Actual source code: snes.c

  1: #include <petsc/private/snesimpl.h>
  2: #include <petscdmshell.h>
  3: #include <petscdraw.h>
  4: #include <petscds.h>
  5: #include <petscdmadaptor.h>
  6: #include <petscconvest.h>

  8: PetscBool         SNESRegisterAllCalled = PETSC_FALSE;
  9: PetscFunctionList SNESList              = NULL;

 11: /* Logging support */
 12: PetscClassId  SNES_CLASSID, DMSNES_CLASSID;
 13: PetscLogEvent SNES_Solve, SNES_SetUp, SNES_FunctionEval, SNES_JacobianEval, SNES_NGSEval, SNES_NGSFuncEval, SNES_NewtonALEval, SNES_NPCSolve, SNES_ObjectiveEval;

 15: /*@
 16:   SNESSetErrorIfNotConverged - Causes `SNESSolve()` to generate an error immediately if the solver has not converged.

 18:   Logically Collective

 20:   Input Parameters:
 21: + snes - iterative context obtained from `SNESCreate()`
 22: - flg  - `PETSC_TRUE` indicates you want the error generated

 24:   Options Database Key:
 25: . -snes_error_if_not_converged <true,false> - cause an immediate error condition and stop the program if the solver does not converge

 27:   Level: intermediate

 29:   Note:
 30:   Normally PETSc continues if a solver fails to converge, you can call `SNESGetConvergedReason()` after a `SNESSolve()`
 31:   to determine if it has converged. Otherwise the solution may be inaccurate or wrong

 33: .seealso: [](ch_snes), `SNES`, `SNESGetErrorIfNotConverged()`, `KSPGetErrorIfNotConverged()`, `KSPSetErrorIfNotConverged()`
 34: @*/
 35: PetscErrorCode SNESSetErrorIfNotConverged(SNES snes, PetscBool flg)
 36: {
 37:   PetscFunctionBegin;
 40:   snes->errorifnotconverged = flg;
 41:   PetscFunctionReturn(PETSC_SUCCESS);
 42: }

 44: /*@
 45:   SNESGetErrorIfNotConverged - Indicates if `SNESSolve()` will generate an error if the solver does not converge?

 47:   Not Collective

 49:   Input Parameter:
 50: . snes - iterative context obtained from `SNESCreate()`

 52:   Output Parameter:
 53: . flag - `PETSC_TRUE` if it will generate an error, else `PETSC_FALSE`

 55:   Level: intermediate

 57: .seealso: [](ch_snes), `SNES`, `SNESSolve()`, `SNESSetErrorIfNotConverged()`, `KSPGetErrorIfNotConverged()`, `KSPSetErrorIfNotConverged()`
 58: @*/
 59: PetscErrorCode SNESGetErrorIfNotConverged(SNES snes, PetscBool *flag)
 60: {
 61:   PetscFunctionBegin;
 63:   PetscAssertPointer(flag, 2);
 64:   *flag = snes->errorifnotconverged;
 65:   PetscFunctionReturn(PETSC_SUCCESS);
 66: }

 68: /*@
 69:   SNESSetAlwaysComputesFinalResidual - tells the `SNES` to always compute the residual (nonlinear function value) at the final solution

 71:   Logically Collective

 73:   Input Parameters:
 74: + snes - the shell `SNES`
 75: - flg  - `PETSC_TRUE` to always compute the residual

 77:   Level: advanced

 79:   Note:
 80:   Some solvers (such as smoothers in a `SNESFAS`) do not need the residual computed at the final solution so skip computing it
 81:   to save time.

 83: .seealso: [](ch_snes), `SNES`, `SNESFAS`, `SNESSolve()`, `SNESGetAlwaysComputesFinalResidual()`
 84: @*/
 85: PetscErrorCode SNESSetAlwaysComputesFinalResidual(SNES snes, PetscBool flg)
 86: {
 87:   PetscFunctionBegin;
 89:   snes->alwayscomputesfinalresidual = flg;
 90:   PetscFunctionReturn(PETSC_SUCCESS);
 91: }

 93: /*@
 94:   SNESGetAlwaysComputesFinalResidual - checks if the `SNES` always computes the residual at the final solution

 96:   Logically Collective

 98:   Input Parameter:
 99: . snes - the `SNES` context

101:   Output Parameter:
102: . flg - `PETSC_TRUE` if the residual is computed

104:   Level: advanced

106: .seealso: [](ch_snes), `SNES`, `SNESFAS`, `SNESSolve()`, `SNESSetAlwaysComputesFinalResidual()`
107: @*/
108: PetscErrorCode SNESGetAlwaysComputesFinalResidual(SNES snes, PetscBool *flg)
109: {
110:   PetscFunctionBegin;
112:   *flg = snes->alwayscomputesfinalresidual;
113:   PetscFunctionReturn(PETSC_SUCCESS);
114: }

116: /*@
117:   SNESSetFunctionDomainError - tells `SNES` that the input vector, a proposed new solution, to your function you provided to `SNESSetFunction()` is not
118:   in the functions domain. For example, a step with negative pressure.

120:   Not Collective

122:   Input Parameter:
123: . snes - the `SNES` context

125:   Level: advanced

127:   Notes:
128:   This does not need to be called by all processes in the `SNES` MPI communicator.

130:   If this is called the `SNESSolve()` stops iterating and returns with a `SNESConvergedReason` of `SNES_DIVERGED_FUNCTION_DOMAIN`

132:   You should always call `SNESGetConvergedReason()` after each `SNESSolve()` and verify if the iteration converged (positive result) or diverged (negative result).

134:   You can direct `SNES` to avoid certain steps by using `SNESVISetVariableBounds()`, `SNESVISetComputeVariableBounds()` or
135:   `SNESLineSearchSetPreCheck()`, `SNESLineSearchSetPostCheck()`

137:   You can call `SNESSetJacobianDomainError()` during a Jacobian computation to indicate the proposed solution is not in the domain.

139:   Developer Note:
140:   This value is used by `SNESCheckFunctionNorm()` to determine if the `SNESConvergedReason` is set to `SNES_DIVERGED_FUNCTION_DOMAIN`

142: .seealso: [](ch_snes), `SNESCreate()`, `SNESSetFunction()`, `SNESFunctionFn`, `SNESSetJacobianDomainError()`, `SNESVISetVariableBounds()`,
143:           `SNESVISetComputeVariableBounds()`, `SNESLineSearchSetPreCheck()`, `SNESLineSearchSetPostCheck()`, `SNESConvergedReason`, `SNESGetConvergedReason()`,
144:           `SNES_DIVERGED_FUNCTION_DOMAIN`
145: @*/
146: PetscErrorCode SNESSetFunctionDomainError(SNES snes)
147: {
148:   PetscFunctionBegin;
150:   PetscCheck(!snes->errorifnotconverged, PETSC_COMM_SELF, PETSC_ERR_ARG_OUTOFRANGE, "User code indicates input vector is not in the function domain");
151:   snes->domainerror = PETSC_TRUE;
152:   PetscFunctionReturn(PETSC_SUCCESS);
153: }

155: /*@
156:   SNESSetJacobianDomainError - tells `SNES` that the function you provided to `SNESSetJacobian()` at the proposed step. For example there is a negative element transformation.

158:   Logically Collective

160:   Input Parameter:
161: . snes - the `SNES` context

163:   Level: advanced

165:   Notes:
166:   If this is called the `SNESSolve()` stops iterating and returns with a `SNESConvergedReason` of `SNES_DIVERGED_FUNCTION_DOMAIN`

168:   You should always call `SNESGetConvergedReason()` after each `SNESSolve()` and verify if the iteration converged (positive result) or diverged (negative result).

170:   You can direct `SNES` to avoid certain steps by using `SNESVISetVariableBounds()`, `SNESVISetComputeVariableBounds()` or
171:   `SNESLineSearchSetPreCheck()`, `SNESLineSearchSetPostCheck()`

173: .seealso: [](ch_snes), `SNESCreate()`, `SNESSetFunction()`, `SNESFunctionFn`, `SNESSetFunctionDomainError()`, `SNESVISetVariableBounds()`,
174:           `SNESVISetComputeVariableBounds()`, `SNESLineSearchSetPreCheck()`, `SNESLineSearchSetPostCheck()`, `SNESConvergedReason`, `SNESGetConvergedReason()`
175: @*/
176: PetscErrorCode SNESSetJacobianDomainError(SNES snes)
177: {
178:   PetscFunctionBegin;
180:   PetscCheck(!snes->errorifnotconverged, PETSC_COMM_SELF, PETSC_ERR_ARG_OUTOFRANGE, "User code indicates computeJacobian does not make sense");
181:   snes->jacobiandomainerror = PETSC_TRUE;
182:   PetscFunctionReturn(PETSC_SUCCESS);
183: }

185: /*@
186:   SNESSetCheckJacobianDomainError - tells `SNESSolve()` whether to check if the user called `SNESSetJacobianDomainError()` Jacobian domain error after
187:   each Jacobian evaluation. By default, it checks for the Jacobian domain error in the debug mode, and does not check it in the optimized mode.

189:   Logically Collective

191:   Input Parameters:
192: + snes - the `SNES` context
193: - flg  - indicates if or not to check Jacobian domain error after each Jacobian evaluation

195:   Level: advanced

197:   Note:
198:   Checks require one extra parallel synchronization for each Jacobian evaluation

200: .seealso: [](ch_snes), `SNES`, `SNESConvergedReason`, `SNESCreate()`, `SNESSetFunction()`, `SNESFunctionFn`, `SNESSetFunctionDomainError()`, `SNESGetCheckJacobianDomainError()`
201: @*/
202: PetscErrorCode SNESSetCheckJacobianDomainError(SNES snes, PetscBool flg)
203: {
204:   PetscFunctionBegin;
206:   snes->checkjacdomainerror = flg;
207:   PetscFunctionReturn(PETSC_SUCCESS);
208: }

210: /*@
211:   SNESGetCheckJacobianDomainError - Get an indicator whether or not `SNES` is checking Jacobian domain errors after each Jacobian evaluation.

213:   Logically Collective

215:   Input Parameter:
216: . snes - the `SNES` context

218:   Output Parameter:
219: . flg - `PETSC_FALSE` indicates that it is not checking Jacobian domain errors after each Jacobian evaluation

221:   Level: advanced

223: .seealso: [](ch_snes), `SNES`, `SNESCreate()`, `SNESSetFunction()`, `SNESFunctionFn`, `SNESSetFunctionDomainError()`, `SNESSetCheckJacobianDomainError()`
224: @*/
225: PetscErrorCode SNESGetCheckJacobianDomainError(SNES snes, PetscBool *flg)
226: {
227:   PetscFunctionBegin;
229:   PetscAssertPointer(flg, 2);
230:   *flg = snes->checkjacdomainerror;
231:   PetscFunctionReturn(PETSC_SUCCESS);
232: }

234: /*@
235:   SNESGetFunctionDomainError - Gets the status of the domain error after a call to `SNESComputeFunction()`

237:   Not Collective, different MPI processes may return different values

239:   Input Parameter:
240: . snes - the `SNES` context

242:   Output Parameter:
243: . domainerror - Set to `PETSC_TRUE` if there's a domain error; `PETSC_FALSE` otherwise.

245:   Level: developer

247:   Notes:
248:   The value will only be true on those MPI processes that called `SNESSetFunctionDomainError()`

250:   The value is reset to `PETSC_FALSE` when `SNESCheckFunctionNorm()` is called.

252: .seealso: [](ch_snes), `SNES`, `SNESSetFunctionDomainError()`, `SNESComputeFunction()`
253: @*/
254: PetscErrorCode SNESGetFunctionDomainError(SNES snes, PetscBool *domainerror)
255: {
256:   PetscFunctionBegin;
258:   PetscAssertPointer(domainerror, 2);
259:   *domainerror = snes->domainerror;
260:   PetscFunctionReturn(PETSC_SUCCESS);
261: }

263: /*@
264:   SNESGetJacobianDomainError - Gets the status of the Jacobian domain error after a call to `SNESComputeJacobian()`

266:   Not Collective, different MPI processes may return different values

268:   Input Parameter:
269: . snes - the `SNES` context

271:   Output Parameter:
272: . domainerror - Set to `PETSC_TRUE` if there's a Jacobian domain error; `PETSC_FALSE` otherwise.

274:   Level: advanced

276:   Notes:
277:   The value will only be true on those MPI processes that called `SNESSetJacobianDomainError()`

279:   The value is reset to `PETSC_FALSE` when `SNESCheckJacobianDomainerror()` is called but only `SNESSetCheckJacobianDomainError()` was called

281: .seealso: [](ch_snes), `SNES`, `SNESSetFunctionDomainError()`, `SNESComputeFunction()`, `SNESGetFunctionDomainError()`
282: @*/
283: PetscErrorCode SNESGetJacobianDomainError(SNES snes, PetscBool *domainerror)
284: {
285:   PetscFunctionBegin;
287:   PetscAssertPointer(domainerror, 2);
288:   *domainerror = snes->jacobiandomainerror;
289:   PetscFunctionReturn(PETSC_SUCCESS);
290: }

292: /*@
293:   SNESLoad - Loads a `SNES` that has been stored in `PETSCVIEWERBINARY` with `SNESView()`.

295:   Collective

297:   Input Parameters:
298: + snes   - the newly loaded `SNES`, this needs to have been created with `SNESCreate()` or
299:            some related function before a call to `SNESLoad()`.
300: - viewer - binary file viewer, obtained from `PetscViewerBinaryOpen()`

302:   Level: intermediate

304:   Note:
305:   The `SNESType` is determined by the data in the file, any type set into the `SNES` before this call is ignored.

307: .seealso: [](ch_snes), `SNES`, `PetscViewer`, `SNESCreate()`, `SNESType`, `PetscViewerBinaryOpen()`, `SNESView()`, `MatLoad()`, `VecLoad()`
308: @*/
309: PetscErrorCode SNESLoad(SNES snes, PetscViewer viewer)
310: {
311:   PetscBool isbinary;
312:   PetscInt  classid;
313:   char      type[256];
314:   KSP       ksp;
315:   DM        dm;
316:   DMSNES    dmsnes;

318:   PetscFunctionBegin;
321:   PetscCall(PetscObjectTypeCompare((PetscObject)viewer, PETSCVIEWERBINARY, &isbinary));
322:   PetscCheck(isbinary, PETSC_COMM_SELF, PETSC_ERR_ARG_WRONG, "Invalid viewer; open viewer with PetscViewerBinaryOpen()");

324:   PetscCall(PetscViewerBinaryRead(viewer, &classid, 1, NULL, PETSC_INT));
325:   PetscCheck(classid == SNES_FILE_CLASSID, PetscObjectComm((PetscObject)snes), PETSC_ERR_ARG_WRONG, "Not SNES next in file");
326:   PetscCall(PetscViewerBinaryRead(viewer, type, 256, NULL, PETSC_CHAR));
327:   PetscCall(SNESSetType(snes, type));
328:   PetscTryTypeMethod(snes, load, viewer);
329:   PetscCall(SNESGetDM(snes, &dm));
330:   PetscCall(DMGetDMSNES(dm, &dmsnes));
331:   PetscCall(DMSNESLoad(dmsnes, viewer));
332:   PetscCall(SNESGetKSP(snes, &ksp));
333:   PetscCall(KSPLoad(ksp, viewer));
334:   PetscFunctionReturn(PETSC_SUCCESS);
335: }

337: #include <petscdraw.h>
338: #if defined(PETSC_HAVE_SAWS)
339: #include <petscviewersaws.h>
340: #endif

342: /*@
343:   SNESViewFromOptions - View a `SNES` based on values in the options database

345:   Collective

347:   Input Parameters:
348: + A    - the `SNES` context
349: . obj  - Optional object that provides the options prefix for the checks
350: - name - command line option

352:   Level: intermediate

354: .seealso: [](ch_snes), `SNES`, `SNESView`, `PetscObjectViewFromOptions()`, `SNESCreate()`
355: @*/
356: PetscErrorCode SNESViewFromOptions(SNES A, PetscObject obj, const char name[])
357: {
358:   PetscFunctionBegin;
360:   PetscCall(PetscObjectViewFromOptions((PetscObject)A, obj, name));
361:   PetscFunctionReturn(PETSC_SUCCESS);
362: }

364: PETSC_EXTERN PetscErrorCode SNESComputeJacobian_DMDA(SNES, Vec, Mat, Mat, void *);

366: /*@
367:   SNESView - Prints or visualizes the `SNES` data structure.

369:   Collective

371:   Input Parameters:
372: + snes   - the `SNES` context
373: - viewer - the `PetscViewer`

375:   Options Database Key:
376: . -snes_view - Calls `SNESView()` at end of `SNESSolve()`

378:   Level: beginner

380:   Notes:
381:   The available visualization contexts include
382: +     `PETSC_VIEWER_STDOUT_SELF` - standard output (default)
383: -     `PETSC_VIEWER_STDOUT_WORLD` - synchronized standard
384:   output where only the first processor opens
385:   the file.  All other processors send their
386:   data to the first processor to print.

388:   The available formats include
389: +     `PETSC_VIEWER_DEFAULT` - standard output (default)
390: -     `PETSC_VIEWER_ASCII_INFO_DETAIL` - more verbose output for `SNESNASM`

392:   The user can open an alternative visualization context with
393:   `PetscViewerASCIIOpen()` - output to a specified file.

395:   In the debugger you can do "call `SNESView`(snes,0)" to display the `SNES` solver. (The same holds for any PETSc object viewer).

397: .seealso: [](ch_snes), `SNES`, `SNESLoad()`, `SNESCreate()`, `PetscViewerASCIIOpen()`
398: @*/
399: PetscErrorCode SNESView(SNES snes, PetscViewer viewer)
400: {
401:   SNESKSPEW     *kctx;
402:   KSP            ksp;
403:   SNESLineSearch linesearch;
404:   PetscBool      isascii, isstring, isbinary, isdraw;
405:   DMSNES         dmsnes;
406: #if defined(PETSC_HAVE_SAWS)
407:   PetscBool issaws;
408: #endif

410:   PetscFunctionBegin;
412:   if (!viewer) PetscCall(PetscViewerASCIIGetStdout(PetscObjectComm((PetscObject)snes), &viewer));
414:   PetscCheckSameComm(snes, 1, viewer, 2);

416:   PetscCall(PetscObjectTypeCompare((PetscObject)viewer, PETSCVIEWERASCII, &isascii));
417:   PetscCall(PetscObjectTypeCompare((PetscObject)viewer, PETSCVIEWERSTRING, &isstring));
418:   PetscCall(PetscObjectTypeCompare((PetscObject)viewer, PETSCVIEWERBINARY, &isbinary));
419:   PetscCall(PetscObjectTypeCompare((PetscObject)viewer, PETSCVIEWERDRAW, &isdraw));
420: #if defined(PETSC_HAVE_SAWS)
421:   PetscCall(PetscObjectTypeCompare((PetscObject)viewer, PETSCVIEWERSAWS, &issaws));
422: #endif
423:   if (isascii) {
424:     SNESNormSchedule normschedule;
425:     DM               dm;
426:     SNESJacobianFn  *cJ;
427:     void            *ctx;
428:     const char      *pre = "";

430:     PetscCall(PetscObjectPrintClassNamePrefixType((PetscObject)snes, viewer));
431:     if (!snes->setupcalled) PetscCall(PetscViewerASCIIPrintf(viewer, "  SNES has not been set up so information may be incomplete\n"));
432:     if (snes->ops->view) {
433:       PetscCall(PetscViewerASCIIPushTab(viewer));
434:       PetscUseTypeMethod(snes, view, viewer);
435:       PetscCall(PetscViewerASCIIPopTab(viewer));
436:     }
437:     if (snes->max_funcs == PETSC_UNLIMITED) {
438:       PetscCall(PetscViewerASCIIPrintf(viewer, "  maximum iterations=%" PetscInt_FMT ", maximum function evaluations=unlimited\n", snes->max_its));
439:     } else {
440:       PetscCall(PetscViewerASCIIPrintf(viewer, "  maximum iterations=%" PetscInt_FMT ", maximum function evaluations=%" PetscInt_FMT "\n", snes->max_its, snes->max_funcs));
441:     }
442:     PetscCall(PetscViewerASCIIPrintf(viewer, "  tolerances: relative=%g, absolute=%g, solution=%g\n", (double)snes->rtol, (double)snes->abstol, (double)snes->stol));
443:     if (snes->usesksp) PetscCall(PetscViewerASCIIPrintf(viewer, "  total number of linear solver iterations=%" PetscInt_FMT "\n", snes->linear_its));
444:     PetscCall(PetscViewerASCIIPrintf(viewer, "  total number of function evaluations=%" PetscInt_FMT "\n", snes->nfuncs));
445:     PetscCall(SNESGetNormSchedule(snes, &normschedule));
446:     if (normschedule > 0) PetscCall(PetscViewerASCIIPrintf(viewer, "  norm schedule %s\n", SNESNormSchedules[normschedule]));
447:     if (snes->gridsequence) PetscCall(PetscViewerASCIIPrintf(viewer, "  total number of grid sequence refinements=%" PetscInt_FMT "\n", snes->gridsequence));
448:     if (snes->ksp_ewconv) {
449:       kctx = (SNESKSPEW *)snes->kspconvctx;
450:       if (kctx) {
451:         PetscCall(PetscViewerASCIIPrintf(viewer, "  Eisenstat-Walker computation of KSP relative tolerance (version %" PetscInt_FMT ")\n", kctx->version));
452:         PetscCall(PetscViewerASCIIPrintf(viewer, "    rtol_0=%g, rtol_max=%g, threshold=%g\n", (double)kctx->rtol_0, (double)kctx->rtol_max, (double)kctx->threshold));
453:         PetscCall(PetscViewerASCIIPrintf(viewer, "    gamma=%g, alpha=%g, alpha2=%g\n", (double)kctx->gamma, (double)kctx->alpha, (double)kctx->alpha2));
454:       }
455:     }
456:     if (snes->lagpreconditioner == -1) {
457:       PetscCall(PetscViewerASCIIPrintf(viewer, "  Preconditioned is never rebuilt\n"));
458:     } else if (snes->lagpreconditioner > 1) {
459:       PetscCall(PetscViewerASCIIPrintf(viewer, "  Preconditioned is rebuilt every %" PetscInt_FMT " new Jacobians\n", snes->lagpreconditioner));
460:     }
461:     if (snes->lagjacobian == -1) {
462:       PetscCall(PetscViewerASCIIPrintf(viewer, "  Jacobian is never rebuilt\n"));
463:     } else if (snes->lagjacobian > 1) {
464:       PetscCall(PetscViewerASCIIPrintf(viewer, "  Jacobian is rebuilt every %" PetscInt_FMT " SNES iterations\n", snes->lagjacobian));
465:     }
466:     PetscCall(SNESGetDM(snes, &dm));
467:     PetscCall(DMSNESGetJacobian(dm, &cJ, &ctx));
468:     if (snes->mf_operator) {
469:       PetscCall(PetscViewerASCIIPrintf(viewer, "  Jacobian is applied matrix-free with differencing\n"));
470:       pre = "Preconditioning ";
471:     }
472:     if (cJ == SNESComputeJacobianDefault) {
473:       PetscCall(PetscViewerASCIIPrintf(viewer, "  %sJacobian is built using finite differences one column at a time\n", pre));
474:     } else if (cJ == SNESComputeJacobianDefaultColor) {
475:       PetscCall(PetscViewerASCIIPrintf(viewer, "  %sJacobian is built using finite differences with coloring\n", pre));
476:       /* it slightly breaks data encapsulation for access the DMDA information directly */
477:     } else if (cJ == SNESComputeJacobian_DMDA) {
478:       MatFDColoring fdcoloring;
479:       PetscCall(PetscObjectQuery((PetscObject)dm, "DMDASNES_FDCOLORING", (PetscObject *)&fdcoloring));
480:       if (fdcoloring) {
481:         PetscCall(PetscViewerASCIIPrintf(viewer, "  %sJacobian is built using colored finite differences on a DMDA\n", pre));
482:       } else {
483:         PetscCall(PetscViewerASCIIPrintf(viewer, "  %sJacobian is built using a DMDA local Jacobian\n", pre));
484:       }
485:     } else if (snes->mf && !snes->mf_operator) {
486:       PetscCall(PetscViewerASCIIPrintf(viewer, "  Jacobian is applied matrix-free with differencing, no explicit Jacobian\n"));
487:     }
488:   } else if (isstring) {
489:     const char *type;
490:     PetscCall(SNESGetType(snes, &type));
491:     PetscCall(PetscViewerStringSPrintf(viewer, " SNESType: %-7.7s", type));
492:     PetscTryTypeMethod(snes, view, viewer);
493:   } else if (isbinary) {
494:     PetscInt    classid = SNES_FILE_CLASSID;
495:     MPI_Comm    comm;
496:     PetscMPIInt rank;
497:     char        type[256];

499:     PetscCall(PetscObjectGetComm((PetscObject)snes, &comm));
500:     PetscCallMPI(MPI_Comm_rank(comm, &rank));
501:     if (rank == 0) {
502:       PetscCall(PetscViewerBinaryWrite(viewer, &classid, 1, PETSC_INT));
503:       PetscCall(PetscStrncpy(type, ((PetscObject)snes)->type_name, sizeof(type)));
504:       PetscCall(PetscViewerBinaryWrite(viewer, type, sizeof(type), PETSC_CHAR));
505:     }
506:     PetscTryTypeMethod(snes, view, viewer);
507:   } else if (isdraw) {
508:     PetscDraw draw;
509:     char      str[36];
510:     PetscReal x, y, bottom, h;

512:     PetscCall(PetscViewerDrawGetDraw(viewer, 0, &draw));
513:     PetscCall(PetscDrawGetCurrentPoint(draw, &x, &y));
514:     PetscCall(PetscStrncpy(str, "SNES: ", sizeof(str)));
515:     PetscCall(PetscStrlcat(str, ((PetscObject)snes)->type_name, sizeof(str)));
516:     PetscCall(PetscDrawStringBoxed(draw, x, y, PETSC_DRAW_BLUE, PETSC_DRAW_BLACK, str, NULL, &h));
517:     bottom = y - h;
518:     PetscCall(PetscDrawPushCurrentPoint(draw, x, bottom));
519:     PetscTryTypeMethod(snes, view, viewer);
520: #if defined(PETSC_HAVE_SAWS)
521:   } else if (issaws) {
522:     PetscMPIInt rank;
523:     const char *name;

525:     PetscCall(PetscObjectGetName((PetscObject)snes, &name));
526:     PetscCallMPI(MPI_Comm_rank(PETSC_COMM_WORLD, &rank));
527:     if (!((PetscObject)snes)->amsmem && rank == 0) {
528:       char dir[1024];

530:       PetscCall(PetscObjectViewSAWs((PetscObject)snes, viewer));
531:       PetscCall(PetscSNPrintf(dir, 1024, "/PETSc/Objects/%s/its", name));
532:       PetscCallSAWs(SAWs_Register, (dir, &snes->iter, 1, SAWs_READ, SAWs_INT));
533:       if (!snes->conv_hist) PetscCall(SNESSetConvergenceHistory(snes, NULL, NULL, PETSC_DECIDE, PETSC_TRUE));
534:       PetscCall(PetscSNPrintf(dir, 1024, "/PETSc/Objects/%s/conv_hist", name));
535:       PetscCallSAWs(SAWs_Register, (dir, snes->conv_hist, 10, SAWs_READ, SAWs_DOUBLE));
536:     }
537: #endif
538:   }
539:   if (snes->linesearch) {
540:     PetscCall(SNESGetLineSearch(snes, &linesearch));
541:     PetscCall(PetscViewerASCIIPushTab(viewer));
542:     PetscCall(SNESLineSearchView(linesearch, viewer));
543:     PetscCall(PetscViewerASCIIPopTab(viewer));
544:   }
545:   if (snes->npc && snes->usesnpc) {
546:     PetscCall(PetscViewerASCIIPushTab(viewer));
547:     PetscCall(SNESView(snes->npc, viewer));
548:     PetscCall(PetscViewerASCIIPopTab(viewer));
549:   }
550:   PetscCall(PetscViewerASCIIPushTab(viewer));
551:   PetscCall(DMGetDMSNES(snes->dm, &dmsnes));
552:   PetscCall(DMSNESView(dmsnes, viewer));
553:   PetscCall(PetscViewerASCIIPopTab(viewer));
554:   if (snes->usesksp) {
555:     PetscCall(SNESGetKSP(snes, &ksp));
556:     PetscCall(PetscViewerASCIIPushTab(viewer));
557:     PetscCall(KSPView(ksp, viewer));
558:     PetscCall(PetscViewerASCIIPopTab(viewer));
559:   }
560:   if (isdraw) {
561:     PetscDraw draw;
562:     PetscCall(PetscViewerDrawGetDraw(viewer, 0, &draw));
563:     PetscCall(PetscDrawPopCurrentPoint(draw));
564:   }
565:   PetscFunctionReturn(PETSC_SUCCESS);
566: }

568: /*
569:   We retain a list of functions that also take SNES command
570:   line options. These are called at the end SNESSetFromOptions()
571: */
572: #define MAXSETFROMOPTIONS 5
573: static PetscInt numberofsetfromoptions;
574: static PetscErrorCode (*othersetfromoptions[MAXSETFROMOPTIONS])(SNES);

576: /*@C
577:   SNESAddOptionsChecker - Adds an additional function to check for `SNES` options.

579:   Not Collective

581:   Input Parameter:
582: . snescheck - function that checks for options

584:   Calling sequence of `snescheck`:
585: . snes - the `SNES` object for which it is checking options

587:   Level: developer

589: .seealso: [](ch_snes), `SNES`, `SNESSetFromOptions()`
590: @*/
591: PetscErrorCode SNESAddOptionsChecker(PetscErrorCode (*snescheck)(SNES snes))
592: {
593:   PetscFunctionBegin;
594:   PetscCheck(numberofsetfromoptions < MAXSETFROMOPTIONS, PETSC_COMM_SELF, PETSC_ERR_ARG_OUTOFRANGE, "Too many options checkers, only %d allowed", MAXSETFROMOPTIONS);
595:   othersetfromoptions[numberofsetfromoptions++] = snescheck;
596:   PetscFunctionReturn(PETSC_SUCCESS);
597: }

599: static PetscErrorCode SNESSetUpMatrixFree_Private(SNES snes, PetscBool hasOperator, PetscInt version)
600: {
601:   Mat          J;
602:   MatNullSpace nullsp;

604:   PetscFunctionBegin;

607:   if (!snes->vec_func && (snes->jacobian || snes->jacobian_pre)) {
608:     Mat A = snes->jacobian, B = snes->jacobian_pre;
609:     PetscCall(MatCreateVecs(A ? A : B, NULL, &snes->vec_func));
610:   }

612:   PetscCheck(version == 1 || version == 2, PETSC_COMM_SELF, PETSC_ERR_ARG_OUTOFRANGE, "matrix-free operator routines, only version 1 and 2");
613:   if (version == 1) {
614:     PetscCall(MatCreateSNESMF(snes, &J));
615:     PetscCall(MatMFFDSetOptionsPrefix(J, ((PetscObject)snes)->prefix));
616:     PetscCall(MatSetFromOptions(J));
617:     /* TODO: the version 2 code should be merged into the MatCreateSNESMF() and MatCreateMFFD() infrastructure and then removed */
618:   } else /* if (version == 2) */ {
619:     PetscCheck(snes->vec_func, PETSC_COMM_SELF, PETSC_ERR_ARG_WRONGSTATE, "SNESSetFunction() must be called first");
620: #if !defined(PETSC_USE_COMPLEX) && !defined(PETSC_USE_REAL_SINGLE) && !defined(PETSC_USE_REAL___FLOAT128) && !defined(PETSC_USE_REAL___FP16)
621:     PetscCall(MatCreateSNESMFMore(snes, snes->vec_func, &J));
622: #else
623:     SETERRQ(PETSC_COMM_SELF, PETSC_ERR_SUP, "matrix-free operator routines (version 2)");
624: #endif
625:   }

627:   /* attach any user provided null space that was on Amat to the newly created matrix-free matrix */
628:   if (snes->jacobian) {
629:     PetscCall(MatGetNullSpace(snes->jacobian, &nullsp));
630:     if (nullsp) PetscCall(MatSetNullSpace(J, nullsp));
631:   }

633:   PetscCall(PetscInfo(snes, "Setting default matrix-free operator routines (version %" PetscInt_FMT ")\n", version));
634:   if (hasOperator) {
635:     /* This version replaces the user provided Jacobian matrix with a
636:        matrix-free version but still employs the user-provided matrix used for computing the preconditioner. */
637:     PetscCall(SNESSetJacobian(snes, J, NULL, NULL, NULL));
638:   } else {
639:     /* This version replaces both the user-provided Jacobian and the user-
640:      provided preconditioner Jacobian with the default matrix-free version. */
641:     if (snes->npcside == PC_LEFT && snes->npc) {
642:       if (!snes->jacobian) PetscCall(SNESSetJacobian(snes, J, NULL, NULL, NULL));
643:     } else {
644:       KSP       ksp;
645:       PC        pc;
646:       PetscBool match;

648:       PetscCall(SNESSetJacobian(snes, J, J, MatMFFDComputeJacobian, NULL));
649:       /* Force no preconditioner */
650:       PetscCall(SNESGetKSP(snes, &ksp));
651:       PetscCall(KSPGetPC(ksp, &pc));
652:       PetscCall(PetscObjectTypeCompareAny((PetscObject)pc, &match, PCSHELL, PCH2OPUS, ""));
653:       if (!match) {
654:         PetscCall(PetscInfo(snes, "Setting default matrix-free preconditioner routines\nThat is no preconditioner is being used\n"));
655:         PetscCall(PCSetType(pc, PCNONE));
656:       }
657:     }
658:   }
659:   PetscCall(MatDestroy(&J));
660:   PetscFunctionReturn(PETSC_SUCCESS);
661: }

663: static PetscErrorCode DMRestrictHook_SNESVecSol(DM dmfine, Mat Restrict, Vec Rscale, Mat Inject, DM dmcoarse, void *ctx)
664: {
665:   SNES snes = (SNES)ctx;
666:   Vec  Xfine, Xfine_named = NULL, Xcoarse;

668:   PetscFunctionBegin;
669:   if (PetscLogPrintInfo) {
670:     PetscInt finelevel, coarselevel, fineclevel, coarseclevel;
671:     PetscCall(DMGetRefineLevel(dmfine, &finelevel));
672:     PetscCall(DMGetCoarsenLevel(dmfine, &fineclevel));
673:     PetscCall(DMGetRefineLevel(dmcoarse, &coarselevel));
674:     PetscCall(DMGetCoarsenLevel(dmcoarse, &coarseclevel));
675:     PetscCall(PetscInfo(dmfine, "Restricting SNES solution vector from level %" PetscInt_FMT "-%" PetscInt_FMT " to level %" PetscInt_FMT "-%" PetscInt_FMT "\n", finelevel, fineclevel, coarselevel, coarseclevel));
676:   }
677:   if (dmfine == snes->dm) Xfine = snes->vec_sol;
678:   else {
679:     PetscCall(DMGetNamedGlobalVector(dmfine, "SNESVecSol", &Xfine_named));
680:     Xfine = Xfine_named;
681:   }
682:   PetscCall(DMGetNamedGlobalVector(dmcoarse, "SNESVecSol", &Xcoarse));
683:   if (Inject) {
684:     PetscCall(MatRestrict(Inject, Xfine, Xcoarse));
685:   } else {
686:     PetscCall(MatRestrict(Restrict, Xfine, Xcoarse));
687:     PetscCall(VecPointwiseMult(Xcoarse, Xcoarse, Rscale));
688:   }
689:   PetscCall(DMRestoreNamedGlobalVector(dmcoarse, "SNESVecSol", &Xcoarse));
690:   if (Xfine_named) PetscCall(DMRestoreNamedGlobalVector(dmfine, "SNESVecSol", &Xfine_named));
691:   PetscFunctionReturn(PETSC_SUCCESS);
692: }

694: static PetscErrorCode DMCoarsenHook_SNESVecSol(DM dm, DM dmc, void *ctx)
695: {
696:   PetscFunctionBegin;
697:   PetscCall(DMCoarsenHookAdd(dmc, DMCoarsenHook_SNESVecSol, DMRestrictHook_SNESVecSol, ctx));
698:   PetscFunctionReturn(PETSC_SUCCESS);
699: }

701: /* This may be called to rediscretize the operator on levels of linear multigrid. The DM shuffle is so the user can
702:  * safely call SNESGetDM() in their residual evaluation routine. */
703: static PetscErrorCode KSPComputeOperators_SNES(KSP ksp, Mat A, Mat B, void *ctx)
704: {
705:   SNES            snes = (SNES)ctx;
706:   DMSNES          sdm;
707:   Vec             X, Xnamed = NULL;
708:   DM              dmsave;
709:   void           *ctxsave;
710:   SNESJacobianFn *jac = NULL;

712:   PetscFunctionBegin;
713:   dmsave = snes->dm;
714:   PetscCall(KSPGetDM(ksp, &snes->dm));
715:   if (dmsave == snes->dm) X = snes->vec_sol; /* We are on the finest level */
716:   else {
717:     PetscBool has;

719:     /* We are on a coarser level, this vec was initialized using a DM restrict hook */
720:     PetscCall(DMHasNamedGlobalVector(snes->dm, "SNESVecSol", &has));
721:     PetscCheck(has, PetscObjectComm((PetscObject)snes->dm), PETSC_ERR_PLIB, "Missing SNESVecSol");
722:     PetscCall(DMGetNamedGlobalVector(snes->dm, "SNESVecSol", &Xnamed));
723:     X = Xnamed;
724:     PetscCall(SNESGetJacobian(snes, NULL, NULL, &jac, &ctxsave));
725:     /* If the DM's don't match up, the MatFDColoring context needed for the jacobian won't match up either -- fixit. */
726:     if (jac == SNESComputeJacobianDefaultColor) PetscCall(SNESSetJacobian(snes, NULL, NULL, SNESComputeJacobianDefaultColor, NULL));
727:   }

729:   /* Compute the operators */
730:   PetscCall(DMGetDMSNES(snes->dm, &sdm));
731:   if (Xnamed && sdm->ops->computefunction) {
732:     /* The SNES contract with the user is that ComputeFunction is always called before ComputeJacobian.
733:        We make sure of this here. Disable affine shift since it is for the finest level */
734:     Vec F, saverhs = snes->vec_rhs;

736:     snes->vec_rhs = NULL;
737:     PetscCall(DMGetGlobalVector(snes->dm, &F));
738:     PetscCall(SNESComputeFunction(snes, X, F));
739:     PetscCall(DMRestoreGlobalVector(snes->dm, &F));
740:     snes->vec_rhs = saverhs;
741:     snes->nfuncs--; /* Do not log coarser level evaluations */
742:   }
743:   /* Make sure KSP DM has the Jacobian computation routine */
744:   if (!sdm->ops->computejacobian) PetscCall(DMCopyDMSNES(dmsave, snes->dm));
745:   PetscCall(SNESComputeJacobian(snes, X, A, B));

747:   /* Put the previous context back */
748:   if (snes->dm != dmsave && jac == SNESComputeJacobianDefaultColor) PetscCall(SNESSetJacobian(snes, NULL, NULL, jac, ctxsave));

750:   if (Xnamed) PetscCall(DMRestoreNamedGlobalVector(snes->dm, "SNESVecSol", &Xnamed));
751:   snes->dm = dmsave;
752:   PetscFunctionReturn(PETSC_SUCCESS);
753: }

755: /*@
756:   SNESSetUpMatrices - ensures that matrices are available for `SNES` Newton-like methods, this is called by `SNESSetUp_XXX()`

758:   Collective

760:   Input Parameter:
761: . snes - `SNES` object to configure

763:   Level: developer

765:   Note:
766:   If the matrices do not yet exist it attempts to create them based on options previously set for the `SNES` such as `-snes_mf`

768:   Developer Note:
769:   The functionality of this routine overlaps in a confusing way with the functionality of `SNESSetUpMatrixFree_Private()` which is called by
770:   `SNESSetUp()` but sometimes `SNESSetUpMatrices()` is called without `SNESSetUp()` being called. A refactorization to simplify the
771:   logic that handles the matrix-free case is desirable.

