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:   snes->domainerror = PETSC_TRUE;
151:   PetscFunctionReturn(PETSC_SUCCESS);
152: }

154: /*@
155:   SNESSetJacobianDomainError - tells `SNES` that the function you provided to `SNESSetJacobian()` at the proposed step. For example there is a negative element transformation.

157:   Logically Collective

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

162:   Level: advanced

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

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

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

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

184: /*@
185:   SNESSetCheckJacobianDomainError - tells `SNESSolve()` whether to check if the user called `SNESSetJacobianDomainError()` Jacobian domain error after
186:   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.

188:   Logically Collective

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

194:   Level: advanced

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

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

209: /*@
210:   SNESGetCheckJacobianDomainError - Get an indicator whether or not `SNES` is checking Jacobian domain errors after each Jacobian evaluation.

212:   Logically Collective

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

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

220:   Level: advanced

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

233: /*@
234:   SNESGetFunctionDomainError - Gets the status of the domain error after a call to `SNESComputeFunction()`

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

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

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

244:   Level: developer

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

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

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

262: /*@
263:   SNESGetJacobianDomainError - Gets the status of the Jacobian domain error after a call to `SNESComputeJacobian()`

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

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

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

273:   Level: advanced

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

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

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

291: /*@
292:   SNESLoad - Loads a `SNES` that has been stored in `PETSCVIEWERBINARY` with `SNESView()`.

294:   Collective

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

301:   Level: intermediate

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

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

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

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

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

341: /*@
342:   SNESViewFromOptions - View a `SNES` based on values in the options database

344:   Collective

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

351:   Level: intermediate

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

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

365: /*@
366:   SNESView - Prints or visualizes the `SNES` data structure.

368:   Collective

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

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

377:   Level: beginner

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

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

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

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

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

409:   PetscFunctionBegin;
411:   if (!viewer) PetscCall(PetscViewerASCIIGetStdout(PetscObjectComm((PetscObject)snes), &viewer));
413:   PetscCheckSameComm(snes, 1, viewer, 2);

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

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

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

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

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

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

567: /*
568:   We retain a list of functions that also take SNES command
569:   line options. These are called at the end SNESSetFromOptions()
570: */
571: #define MAXSETFROMOPTIONS 5
572: static PetscInt numberofsetfromoptions;
573: static PetscErrorCode (*othersetfromoptions[MAXSETFROMOPTIONS])(SNES);

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

578:   Not Collective

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

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

586:   Level: developer

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

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

603:   PetscFunctionBegin;

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

754: /*@
755:   SNESSetUpMatrices - ensures that matrices are available for `SNES` Newton-like methods, this is called by `SNESSetUp_XXX()`

757:   Collective

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

762:   Level: developer

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

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

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

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

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

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

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

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

838:   Collective

840:   Input Parameters:
841: + snes         - `SNES` object you wish to monitor
842: . name         - the monitor type one is seeking
843: . help         - message indicating what monitoring is done
844: . manual       - manual page for the monitor
845: . monitor      - the monitor function, this must use a `PetscViewerFormat` as its context
846: - 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

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

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

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

861:   Level: advanced

863: .seealso: [](ch_snes), `PetscOptionsCreateViewer()`, `PetscOptionsGetReal()`, `PetscOptionsHasName()`, `PetscOptionsGetString()`,
864:           `PetscOptionsGetIntArray()`, `PetscOptionsGetRealArray()`, `PetscOptionsBool()`
865:           `PetscOptionsInt()`, `PetscOptionsString()`, `PetscOptionsReal()`,
866:           `PetscOptionsName()`, `PetscOptionsBegin()`, `PetscOptionsEnd()`, `PetscOptionsHeadBegin()`,
867:           `PetscOptionsStringArray()`, `PetscOptionsRealArray()`, `PetscOptionsScalar()`,
868:           `PetscOptionsBoolGroupBegin()`, `PetscOptionsBoolGroup()`, `PetscOptionsBoolGroupEnd()`,
869:           `PetscOptionsFList()`, `PetscOptionsEList()`
870: @*/
871: 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))
872: {
873:   PetscViewer       viewer;
874:   PetscViewerFormat format;
875:   PetscBool         flg;

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

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

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

914: /*@
915:   SNESSetFromOptions - Sets various `SNES` and `KSP` parameters from user options.