773: .seealso: [](ch_snes), `SNES`, `SNESSetUp()`
774: @*/
775: PetscErrorCode SNESSetUpMatrices(SNES snes)
776: {
777:   DM     dm;
778:   DMSNES sdm;

780:   PetscFunctionBegin;
781:   PetscCall(SNESGetDM(snes, &dm));
782:   PetscCall(DMGetDMSNES(dm, &sdm));
783:   if (!snes->jacobian && snes->mf && !snes->mf_operator && !snes->jacobian_pre) {
784:     Mat   J;
785:     void *functx;
786:     PetscCall(MatCreateSNESMF(snes, &J));
787:     PetscCall(MatMFFDSetOptionsPrefix(J, ((PetscObject)snes)->prefix));
788:     PetscCall(MatSetFromOptions(J));
789:     PetscCall(SNESGetFunction(snes, NULL, NULL, &functx));
790:     PetscCall(SNESSetJacobian(snes, J, J, NULL, NULL));
791:     PetscCall(MatDestroy(&J));
792:   } else if (snes->mf_operator && !snes->jacobian_pre && !snes->jacobian) {
793:     Mat J, B;
794:     PetscCall(MatCreateSNESMF(snes, &J));
795:     PetscCall(MatMFFDSetOptionsPrefix(J, ((PetscObject)snes)->prefix));
796:     PetscCall(MatSetFromOptions(J));
797:     PetscCall(DMCreateMatrix(snes->dm, &B));
798:     /* sdm->computejacobian was already set to reach here */
799:     PetscCall(SNESSetJacobian(snes, J, B, NULL, NULL));
800:     PetscCall(MatDestroy(&J));
801:     PetscCall(MatDestroy(&B));
802:   } else if (!snes->jacobian_pre) {
803:     PetscDS   prob;
804:     Mat       J, B;
805:     PetscBool hasPrec = PETSC_FALSE;

807:     J = snes->jacobian;
808:     PetscCall(DMGetDS(dm, &prob));
809:     if (prob) PetscCall(PetscDSHasJacobianPreconditioner(prob, &hasPrec));
810:     if (J) PetscCall(PetscObjectReference((PetscObject)J));
811:     else if (hasPrec) PetscCall(DMCreateMatrix(snes->dm, &J));
812:     PetscCall(DMCreateMatrix(snes->dm, &B));
813:     PetscCall(SNESSetJacobian(snes, J ? J : B, B, NULL, NULL));
814:     PetscCall(MatDestroy(&J));
815:     PetscCall(MatDestroy(&B));
816:   }
817:   {
818:     KSP ksp;
819:     PetscCall(SNESGetKSP(snes, &ksp));
820:     PetscCall(KSPSetComputeOperators(ksp, KSPComputeOperators_SNES, snes));
821:     PetscCall(DMCoarsenHookAdd(snes->dm, DMCoarsenHook_SNESVecSol, DMRestrictHook_SNESVecSol, snes));
822:   }
823:   PetscFunctionReturn(PETSC_SUCCESS);
824: }

826: PETSC_SINGLE_LIBRARY_INTERN PetscErrorCode PetscMonitorPauseFinal_Internal(PetscInt, void *);

828: static PetscErrorCode SNESMonitorPauseFinal_Internal(SNES snes)
829: {
830:   PetscFunctionBegin;
831:   if (!snes->pauseFinal) PetscFunctionReturn(PETSC_SUCCESS);
832:   PetscCall(PetscMonitorPauseFinal_Internal(snes->numbermonitors, snes->monitorcontext));
833:   PetscFunctionReturn(PETSC_SUCCESS);
834: }

836: /*@C
837:   SNESMonitorSetFromOptions - Sets a monitor function and viewer appropriate for the type indicated by the user

839:   Collective

841:   Input Parameters:
842: + snes         - `SNES` object you wish to monitor
843: . name         - the monitor type one is seeking
844: . help         - message indicating what monitoring is done
845: . manual       - manual page for the monitor
846: . monitor      - the monitor function, this must use a `PetscViewerFormat` as its context
847: - monitorsetup - a function that is called once ONLY if the user selected this monitor that may set additional features of the `SNES` or `PetscViewer` objects

849:   Calling sequence of `monitor`:
850: + snes - the nonlinear solver context
851: . it   - the current iteration
852: . r    - the current function norm
853: - vf   - a `PetscViewerAndFormat` struct that contains the `PetscViewer` and `PetscViewerFormat` to use

855:   Calling sequence of `monitorsetup`:
856: + snes - the nonlinear solver context
857: - vf   - a `PetscViewerAndFormat` struct that contains the `PetscViewer` and `PetscViewerFormat` to use

859:   Options Database Key:
860: . -name - trigger the use of this monitor in `SNESSetFromOptions()`

862:   Level: advanced

864: .seealso: [](ch_snes), `PetscOptionsCreateViewer()`, `PetscOptionsGetReal()`, `PetscOptionsHasName()`, `PetscOptionsGetString()`,
865:           `PetscOptionsGetIntArray()`, `PetscOptionsGetRealArray()`, `PetscOptionsBool()`
866:           `PetscOptionsInt()`, `PetscOptionsString()`, `PetscOptionsReal()`,
867:           `PetscOptionsName()`, `PetscOptionsBegin()`, `PetscOptionsEnd()`, `PetscOptionsHeadBegin()`,
868:           `PetscOptionsStringArray()`, `PetscOptionsRealArray()`, `PetscOptionsScalar()`,
869:           `PetscOptionsBoolGroupBegin()`, `PetscOptionsBoolGroup()`, `PetscOptionsBoolGroupEnd()`,
870:           `PetscOptionsFList()`, `PetscOptionsEList()`
871: @*/
872: PetscErrorCode SNESMonitorSetFromOptions(SNES snes, const char name[], const char help[], const char manual[], PetscErrorCode (*monitor)(SNES snes, PetscInt it, PetscReal r, PetscViewerAndFormat *vf), PetscErrorCode (*monitorsetup)(SNES snes, PetscViewerAndFormat *vf))
873: {
874:   PetscViewer       viewer;
875:   PetscViewerFormat format;
876:   PetscBool         flg;

878:   PetscFunctionBegin;
879:   PetscCall(PetscOptionsCreateViewer(PetscObjectComm((PetscObject)snes), ((PetscObject)snes)->options, ((PetscObject)snes)->prefix, name, &viewer, &format, &flg));
880:   if (flg) {
881:     PetscViewerAndFormat *vf;
882:     PetscCall(PetscViewerAndFormatCreate(viewer, format, &vf));
883:     PetscCall(PetscViewerDestroy(&viewer));
884:     if (monitorsetup) PetscCall((*monitorsetup)(snes, vf));
885:     PetscCall(SNESMonitorSet(snes, (PetscErrorCode (*)(SNES, PetscInt, PetscReal, void *))monitor, vf, (PetscCtxDestroyFn *)PetscViewerAndFormatDestroy));
886:   }
887:   PetscFunctionReturn(PETSC_SUCCESS);
888: }

890: PetscErrorCode SNESEWSetFromOptions_Private(SNESKSPEW *kctx, PetscBool print_api, MPI_Comm comm, const char *prefix)
891: {
892:   const char *api = print_api ? "SNESKSPSetParametersEW" : NULL;

894:   PetscFunctionBegin;
895:   PetscOptionsBegin(comm, prefix, "Eisenstat and Walker type forcing options", "KSP");
896:   PetscCall(PetscOptionsInt("-ksp_ew_version", "Version 1, 2 or 3", api, kctx->version, &kctx->version, NULL));
897:   PetscCall(PetscOptionsReal("-ksp_ew_rtol0", "0 <= rtol0 < 1", api, kctx->rtol_0, &kctx->rtol_0, NULL));
898:   kctx->rtol_max = PetscMax(kctx->rtol_0, kctx->rtol_max);
899:   PetscCall(PetscOptionsReal("-ksp_ew_rtolmax", "0 <= rtolmax < 1", api, kctx->rtol_max, &kctx->rtol_max, NULL));
900:   PetscCall(PetscOptionsReal("-ksp_ew_gamma", "0 <= gamma <= 1", api, kctx->gamma, &kctx->gamma, NULL));
901:   PetscCall(PetscOptionsReal("-ksp_ew_alpha", "1 < alpha <= 2", api, kctx->alpha, &kctx->alpha, NULL));
902:   PetscCall(PetscOptionsReal("-ksp_ew_alpha2", "alpha2", NULL, kctx->alpha2, &kctx->alpha2, NULL));
903:   PetscCall(PetscOptionsReal("-ksp_ew_threshold", "0 < threshold < 1", api, kctx->threshold, &kctx->threshold, NULL));
904:   PetscCall(PetscOptionsReal("-ksp_ew_v4_p1", "p1", NULL, kctx->v4_p1, &kctx->v4_p1, NULL));
905:   PetscCall(PetscOptionsReal("-ksp_ew_v4_p2", "p2", NULL, kctx->v4_p2, &kctx->v4_p2, NULL));
906:   PetscCall(PetscOptionsReal("-ksp_ew_v4_p3", "p3", NULL, kctx->v4_p3, &kctx->v4_p3, NULL));
907:   PetscCall(PetscOptionsReal("-ksp_ew_v4_m1", "Scaling when rk-1 in [p2,p3)", NULL, kctx->v4_m1, &kctx->v4_m1, NULL));
908:   PetscCall(PetscOptionsReal("-ksp_ew_v4_m2", "Scaling when rk-1 in [p3,+infty)", NULL, kctx->v4_m2, &kctx->v4_m2, NULL));
909:   PetscCall(PetscOptionsReal("-ksp_ew_v4_m3", "Threshold for successive rtol (0.1 in Eq.7)", NULL, kctx->v4_m3, &kctx->v4_m3, NULL));
910:   PetscCall(PetscOptionsReal("-ksp_ew_v4_m4", "Adaptation scaling (0.5 in Eq.7)", NULL, kctx->v4_m4, &kctx->v4_m4, NULL));
911:   PetscOptionsEnd();
912:   PetscFunctionReturn(PETSC_SUCCESS);
913: }

915: /*@
916:   SNESSetFromOptions - Sets various `SNES` and `KSP` parameters from user options.

918:   Collective

920:   Input Parameter:
921: . snes - the `SNES` context

923:   Options Database Keys:
924: + -snes_type <type>                                                            - newtonls, newtontr, ngmres, ncg, nrichardson, qn, vi, fas, `SNESType` for complete list
925: . -snes_rtol <rtol>                                                            - relative decrease in tolerance norm from initial
926: . -snes_atol <abstol>                                                          - absolute tolerance of residual norm
927: . -snes_stol <stol>                                                            - convergence tolerance in terms of the norm of the change in the solution between steps
928: . -snes_divergence_tolerance <divtol>                                          - if the residual goes above divtol*rnorm0, exit with divergence
929: . -snes_max_it <max_it>                                                        - maximum number of iterations
930: . -snes_max_funcs <max_funcs>                                                  - maximum number of function evaluations
931: . -snes_force_iteration <force>                                                - force `SNESSolve()` to take at least one iteration
932: . -snes_max_fail <max_fail>                                                    - maximum number of line search failures allowed before stopping, default is none
933: . -snes_max_linear_solve_fail                                                  - number of linear solver failures before SNESSolve() stops
934: . -snes_lag_preconditioner <lag>                                               - how often preconditioner is rebuilt (use -1 to never rebuild)
935: . -snes_lag_preconditioner_persists <true,false>                               - retains the -snes_lag_preconditioner information across multiple SNESSolve()
936: . -snes_lag_jacobian <lag>                                                     - how often Jacobian is rebuilt (use -1 to never rebuild)
937: . -snes_lag_jacobian_persists <true,false>                                     - retains the -snes_lag_jacobian information across multiple SNESSolve()
938: . -snes_convergence_test <default,skip,correct_pressure>                       - convergence test in nonlinear solver. default `SNESConvergedDefault()`. skip `SNESConvergedSkip()` means continue iterating until max_it or some other criterion is reached, saving expense of convergence test. correct_pressure `SNESConvergedCorrectPressure()` has special handling of a pressure null space.
939: . -snes_monitor [ascii][:filename][:viewer format]                             - prints residual norm at each iteration. if no filename given prints to stdout
940: . -snes_monitor_solution [ascii binary draw][:filename][:viewer format]        - plots solution at each iteration
941: . -snes_monitor_residual [ascii binary draw][:filename][:viewer format]        - plots residual (not its norm) at each iteration
942: . -snes_monitor_solution_update [ascii binary draw][:filename][:viewer format] - plots update to solution at each iteration
943: . -snes_monitor_lg_residualnorm                                                - plots residual norm at each iteration
944: . -snes_monitor_lg_range                                                       - plots residual norm at each iteration
945: . -snes_monitor_pause_final                                                    - Pauses all monitor drawing after the solver ends
946: . -snes_fd                                                                     - use finite differences to compute Jacobian; very slow, only for testing
947: . -snes_fd_color                                                               - use finite differences with coloring to compute Jacobian
948: . -snes_mf_ksp_monitor                                                         - if using matrix-free multiply then print h at each `KSP` iteration
949: . -snes_converged_reason                                                       - print the reason for convergence/divergence after each solve
950: . -npc_snes_type <type>                                                        - the `SNES` type to use as a nonlinear preconditioner
951: . -snes_test_jacobian <optional threshold>                                     - compare the user provided Jacobian with one computed via finite differences to check for errors.  If a threshold is given, display only those entries whose difference is greater than the threshold.
952: - -snes_test_jacobian_view                                                     - display the user provided Jacobian, the finite difference Jacobian and the difference between them to help users detect the location of errors in the user provided Jacobian.

954:   Options Database Keys for Eisenstat-Walker method:
955: + -snes_ksp_ew                       - use Eisenstat-Walker method for determining linear system convergence
956: . -snes_ksp_ew_version ver           - version of  Eisenstat-Walker method
957: . -snes_ksp_ew_rtol0 <rtol0>         - Sets rtol0
958: . -snes_ksp_ew_rtolmax <rtolmax>     - Sets rtolmax
959: . -snes_ksp_ew_gamma <gamma>         - Sets gamma
960: . -snes_ksp_ew_alpha <alpha>         - Sets alpha
961: . -snes_ksp_ew_alpha2 <alpha2>       - Sets alpha2
962: - -snes_ksp_ew_threshold <threshold> - Sets threshold

964:   Level: beginner

966:   Notes:
967:   To see all options, run your program with the -help option or consult the users manual

969:   `SNES` supports three approaches for computing (approximate) Jacobians: user provided via `SNESSetJacobian()`, matrix-free using `MatCreateSNESMF()`,
970:   and computing explicitly with
971:   finite differences and coloring using `MatFDColoring`. It is also possible to use automatic differentiation and the `MatFDColoring` object.

973: .seealso: [](ch_snes), `SNESType`, `SNESSetOptionsPrefix()`, `SNESResetFromOptions()`, `SNES`, `SNESCreate()`, `MatCreateSNESMF()`, `MatFDColoring`
974: @*/
975: PetscErrorCode SNESSetFromOptions(SNES snes)
976: {
977:   PetscBool   flg, pcset, persist, set;
978:   PetscInt    i, indx, lag, grids, max_its, max_funcs;
979:   const char *deft        = SNESNEWTONLS;
980:   const char *convtests[] = {"default", "skip", "correct_pressure"};
981:   SNESKSPEW  *kctx        = NULL;
982:   char        type[256], monfilename[PETSC_MAX_PATH_LEN], ewprefix[256];
983:   PCSide      pcside;
984:   const char *optionsprefix;
985:   PetscReal   rtol, abstol, stol;

987:   PetscFunctionBegin;
989:   PetscCall(SNESRegisterAll());
990:   PetscObjectOptionsBegin((PetscObject)snes);
991:   if (((PetscObject)snes)->type_name) deft = ((PetscObject)snes)->type_name;
992:   PetscCall(PetscOptionsFList("-snes_type", "Nonlinear solver method", "SNESSetType", SNESList, deft, type, 256, &flg));
993:   if (flg) {
994:     PetscCall(SNESSetType(snes, type));
995:   } else if (!((PetscObject)snes)->type_name) {
996:     PetscCall(SNESSetType(snes, deft));
997:   }

999:   abstol    = snes->abstol;
1000:   rtol      = snes->rtol;
1001:   stol      = snes->stol;
1002:   max_its   = snes->max_its;
1003:   max_funcs = snes->max_funcs;
1004:   PetscCall(PetscOptionsReal("-snes_rtol", "Stop if decrease in function norm less than", "SNESSetTolerances", snes->rtol, &rtol, NULL));
1005:   PetscCall(PetscOptionsReal("-snes_atol", "Stop if function norm less than", "SNESSetTolerances", snes->abstol, &abstol, NULL));
1006:   PetscCall(PetscOptionsReal("-snes_stol", "Stop if step length less than", "SNESSetTolerances", snes->stol, &stol, NULL));
1007:   PetscCall(PetscOptionsInt("-snes_max_it", "Maximum iterations", "SNESSetTolerances", snes->max_its, &max_its, NULL));
1008:   PetscCall(PetscOptionsInt("-snes_max_funcs", "Maximum function evaluations", "SNESSetTolerances", snes->max_funcs, &max_funcs, NULL));
1009:   PetscCall(SNESSetTolerances(snes, abstol, rtol, stol, max_its, max_funcs));

1011:   PetscCall(PetscOptionsReal("-snes_divergence_tolerance", "Stop if residual norm increases by this factor", "SNESSetDivergenceTolerance", snes->divtol, &snes->divtol, &flg));
1012:   if (flg) PetscCall(SNESSetDivergenceTolerance(snes, snes->divtol));

1014:   PetscCall(PetscOptionsInt("-snes_max_fail", "Maximum nonlinear step failures", "SNESSetMaxNonlinearStepFailures", snes->maxFailures, &snes->maxFailures, &flg));
1015:   if (flg) PetscCall(SNESSetMaxNonlinearStepFailures(snes, snes->maxFailures));

1017:   PetscCall(PetscOptionsInt("-snes_max_linear_solve_fail", "Maximum failures in linear solves allowed", "SNESSetMaxLinearSolveFailures", snes->maxLinearSolveFailures, &snes->maxLinearSolveFailures, &flg));
1018:   if (flg) PetscCall(SNESSetMaxLinearSolveFailures(snes, snes->maxLinearSolveFailures));

1020:   PetscCall(PetscOptionsBool("-snes_error_if_not_converged", "Generate error if solver does not converge", "SNESSetErrorIfNotConverged", snes->errorifnotconverged, &snes->errorifnotconverged, NULL));
1021:   PetscCall(PetscOptionsBool("-snes_force_iteration", "Force SNESSolve() to take at least one iteration", "SNESSetForceIteration", snes->forceiteration, &snes->forceiteration, NULL));
1022:   PetscCall(PetscOptionsBool("-snes_check_jacobian_domain_error", "Check Jacobian domain error after Jacobian evaluation", "SNESCheckJacobianDomainError", snes->checkjacdomainerror, &snes->checkjacdomainerror, NULL));

1024:   PetscCall(PetscOptionsInt("-snes_lag_preconditioner", "How often to rebuild preconditioner", "SNESSetLagPreconditioner", snes->lagpreconditioner, &lag, &flg));
1025:   if (flg) {
1026:     PetscCheck(lag != -1, PetscObjectComm((PetscObject)snes), PETSC_ERR_USER, "Cannot set the lag to -1 from the command line since the preconditioner must be built as least once, perhaps you mean -2");
1027:     PetscCall(SNESSetLagPreconditioner(snes, lag));
1028:   }
1029:   PetscCall(PetscOptionsBool("-snes_lag_preconditioner_persists", "Preconditioner lagging through multiple SNES solves", "SNESSetLagPreconditionerPersists", snes->lagjac_persist, &persist, &flg));
1030:   if (flg) PetscCall(SNESSetLagPreconditionerPersists(snes, persist));
1031:   PetscCall(PetscOptionsInt("-snes_lag_jacobian", "How often to rebuild Jacobian", "SNESSetLagJacobian", snes->lagjacobian, &lag, &flg));
1032:   if (flg) {
1033:     PetscCheck(lag != -1, PetscObjectComm((PetscObject)snes), PETSC_ERR_USER, "Cannot set the lag to -1 from the command line since the Jacobian must be built as least once, perhaps you mean -2");
1034:     PetscCall(SNESSetLagJacobian(snes, lag));
1035:   }
1036:   PetscCall(PetscOptionsBool("-snes_lag_jacobian_persists", "Jacobian lagging through multiple SNES solves", "SNESSetLagJacobianPersists", snes->lagjac_persist, &persist, &flg));
1037:   if (flg) PetscCall(SNESSetLagJacobianPersists(snes, persist));

1039:   PetscCall(PetscOptionsInt("-snes_grid_sequence", "Use grid sequencing to generate initial guess", "SNESSetGridSequence", snes->gridsequence, &grids, &flg));
1040:   if (flg) PetscCall(SNESSetGridSequence(snes, grids));

1042:   PetscCall(PetscOptionsEList("-snes_convergence_test", "Convergence test", "SNESSetConvergenceTest", convtests, PETSC_STATIC_ARRAY_LENGTH(convtests), "default", &indx, &flg));
1043:   if (flg) {
1044:     switch (indx) {
1045:     case 0:
1046:       PetscCall(SNESSetConvergenceTest(snes, SNESConvergedDefault, NULL, NULL));
1047:       break;
1048:     case 1:
1049:       PetscCall(SNESSetConvergenceTest(snes, SNESConvergedSkip, NULL, NULL));
1050:       break;
1051:     case 2:
1052:       PetscCall(SNESSetConvergenceTest(snes, SNESConvergedCorrectPressure, NULL, NULL));
1053:       break;
1054:     }
1055:   }

1057:   PetscCall(PetscOptionsEList("-snes_norm_schedule", "SNES Norm schedule", "SNESSetNormSchedule", SNESNormSchedules, 5, "function", &indx, &flg));
1058:   if (flg) PetscCall(SNESSetNormSchedule(snes, (SNESNormSchedule)indx));

1060:   PetscCall(PetscOptionsEList("-snes_function_type", "SNES Norm schedule", "SNESSetFunctionType", SNESFunctionTypes, 2, "unpreconditioned", &indx, &flg));
1061:   if (flg) PetscCall(SNESSetFunctionType(snes, (SNESFunctionType)indx));

1063:   kctx = (SNESKSPEW *)snes->kspconvctx;

1065:   PetscCall(PetscOptionsBool("-snes_ksp_ew", "Use Eisentat-Walker linear system convergence test", "SNESKSPSetUseEW", snes->ksp_ewconv, &snes->ksp_ewconv, NULL));

1067:   PetscCall(SNESGetOptionsPrefix(snes, &optionsprefix));
1068:   PetscCall(PetscSNPrintf(ewprefix, sizeof(ewprefix), "%s%s", optionsprefix ? optionsprefix : "", "snes_"));
1069:   PetscCall(SNESEWSetFromOptions_Private(kctx, PETSC_TRUE, PetscObjectComm((PetscObject)snes), ewprefix));

1071:   flg = PETSC_FALSE;
1072:   PetscCall(PetscOptionsBool("-snes_monitor_cancel", "Remove all monitors", "SNESMonitorCancel", flg, &flg, &set));
1073:   if (set && flg) PetscCall(SNESMonitorCancel(snes));

1075:   PetscCall(SNESMonitorSetFromOptions(snes, "-snes_monitor", "Monitor norm of function", "SNESMonitorDefault", SNESMonitorDefault, SNESMonitorDefaultSetUp));
1076:   PetscCall(SNESMonitorSetFromOptions(snes, "-snes_monitor_short", "Monitor norm of function with fewer digits", "SNESMonitorDefaultShort", SNESMonitorDefaultShort, NULL));
1077:   PetscCall(SNESMonitorSetFromOptions(snes, "-snes_monitor_range", "Monitor range of elements of function", "SNESMonitorRange", SNESMonitorRange, NULL));

1079:   PetscCall(SNESMonitorSetFromOptions(snes, "-snes_monitor_ratio", "Monitor ratios of the norm of function for consecutive steps", "SNESMonitorRatio", SNESMonitorRatio, SNESMonitorRatioSetUp));
1080:   PetscCall(SNESMonitorSetFromOptions(snes, "-snes_monitor_field", "Monitor norm of function (split into fields)", "SNESMonitorDefaultField", SNESMonitorDefaultField, NULL));
1081:   PetscCall(SNESMonitorSetFromOptions(snes, "-snes_monitor_solution", "View solution at each iteration", "SNESMonitorSolution", SNESMonitorSolution, NULL));
1082:   PetscCall(SNESMonitorSetFromOptions(snes, "-snes_monitor_solution_update", "View correction at each iteration", "SNESMonitorSolutionUpdate", SNESMonitorSolutionUpdate, NULL));
1083:   PetscCall(SNESMonitorSetFromOptions(snes, "-snes_monitor_residual", "View residual at each iteration", "SNESMonitorResidual", SNESMonitorResidual, NULL));
1084:   PetscCall(SNESMonitorSetFromOptions(snes, "-snes_monitor_jacupdate_spectrum", "Print the change in the spectrum of the Jacobian", "SNESMonitorJacUpdateSpectrum", SNESMonitorJacUpdateSpectrum, NULL));
1085:   PetscCall(SNESMonitorSetFromOptions(snes, "-snes_monitor_fields", "Monitor norm of function per field", "SNESMonitorSet", SNESMonitorFields, NULL));
1086:   PetscCall(PetscOptionsBool("-snes_monitor_pause_final", "Pauses all draw monitors at the final iterate", "SNESMonitorPauseFinal_Internal", PETSC_FALSE, &snes->pauseFinal, NULL));

1088:   PetscCall(PetscOptionsString("-snes_monitor_python", "Use Python function", "SNESMonitorSet", NULL, monfilename, sizeof(monfilename), &flg));
1089:   if (flg) PetscCall(PetscPythonMonitorSet((PetscObject)snes, monfilename));

1091:   flg = PETSC_FALSE;
1092:   PetscCall(PetscOptionsBool("-snes_monitor_lg_range", "Plot function range at each iteration", "SNESMonitorLGRange", flg, &flg, NULL));
1093:   if (flg) {
1094:     PetscViewer ctx;

1096:     PetscCall(PetscViewerDrawOpen(PetscObjectComm((PetscObject)snes), NULL, NULL, PETSC_DECIDE, PETSC_DECIDE, 400, 300, &ctx));
1097:     PetscCall(SNESMonitorSet(snes, SNESMonitorLGRange, ctx, (PetscCtxDestroyFn *)PetscViewerDestroy));
1098:   }

1100:   PetscCall(PetscViewerDestroy(&snes->convergedreasonviewer));
1101:   PetscCall(PetscOptionsCreateViewer(PetscObjectComm((PetscObject)snes), ((PetscObject)snes)->options, ((PetscObject)snes)->prefix, "-snes_converged_reason", &snes->convergedreasonviewer, &snes->convergedreasonformat, NULL));
1102:   flg = PETSC_FALSE;
1103:   PetscCall(PetscOptionsBool("-snes_converged_reason_view_cancel", "Remove all converged reason viewers", "SNESConvergedReasonViewCancel", flg, &flg, &set));
1104:   if (set && flg) PetscCall(SNESConvergedReasonViewCancel(snes));

1106:   flg = PETSC_FALSE;
1107:   PetscCall(PetscOptionsBool("-snes_fd", "Use finite differences (slow) to compute Jacobian", "SNESComputeJacobianDefault", flg, &flg, NULL));
1108:   if (flg) {
1109:     void *functx;
1110:     DM    dm;
1111:     PetscCall(SNESGetDM(snes, &dm));
1112:     PetscCall(DMSNESUnsetJacobianContext_Internal(dm));
1113:     PetscCall(SNESGetFunction(snes, NULL, NULL, &functx));
1114:     PetscCall(SNESSetJacobian(snes, snes->jacobian, snes->jacobian_pre, SNESComputeJacobianDefault, functx));
1115:     PetscCall(PetscInfo(snes, "Setting default finite difference Jacobian matrix\n"));
1116:   }

1118:   flg = PETSC_FALSE;
1119:   PetscCall(PetscOptionsBool("-snes_fd_function", "Use finite differences (slow) to compute function from user objective", "SNESObjectiveComputeFunctionDefaultFD", flg, &flg, NULL));
1120:   if (flg) PetscCall(SNESSetFunction(snes, NULL, SNESObjectiveComputeFunctionDefaultFD, NULL));

1122:   flg = PETSC_FALSE;
1123:   PetscCall(PetscOptionsBool("-snes_fd_color", "Use finite differences with coloring to compute Jacobian", "SNESComputeJacobianDefaultColor", flg, &flg, NULL));
1124:   if (flg) {
1125:     DM dm;
1126:     PetscCall(SNESGetDM(snes, &dm));
1127:     PetscCall(DMSNESUnsetJacobianContext_Internal(dm));
1128:     PetscCall(SNESSetJacobian(snes, snes->jacobian, snes->jacobian_pre, SNESComputeJacobianDefaultColor, NULL));
1129:     PetscCall(PetscInfo(snes, "Setting default finite difference coloring Jacobian matrix\n"));
1130:   }

1132:   flg = PETSC_FALSE;
1133:   PetscCall(PetscOptionsBool("-snes_mf_operator", "Use a Matrix-Free Jacobian with user-provided matrix for computing the preconditioner", "SNESSetUseMatrixFree", PETSC_FALSE, &snes->mf_operator, &flg));
1134:   if (flg && snes->mf_operator) {
1135:     snes->mf_operator = PETSC_TRUE;
1136:     snes->mf          = PETSC_TRUE;
1137:   }
1138:   flg = PETSC_FALSE;
1139:   PetscCall(PetscOptionsBool("-snes_mf", "Use a Matrix-Free Jacobian with no matrix for computing the preconditioner", "SNESSetUseMatrixFree", PETSC_FALSE, &snes->mf, &flg));
1140:   if (!flg && snes->mf_operator) snes->mf = PETSC_TRUE;
1141:   PetscCall(PetscOptionsInt("-snes_mf_version", "Matrix-Free routines version 1 or 2", "None", snes->mf_version, &snes->mf_version, NULL));

1143:   PetscCall(PetscOptionsName("-snes_test_function", "Compare hand-coded and finite difference functions", "None", &snes->testFunc));
1144:   PetscCall(PetscOptionsName("-snes_test_jacobian", "Compare hand-coded and finite difference Jacobians", "None", &snes->testJac));

1146:   flg = PETSC_FALSE;
1147:   PetscCall(SNESGetNPCSide(snes, &pcside));
1148:   PetscCall(PetscOptionsEnum("-snes_npc_side", "SNES nonlinear preconditioner side", "SNESSetNPCSide", PCSides, (PetscEnum)pcside, (PetscEnum *)&pcside, &flg));
1149:   if (flg) PetscCall(SNESSetNPCSide(snes, pcside));

1151: #if defined(PETSC_HAVE_SAWS)
1152:   /*
1153:     Publish convergence information using SAWs
1154:   */
1155:   flg = PETSC_FALSE;
1156:   PetscCall(PetscOptionsBool("-snes_monitor_saws", "Publish SNES progress using SAWs", "SNESMonitorSet", flg, &flg, NULL));
1157:   if (flg) {
1158:     void *ctx;
1159:     PetscCall(SNESMonitorSAWsCreate(snes, &ctx));
1160:     PetscCall(SNESMonitorSet(snes, SNESMonitorSAWs, ctx, SNESMonitorSAWsDestroy));
1161:   }
1162: #endif
1163: #if defined(PETSC_HAVE_SAWS)
1164:   {
1165:     PetscBool set;
1166:     flg = PETSC_FALSE;
1167:     PetscCall(PetscOptionsBool("-snes_saws_block", "Block for SAWs at end of SNESSolve", "PetscObjectSAWsBlock", ((PetscObject)snes)->amspublishblock, &flg, &set));
1168:     if (set) PetscCall(PetscObjectSAWsSetBlock((PetscObject)snes, flg));
1169:   }
1170: #endif

1172:   for (i = 0; i < numberofsetfromoptions; i++) PetscCall((*othersetfromoptions[i])(snes));

1174:   PetscTryTypeMethod(snes, setfromoptions, PetscOptionsObject);

1176:   /* process any options handlers added with PetscObjectAddOptionsHandler() */
1177:   PetscCall(PetscObjectProcessOptionsHandlers((PetscObject)snes, PetscOptionsObject));
1178:   PetscOptionsEnd();

1180:   if (snes->linesearch) {
1181:     PetscCall(SNESGetLineSearch(snes, &snes->linesearch));
1182:     PetscCall(SNESLineSearchSetFromOptions(snes->linesearch));
1183:   }

1185:   if (snes->usesksp) {
1186:     if (!snes->ksp) PetscCall(SNESGetKSP(snes, &snes->ksp));
1187:     PetscCall(KSPSetOperators(snes->ksp, snes->jacobian, snes->jacobian_pre));
1188:     PetscCall(KSPSetFromOptions(snes->ksp));
1189:   }

1191:   /* if user has set the SNES NPC type via options database, create it. */
1192:   PetscCall(SNESGetOptionsPrefix(snes, &optionsprefix));
1193:   PetscCall(PetscOptionsHasName(((PetscObject)snes)->options, optionsprefix, "-npc_snes_type", &pcset));
1194:   if (pcset && (!snes->npc)) PetscCall(SNESGetNPC(snes, &snes->npc));
1195:   if (snes->npc) PetscCall(SNESSetFromOptions(snes->npc));
1196:   snes->setfromoptionscalled++;
1197:   PetscFunctionReturn(PETSC_SUCCESS);
1198: }

1200: /*@
1201:   SNESResetFromOptions - Sets various `SNES` and `KSP` parameters from user options ONLY if the `SNESSetFromOptions()` was previously called

1203:   Collective

1205:   Input Parameter:
1206: . snes - the `SNES` context

1208:   Level: advanced

1210: .seealso: [](ch_snes), `SNES`, `SNESSetFromOptions()`, `SNESSetOptionsPrefix()`
1211: @*/
1212: PetscErrorCode SNESResetFromOptions(SNES snes)
1213: {
1214:   PetscFunctionBegin;
1215:   if (snes->setfromoptionscalled) PetscCall(SNESSetFromOptions(snes));
1216:   PetscFunctionReturn(PETSC_SUCCESS);
1217: }

1219: /*@C
1220:   SNESSetComputeApplicationContext - Sets an optional function to compute a user-defined context for
1221:   the nonlinear solvers.

1223:   Logically Collective; No Fortran Support

1225:   Input Parameters:
1226: + snes    - the `SNES` context
1227: . compute - function to compute the context
1228: - destroy - function to destroy the context, see `PetscCtxDestroyFn` for the calling sequence

1230:   Calling sequence of `compute`:
1231: + snes - the `SNES` context
1232: - ctx  - context to be computed

1234:   Level: intermediate

1236:   Note:
1237:   This routine is useful if you are performing grid sequencing or using `SNESFAS` and need the appropriate context generated for each level.

1239:   Use `SNESSetApplicationContext()` to see the context immediately

1241: .seealso: [](ch_snes), `SNESGetApplicationContext()`, `SNESSetApplicationContext()`, `PetscCtxDestroyFn`
1242: @*/
1243: PetscErrorCode SNESSetComputeApplicationContext(SNES snes, PetscErrorCode (*compute)(SNES snes, void **ctx), PetscCtxDestroyFn *destroy)
1244: {
1245:   PetscFunctionBegin;
1247:   snes->ops->usercompute = compute;
1248:   snes->ops->ctxdestroy  = destroy;
1249:   PetscFunctionReturn(PETSC_SUCCESS);
1250: }

1252: /*@
1253:   SNESSetApplicationContext - Sets the optional user-defined context for the nonlinear solvers.

1255:   Logically Collective

1257:   Input Parameters:
1258: + snes - the `SNES` context
1259: - ctx  - the user context

1261:   Level: intermediate

1263:   Notes:
1264:   Users can provide a context when constructing the `SNES` options and then access it inside their function, Jacobian computation, or other evaluation function
1265:   with `SNESGetApplicationContext()`

1267:   To provide a function that computes the context for you use `SNESSetComputeApplicationContext()`

1269:   Fortran Note:
1270:   This only works when `ctx` is a Fortran derived type (it cannot be a `PetscObject`), we recommend writing a Fortran interface definition for this
1271:   function that tells the Fortran compiler the derived data type that is passed in as the `ctx` argument. See `SNESGetApplicationContext()` for
1272:   an example.

1274: .seealso: [](ch_snes), `SNES`, `SNESSetComputeApplicationContext()`, `SNESGetApplicationContext()`
1275: @*/
1276: PetscErrorCode SNESSetApplicationContext(SNES snes, void *ctx)
1277: {
1278:   KSP ksp;

1280:   PetscFunctionBegin;
1282:   PetscCall(SNESGetKSP(snes, &ksp));
1283:   PetscCall(KSPSetApplicationContext(ksp, ctx));
1284:   snes->ctx = ctx;
1285:   PetscFunctionReturn(PETSC_SUCCESS);
1286: }

1288: /*@
1289:   SNESGetApplicationContext - Gets the user-defined context for the
1290:   nonlinear solvers set with `SNESGetApplicationContext()` or `SNESSetComputeApplicationContext()`

1292:   Not Collective

1294:   Input Parameter:
1295: . snes - `SNES` context

1297:   Output Parameter:
1298: . ctx - user context

1300:   Level: intermediate

1302:   Fortran Notes:
1303:   This only works when the context is a Fortran derived type (it cannot be a `PetscObject`) and you **must** write a Fortran interface definition for this
1304:   function that tells the Fortran compiler the derived data type that is returned as the `ctx` argument. For example,
1305: .vb
1306:   Interface SNESGetApplicationContext
1307:     Subroutine SNESGetApplicationContext(snes,ctx,ierr)
1308:   #include <petsc/finclude/petscsnes.h>
1309:       use petscsnes
1310:       SNES snes
1311:       type(tUsertype), pointer :: ctx
1312:       PetscErrorCode ierr
1313:     End Subroutine
1314:   End Interface SNESGetApplicationContext
1315: .ve

1317:   The prototype for `ctx` must be
1318: .vb
1319:   type(tUsertype), pointer :: ctx
1320: .ve

1322: .seealso: [](ch_snes), `SNESSetApplicationContext()`, `SNESSetComputeApplicationContext()`
1323: @*/
1324: PetscErrorCode SNESGetApplicationContext(SNES snes, PeCtx ctx)
1325: {
1326:   PetscFunctionBegin;
1328:   *(void **)ctx = snes->ctx;
1329:   PetscFunctionReturn(PETSC_SUCCESS);
1330: }

1332: /*@
1333:   SNESSetUseMatrixFree - indicates that `SNES` should use matrix-free finite difference matrix-vector products to apply the Jacobian.

1335:   Logically Collective

1337:   Input Parameters:
1338: + snes        - `SNES` context
1339: . mf_operator - use matrix-free only for the Amat used by `SNESSetJacobian()`, this means the user provided Pmat will continue to be used
1340: - mf          - use matrix-free for both the Amat and Pmat used by `SNESSetJacobian()`, both the Amat and Pmat set in `SNESSetJacobian()` will be ignored. With
1341:                 this option no matrix-element based preconditioners can be used in the linear solve since the matrix won't be explicitly available

1343:   Options Database Keys:
1344: + -snes_mf_operator - use matrix-free only for the mat operator
1345: . -snes_mf          - use matrix-free for both the mat and pmat operator
1346: . -snes_fd_color    - compute the Jacobian via coloring and finite differences.
1347: - -snes_fd          - compute the Jacobian via finite differences (slow)

1349:   Level: intermediate

1351:   Note:
1352:   `SNES` supports three approaches for computing (approximate) Jacobians: user provided via `SNESSetJacobian()`, matrix-free using `MatCreateSNESMF()`,
1353:   and computing explicitly with
1354:   finite differences and coloring using `MatFDColoring`. It is also possible to use automatic differentiation and the `MatFDColoring` object.

1356: .seealso: [](ch_snes), `SNES`, `SNESGetUseMatrixFree()`, `MatCreateSNESMF()`, `SNESComputeJacobianDefaultColor()`, `MatFDColoring`
1357: @*/
1358: PetscErrorCode SNESSetUseMatrixFree(SNES snes, PetscBool mf_operator, PetscBool mf)
1359: {
1360:   PetscFunctionBegin;
1364:   snes->mf          = mf_operator ? PETSC_TRUE : mf;
1365:   snes->mf_operator = mf_operator;
1366:   PetscFunctionReturn(PETSC_SUCCESS);
1367: }

1369: /*@
1370:   SNESGetUseMatrixFree - indicates if the `SNES` uses matrix-free finite difference matrix vector products to apply the Jacobian.

1372:   Not Collective, but the resulting flags will be the same on all MPI processes

1374:   Input Parameter:
1375: . snes - `SNES` context

1377:   Output Parameters:
1378: + mf_operator - use matrix-free only for the Amat used by `SNESSetJacobian()`, this means the user provided Pmat will continue to be used
1379: - mf          - use matrix-free for both the Amat and Pmat used by `SNESSetJacobian()`, both the Amat and Pmat set in `SNESSetJacobian()` will be ignored

1381:   Level: intermediate

1383: .seealso: [](ch_snes), `SNES`, `SNESSetUseMatrixFree()`, `MatCreateSNESMF()`
1384: @*/
1385: PetscErrorCode SNESGetUseMatrixFree(SNES snes, PetscBool *mf_operator, PetscBool *mf)
1386: {
1387:   PetscFunctionBegin;
1389:   if (mf) *mf = snes->mf;
1390:   if (mf_operator) *mf_operator = snes->mf_operator;
1391:   PetscFunctionReturn(PETSC_SUCCESS);
1392: }

1394: /*@
1395:   SNESGetIterationNumber - Gets the number of nonlinear iterations completed in the current or most recent `SNESSolve()`

1397:   Not Collective

1399:   Input Parameter:
1400: . snes - `SNES` context

1402:   Output Parameter:
1403: . iter - iteration number

1405:   Level: intermediate

1407:   Notes:
1408:   For example, during the computation of iteration 2 this would return 1.

1410:   This is useful for using lagged Jacobians (where one does not recompute the
1411:   Jacobian at each `SNES` iteration). For example, the code
1412: .vb
1413:       ierr = SNESGetIterationNumber(snes,&it);
1414:       if (!(it % 2)) {
1415:         [compute Jacobian here]
1416:       }
1417: .ve
1418:   can be used in your function that computes the Jacobian to cause the Jacobian to be
1419:   recomputed every second `SNES` iteration. See also `SNESSetLagJacobian()`

1421:   After the `SNES` solve is complete this will return the number of nonlinear iterations used.

1423: .seealso: [](ch_snes), `SNES`, `SNESSolve()`, `SNESSetLagJacobian()`, `SNESGetLinearSolveIterations()`, `SNESSetMonitor()`
1424: @*/
1425: PetscErrorCode SNESGetIterationNumber(SNES snes, PetscInt *iter)
1426: {
1427:   PetscFunctionBegin;
1429:   PetscAssertPointer(iter, 2);
1430:   *iter = snes->iter;
1431:   PetscFunctionReturn(PETSC_SUCCESS);
1432: }

1434: /*@
1435:   SNESSetIterationNumber - Sets the current iteration number.

1437:   Not Collective

1439:   Input Parameters:
1440: + snes - `SNES` context
1441: - iter - iteration number

1443:   Level: developer

1445:   Note:
1446:   This should only be called inside a `SNES` nonlinear solver.

1448: .seealso: [](ch_snes), `SNESGetLinearSolveIterations()`
1449: @*/
1450: PetscErrorCode SNESSetIterationNumber(SNES snes, PetscInt iter)
1451: {
1452:   PetscFunctionBegin;
1454:   PetscCall(PetscObjectSAWsTakeAccess((PetscObject)snes));
1455:   snes->iter = iter;
1456:   PetscCall(PetscObjectSAWsGrantAccess((PetscObject)snes));
1457:   PetscFunctionReturn(PETSC_SUCCESS);
1458: }

1460: /*@
1461:   SNESGetNonlinearStepFailures - Gets the number of unsuccessful steps
1462:   attempted by the nonlinear solver in the current or most recent `SNESSolve()` .

1464:   Not Collective

1466:   Input Parameter:
1467: . snes - `SNES` context

1469:   Output Parameter:
1470: . nfails - number of unsuccessful steps attempted

1472:   Level: intermediate

1474:   Note:
1475:   This counter is reset to zero for each successive call to `SNESSolve()`.

1477: .seealso: [](ch_snes), `SNES`, `SNESGetMaxLinearSolveFailures()`, `SNESGetLinearSolveIterations()`, `SNESSetMaxLinearSolveFailures()`, `SNESGetLinearSolveFailures()`,
1478:           `SNESSetMaxNonlinearStepFailures()`, `SNESGetMaxNonlinearStepFailures()`
1479: @*/
1480: PetscErrorCode SNESGetNonlinearStepFailures(SNES snes, PetscInt *nfails)
1481: {
1482:   PetscFunctionBegin;
1484:   PetscAssertPointer(nfails, 2);
1485:   *nfails = snes->numFailures;
1486:   PetscFunctionReturn(PETSC_SUCCESS);
1487: }

1489: /*@
1490:   SNESSetMaxNonlinearStepFailures - Sets the maximum number of unsuccessful steps
1491:   attempted by the nonlinear solver before it gives up and returns unconverged or generates an error

1493:   Not Collective

1495:   Input Parameters:
1496: + snes     - `SNES` context
1497: - maxFails - maximum of unsuccessful steps allowed, use `PETSC_UNLIMITED` to have no limit on the number of failures

1499:   Options Database Key:
1500: . -snes_max_fail <n> - maximum number of unsuccessful steps allowed

1502:   Level: intermediate

1504:   Developer Note:
1505:   The options database key is wrong for this function name

1507: .seealso: [](ch_snes), `SNESSetErrorIfNotConverged()`, `SNESGetMaxLinearSolveFailures()`, `SNESGetLinearSolveIterations()`, `SNESSetMaxLinearSolveFailures()`, `SNESGetLinearSolveFailures()`,
1508:           `SNESGetMaxNonlinearStepFailures()`, `SNESGetNonlinearStepFailures()`
1509: @*/
1510: PetscErrorCode SNESSetMaxNonlinearStepFailures(SNES snes, PetscInt maxFails)
1511: {
1512:   PetscFunctionBegin;

1515:   if (maxFails == PETSC_UNLIMITED) {
1516:     snes->maxFailures = PETSC_INT_MAX;
1517:   } else {
1518:     PetscCheck(maxFails >= 0, PetscObjectComm((PetscObject)snes), PETSC_ERR_ARG_OUTOFRANGE, "Cannot have a negative maximum number of failures");
1519:     snes->maxFailures = maxFails;
1520:   }
1521:   PetscFunctionReturn(PETSC_SUCCESS);
1522: }

1524: /*@
1525:   SNESGetMaxNonlinearStepFailures - Gets the maximum number of unsuccessful steps
1526:   attempted by the nonlinear solver before it gives up and returns unconverged or generates an error

1528:   Not Collective

1530:   Input Parameter:
1531: . snes - `SNES` context

1533:   Output Parameter:
1534: . maxFails - maximum of unsuccessful steps

1536:   Level: intermediate

1538: .seealso: [](ch_snes), `SNESSetErrorIfNotConverged()`, `SNESGetMaxLinearSolveFailures()`, `SNESGetLinearSolveIterations()`, `SNESSetMaxLinearSolveFailures()`, `SNESGetLinearSolveFailures()`,
1539:           `SNESSetMaxNonlinearStepFailures()`, `SNESGetNonlinearStepFailures()`
1540: @*/
1541: PetscErrorCode SNESGetMaxNonlinearStepFailures(SNES snes, PetscInt *maxFails)
1542: {
1543:   PetscFunctionBegin;
1545:   PetscAssertPointer(maxFails, 2);
1546:   *maxFails = snes->maxFailures;
1547:   PetscFunctionReturn(PETSC_SUCCESS);
1548: }

1550: /*@
1551:   SNESGetNumberFunctionEvals - Gets the number of user provided function evaluations
1552:   done by the `SNES` object in the current or most recent `SNESSolve()`

1554:   Not Collective

1556:   Input Parameter:
1557: . snes - `SNES` context

1559:   Output Parameter:
1560: . nfuncs - number of evaluations

1562:   Level: intermediate

1564:   Note:
1565:   Reset every time `SNESSolve()` is called unless `SNESSetCountersReset()` is used.

1567: .seealso: [](ch_snes), `SNES`, `SNESGetMaxLinearSolveFailures()`, `SNESGetLinearSolveIterations()`, `SNESSetMaxLinearSolveFailures()`, `SNESGetLinearSolveFailures()`, `SNESSetCountersReset()`
1568: @*/
1569: PetscErrorCode SNESGetNumberFunctionEvals(SNES snes, PetscInt *nfuncs)
1570: {
1571:   PetscFunctionBegin;
1573:   PetscAssertPointer(nfuncs, 2);
1574:   *nfuncs = snes->nfuncs;
1575:   PetscFunctionReturn(PETSC_SUCCESS);
1576: }

1578: /*@
1579:   SNESGetLinearSolveFailures - Gets the number of failed (non-converged)
1580:   linear solvers in the current or most recent `SNESSolve()`

1582:   Not Collective

1584:   Input Parameter:
1585: . snes - `SNES` context

1587:   Output Parameter:
1588: . nfails - number of failed solves

1590:   Options Database Key:
1591: . -snes_max_linear_solve_fail <num> - The number of failures before the solve is terminated

1593:   Level: intermediate

1595:   Note:
1596:   This counter is reset to zero for each successive call to `SNESSolve()`.

1598: .seealso: [](ch_snes), `SNESGetMaxLinearSolveFailures()`, `SNESGetLinearSolveIterations()`, `SNESSetMaxLinearSolveFailures()`
1599: @*/
1600: PetscErrorCode SNESGetLinearSolveFailures(SNES snes, PetscInt *nfails)
1601: {
1602:   PetscFunctionBegin;
1604:   PetscAssertPointer(nfails, 2);
1605:   *nfails = snes->numLinearSolveFailures;
1606:   PetscFunctionReturn(PETSC_SUCCESS);
1607: }

1609: /*@
1610:   SNESSetMaxLinearSolveFailures - the number of failed linear solve attempts
1611:   allowed before `SNES` returns with a diverged reason of `SNES_DIVERGED_LINEAR_SOLVE`

1613:   Logically Collective

1615:   Input Parameters:
1616: + snes     - `SNES` context
1617: - maxFails - maximum allowed linear solve failures, use `PETSC_UNLIMITED` to have no limit on the number of failures

1619:   Options Database Key:
1620: . -snes_max_linear_solve_fail <num> - The number of failures before the solve is terminated

1622:   Level: intermediate

1624:   Note:
1625:   By default this is 0; that is `SNES` returns on the first failed linear solve

1627:   Developer Note:
1628:   The options database key is wrong for this function name

1630: .seealso: [](ch_snes), `SNESSetErrorIfNotConverged()`, `SNESGetLinearSolveFailures()`, `SNESGetMaxLinearSolveFailures()`, `SNESGetLinearSolveIterations()`
1631: @*/
1632: PetscErrorCode SNESSetMaxLinearSolveFailures(SNES snes, PetscInt maxFails)
1633: {
1634:   PetscFunctionBegin;

1638:   if (maxFails == PETSC_UNLIMITED) {
1639:     snes->maxLinearSolveFailures = PETSC_INT_MAX;
1640:   } else {
1641:     PetscCheck(maxFails >= 0, PetscObjectComm((PetscObject)snes), PETSC_ERR_ARG_OUTOFRANGE, "Cannot have a negative maximum number of failures");
1642:     snes->maxLinearSolveFailures = maxFails;
1643:   }
1644:   PetscFunctionReturn(PETSC_SUCCESS);
1645: }

1647: /*@
1648:   SNESGetMaxLinearSolveFailures - gets the maximum number of linear solve failures that
1649:   are allowed before `SNES` returns as unsuccessful

1651:   Not Collective

1653:   Input Parameter:
1654: . snes - `SNES` context

1656:   Output Parameter:
1657: . maxFails - maximum of unsuccessful solves allowed

1659:   Level: intermediate

1661:   Note:
1662:   By default this is 1; that is `SNES` returns on the first failed linear solve

1664: .seealso: [](ch_snes), `SNESSetErrorIfNotConverged()`, `SNESGetLinearSolveFailures()`, `SNESGetLinearSolveIterations()`, `SNESSetMaxLinearSolveFailures()`,
1665: @*/
1666: PetscErrorCode SNESGetMaxLinearSolveFailures(SNES snes, PetscInt *maxFails)
1667: {
1668:   PetscFunctionBegin;
1670:   PetscAssertPointer(maxFails, 2);
1671:   *maxFails = snes->maxLinearSolveFailures;
1672:   PetscFunctionReturn(PETSC_SUCCESS);
1673: }

1675: /*@
1676:   SNESGetLinearSolveIterations - Gets the total number of linear iterations
1677:   used by the nonlinear solver in the most recent `SNESSolve()`

1679:   Not Collective

1681:   Input Parameter:
1682: . snes - `SNES` context

1684:   Output Parameter:
1685: . lits - number of linear iterations

1687:   Level: intermediate

1689:   Notes:
1690:   This counter is reset to zero for each successive call to `SNESSolve()` unless `SNESSetCountersReset()` is used.

1692:   If the linear solver fails inside the `SNESSolve()` the iterations for that call to the linear solver are not included. If you wish to count them
1693:   then call `KSPGetIterationNumber()` after the failed solve.

1695: .seealso: [](ch_snes), `SNES`, `SNESGetIterationNumber()`, `SNESGetLinearSolveFailures()`, `SNESGetMaxLinearSolveFailures()`, `SNESSetCountersReset()`
1696: @*/
1697: PetscErrorCode SNESGetLinearSolveIterations(SNES snes, PetscInt *lits)
1698: {
1699:   PetscFunctionBegin;
1701:   PetscAssertPointer(lits, 2);
1702:   *lits = snes->linear_its;
1703:   PetscFunctionReturn(PETSC_SUCCESS);
1704: }

1706: /*@
1707:   SNESSetCountersReset - Sets whether or not the counters for linear iterations and function evaluations
1708:   are reset every time `SNESSolve()` is called.

1710:   Logically Collective

1712:   Input Parameters:
1713: + snes  - `SNES` context
1714: - reset - whether to reset the counters or not, defaults to `PETSC_TRUE`

1716:   Level: developer

1718: .seealso: [](ch_snes), `SNESGetNumberFunctionEvals()`, `SNESGetLinearSolveIterations()`, `SNESGetNPC()`
1719: @*/
1720: PetscErrorCode SNESSetCountersReset(SNES snes, PetscBool reset)
1721: {
1722:   PetscFunctionBegin;
1725:   snes->counters_reset = reset;
1726:   PetscFunctionReturn(PETSC_SUCCESS);
1727: }

1729: /*@
1730:   SNESResetCounters - Reset counters for linear iterations and function evaluations.

1732:   Logically Collective

1734:   Input Parameters:
1735: . snes - `SNES` context

1737:   Level: developer

1739:   Note:
1740:   It honors the flag set with `SNESSetCountersReset()`

1742: .seealso: [](ch_snes), `SNESGetNumberFunctionEvals()`, `SNESGetLinearSolveIterations()`, `SNESGetNPC()`
1743: @*/
1744: PetscErrorCode SNESResetCounters(SNES snes)
1745: {
1746:   PetscFunctionBegin;
1748:   if (snes->counters_reset) {
1749:     snes->nfuncs      = 0;
1750:     snes->linear_its  = 0;
1751:     snes->numFailures = 0;
1752:   }
1753:   PetscFunctionReturn(PETSC_SUCCESS);
1754: }

1756: /*@
1757:   SNESSetKSP - Sets a `KSP` context for the `SNES` object to use

1759:   Not Collective, but the `SNES` and `KSP` objects must live on the same `MPI_Comm`

1761:   Input Parameters:
1762: + snes - the `SNES` context
1763: - ksp  - the `KSP` context

1765:   Level: developer

1767:   Notes:
1768:   The `SNES` object already has its `KSP` object, you can obtain with `SNESGetKSP()`
1769:   so this routine is rarely needed.

1771:   The `KSP` object that is already in the `SNES` object has its reference count
1772:   decreased by one when this is called.

1774: .seealso: [](ch_snes), `SNES`, `KSP`, `KSPGetPC()`, `SNESCreate()`, `KSPCreate()`
1775: @*/
1776: PetscErrorCode SNESSetKSP(SNES snes, KSP ksp)
1777: {
1778:   PetscFunctionBegin;
1781:   PetscCheckSameComm(snes, 1, ksp, 2);
1782:   PetscCall(PetscObjectReference((PetscObject)ksp));
1783:   if (snes->ksp) PetscCall(PetscObjectDereference((PetscObject)snes->ksp));
1784:   snes->ksp = ksp;
1785:   PetscFunctionReturn(PETSC_SUCCESS);
1786: }

1788: /*@
1789:   SNESParametersInitialize - Sets all the parameters in `snes` to their default value (when `SNESCreate()` was called) if they
1790:   currently contain default values

1792:   Collective

1794:   Input Parameter:
1795: . snes - the `SNES` object

1797:   Level: developer

1799:   Developer Note:
1800:   This is called by all the `SNESCreate_XXX()` routines.

1802: .seealso: [](ch_snes), `SNES`, `SNESSolve()`, `SNESDestroy()`, `SNESSetLagPreconditioner()`, `SNESSetLagJacobian()`,
1803:           `PetscObjectParameterSetDefault()`
1804: @*/
1805: PetscErrorCode SNESParametersInitialize(SNES snes)
1806: {
1807:   PetscObjectParameterSetDefault(snes, max_its, 50);
1808:   PetscObjectParameterSetDefault(snes, max_funcs, 10000);
1809:   PetscObjectParameterSetDefault(snes, rtol, PetscDefined(USE_REAL_SINGLE) ? 1.e-5 : 1.e-8);
1810:   PetscObjectParameterSetDefault(snes, abstol, PetscDefined(USE_REAL_SINGLE) ? 1.e-25 : 1.e-50);
1811:   PetscObjectParameterSetDefault(snes, stol, PetscDefined(USE_REAL_SINGLE) ? 1.e-5 : 1.e-8);
1812:   PetscObjectParameterSetDefault(snes, divtol, 1.e4);
1813:   return PETSC_SUCCESS;
1814: }

1816: /*@
1817:   SNESCreate - Creates a nonlinear solver context used to manage a set of nonlinear solves

1819:   Collective

1821:   Input Parameter:
1822: . comm - MPI communicator

1824:   Output Parameter:
1825: . outsnes - the new `SNES` context

1827:   Options Database Keys:
1828: + -snes_mf          - Activates default matrix-free Jacobian-vector products, and no matrix to construct a preconditioner
1829: . -snes_mf_operator - Activates default matrix-free Jacobian-vector products, and a user-provided matrix as set by `SNESSetJacobian()`
1830: . -snes_fd_coloring - uses a relative fast computation of the Jacobian using finite differences and a graph coloring
1831: - -snes_fd          - Uses (slow!) finite differences to compute Jacobian

1833:   Level: beginner

1835:   Developer Notes:
1836:   `SNES` always creates a `KSP` object even though many `SNES` methods do not use it. This is
1837:   unfortunate and should be fixed at some point. The flag snes->usesksp indicates if the
1838:   particular method does use `KSP` and regulates if the information about the `KSP` is printed
1839:   in `SNESView()`.

1841:   `TSSetFromOptions()` does call `SNESSetFromOptions()` which can lead to users being confused
1842:   by help messages about meaningless `SNES` options.

1844:   `SNES` always creates the `snes->kspconvctx` even though it is used by only one type. This should be fixed.

1846: .seealso: [](ch_snes), `SNES`, `SNESSolve()`, `SNESDestroy()`, `SNESSetLagPreconditioner()`, `SNESSetLagJacobian()`
1847: @*/
1848: PetscErrorCode SNESCreate(MPI_Comm comm, SNES *outsnes)
1849: {
1850:   SNES       snes;
1851:   SNESKSPEW *kctx;

1853:   PetscFunctionBegin;
1854:   PetscAssertPointer(outsnes, 2);
1855:   PetscCall(SNESInitializePackage());

1857:   PetscCall(PetscHeaderCreate(snes, SNES_CLASSID, "SNES", "Nonlinear solver", "SNES", comm, SNESDestroy, SNESView));
1858:   snes->ops->converged = SNESConvergedDefault;
1859:   snes->usesksp        = PETSC_TRUE;
1860:   snes->norm           = 0.0;
1861:   snes->xnorm          = 0.0;
1862:   snes->ynorm          = 0.0;
1863:   snes->normschedule   = SNES_NORM_ALWAYS;
1864:   snes->functype       = SNES_FUNCTION_DEFAULT;
1865:   snes->ttol           = 0.0;

1867:   snes->rnorm0               = 0;
1868:   snes->nfuncs               = 0;
1869:   snes->numFailures          = 0;
1870:   snes->maxFailures          = 1;
1871:   snes->linear_its           = 0;
1872:   snes->lagjacobian          = 1;
1873:   snes->jac_iter             = 0;
1874:   snes->lagjac_persist       = PETSC_FALSE;
1875:   snes->lagpreconditioner    = 1;
1876:   snes->pre_iter             = 0;
1877:   snes->lagpre_persist       = PETSC_FALSE;
1878:   snes->numbermonitors       = 0;
1879:   snes->numberreasonviews    = 0;
1880:   snes->data                 = NULL;
1881:   snes->setupcalled          = PETSC_FALSE;
1882:   snes->ksp_ewconv           = PETSC_FALSE;
1883:   snes->nwork                = 0;
1884:   snes->work                 = NULL;
1885:   snes->nvwork               = 0;
1886:   snes->vwork                = NULL;
1887:   snes->conv_hist_len        = 0;
1888:   snes->conv_hist_max        = 0;
1889:   snes->conv_hist            = NULL;
1890:   snes->conv_hist_its        = NULL;
1891:   snes->conv_hist_reset      = PETSC_TRUE;
1892:   snes->counters_reset       = PETSC_TRUE;
1893:   snes->vec_func_init_set    = PETSC_FALSE;
1894:   snes->reason               = SNES_CONVERGED_ITERATING;
1895:   snes->npcside              = PC_RIGHT;
1896:   snes->setfromoptionscalled = 0;

1898:   snes->mf          = PETSC_FALSE;
1899:   snes->mf_operator = PETSC_FALSE;
1900:   snes->mf_version  = 1;

1902:   snes->numLinearSolveFailures = 0;
1903:   snes->maxLinearSolveFailures = 1;

1905:   snes->vizerotolerance     = 1.e-8;
1906:   snes->checkjacdomainerror = PetscDefined(USE_DEBUG) ? PETSC_TRUE : PETSC_FALSE;

1908:   /* Set this to true if the implementation of SNESSolve_XXX does compute the residual at the final solution. */
1909:   snes->alwayscomputesfinalresidual = PETSC_FALSE;

1911:   /* Create context to compute Eisenstat-Walker relative tolerance for KSP */
1912:   PetscCall(PetscNew(&kctx));

1914:   snes->kspconvctx  = kctx;
1915:   kctx->version     = 2;
1916:   kctx->rtol_0      = 0.3; /* Eisenstat and Walker suggest rtol_0=.5, but
1917:                              this was too large for some test cases */
1918:   kctx->rtol_last   = 0.0;
1919:   kctx->rtol_max    = 0.9;
1920:   kctx->gamma       = 1.0;
1921:   kctx->alpha       = 0.5 * (1.0 + PetscSqrtReal(5.0));
1922:   kctx->alpha2      = kctx->alpha;
1923:   kctx->threshold   = 0.1;
1924:   kctx->lresid_last = 0.0;
1925:   kctx->norm_last   = 0.0;

1927:   kctx->rk_last     = 0.0;
1928:   kctx->rk_last_2   = 0.0;
1929:   kctx->rtol_last_2 = 0.0;
1930:   kctx->v4_p1       = 0.1;
1931:   kctx->v4_p2       = 0.4;
1932:   kctx->v4_p3       = 0.7;
1933:   kctx->v4_m1       = 0.8;
1934:   kctx->v4_m2       = 0.5;
1935:   kctx->v4_m3       = 0.1;
1936:   kctx->v4_m4       = 0.5;

1938:   PetscCall(SNESParametersInitialize(snes));
1939:   *outsnes = snes;
1940:   PetscFunctionReturn(PETSC_SUCCESS);
1941: }

1943: /*@C
1944:   SNESSetFunction - Sets the function evaluation routine and function
1945:   vector for use by the `SNES` routines in solving systems of nonlinear
1946:   equations.

1948:   Logically Collective

1950:   Input Parameters:
1951: + snes - the `SNES` context
1952: . r    - vector to store function values, may be `NULL`
1953: . f    - function evaluation routine;  for calling sequence see `SNESFunctionFn`
1954: - ctx  - [optional] user-defined context for private data for the
1955:          function evaluation routine (may be `NULL`)

1957:   Level: beginner

1959: .seealso: [](ch_snes), `SNES`, `SNESGetFunction()`, `SNESComputeFunction()`, `SNESSetJacobian()`, `SNESSetPicard()`, `SNESFunctionFn`
1960: @*/
1961: PetscErrorCode SNESSetFunction(SNES snes, Vec r, SNESFunctionFn *f, void *ctx)
1962: {
1963:   DM dm;

1965:   PetscFunctionBegin;
1967:   if (r) {
1969:     PetscCheckSameComm(snes, 1, r, 2);
1970:     PetscCall(PetscObjectReference((PetscObject)r));
1971:     PetscCall(VecDestroy(&snes->vec_func));
1972:     snes->vec_func = r;
1973:   }
1974:   PetscCall(SNESGetDM(snes, &dm));
1975:   PetscCall(DMSNESSetFunction(dm, f, ctx));
1976:   if (f == SNESPicardComputeFunction) PetscCall(DMSNESSetMFFunction(dm, SNESPicardComputeMFFunction, ctx));
1977:   PetscFunctionReturn(PETSC_SUCCESS);
1978: }

1980: /*@C
1981:   SNESSetInitialFunction - Set an already computed function evaluation at the initial guess to be reused by `SNESSolve()`.

1983:   Logically Collective

1985:   Input Parameters:
1986: + snes - the `SNES` context
1987: - f    - vector to store function value

1989:   Level: developer

1991:   Notes:
1992:   This should not be modified during the solution procedure.

1994:   This is used extensively in the `SNESFAS` hierarchy and in nonlinear preconditioning.

1996: .seealso: [](ch_snes), `SNES`, `SNESFAS`, `SNESSetFunction()`, `SNESComputeFunction()`, `SNESSetInitialFunctionNorm()`
1997: @*/
1998: PetscErrorCode SNESSetInitialFunction(SNES snes, Vec f)
1999: {
2000:   Vec vec_func;

2002:   PetscFunctionBegin;
2005:   PetscCheckSameComm(snes, 1, f, 2);
2006:   if (snes->npcside == PC_LEFT && snes->functype == SNES_FUNCTION_PRECONDITIONED) {
2007:     snes->vec_func_init_set = PETSC_FALSE;
2008:     PetscFunctionReturn(PETSC_SUCCESS);
2009:   }
2010:   PetscCall(SNESGetFunction(snes, &vec_func, NULL, NULL));
2011:   PetscCall(VecCopy(f, vec_func));

2013:   snes->vec_func_init_set = PETSC_TRUE;
2014:   PetscFunctionReturn(PETSC_SUCCESS);
2015: }

2017: /*@
2018:   SNESSetNormSchedule - Sets the `SNESNormSchedule` used in convergence and monitoring
2019:   of the `SNES` method, when norms are computed in the solving process

2021:   Logically Collective

2023:   Input Parameters:
2024: + snes         - the `SNES` context
2025: - normschedule - the frequency of norm computation

2027:   Options Database Key:
2028: . -snes_norm_schedule <none, always, initialonly, finalonly, initialfinalonly> - set the schedule

2030:   Level: advanced

2032:   Notes:
2033:   Only certain `SNES` methods support certain `SNESNormSchedules`.  Most require evaluation
2034:   of the nonlinear function and the taking of its norm at every iteration to
2035:   even ensure convergence at all.  However, methods such as custom Gauss-Seidel methods
2036:   `SNESNGS` and the like do not require the norm of the function to be computed, and therefore
2037:   may either be monitored for convergence or not.  As these are often used as nonlinear
2038:   preconditioners, monitoring the norm of their error is not a useful enterprise within
2039:   their solution.

2041: .seealso: [](ch_snes), `SNESNormSchedule`, `SNESGetNormSchedule()`, `SNESComputeFunction()`, `VecNorm()`, `SNESSetFunction()`, `SNESSetInitialFunction()`
2042: @*/
2043: PetscErrorCode SNESSetNormSchedule(SNES snes, SNESNormSchedule normschedule)
2044: {
2045:   PetscFunctionBegin;
2047:   snes->normschedule = normschedule;
2048:   PetscFunctionReturn(PETSC_SUCCESS);
2049: }

2051: /*@
2052:   SNESGetNormSchedule - Gets the `SNESNormSchedule` used in convergence and monitoring
2053:   of the `SNES` method.

2055:   Logically Collective

2057:   Input Parameters:
2058: + snes         - the `SNES` context
2059: - normschedule - the type of the norm used

2061:   Level: advanced

2063: .seealso: [](ch_snes), `SNES`, `SNESSetNormSchedule()`, `SNESComputeFunction()`, `VecNorm()`, `SNESSetFunction()`, `SNESSetInitialFunction()`, `SNESNormSchedule`
2064: @*/
2065: PetscErrorCode SNESGetNormSchedule(SNES snes, SNESNormSchedule *normschedule)
2066: {
2067:   PetscFunctionBegin;
2069:   *normschedule = snes->normschedule;
2070:   PetscFunctionReturn(PETSC_SUCCESS);
2071: }

2073: /*@
2074:   SNESSetFunctionNorm - Sets the last computed residual norm.

2076:   Logically Collective

2078:   Input Parameters:
2079: + snes - the `SNES` context
2080: - norm - the value of the norm

2082:   Level: developer

2084: .seealso: [](ch_snes), `SNES`, `SNESGetNormSchedule()`, `SNESComputeFunction()`, `VecNorm()`, `SNESSetFunction()`, `SNESSetInitialFunction()`, `SNESNormSchedule`
2085: @*/
2086: PetscErrorCode SNESSetFunctionNorm(SNES snes, PetscReal norm)
2087: {
2088:   PetscFunctionBegin;
2090:   snes->norm = norm;
2091:   PetscFunctionReturn(PETSC_SUCCESS);
2092: }

2094: /*@
2095:   SNESGetFunctionNorm - Gets the last computed norm of the residual

2097:   Not Collective

2099:   Input Parameter:
2100: . snes - the `SNES` context

2102:   Output Parameter:
2103: . norm - the last computed residual norm

2105:   Level: developer

2107: .seealso: [](ch_snes), `SNES`, `SNESSetNormSchedule()`, `SNESComputeFunction()`, `VecNorm()`, `SNESSetFunction()`, `SNESSetInitialFunction()`, `SNESNormSchedule`
2108: @*/
2109: PetscErrorCode SNESGetFunctionNorm(SNES snes, PetscReal *norm)
2110: {
2111:   PetscFunctionBegin;
2113:   PetscAssertPointer(norm, 2);
2114:   *norm = snes->norm;
2115:   PetscFunctionReturn(PETSC_SUCCESS);
2116: }

2118: /*@
2119:   SNESGetUpdateNorm - Gets the last computed norm of the solution update

2121:   Not Collective

2123:   Input Parameter:
2124: . snes - the `SNES` context

2126:   Output Parameter:
2127: . ynorm - the last computed update norm

2129:   Level: developer

2131:   Note:
2132:   The new solution is the current solution plus the update, so this norm is an indication of the size of the update

2134: .seealso: [](ch_snes), `SNES`, `SNESSetNormSchedule()`, `SNESComputeFunction()`, `SNESGetFunctionNorm()`
2135: @*/
2136: PetscErrorCode SNESGetUpdateNorm(SNES snes, PetscReal *ynorm)
2137: {
2138:   PetscFunctionBegin;
2140:   PetscAssertPointer(ynorm, 2);
2141:   *ynorm = snes->ynorm;
2142:   PetscFunctionReturn(PETSC_SUCCESS);
2143: }

2145: /*@
2146:   SNESGetSolutionNorm - Gets the last computed norm of the solution

2148:   Not Collective

2150:   Input Parameter:
2151: . snes - the `SNES` context

2153:   Output Parameter:
2154: . xnorm - the last computed solution norm

2156:   Level: developer

2158: .seealso: [](ch_snes), `SNES`, `SNESSetNormSchedule()`, `SNESComputeFunction()`, `SNESGetFunctionNorm()`, `SNESGetUpdateNorm()`
2159: @*/
2160: PetscErrorCode SNESGetSolutionNorm(SNES snes, PetscReal *xnorm)
2161: {
2162:   PetscFunctionBegin;
2164:   PetscAssertPointer(xnorm, 2);
2165:   *xnorm = snes->xnorm;
2166:   PetscFunctionReturn(PETSC_SUCCESS);
2167: }

2169: /*@
2170:   SNESSetFunctionType - Sets the `SNESFunctionType`
2171:   of the `SNES` method.

2173:   Logically Collective

2175:   Input Parameters:
2176: + snes - the `SNES` context
2177: - type - the function type

2179:   Level: developer

2181:   Values of the function type\:
2182: +  `SNES_FUNCTION_DEFAULT`          - the default for the given `SNESType`
2183: .  `SNES_FUNCTION_UNPRECONDITIONED` - an unpreconditioned function evaluation (this is the function provided with `SNESSetFunction()`
2184: -  `SNES_FUNCTION_PRECONDITIONED`   - a transformation of the function provided with `SNESSetFunction()`

2186:   Note:
2187:   Different `SNESType`s use this value in different ways

2189: .seealso: [](ch_snes), `SNES`, `SNESFunctionType`, `SNESGetNormSchedule()`, `SNESComputeFunction()`, `VecNorm()`, `SNESSetFunction()`, `SNESSetInitialFunction()`, `SNESNormSchedule`
2190: @*/
2191: PetscErrorCode SNESSetFunctionType(SNES snes, SNESFunctionType type)
2192: {
2193:   PetscFunctionBegin;
2195:   snes->functype = type;
2196:   PetscFunctionReturn(PETSC_SUCCESS);
2197: }

2199: /*@
2200:   SNESGetFunctionType - Gets the `SNESFunctionType` used in convergence and monitoring set with `SNESSetFunctionType()`
2201:   of the SNES method.

2203:   Logically Collective

2205:   Input Parameters:
2206: + snes - the `SNES` context
2207: - type - the type of the function evaluation, see `SNESSetFunctionType()`

2209:   Level: advanced

2211: .seealso: [](ch_snes), `SNESSetFunctionType()`, `SNESFunctionType`, `SNESSetNormSchedule()`, `SNESComputeFunction()`, `VecNorm()`, `SNESSetFunction()`, `SNESSetInitialFunction()`, `SNESNormSchedule`
2212: @*/
2213: PetscErrorCode SNESGetFunctionType(SNES snes, SNESFunctionType *type)
2214: {
2215:   PetscFunctionBegin;
2217:   *type = snes->functype;
2218:   PetscFunctionReturn(PETSC_SUCCESS);
2219: }

2221: /*@C
2222:   SNESSetNGS - Sets the user nonlinear Gauss-Seidel routine for
2223:   use with composed nonlinear solvers.

2225:   Input Parameters:
2226: + snes - the `SNES` context, usually of the `SNESType` `SNESNGS`
2227: . f    - function evaluation routine to apply Gauss-Seidel, see `SNESNGSFn` for calling sequence
2228: - ctx  - [optional] user-defined context for private data for the smoother evaluation routine (may be `NULL`)

2230:   Level: intermediate

2232:   Note:
2233:   The `SNESNGS` routines are used by the composed nonlinear solver to generate
2234:   a problem appropriate update to the solution, particularly `SNESFAS`.