917:   Collective

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

922:   Options Database Keys:
923: + -snes_type <type>                                                            - newtonls, newtontr, ngmres, ncg, nrichardson, qn, vi, fas, `SNESType` for complete list
924: . -snes_rtol <rtol>                                                            - relative decrease in tolerance norm from initial
925: . -snes_atol <abstol>                                                          - absolute tolerance of residual norm
926: . -snes_stol <stol>                                                            - convergence tolerance in terms of the norm of the change in the solution between steps
927: . -snes_divergence_tolerance <divtol>                                          - if the residual goes above divtol*rnorm0, exit with divergence
928: . -snes_max_it <max_it>                                                        - maximum number of iterations
929: . -snes_max_funcs <max_funcs>                                                  - maximum number of function evaluations
930: . -snes_force_iteration <force>                                                - force `SNESSolve()` to take at least one iteration
931: . -snes_max_fail <max_fail>                                                    - maximum number of line search failures allowed before stopping, default is none
932: . -snes_max_linear_solve_fail                                                  - number of linear solver failures before SNESSolve() stops
933: . -snes_lag_preconditioner <lag>                                               - how often preconditioner is rebuilt (use -1 to never rebuild)
934: . -snes_lag_preconditioner_persists <true,false>                               - retains the -snes_lag_preconditioner information across multiple SNESSolve()
935: . -snes_lag_jacobian <lag>                                                     - how often Jacobian is rebuilt (use -1 to never rebuild)
936: . -snes_lag_jacobian_persists <true,false>                                     - retains the -snes_lag_jacobian information across multiple SNESSolve()
937: . -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.
938: . -snes_monitor [ascii][:filename][:viewer format]                             - prints residual norm at each iteration. if no filename given prints to stdout
939: . -snes_monitor_solution [ascii binary draw][:filename][:viewer format]        - plots solution at each iteration
940: . -snes_monitor_residual [ascii binary draw][:filename][:viewer format]        - plots residual (not its norm) at each iteration
941: . -snes_monitor_solution_update [ascii binary draw][:filename][:viewer format] - plots update to solution at each iteration
942: . -snes_monitor_lg_residualnorm                                                - plots residual norm at each iteration
943: . -snes_monitor_lg_range                                                       - plots residual norm at each iteration
944: . -snes_monitor_pause_final                                                    - Pauses all monitor drawing after the solver ends
945: . -snes_fd                                                                     - use finite differences to compute Jacobian; very slow, only for testing
946: . -snes_fd_color                                                               - use finite differences with coloring to compute Jacobian
947: . -snes_mf_ksp_monitor                                                         - if using matrix-free multiply then print h at each `KSP` iteration
948: . -snes_converged_reason                                                       - print the reason for convergence/divergence after each solve
949: . -npc_snes_type <type>                                                        - the `SNES` type to use as a nonlinear preconditioner
950: . -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.
951: - -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.

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

963:   Level: beginner

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

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

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

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

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

1010:   PetscCall(PetscOptionsReal("-snes_divergence_tolerance", "Stop if residual norm increases by this factor", "SNESSetDivergenceTolerance", snes->divtol, &snes->divtol, &flg));
1011:   if (flg) PetscCall(SNESSetDivergenceTolerance(snes, snes->divtol));

1013:   PetscCall(PetscOptionsInt("-snes_max_fail", "Maximum nonlinear step failures", "SNESSetMaxNonlinearStepFailures", snes->maxFailures, &snes->maxFailures, &flg));
1014:   if (flg) PetscCall(SNESSetMaxNonlinearStepFailures(snes, snes->maxFailures));

1016:   PetscCall(PetscOptionsInt("-snes_max_linear_solve_fail", "Maximum failures in linear solves allowed", "SNESSetMaxLinearSolveFailures", snes->maxLinearSolveFailures, &snes->maxLinearSolveFailures, &flg));
1017:   if (flg) PetscCall(SNESSetMaxLinearSolveFailures(snes, snes->maxLinearSolveFailures));

1019:   PetscCall(PetscOptionsBool("-snes_error_if_not_converged", "Generate error if solver does not converge", "SNESSetErrorIfNotConverged", snes->errorifnotconverged, &snes->errorifnotconverged, NULL));
1020:   PetscCall(PetscOptionsBool("-snes_force_iteration", "Force SNESSolve() to take at least one iteration", "SNESSetForceIteration", snes->forceiteration, &snes->forceiteration, NULL));
1021:   PetscCall(PetscOptionsBool("-snes_check_jacobian_domain_error", "Check Jacobian domain error after Jacobian evaluation", "SNESCheckJacobianDomainError", snes->checkjacdomainerror, &snes->checkjacdomainerror, NULL));

1023:   PetscCall(PetscOptionsInt("-snes_lag_preconditioner", "How often to rebuild preconditioner", "SNESSetLagPreconditioner", snes->lagpreconditioner, &lag, &flg));
1024:   if (flg) {
1025:     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");
1026:     PetscCall(SNESSetLagPreconditioner(snes, lag));
1027:   }
1028:   PetscCall(PetscOptionsBool("-snes_lag_preconditioner_persists", "Preconditioner lagging through multiple SNES solves", "SNESSetLagPreconditionerPersists", snes->lagjac_persist, &persist, &flg));
1029:   if (flg) PetscCall(SNESSetLagPreconditionerPersists(snes, persist));
1030:   PetscCall(PetscOptionsInt("-snes_lag_jacobian", "How often to rebuild Jacobian", "SNESSetLagJacobian", snes->lagjacobian, &lag, &flg));
1031:   if (flg) {
1032:     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");
1033:     PetscCall(SNESSetLagJacobian(snes, lag));
1034:   }
1035:   PetscCall(PetscOptionsBool("-snes_lag_jacobian_persists", "Jacobian lagging through multiple SNES solves", "SNESSetLagJacobianPersists", snes->lagjac_persist, &persist, &flg));
1036:   if (flg) PetscCall(SNESSetLagJacobianPersists(snes, persist));

1038:   PetscCall(PetscOptionsInt("-snes_grid_sequence", "Use grid sequencing to generate initial guess", "SNESSetGridSequence", snes->gridsequence, &grids, &flg));
1039:   if (flg) PetscCall(SNESSetGridSequence(snes, grids));

1041:   PetscCall(PetscOptionsEList("-snes_convergence_test", "Convergence test", "SNESSetConvergenceTest", convtests, PETSC_STATIC_ARRAY_LENGTH(convtests), "default", &indx, &flg));
1042:   if (flg) {
1043:     switch (indx) {
1044:     case 0:
1045:       PetscCall(SNESSetConvergenceTest(snes, SNESConvergedDefault, NULL, NULL));
1046:       break;
1047:     case 1:
1048:       PetscCall(SNESSetConvergenceTest(snes, SNESConvergedSkip, NULL, NULL));
1049:       break;
1050:     case 2:
1051:       PetscCall(SNESSetConvergenceTest(snes, SNESConvergedCorrectPressure, NULL, NULL));
1052:       break;
1053:     }
1054:   }

1056:   PetscCall(PetscOptionsEList("-snes_norm_schedule", "SNES Norm schedule", "SNESSetNormSchedule", SNESNormSchedules, 5, "function", &indx, &flg));
1057:   if (flg) PetscCall(SNESSetNormSchedule(snes, (SNESNormSchedule)indx));

1059:   PetscCall(PetscOptionsEList("-snes_function_type", "SNES Norm schedule", "SNESSetFunctionType", SNESFunctionTypes, 2, "unpreconditioned", &indx, &flg));
1060:   if (flg) PetscCall(SNESSetFunctionType(snes, (SNESFunctionType)indx));

1062:   kctx = (SNESKSPEW *)snes->kspconvctx;

1064:   PetscCall(PetscOptionsBool("-snes_ksp_ew", "Use Eisentat-Walker linear system convergence test", "SNESKSPSetUseEW", snes->ksp_ewconv, &snes->ksp_ewconv, NULL));

1066:   PetscCall(SNESGetOptionsPrefix(snes, &optionsprefix));
1067:   PetscCall(PetscSNPrintf(ewprefix, sizeof(ewprefix), "%s%s", optionsprefix ? optionsprefix : "", "snes_"));
1068:   PetscCall(SNESEWSetFromOptions_Private(kctx, PETSC_TRUE, PetscObjectComm((PetscObject)snes), ewprefix));

1070:   flg = PETSC_FALSE;
1071:   PetscCall(PetscOptionsBool("-snes_monitor_cancel", "Remove all monitors", "SNESMonitorCancel", flg, &flg, &set));
1072:   if (set && flg) PetscCall(SNESMonitorCancel(snes));

1074:   PetscCall(SNESMonitorSetFromOptions(snes, "-snes_monitor", "Monitor norm of function", "SNESMonitorDefault", SNESMonitorDefault, SNESMonitorDefaultSetUp));
1075:   PetscCall(SNESMonitorSetFromOptions(snes, "-snes_monitor_short", "Monitor norm of function with fewer digits", "SNESMonitorDefaultShort", SNESMonitorDefaultShort, NULL));
1076:   PetscCall(SNESMonitorSetFromOptions(snes, "-snes_monitor_range", "Monitor range of elements of function", "SNESMonitorRange", SNESMonitorRange, NULL));

1078:   PetscCall(SNESMonitorSetFromOptions(snes, "-snes_monitor_ratio", "Monitor ratios of the norm of function for consecutive steps", "SNESMonitorRatio", SNESMonitorRatio, SNESMonitorRatioSetUp));
1079:   PetscCall(SNESMonitorSetFromOptions(snes, "-snes_monitor_field", "Monitor norm of function (split into fields)", "SNESMonitorDefaultField", SNESMonitorDefaultField, NULL));
1080:   PetscCall(SNESMonitorSetFromOptions(snes, "-snes_monitor_solution", "View solution at each iteration", "SNESMonitorSolution", SNESMonitorSolution, NULL));
1081:   PetscCall(SNESMonitorSetFromOptions(snes, "-snes_monitor_solution_update", "View correction at each iteration", "SNESMonitorSolutionUpdate", SNESMonitorSolutionUpdate, NULL));
1082:   PetscCall(SNESMonitorSetFromOptions(snes, "-snes_monitor_residual", "View residual at each iteration", "SNESMonitorResidual", SNESMonitorResidual, NULL));
1083:   PetscCall(SNESMonitorSetFromOptions(snes, "-snes_monitor_jacupdate_spectrum", "Print the change in the spectrum of the Jacobian", "SNESMonitorJacUpdateSpectrum", SNESMonitorJacUpdateSpectrum, NULL));
1084:   PetscCall(SNESMonitorSetFromOptions(snes, "-snes_monitor_fields", "Monitor norm of function per field", "SNESMonitorSet", SNESMonitorFields, NULL));
1085:   PetscCall(PetscOptionsBool("-snes_monitor_pause_final", "Pauses all draw monitors at the final iterate", "SNESMonitorPauseFinal_Internal", PETSC_FALSE, &snes->pauseFinal, NULL));

1087:   PetscCall(PetscOptionsString("-snes_monitor_python", "Use Python function", "SNESMonitorSet", NULL, monfilename, sizeof(monfilename), &flg));
1088:   if (flg) PetscCall(PetscPythonMonitorSet((PetscObject)snes, monfilename));

1090:   flg = PETSC_FALSE;
1091:   PetscCall(PetscOptionsBool("-snes_monitor_lg_range", "Plot function range at each iteration", "SNESMonitorLGRange", flg, &flg, NULL));
1092:   if (flg) {
1093:     PetscViewer ctx;

1095:     PetscCall(PetscViewerDrawOpen(PetscObjectComm((PetscObject)snes), NULL, NULL, PETSC_DECIDE, PETSC_DECIDE, 400, 300, &ctx));
1096:     PetscCall(SNESMonitorSet(snes, SNESMonitorLGRange, ctx, (PetscCtxDestroyFn *)PetscViewerDestroy));
1097:   }