2236: .seealso: [](ch_snes), `SNESNGS`, `SNESGetNGS()`, `SNESNCG`, `SNESGetFunction()`, `SNESComputeNGS()`, `SNESNGSFn`
2237: @*/
2238: PetscErrorCode SNESSetNGS(SNES snes, SNESNGSFn *f, void *ctx)
2239: {
2240:   DM dm;

2242:   PetscFunctionBegin;
2244:   PetscCall(SNESGetDM(snes, &dm));
2245:   PetscCall(DMSNESSetNGS(dm, f, ctx));
2246:   PetscFunctionReturn(PETSC_SUCCESS);
2247: }

2249: /*
2250:      This is used for -snes_mf_operator; it uses a duplicate of snes->jacobian_pre because snes->jacobian_pre cannot be
2251:    changed during the KSPSolve()
2252: */
2253: PetscErrorCode SNESPicardComputeMFFunction(SNES snes, Vec x, Vec f, void *ctx)
2254: {
2255:   DM     dm;
2256:   DMSNES sdm;

2258:   PetscFunctionBegin;
2259:   PetscCall(SNESGetDM(snes, &dm));
2260:   PetscCall(DMGetDMSNES(dm, &sdm));
2261:   /*  A(x)*x - b(x) */
2262:   if (sdm->ops->computepfunction) {
2263:     PetscCallBack("SNES Picard callback function", (*sdm->ops->computepfunction)(snes, x, f, sdm->pctx));
2264:     PetscCall(VecScale(f, -1.0));
2265:     /* Cannot share nonzero pattern because of the possible use of SNESComputeJacobianDefault() */
2266:     if (!snes->picard) PetscCall(MatDuplicate(snes->jacobian_pre, MAT_DO_NOT_COPY_VALUES, &snes->picard));
2267:     PetscCallBack("SNES Picard callback Jacobian", (*sdm->ops->computepjacobian)(snes, x, snes->picard, snes->picard, sdm->pctx));
2268:     PetscCall(MatMultAdd(snes->picard, x, f, f));
2269:   } else {
2270:     PetscCallBack("SNES Picard callback Jacobian", (*sdm->ops->computepjacobian)(snes, x, snes->picard, snes->picard, sdm->pctx));
2271:     PetscCall(MatMult(snes->picard, x, f));
2272:   }
2273:   PetscFunctionReturn(PETSC_SUCCESS);
2274: }

2276: PetscErrorCode SNESPicardComputeFunction(SNES snes, Vec x, Vec f, void *ctx)
2277: {
2278:   DM     dm;
2279:   DMSNES sdm;

2281:   PetscFunctionBegin;
2282:   PetscCall(SNESGetDM(snes, &dm));
2283:   PetscCall(DMGetDMSNES(dm, &sdm));
2284:   /*  A(x)*x - b(x) */
2285:   if (sdm->ops->computepfunction) {
2286:     PetscCallBack("SNES Picard callback function", (*sdm->ops->computepfunction)(snes, x, f, sdm->pctx));
2287:     PetscCall(VecScale(f, -1.0));
2288:     PetscCallBack("SNES Picard callback Jacobian", (*sdm->ops->computepjacobian)(snes, x, snes->jacobian, snes->jacobian_pre, sdm->pctx));
2289:     PetscCall(MatMultAdd(snes->jacobian_pre, x, f, f));
2290:   } else {
2291:     PetscCallBack("SNES Picard callback Jacobian", (*sdm->ops->computepjacobian)(snes, x, snes->jacobian, snes->jacobian_pre, sdm->pctx));
2292:     PetscCall(MatMult(snes->jacobian_pre, x, f));
2293:   }
2294:   PetscFunctionReturn(PETSC_SUCCESS);
2295: }

2297: PetscErrorCode SNESPicardComputeJacobian(SNES snes, Vec x1, Mat J, Mat B, void *ctx)
2298: {
2299:   PetscFunctionBegin;
2300:   /* the jacobian matrix should be pre-filled in SNESPicardComputeFunction */
2301:   /* must assembly if matrix-free to get the last SNES solution */
2302:   PetscCall(MatAssemblyBegin(J, MAT_FINAL_ASSEMBLY));
2303:   PetscCall(MatAssemblyEnd(J, MAT_FINAL_ASSEMBLY));
2304:   PetscFunctionReturn(PETSC_SUCCESS);
2305: }

2307: /*@C
2308:   SNESSetPicard - Use `SNES` to solve the system $A(x) x = bp(x) + b $ via a Picard type iteration (Picard linearization)

2310:   Logically Collective

2312:   Input Parameters:
2313: + snes - the `SNES` context
2314: . r    - vector to store function values, may be `NULL`
2315: . bp   - function evaluation routine, may be `NULL`, for the calling sequence see `SNESFunctionFn`
2316: . Amat - matrix with which $A(x) x - bp(x) - b$ is to be computed
2317: . Pmat - matrix from which preconditioner is computed (usually the same as `Amat`)
2318: . J    - function to compute matrix values, for the calling sequence see `SNESJacobianFn`
2319: - ctx  - [optional] user-defined context for private data for the function evaluation routine (may be `NULL`)

2321:   Level: intermediate

2323:   Notes:
2324:   It is often better to provide the nonlinear function $F()$ and some approximation to its Jacobian directly and use
2325:   an approximate Newton solver. This interface is provided to allow porting/testing a previous Picard based code in PETSc before converting it to approximate Newton.

2327:   One can call `SNESSetPicard()` or `SNESSetFunction()` (and possibly `SNESSetJacobian()`) but cannot call both

2329:   Solves the equation $A(x) x = bp(x) - b$ via the defect correction algorithm $A(x^{n}) (x^{n+1} - x^{n}) = bp(x^{n}) + b - A(x^{n})x^{n}$.
2330:   When an exact solver is used this corresponds to the "classic" Picard $A(x^{n}) x^{n+1} = bp(x^{n}) + b$ iteration.

2332:   Run with `-snes_mf_operator` to solve the system with Newton's method using $A(x^{n})$ to construct the preconditioner.

2334:   We implement the defect correction form of the Picard iteration because it converges much more generally when inexact linear solvers are used then
2335:   the direct Picard iteration $A(x^n) x^{n+1} = bp(x^n) + b$

2337:   There is some controversity over the definition of a Picard iteration for nonlinear systems but almost everyone agrees that it involves a linear solve and some
2338:   believe it is the iteration  $A(x^{n}) x^{n+1} = b(x^{n})$ hence we use the name Picard. If anyone has an authoritative  reference that defines the Picard iteration
2339:   different please contact us at petsc-dev@mcs.anl.gov and we'll have an entirely new argument \:-).

2341:   When used with `-snes_mf_operator` this will run matrix-free Newton's method where the matrix-vector product is of the true Jacobian of $A(x)x - bp(x) - b$ and
2342:   $A(x^{n})$ is used to build the preconditioner

2344:   When used with `-snes_fd` this will compute the true Jacobian (very slowly one column at a time) and thus represent Newton's method.

2346:   When used with `-snes_fd_coloring` this will compute the Jacobian via coloring and thus represent a faster implementation of Newton's method. But the
2347:   the nonzero structure of the Jacobian is, in general larger than that of the Picard matrix $A$ so you must provide in $A$ the needed nonzero structure for the correct
2348:   coloring. When using `DMDA` this may mean creating the matrix $A$ with `DMCreateMatrix()` using a wider stencil than strictly needed for $A$ or with a `DMDA_STENCIL_BOX`.
2349:   See the comment in src/snes/tutorials/ex15.c.

2351: .seealso: [](ch_snes), `SNES`, `SNESGetFunction()`, `SNESSetFunction()`, `SNESComputeFunction()`, `SNESSetJacobian()`, `SNESGetPicard()`, `SNESLineSearchPreCheckPicard()`,
2352:           `SNESFunctionFn`, `SNESJacobianFn`
2353: @*/
2354: PetscErrorCode SNESSetPicard(SNES snes, Vec r, SNESFunctionFn *bp, Mat Amat, Mat Pmat, SNESJacobianFn *J, void *ctx)
2355: {
2356:   DM dm;

2358:   PetscFunctionBegin;
2360:   PetscCall(SNESGetDM(snes, &dm));
2361:   PetscCall(DMSNESSetPicard(dm, bp, J, ctx));
2362:   PetscCall(DMSNESSetMFFunction(dm, SNESPicardComputeMFFunction, ctx));
2363:   PetscCall(SNESSetFunction(snes, r, SNESPicardComputeFunction, ctx));
2364:   PetscCall(SNESSetJacobian(snes, Amat, Pmat, SNESPicardComputeJacobian, ctx));
2365:   PetscFunctionReturn(PETSC_SUCCESS);
2366: }

2368: /*@C
2369:   SNESGetPicard - Returns the context for the Picard iteration

2371:   Not Collective, but `Vec` is parallel if `SNES` is parallel. Collective if `Vec` is requested, but has not been created yet.

2373:   Input Parameter:
2374: . snes - the `SNES` context

2376:   Output Parameters:
2377: + r    - the function (or `NULL`)
2378: . f    - the function (or `NULL`);  for calling sequence see `SNESFunctionFn`
2379: . Amat - the matrix used to defined the operation A(x) x - b(x) (or `NULL`)
2380: . Pmat - the matrix from which the preconditioner will be constructed (or `NULL`)
2381: . J    - the function for matrix evaluation (or `NULL`);  for calling sequence see `SNESJacobianFn`
2382: - ctx  - the function context (or `NULL`)

2384:   Level: advanced

2386: .seealso: [](ch_snes), `SNESSetFunction()`, `SNESSetPicard()`, `SNESGetFunction()`, `SNESGetJacobian()`, `SNESGetDM()`, `SNESFunctionFn`, `SNESJacobianFn`
2387: @*/
2388: PetscErrorCode SNESGetPicard(SNES snes, Vec *r, SNESFunctionFn **f, Mat *Amat, Mat *Pmat, SNESJacobianFn **J, void **ctx)
2389: {
2390:   DM dm;

2392:   PetscFunctionBegin;
2394:   PetscCall(SNESGetFunction(snes, r, NULL, NULL));
2395:   PetscCall(SNESGetJacobian(snes, Amat, Pmat, NULL, NULL));
2396:   PetscCall(SNESGetDM(snes, &dm));
2397:   PetscCall(DMSNESGetPicard(dm, f, J, ctx));
2398:   PetscFunctionReturn(PETSC_SUCCESS);
2399: }

2401: /*@C
2402:   SNESSetComputeInitialGuess - Sets a routine used to compute an initial guess for the nonlinear problem

2404:   Logically Collective

2406:   Input Parameters:
2407: + snes - the `SNES` context
2408: . func - function evaluation routine, see `SNESInitialGuessFn` for the calling sequence
2409: - ctx  - [optional] user-defined context for private data for the
2410:          function evaluation routine (may be `NULL`)

2412:   Level: intermediate

2414: .seealso: [](ch_snes), `SNES`, `SNESSolve()`, `SNESSetFunction()`, `SNESGetFunction()`, `SNESComputeFunction()`, `SNESSetJacobian()`, `SNESInitialGuessFn`
2415: @*/
2416: PetscErrorCode SNESSetComputeInitialGuess(SNES snes, SNESInitialGuessFn *func, void *ctx)
2417: {
2418:   PetscFunctionBegin;
2420:   if (func) snes->ops->computeinitialguess = func;
2421:   if (ctx) snes->initialguessP = ctx;
2422:   PetscFunctionReturn(PETSC_SUCCESS);
2423: }

2425: /*@C
2426:   SNESGetRhs - Gets the vector for solving F(x) = `rhs`. If `rhs` is not set
2427:   it assumes a zero right-hand side.

2429:   Logically Collective

2431:   Input Parameter:
2432: . snes - the `SNES` context

2434:   Output Parameter:
2435: . rhs - the right-hand side vector or `NULL` if there is no right-hand side vector

2437:   Level: intermediate

2439: .seealso: [](ch_snes), `SNES`, `SNESGetSolution()`, `SNESGetFunction()`, `SNESComputeFunction()`, `SNESSetJacobian()`, `SNESSetFunction()`
2440: @*/
2441: PetscErrorCode SNESGetRhs(SNES snes, Vec *rhs)
2442: {
2443:   PetscFunctionBegin;
2445:   PetscAssertPointer(rhs, 2);
2446:   *rhs = snes->vec_rhs;
2447:   PetscFunctionReturn(PETSC_SUCCESS);
2448: }

2450: /*@
2451:   SNESComputeFunction - Calls the function that has been set with `SNESSetFunction()`.

2453:   Collective

2455:   Input Parameters:
2456: + snes - the `SNES` context
2457: - x    - input vector

2459:   Output Parameter:
2460: . y - function vector, as set by `SNESSetFunction()`

2462:   Level: developer

2464:   Notes:
2465:   `SNESComputeFunction()` is typically used within nonlinear solvers
2466:   implementations, so users would not generally call this routine themselves.

2468:   When solving for $F(x) = b$, this routine computes $y = F(x) - b$.

2470: .seealso: [](ch_snes), `SNES`, `SNESSetFunction()`, `SNESGetFunction()`, `SNESComputeMFFunction()`
2471: @*/
2472: PetscErrorCode SNESComputeFunction(SNES snes, Vec x, Vec y)
2473: {
2474:   DM     dm;
2475:   DMSNES sdm;

2477:   PetscFunctionBegin;
2481:   PetscCheckSameComm(snes, 1, x, 2);
2482:   PetscCheckSameComm(snes, 1, y, 3);
2483:   PetscCall(VecValidValues_Internal(x, 2, PETSC_TRUE));

2485:   PetscCall(SNESGetDM(snes, &dm));
2486:   PetscCall(DMGetDMSNES(dm, &sdm));
2487:   PetscCheck(sdm->ops->computefunction || snes->vec_rhs, PETSC_COMM_SELF, PETSC_ERR_ARG_WRONGSTATE, "Must call SNESSetFunction() or SNESSetDM() before SNESComputeFunction(), likely called from SNESSolve().");
2488:   if (sdm->ops->computefunction) {
2489:     if (sdm->ops->computefunction != SNESObjectiveComputeFunctionDefaultFD) PetscCall(PetscLogEventBegin(SNES_FunctionEval, snes, x, y, 0));
2490:     PetscCall(VecLockReadPush(x));
2491:     /* ensure domainerror is false prior to computefunction evaluation (may not have been reset) */
2492:     snes->domainerror = PETSC_FALSE;
2493:     {
2494:       void           *ctx;
2495:       SNESFunctionFn *computefunction;
2496:       PetscCall(DMSNESGetFunction(dm, &computefunction, &ctx));
2497:       PetscCallBack("SNES callback function", (*computefunction)(snes, x, y, ctx));
2498:     }
2499:     PetscCall(VecLockReadPop(x));
2500:     if (sdm->ops->computefunction != SNESObjectiveComputeFunctionDefaultFD) PetscCall(PetscLogEventEnd(SNES_FunctionEval, snes, x, y, 0));
2501:   } else /* if (snes->vec_rhs) */ {
2502:     PetscCall(MatMult(snes->jacobian, x, y));
2503:   }
2504:   if (snes->vec_rhs) PetscCall(VecAXPY(y, -1.0, snes->vec_rhs));
2505:   snes->nfuncs++;
2506:   /*
2507:      domainerror might not be set on all processes; so we tag vector locally with Inf and the next inner product or norm will
2508:      propagate the value to all processes
2509:   */
2510:   PetscCall(VecFlag(y, snes->domainerror));
2511:   PetscFunctionReturn(PETSC_SUCCESS);
2512: }

2514: /*@
2515:   SNESComputeMFFunction - Calls the function that has been set with `DMSNESSetMFFunction()`.

2517:   Collective

2519:   Input Parameters:
2520: + snes - the `SNES` context
2521: - x    - input vector

2523:   Output Parameter:
2524: . y - output vector

2526:   Level: developer

2528:   Notes:
2529:   `SNESComputeMFFunction()` is used within the matrix-vector products called by the matrix created with `MatCreateSNESMF()`
2530:   so users would not generally call this routine themselves.

2532:   Since this function is intended for use with finite differencing it does not subtract the right-hand side vector provided with `SNESSolve()`
2533:   while `SNESComputeFunction()` does. As such, this routine cannot be used with  `MatMFFDSetBase()` with a provided F function value even if it applies the
2534:   same function as `SNESComputeFunction()` if a `SNESSolve()` right-hand side vector is use because the two functions difference would include this right hand side function.

2536: .seealso: [](ch_snes), `SNES`, `SNESSetFunction()`, `SNESGetFunction()`, `SNESComputeFunction()`, `MatCreateSNESMF()`, `DMSNESSetMFFunction()`
2537: @*/
2538: PetscErrorCode SNESComputeMFFunction(SNES snes, Vec x, Vec y)
2539: {
2540:   DM     dm;
2541:   DMSNES sdm;

2543:   PetscFunctionBegin;
2547:   PetscCheckSameComm(snes, 1, x, 2);
2548:   PetscCheckSameComm(snes, 1, y, 3);
2549:   PetscCall(VecValidValues_Internal(x, 2, PETSC_TRUE));

2551:   PetscCall(SNESGetDM(snes, &dm));
2552:   PetscCall(DMGetDMSNES(dm, &sdm));
2553:   PetscCall(PetscLogEventBegin(SNES_FunctionEval, snes, x, y, 0));
2554:   PetscCall(VecLockReadPush(x));
2555:   /* ensure domainerror is false prior to computefunction evaluation (may not have been reset) */
2556:   snes->domainerror = PETSC_FALSE;
2557:   PetscCallBack("SNES callback function", (*sdm->ops->computemffunction)(snes, x, y, sdm->mffunctionctx));
2558:   PetscCall(VecLockReadPop(x));
2559:   PetscCall(PetscLogEventEnd(SNES_FunctionEval, snes, x, y, 0));
2560:   snes->nfuncs++;
2561:   /*
2562:      domainerror might not be set on all processes; so we tag vector locally with Inf and the next inner product or norm will
2563:      propagate the value to all processes
2564:   */
2565:   PetscCall(VecFlag(y, snes->domainerror));
2566:   PetscFunctionReturn(PETSC_SUCCESS);
2567: }

2569: /*@
2570:   SNESComputeNGS - Calls the Gauss-Seidel function that has been set with `SNESSetNGS()`.

2572:   Collective

2574:   Input Parameters:
2575: + snes - the `SNES` context
2576: . x    - input vector
2577: - b    - rhs vector

2579:   Output Parameter:
2580: . x - new solution vector

2582:   Level: developer

2584:   Note:
2585:   `SNESComputeNGS()` is typically used within composed nonlinear solver
2586:   implementations, so most users would not generally call this routine
2587:   themselves.

2589: .seealso: [](ch_snes), `SNESNGSFn`, `SNESSetNGS()`, `SNESComputeFunction()`, `SNESNGS`
2590: @*/
2591: PetscErrorCode SNESComputeNGS(SNES snes, Vec b, Vec x)
2592: {
2593:   DM     dm;
2594:   DMSNES sdm;

2596:   PetscFunctionBegin;
2600:   PetscCheckSameComm(snes, 1, x, 3);
2601:   if (b) PetscCheckSameComm(snes, 1, b, 2);
2602:   if (b) PetscCall(VecValidValues_Internal(b, 2, PETSC_TRUE));
2603:   PetscCall(PetscLogEventBegin(SNES_NGSEval, snes, x, b, 0));
2604:   PetscCall(SNESGetDM(snes, &dm));
2605:   PetscCall(DMGetDMSNES(dm, &sdm));
2606:   PetscCheck(sdm->ops->computegs, PETSC_COMM_SELF, PETSC_ERR_ARG_WRONGSTATE, "Must call SNESSetNGS() before SNESComputeNGS(), likely called from SNESSolve().");
2607:   if (b) PetscCall(VecLockReadPush(b));
2608:   PetscCallBack("SNES callback NGS", (*sdm->ops->computegs)(snes, x, b, sdm->gsctx));
2609:   if (b) PetscCall(VecLockReadPop(b));
2610:   PetscCall(PetscLogEventEnd(SNES_NGSEval, snes, x, b, 0));
2611:   PetscFunctionReturn(PETSC_SUCCESS);
2612: }

2614: static PetscErrorCode SNESComputeFunction_FD(SNES snes, Vec Xin, Vec G)
2615: {
2616:   Vec          X;
2617:   PetscScalar *g;
2618:   PetscReal    f, f2;
2619:   PetscInt     low, high, N, i;
2620:   PetscBool    flg;
2621:   PetscReal    h = .5 * PETSC_SQRT_MACHINE_EPSILON;

2623:   PetscFunctionBegin;
2624:   PetscCall(PetscOptionsGetReal(((PetscObject)snes)->options, ((PetscObject)snes)->prefix, "-snes_fd_delta", &h, &flg));
2625:   PetscCall(VecDuplicate(Xin, &X));
2626:   PetscCall(VecCopy(Xin, X));
2627:   PetscCall(VecGetSize(X, &N));
2628:   PetscCall(VecGetOwnershipRange(X, &low, &high));
2629:   PetscCall(VecSetOption(X, VEC_IGNORE_OFF_PROC_ENTRIES, PETSC_TRUE));
2630:   PetscCall(VecGetArray(G, &g));
2631:   for (i = 0; i < N; i++) {
2632:     PetscCall(VecSetValue(X, i, -h, ADD_VALUES));
2633:     PetscCall(VecAssemblyBegin(X));
2634:     PetscCall(VecAssemblyEnd(X));
2635:     PetscCall(SNESComputeObjective(snes, X, &f));
2636:     PetscCall(VecSetValue(X, i, 2.0 * h, ADD_VALUES));
2637:     PetscCall(VecAssemblyBegin(X));
2638:     PetscCall(VecAssemblyEnd(X));
2639:     PetscCall(SNESComputeObjective(snes, X, &f2));
2640:     PetscCall(VecSetValue(X, i, -h, ADD_VALUES));
2641:     PetscCall(VecAssemblyBegin(X));
2642:     PetscCall(VecAssemblyEnd(X));
2643:     if (i >= low && i < high) g[i - low] = (f2 - f) / (2.0 * h);
2644:   }
2645:   PetscCall(VecRestoreArray(G, &g));
2646:   PetscCall(VecDestroy(&X));
2647:   PetscFunctionReturn(PETSC_SUCCESS);
2648: }

2650: /*@
2651:   SNESTestFunction - Computes the difference between the computed and finite-difference functions

2653:   Collective

2655:   Input Parameter:
2656: . snes - the `SNES` context

2658:   Options Database Keys:
2659: + -snes_test_function      - compare the user provided function with one compute via finite differences to check for errors.
2660: - -snes_test_function_view - display the user provided function, the finite difference function and the difference

2662:   Level: developer

2664: .seealso: [](ch_snes), `SNESTestJacobian()`, `SNESSetFunction()`, `SNESComputeFunction()`
2665: @*/
2666: PetscErrorCode SNESTestFunction(SNES snes)
2667: {
2668:   Vec               x, g1, g2, g3;
2669:   PetscBool         complete_print = PETSC_FALSE;
2670:   PetscReal         hcnorm, fdnorm, hcmax, fdmax, diffmax, diffnorm;
2671:   PetscScalar       dot;
2672:   MPI_Comm          comm;
2673:   PetscViewer       viewer, mviewer;
2674:   PetscViewerFormat format;
2675:   PetscInt          tabs;
2676:   static PetscBool  directionsprinted = PETSC_FALSE;
2677:   SNESObjectiveFn  *objective;

2679:   PetscFunctionBegin;
2680:   PetscCall(SNESGetObjective(snes, &objective, NULL));
2681:   if (!objective) PetscFunctionReturn(PETSC_SUCCESS);

2683:   PetscObjectOptionsBegin((PetscObject)snes);
2684:   PetscCall(PetscOptionsViewer("-snes_test_function_view", "View difference between hand-coded and finite difference function element entries", "None", &mviewer, &format, &complete_print));
2685:   PetscOptionsEnd();

2687:   PetscCall(PetscObjectGetComm((PetscObject)snes, &comm));
2688:   PetscCall(PetscViewerASCIIGetStdout(comm, &viewer));
2689:   PetscCall(PetscViewerASCIIGetTab(viewer, &tabs));
2690:   PetscCall(PetscViewerASCIISetTab(viewer, ((PetscObject)snes)->tablevel));
2691:   PetscCall(PetscViewerASCIIPrintf(viewer, "  ---------- Testing Function -------------\n"));
2692:   if (!complete_print && !directionsprinted) {
2693:     PetscCall(PetscViewerASCIIPrintf(viewer, "  Run with -snes_test_function_view and optionally -snes_test_function <threshold> to show difference\n"));
2694:     PetscCall(PetscViewerASCIIPrintf(viewer, "    of hand-coded and finite difference function entries greater than <threshold>.\n"));
2695:   }
2696:   if (!directionsprinted) {
2697:     PetscCall(PetscViewerASCIIPrintf(viewer, "  Testing hand-coded Function, if (for double precision runs) ||F - Ffd||/||F|| is\n"));
2698:     PetscCall(PetscViewerASCIIPrintf(viewer, "    O(1.e-8), the hand-coded Function is probably correct.\n"));
2699:     directionsprinted = PETSC_TRUE;
2700:   }
2701:   if (complete_print) PetscCall(PetscViewerPushFormat(mviewer, format));

2703:   PetscCall(SNESGetSolution(snes, &x));
2704:   PetscCall(VecDuplicate(x, &g1));
2705:   PetscCall(VecDuplicate(x, &g2));
2706:   PetscCall(VecDuplicate(x, &g3));
2707:   PetscCall(SNESComputeFunction(snes, x, g1));
2708:   PetscCall(SNESComputeFunction_FD(snes, x, g2));

2710:   PetscCall(VecNorm(g2, NORM_2, &fdnorm));
2711:   PetscCall(VecNorm(g1, NORM_2, &hcnorm));
2712:   PetscCall(VecNorm(g2, NORM_INFINITY, &fdmax));
2713:   PetscCall(VecNorm(g1, NORM_INFINITY, &hcmax));
2714:   PetscCall(VecDot(g1, g2, &dot));
2715:   PetscCall(VecCopy(g1, g3));
2716:   PetscCall(VecAXPY(g3, -1.0, g2));
2717:   PetscCall(VecNorm(g3, NORM_2, &diffnorm));
2718:   PetscCall(VecNorm(g3, NORM_INFINITY, &diffmax));
2719:   PetscCall(PetscViewerASCIIPrintf(viewer, "  ||Ffd|| %g, ||F|| = %g, angle cosine = (Ffd'F)/||Ffd||||F|| = %g\n", (double)fdnorm, (double)hcnorm, (double)(PetscRealPart(dot) / (fdnorm * hcnorm))));
2720:   PetscCall(PetscViewerASCIIPrintf(viewer, "  2-norm ||F - Ffd||/||F|| = %g, ||F - Ffd|| = %g\n", (double)(diffnorm / PetscMax(hcnorm, fdnorm)), (double)diffnorm));
2721:   PetscCall(PetscViewerASCIIPrintf(viewer, "  max-norm ||F - Ffd||/||F|| = %g, ||F - Ffd|| = %g\n", (double)(diffmax / PetscMax(hcmax, fdmax)), (double)diffmax));

2723:   if (complete_print) {
2724:     PetscCall(PetscViewerASCIIPrintf(viewer, "  Hand-coded function ----------\n"));
2725:     PetscCall(VecView(g1, mviewer));
2726:     PetscCall(PetscViewerASCIIPrintf(viewer, "  Finite difference function ----------\n"));
2727:     PetscCall(VecView(g2, mviewer));
2728:     PetscCall(PetscViewerASCIIPrintf(viewer, "  Hand-coded minus finite-difference function ----------\n"));
2729:     PetscCall(VecView(g3, mviewer));
2730:   }
2731:   PetscCall(VecDestroy(&g1));
2732:   PetscCall(VecDestroy(&g2));
2733:   PetscCall(VecDestroy(&g3));

2735:   if (complete_print) {
2736:     PetscCall(PetscViewerPopFormat(mviewer));
2737:     PetscCall(PetscViewerDestroy(&mviewer));
2738:   }
2739:   PetscCall(PetscViewerASCIISetTab(viewer, tabs));
2740:   PetscFunctionReturn(PETSC_SUCCESS);
2741: }

2743: /*@
2744:   SNESTestJacobian - Computes the difference between the computed and finite-difference Jacobians

2746:   Collective

2748:   Input Parameter:
2749: . snes - the `SNES` context

2751:   Output Parameters:
2752: + Jnorm    - the Frobenius norm of the computed Jacobian, or `NULL`
2753: - diffNorm - the Frobenius norm of the difference of the computed and finite-difference Jacobians, or `NULL`

2755:   Options Database Keys:
2756: + -snes_test_jacobian <optional threshold> - compare the user provided Jacobian with one compute via finite differences to check for errors.  If a threshold is given, display only those entries whose difference is greater than the threshold.
2757: - -snes_test_jacobian_view                 - display the user provided Jacobian, the finite difference Jacobian and the difference

2759:   Level: developer

2761:   Note:
2762:   Directions and norms are printed to stdout if `diffNorm` is `NULL`.

2764: .seealso: [](ch_snes), `SNESTestFunction()`, `SNESSetJacobian()`, `SNESComputeJacobian()`
2765: @*/
2766: PetscErrorCode SNESTestJacobian(SNES snes, PetscReal *Jnorm, PetscReal *diffNorm)
2767: {
2768:   Mat               A, B, C, D, jacobian;
2769:   Vec               x = snes->vec_sol, f;
2770:   PetscReal         nrm, gnorm;
2771:   PetscReal         threshold = 1.e-5;
2772:   MatType           mattype;
2773:   PetscInt          m, n, M, N;
2774:   void             *functx;
2775:   PetscBool         complete_print = PETSC_FALSE, threshold_print = PETSC_FALSE, flg, istranspose;
2776:   PetscBool         silent = diffNorm != PETSC_NULLPTR ? PETSC_TRUE : PETSC_FALSE;
2777:   PetscViewer       viewer, mviewer;
2778:   MPI_Comm          comm;
2779:   PetscInt          tabs;
2780:   static PetscBool  directionsprinted = PETSC_FALSE;
2781:   PetscViewerFormat format;

2783:   PetscFunctionBegin;
2784:   PetscObjectOptionsBegin((PetscObject)snes);
2785:   PetscCall(PetscOptionsReal("-snes_test_jacobian", "Threshold for element difference between hand-coded and finite difference being meaningful", "None", threshold, &threshold, NULL));
2786:   PetscCall(PetscOptionsDeprecated("-snes_test_jacobian_display", "-snes_test_jacobian_view", "3.13", NULL));
2787:   PetscCall(PetscOptionsViewer("-snes_test_jacobian_view", "View difference between hand-coded and finite difference Jacobians element entries", "None", &mviewer, &format, &complete_print));
2788:   PetscCall(PetscOptionsDeprecated("-snes_test_jacobian_display_threshold", "-snes_test_jacobian", "3.13", "-snes_test_jacobian accepts an optional threshold (since v3.10)"));
2789:   PetscCall(PetscOptionsReal("-snes_test_jacobian_display_threshold", "Display difference between hand-coded and finite difference Jacobians which exceed input threshold", "None", threshold, &threshold, &threshold_print));
2790:   PetscOptionsEnd();

2792:   PetscCall(PetscObjectGetComm((PetscObject)snes, &comm));
2793:   PetscCall(PetscViewerASCIIGetStdout(comm, &viewer));
2794:   PetscCall(PetscViewerASCIIGetTab(viewer, &tabs));
2795:   PetscCall(PetscViewerASCIISetTab(viewer, ((PetscObject)snes)->tablevel));
2796:   if (!silent) PetscCall(PetscViewerASCIIPrintf(viewer, "  ---------- Testing Jacobian -------------\n"));
2797:   if (!complete_print && !silent && !directionsprinted) {
2798:     PetscCall(PetscViewerASCIIPrintf(viewer, "  Run with -snes_test_jacobian_view and optionally -snes_test_jacobian <threshold> to show difference\n"));
2799:     PetscCall(PetscViewerASCIIPrintf(viewer, "    of hand-coded and finite difference Jacobian entries greater than <threshold>.\n"));
2800:   }
2801:   if (!directionsprinted && !silent) {
2802:     PetscCall(PetscViewerASCIIPrintf(viewer, "  Testing hand-coded Jacobian, if (for double precision runs) ||J - Jfd||_F/||J||_F is\n"));
2803:     PetscCall(PetscViewerASCIIPrintf(viewer, "    O(1.e-8), the hand-coded Jacobian is probably correct.\n"));
2804:     directionsprinted = PETSC_TRUE;
2805:   }
2806:   if (complete_print) PetscCall(PetscViewerPushFormat(mviewer, format));

2808:   PetscCall(PetscObjectTypeCompare((PetscObject)snes->jacobian, MATMFFD, &flg));
2809:   if (!flg) jacobian = snes->jacobian;
2810:   else jacobian = snes->jacobian_pre;

2812:   if (!x) PetscCall(MatCreateVecs(jacobian, &x, NULL));
2813:   else PetscCall(PetscObjectReference((PetscObject)x));
2814:   PetscCall(VecDuplicate(x, &f));

2816:   /* evaluate the function at this point because SNESComputeJacobianDefault() assumes that the function has been evaluated and put into snes->vec_func */
2817:   PetscCall(SNESComputeFunction(snes, x, f));
2818:   PetscCall(VecDestroy(&f));
2819:   PetscCall(PetscObjectTypeCompare((PetscObject)snes, SNESKSPTRANSPOSEONLY, &istranspose));
2820:   while (jacobian) {
2821:     Mat JT = NULL, Jsave = NULL;

2823:     if (istranspose) {
2824:       PetscCall(MatCreateTranspose(jacobian, &JT));
2825:       Jsave    = jacobian;
2826:       jacobian = JT;
2827:     }
2828:     PetscCall(PetscObjectBaseTypeCompareAny((PetscObject)jacobian, &flg, MATSEQAIJ, MATMPIAIJ, MATSEQDENSE, MATMPIDENSE, MATSEQBAIJ, MATMPIBAIJ, MATSEQSBAIJ, MATMPISBAIJ, ""));
2829:     if (flg) {
2830:       A = jacobian;
2831:       PetscCall(PetscObjectReference((PetscObject)A));
2832:     } else {
2833:       PetscCall(MatComputeOperator(jacobian, MATAIJ, &A));
2834:     }

2836:     PetscCall(MatGetType(A, &mattype));
2837:     PetscCall(MatGetSize(A, &M, &N));
2838:     PetscCall(MatGetLocalSize(A, &m, &n));
2839:     PetscCall(MatCreate(PetscObjectComm((PetscObject)A), &B));
2840:     PetscCall(MatSetType(B, mattype));
2841:     PetscCall(MatSetSizes(B, m, n, M, N));
2842:     PetscCall(MatSetBlockSizesFromMats(B, A, A));
2843:     PetscCall(MatSetUp(B));
2844:     PetscCall(MatSetOption(B, MAT_NEW_NONZERO_ALLOCATION_ERR, PETSC_FALSE));

2846:     PetscCall(SNESGetFunction(snes, NULL, NULL, &functx));
2847:     PetscCall(SNESComputeJacobianDefault(snes, x, B, B, functx));

2849:     PetscCall(MatDuplicate(B, MAT_COPY_VALUES, &D));
2850:     PetscCall(MatAYPX(D, -1.0, A, DIFFERENT_NONZERO_PATTERN));
2851:     PetscCall(MatNorm(D, NORM_FROBENIUS, &nrm));
2852:     PetscCall(MatNorm(A, NORM_FROBENIUS, &gnorm));
2853:     PetscCall(MatDestroy(&D));
2854:     if (!gnorm) gnorm = 1; /* just in case */
2855:     if (!silent) PetscCall(PetscViewerASCIIPrintf(viewer, "  ||J - Jfd||_F/||J||_F = %g, ||J - Jfd||_F = %g\n", (double)(nrm / gnorm), (double)nrm));
2856:     if (complete_print) {
2857:       PetscCall(PetscViewerASCIIPrintf(viewer, "  Hand-coded Jacobian ----------\n"));
2858:       PetscCall(MatView(A, mviewer));
2859:       PetscCall(PetscViewerASCIIPrintf(viewer, "  Finite difference Jacobian ----------\n"));
2860:       PetscCall(MatView(B, mviewer));
2861:     }

2863:     if (threshold_print || complete_print) {
2864:       PetscInt           Istart, Iend, *ccols, bncols, cncols, j, row;
2865:       PetscScalar       *cvals;
2866:       const PetscInt    *bcols;
2867:       const PetscScalar *bvals;

2869:       PetscCall(MatCreate(PetscObjectComm((PetscObject)A), &C));
2870:       PetscCall(MatSetType(C, mattype));
2871:       PetscCall(MatSetSizes(C, m, n, M, N));
2872:       PetscCall(MatSetBlockSizesFromMats(C, A, A));
2873:       PetscCall(MatSetUp(C));
2874:       PetscCall(MatSetOption(C, MAT_NEW_NONZERO_ALLOCATION_ERR, PETSC_FALSE));

2876:       PetscCall(MatAYPX(B, -1.0, A, DIFFERENT_NONZERO_PATTERN));
2877:       PetscCall(MatGetOwnershipRange(B, &Istart, &Iend));

2879:       for (row = Istart; row < Iend; row++) {
2880:         PetscCall(MatGetRow(B, row, &bncols, &bcols, &bvals));
2881:         PetscCall(PetscMalloc2(bncols, &ccols, bncols, &cvals));
2882:         for (j = 0, cncols = 0; j < bncols; j++) {
2883:           if (PetscAbsScalar(bvals[j]) > threshold) {
2884:             ccols[cncols] = bcols[j];
2885:             cvals[cncols] = bvals[j];
2886:             cncols += 1;
2887:           }
2888:         }
2889:         if (cncols) PetscCall(MatSetValues(C, 1, &row, cncols, ccols, cvals, INSERT_VALUES));
2890:         PetscCall(MatRestoreRow(B, row, &bncols, &bcols, &bvals));
2891:         PetscCall(PetscFree2(ccols, cvals));
2892:       }
2893:       PetscCall(MatAssemblyBegin(C, MAT_FINAL_ASSEMBLY));
2894:       PetscCall(MatAssemblyEnd(C, MAT_FINAL_ASSEMBLY));
2895:       PetscCall(PetscViewerASCIIPrintf(viewer, "  Hand-coded minus finite-difference Jacobian with tolerance %g ----------\n", (double)threshold));
2896:       PetscCall(MatView(C, complete_print ? mviewer : viewer));
2897:       PetscCall(MatDestroy(&C));
2898:     }
2899:     PetscCall(MatDestroy(&A));
2900:     PetscCall(MatDestroy(&B));
2901:     PetscCall(MatDestroy(&JT));
2902:     if (Jsave) jacobian = Jsave;
2903:     if (jacobian != snes->jacobian_pre) {
2904:       jacobian = snes->jacobian_pre;
2905:       if (!silent) PetscCall(PetscViewerASCIIPrintf(viewer, "  ---------- Testing Jacobian for preconditioner -------------\n"));
2906:     } else jacobian = NULL;
2907:   }
2908:   PetscCall(VecDestroy(&x));
2909:   if (complete_print) PetscCall(PetscViewerPopFormat(mviewer));
2910:   if (mviewer) PetscCall(PetscViewerDestroy(&mviewer));
2911:   PetscCall(PetscViewerASCIISetTab(viewer, tabs));

2913:   if (Jnorm) *Jnorm = gnorm;
2914:   if (diffNorm) *diffNorm = nrm;
2915:   PetscFunctionReturn(PETSC_SUCCESS);
2916: }

2918: /*@
2919:   SNESComputeJacobian - Computes the Jacobian matrix that has been set with `SNESSetJacobian()`.