1099:   PetscCall(PetscViewerDestroy(&snes->convergedreasonviewer));
1100:   PetscCall(PetscOptionsCreateViewer(PetscObjectComm((PetscObject)snes), ((PetscObject)snes)->options, ((PetscObject)snes)->prefix, "-snes_converged_reason", &snes->convergedreasonviewer, &snes->convergedreasonformat, NULL));
1101:   flg = PETSC_FALSE;
1102:   PetscCall(PetscOptionsBool("-snes_converged_reason_view_cancel", "Remove all converged reason viewers", "SNESConvergedReasonViewCancel", flg, &flg, &set));
1103:   if (set && flg) PetscCall(SNESConvergedReasonViewCancel(snes));

1105:   flg = PETSC_FALSE;
1106:   PetscCall(PetscOptionsBool("-snes_fd", "Use finite differences (slow) to compute Jacobian", "SNESComputeJacobianDefault", flg, &flg, NULL));
1107:   if (flg) {
1108:     void *functx;
1109:     DM    dm;
1110:     PetscCall(SNESGetDM(snes, &dm));
1111:     PetscCall(DMSNESUnsetJacobianContext_Internal(dm));
1112:     PetscCall(SNESGetFunction(snes, NULL, NULL, &functx));
1113:     PetscCall(SNESSetJacobian(snes, snes->jacobian, snes->jacobian_pre, SNESComputeJacobianDefault, functx));
1114:     PetscCall(PetscInfo(snes, "Setting default finite difference Jacobian matrix\n"));
1115:   }

1117:   flg = PETSC_FALSE;
1118:   PetscCall(PetscOptionsBool("-snes_fd_function", "Use finite differences (slow) to compute function from user objective", "SNESObjectiveComputeFunctionDefaultFD", flg, &flg, NULL));
1119:   if (flg) PetscCall(SNESSetFunction(snes, NULL, SNESObjectiveComputeFunctionDefaultFD, NULL));

1121:   flg = PETSC_FALSE;
1122:   PetscCall(PetscOptionsBool("-snes_fd_color", "Use finite differences with coloring to compute Jacobian", "SNESComputeJacobianDefaultColor", flg, &flg, NULL));
1123:   if (flg) {
1124:     DM dm;
1125:     PetscCall(SNESGetDM(snes, &dm));
1126:     PetscCall(DMSNESUnsetJacobianContext_Internal(dm));
1127:     PetscCall(SNESSetJacobian(snes, snes->jacobian, snes->jacobian_pre, SNESComputeJacobianDefaultColor, NULL));
1128:     PetscCall(PetscInfo(snes, "Setting default finite difference coloring Jacobian matrix\n"));
1129:   }

1131:   flg = PETSC_FALSE;
1132:   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));
1133:   if (flg && snes->mf_operator) {
1134:     snes->mf_operator = PETSC_TRUE;
1135:     snes->mf          = PETSC_TRUE;
1136:   }
1137:   flg = PETSC_FALSE;
1138:   PetscCall(PetscOptionsBool("-snes_mf", "Use a Matrix-Free Jacobian with no matrix for computing the preconditioner", "SNESSetUseMatrixFree", PETSC_FALSE, &snes->mf, &flg));
1139:   if (!flg && snes->mf_operator) snes->mf = PETSC_TRUE;
1140:   PetscCall(PetscOptionsInt("-snes_mf_version", "Matrix-Free routines version 1 or 2", "None", snes->mf_version, &snes->mf_version, NULL));

1142:   PetscCall(PetscOptionsName("-snes_test_function", "Compare hand-coded and finite difference functions", "None", &snes->testFunc));
1143:   PetscCall(PetscOptionsName("-snes_test_jacobian", "Compare hand-coded and finite difference Jacobians", "None", &snes->testJac));

1145:   flg = PETSC_FALSE;
1146:   PetscCall(SNESGetNPCSide(snes, &pcside));
1147:   PetscCall(PetscOptionsEnum("-snes_npc_side", "SNES nonlinear preconditioner side", "SNESSetNPCSide", PCSides, (PetscEnum)pcside, (PetscEnum *)&pcside, &flg));
1148:   if (flg) PetscCall(SNESSetNPCSide(snes, pcside));

1150: #if defined(PETSC_HAVE_SAWS)
1151:   /*
1152:     Publish convergence information using SAWs
1153:   */
1154:   flg = PETSC_FALSE;
1155:   PetscCall(PetscOptionsBool("-snes_monitor_saws", "Publish SNES progress using SAWs", "SNESMonitorSet", flg, &flg, NULL));
1156:   if (flg) {
1157:     void *ctx;
1158:     PetscCall(SNESMonitorSAWsCreate(snes, &ctx));
1159:     PetscCall(SNESMonitorSet(snes, SNESMonitorSAWs, ctx, SNESMonitorSAWsDestroy));
1160:   }
1161: #endif
1162: #if defined(PETSC_HAVE_SAWS)
1163:   {
1164:     PetscBool set;
1165:     flg = PETSC_FALSE;
1166:     PetscCall(PetscOptionsBool("-snes_saws_block", "Block for SAWs at end of SNESSolve", "PetscObjectSAWsBlock", ((PetscObject)snes)->amspublishblock, &flg, &set));
1167:     if (set) PetscCall(PetscObjectSAWsSetBlock((PetscObject)snes, flg));
1168:   }
1169: #endif