2921:   Collective

2923:   Input Parameters:
2924: + snes - the `SNES` context
2925: - X    - input vector

2927:   Output Parameters:
2928: + A - Jacobian matrix
2929: - B - optional matrix for building the preconditioner, usually the same as `A`

2931:   Options Database Keys:
2932: + -snes_lag_preconditioner <lag>           - how often to rebuild preconditioner
2933: . -snes_lag_jacobian <lag>                 - how often to rebuild Jacobian
2934: . -snes_test_jacobian <optional threshold> - compare the user provided Jacobian with one compute via finite differences to check for errors.  If a threshold is given, display only those entries whose difference is greater than the threshold.
2935: . -snes_test_jacobian_view                 - display the user provided Jacobian, the finite difference Jacobian and the difference between them to help users detect the location of errors in the user provided Jacobian
2936: . -snes_compare_explicit                   - Compare the computed Jacobian to the finite difference Jacobian and output the differences
2937: . -snes_compare_explicit_draw              - Compare the computed Jacobian to the finite difference Jacobian and draw the result
2938: . -snes_compare_explicit_contour           - Compare the computed Jacobian to the finite difference Jacobian and draw a contour plot with the result
2939: . -snes_compare_operator                   - Make the comparison options above use the operator instead of the matrix used to construct the preconditioner
2940: . -snes_compare_coloring                   - Compute the finite difference Jacobian using coloring and display norms of difference
2941: . -snes_compare_coloring_display           - Compute the finite difference Jacobian using coloring and display verbose differences
2942: . -snes_compare_coloring_threshold         - Display only those matrix entries that differ by more than a given threshold
2943: . -snes_compare_coloring_threshold_atol    - Absolute tolerance for difference in matrix entries to be displayed by `-snes_compare_coloring_threshold`
2944: . -snes_compare_coloring_threshold_rtol    - Relative tolerance for difference in matrix entries to be displayed by `-snes_compare_coloring_threshold`
2945: . -snes_compare_coloring_draw              - Compute the finite difference Jacobian using coloring and draw differences
2946: - -snes_compare_coloring_draw_contour      - Compute the finite difference Jacobian using coloring and show contours of matrices and differences

2948:   Level: developer

2950:   Note:
2951:   Most users should not need to explicitly call this routine, as it
2952:   is used internally within the nonlinear solvers.

2954:   Developer Note:
2955:   This has duplicative ways of checking the accuracy of the user provided Jacobian (see the options above). This is for historical reasons, the routine `SNESTestJacobian()` use to used
2956:   with the `SNESType` of test that has been removed.

2958: .seealso: [](ch_snes), `SNESSetJacobian()`, `KSPSetOperators()`, `MatStructure`, `SNESSetLagPreconditioner()`, `SNESSetLagJacobian()`
2959: @*/
2960: PetscErrorCode SNESComputeJacobian(SNES snes, Vec X, Mat A, Mat B)
2961: {
2962:   PetscBool flag;
2963:   DM        dm;
2964:   DMSNES    sdm;
2965:   KSP       ksp;

2967:   PetscFunctionBegin;
2970:   PetscCheckSameComm(snes, 1, X, 2);
2971:   PetscCall(VecValidValues_Internal(X, 2, PETSC_TRUE));
2972:   PetscCall(SNESGetDM(snes, &dm));
2973:   PetscCall(DMGetDMSNES(dm, &sdm));

2975:   /* make sure that MatAssemblyBegin/End() is called on A matrix if it is matrix-free */
2976:   if (snes->lagjacobian == -2) {
2977:     snes->lagjacobian = -1;

2979:     PetscCall(PetscInfo(snes, "Recomputing Jacobian/preconditioner because lag is -2 (means compute Jacobian, but then never again) \n"));
2980:   } else if (snes->lagjacobian == -1) {
2981:     PetscCall(PetscInfo(snes, "Reusing Jacobian/preconditioner because lag is -1\n"));
2982:     PetscCall(PetscObjectTypeCompare((PetscObject)A, MATMFFD, &flag));
2983:     if (flag) {
2984:       PetscCall(MatAssemblyBegin(A, MAT_FINAL_ASSEMBLY));
2985:       PetscCall(MatAssemblyEnd(A, MAT_FINAL_ASSEMBLY));
2986:     }
2987:     PetscFunctionReturn(PETSC_SUCCESS);
2988:   } else if (snes->lagjacobian > 1 && (snes->iter + snes->jac_iter) % snes->lagjacobian) {
2989:     PetscCall(PetscInfo(snes, "Reusing Jacobian/preconditioner because lag is %" PetscInt_FMT " and SNES iteration is %" PetscInt_FMT "\n", snes->lagjacobian, snes->iter));
2990:     PetscCall(PetscObjectTypeCompare((PetscObject)A, MATMFFD, &flag));
2991:     if (flag) {
2992:       PetscCall(MatAssemblyBegin(A, MAT_FINAL_ASSEMBLY));
2993:       PetscCall(MatAssemblyEnd(A, MAT_FINAL_ASSEMBLY));
2994:     }
2995:     PetscFunctionReturn(PETSC_SUCCESS);
2996:   }
2997:   if (snes->npc && snes->npcside == PC_LEFT) {
2998:     PetscCall(MatAssemblyBegin(A, MAT_FINAL_ASSEMBLY));
2999:     PetscCall(MatAssemblyEnd(A, MAT_FINAL_ASSEMBLY));
3000:     PetscFunctionReturn(PETSC_SUCCESS);
3001:   }

3003:   PetscCall(PetscLogEventBegin(SNES_JacobianEval, snes, X, A, B));
3004:   PetscCall(VecLockReadPush(X));
3005:   {
3006:     void           *ctx;
3007:     SNESJacobianFn *J;
3008:     PetscCall(DMSNESGetJacobian(dm, &J, &ctx));
3009:     PetscCallBack("SNES callback Jacobian", (*J)(snes, X, A, B, ctx));
3010:   }
3011:   PetscCall(VecLockReadPop(X));
3012:   PetscCall(PetscLogEventEnd(SNES_JacobianEval, snes, X, A, B));

3014:   /* attach latest linearization point to the matrix used to construct the preconditioner */
3015:   PetscCall(PetscObjectCompose((PetscObject)B, "__SNES_latest_X", (PetscObject)X));

3017:   /* the next line ensures that snes->ksp exists */
3018:   PetscCall(SNESGetKSP(snes, &ksp));
3019:   if (snes->lagpreconditioner == -2) {
3020:     PetscCall(PetscInfo(snes, "Rebuilding preconditioner exactly once since lag is -2\n"));
3021:     PetscCall(KSPSetReusePreconditioner(snes->ksp, PETSC_FALSE));
3022:     snes->lagpreconditioner = -1;
3023:   } else if (snes->lagpreconditioner == -1) {
3024:     PetscCall(PetscInfo(snes, "Reusing preconditioner because lag is -1\n"));
3025:     PetscCall(KSPSetReusePreconditioner(snes->ksp, PETSC_TRUE));
3026:   } else if (snes->lagpreconditioner > 1 && (snes->iter + snes->pre_iter) % snes->lagpreconditioner) {
3027:     PetscCall(PetscInfo(snes, "Reusing preconditioner because lag is %" PetscInt_FMT " and SNES iteration is %" PetscInt_FMT "\n", snes->lagpreconditioner, snes->iter));
3028:     PetscCall(KSPSetReusePreconditioner(snes->ksp, PETSC_TRUE));
3029:   } else {
3030:     PetscCall(PetscInfo(snes, "Rebuilding preconditioner\n"));
3031:     PetscCall(KSPSetReusePreconditioner(snes->ksp, PETSC_FALSE));
3032:   }

3034:   /* monkey business to allow testing Jacobians in multilevel solvers.
3035:      This is needed because the SNESTestXXX interface does not accept vectors and matrices */
3036:   {
3037:     Vec xsave            = snes->vec_sol;
3038:     Mat jacobiansave     = snes->jacobian;
3039:     Mat jacobian_presave = snes->jacobian_pre;

3041:     snes->vec_sol      = X;
3042:     snes->jacobian     = A;
3043:     snes->jacobian_pre = B;
3044:     if (snes->testFunc) PetscCall(SNESTestFunction(snes));
3045:     if (snes->testJac) PetscCall(SNESTestJacobian(snes, NULL, NULL));

3047:     snes->vec_sol      = xsave;
3048:     snes->jacobian     = jacobiansave;
3049:     snes->jacobian_pre = jacobian_presave;
3050:   }

3052:   {
3053:     PetscBool flag = PETSC_FALSE, flag_draw = PETSC_FALSE, flag_contour = PETSC_FALSE, flag_operator = PETSC_FALSE;
3054:     PetscCall(PetscOptionsCreateViewer(PetscObjectComm((PetscObject)snes), ((PetscObject)snes)->options, ((PetscObject)snes)->prefix, "-snes_compare_explicit", NULL, NULL, &flag));
3055:     PetscCall(PetscOptionsCreateViewer(PetscObjectComm((PetscObject)snes), ((PetscObject)snes)->options, ((PetscObject)snes)->prefix, "-snes_compare_explicit_draw", NULL, NULL, &flag_draw));
3056:     PetscCall(PetscOptionsCreateViewer(PetscObjectComm((PetscObject)snes), ((PetscObject)snes)->options, ((PetscObject)snes)->prefix, "-snes_compare_explicit_draw_contour", NULL, NULL, &flag_contour));
3057:     PetscCall(PetscOptionsCreateViewer(PetscObjectComm((PetscObject)snes), ((PetscObject)snes)->options, ((PetscObject)snes)->prefix, "-snes_compare_operator", NULL, NULL, &flag_operator));
3058:     if (flag || flag_draw || flag_contour) {
3059:       Mat         Bexp_mine = NULL, Bexp, FDexp;
3060:       PetscViewer vdraw, vstdout;
3061:       PetscBool   flg;
3062:       if (flag_operator) {
3063:         PetscCall(MatComputeOperator(A, MATAIJ, &Bexp_mine));
3064:         Bexp = Bexp_mine;
3065:       } else {
3066:         /* See if the matrix used to construct the preconditioner can be viewed and added directly */
3067:         PetscCall(PetscObjectBaseTypeCompareAny((PetscObject)B, &flg, MATSEQAIJ, MATMPIAIJ, MATSEQDENSE, MATMPIDENSE, MATSEQBAIJ, MATMPIBAIJ, MATSEQSBAIJ, MATMPIBAIJ, ""));
3068:         if (flg) Bexp = B;
3069:         else {
3070:           /* If the "preconditioning" matrix is itself MATSHELL or some other type without direct support */
3071:           PetscCall(MatComputeOperator(B, MATAIJ, &Bexp_mine));
3072:           Bexp = Bexp_mine;
3073:         }
3074:       }
3075:       PetscCall(MatConvert(Bexp, MATSAME, MAT_INITIAL_MATRIX, &FDexp));
3076:       PetscCall(SNESComputeJacobianDefault(snes, X, FDexp, FDexp, NULL));
3077:       PetscCall(PetscViewerASCIIGetStdout(PetscObjectComm((PetscObject)snes), &vstdout));
3078:       if (flag_draw || flag_contour) {
3079:         PetscCall(PetscViewerDrawOpen(PetscObjectComm((PetscObject)snes), NULL, "Explicit Jacobians", PETSC_DECIDE, PETSC_DECIDE, 300, 300, &vdraw));
3080:         if (flag_contour) PetscCall(PetscViewerPushFormat(vdraw, PETSC_VIEWER_DRAW_CONTOUR));
3081:       } else vdraw = NULL;
3082:       PetscCall(PetscViewerASCIIPrintf(vstdout, "Explicit %s\n", flag_operator ? "Jacobian" : "preconditioning Jacobian"));
3083:       if (flag) PetscCall(MatView(Bexp, vstdout));
3084:       if (vdraw) PetscCall(MatView(Bexp, vdraw));
3085:       PetscCall(PetscViewerASCIIPrintf(vstdout, "Finite difference Jacobian\n"));
3086:       if (flag) PetscCall(MatView(FDexp, vstdout));
3087:       if (vdraw) PetscCall(MatView(FDexp, vdraw));
3088:       PetscCall(MatAYPX(FDexp, -1.0, Bexp, SAME_NONZERO_PATTERN));
3089:       PetscCall(PetscViewerASCIIPrintf(vstdout, "User-provided matrix minus finite difference Jacobian\n"));
3090:       if (flag) PetscCall(MatView(FDexp, vstdout));
3091:       if (vdraw) { /* Always use contour for the difference */
3092:         PetscCall(PetscViewerPushFormat(vdraw, PETSC_VIEWER_DRAW_CONTOUR));
3093:         PetscCall(MatView(FDexp, vdraw));
3094:         PetscCall(PetscViewerPopFormat(vdraw));
3095:       }
3096:       if (flag_contour) PetscCall(PetscViewerPopFormat(vdraw));
3097:       PetscCall(PetscViewerDestroy(&vdraw));
3098:       PetscCall(MatDestroy(&Bexp_mine));
3099:       PetscCall(MatDestroy(&FDexp));
3100:     }
3101:   }
3102:   {
3103:     PetscBool flag = PETSC_FALSE, flag_display = PETSC_FALSE, flag_draw = PETSC_FALSE, flag_contour = PETSC_FALSE, flag_threshold = PETSC_FALSE;
3104:     PetscReal threshold_atol = PETSC_SQRT_MACHINE_EPSILON, threshold_rtol = 10 * PETSC_SQRT_MACHINE_EPSILON;
3105:     PetscCall(PetscOptionsCreateViewer(PetscObjectComm((PetscObject)snes), ((PetscObject)snes)->options, ((PetscObject)snes)->prefix, "-snes_compare_coloring", NULL, NULL, &flag));
3106:     PetscCall(PetscOptionsCreateViewer(PetscObjectComm((PetscObject)snes), ((PetscObject)snes)->options, ((PetscObject)snes)->prefix, "-snes_compare_coloring_display", NULL, NULL, &flag_display));
3107:     PetscCall(PetscOptionsCreateViewer(PetscObjectComm((PetscObject)snes), ((PetscObject)snes)->options, ((PetscObject)snes)->prefix, "-snes_compare_coloring_draw", NULL, NULL, &flag_draw));
3108:     PetscCall(PetscOptionsCreateViewer(PetscObjectComm((PetscObject)snes), ((PetscObject)snes)->options, ((PetscObject)snes)->prefix, "-snes_compare_coloring_draw_contour", NULL, NULL, &flag_contour));
3109:     PetscCall(PetscOptionsCreateViewer(PetscObjectComm((PetscObject)snes), ((PetscObject)snes)->options, ((PetscObject)snes)->prefix, "-snes_compare_coloring_threshold", NULL, NULL, &flag_threshold));
3110:     if (flag_threshold) {
3111:       PetscCall(PetscOptionsGetReal(((PetscObject)snes)->options, ((PetscObject)snes)->prefix, "-snes_compare_coloring_threshold_rtol", &threshold_rtol, NULL));
3112:       PetscCall(PetscOptionsGetReal(((PetscObject)snes)->options, ((PetscObject)snes)->prefix, "-snes_compare_coloring_threshold_atol", &threshold_atol, NULL));
3113:     }
3114:     if (flag || flag_display || flag_draw || flag_contour || flag_threshold) {
3115:       Mat             Bfd;
3116:       PetscViewer     vdraw, vstdout;
3117:       MatColoring     coloring;
3118:       ISColoring      iscoloring;
3119:       MatFDColoring   matfdcoloring;
3120:       SNESFunctionFn *func;
3121:       void           *funcctx;
3122:       PetscReal       norm1, norm2, normmax;

3124:       PetscCall(MatDuplicate(B, MAT_DO_NOT_COPY_VALUES, &Bfd));
3125:       PetscCall(MatColoringCreate(Bfd, &coloring));
3126:       PetscCall(MatColoringSetType(coloring, MATCOLORINGSL));
3127:       PetscCall(MatColoringSetFromOptions(coloring));
3128:       PetscCall(MatColoringApply(coloring, &iscoloring));
3129:       PetscCall(MatColoringDestroy(&coloring));
3130:       PetscCall(MatFDColoringCreate(Bfd, iscoloring, &matfdcoloring));
3131:       PetscCall(MatFDColoringSetFromOptions(matfdcoloring));
3132:       PetscCall(MatFDColoringSetUp(Bfd, iscoloring, matfdcoloring));
3133:       PetscCall(ISColoringDestroy(&iscoloring));

3135:       /* This method of getting the function is currently unreliable since it doesn't work for DM local functions. */
3136:       PetscCall(SNESGetFunction(snes, NULL, &func, &funcctx));
3137:       PetscCall(MatFDColoringSetFunction(matfdcoloring, (MatFDColoringFn *)func, funcctx));
3138:       PetscCall(PetscObjectSetOptionsPrefix((PetscObject)matfdcoloring, ((PetscObject)snes)->prefix));
3139:       PetscCall(PetscObjectAppendOptionsPrefix((PetscObject)matfdcoloring, "coloring_"));
3140:       PetscCall(MatFDColoringSetFromOptions(matfdcoloring));
3141:       PetscCall(MatFDColoringApply(Bfd, matfdcoloring, X, snes));
3142:       PetscCall(MatFDColoringDestroy(&matfdcoloring));

3144:       PetscCall(PetscViewerASCIIGetStdout(PetscObjectComm((PetscObject)snes), &vstdout));
3145:       if (flag_draw || flag_contour) {
3146:         PetscCall(PetscViewerDrawOpen(PetscObjectComm((PetscObject)snes), NULL, "Colored Jacobians", PETSC_DECIDE, PETSC_DECIDE, 300, 300, &vdraw));
3147:         if (flag_contour) PetscCall(PetscViewerPushFormat(vdraw, PETSC_VIEWER_DRAW_CONTOUR));
3148:       } else vdraw = NULL;
3149:       PetscCall(PetscViewerASCIIPrintf(vstdout, "Explicit preconditioning Jacobian\n"));
3150:       if (flag_display) PetscCall(MatView(B, vstdout));
3151:       if (vdraw) PetscCall(MatView(B, vdraw));
3152:       PetscCall(PetscViewerASCIIPrintf(vstdout, "Colored Finite difference Jacobian\n"));
3153:       if (flag_display) PetscCall(MatView(Bfd, vstdout));
3154:       if (vdraw) PetscCall(MatView(Bfd, vdraw));
3155:       PetscCall(MatAYPX(Bfd, -1.0, B, SAME_NONZERO_PATTERN));
3156:       PetscCall(MatNorm(Bfd, NORM_1, &norm1));
3157:       PetscCall(MatNorm(Bfd, NORM_FROBENIUS, &norm2));
3158:       PetscCall(MatNorm(Bfd, NORM_MAX, &normmax));
3159:       PetscCall(PetscViewerASCIIPrintf(vstdout, "User-provided matrix minus finite difference Jacobian, norm1=%g normFrob=%g normmax=%g\n", (double)norm1, (double)norm2, (double)normmax));
3160:       if (flag_display) PetscCall(MatView(Bfd, vstdout));
3161:       if (vdraw) { /* Always use contour for the difference */
3162:         PetscCall(PetscViewerPushFormat(vdraw, PETSC_VIEWER_DRAW_CONTOUR));
3163:         PetscCall(MatView(Bfd, vdraw));
3164:         PetscCall(PetscViewerPopFormat(vdraw));
3165:       }
3166:       if (flag_contour) PetscCall(PetscViewerPopFormat(vdraw));

3168:       if (flag_threshold) {
3169:         PetscInt bs, rstart, rend, i;
3170:         PetscCall(MatGetBlockSize(B, &bs));
3171:         PetscCall(MatGetOwnershipRange(B, &rstart, &rend));
3172:         for (i = rstart; i < rend; i++) {
3173:           const PetscScalar *ba, *ca;
3174:           const PetscInt    *bj, *cj;
3175:           PetscInt           bn, cn, j, maxentrycol = -1, maxdiffcol = -1, maxrdiffcol = -1;
3176:           PetscReal          maxentry = 0, maxdiff = 0, maxrdiff = 0;
3177:           PetscCall(MatGetRow(B, i, &bn, &bj, &ba));
3178:           PetscCall(MatGetRow(Bfd, i, &cn, &cj, &ca));
3179:           PetscCheck(bn == cn, ((PetscObject)A)->comm, PETSC_ERR_PLIB, "Unexpected different nonzero pattern in -snes_compare_coloring_threshold");
3180:           for (j = 0; j < bn; j++) {
3181:             PetscReal rdiff = PetscAbsScalar(ca[j]) / (threshold_atol + threshold_rtol * PetscAbsScalar(ba[j]));
3182:             if (PetscAbsScalar(ba[j]) > PetscAbs(maxentry)) {
3183:               maxentrycol = bj[j];
3184:               maxentry    = PetscRealPart(ba[j]);
3185:             }
3186:             if (PetscAbsScalar(ca[j]) > PetscAbs(maxdiff)) {
3187:               maxdiffcol = bj[j];
3188:               maxdiff    = PetscRealPart(ca[j]);
3189:             }
3190:             if (rdiff > maxrdiff) {
3191:               maxrdiffcol = bj[j];
3192:               maxrdiff    = rdiff;
3193:             }
3194:           }
3195:           if (maxrdiff > 1) {
3196:             PetscCall(PetscViewerASCIIPrintf(vstdout, "row %" PetscInt_FMT " (maxentry=%g at %" PetscInt_FMT ", maxdiff=%g at %" PetscInt_FMT ", maxrdiff=%g at %" PetscInt_FMT "):", i, (double)maxentry, maxentrycol, (double)maxdiff, maxdiffcol, (double)maxrdiff, maxrdiffcol));
3197:             for (j = 0; j < bn; j++) {
3198:               PetscReal rdiff;
3199:               rdiff = PetscAbsScalar(ca[j]) / (threshold_atol + threshold_rtol * PetscAbsScalar(ba[j]));
3200:               if (rdiff > 1) PetscCall(PetscViewerASCIIPrintf(vstdout, " (%" PetscInt_FMT ",%g:%g)", bj[j], (double)PetscRealPart(ba[j]), (double)PetscRealPart(ca[j])));
3201:             }
3202:             PetscCall(PetscViewerASCIIPrintf(vstdout, "\n"));
3203:           }
3204:           PetscCall(MatRestoreRow(B, i, &bn, &bj, &ba));
3205:           PetscCall(MatRestoreRow(Bfd, i, &cn, &cj, &ca));
3206:         }
3207:       }
3208:       PetscCall(PetscViewerDestroy(&vdraw));
3209:       PetscCall(MatDestroy(&Bfd));
3210:     }
3211:   }
3212:   PetscFunctionReturn(PETSC_SUCCESS);
3213: }

3215: /*@C
3216:   SNESSetJacobian - Sets the function to compute Jacobian as well as the
3217:   location to store the matrix.

3219:   Logically Collective

3221:   Input Parameters:
3222: + snes - the `SNES` context
3223: . Amat - the matrix that defines the (approximate) Jacobian
3224: . Pmat - the matrix to be used in constructing the preconditioner, usually the same as `Amat`.
3225: . J    - Jacobian evaluation routine (if `NULL` then `SNES` retains any previously set value), see `SNESJacobianFn` for details
3226: - ctx  - [optional] user-defined context for private data for the
3227:          Jacobian evaluation routine (may be `NULL`) (if `NULL` then `SNES` retains any previously set value)

3229:   Level: beginner

3231:   Notes:
3232:   If the `Amat` matrix and `Pmat` matrix are different you must call `MatAssemblyBegin()`/`MatAssemblyEnd()` on
3233:   each matrix.

3235:   If you know the operator `Amat` has a null space you can use `MatSetNullSpace()` and `MatSetTransposeNullSpace()` to supply the null
3236:   space to `Amat` and the `KSP` solvers will automatically use that null space as needed during the solution process.

3238:   If using `SNESComputeJacobianDefaultColor()` to assemble a Jacobian, the `ctx` argument
3239:   must be a `MatFDColoring`.

3241:   Other defect-correction schemes can be used by computing a different matrix in place of the Jacobian.  One common
3242:   example is to use the "Picard linearization" which only differentiates through the highest order parts of each term using `SNESSetPicard()`

3244: .seealso: [](ch_snes), `SNES`, `KSPSetOperators()`, `SNESSetFunction()`, `MatMFFDComputeJacobian()`, `SNESComputeJacobianDefaultColor()`, `MatStructure`,
3245:           `SNESSetPicard()`, `SNESJacobianFn`, `SNESFunctionFn`
3246: @*/
3247: PetscErrorCode SNESSetJacobian(SNES snes, Mat Amat, Mat Pmat, SNESJacobianFn *J, void *ctx)
3248: {
3249:   DM dm;

3251:   PetscFunctionBegin;
3255:   if (Amat) PetscCheckSameComm(snes, 1, Amat, 2);
3256:   if (Pmat) PetscCheckSameComm(snes, 1, Pmat, 3);
3257:   PetscCall(SNESGetDM(snes, &dm));
3258:   PetscCall(DMSNESSetJacobian(dm, J, ctx));
3259:   if (Amat) {
3260:     PetscCall(PetscObjectReference((PetscObject)Amat));
3261:     PetscCall(MatDestroy(&snes->jacobian));

3263:     snes->jacobian = Amat;
3264:   }
3265:   if (Pmat) {
3266:     PetscCall(PetscObjectReference((PetscObject)Pmat));
3267:     PetscCall(MatDestroy(&snes->jacobian_pre));

3269:     snes->jacobian_pre = Pmat;
3270:   }
3271:   PetscFunctionReturn(PETSC_SUCCESS);
3272: }

3274: /*@C
3275:   SNESGetJacobian - Returns the Jacobian matrix and optionally the user
3276:   provided context for evaluating the Jacobian.

3278:   Not Collective, but `Mat` object will be parallel if `SNES` is

3280:   Input Parameter:
3281: . snes - the nonlinear solver context

3283:   Output Parameters:
3284: + Amat - location to stash (approximate) Jacobian matrix (or `NULL`)
3285: . Pmat - location to stash matrix used to compute the preconditioner (or `NULL`)
3286: . J    - location to put Jacobian function (or `NULL`), for calling sequence see `SNESJacobianFn`
3287: - ctx  - location to stash Jacobian ctx (or `NULL`)

3289:   Level: advanced

3291: .seealso: [](ch_snes), `SNES`, `Mat`, `SNESSetJacobian()`, `SNESComputeJacobian()`, `SNESJacobianFn`, `SNESGetFunction()`
3292: @*/
3293: PetscErrorCode SNESGetJacobian(SNES snes, Mat *Amat, Mat *Pmat, SNESJacobianFn **J, void **ctx)
3294: {
3295:   DM dm;

3297:   PetscFunctionBegin;
3299:   if (Amat) *Amat = snes->jacobian;
3300:   if (Pmat) *Pmat = snes->jacobian_pre;
3301:   PetscCall(SNESGetDM(snes, &dm));
3302:   PetscCall(DMSNESGetJacobian(dm, J, ctx));
3303:   PetscFunctionReturn(PETSC_SUCCESS);
3304: }

3306: static PetscErrorCode SNESSetDefaultComputeJacobian(SNES snes)
3307: {
3308:   DM     dm;
3309:   DMSNES sdm;

3311:   PetscFunctionBegin;
3312:   PetscCall(SNESGetDM(snes, &dm));
3313:   PetscCall(DMGetDMSNES(dm, &sdm));
3314:   if (!sdm->ops->computejacobian && snes->jacobian_pre) {
3315:     DM        dm;
3316:     PetscBool isdense, ismf;

3318:     PetscCall(SNESGetDM(snes, &dm));
3319:     PetscCall(PetscObjectTypeCompareAny((PetscObject)snes->jacobian_pre, &isdense, MATSEQDENSE, MATMPIDENSE, MATDENSE, NULL));
3320:     PetscCall(PetscObjectTypeCompareAny((PetscObject)snes->jacobian_pre, &ismf, MATMFFD, MATSHELL, NULL));
3321:     if (isdense) {
3322:       PetscCall(DMSNESSetJacobian(dm, SNESComputeJacobianDefault, NULL));
3323:     } else if (!ismf) {
3324:       PetscCall(DMSNESSetJacobian(dm, SNESComputeJacobianDefaultColor, NULL));
3325:     }
3326:   }
3327:   PetscFunctionReturn(PETSC_SUCCESS);
3328: }

3330: /*@
3331:   SNESSetUp - Sets up the internal data structures for the later use
3332:   of a nonlinear solver `SNESSolve()`.

3334:   Collective

3336:   Input Parameter:
3337: . snes - the `SNES` context

3339:   Level: advanced

3341:   Note:
3342:   For basic use of the `SNES` solvers the user does not need to explicitly call
3343:   `SNESSetUp()`, since these actions will automatically occur during
3344:   the call to `SNESSolve()`.  However, if one wishes to control this
3345:   phase separately, `SNESSetUp()` should be called after `SNESCreate()`
3346:   and optional routines of the form SNESSetXXX(), but before `SNESSolve()`.

3348: .seealso: [](ch_snes), `SNES`, `SNESCreate()`, `SNESSolve()`, `SNESDestroy()`, `SNESSetFromOptions()`
3349: @*/
3350: PetscErrorCode SNESSetUp(SNES snes)
3351: {
3352:   DM             dm;
3353:   DMSNES         sdm;
3354:   SNESLineSearch linesearch, pclinesearch;
3355:   void          *lsprectx, *lspostctx;
3356:   PetscBool      mf_operator, mf;
3357:   Vec            f, fpc;
3358:   void          *funcctx;
3359:   void          *jacctx, *appctx;
3360:   Mat            j, jpre;
3361:   PetscErrorCode (*precheck)(SNESLineSearch, Vec, Vec, PetscBool *, void *);
3362:   PetscErrorCode (*postcheck)(SNESLineSearch, Vec, Vec, Vec, PetscBool *, PetscBool *, void *);
3363:   SNESFunctionFn *func;
3364:   SNESJacobianFn *jac;

3366:   PetscFunctionBegin;
3368:   if (snes->setupcalled) PetscFunctionReturn(PETSC_SUCCESS);
3369:   PetscCall(PetscLogEventBegin(SNES_SetUp, snes, 0, 0, 0));

3371:   if (!((PetscObject)snes)->type_name) PetscCall(SNESSetType(snes, SNESNEWTONLS));

3373:   PetscCall(SNESGetFunction(snes, &snes->vec_func, NULL, NULL));

3375:   PetscCall(SNESGetDM(snes, &dm));
3376:   PetscCall(DMGetDMSNES(dm, &sdm));
3377:   PetscCall(SNESSetDefaultComputeJacobian(snes));

3379:   if (!snes->vec_func) PetscCall(DMCreateGlobalVector(dm, &snes->vec_func));

3381:   if (!snes->ksp) PetscCall(SNESGetKSP(snes, &snes->ksp));

3383:   if (snes->linesearch) {
3384:     PetscCall(SNESGetLineSearch(snes, &snes->linesearch));
3385:     PetscCall(SNESLineSearchSetFunction(snes->linesearch, SNESComputeFunction));
3386:   }

3388:   PetscCall(SNESGetUseMatrixFree(snes, &mf_operator, &mf));
3389:   if (snes->npc && snes->npcside == PC_LEFT) {
3390:     snes->mf          = PETSC_TRUE;
3391:     snes->mf_operator = PETSC_FALSE;
3392:   }

3394:   if (snes->npc) {
3395:     /* copy the DM over */
3396:     PetscCall(SNESGetDM(snes, &dm));
3397:     PetscCall(SNESSetDM(snes->npc, dm));

3399:     PetscCall(SNESGetFunction(snes, &f, &func, &funcctx));
3400:     PetscCall(VecDuplicate(f, &fpc));
3401:     PetscCall(SNESSetFunction(snes->npc, fpc, func, funcctx));
3402:     PetscCall(SNESGetJacobian(snes, &j, &jpre, &jac, &jacctx));
3403:     PetscCall(SNESSetJacobian(snes->npc, j, jpre, jac, jacctx));
3404:     PetscCall(SNESGetApplicationContext(snes, &appctx));
3405:     PetscCall(SNESSetApplicationContext(snes->npc, appctx));
3406:     PetscCall(SNESSetUseMatrixFree(snes->npc, mf_operator, mf));
3407:     PetscCall(VecDestroy(&fpc));

3409:     /* copy the function pointers over */
3410:     PetscCall(PetscObjectCopyFortranFunctionPointers((PetscObject)snes, (PetscObject)snes->npc));

3412:     /* default to 1 iteration */
3413:     PetscCall(SNESSetTolerances(snes->npc, 0.0, 0.0, 0.0, 1, snes->npc->max_funcs));
3414:     if (snes->npcside == PC_RIGHT) {
3415:       PetscCall(SNESSetNormSchedule(snes->npc, SNES_NORM_FINAL_ONLY));
3416:     } else {
3417:       PetscCall(SNESSetNormSchedule(snes->npc, SNES_NORM_NONE));
3418:     }
3419:     PetscCall(SNESSetFromOptions(snes->npc));

3421:     /* copy the line search context over */
3422:     if (snes->linesearch && snes->npc->linesearch) {
3423:       PetscCall(SNESGetLineSearch(snes, &linesearch));
3424:       PetscCall(SNESGetLineSearch(snes->npc, &pclinesearch));
3425:       PetscCall(SNESLineSearchGetPreCheck(linesearch, &precheck, &lsprectx));
3426:       PetscCall(SNESLineSearchGetPostCheck(linesearch, &postcheck, &lspostctx));
3427:       PetscCall(SNESLineSearchSetPreCheck(pclinesearch, precheck, lsprectx));
3428:       PetscCall(SNESLineSearchSetPostCheck(pclinesearch, postcheck, lspostctx));
3429:       PetscCall(PetscObjectCopyFortranFunctionPointers((PetscObject)linesearch, (PetscObject)pclinesearch));
3430:     }
3431:   }
3432:   if (snes->mf) PetscCall(SNESSetUpMatrixFree_Private(snes, snes->mf_operator, snes->mf_version));
3433:   if (snes->ops->usercompute && !snes->ctx) PetscCallBack("SNES callback compute application context", (*snes->ops->usercompute)(snes, &snes->ctx));

3435:   snes->jac_iter = 0;
3436:   snes->pre_iter = 0;

3438:   PetscTryTypeMethod(snes, setup);

3440:   PetscCall(SNESSetDefaultComputeJacobian(snes));

3442:   if (snes->npc && snes->npcside == PC_LEFT) {
3443:     if (snes->functype == SNES_FUNCTION_PRECONDITIONED) {
3444:       if (snes->linesearch) {
3445:         PetscCall(SNESGetLineSearch(snes, &linesearch));
3446:         PetscCall(SNESLineSearchSetFunction(linesearch, SNESComputeFunctionDefaultNPC));
3447:       }
3448:     }
3449:   }
3450:   PetscCall(PetscLogEventEnd(SNES_SetUp, snes, 0, 0, 0));
3451:   snes->setupcalled = PETSC_TRUE;
3452:   PetscFunctionReturn(PETSC_SUCCESS);
3453: }

3455: /*@
3456:   SNESReset - Resets a `SNES` context to the state it was in before `SNESSetUp()` was called and removes any allocated `Vec` and `Mat` from its data structures

3458:   Collective

3460:   Input Parameter:
3461: . snes - the nonlinear iterative solver context obtained from `SNESCreate()`

3463:   Level: intermediate

3465:   Notes:
3466:   Any options set on the `SNES` object, including those set with `SNESSetFromOptions()` remain.

3468:   Call this if you wish to reuse a `SNES` but with different size vectors

3470:   Also calls the application context destroy routine set with `SNESSetComputeApplicationContext()`

3472: .seealso: [](ch_snes), `SNES`, `SNESDestroy()`, `SNESCreate()`, `SNESSetUp()`, `SNESSolve()`
3473: @*/
3474: PetscErrorCode SNESReset(SNES snes)
3475: {
3476:   PetscFunctionBegin;
3478:   if (snes->ops->ctxdestroy && snes->ctx) {
3479:     PetscCallBack("SNES callback destroy application context", (*snes->ops->ctxdestroy)(&snes->ctx));
3480:     snes->ctx = NULL;
3481:   }
3482:   if (snes->npc) PetscCall(SNESReset(snes->npc));

3484:   PetscTryTypeMethod(snes, reset);
3485:   if (snes->ksp) PetscCall(KSPReset(snes->ksp));

3487:   if (snes->linesearch) PetscCall(SNESLineSearchReset(snes->linesearch));

3489:   PetscCall(VecDestroy(&snes->vec_rhs));
3490:   PetscCall(VecDestroy(&snes->vec_sol));
3491:   PetscCall(VecDestroy(&snes->vec_sol_update));
3492:   PetscCall(VecDestroy(&snes->vec_func));
3493:   PetscCall(MatDestroy(&snes->jacobian));
3494:   PetscCall(MatDestroy(&snes->jacobian_pre));
3495:   PetscCall(MatDestroy(&snes->picard));
3496:   PetscCall(VecDestroyVecs(snes->nwork, &snes->work));
3497:   PetscCall(VecDestroyVecs(snes->nvwork, &snes->vwork));

3499:   snes->alwayscomputesfinalresidual = PETSC_FALSE;

3501:   snes->nwork = snes->nvwork = 0;
3502:   snes->setupcalled          = PETSC_FALSE;
3503:   PetscFunctionReturn(PETSC_SUCCESS);
3504: }

3506: /*@
3507:   SNESConvergedReasonViewCancel - Clears all the reason view functions for a `SNES` object provided with `SNESConvergedReasonViewSet()` also
3508:   removes the default viewer.

3510:   Collective

3512:   Input Parameter:
3513: . snes - the nonlinear iterative solver context obtained from `SNESCreate()`

3515:   Level: intermediate

3517: .seealso: [](ch_snes), `SNES`, `SNESCreate()`, `SNESDestroy()`, `SNESReset()`, `SNESConvergedReasonViewSet()`
3518: @*/
3519: PetscErrorCode SNESConvergedReasonViewCancel(SNES snes)
3520: {
3521:   PetscInt i;

3523:   PetscFunctionBegin;
3525:   for (i = 0; i < snes->numberreasonviews; i++) {
3526:     if (snes->reasonviewdestroy[i]) PetscCall((*snes->reasonviewdestroy[i])(&snes->reasonviewcontext[i]));
3527:   }
3528:   snes->numberreasonviews = 0;
3529:   PetscCall(PetscViewerDestroy(&snes->convergedreasonviewer));
3530:   PetscFunctionReturn(PETSC_SUCCESS);
3531: }

3533: /*@
3534:   SNESDestroy - Destroys the nonlinear solver context that was created
3535:   with `SNESCreate()`.

3537:   Collective

3539:   Input Parameter:
3540: . snes - the `SNES` context

3542:   Level: beginner

3544: .seealso: [](ch_snes), `SNES`, `SNESCreate()`, `SNESSolve()`
3545: @*/
3546: PetscErrorCode SNESDestroy(SNES *snes)
3547: {
3548:   DM dm;

3550:   PetscFunctionBegin;
3551:   if (!*snes) PetscFunctionReturn(PETSC_SUCCESS);
3553:   if (--((PetscObject)*snes)->refct > 0) {
3554:     *snes = NULL;
3555:     PetscFunctionReturn(PETSC_SUCCESS);
3556:   }

3558:   PetscCall(SNESReset(*snes));
3559:   PetscCall(SNESDestroy(&(*snes)->npc));

3561:   /* if memory was published with SAWs then destroy it */
3562:   PetscCall(PetscObjectSAWsViewOff((PetscObject)*snes));
3563:   PetscTryTypeMethod(*snes, destroy);

3565:   dm = (*snes)->dm;
3566:   while (dm) {
3567:     PetscCall(DMCoarsenHookRemove(dm, DMCoarsenHook_SNESVecSol, DMRestrictHook_SNESVecSol, *snes));
3568:     PetscCall(DMGetCoarseDM(dm, &dm));
3569:   }

3571:   PetscCall(DMDestroy(&(*snes)->dm));
3572:   PetscCall(KSPDestroy(&(*snes)->ksp));
3573:   PetscCall(SNESLineSearchDestroy(&(*snes)->linesearch));

3575:   PetscCall(PetscFree((*snes)->kspconvctx));
3576:   if ((*snes)->ops->convergeddestroy) PetscCall((*(*snes)->ops->convergeddestroy)((*snes)->cnvP));
3577:   if ((*snes)->conv_hist_alloc) PetscCall(PetscFree2((*snes)->conv_hist, (*snes)->conv_hist_its));
3578:   PetscCall(SNESMonitorCancel(*snes));
3579:   PetscCall(SNESConvergedReasonViewCancel(*snes));
3580:   PetscCall(PetscHeaderDestroy(snes));
3581:   PetscFunctionReturn(PETSC_SUCCESS);
3582: }

3584: /* ----------- Routines to set solver parameters ---------- */

3586: /*@
3587:   SNESSetLagPreconditioner - Sets when the preconditioner is rebuilt in the nonlinear solve `SNESSolve()`.

3589:   Logically Collective

3591:   Input Parameters:
3592: + snes - the `SNES` context
3593: - lag  - 1 means rebuild every time the Jacobian is computed within a single nonlinear solve, 2 means every second time
3594:          the Jacobian is built etc. -2 indicates rebuild preconditioner at next chance but then never rebuild after that

3596:   Options Database Keys:
3597: + -snes_lag_jacobian_persists <true,false>       - sets the persistence through multiple `SNESSolve()`
3598: . -snes_lag_jacobian <-2,1,2,...>                - sets the lag
3599: . -snes_lag_preconditioner_persists <true,false> - sets the persistence through multiple `SNESSolve()`
3600: - -snes_lag_preconditioner <-2,1,2,...>          - sets the lag

3602:   Level: intermediate

3604:   Notes:
3605:   The default is 1

3607:   The preconditioner is ALWAYS built in the first iteration of a nonlinear solve unless lag is -1 or `SNESSetLagPreconditionerPersists()` was called

3609:   `SNESSetLagPreconditionerPersists()` allows using the same uniform lagging (for example every second linear solve) across multiple nonlinear solves.

3611: .seealso: [](ch_snes), `SNESGetLagPreconditioner()`, `SNESSetLagJacobian()`, `SNESGetLagJacobian()`, `SNESSetLagPreconditionerPersists()`,
3612:           `SNESSetLagJacobianPersists()`, `SNES`, `SNESSolve()`
3613: @*/
3614: PetscErrorCode SNESSetLagPreconditioner(SNES snes, PetscInt lag)
3615: {
3616:   PetscFunctionBegin;
3618:   PetscCheck(lag >= -2, PETSC_COMM_SELF, PETSC_ERR_ARG_OUTOFRANGE, "Lag must be -2, -1, 1 or greater");
3619:   PetscCheck(lag, PETSC_COMM_SELF, PETSC_ERR_ARG_OUTOFRANGE, "Lag cannot be 0");
3621:   snes->lagpreconditioner = lag;
3622:   PetscFunctionReturn(PETSC_SUCCESS);
3623: }

3625: /*@
3626:   SNESSetGridSequence - sets the number of steps of grid sequencing that `SNES` will do

3628:   Logically Collective

3630:   Input Parameters:
3631: + snes  - the `SNES` context
3632: - steps - the number of refinements to do, defaults to 0

3634:   Options Database Key:
3635: . -snes_grid_sequence <steps> - Use grid sequencing to generate initial guess

3637:   Level: intermediate

3639:   Notes:
3640:   Once grid sequencing is turned on `SNESSolve()` will automatically perform the solve on each grid refinement.

3642:   Use `SNESGetSolution()` to extract the fine grid solution after grid sequencing.

3644: .seealso: [](ch_snes), `SNES`, `SNESGetLagPreconditioner()`, `SNESSetLagJacobian()`, `SNESGetLagJacobian()`, `SNESGetGridSequence()`,
3645:           `SNESSetDM()`, `SNESSolve()`
3646: @*/
3647: PetscErrorCode SNESSetGridSequence(SNES snes, PetscInt steps)
3648: {
3649:   PetscFunctionBegin;
3652:   snes->gridsequence = steps;
3653:   PetscFunctionReturn(PETSC_SUCCESS);
3654: }

3656: /*@
3657:   SNESGetGridSequence - gets the number of steps of grid sequencing that `SNES` will do

3659:   Logically Collective

3661:   Input Parameter:
3662: . snes - the `SNES` context

3664:   Output Parameter:
3665: . steps - the number of refinements to do, defaults to 0

3667:   Level: intermediate

3669: .seealso: [](ch_snes), `SNESGetLagPreconditioner()`, `SNESSetLagJacobian()`, `SNESGetLagJacobian()`, `SNESSetGridSequence()`
3670: @*/
3671: PetscErrorCode SNESGetGridSequence(SNES snes, PetscInt *steps)
3672: {
3673:   PetscFunctionBegin;
3675:   *steps = snes->gridsequence;
3676:   PetscFunctionReturn(PETSC_SUCCESS);
3677: }

3679: /*@
3680:   SNESGetLagPreconditioner - Return how often the preconditioner is rebuilt

3682:   Not Collective

3684:   Input Parameter:
3685: . snes - the `SNES` context

3687:   Output Parameter:
3688: . lag - -1 indicates NEVER rebuild, 1 means rebuild every time the Jacobian is computed within a single nonlinear solve, 2 means every second time
3689:          the Jacobian is built etc. -2 indicates rebuild preconditioner at next chance but then never rebuild after that

3691:   Level: intermediate

3693:   Notes:
3694:   The default is 1

3696:   The preconditioner is ALWAYS built in the first iteration of a nonlinear solve unless lag is -1

3698: .seealso: [](ch_snes), `SNES`, `SNESSetLagPreconditioner()`, `SNESSetLagJacobianPersists()`, `SNESSetLagPreconditionerPersists()`
3699: @*/
3700: PetscErrorCode SNESGetLagPreconditioner(SNES snes, PetscInt *lag)
3701: {
3702:   PetscFunctionBegin;
3704:   *lag = snes->lagpreconditioner;
3705:   PetscFunctionReturn(PETSC_SUCCESS);
3706: }

3708: /*@
3709:   SNESSetLagJacobian - Set when the Jacobian is rebuilt in the nonlinear solve. See `SNESSetLagPreconditioner()` for determining how
3710:   often the preconditioner is rebuilt.

3712:   Logically Collective

3714:   Input Parameters:
3715: + snes - the `SNES` context
3716: - lag  - -1 indicates NEVER rebuild, 1 means rebuild every time the Jacobian is computed within a single nonlinear solve, 2 means every second time
3717:          the Jacobian is built etc. -2 means rebuild at next chance but then never again

3719:   Options Database Keys:
3720: + -snes_lag_jacobian_persists <true,false>       - sets the persistence through multiple SNES solves
3721: . -snes_lag_jacobian <-2,1,2,...>                - sets the lag
3722: . -snes_lag_preconditioner_persists <true,false> - sets the persistence through multiple SNES solves
3723: - -snes_lag_preconditioner <-2,1,2,...>          - sets the lag.

3725:   Level: intermediate

3727:   Notes:
3728:   The default is 1

3730:   The Jacobian is ALWAYS built in the first iteration of a nonlinear solve unless lag is -1

3732:   If  -1 is used before the very first nonlinear solve the CODE WILL FAIL! because no Jacobian is used, use -2 to indicate you want it recomputed
3733:   at the next Newton step but never again (unless it is reset to another value)

3735: .seealso: [](ch_snes), `SNES`, `SNESGetLagPreconditioner()`, `SNESSetLagPreconditioner()`, `SNESGetLagJacobianPersists()`, `SNESSetLagPreconditionerPersists()`
3736: @*/
3737: PetscErrorCode SNESSetLagJacobian(SNES snes, PetscInt lag)
3738: {
3739:   PetscFunctionBegin;
3741:   PetscCheck(lag >= -2, PETSC_COMM_SELF, PETSC_ERR_ARG_OUTOFRANGE, "Lag must be -2, -1, 1 or greater");
3742:   PetscCheck(lag, PETSC_COMM_SELF, PETSC_ERR_ARG_OUTOFRANGE, "Lag cannot be 0");
3744:   snes->lagjacobian = lag;
3745:   PetscFunctionReturn(PETSC_SUCCESS);
3746: }

3748: /*@
3749:   SNESGetLagJacobian - Get how often the Jacobian is rebuilt. See `SNESGetLagPreconditioner()` to determine when the preconditioner is rebuilt

3751:   Not Collective

3753:   Input Parameter:
3754: . snes - the `SNES` context

3756:   Output Parameter:
3757: . lag - -1 indicates NEVER rebuild, 1 means rebuild every time the Jacobian is computed within a single nonlinear solve, 2 means every second time
3758:          the Jacobian is built etc.

3760:   Level: intermediate

3762:   Notes:
3763:   The default is 1

3765:   The jacobian is ALWAYS built in the first iteration of a nonlinear solve unless lag is -1 or `SNESSetLagJacobianPersists()` was called.

3767: .seealso: [](ch_snes), `SNES`, `SNESSetLagJacobian()`, `SNESSetLagPreconditioner()`, `SNESGetLagPreconditioner()`, `SNESSetLagJacobianPersists()`, `SNESSetLagPreconditionerPersists()`

3769: @*/
3770: PetscErrorCode SNESGetLagJacobian(SNES snes, PetscInt *lag)
3771: {
3772:   PetscFunctionBegin;
3774:   *lag = snes->lagjacobian;
3775:   PetscFunctionReturn(PETSC_SUCCESS);
3776: }

3778: /*@
3779:   SNESSetLagJacobianPersists - Set whether or not the Jacobian lagging persists through multiple nonlinear solves

3781:   Logically collective

3783:   Input Parameters:
3784: + snes - the `SNES` context
3785: - flg  - jacobian lagging persists if true

3787:   Options Database Keys:
3788: + -snes_lag_jacobian_persists <true,false>       - sets the persistence through multiple SNES solves
3789: . -snes_lag_jacobian <-2,1,2,...>                - sets the lag
3790: . -snes_lag_preconditioner_persists <true,false> - sets the persistence through multiple SNES solves
3791: - -snes_lag_preconditioner <-2,1,2,...>          - sets the lag

3793:   Level: advanced

3795:   Notes:
3796:   Normally when `SNESSetLagJacobian()` is used, the Jacobian is always rebuilt at the beginning of each new nonlinear solve, this removes that behavior

3798:   This is useful both for nonlinear preconditioning, where it's appropriate to have the Jacobian be stale by
3799:   several solves, and for implicit time-stepping, where Jacobian lagging in the inner nonlinear solve over several
3800:   timesteps may present huge efficiency gains.

3802: .seealso: [](ch_snes), `SNES`, `SNESSetLagPreconditionerPersists()`, `SNESSetLagJacobian()`, `SNESGetLagJacobian()`, `SNESGetNPC()`
3803: @*/
3804: PetscErrorCode SNESSetLagJacobianPersists(SNES snes, PetscBool flg)
3805: {
3806:   PetscFunctionBegin;
3809:   snes->lagjac_persist = flg;
3810:   PetscFunctionReturn(PETSC_SUCCESS);
3811: }

3813: /*@
3814:   SNESSetLagPreconditionerPersists - Set whether or not the preconditioner lagging persists through multiple nonlinear solves

3816:   Logically Collective

3818:   Input Parameters:
3819: + snes - the `SNES` context
3820: - flg  - preconditioner lagging persists if true

3822:   Options Database Keys:
3823: + -snes_lag_jacobian_persists <true,false>       - sets the persistence through multiple SNES solves
3824: . -snes_lag_jacobian <-2,1,2,...>                - sets the lag
3825: . -snes_lag_preconditioner_persists <true,false> - sets the persistence through multiple SNES solves
3826: - -snes_lag_preconditioner <-2,1,2,...>          - sets the lag

3828:   Level: developer

3830:   Notes:
3831:   Normally when `SNESSetLagPreconditioner()` is used, the preconditioner is always rebuilt at the beginning of each new nonlinear solve, this removes that behavior

3833:   This is useful both for nonlinear preconditioning, where it's appropriate to have the preconditioner be stale
3834:   by several solves, and for implicit time-stepping, where preconditioner lagging in the inner nonlinear solve over
3835:   several timesteps may present huge efficiency gains.

3837: .seealso: [](ch_snes), `SNES`, `SNESSetLagJacobianPersists()`, `SNESSetLagJacobian()`, `SNESGetLagJacobian()`, `SNESGetNPC()`, `SNESSetLagPreconditioner()`
3838: @*/
3839: PetscErrorCode SNESSetLagPreconditionerPersists(SNES snes, PetscBool flg)
3840: {
3841:   PetscFunctionBegin;
3844:   snes->lagpre_persist = flg;
3845:   PetscFunctionReturn(PETSC_SUCCESS);
3846: }

3848: /*@
3849:   SNESSetForceIteration - force `SNESSolve()` to take at least one iteration regardless of the initial residual norm

3851:   Logically Collective

3853:   Input Parameters:
3854: + snes  - the `SNES` context
3855: - force - `PETSC_TRUE` require at least one iteration

3857:   Options Database Key:
3858: . -snes_force_iteration <force> - Sets forcing an iteration

3860:   Level: intermediate

3862:   Note:
3863:   This is used sometimes with `TS` to prevent `TS` from detecting a false steady state solution

3865: .seealso: [](ch_snes), `SNES`, `TS`, `SNESSetDivergenceTolerance()`
3866: @*/
3867: PetscErrorCode SNESSetForceIteration(SNES snes, PetscBool force)
3868: {
3869:   PetscFunctionBegin;
3871:   snes->forceiteration = force;
3872:   PetscFunctionReturn(PETSC_SUCCESS);
3873: }

3875: /*@
3876:   SNESGetForceIteration - Check whether or not `SNESSolve()` take at least one iteration regardless of the initial residual norm

3878:   Logically Collective

3880:   Input Parameter:
3881: . snes - the `SNES` context

3883:   Output Parameter:
3884: . force - `PETSC_TRUE` requires at least one iteration.

3886:   Level: intermediate

3888: .seealso: [](ch_snes), `SNES`, `SNESSetForceIteration()`, `SNESSetDivergenceTolerance()`
3889: @*/
3890: PetscErrorCode SNESGetForceIteration(SNES snes, PetscBool *force)
3891: {
3892:   PetscFunctionBegin;
3894:   *force = snes->forceiteration;
3895:   PetscFunctionReturn(PETSC_SUCCESS);
3896: }

3898: /*@
3899:   SNESSetTolerances - Sets various parameters used in `SNES` convergence tests.

3901:   Logically Collective

3903:   Input Parameters:
3904: + snes   - the `SNES` context
3905: . abstol - the absolute convergence tolerance, $ F(x^n) \le abstol $
3906: . rtol   - the relative convergence tolerance, $ F(x^n) \le reltol * F(x^0) $
3907: . stol   - convergence tolerance in terms of the norm of the change in the solution between steps,  || delta x || < stol*|| x ||
3908: . maxit  - the maximum number of iterations allowed in the solver, default 50.
3909: - maxf   - the maximum number of function evaluations allowed in the solver (use `PETSC_UNLIMITED` indicates no limit), default 10,000

3911:   Options Database Keys:
3912: + -snes_atol <abstol>    - Sets `abstol`
3913: . -snes_rtol <rtol>      - Sets `rtol`
3914: . -snes_stol <stol>      - Sets `stol`
3915: . -snes_max_it <maxit>   - Sets `maxit`
3916: - -snes_max_funcs <maxf> - Sets `maxf` (use `unlimited` to have no maximum)

3918:   Level: intermediate

3920:   Note:
3921:   All parameters must be non-negative

3923:   Use `PETSC_CURRENT` to retain the current value of any parameter and `PETSC_DETERMINE` to use the default value for the given `SNES`.
3924:   The default value is the value in the object when its type is set.

3926:   Use `PETSC_UNLIMITED` on `maxit` or `maxf` to indicate there is no bound on the number of iterations or number of function evaluations.

3928:   Fortran Note:
3929:   Use `PETSC_CURRENT_INTEGER`, `PETSC_CURRENT_REAL`, `PETSC_UNLIMITED_INTEGER`, `PETSC_DETERMINE_INTEGER`, or `PETSC_DETERMINE_REAL`

3931: .seealso: [](ch_snes), `SNESSolve()`, `SNES`, `SNESSetDivergenceTolerance()`, `SNESSetForceIteration()`
3932: @*/
3933: PetscErrorCode SNESSetTolerances(SNES snes, PetscReal abstol, PetscReal rtol, PetscReal stol, PetscInt maxit, PetscInt maxf)
3934: {
3935:   PetscFunctionBegin;

3943:   if (abstol == (PetscReal)PETSC_DETERMINE) {
3944:     snes->abstol = snes->default_abstol;
3945:   } else if (abstol != (PetscReal)PETSC_CURRENT) {
3946:     PetscCheck(abstol >= 0.0, PetscObjectComm((PetscObject)snes), PETSC_ERR_ARG_OUTOFRANGE, "Absolute tolerance %g must be non-negative", (double)abstol);
3947:     snes->abstol = abstol;
3948:   }

3950:   if (rtol == (PetscReal)PETSC_DETERMINE) {
3951:     snes->rtol = snes->default_rtol;
3952:   } else if (rtol != (PetscReal)PETSC_CURRENT) {
3953:     PetscCheck(rtol >= 0.0 && 1.0 > rtol, PetscObjectComm((PetscObject)snes), PETSC_ERR_ARG_OUTOFRANGE, "Relative tolerance %g must be non-negative and less than 1.0", (double)rtol);
3954:     snes->rtol = rtol;
3955:   }

3957:   if (stol == (PetscReal)PETSC_DETERMINE) {
3958:     snes->stol = snes->default_stol;
3959:   } else if (stol != (PetscReal)PETSC_CURRENT) {
3960:     PetscCheck(stol >= 0.0, PetscObjectComm((PetscObject)snes), PETSC_ERR_ARG_OUTOFRANGE, "Step tolerance %g must be non-negative", (double)stol);
3961:     snes->stol = stol;
3962:   }

3964:   if (maxit == PETSC_DETERMINE) {
3965:     snes->max_its = snes->default_max_its;
3966:   } else if (maxit == PETSC_UNLIMITED) {
3967:     snes->max_its = PETSC_INT_MAX;
3968:   } else if (maxit != PETSC_CURRENT) {
3969:     PetscCheck(maxit >= 0, PetscObjectComm((PetscObject)snes), PETSC_ERR_ARG_OUTOFRANGE, "Maximum number of iterations %" PetscInt_FMT " must be non-negative", maxit);
3970:     snes->max_its = maxit;
3971:   }

3973:   if (maxf == PETSC_DETERMINE) {
3974:     snes->max_funcs = snes->default_max_funcs;
3975:   } else if (maxf == PETSC_UNLIMITED || maxf == -1) {
3976:     snes->max_funcs = PETSC_UNLIMITED;
3977:   } else if (maxf != PETSC_CURRENT) {
3978:     PetscCheck(maxf >= 0, PetscObjectComm((PetscObject)snes), PETSC_ERR_ARG_OUTOFRANGE, "Maximum number of function evaluations %" PetscInt_FMT " must be nonnegative", maxf);
3979:     snes->max_funcs = maxf;
3980:   }
3981:   PetscFunctionReturn(PETSC_SUCCESS);
3982: }

3984: /*@
3985:   SNESSetDivergenceTolerance - Sets the divergence tolerance used for the `SNES` divergence test.

3987:   Logically Collective

3989:   Input Parameters:
3990: + snes   - the `SNES` context
3991: - divtol - the divergence tolerance. Use `PETSC_UNLIMITED` to deactivate the test. If the residual norm $ F(x^n) \ge divtol * F(x^0) $ the solver
3992:            is stopped due to divergence.

3994:   Options Database Key:
3995: . -snes_divergence_tolerance <divtol> - Sets `divtol`

3997:   Level: intermediate

3999:   Notes:
4000:   Use `PETSC_DETERMINE` to use the default value from when the object's type was set.

4002:   Fortran Note:
4003:   Use ``PETSC_DETERMINE_REAL` or `PETSC_UNLIMITED_REAL`

4005: .seealso: [](ch_snes), `SNES`, `SNESSolve()`, `SNESSetTolerances()`, `SNESGetDivergenceTolerance()`
4006: @*/
4007: PetscErrorCode SNESSetDivergenceTolerance(SNES snes, PetscReal divtol)
4008: {
4009:   PetscFunctionBegin;

4013:   if (divtol == (PetscReal)PETSC_DETERMINE) {
4014:     snes->divtol = snes->default_divtol;
4015:   } else if (divtol == (PetscReal)PETSC_UNLIMITED || divtol == -1) {
4016:     snes->divtol = PETSC_UNLIMITED;
4017:   } else if (divtol != (PetscReal)PETSC_CURRENT) {
4018:     PetscCheck(divtol >= 1.0, PetscObjectComm((PetscObject)snes), PETSC_ERR_ARG_OUTOFRANGE, "Divergence tolerance %g must be greater than 1.0", (double)divtol);
4019:     snes->divtol = divtol;
4020:   }
4021:   PetscFunctionReturn(PETSC_SUCCESS);
4022: }

4024: /*@
4025:   SNESGetTolerances - Gets various parameters used in `SNES` convergence tests.

4027:   Not Collective

4029:   Input Parameter:
4030: . snes - the `SNES` context

4032:   Output Parameters:
4033: + atol  - the absolute convergence tolerance
4034: . rtol  - the relative convergence tolerance
4035: . stol  - convergence tolerance in terms of the norm of the change in the solution between steps
4036: . maxit - the maximum number of iterations allowed
4037: - maxf  - the maximum number of function evaluations allowed, `PETSC_UNLIMITED` indicates no bound

4039:   Level: intermediate

4041:   Notes:
4042:   See `SNESSetTolerances()` for details on the parameters.

4044:   The user can specify `NULL` for any parameter that is not needed.

4046: .seealso: [](ch_snes), `SNES`, `SNESSetTolerances()`
4047: @*/
4048: PetscErrorCode SNESGetTolerances(SNES snes, PetscReal *atol, PetscReal *rtol, PetscReal *stol, PetscInt *maxit, PetscInt *maxf)
4049: {
4050:   PetscFunctionBegin;
4052:   if (atol) *atol = snes->abstol;
4053:   if (rtol) *rtol = snes->rtol;
4054:   if (stol) *stol = snes->stol;
4055:   if (maxit) *maxit = snes->max_its;
4056:   if (maxf) *maxf = snes->max_funcs;
4057:   PetscFunctionReturn(PETSC_SUCCESS);
4058: }

4060: /*@
4061:   SNESGetDivergenceTolerance - Gets divergence tolerance used in divergence test.

4063:   Not Collective

4065:   Input Parameters:
4066: + snes   - the `SNES` context
4067: - divtol - divergence tolerance

4069:   Level: intermediate

4071: .seealso: [](ch_snes), `SNES`, `SNESSetDivergenceTolerance()`
4072: @*/
4073: PetscErrorCode SNESGetDivergenceTolerance(SNES snes, PetscReal *divtol)
4074: {
4075:   PetscFunctionBegin;
4077:   if (divtol) *divtol = snes->divtol;
4078:   PetscFunctionReturn(PETSC_SUCCESS);
4079: }

4081: PETSC_INTERN PetscErrorCode SNESMonitorRange_Private(SNES, PetscInt, PetscReal *);

4083: PetscErrorCode SNESMonitorLGRange(SNES snes, PetscInt n, PetscReal rnorm, void *monctx)
4084: {
4085:   PetscDrawLG      lg;
4086:   PetscReal        x, y, per;
4087:   PetscViewer      v = (PetscViewer)monctx;
4088:   static PetscReal prev; /* should be in the context */
4089:   PetscDraw        draw;

4091:   PetscFunctionBegin;
4093:   PetscCall(PetscViewerDrawGetDrawLG(v, 0, &lg));
4094:   if (!n) PetscCall(PetscDrawLGReset(lg));
4095:   PetscCall(PetscDrawLGGetDraw(lg, &draw));
4096:   PetscCall(PetscDrawSetTitle(draw, "Residual norm"));
4097:   x = (PetscReal)n;
4098:   if (rnorm > 0.0) y = PetscLog10Real(rnorm);
4099:   else y = -15.0;
4100:   PetscCall(PetscDrawLGAddPoint(lg, &x, &y));
4101:   if (n < 20 || !(n % 5) || snes->reason) {
4102:     PetscCall(PetscDrawLGDraw(lg));
4103:     PetscCall(PetscDrawLGSave(lg));
4104:   }

4106:   PetscCall(PetscViewerDrawGetDrawLG(v, 1, &lg));
4107:   if (!n) PetscCall(PetscDrawLGReset(lg));
4108:   PetscCall(PetscDrawLGGetDraw(lg, &draw));
4109:   PetscCall(PetscDrawSetTitle(draw, "% elements > .2*max element"));
4110:   PetscCall(SNESMonitorRange_Private(snes, n, &per));
4111:   x = (PetscReal)n;
4112:   y = 100.0 * per;
4113:   PetscCall(PetscDrawLGAddPoint(lg, &x, &y));
4114:   if (n < 20 || !(n % 5) || snes->reason) {
4115:     PetscCall(PetscDrawLGDraw(lg));
4116:     PetscCall(PetscDrawLGSave(lg));
4117:   }

4119:   PetscCall(PetscViewerDrawGetDrawLG(v, 2, &lg));
4120:   if (!n) {
4121:     prev = rnorm;
4122:     PetscCall(PetscDrawLGReset(lg));
4123:   }
4124:   PetscCall(PetscDrawLGGetDraw(lg, &draw));
4125:   PetscCall(PetscDrawSetTitle(draw, "(norm -oldnorm)/oldnorm"));
4126:   x = (PetscReal)n;
4127:   y = (prev - rnorm) / prev;
4128:   PetscCall(PetscDrawLGAddPoint(lg, &x, &y));
4129:   if (n < 20 || !(n % 5) || snes->reason) {
4130:     PetscCall(PetscDrawLGDraw(lg));
4131:     PetscCall(PetscDrawLGSave(lg));
4132:   }

4134:   PetscCall(PetscViewerDrawGetDrawLG(v, 3, &lg));
4135:   if (!n) PetscCall(PetscDrawLGReset(lg));
4136:   PetscCall(PetscDrawLGGetDraw(lg, &draw));
4137:   PetscCall(PetscDrawSetTitle(draw, "(norm -oldnorm)/oldnorm*(% > .2 max)"));
4138:   x = (PetscReal)n;
4139:   y = (prev - rnorm) / (prev * per);
4140:   if (n > 2) { /*skip initial crazy value */
4141:     PetscCall(PetscDrawLGAddPoint(lg, &x, &y));
4142:   }
4143:   if (n < 20 || !(n % 5) || snes->reason) {
4144:     PetscCall(PetscDrawLGDraw(lg));
4145:     PetscCall(PetscDrawLGSave(lg));
4146:   }
4147:   prev = rnorm;
4148:   PetscFunctionReturn(PETSC_SUCCESS);
4149: }

4151: /*@
4152:   SNESConverged - Run the convergence test and update the `SNESConvergedReason`.

4154:   Collective

4156:   Input Parameters:
4157: + snes  - the `SNES` context
4158: . it    - current iteration
4159: . xnorm - 2-norm of current iterate
4160: . snorm - 2-norm of current step
4161: - fnorm - 2-norm of function

4163:   Level: developer

4165:   Note:
4166:   This routine is called by the `SNESSolve()` implementations.
4167:   It does not typically need to be called by the user.

4169: .seealso: [](ch_snes), `SNES`, `SNESSolve`, `SNESSetConvergenceTest()`
4170: @*/
4171: PetscErrorCode SNESConverged(SNES snes, PetscInt it, PetscReal xnorm, PetscReal snorm, PetscReal fnorm)
4172: {
4173:   PetscFunctionBegin;
4174:   if (!snes->reason) {
4175:     if (snes->normschedule == SNES_NORM_ALWAYS) PetscUseTypeMethod(snes, converged, it, xnorm, snorm, fnorm, &snes->reason, snes->cnvP);
4176:     if (it == snes->max_its && !snes->reason) {
4177:       if (snes->normschedule == SNES_NORM_ALWAYS) {
4178:         PetscCall(PetscInfo(snes, "Maximum number of iterations has been reached: %" PetscInt_FMT "\n", snes->max_its));
4179:         snes->reason = SNES_DIVERGED_MAX_IT;
4180:       } else snes->reason = SNES_CONVERGED_ITS;
4181:     }
4182:   }
4183:   PetscFunctionReturn(PETSC_SUCCESS);
4184: }

4186: /*@
4187:   SNESMonitor - runs any `SNES` monitor routines provided with `SNESMonitor()` or the options database

4189:   Collective

4191:   Input Parameters:
4192: + snes  - nonlinear solver context obtained from `SNESCreate()`
4193: . iter  - current iteration number
4194: - rnorm - current relative norm of the residual

4196:   Level: developer

4198:   Note:
4199:   This routine is called by the `SNESSolve()` implementations.
4200:   It does not typically need to be called by the user.

4202: .seealso: [](ch_snes), `SNES`, `SNESMonitorSet()`
4203: @*/
4204: PetscErrorCode SNESMonitor(SNES snes, PetscInt iter, PetscReal rnorm)
4205: {
4206:   PetscInt i, n = snes->numbermonitors;

4208:   PetscFunctionBegin;
4209:   PetscCall(VecLockReadPush(snes->vec_sol));
4210:   for (i = 0; i < n; i++) PetscCall((*snes->monitor[i])(snes, iter, rnorm, snes->monitorcontext[i]));
4211:   PetscCall(VecLockReadPop(snes->vec_sol));
4212:   PetscFunctionReturn(PETSC_SUCCESS);
4213: }

4215: /* ------------ Routines to set performance monitoring options ----------- */

4217: /*MC
4218:     SNESMonitorFunction - functional form passed to `SNESMonitorSet()` to monitor convergence of nonlinear solver

4220:      Synopsis:
4221: #include <petscsnes.h>
4222:     PetscErrorCode SNESMonitorFunction(SNES snes, PetscInt its, PetscReal norm, void *mctx)

4224:      Collective

4226:     Input Parameters:
4227: +    snes - the `SNES` context
4228: .    its - iteration number
4229: .    norm - 2-norm function value (may be estimated)
4230: -    mctx - [optional] monitoring context

4232:    Level: advanced

4234: .seealso: [](ch_snes), `SNESMonitorSet()`
4235: M*/

4237: /*@C
4238:   SNESMonitorSet - Sets an ADDITIONAL function that is to be used at every
4239:   iteration of the `SNES` nonlinear solver to display the iteration's
4240:   progress.

4242:   Logically Collective

4244:   Input Parameters:
4245: + snes           - the `SNES` context
4246: . f              - the monitor function,  for the calling sequence see `SNESMonitorFunction`
4247: . mctx           - [optional] user-defined context for private data for the monitor routine (use `NULL` if no context is desired)
4248: - monitordestroy - [optional] routine that frees monitor context (may be `NULL`), see `PetscCtxDestroyFn` for the calling sequence

4250:   Options Database Keys:
4251: + -snes_monitor               - sets `SNESMonitorDefault()`
4252: . -snes_monitor draw::draw_lg - sets line graph monitor,
4253: - -snes_monitor_cancel        - cancels all monitors that have been hardwired into a code by calls to `SNESMonitorSet()`, but does not cancel those set via
4254:                                 the options database.

4256:   Level: intermediate

4258:   Note:
4259:   Several different monitoring routines may be set by calling
4260:   `SNESMonitorSet()` multiple times; all will be called in the
4261:   order in which they were set.

4263:   Fortran Note:
4264:   Only a single monitor function can be set for each `SNES` object

4266: .seealso: [](ch_snes), `SNES`, `SNESSolve()`, `SNESMonitorDefault()`, `SNESMonitorCancel()`, `SNESMonitorFunction`, `PetscCtxDestroyFn`
4267: @*/
4268: PetscErrorCode SNESMonitorSet(SNES snes, PetscErrorCode (*f)(SNES, PetscInt, PetscReal, void *), void *mctx, PetscCtxDestroyFn *monitordestroy)
4269: {
4270:   PetscFunctionBegin;
4272:   for (PetscInt i = 0; i < snes->numbermonitors; i++) {
4273:     PetscBool identical;

4275:     PetscCall(PetscMonitorCompare((PetscErrorCode (*)(void))(PetscVoidFn *)f, mctx, monitordestroy, (PetscErrorCode (*)(void))(PetscVoidFn *)snes->monitor[i], snes->monitorcontext[i], snes->monitordestroy[i], &identical));
4276:     if (identical) PetscFunctionReturn(PETSC_SUCCESS);
4277:   }
4278:   PetscCheck(snes->numbermonitors < MAXSNESMONITORS, PETSC_COMM_SELF, PETSC_ERR_ARG_OUTOFRANGE, "Too many monitors set");
4279:   snes->monitor[snes->numbermonitors]          = f;
4280:   snes->monitordestroy[snes->numbermonitors]   = monitordestroy;
4281:   snes->monitorcontext[snes->numbermonitors++] = mctx;
4282:   PetscFunctionReturn(PETSC_SUCCESS);
4283: }

4285: /*@
4286:   SNESMonitorCancel - Clears all the monitor functions for a `SNES` object.

4288:   Logically Collective

4290:   Input Parameter:
4291: . snes - the `SNES` context

4293:   Options Database Key:
4294: . -snes_monitor_cancel - cancels all monitors that have been hardwired
4295:                          into a code by calls to `SNESMonitorSet()`, but does not cancel those
4296:                          set via the options database

4298:   Level: intermediate

4300:   Note:
4301:   There is no way to clear one specific monitor from a `SNES` object.

4303: .seealso: [](ch_snes), `SNES`, `SNESMonitorDefault()`, `SNESMonitorSet()`
4304: @*/
4305: PetscErrorCode SNESMonitorCancel(SNES snes)
4306: {
4307:   PetscInt i;

4309:   PetscFunctionBegin;
4311:   for (i = 0; i < snes->numbermonitors; i++) {
4312:     if (snes->monitordestroy[i]) PetscCall((*snes->monitordestroy[i])(&snes->monitorcontext[i]));
4313:   }
4314:   snes->numbermonitors = 0;
4315:   PetscFunctionReturn(PETSC_SUCCESS);
4316: }

4318: /*MC
4319:     SNESConvergenceTestFunction - functional form used for testing of convergence of nonlinear solver

4321:      Synopsis:
4322: #include <petscsnes.h>
4323:      PetscErrorCode SNESConvergenceTest(SNES snes, PetscInt it, PetscReal xnorm, PetscReal gnorm, PetscReal f, SNESConvergedReason *reason, void *cctx)

4325:      Collective

4327:     Input Parameters:
4328: +    snes - the `SNES` context
4329: .    it - current iteration (0 is the first and is before any Newton step)
4330: .    xnorm - 2-norm of current iterate
4331: .    gnorm - 2-norm of current step
4332: .    f - 2-norm of function
4333: -    cctx - [optional] convergence context

4335:     Output Parameter:
4336: .    reason - reason for convergence/divergence, only needs to be set when convergence or divergence is detected

4338:    Level: intermediate

4340: .seealso: [](ch_snes), `SNES`, `SNESSolve`, `SNESSetConvergenceTest()`
4341: M*/

4343: /*@C
4344:   SNESSetConvergenceTest - Sets the function that is to be used
4345:   to test for convergence of the nonlinear iterative solution.

4347:   Logically Collective

4349:   Input Parameters:
4350: + snes                        - the `SNES` context
4351: . SNESConvergenceTestFunction - routine to test for convergence
4352: . cctx                        - [optional] context for private data for the convergence routine  (may be `NULL`)
4353: - destroy                     - [optional] destructor for the context (may be `NULL`; `PETSC_NULL_FUNCTION` in Fortran)

4355:   Level: advanced

4357: .seealso: [](ch_snes), `SNES`, `SNESConvergedDefault()`, `SNESConvergedSkip()`, `SNESConvergenceTestFunction`
4358: @*/
4359: PetscErrorCode SNESSetConvergenceTest(SNES snes, PetscErrorCode (*SNESConvergenceTestFunction)(SNES, PetscInt, PetscReal, PetscReal, PetscReal, SNESConvergedReason *, void *), void *cctx, PetscErrorCode (*destroy)(void *))
4360: {
4361:   PetscFunctionBegin;
4363:   if (!SNESConvergenceTestFunction) SNESConvergenceTestFunction = SNESConvergedSkip;
4364:   if (snes->ops->convergeddestroy) PetscCall((*snes->ops->convergeddestroy)(snes->cnvP));
4365:   snes->ops->converged        = SNESConvergenceTestFunction;
4366:   snes->ops->convergeddestroy = destroy;
4367:   snes->cnvP                  = cctx;
4368:   PetscFunctionReturn(PETSC_SUCCESS);
4369: }

4371: /*@
4372:   SNESGetConvergedReason - Gets the reason the `SNES` iteration was stopped, which may be due to convergence, divergence, or stagnation

4374:   Not Collective

4376:   Input Parameter:
4377: . snes - the `SNES` context

4379:   Output Parameter:
4380: . reason - negative value indicates diverged, positive value converged, see `SNESConvergedReason` for the individual convergence tests for complete lists

4382:   Options Database Key:
4383: . -snes_converged_reason - prints the reason to standard out

4385:   Level: intermediate

4387:   Note:
4388:   Should only be called after the call the `SNESSolve()` is complete, if it is called earlier it returns the value `SNES__CONVERGED_ITERATING`.