1171:   for (i = 0; i < numberofsetfromoptions; i++) PetscCall((*othersetfromoptions[i])(snes));

1173:   PetscTryTypeMethod(snes, setfromoptions, PetscOptionsObject);

1175:   /* process any options handlers added with PetscObjectAddOptionsHandler() */
1176:   PetscCall(PetscObjectProcessOptionsHandlers((PetscObject)snes, PetscOptionsObject));
1177:   PetscOptionsEnd();

1179:   if (snes->linesearch) {
1180:     PetscCall(SNESGetLineSearch(snes, &snes->linesearch));
1181:     PetscCall(SNESLineSearchSetFromOptions(snes->linesearch));
1182:   }

1184:   if (snes->usesksp) {
1185:     if (!snes->ksp) PetscCall(SNESGetKSP(snes, &snes->ksp));
1186:     PetscCall(KSPSetOperators(snes->ksp, snes->jacobian, snes->jacobian_pre));
1187:     PetscCall(KSPSetFromOptions(snes->ksp));
1188:   }

1190:   /* if user has set the SNES NPC type via options database, create it. */
1191:   PetscCall(SNESGetOptionsPrefix(snes, &optionsprefix));
1192:   PetscCall(PetscOptionsHasName(((PetscObject)snes)->options, optionsprefix, "-npc_snes_type", &pcset));
1193:   if (pcset && (!snes->npc)) PetscCall(SNESGetNPC(snes, &snes->npc));
1194:   if (snes->npc) PetscCall(SNESSetFromOptions(snes->npc));
1195:   snes->setfromoptionscalled++;
1196:   PetscFunctionReturn(PETSC_SUCCESS);
1197: }

1199: /*@
1200:   SNESResetFromOptions - Sets various `SNES` and `KSP` parameters from user options ONLY if the `SNESSetFromOptions()` was previously called

1202:   Collective

1204:   Input Parameter:
1205: . snes - the `SNES` context

1207:   Level: advanced

1209: .seealso: [](ch_snes), `SNES`, `SNESSetFromOptions()`, `SNESSetOptionsPrefix()`
1210: @*/
1211: PetscErrorCode SNESResetFromOptions(SNES snes)
1212: {
1213:   PetscFunctionBegin;
1214:   if (snes->setfromoptionscalled) PetscCall(SNESSetFromOptions(snes));
1215:   PetscFunctionReturn(PETSC_SUCCESS);
1216: }

1218: /*@C
1219:   SNESSetComputeApplicationContext - Sets an optional function to compute a user-defined context for
1220:   the nonlinear solvers.

1222:   Logically Collective; No Fortran Support

1224:   Input Parameters:
1225: + snes    - the `SNES` context
1226: . compute - function to compute the context
1227: - destroy - function to destroy the context, see `PetscCtxDestroyFn` for the calling sequence

1229:   Calling sequence of `compute`:
1230: + snes - the `SNES` context
1231: - ctx  - context to be computed

1233:   Level: intermediate

1235:   Note:
1236:   This routine is useful if you are performing grid sequencing or using `SNESFAS` and need the appropriate context generated for each level.

1238:   Use `SNESSetApplicationContext()` to see the context immediately

1240: .seealso: [](ch_snes), `SNESGetApplicationContext()`, `SNESSetApplicationContext()`, `PetscCtxDestroyFn`
1241: @*/
1242: PetscErrorCode SNESSetComputeApplicationContext(SNES snes, PetscErrorCode (*compute)(SNES snes, void **ctx), PetscCtxDestroyFn *destroy)
1243: {
1244:   PetscFunctionBegin;
1246:   snes->ops->usercompute = compute;
1247:   snes->ops->ctxdestroy  = destroy;
1248:   PetscFunctionReturn(PETSC_SUCCESS);
1249: }

1251: /*@
1252:   SNESSetApplicationContext - Sets the optional user-defined context for the nonlinear solvers.

1254:   Logically Collective

1256:   Input Parameters:
1257: + snes - the `SNES` context
1258: - ctx  - the user context

1260:   Level: intermediate

1262:   Notes:
1263:   Users can provide a context when constructing the `SNES` options and then access it inside their function, Jacobian computation, or other evaluation function
1264:   with `SNESGetApplicationContext()`

1266:   To provide a function that computes the context for you use `SNESSetComputeApplicationContext()`

1268:   Fortran Note:
1269:   This only works when `ctx` is a Fortran derived type (it cannot be a `PetscObject`), we recommend writing a Fortran interface definition for this
1270:   function that tells the Fortran compiler the derived data type that is passed in as the `ctx` argument. See `SNESGetApplicationContext()` for
1271:   an example.