4390: .seealso: [](ch_snes), `SNESSolve()`, `SNESSetConvergenceTest()`, `SNESSetConvergedReason()`, `SNESConvergedReason`, `SNESGetConvergedReasonString()`
4391: @*/
4392: PetscErrorCode SNESGetConvergedReason(SNES snes, SNESConvergedReason *reason)
4393: {
4394:   PetscFunctionBegin;
4396:   PetscAssertPointer(reason, 2);
4397:   *reason = snes->reason;
4398:   PetscFunctionReturn(PETSC_SUCCESS);
4399: }

4401: /*@C
4402:   SNESGetConvergedReasonString - Return a human readable string for `SNESConvergedReason`

4404:   Not Collective

4406:   Input Parameter:
4407: . snes - the `SNES` context

4409:   Output Parameter:
4410: . strreason - a human readable string that describes `SNES` converged reason

4412:   Level: beginner

4414: .seealso: [](ch_snes), `SNES`, `SNESGetConvergedReason()`
4415: @*/
4416: PetscErrorCode SNESGetConvergedReasonString(SNES snes, const char **strreason)
4417: {
4418:   PetscFunctionBegin;
4420:   PetscAssertPointer(strreason, 2);
4421:   *strreason = SNESConvergedReasons[snes->reason];
4422:   PetscFunctionReturn(PETSC_SUCCESS);
4423: }

4425: /*@
4426:   SNESSetConvergedReason - Sets the reason the `SNES` iteration was stopped.

4428:   Not Collective

4430:   Input Parameters:
4431: + snes   - the `SNES` context
4432: - reason - negative value indicates diverged, positive value converged, see `SNESConvergedReason` or the
4433:             manual pages for the individual convergence tests for complete lists

4435:   Level: developer

4437:   Developer Note:
4438:   Called inside the various `SNESSolve()` implementations

4440: .seealso: [](ch_snes), `SNESGetConvergedReason()`, `SNESSetConvergenceTest()`, `SNESConvergedReason`
4441: @*/
4442: PetscErrorCode SNESSetConvergedReason(SNES snes, SNESConvergedReason reason)
4443: {
4444:   PetscFunctionBegin;
4446:   PetscCheck(!snes->errorifnotconverged || reason > 0, PetscObjectComm((PetscObject)snes), PETSC_ERR_PLIB, "SNES code should have previously errored due to negative reason");
4447:   snes->reason = reason;
4448:   PetscFunctionReturn(PETSC_SUCCESS);
4449: }

4451: /*@
4452:   SNESSetConvergenceHistory - Sets the arrays used to hold the convergence history.

4454:   Logically Collective

4456:   Input Parameters:
4457: + snes  - iterative context obtained from `SNESCreate()`
4458: . a     - array to hold history, this array will contain the function norms computed at each step
4459: . its   - integer array holds the number of linear iterations for each solve.
4460: . na    - size of `a` and `its`
4461: - reset - `PETSC_TRUE` indicates each new nonlinear solve resets the history counter to zero,
4462:           else it continues storing new values for new nonlinear solves after the old ones

4464:   Level: intermediate

4466:   Notes:
4467:   If 'a' and 'its' are `NULL` then space is allocated for the history. If 'na' is `PETSC_DECIDE` (or, deprecated, `PETSC_DEFAULT`) then a
4468:   default array of length 1,000 is allocated.

4470:   This routine is useful, e.g., when running a code for purposes
4471:   of accurate performance monitoring, when no I/O should be done
4472:   during the section of code that is being timed.

4474:   If the arrays run out of space after a number of iterations then the later values are not saved in the history

4476: .seealso: [](ch_snes), `SNES`, `SNESSolve()`, `SNESGetConvergenceHistory()`
4477: @*/
4478: PetscErrorCode SNESSetConvergenceHistory(SNES snes, PetscReal a[], PetscInt its[], PetscInt na, PetscBool reset)
4479: {
4480:   PetscFunctionBegin;
4482:   if (a) PetscAssertPointer(a, 2);
4483:   if (its) PetscAssertPointer(its, 3);
4484:   if (!a) {
4485:     if (na == PETSC_DECIDE) na = 1000;
4486:     PetscCall(PetscCalloc2(na, &a, na, &its));
4487:     snes->conv_hist_alloc = PETSC_TRUE;
4488:   }
4489:   snes->conv_hist       = a;
4490:   snes->conv_hist_its   = its;
4491:   snes->conv_hist_max   = (size_t)na;
4492:   snes->conv_hist_len   = 0;
4493:   snes->conv_hist_reset = reset;
4494:   PetscFunctionReturn(PETSC_SUCCESS);
4495: }

4497: #if defined(PETSC_HAVE_MATLAB)
4498:   #include <engine.h> /* MATLAB include file */
4499:   #include <mex.h>    /* MATLAB include file */

4501: PETSC_EXTERN mxArray *SNESGetConvergenceHistoryMatlab(SNES snes)
4502: {
4503:   mxArray   *mat;
4504:   PetscInt   i;
4505:   PetscReal *ar;

4507:   mat = mxCreateDoubleMatrix(snes->conv_hist_len, 1, mxREAL);
4508:   ar  = (PetscReal *)mxGetData(mat);
4509:   for (i = 0; i < snes->conv_hist_len; i++) ar[i] = snes->conv_hist[i];
4510:   return mat;
4511: }
4512: #endif

4514: /*@C
4515:   SNESGetConvergenceHistory - Gets the arrays used to hold the convergence history.

4517:   Not Collective

4519:   Input Parameter:
4520: . snes - iterative context obtained from `SNESCreate()`

4522:   Output Parameters:
4523: + a   - array to hold history, usually was set with `SNESSetConvergenceHistory()`
4524: . its - integer array holds the number of linear iterations (or
4525:          negative if not converged) for each solve.
4526: - na  - size of `a` and `its`

4528:   Level: intermediate

4530:   Note:
4531:   This routine is useful, e.g., when running a code for purposes
4532:   of accurate performance monitoring, when no I/O should be done
4533:   during the section of code that is being timed.

4535:   Fortran Notes:
4536:   Return the arrays with ``SNESRestoreConvergenceHistory()`

4538:   Use the arguments
4539: .vb
4540:   PetscReal, pointer :: a(:)
4541:   PetscInt, pointer :: its(:)
4542: .ve

4544: .seealso: [](ch_snes), `SNES`, `SNESSolve()`, `SNESSetConvergenceHistory()`
4545: @*/
4546: PetscErrorCode SNESGetConvergenceHistory(SNES snes, PetscReal *a[], PetscInt *its[], PetscInt *na)
4547: {
4548:   PetscFunctionBegin;
4550:   if (a) *a = snes->conv_hist;
4551:   if (its) *its = snes->conv_hist_its;
4552:   if (na) *na = (PetscInt)snes->conv_hist_len;
4553:   PetscFunctionReturn(PETSC_SUCCESS);
4554: }

4556: /*@C
4557:   SNESSetUpdate - Sets the general-purpose update function called
4558:   at the beginning of every iteration of the nonlinear solve. Specifically
4559:   it is called just before the Jacobian is "evaluated" and after the function
4560:   evaluation.

4562:   Logically Collective

4564:   Input Parameters:
4565: + snes - The nonlinear solver context
4566: - func - The update function; for calling sequence see `SNESUpdateFn`

4568:   Level: advanced

4570:   Notes:
4571:   This is NOT what one uses to update the ghost points before a function evaluation, that should be done at the beginning of your function provided
4572:   to `SNESSetFunction()`, or `SNESSetPicard()`
4573:   This is not used by most users, and it is intended to provide a general hook that is run
4574:   right before the direction step is computed.

4576:   Users are free to modify the current residual vector,
4577:   the current linearization point, or any other vector associated to the specific solver used.
4578:   If such modifications take place, it is the user responsibility to update all the relevant
4579:   vectors. For example, if one is adjusting the model parameters at each Newton step their code may look like
4580: .vb
4581:   PetscErrorCode update(SNES snes, PetscInt iteration)
4582:   {
4583:     PetscFunctionBeginUser;
4584:     if (iteration > 0) {
4585:       // update the model parameters here
4586:       Vec x,f;
4587:       PetscCall(SNESGetSolution(snes,&x));
4588:       PetcCall(SNESGetFunction(snes,&f,NULL,NULL));
4589:       PetscCall(SNESComputeFunction(snes,x,f));
4590:     }
4591:     PetscFunctionReturn(PETSC_SUCCESS);
4592:   }
4593: .ve

4595:   There are a variety of function hooks one many set that are called at different stages of the nonlinear solution process, see the functions listed below.

4597: .seealso: [](ch_snes), `SNES`, `SNESSolve()`, `SNESSetJacobian()`, `SNESLineSearchSetPreCheck()`, `SNESLineSearchSetPostCheck()`, `SNESNewtonTRSetPreCheck()`, `SNESNewtonTRSetPostCheck()`,
4598:          `SNESMonitorSet()`
4599: @*/
4600: PetscErrorCode SNESSetUpdate(SNES snes, SNESUpdateFn *func)
4601: {
4602:   PetscFunctionBegin;
4604:   snes->ops->update = func;
4605:   PetscFunctionReturn(PETSC_SUCCESS);
4606: }

4608: /*@
4609:   SNESConvergedReasonView - Displays the reason a `SNES` solve converged or diverged to a viewer

4611:   Collective

4613:   Input Parameters:
4614: + snes   - iterative context obtained from `SNESCreate()`
4615: - viewer - the viewer to display the reason

4617:   Options Database Keys:
4618: + -snes_converged_reason          - print reason for converged or diverged, also prints number of iterations
4619: - -snes_converged_reason ::failed - only print reason and number of iterations when diverged

4621:   Level: beginner

4623:   Note:
4624:   To change the format of the output call `PetscViewerPushFormat`(viewer,format) before this call. Use `PETSC_VIEWER_DEFAULT` for the default,
4625:   use `PETSC_VIEWER_FAILED` to only display a reason if it fails.

4627: .seealso: [](ch_snes), `SNESConvergedReason`, `PetscViewer`, `SNES`,
4628:           `SNESCreate()`, `SNESSetUp()`, `SNESDestroy()`, `SNESSetTolerances()`, `SNESConvergedDefault()`, `SNESGetConvergedReason()`,
4629:           `SNESConvergedReasonViewFromOptions()`,
4630:           `PetscViewerPushFormat()`, `PetscViewerPopFormat()`
4631: @*/
4632: PetscErrorCode SNESConvergedReasonView(SNES snes, PetscViewer viewer)
4633: {
4634:   PetscViewerFormat format;
4635:   PetscBool         isAscii;

4637:   PetscFunctionBegin;
4638:   if (!viewer) viewer = PETSC_VIEWER_STDOUT_(PetscObjectComm((PetscObject)snes));
4639:   PetscCall(PetscObjectTypeCompare((PetscObject)viewer, PETSCVIEWERASCII, &isAscii));
4640:   if (isAscii) {
4641:     PetscCall(PetscViewerGetFormat(viewer, &format));
4642:     PetscCall(PetscViewerASCIIAddTab(viewer, ((PetscObject)snes)->tablevel + 1));
4643:     if (format == PETSC_VIEWER_ASCII_INFO_DETAIL) {
4644:       DM       dm;
4645:       Vec      u;
4646:       PetscDS  prob;
4647:       PetscInt Nf, f;
4648:       PetscErrorCode (**exactSol)(PetscInt, PetscReal, const PetscReal[], PetscInt, PetscScalar[], void *);
4649:       void    **exactCtx;
4650:       PetscReal error;

4652:       PetscCall(SNESGetDM(snes, &dm));
4653:       PetscCall(SNESGetSolution(snes, &u));
4654:       PetscCall(DMGetDS(dm, &prob));
4655:       PetscCall(PetscDSGetNumFields(prob, &Nf));
4656:       PetscCall(PetscMalloc2(Nf, &exactSol, Nf, &exactCtx));
4657:       for (f = 0; f < Nf; ++f) PetscCall(PetscDSGetExactSolution(prob, f, &exactSol[f], &exactCtx[f]));
4658:       PetscCall(DMComputeL2Diff(dm, 0.0, exactSol, exactCtx, u, &error));
4659:       PetscCall(PetscFree2(exactSol, exactCtx));
4660:       if (error < 1.0e-11) PetscCall(PetscViewerASCIIPrintf(viewer, "L_2 Error: < 1.0e-11\n"));
4661:       else PetscCall(PetscViewerASCIIPrintf(viewer, "L_2 Error: %g\n", (double)error));
4662:     }
4663:     if (snes->reason > 0 && format != PETSC_VIEWER_FAILED) {
4664:       if (((PetscObject)snes)->prefix) {
4665:         PetscCall(PetscViewerASCIIPrintf(viewer, "Nonlinear %s solve converged due to %s iterations %" PetscInt_FMT "\n", ((PetscObject)snes)->prefix, SNESConvergedReasons[snes->reason], snes->iter));
4666:       } else {
4667:         PetscCall(PetscViewerASCIIPrintf(viewer, "Nonlinear solve converged due to %s iterations %" PetscInt_FMT "\n", SNESConvergedReasons[snes->reason], snes->iter));
4668:       }
4669:     } else if (snes->reason <= 0) {
4670:       if (((PetscObject)snes)->prefix) {
4671:         PetscCall(PetscViewerASCIIPrintf(viewer, "Nonlinear %s solve did not converge due to %s iterations %" PetscInt_FMT "\n", ((PetscObject)snes)->prefix, SNESConvergedReasons[snes->reason], snes->iter));
4672:       } else {
4673:         PetscCall(PetscViewerASCIIPrintf(viewer, "Nonlinear solve did not converge due to %s iterations %" PetscInt_FMT "\n", SNESConvergedReasons[snes->reason], snes->iter));
4674:       }
4675:     }
4676:     PetscCall(PetscViewerASCIISubtractTab(viewer, ((PetscObject)snes)->tablevel + 1));
4677:   }
4678:   PetscFunctionReturn(PETSC_SUCCESS);
4679: }

4681: /*@C
4682:   SNESConvergedReasonViewSet - Sets an ADDITIONAL function that is to be used at the
4683:   end of the nonlinear solver to display the convergence reason of the nonlinear solver.

4685:   Logically Collective

4687:   Input Parameters:
4688: + snes              - the `SNES` context
4689: . f                 - the `SNESConvergedReason` view function
4690: . vctx              - [optional] user-defined context for private data for the `SNESConvergedReason` view function (use `NULL` if no context is desired)
4691: - reasonviewdestroy - [optional] routine that frees the context (may be `NULL`), see `PetscCtxDestroyFn` for the calling sequence

4693:   Calling sequence of `f`:
4694: + snes - the `SNES` context
4695: - vctx - [optional] context for private data for the function

4697:   Options Database Keys:
4698: + -snes_converged_reason             - sets a default `SNESConvergedReasonView()`
4699: - -snes_converged_reason_view_cancel - cancels all converged reason viewers that have been hardwired into a code by
4700:                                        calls to `SNESConvergedReasonViewSet()`, but does not cancel those set via the options database.

4702:   Level: intermediate

4704:   Note:
4705:   Several different converged reason view routines may be set by calling
4706:   `SNESConvergedReasonViewSet()` multiple times; all will be called in the
4707:   order in which they were set.

4709: .seealso: [](ch_snes), `SNES`, `SNESSolve()`, `SNESConvergedReason`, `SNESGetConvergedReason()`, `SNESConvergedReasonView()`, `SNESConvergedReasonViewCancel()`,
4710:           `PetscCtxDestroyFn`
4711: @*/
4712: PetscErrorCode SNESConvergedReasonViewSet(SNES snes, PetscErrorCode (*f)(SNES snes, void *vctx), void *vctx, PetscCtxDestroyFn *reasonviewdestroy)
4713: {
4714:   PetscFunctionBegin;
4716:   for (PetscInt i = 0; i < snes->numberreasonviews; i++) {
4717:     PetscBool identical;

4719:     PetscCall(PetscMonitorCompare((PetscErrorCode (*)(void))(PetscVoidFn *)f, vctx, reasonviewdestroy, (PetscErrorCode (*)(void))(PetscVoidFn *)snes->reasonview[i], snes->reasonviewcontext[i], snes->reasonviewdestroy[i], &identical));
4720:     if (identical) PetscFunctionReturn(PETSC_SUCCESS);
4721:   }
4722:   PetscCheck(snes->numberreasonviews < MAXSNESREASONVIEWS, PETSC_COMM_SELF, PETSC_ERR_ARG_OUTOFRANGE, "Too many SNES reasonview set");
4723:   snes->reasonview[snes->numberreasonviews]          = f;
4724:   snes->reasonviewdestroy[snes->numberreasonviews]   = reasonviewdestroy;
4725:   snes->reasonviewcontext[snes->numberreasonviews++] = vctx;
4726:   PetscFunctionReturn(PETSC_SUCCESS);
4727: }

4729: /*@
4730:   SNESConvergedReasonViewFromOptions - Processes command line options to determine if/how a `SNESConvergedReason` is to be viewed at the end of `SNESSolve()`
4731:   All the user-provided viewer routines set with `SNESConvergedReasonViewSet()` will be called, if they exist.

4733:   Collective

4735:   Input Parameter:
4736: . snes - the `SNES` object

4738:   Level: advanced

4740: .seealso: [](ch_snes), `SNES`, `SNESConvergedReason`, `SNESConvergedReasonViewSet()`, `SNESCreate()`, `SNESSetUp()`, `SNESDestroy()`,
4741:           `SNESSetTolerances()`, `SNESConvergedDefault()`, `SNESGetConvergedReason()`, `SNESConvergedReasonView()`
4742: @*/
4743: PetscErrorCode SNESConvergedReasonViewFromOptions(SNES snes)
4744: {
4745:   static PetscBool incall = PETSC_FALSE;

4747:   PetscFunctionBegin;
4748:   if (incall) PetscFunctionReturn(PETSC_SUCCESS);
4749:   incall = PETSC_TRUE;

4751:   /* All user-provided viewers are called first, if they exist. */
4752:   for (PetscInt i = 0; i < snes->numberreasonviews; i++) PetscCall((*snes->reasonview[i])(snes, snes->reasonviewcontext[i]));

4754:   /* Call PETSc default routine if users ask for it */
4755:   if (snes->convergedreasonviewer) {
4756:     PetscCall(PetscViewerPushFormat(snes->convergedreasonviewer, snes->convergedreasonformat));
4757:     PetscCall(SNESConvergedReasonView(snes, snes->convergedreasonviewer));
4758:     PetscCall(PetscViewerPopFormat(snes->convergedreasonviewer));
4759:   }
4760:   incall = PETSC_FALSE;
4761:   PetscFunctionReturn(PETSC_SUCCESS);
4762: }

4764: /*@
4765:   SNESSolve - Solves a nonlinear system $F(x) = b $ associated with a `SNES` object

4767:   Collective

4769:   Input Parameters:
4770: + snes - the `SNES` context
4771: . b    - the constant part of the equation $F(x) = b$, or `NULL` to use zero.
4772: - x    - the solution vector.

4774:   Level: beginner

4776:   Note:
4777:   The user should initialize the vector, `x`, with the initial guess
4778:   for the nonlinear solve prior to calling `SNESSolve()` .

4780: .seealso: [](ch_snes), `SNES`, `SNESCreate()`, `SNESDestroy()`, `SNESSetFunction()`, `SNESSetJacobian()`, `SNESSetGridSequence()`, `SNESGetSolution()`,
4781:           `SNESNewtonTRSetPreCheck()`, `SNESNewtonTRGetPreCheck()`, `SNESNewtonTRSetPostCheck()`, `SNESNewtonTRGetPostCheck()`,
4782:           `SNESLineSearchSetPostCheck()`, `SNESLineSearchGetPostCheck()`, `SNESLineSearchSetPreCheck()`, `SNESLineSearchGetPreCheck()`
4783: @*/
4784: PetscErrorCode SNESSolve(SNES snes, Vec b, Vec x)
4785: {
4786:   PetscBool flg;
4787:   PetscInt  grid;
4788:   Vec       xcreated = NULL;
4789:   DM        dm;

4791:   PetscFunctionBegin;
4794:   if (x) PetscCheckSameComm(snes, 1, x, 3);
4796:   if (b) PetscCheckSameComm(snes, 1, b, 2);

4798:   /* High level operations using the nonlinear solver */
4799:   {
4800:     PetscViewer       viewer;
4801:     PetscViewerFormat format;
4802:     PetscInt          num;
4803:     PetscBool         flg;
4804:     static PetscBool  incall = PETSC_FALSE;

4806:     if (!incall) {
4807:       /* Estimate the convergence rate of the discretization */
4808:       PetscCall(PetscOptionsCreateViewer(PetscObjectComm((PetscObject)snes), ((PetscObject)snes)->options, ((PetscObject)snes)->prefix, "-snes_convergence_estimate", &viewer, &format, &flg));
4809:       if (flg) {
4810:         PetscConvEst conv;
4811:         DM           dm;
4812:         PetscReal   *alpha; /* Convergence rate of the solution error for each field in the L_2 norm */
4813:         PetscInt     Nf;

4815:         incall = PETSC_TRUE;
4816:         PetscCall(SNESGetDM(snes, &dm));
4817:         PetscCall(DMGetNumFields(dm, &Nf));
4818:         PetscCall(PetscCalloc1(Nf, &alpha));
4819:         PetscCall(PetscConvEstCreate(PetscObjectComm((PetscObject)snes), &conv));
4820:         PetscCall(PetscConvEstSetSolver(conv, (PetscObject)snes));
4821:         PetscCall(PetscConvEstSetFromOptions(conv));
4822:         PetscCall(PetscConvEstSetUp(conv));
4823:         PetscCall(PetscConvEstGetConvRate(conv, alpha));
4824:         PetscCall(PetscViewerPushFormat(viewer, format));
4825:         PetscCall(PetscConvEstRateView(conv, alpha, viewer));
4826:         PetscCall(PetscViewerPopFormat(viewer));
4827:         PetscCall(PetscViewerDestroy(&viewer));
4828:         PetscCall(PetscConvEstDestroy(&conv));
4829:         PetscCall(PetscFree(alpha));
4830:         incall = PETSC_FALSE;
4831:       }
4832:       /* Adaptively refine the initial grid */
4833:       num = 1;
4834:       PetscCall(PetscOptionsGetInt(NULL, ((PetscObject)snes)->prefix, "-snes_adapt_initial", &num, &flg));
4835:       if (flg) {
4836:         DMAdaptor adaptor;

4838:         incall = PETSC_TRUE;
4839:         PetscCall(DMAdaptorCreate(PetscObjectComm((PetscObject)snes), &adaptor));
4840:         PetscCall(DMAdaptorSetSolver(adaptor, snes));
4841:         PetscCall(DMAdaptorSetSequenceLength(adaptor, num));
4842:         PetscCall(DMAdaptorSetFromOptions(adaptor));
4843:         PetscCall(DMAdaptorSetUp(adaptor));
4844:         PetscCall(DMAdaptorAdapt(adaptor, x, DM_ADAPTATION_INITIAL, &dm, &x));
4845:         PetscCall(DMAdaptorDestroy(&adaptor));
4846:         incall = PETSC_FALSE;
4847:       }
4848:       /* Use grid sequencing to adapt */
4849:       num = 0;
4850:       PetscCall(PetscOptionsGetInt(NULL, ((PetscObject)snes)->prefix, "-snes_adapt_sequence", &num, NULL));
4851:       if (num) {
4852:         DMAdaptor   adaptor;
4853:         const char *prefix;

4855:         incall = PETSC_TRUE;
4856:         PetscCall(DMAdaptorCreate(PetscObjectComm((PetscObject)snes), &adaptor));
4857:         PetscCall(SNESGetOptionsPrefix(snes, &prefix));
4858:         PetscCall(DMAdaptorSetOptionsPrefix(adaptor, prefix));
4859:         PetscCall(DMAdaptorSetSolver(adaptor, snes));
4860:         PetscCall(DMAdaptorSetSequenceLength(adaptor, num));
4861:         PetscCall(DMAdaptorSetFromOptions(adaptor));
4862:         PetscCall(DMAdaptorSetUp(adaptor));
4863:         PetscCall(PetscObjectViewFromOptions((PetscObject)adaptor, NULL, "-snes_adapt_view"));
4864:         PetscCall(DMAdaptorAdapt(adaptor, x, DM_ADAPTATION_SEQUENTIAL, &dm, &x));
4865:         PetscCall(DMAdaptorDestroy(&adaptor));
4866:         incall = PETSC_FALSE;
4867:       }
4868:     }
4869:   }
4870:   if (!x) x = snes->vec_sol;
4871:   if (!x) {
4872:     PetscCall(SNESGetDM(snes, &dm));
4873:     PetscCall(DMCreateGlobalVector(dm, &xcreated));
4874:     x = xcreated;
4875:   }
4876:   PetscCall(SNESViewFromOptions(snes, NULL, "-snes_view_pre"));

4878:   for (grid = 0; grid < snes->gridsequence; grid++) PetscCall(PetscViewerASCIIPushTab(PETSC_VIEWER_STDOUT_(PetscObjectComm((PetscObject)snes))));
4879:   for (grid = 0; grid < snes->gridsequence + 1; grid++) {
4880:     /* set solution vector */
4881:     if (!grid) PetscCall(PetscObjectReference((PetscObject)x));
4882:     PetscCall(VecDestroy(&snes->vec_sol));
4883:     snes->vec_sol = x;
4884:     PetscCall(SNESGetDM(snes, &dm));

4886:     /* set affine vector if provided */
4887:     if (b) PetscCall(PetscObjectReference((PetscObject)b));
4888:     PetscCall(VecDestroy(&snes->vec_rhs));
4889:     snes->vec_rhs = b;

4891:     if (snes->vec_rhs) PetscCheck(snes->vec_func != snes->vec_rhs, PETSC_COMM_SELF, PETSC_ERR_ARG_IDN, "Right hand side vector cannot be function vector");
4892:     PetscCheck(snes->vec_func != snes->vec_sol, PETSC_COMM_SELF, PETSC_ERR_ARG_IDN, "Solution vector cannot be function vector");
4893:     PetscCheck(snes->vec_rhs != snes->vec_sol, PETSC_COMM_SELF, PETSC_ERR_ARG_IDN, "Solution vector cannot be right-hand side vector");
4894:     if (!snes->vec_sol_update /* && snes->vec_sol */) PetscCall(VecDuplicate(snes->vec_sol, &snes->vec_sol_update));
4895:     PetscCall(DMShellSetGlobalVector(dm, snes->vec_sol));
4896:     PetscCall(SNESSetUp(snes));

4898:     if (!grid) {
4899:       if (snes->ops->computeinitialguess) PetscCallBack("SNES callback compute initial guess", (*snes->ops->computeinitialguess)(snes, snes->vec_sol, snes->initialguessP));
4900:     }

4902:     if (snes->conv_hist_reset) snes->conv_hist_len = 0;
4903:     PetscCall(SNESResetCounters(snes));
4904:     snes->reason = SNES_CONVERGED_ITERATING;
4905:     PetscCall(PetscLogEventBegin(SNES_Solve, snes, 0, 0, 0));
4906:     PetscUseTypeMethod(snes, solve);
4907:     PetscCall(PetscLogEventEnd(SNES_Solve, snes, 0, 0, 0));
4908:     PetscCheck(snes->reason, PETSC_COMM_SELF, PETSC_ERR_PLIB, "Internal error, solver %s returned without setting converged reason", ((PetscObject)snes)->type_name);
4909:     snes->domainerror = PETSC_FALSE; /* clear the flag if it has been set */

4911:     if (snes->lagjac_persist) snes->jac_iter += snes->iter;
4912:     if (snes->lagpre_persist) snes->pre_iter += snes->iter;

4914:     PetscCall(PetscOptionsCreateViewer(PetscObjectComm((PetscObject)snes), ((PetscObject)snes)->options, ((PetscObject)snes)->prefix, "-snes_test_local_min", NULL, NULL, &flg));
4915:     if (flg && !PetscPreLoadingOn) PetscCall(SNESTestLocalMin(snes));
4916:     /* Call converged reason views. This may involve user-provided viewers as well */
4917:     PetscCall(SNESConvergedReasonViewFromOptions(snes));

4919:     if (snes->errorifnotconverged) PetscCheck(snes->reason >= 0, PetscObjectComm((PetscObject)snes), PETSC_ERR_NOT_CONVERGED, "SNESSolve has not converged");
4920:     if (snes->reason < 0) break;
4921:     if (grid < snes->gridsequence) {
4922:       DM  fine;
4923:       Vec xnew;
4924:       Mat interp;

4926:       PetscCall(DMRefine(snes->dm, PetscObjectComm((PetscObject)snes), &fine));
4927:       PetscCheck(fine, PetscObjectComm((PetscObject)snes), PETSC_ERR_ARG_INCOMP, "DMRefine() did not perform any refinement, cannot continue grid sequencing");
4928:       PetscCall(DMGetCoordinatesLocalSetUp(fine));
4929:       PetscCall(DMCreateInterpolation(snes->dm, fine, &interp, NULL));
4930:       PetscCall(DMCreateGlobalVector(fine, &xnew));
4931:       PetscCall(MatInterpolate(interp, x, xnew));
4932:       PetscCall(DMInterpolate(snes->dm, interp, fine));
4933:       PetscCall(MatDestroy(&interp));
4934:       x = xnew;

4936:       PetscCall(SNESReset(snes));
4937:       PetscCall(SNESSetDM(snes, fine));
4938:       PetscCall(SNESResetFromOptions(snes));
4939:       PetscCall(DMDestroy(&fine));
4940:       PetscCall(PetscViewerASCIIPopTab(PETSC_VIEWER_STDOUT_(PetscObjectComm((PetscObject)snes))));
4941:     }
4942:   }
4943:   PetscCall(SNESViewFromOptions(snes, NULL, "-snes_view"));
4944:   PetscCall(VecViewFromOptions(snes->vec_sol, (PetscObject)snes, "-snes_view_solution"));
4945:   PetscCall(DMMonitor(snes->dm));
4946:   PetscCall(SNESMonitorPauseFinal_Internal(snes));

4948:   PetscCall(VecDestroy(&xcreated));
4949:   PetscCall(PetscObjectSAWsBlock((PetscObject)snes));
4950:   PetscFunctionReturn(PETSC_SUCCESS);
4951: }

4953: /* --------- Internal routines for SNES Package --------- */

4955: /*@
4956:   SNESSetType - Sets the algorithm/method to be used to solve the nonlinear system with the given `SNES`

4958:   Collective

4960:   Input Parameters:
4961: + snes - the `SNES` context
4962: - type - a known method

4964:   Options Database Key:
4965: . -snes_type <type> - Sets the method; use -help for a list
4966:    of available methods (for instance, newtonls or newtontr)

4968:   Level: intermediate

4970:   Notes:
4971:   See `SNESType` for available methods (for instance)
4972: +    `SNESNEWTONLS` - Newton's method with line search
4973:   (systems of nonlinear equations)
4974: -    `SNESNEWTONTR` - Newton's method with trust region
4975:   (systems of nonlinear equations)

4977:   Normally, it is best to use the `SNESSetFromOptions()` command and then
4978:   set the `SNES` solver type from the options database rather than by using
4979:   this routine.  Using the options database provides the user with
4980:   maximum flexibility in evaluating the many nonlinear solvers.
4981:   The `SNESSetType()` routine is provided for those situations where it
4982:   is necessary to set the nonlinear solver independently of the command
4983:   line or options database.  This might be the case, for example, when
4984:   the choice of solver changes during the execution of the program,
4985:   and the user's application is taking responsibility for choosing the
4986:   appropriate method.

4988:   Developer Note:
4989:   `SNESRegister()` adds a constructor for a new `SNESType` to `SNESList`, `SNESSetType()` locates
4990:   the constructor in that list and calls it to create the specific object.

4992: .seealso: [](ch_snes), `SNES`, `SNESSolve()`, `SNESType`, `SNESCreate()`, `SNESDestroy()`, `SNESGetType()`, `SNESSetFromOptions()`
4993: @*/
4994: PetscErrorCode SNESSetType(SNES snes, SNESType type)
4995: {
4996:   PetscBool match;
4997:   PetscErrorCode (*r)(SNES);

4999:   PetscFunctionBegin;
5001:   PetscAssertPointer(type, 2);

5003:   PetscCall(PetscObjectTypeCompare((PetscObject)snes, type, &match));
5004:   if (match) PetscFunctionReturn(PETSC_SUCCESS);

5006:   PetscCall(PetscFunctionListFind(SNESList, type, &r));
5007:   PetscCheck(r, PetscObjectComm((PetscObject)snes), PETSC_ERR_ARG_UNKNOWN_TYPE, "Unable to find requested SNES type %s", type);
5008:   /* Destroy the previous private SNES context */
5009:   PetscTryTypeMethod(snes, destroy);
5010:   /* Reinitialize type-specific function pointers in SNESOps structure */
5011:   snes->ops->reset          = NULL;
5012:   snes->ops->setup          = NULL;
5013:   snes->ops->solve          = NULL;
5014:   snes->ops->view           = NULL;
5015:   snes->ops->setfromoptions = NULL;
5016:   snes->ops->destroy        = NULL;

5018:   /* It may happen the user has customized the line search before calling SNESSetType */
5019:   if (((PetscObject)snes)->type_name) PetscCall(SNESLineSearchDestroy(&snes->linesearch));

5021:   /* Call the SNESCreate_XXX routine for this particular Nonlinear solver */
5022:   snes->setupcalled = PETSC_FALSE;

5024:   PetscCall(PetscObjectChangeTypeName((PetscObject)snes, type));
5025:   PetscCall((*r)(snes));
5026:   PetscFunctionReturn(PETSC_SUCCESS);
5027: }

5029: /*@
5030:   SNESGetType - Gets the `SNES` method type and name (as a string).

5032:   Not Collective

5034:   Input Parameter:
5035: . snes - nonlinear solver context

5037:   Output Parameter:
5038: . type - `SNES` method (a character string)

5040:   Level: intermediate

5042: .seealso: [](ch_snes), `SNESSetType()`, `SNESType`, `SNESSetFromOptions()`, `SNES`
5043: @*/
5044: PetscErrorCode SNESGetType(SNES snes, SNESType *type)
5045: {
5046:   PetscFunctionBegin;
5048:   PetscAssertPointer(type, 2);
5049:   *type = ((PetscObject)snes)->type_name;
5050:   PetscFunctionReturn(PETSC_SUCCESS);
5051: }

5053: /*@
5054:   SNESSetSolution - Sets the solution vector for use by the `SNES` routines.

5056:   Logically Collective

5058:   Input Parameters:
5059: + snes - the `SNES` context obtained from `SNESCreate()`
5060: - u    - the solution vector

5062:   Level: beginner

5064: .seealso: [](ch_snes), `SNES`, `SNESSolve()`, `SNESGetSolution()`, `Vec`
5065: @*/
5066: PetscErrorCode SNESSetSolution(SNES snes, Vec u)
5067: {
5068:   DM dm;

5070:   PetscFunctionBegin;
5073:   PetscCall(PetscObjectReference((PetscObject)u));
5074:   PetscCall(VecDestroy(&snes->vec_sol));

5076:   snes->vec_sol = u;

5078:   PetscCall(SNESGetDM(snes, &dm));
5079:   PetscCall(DMShellSetGlobalVector(dm, u));
5080:   PetscFunctionReturn(PETSC_SUCCESS);
5081: }

5083: /*@
5084:   SNESGetSolution - Returns the vector where the approximate solution is
5085:   stored. This is the fine grid solution when using `SNESSetGridSequence()`.

5087:   Not Collective, but `x` is parallel if `snes` is parallel

5089:   Input Parameter:
5090: . snes - the `SNES` context

5092:   Output Parameter:
5093: . x - the solution

5095:   Level: intermediate

5097: .seealso: [](ch_snes), `SNESSetSolution()`, `SNESSolve()`, `SNES`, `SNESGetSolutionUpdate()`, `SNESGetFunction()`
5098: @*/
5099: PetscErrorCode SNESGetSolution(SNES snes, Vec *x)
5100: {
5101:   PetscFunctionBegin;
5103:   PetscAssertPointer(x, 2);
5104:   *x = snes->vec_sol;
5105:   PetscFunctionReturn(PETSC_SUCCESS);
5106: }

5108: /*@
5109:   SNESGetSolutionUpdate - Returns the vector where the solution update is
5110:   stored.

5112:   Not Collective, but `x` is parallel if `snes` is parallel

5114:   Input Parameter:
5115: . snes - the `SNES` context

5117:   Output Parameter:
5118: . x - the solution update

5120:   Level: advanced

5122: .seealso: [](ch_snes), `SNES`, `SNESGetSolution()`, `SNESGetFunction()`
5123: @*/
5124: PetscErrorCode SNESGetSolutionUpdate(SNES snes, Vec *x)
5125: {
5126:   PetscFunctionBegin;
5128:   PetscAssertPointer(x, 2);
5129:   *x = snes->vec_sol_update;
5130:   PetscFunctionReturn(PETSC_SUCCESS);
5131: }

5133: /*@C
5134:   SNESGetFunction - Returns the function that defines the nonlinear system set with `SNESSetFunction()`

5136:   Not Collective, but `r` is parallel if `snes` is parallel. Collective if `r` is requested, but has not been created yet.