1273: .seealso: [](ch_snes), `SNES`, `SNESSetComputeApplicationContext()`, `SNESGetApplicationContext()`
1274: @*/
1275: PetscErrorCode SNESSetApplicationContext(SNES snes, void *ctx)
1276: {
1277:   KSP ksp;

1279:   PetscFunctionBegin;
1281:   PetscCall(SNESGetKSP(snes, &ksp));
1282:   PetscCall(KSPSetApplicationContext(ksp, ctx));
1283:   snes->ctx = ctx;
1284:   PetscFunctionReturn(PETSC_SUCCESS);
1285: }

1287: /*@
1288:   SNESGetApplicationContext - Gets the user-defined context for the
1289:   nonlinear solvers set with `SNESGetApplicationContext()` or `SNESSetComputeApplicationContext()`

1291:   Not Collective

1293:   Input Parameter:
1294: . snes - `SNES` context

1296:   Output Parameter:
1297: . ctx - user context

1299:   Level: intermediate

1301:   Fortran Notes:
1302:   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
1303:   function that tells the Fortran compiler the derived data type that is returned as the `ctx` argument. For example,
1304: .vb
1305:   Interface SNESGetApplicationContext
1306:     Subroutine SNESGetApplicationContext(snes,ctx,ierr)
1307:   #include <petsc/finclude/petscsnes.h>
1308:       use petscsnes
1309:       SNES snes
1310:       type(tUsertype), pointer :: ctx
1311:       PetscErrorCode ierr
1312:     End Subroutine
1313:   End Interface SNESGetApplicationContext
1314: .ve

1316:   The prototype for `ctx` must be
1317: .vb
1318:   type(tUsertype), pointer :: ctx
1319: .ve

1321: .seealso: [](ch_snes), `SNESSetApplicationContext()`, `SNESSetComputeApplicationContext()`
1322: @*/
1323: PetscErrorCode SNESGetApplicationContext(SNES snes, PeCtx ctx)
1324: {
1325:   PetscFunctionBegin;
1327:   *(void **)ctx = snes->ctx;
1328:   PetscFunctionReturn(PETSC_SUCCESS);
1329: }

1331: /*@
1332:   SNESSetUseMatrixFree - indicates that `SNES` should use matrix-free finite difference matrix-vector products to apply the Jacobian.

1334:   Logically Collective

1336:   Input Parameters:
1337: + snes        - `SNES` context
1338: . mf_operator - use matrix-free only for the Amat used by `SNESSetJacobian()`, this means the user provided Pmat will continue to be used
1339: - 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
1340:                 this option no matrix-element based preconditioners can be used in the linear solve since the matrix won't be explicitly available

1342:   Options Database Keys:
1343: + -snes_mf_operator - use matrix-free only for the mat operator
1344: . -snes_mf          - use matrix-free for both the mat and pmat operator
1345: . -snes_fd_color    - compute the Jacobian via coloring and finite differences.
1346: - -snes_fd          - compute the Jacobian via finite differences (slow)

1348:   Level: intermediate

1350:   Note:
1351:   `SNES` supports three approaches for computing (approximate) Jacobians: user provided via `SNESSetJacobian()`, matrix-free using `MatCreateSNESMF()`,
1352:   and computing explicitly with
1353:   finite differences and coloring using `MatFDColoring`. It is also possible to use automatic differentiation and the `MatFDColoring` object.

1355: .seealso: [](ch_snes), `SNES`, `SNESGetUseMatrixFree()`, `MatCreateSNESMF()`, `SNESComputeJacobianDefaultColor()`, `MatFDColoring`
1356: @*/
1357: PetscErrorCode SNESSetUseMatrixFree(SNES snes, PetscBool mf_operator, PetscBool mf)
1358: {
1359:   PetscFunctionBegin;
1363:   snes->mf          = mf_operator ? PETSC_TRUE : mf;
1364:   snes->mf_operator = mf_operator;
1365:   PetscFunctionReturn(PETSC_SUCCESS);
1366: }

1368: /*@
1369:   SNESGetUseMatrixFree - indicates if the `SNES` uses matrix-free finite difference matrix vector products to apply the Jacobian.

1371:   Not Collective, but the resulting flags will be the same on all MPI processes

1373:   Input Parameter:
1374: . snes - `SNES` context

1376:   Output Parameters:
1377: + mf_operator - use matrix-free only for the Amat used by `SNESSetJacobian()`, this means the user provided Pmat will continue to be used
1378: - mf          - use matrix-free for both the Amat and Pmat used by `SNESSetJacobian()`, both the Amat and Pmat set in `SNESSetJacobian()` will be ignored

1380:   Level: intermediate

1382: .seealso: [](ch_snes), `SNES`, `SNESSetUseMatrixFree()`, `MatCreateSNESMF()`
1383: @*/
1384: PetscErrorCode SNESGetUseMatrixFree(SNES snes, PetscBool *mf_operator, PetscBool *mf)
1385: {
1386:   PetscFunctionBegin;
1388:   if (mf) *mf = snes->mf;
1389:   if (mf_operator) *mf_operator = snes->mf_operator;
1390:   PetscFunctionReturn(PETSC_SUCCESS);
1391: }

1393: /*@
1394:   SNESGetIterationNumber - Gets the number of nonlinear iterations completed in the current or most recent `SNESSolve()`

1396:   Not Collective

1398:   Input Parameter:
1399: . snes - `SNES` context

1401:   Output Parameter:
1402: . iter - iteration number

1404:   Level: intermediate

1406:   Notes:
1407:   For example, during the computation of iteration 2 this would return 1.

1409:   This is useful for using lagged Jacobians (where one does not recompute the
1410:   Jacobian at each `SNES` iteration). For example, the code
1411: .vb
1412:       ierr = SNESGetIterationNumber(snes,&it);
1413:       if (!(it % 2)) {
1414:         [compute Jacobian here]
1415:       }
1416: .ve
1417:   can be used in your function that computes the Jacobian to cause the Jacobian to be
1418:   recomputed every second `SNES` iteration. See also `SNESSetLagJacobian()`

1420:   After the `SNES` solve is complete this will return the number of nonlinear iterations used.

1422: .seealso: [](ch_snes), `SNES`, `SNESSolve()`, `SNESSetLagJacobian()`, `SNESGetLinearSolveIterations()`, `SNESSetMonitor()`
1423: @*/
1424: PetscErrorCode SNESGetIterationNumber(SNES snes, PetscInt *iter)
1425: {
1426:   PetscFunctionBegin;
1428:   PetscAssertPointer(iter, 2);
1429:   *iter = snes->iter;
1430:   PetscFunctionReturn(PETSC_SUCCESS);
1431: }

1433: /*@
1434:   SNESSetIterationNumber - Sets the current iteration number.

1436:   Not Collective

1438:   Input Parameters:
1439: + snes - `SNES` context
1440: - iter - iteration number

1442:   Level: developer

1444:   Note:
1445:   This should only be called inside a `SNES` nonlinear solver.

1447: .seealso: [](ch_snes), `SNESGetLinearSolveIterations()`
1448: @*/
1449: PetscErrorCode SNESSetIterationNumber(SNES snes, PetscInt iter)
1450: {
1451:   PetscFunctionBegin;
1453:   PetscCall(PetscObjectSAWsTakeAccess((PetscObject)snes));
1454:   snes->iter = iter;
1455:   PetscCall(PetscObjectSAWsGrantAccess((PetscObject)snes));
1456:   PetscFunctionReturn(PETSC_SUCCESS);
1457: }

1459: /*@
1460:   SNESGetNonlinearStepFailures - Gets the number of unsuccessful steps
1461:   attempted by the nonlinear solver in the current or most recent `SNESSolve()` .

1463:   Not Collective

1465:   Input Parameter:
1466: . snes - `SNES` context

1468:   Output Parameter:
1469: . nfails - number of unsuccessful steps attempted

1471:   Level: intermediate

1473:   Note:
1474:   This counter is reset to zero for each successive call to `SNESSolve()`.

1476: .seealso: [](ch_snes), `SNES`, `SNESGetMaxLinearSolveFailures()`, `SNESGetLinearSolveIterations()`, `SNESSetMaxLinearSolveFailures()`, `SNESGetLinearSolveFailures()`,
1477:           `SNESSetMaxNonlinearStepFailures()`, `SNESGetMaxNonlinearStepFailures()`
1478: @*/
1479: PetscErrorCode SNESGetNonlinearStepFailures(SNES snes, PetscInt *nfails)
1480: {
1481:   PetscFunctionBegin;
1483:   PetscAssertPointer(nfails, 2);
1484:   *nfails = snes->numFailures;
1485:   PetscFunctionReturn(PETSC_SUCCESS);
1486: }

1488: /*@
1489:   SNESSetMaxNonlinearStepFailures - Sets the maximum number of unsuccessful steps
1490:   attempted by the nonlinear solver before it gives up and returns unconverged or generates an error

1492:   Not Collective

1494:   Input Parameters:
1495: + snes     - `SNES` context
1496: - maxFails - maximum of unsuccessful steps allowed, use `PETSC_UNLIMITED` to have no limit on the number of failures

1498:   Options Database Key:
1499: . -snes_max_fail <n> - maximum number of unsuccessful steps allowed

1501:   Level: intermediate

1503:   Developer Note:
1504:   The options database key is wrong for this function name

1506: .seealso: [](ch_snes), `SNESSetErrorIfNotConverged()`, `SNESGetMaxLinearSolveFailures()`, `SNESGetLinearSolveIterations()`, `SNESSetMaxLinearSolveFailures()`, `SNESGetLinearSolveFailures()`,
1507:           `SNESGetMaxNonlinearStepFailures()`, `SNESGetNonlinearStepFailures()`
1508: @*/
1509: PetscErrorCode SNESSetMaxNonlinearStepFailures(SNES snes, PetscInt maxFails)
1510: {
1511:   PetscFunctionBegin;

1514:   if (maxFails == PETSC_UNLIMITED) {
1515:     snes->maxFailures = PETSC_INT_MAX;
1516:   } else {
1517:     PetscCheck(maxFails >= 0, PetscObjectComm((PetscObject)snes), PETSC_ERR_ARG_OUTOFRANGE, "Cannot have a negative maximum number of failures");
1518:     snes->maxFailures = maxFails;
1519:   }
1520:   PetscFunctionReturn(PETSC_SUCCESS);
1521: }

1523: /*@
1524:   SNESGetMaxNonlinearStepFailures - Gets the maximum number of unsuccessful steps
1525:   attempted by the nonlinear solver before it gives up and returns unconverged or generates an error

1527:   Not Collective

1529:   Input Parameter:
1530: . snes - `SNES` context

1532:   Output Parameter:
1533: . maxFails - maximum of unsuccessful steps

1535:   Level: intermediate

1537: .seealso: [](ch_snes), `SNESSetErrorIfNotConverged()`, `SNESGetMaxLinearSolveFailures()`, `SNESGetLinearSolveIterations()`, `SNESSetMaxLinearSolveFailures()`, `SNESGetLinearSolveFailures()`,
1538:           `SNESSetMaxNonlinearStepFailures()`, `SNESGetNonlinearStepFailures()`
1539: @*/
1540: PetscErrorCode SNESGetMaxNonlinearStepFailures(SNES snes, PetscInt *maxFails)
1541: {
1542:   PetscFunctionBegin;
1544:   PetscAssertPointer(maxFails, 2);
1545:   *maxFails = snes->maxFailures;
1546:   PetscFunctionReturn(PETSC_SUCCESS);
1547: }

1549: /*@
1550:   SNESGetNumberFunctionEvals - Gets the number of user provided function evaluations
1551:   done by the `SNES` object in the current or most recent `SNESSolve()`

1553:   Not Collective

1555:   Input Parameter:
1556: . snes - `SNES` context

1558:   Output Parameter:
1559: . nfuncs - number of evaluations

1561:   Level: intermediate

1563:   Note:
1564:   Reset every time `SNESSolve()` is called unless `SNESSetCountersReset()` is used.