5138:   Input Parameter:
5139: . snes - the `SNES` context

5141:   Output Parameters:
5142: + r   - the vector that is used to store residuals (or `NULL` if you don't want it)
5143: . f   - the function (or `NULL` if you don't want it);  for calling sequence see `SNESFunctionFn`
5144: - ctx - the function context (or `NULL` if you don't want it)

5146:   Level: advanced

5148:   Note:
5149:   The vector `r` DOES NOT, in general, contain the current value of the `SNES` nonlinear function

5151: .seealso: [](ch_snes), `SNES`, `SNESSolve()`, `SNESSetFunction()`, `SNESGetSolution()`, `SNESFunctionFn`
5152: @*/
5153: PetscErrorCode SNESGetFunction(SNES snes, Vec *r, SNESFunctionFn **f, void **ctx)
5154: {
5155:   DM dm;

5157:   PetscFunctionBegin;
5159:   if (r) {
5160:     if (!snes->vec_func) {
5161:       if (snes->vec_rhs) {
5162:         PetscCall(VecDuplicate(snes->vec_rhs, &snes->vec_func));
5163:       } else if (snes->vec_sol) {
5164:         PetscCall(VecDuplicate(snes->vec_sol, &snes->vec_func));
5165:       } else if (snes->dm) {
5166:         PetscCall(DMCreateGlobalVector(snes->dm, &snes->vec_func));
5167:       }
5168:     }
5169:     *r = snes->vec_func;
5170:   }
5171:   PetscCall(SNESGetDM(snes, &dm));
5172:   PetscCall(DMSNESGetFunction(dm, f, ctx));
5173:   PetscFunctionReturn(PETSC_SUCCESS);
5174: }

5176: /*@C
5177:   SNESGetNGS - Returns the function and context set with `SNESSetNGS()`

5179:   Input Parameter:
5180: . snes - the `SNES` context

5182:   Output Parameters:
5183: + f   - the function (or `NULL`) see `SNESNGSFn` for calling sequence
5184: - ctx - the function context (or `NULL`)

5186:   Level: advanced

5188: .seealso: [](ch_snes), `SNESSetNGS()`, `SNESGetFunction()`, `SNESNGSFn`
5189: @*/
5190: PetscErrorCode SNESGetNGS(SNES snes, SNESNGSFn **f, void **ctx)
5191: {
5192:   DM dm;

5194:   PetscFunctionBegin;
5196:   PetscCall(SNESGetDM(snes, &dm));
5197:   PetscCall(DMSNESGetNGS(dm, f, ctx));
5198:   PetscFunctionReturn(PETSC_SUCCESS);
5199: }

5201: /*@
5202:   SNESSetOptionsPrefix - Sets the prefix used for searching for all
5203:   `SNES` options in the database.

5205:   Logically Collective

5207:   Input Parameters:
5208: + snes   - the `SNES` context
5209: - prefix - the prefix to prepend to all option names

5211:   Level: advanced

5213:   Note:
5214:   A hyphen (-) must NOT be given at the beginning of the prefix name.
5215:   The first character of all runtime options is AUTOMATICALLY the hyphen.

5217: .seealso: [](ch_snes), `SNES`, `SNESSetFromOptions()`, `SNESAppendOptionsPrefix()`
5218: @*/
5219: PetscErrorCode SNESSetOptionsPrefix(SNES snes, const char prefix[])
5220: {
5221:   PetscFunctionBegin;
5223:   PetscCall(PetscObjectSetOptionsPrefix((PetscObject)snes, prefix));
5224:   if (!snes->ksp) PetscCall(SNESGetKSP(snes, &snes->ksp));
5225:   if (snes->linesearch) {
5226:     PetscCall(SNESGetLineSearch(snes, &snes->linesearch));
5227:     PetscCall(PetscObjectSetOptionsPrefix((PetscObject)snes->linesearch, prefix));
5228:   }
5229:   PetscCall(KSPSetOptionsPrefix(snes->ksp, prefix));
5230:   PetscFunctionReturn(PETSC_SUCCESS);
5231: }

5233: /*@
5234:   SNESAppendOptionsPrefix - Appends to the prefix used for searching for all
5235:   `SNES` options in the database.

5237:   Logically Collective

5239:   Input Parameters:
5240: + snes   - the `SNES` context
5241: - prefix - the prefix to prepend to all option names

5243:   Level: advanced

5245:   Note:
5246:   A hyphen (-) must NOT be given at the beginning of the prefix name.
5247:   The first character of all runtime options is AUTOMATICALLY the hyphen.

5249: .seealso: [](ch_snes), `SNESGetOptionsPrefix()`, `SNESSetOptionsPrefix()`
5250: @*/
5251: PetscErrorCode SNESAppendOptionsPrefix(SNES snes, const char prefix[])
5252: {
5253:   PetscFunctionBegin;
5255:   PetscCall(PetscObjectAppendOptionsPrefix((PetscObject)snes, prefix));
5256:   if (!snes->ksp) PetscCall(SNESGetKSP(snes, &snes->ksp));
5257:   if (snes->linesearch) {
5258:     PetscCall(SNESGetLineSearch(snes, &snes->linesearch));
5259:     PetscCall(PetscObjectAppendOptionsPrefix((PetscObject)snes->linesearch, prefix));
5260:   }
5261:   PetscCall(KSPAppendOptionsPrefix(snes->ksp, prefix));
5262:   PetscFunctionReturn(PETSC_SUCCESS);
5263: }

5265: /*@
5266:   SNESGetOptionsPrefix - Gets the prefix used for searching for all
5267:   `SNES` options in the database.

5269:   Not Collective

5271:   Input Parameter:
5272: . snes - the `SNES` context

5274:   Output Parameter:
5275: . prefix - pointer to the prefix string used

5277:   Level: advanced

5279: .seealso: [](ch_snes), `SNES`, `SNESSetOptionsPrefix()`, `SNESAppendOptionsPrefix()`
5280: @*/
5281: PetscErrorCode SNESGetOptionsPrefix(SNES snes, const char *prefix[])
5282: {
5283:   PetscFunctionBegin;
5285:   PetscCall(PetscObjectGetOptionsPrefix((PetscObject)snes, prefix));
5286:   PetscFunctionReturn(PETSC_SUCCESS);
5287: }

5289: /*@C
5290:   SNESRegister - Adds a method to the nonlinear solver package.

5292:   Not Collective

5294:   Input Parameters:
5295: + sname    - name of a new user-defined solver
5296: - function - routine to create method context

5298:   Level: advanced

5300:   Note:
5301:   `SNESRegister()` may be called multiple times to add several user-defined solvers.

5303:   Example Usage:
5304: .vb
5305:    SNESRegister("my_solver", MySolverCreate);
5306: .ve

5308:   Then, your solver can be chosen with the procedural interface via
5309: .vb
5310:   SNESSetType(snes, "my_solver")
5311: .ve
5312:   or at runtime via the option
5313: .vb
5314:   -snes_type my_solver
5315: .ve

5317: .seealso: [](ch_snes), `SNESRegisterAll()`, `SNESRegisterDestroy()`
5318: @*/
5319: PetscErrorCode SNESRegister(const char sname[], PetscErrorCode (*function)(SNES))
5320: {
5321:   PetscFunctionBegin;
5322:   PetscCall(SNESInitializePackage());
5323:   PetscCall(PetscFunctionListAdd(&SNESList, sname, function));
5324:   PetscFunctionReturn(PETSC_SUCCESS);
5325: }

5327: PetscErrorCode SNESTestLocalMin(SNES snes)
5328: {
5329:   PetscInt    N, i, j;
5330:   Vec         u, uh, fh;
5331:   PetscScalar value;
5332:   PetscReal   norm;

5334:   PetscFunctionBegin;
5335:   PetscCall(SNESGetSolution(snes, &u));
5336:   PetscCall(VecDuplicate(u, &uh));
5337:   PetscCall(VecDuplicate(u, &fh));

5339:   /* currently only works for sequential */
5340:   PetscCall(PetscPrintf(PetscObjectComm((PetscObject)snes), "Testing FormFunction() for local min\n"));
5341:   PetscCall(VecGetSize(u, &N));
5342:   for (i = 0; i < N; i++) {
5343:     PetscCall(VecCopy(u, uh));
5344:     PetscCall(PetscPrintf(PetscObjectComm((PetscObject)snes), "i = %" PetscInt_FMT "\n", i));
5345:     for (j = -10; j < 11; j++) {
5346:       value = PetscSign(j) * PetscExpReal(PetscAbs(j) - 10.0);
5347:       PetscCall(VecSetValue(uh, i, value, ADD_VALUES));
5348:       PetscCall(SNESComputeFunction(snes, uh, fh));
5349:       PetscCall(VecNorm(fh, NORM_2, &norm));
5350:       PetscCall(PetscPrintf(PetscObjectComm((PetscObject)snes), "       j norm %" PetscInt_FMT " %18.16e\n", j, (double)norm));
5351:       value = -value;
5352:       PetscCall(VecSetValue(uh, i, value, ADD_VALUES));
5353:     }
5354:   }
5355:   PetscCall(VecDestroy(&uh));
5356:   PetscCall(VecDestroy(&fh));
5357:   PetscFunctionReturn(PETSC_SUCCESS);
5358: }

5360: /*@
5361:   SNESKSPSetUseEW - Sets `SNES` to the use Eisenstat-Walker method for
5362:   computing relative tolerance for linear solvers within an inexact
5363:   Newton method.

5365:   Logically Collective

5367:   Input Parameters:
5368: + snes - `SNES` context
5369: - flag - `PETSC_TRUE` or `PETSC_FALSE`

5371:   Options Database Keys:
5372: + -snes_ksp_ew                       - use Eisenstat-Walker method for determining linear system convergence
5373: . -snes_ksp_ew_version ver           - version of  Eisenstat-Walker method
5374: . -snes_ksp_ew_rtol0 <rtol0>         - Sets rtol0
5375: . -snes_ksp_ew_rtolmax <rtolmax>     - Sets rtolmax
5376: . -snes_ksp_ew_gamma <gamma>         - Sets gamma
5377: . -snes_ksp_ew_alpha <alpha>         - Sets alpha
5378: . -snes_ksp_ew_alpha2 <alpha2>       - Sets alpha2
5379: - -snes_ksp_ew_threshold <threshold> - Sets threshold

5381:   Level: advanced

5383:   Note:
5384:   The default is to use a constant relative tolerance for
5385:   the inner linear solvers.  Alternatively, one can use the
5386:   Eisenstat-Walker method {cite}`ew96`, where the relative convergence tolerance
5387:   is reset at each Newton iteration according progress of the nonlinear
5388:   solver.

5390: .seealso: [](ch_snes), `KSP`, `SNES`, `SNESKSPGetUseEW()`, `SNESKSPGetParametersEW()`, `SNESKSPSetParametersEW()`
5391: @*/
5392: PetscErrorCode SNESKSPSetUseEW(SNES snes, PetscBool flag)
5393: {
5394:   PetscFunctionBegin;
5397:   snes->ksp_ewconv = flag;
5398:   PetscFunctionReturn(PETSC_SUCCESS);
5399: }

5401: /*@
5402:   SNESKSPGetUseEW - Gets if `SNES` is using Eisenstat-Walker method
5403:   for computing relative tolerance for linear solvers within an
5404:   inexact Newton method.

5406:   Not Collective

5408:   Input Parameter:
5409: . snes - `SNES` context

5411:   Output Parameter:
5412: . flag - `PETSC_TRUE` or `PETSC_FALSE`

5414:   Level: advanced

5416: .seealso: [](ch_snes), `SNESKSPSetUseEW()`, `SNESKSPGetParametersEW()`, `SNESKSPSetParametersEW()`
5417: @*/
5418: PetscErrorCode SNESKSPGetUseEW(SNES snes, PetscBool *flag)
5419: {
5420:   PetscFunctionBegin;
5422:   PetscAssertPointer(flag, 2);
5423:   *flag = snes->ksp_ewconv;
5424:   PetscFunctionReturn(PETSC_SUCCESS);
5425: }

5427: /*@
5428:   SNESKSPSetParametersEW - Sets parameters for Eisenstat-Walker
5429:   convergence criteria for the linear solvers within an inexact
5430:   Newton method.

5432:   Logically Collective

5434:   Input Parameters:
5435: + snes      - `SNES` context
5436: . version   - version 1, 2 (default is 2), 3 or 4
5437: . rtol_0    - initial relative tolerance (0 <= rtol_0 < 1)
5438: . rtol_max  - maximum relative tolerance (0 <= rtol_max < 1)
5439: . gamma     - multiplicative factor for version 2 rtol computation
5440:              (0 <= gamma2 <= 1)
5441: . alpha     - power for version 2 rtol computation (1 < alpha <= 2)
5442: . alpha2    - power for safeguard
5443: - threshold - threshold for imposing safeguard (0 < threshold < 1)

5445:   Level: advanced

5447:   Notes:
5448:   Version 3 was contributed by Luis Chacon, June 2006.

5450:   Use `PETSC_CURRENT` to retain the default for any of the parameters.

5452: .seealso: [](ch_snes), `SNES`, `SNESKSPSetUseEW()`, `SNESKSPGetUseEW()`, `SNESKSPGetParametersEW()`
5453: @*/
5454: PetscErrorCode SNESKSPSetParametersEW(SNES snes, PetscInt version, PetscReal rtol_0, PetscReal rtol_max, PetscReal gamma, PetscReal alpha, PetscReal alpha2, PetscReal threshold)
5455: {
5456:   SNESKSPEW *kctx;

5458:   PetscFunctionBegin;
5460:   kctx = (SNESKSPEW *)snes->kspconvctx;
5461:   PetscCheck(kctx, PETSC_COMM_SELF, PETSC_ERR_ARG_WRONGSTATE, "No Eisenstat-Walker context existing");

5470:   if (version != PETSC_CURRENT) kctx->version = version;
5471:   if (rtol_0 != (PetscReal)PETSC_CURRENT) kctx->rtol_0 = rtol_0;
5472:   if (rtol_max != (PetscReal)PETSC_CURRENT) kctx->rtol_max = rtol_max;
5473:   if (gamma != (PetscReal)PETSC_CURRENT) kctx->gamma = gamma;
5474:   if (alpha != (PetscReal)PETSC_CURRENT) kctx->alpha = alpha;
5475:   if (alpha2 != (PetscReal)PETSC_CURRENT) kctx->alpha2 = alpha2;
5476:   if (threshold != (PetscReal)PETSC_CURRENT) kctx->threshold = threshold;

5478:   PetscCheck(kctx->version >= 1 && kctx->version <= 4, PETSC_COMM_SELF, PETSC_ERR_ARG_OUTOFRANGE, "Only versions 1 to 4 are supported: %" PetscInt_FMT, kctx->version);
5479:   PetscCheck(kctx->rtol_0 >= 0.0 && kctx->rtol_0 < 1.0, PETSC_COMM_SELF, PETSC_ERR_ARG_OUTOFRANGE, "0.0 <= rtol_0 < 1.0: %g", (double)kctx->rtol_0);
5480:   PetscCheck(kctx->rtol_max >= 0.0 && kctx->rtol_max < 1.0, PETSC_COMM_SELF, PETSC_ERR_ARG_OUTOFRANGE, "0.0 <= rtol_max (%g) < 1.0", (double)kctx->rtol_max);
5481:   PetscCheck(kctx->gamma >= 0.0 && kctx->gamma <= 1.0, PETSC_COMM_SELF, PETSC_ERR_ARG_OUTOFRANGE, "0.0 <= gamma (%g) <= 1.0", (double)kctx->gamma);
5482:   PetscCheck(kctx->alpha > 1.0 && kctx->alpha <= 2.0, PETSC_COMM_SELF, PETSC_ERR_ARG_OUTOFRANGE, "1.0 < alpha (%g) <= 2.0", (double)kctx->alpha);
5483:   PetscCheck(kctx->threshold > 0.0 && kctx->threshold < 1.0, PETSC_COMM_SELF, PETSC_ERR_ARG_OUTOFRANGE, "0.0 < threshold (%g) < 1.0", (double)kctx->threshold);
5484:   PetscFunctionReturn(PETSC_SUCCESS);
5485: }

5487: /*@
5488:   SNESKSPGetParametersEW - Gets parameters for Eisenstat-Walker
5489:   convergence criteria for the linear solvers within an inexact
5490:   Newton method.

5492:   Not Collective

5494:   Input Parameter:
5495: . snes - `SNES` context

5497:   Output Parameters:
5498: + version   - version 1, 2 (default is 2), 3 or 4
5499: . rtol_0    - initial relative tolerance (0 <= rtol_0 < 1)
5500: . rtol_max  - maximum relative tolerance (0 <= rtol_max < 1)
5501: . gamma     - multiplicative factor for version 2 rtol computation (0 <= gamma2 <= 1)
5502: . alpha     - power for version 2 rtol computation (1 < alpha <= 2)
5503: . alpha2    - power for safeguard
5504: - threshold - threshold for imposing safeguard (0 < threshold < 1)

5506:   Level: advanced

5508: .seealso: [](ch_snes), `SNES`, `SNESKSPSetUseEW()`, `SNESKSPGetUseEW()`, `SNESKSPSetParametersEW()`
5509: @*/
5510: PetscErrorCode SNESKSPGetParametersEW(SNES snes, PetscInt *version, PetscReal *rtol_0, PetscReal *rtol_max, PetscReal *gamma, PetscReal *alpha, PetscReal *alpha2, PetscReal *threshold)
5511: {
5512:   SNESKSPEW *kctx;

5514:   PetscFunctionBegin;
5516:   kctx = (SNESKSPEW *)snes->kspconvctx;
5517:   PetscCheck(kctx, PETSC_COMM_SELF, PETSC_ERR_ARG_WRONGSTATE, "No Eisenstat-Walker context existing");
5518:   if (version) *version = kctx->version;
5519:   if (rtol_0) *rtol_0 = kctx->rtol_0;
5520:   if (rtol_max) *rtol_max = kctx->rtol_max;
5521:   if (gamma) *gamma = kctx->gamma;
5522:   if (alpha) *alpha = kctx->alpha;
5523:   if (alpha2) *alpha2 = kctx->alpha2;
5524:   if (threshold) *threshold = kctx->threshold;
5525:   PetscFunctionReturn(PETSC_SUCCESS);
5526: }

5528: PetscErrorCode KSPPreSolve_SNESEW(KSP ksp, Vec b, Vec x, void *ctx)
5529: {
5530:   SNES       snes = (SNES)ctx;
5531:   SNESKSPEW *kctx = (SNESKSPEW *)snes->kspconvctx;
5532:   PetscReal  rtol = PETSC_CURRENT, stol;

5534:   PetscFunctionBegin;
5535:   if (!snes->ksp_ewconv) PetscFunctionReturn(PETSC_SUCCESS);
5536:   if (!snes->iter) {
5537:     rtol = kctx->rtol_0; /* first time in, so use the original user rtol */
5538:     PetscCall(VecNorm(snes->vec_func, NORM_2, &kctx->norm_first));
5539:   } else {
5540:     PetscCheck(kctx->version >= 1 && kctx->version <= 4, PETSC_COMM_SELF, PETSC_ERR_ARG_OUTOFRANGE, "Only versions 1-4 are supported: %" PetscInt_FMT, kctx->version);
5541:     if (kctx->version == 1) {
5542:       rtol = PetscAbsReal(snes->norm - kctx->lresid_last) / kctx->norm_last;
5543:       stol = PetscPowReal(kctx->rtol_last, kctx->alpha2);
5544:       if (stol > kctx->threshold) rtol = PetscMax(rtol, stol);
5545:     } else if (kctx->version == 2) {
5546:       rtol = kctx->gamma * PetscPowReal(snes->norm / kctx->norm_last, kctx->alpha);
5547:       stol = kctx->gamma * PetscPowReal(kctx->rtol_last, kctx->alpha);
5548:       if (stol > kctx->threshold) rtol = PetscMax(rtol, stol);
5549:     } else if (kctx->version == 3) { /* contributed by Luis Chacon, June 2006. */
5550:       rtol = kctx->gamma * PetscPowReal(snes->norm / kctx->norm_last, kctx->alpha);
5551:       /* safeguard: avoid sharp decrease of rtol */
5552:       stol = kctx->gamma * PetscPowReal(kctx->rtol_last, kctx->alpha);
5553:       stol = PetscMax(rtol, stol);
5554:       rtol = PetscMin(kctx->rtol_0, stol);
5555:       /* safeguard: avoid oversolving */
5556:       stol = kctx->gamma * (kctx->norm_first * snes->rtol) / snes->norm;
5557:       stol = PetscMax(rtol, stol);
5558:       rtol = PetscMin(kctx->rtol_0, stol);
5559:     } else /* if (kctx->version == 4) */ {
5560:       /* H.-B. An et al. Journal of Computational and Applied Mathematics 200 (2007) 47-60 */
5561:       PetscReal ared = PetscAbsReal(kctx->norm_last - snes->norm);
5562:       PetscReal pred = PetscAbsReal(kctx->norm_last - kctx->lresid_last);
5563:       PetscReal rk   = ared / pred;
5564:       if (rk < kctx->v4_p1) rtol = 1. - 2. * kctx->v4_p1;
5565:       else if (rk < kctx->v4_p2) rtol = kctx->rtol_last;
5566:       else if (rk < kctx->v4_p3) rtol = kctx->v4_m1 * kctx->rtol_last;
5567:       else rtol = kctx->v4_m2 * kctx->rtol_last;

5569:       if (kctx->rtol_last_2 > kctx->v4_m3 && kctx->rtol_last > kctx->v4_m3 && kctx->rk_last_2 < kctx->v4_p1 && kctx->rk_last < kctx->v4_p1) rtol = kctx->v4_m4 * kctx->rtol_last;
5570:       kctx->rtol_last_2 = kctx->rtol_last;
5571:       kctx->rk_last_2   = kctx->rk_last;
5572:       kctx->rk_last     = rk;
5573:     }
5574:   }
5575:   /* safeguard: avoid rtol greater than rtol_max */
5576:   rtol = PetscMin(rtol, kctx->rtol_max);
5577:   PetscCall(KSPSetTolerances(ksp, rtol, PETSC_CURRENT, PETSC_CURRENT, PETSC_CURRENT));
5578:   PetscCall(PetscInfo(snes, "iter %" PetscInt_FMT ", Eisenstat-Walker (version %" PetscInt_FMT ") KSP rtol=%g\n", snes->iter, kctx->version, (double)rtol));
5579:   PetscFunctionReturn(PETSC_SUCCESS);
5580: }

5582: PetscErrorCode KSPPostSolve_SNESEW(KSP ksp, Vec b, Vec x, void *ctx)
5583: {
5584:   SNES       snes = (SNES)ctx;
5585:   SNESKSPEW *kctx = (SNESKSPEW *)snes->kspconvctx;
5586:   PCSide     pcside;
5587:   Vec        lres;

5589:   PetscFunctionBegin;
5590:   if (!snes->ksp_ewconv) PetscFunctionReturn(PETSC_SUCCESS);
5591:   PetscCall(KSPGetTolerances(ksp, &kctx->rtol_last, NULL, NULL, NULL));
5592:   kctx->norm_last = snes->norm;
5593:   if (kctx->version == 1 || kctx->version == 4) {
5594:     PC        pc;
5595:     PetscBool getRes;

5597:     PetscCall(KSPGetPC(ksp, &pc));
5598:     PetscCall(PetscObjectTypeCompare((PetscObject)pc, PCNONE, &getRes));
5599:     if (!getRes) {
5600:       KSPNormType normtype;

5602:       PetscCall(KSPGetNormType(ksp, &normtype));
5603:       getRes = (PetscBool)(normtype == KSP_NORM_UNPRECONDITIONED);
5604:     }
5605:     PetscCall(KSPGetPCSide(ksp, &pcside));
5606:     if (pcside == PC_RIGHT || getRes) { /* KSP residual is true linear residual */
5607:       PetscCall(KSPGetResidualNorm(ksp, &kctx->lresid_last));
5608:     } else {
5609:       /* KSP residual is preconditioned residual */
5610:       /* compute true linear residual norm */
5611:       Mat J;
5612:       PetscCall(KSPGetOperators(ksp, &J, NULL));
5613:       PetscCall(VecDuplicate(b, &lres));
5614:       PetscCall(MatMult(J, x, lres));
5615:       PetscCall(VecAYPX(lres, -1.0, b));
5616:       PetscCall(VecNorm(lres, NORM_2, &kctx->lresid_last));
5617:       PetscCall(VecDestroy(&lres));
5618:     }
5619:   }
5620:   PetscFunctionReturn(PETSC_SUCCESS);
5621: }

5623: /*@
5624:   SNESGetKSP - Returns the `KSP` context for a `SNES` solver.

5626:   Not Collective, but if `snes` is parallel, then `ksp` is parallel

5628:   Input Parameter:
5629: . snes - the `SNES` context

5631:   Output Parameter:
5632: . ksp - the `KSP` context

5634:   Level: beginner

5636:   Notes:
5637:   The user can then directly manipulate the `KSP` context to set various
5638:   options, etc.  Likewise, the user can then extract and manipulate the
5639:   `PC` contexts as well.

5641:   Some `SNESType`s do not use a `KSP` but a `KSP` is still returned by this function, changes to that `KSP` will have no effect.

5643: .seealso: [](ch_snes), `SNES`, `KSP`, `PC`, `KSPGetPC()`, `SNESCreate()`, `KSPCreate()`, `SNESSetKSP()`
5644: @*/
5645: PetscErrorCode SNESGetKSP(SNES snes, KSP *ksp)
5646: {
5647:   PetscFunctionBegin;
5649:   PetscAssertPointer(ksp, 2);

5651:   if (!snes->ksp) {
5652:     PetscCall(KSPCreate(PetscObjectComm((PetscObject)snes), &snes->ksp));
5653:     PetscCall(PetscObjectIncrementTabLevel((PetscObject)snes->ksp, (PetscObject)snes, 1));

5655:     PetscCall(KSPSetPreSolve(snes->ksp, KSPPreSolve_SNESEW, snes));
5656:     PetscCall(KSPSetPostSolve(snes->ksp, KSPPostSolve_SNESEW, snes));

5658:     PetscCall(KSPMonitorSetFromOptions(snes->ksp, "-snes_monitor_ksp", "snes_preconditioned_residual", snes));
5659:     PetscCall(PetscObjectSetOptions((PetscObject)snes->ksp, ((PetscObject)snes)->options));
5660:   }
5661:   *ksp = snes->ksp;
5662:   PetscFunctionReturn(PETSC_SUCCESS);
5663: }

5665: #include <petsc/private/dmimpl.h>
5666: /*@
5667:   SNESSetDM - Sets the `DM` that may be used by some `SNES` nonlinear solvers or their underlying preconditioners

5669:   Logically Collective

5671:   Input Parameters:
5672: + snes - the nonlinear solver context
5673: - dm   - the `DM`, cannot be `NULL`

5675:   Level: intermediate

5677:   Note:
5678:   A `DM` can only be used for solving one problem at a time because information about the problem is stored on the `DM`,
5679:   even when not using interfaces like `DMSNESSetFunction()`.  Use `DMClone()` to get a distinct `DM` when solving different
5680:   problems using the same function space.

5682: .seealso: [](ch_snes), `DM`, `SNES`, `SNESGetDM()`, `KSPSetDM()`, `KSPGetDM()`
5683: @*/
5684: PetscErrorCode SNESSetDM(SNES snes, DM dm)
5685: {
5686:   KSP    ksp;
5687:   DMSNES sdm;

5689:   PetscFunctionBegin;
5692:   PetscCall(PetscObjectReference((PetscObject)dm));
5693:   if (snes->dm) { /* Move the DMSNES context over to the new DM unless the new DM already has one */
5694:     if (snes->dm->dmsnes && !dm->dmsnes) {
5695:       PetscCall(DMCopyDMSNES(snes->dm, dm));
5696:       PetscCall(DMGetDMSNES(snes->dm, &sdm));
5697:       if (sdm->originaldm == snes->dm) sdm->originaldm = dm; /* Grant write privileges to the replacement DM */
5698:     }
5699:     PetscCall(DMCoarsenHookRemove(snes->dm, DMCoarsenHook_SNESVecSol, DMRestrictHook_SNESVecSol, snes));
5700:     PetscCall(DMDestroy(&snes->dm));
5701:   }
5702:   snes->dm     = dm;
5703:   snes->dmAuto = PETSC_FALSE;

5705:   PetscCall(SNESGetKSP(snes, &ksp));
5706:   PetscCall(KSPSetDM(ksp, dm));
5707:   PetscCall(KSPSetDMActive(ksp, PETSC_FALSE));
5708:   if (snes->npc) {
5709:     PetscCall(SNESSetDM(snes->npc, snes->dm));
5710:     PetscCall(SNESSetNPCSide(snes, snes->npcside));
5711:   }
5712:   PetscFunctionReturn(PETSC_SUCCESS);
5713: }

5715: /*@
5716:   SNESGetDM - Gets the `DM` that may be used by some `SNES` nonlinear solvers/preconditioners

5718:   Not Collective but `dm` obtained is parallel on `snes`

5720:   Input Parameter:
5721: . snes - the `SNES` context

5723:   Output Parameter:
5724: . dm - the `DM`

5726:   Level: intermediate

5728: .seealso: [](ch_snes), `DM`, `SNES`, `SNESSetDM()`, `KSPSetDM()`, `KSPGetDM()`
5729: @*/
5730: PetscErrorCode SNESGetDM(SNES snes, DM *dm)
5731: {
5732:   PetscFunctionBegin;
5734:   if (!snes->dm) {
5735:     PetscCall(DMShellCreate(PetscObjectComm((PetscObject)snes), &snes->dm));
5736:     snes->dmAuto = PETSC_TRUE;
5737:   }
5738:   *dm = snes->dm;
5739:   PetscFunctionReturn(PETSC_SUCCESS);
5740: }

5742: /*@
5743:   SNESSetNPC - Sets the nonlinear preconditioner to be used.

5745:   Collective

5747:   Input Parameters:
5748: + snes - iterative context obtained from `SNESCreate()`
5749: - npc  - the `SNES` nonlinear preconditioner object

5751:   Options Database Key:
5752: . -npc_snes_type <type> - set the type of the `SNES` to use as the nonlinear preconditioner

5754:   Level: developer

5756:   Notes:
5757:   This is rarely used, rather use `SNESGetNPC()` to retrieve the preconditioner and configure it using the API.

5759:   Only some `SNESType` can use a nonlinear preconditioner

5761: .seealso: [](ch_snes), `SNES`, `SNESNGS`, `SNESFAS`, `SNESGetNPC()`, `SNESHasNPC()`
5762: @*/
5763: PetscErrorCode SNESSetNPC(SNES snes, SNES npc)
5764: {
5765:   PetscFunctionBegin;
5768:   PetscCheckSameComm(snes, 1, npc, 2);
5769:   PetscCall(PetscObjectReference((PetscObject)npc));
5770:   PetscCall(SNESDestroy(&snes->npc));
5771:   snes->npc = npc;
5772:   PetscFunctionReturn(PETSC_SUCCESS);
5773: }

5775: /*@
5776:   SNESGetNPC - Gets a nonlinear preconditioning solver SNES` to be used to precondition the original nonlinear solver.

5778:   Not Collective; but any changes to the obtained the `pc` object must be applied collectively

5780:   Input Parameter:
5781: . snes - iterative context obtained from `SNESCreate()`

5783:   Output Parameter:
5784: . pc - the `SNES` preconditioner context

5786:   Options Database Key:
5787: . -npc_snes_type <type> - set the type of the `SNES` to use as the nonlinear preconditioner

5789:   Level: advanced

5791:   Notes:
5792:   If a `SNES` was previously set with `SNESSetNPC()` then that value is returned, otherwise a new `SNES` object is created that will
5793:   be used as the nonlinear preconditioner for the current `SNES`.

5795:   The (preconditioner) `SNES` returned automatically inherits the same nonlinear function and Jacobian supplied to the original
5796:   `SNES`. These may be overwritten if needed.

5798:   Use the options database prefixes `-npc_snes`, `-npc_ksp`, etc., to control the configuration of the nonlinear preconditioner

5800: .seealso: [](ch_snes), `SNESSetNPC()`, `SNESHasNPC()`, `SNES`, `SNESCreate()`
5801: @*/
5802: PetscErrorCode SNESGetNPC(SNES snes, SNES *pc)
5803: {
5804:   const char *optionsprefix;

5806:   PetscFunctionBegin;
5808:   PetscAssertPointer(pc, 2);
5809:   if (!snes->npc) {
5810:     void *ctx;

5812:     PetscCall(SNESCreate(PetscObjectComm((PetscObject)snes), &snes->npc));
5813:     PetscCall(PetscObjectIncrementTabLevel((PetscObject)snes->npc, (PetscObject)snes, 1));
5814:     PetscCall(SNESGetOptionsPrefix(snes, &optionsprefix));
5815:     PetscCall(SNESSetOptionsPrefix(snes->npc, optionsprefix));
5816:     PetscCall(SNESAppendOptionsPrefix(snes->npc, "npc_"));
5817:     if (snes->ops->usercompute) {
5818:       PetscCall(SNESSetComputeApplicationContext(snes, snes->ops->usercompute, snes->ops->ctxdestroy));
5819:     } else {
5820:       PetscCall(SNESGetApplicationContext(snes, &ctx));
5821:       PetscCall(SNESSetApplicationContext(snes->npc, ctx));
5822:     }
5823:     PetscCall(SNESSetCountersReset(snes->npc, PETSC_FALSE));
5824:   }
5825:   *pc = snes->npc;
5826:   PetscFunctionReturn(PETSC_SUCCESS);
5827: }

5829: /*@
5830:   SNESHasNPC - Returns whether a nonlinear preconditioner is associated with the given `SNES`

5832:   Not Collective

5834:   Input Parameter:
5835: . snes - iterative context obtained from `SNESCreate()`

5837:   Output Parameter:
5838: . has_npc - whether the `SNES` has a nonlinear preconditioner or not

5840:   Level: developer

5842: .seealso: [](ch_snes), `SNESSetNPC()`, `SNESGetNPC()`
5843: @*/
5844: PetscErrorCode SNESHasNPC(SNES snes, PetscBool *has_npc)
5845: {
5846:   PetscFunctionBegin;
5848:   PetscAssertPointer(has_npc, 2);
5849:   *has_npc = snes->npc ? PETSC_TRUE : PETSC_FALSE;
5850:   PetscFunctionReturn(PETSC_SUCCESS);
5851: }

5853: /*@
5854:   SNESSetNPCSide - Sets the nonlinear preconditioning side used by the nonlinear preconditioner inside `SNES`.

5856:   Logically Collective

5858:   Input Parameter:
5859: . snes - iterative context obtained from `SNESCreate()`

5861:   Output Parameter:
5862: . side - the preconditioning side, where side is one of
5863: .vb
5864:       PC_LEFT  - left preconditioning
5865:       PC_RIGHT - right preconditioning (default for most nonlinear solvers)
5866: .ve

5868:   Options Database Key:
5869: . -snes_npc_side <right,left> - nonlinear preconditioner side

5871:   Level: intermediate

5873:   Note:
5874:   `SNESNRICHARDSON` and `SNESNCG` only support left preconditioning.

5876: .seealso: [](ch_snes), `SNES`, `SNESGetNPC()`, `SNESNRICHARDSON`, `SNESNCG`, `SNESType`, `SNESGetNPCSide()`, `KSPSetPCSide()`, `PC_LEFT`, `PC_RIGHT`, `PCSide`
5877: @*/
5878: PetscErrorCode SNESSetNPCSide(SNES snes, PCSide side)
5879: {
5880:   PetscFunctionBegin;
5883:   if (side == PC_SIDE_DEFAULT) side = PC_RIGHT;
5884:   PetscCheck((side == PC_LEFT) || (side == PC_RIGHT), PetscObjectComm((PetscObject)snes), PETSC_ERR_ARG_WRONG, "Only PC_LEFT and PC_RIGHT are supported");
5885:   snes->npcside = side;
5886:   PetscFunctionReturn(PETSC_SUCCESS);
5887: }

5889: /*@
5890:   SNESGetNPCSide - Gets the preconditioning side used by the nonlinear preconditioner inside `SNES`.

5892:   Not Collective

5894:   Input Parameter:
5895: . snes - iterative context obtained from `SNESCreate()`

5897:   Output Parameter:
5898: . side - the preconditioning side, where side is one of
5899: .vb
5900:       `PC_LEFT` - left preconditioning
5901:       `PC_RIGHT` - right preconditioning (default for most nonlinear solvers)
5902: .ve

5904:   Level: intermediate

5906: .seealso: [](ch_snes), `SNES`, `SNESGetNPC()`, `SNESSetNPCSide()`, `KSPGetPCSide()`, `PC_LEFT`, `PC_RIGHT`, `PCSide`
5907: @*/
5908: PetscErrorCode SNESGetNPCSide(SNES snes, PCSide *side)
5909: {
5910:   PetscFunctionBegin;
5912:   PetscAssertPointer(side, 2);
5913:   *side = snes->npcside;
5914:   PetscFunctionReturn(PETSC_SUCCESS);
5915: }

5917: /*@
5918:   SNESSetLineSearch - Sets the `SNESLineSearch` to be used for a given `SNES`

5920:   Collective

5922:   Input Parameters:
5923: + snes       - iterative context obtained from `SNESCreate()`
5924: - linesearch - the linesearch object

5926:   Level: developer

5928:   Note:
5929:   This is almost never used, rather one uses `SNESGetLineSearch()` to retrieve the line search and set options on it
5930:   to configure it using the API).

5932: .seealso: [](ch_snes), `SNES`, `SNESLineSearch`, `SNESGetLineSearch()`
5933: @*/
5934: PetscErrorCode SNESSetLineSearch(SNES snes, SNESLineSearch linesearch)
5935: {
5936:   PetscFunctionBegin;
5939:   PetscCheckSameComm(snes, 1, linesearch, 2);
5940:   PetscCall(PetscObjectReference((PetscObject)linesearch));
5941:   PetscCall(SNESLineSearchDestroy(&snes->linesearch));

5943:   snes->linesearch = linesearch;
5944:   PetscFunctionReturn(PETSC_SUCCESS);
5945: }

5947: /*@
5948:   SNESGetLineSearch - Returns the line search associated with the `SNES`.

5950:   Not Collective

5952:   Input Parameter:
5953: . snes - iterative context obtained from `SNESCreate()`

5955:   Output Parameter:
5956: . linesearch - linesearch context

5958:   Level: beginner

5960:   Notes:
5961:   It creates a default line search instance which can be configured as needed in case it has not been already set with `SNESSetLineSearch()`.

5963:   You can also use the options database keys `-snes_linesearch_*` to configure the line search. See `SNESLineSearchSetFromOptions()` for the possible options.

5965: .seealso: [](ch_snes), `SNESLineSearch`, `SNESSetLineSearch()`, `SNESLineSearchCreate()`, `SNESLineSearchSetFromOptions()`
5966: @*/
5967: PetscErrorCode SNESGetLineSearch(SNES snes, SNESLineSearch *linesearch)
5968: {
5969:   const char *optionsprefix;

5971:   PetscFunctionBegin;
5973:   PetscAssertPointer(linesearch, 2);
5974:   if (!snes->linesearch) {
5975:     PetscCall(SNESGetOptionsPrefix(snes, &optionsprefix));
5976:     PetscCall(SNESLineSearchCreate(PetscObjectComm((PetscObject)snes), &snes->linesearch));
5977:     PetscCall(SNESLineSearchSetSNES(snes->linesearch, snes));
5978:     PetscCall(SNESLineSearchAppendOptionsPrefix(snes->linesearch, optionsprefix));
5979:     PetscCall(PetscObjectIncrementTabLevel((PetscObject)snes->linesearch, (PetscObject)snes, 1));
5980:   }
5981:   *linesearch = snes->linesearch;
5982:   PetscFunctionReturn(PETSC_SUCCESS);
5983: }