1566: .seealso: [](ch_snes), `SNES`, `SNESGetMaxLinearSolveFailures()`, `SNESGetLinearSolveIterations()`, `SNESSetMaxLinearSolveFailures()`, `SNESGetLinearSolveFailures()`, `SNESSetCountersReset()`
1567: @*/
1568: PetscErrorCode SNESGetNumberFunctionEvals(SNES snes, PetscInt *nfuncs)
1569: {
1570:   PetscFunctionBegin;
1572:   PetscAssertPointer(nfuncs, 2);
1573:   *nfuncs = snes->nfuncs;
1574:   PetscFunctionReturn(PETSC_SUCCESS);
1575: }

1577: /*@
1578:   SNESGetLinearSolveFailures - Gets the number of failed (non-converged)
1579:   linear solvers in the current or most recent `SNESSolve()`

1581:   Not Collective

1583:   Input Parameter:
1584: . snes - `SNES` context

1586:   Output Parameter:
1587: . nfails - number of failed solves

1589:   Options Database Key:
1590: . -snes_max_linear_solve_fail <num> - The number of failures before the solve is terminated

1592:   Level: intermediate

1594:   Note:
1595:   This counter is reset to zero for each successive call to `SNESSolve()`.

1597: .seealso: [](ch_snes), `SNESGetMaxLinearSolveFailures()`, `SNESGetLinearSolveIterations()`, `SNESSetMaxLinearSolveFailures()`
1598: @*/
1599: PetscErrorCode SNESGetLinearSolveFailures(SNES snes, PetscInt *nfails)
1600: {
1601:   PetscFunctionBegin;
1603:   PetscAssertPointer(nfails, 2);
1604:   *nfails = snes->numLinearSolveFailures;
1605:   PetscFunctionReturn(PETSC_SUCCESS);
1606: }

1608: /*@
1609:   SNESSetMaxLinearSolveFailures - the number of failed linear solve attempts
1610:   allowed before `SNES` returns with a diverged reason of `SNES_DIVERGED_LINEAR_SOLVE`

1612:   Logically Collective

1614:   Input Parameters:
1615: + snes     - `SNES` context
1616: - maxFails - maximum allowed linear solve failures, use `PETSC_UNLIMITED` to have no limit on the number of failures

1618:   Options Database Key:
1619: . -snes_max_linear_solve_fail <num> - The number of failures before the solve is terminated

1621:   Level: intermediate

1623:   Note:
1624:   By default this is 0; that is `SNES` returns on the first failed linear solve

1626:   Developer Note:
1627:   The options database key is wrong for this function name

1629: .seealso: [](ch_snes), `SNESSetErrorIfNotConverged()`, `SNESGetLinearSolveFailures()`, `SNESGetMaxLinearSolveFailures()`, `SNESGetLinearSolveIterations()`
1630: @*/
1631: PetscErrorCode SNESSetMaxLinearSolveFailures(SNES snes, PetscInt maxFails)
1632: {
1633:   PetscFunctionBegin;

1637:   if (maxFails == PETSC_UNLIMITED) {
1638:     snes->maxLinearSolveFailures = PETSC_INT_MAX;
1639:   } else {
1640:     PetscCheck(maxFails >= 0, PetscObjectComm((PetscObject)snes), PETSC_ERR_ARG_OUTOFRANGE, "Cannot have a negative maximum number of failures");
1641:     snes->maxLinearSolveFailures = maxFails;
1642:   }
1643:   PetscFunctionReturn(PETSC_SUCCESS);
1644: }

1646: /*@
1647:   SNESGetMaxLinearSolveFailures - gets the maximum number of linear solve failures that
1648:   are allowed before `SNES` returns as unsuccessful

1650:   Not Collective

1652:   Input Parameter:
1653: . snes - `SNES` context

1655:   Output Parameter:
1656: . maxFails - maximum of unsuccessful solves allowed

1658:   Level: intermediate

1660:   Note:
1661:   By default this is 1; that is `SNES` returns on the first failed linear solve

1663: .seealso: [](ch_snes), `SNESSetErrorIfNotConverged()`, `SNESGetLinearSolveFailures()`, `SNESGetLinearSolveIterations()`, `SNESSetMaxLinearSolveFailures()`,
1664: @*/
1665: PetscErrorCode SNESGetMaxLinearSolveFailures(SNES snes, PetscInt *maxFails)
1666: {
1667:   PetscFunctionBegin;
1669:   PetscAssertPointer(maxFails, 2);
1670:   *maxFails = snes->maxLinearSolveFailures;
1671:   PetscFunctionReturn(PETSC_SUCCESS);
1672: }

1674: /*@
1675:   SNESGetLinearSolveIterations - Gets the total number of linear iterations
1676:   used by the nonlinear solver in the most recent `SNESSolve()`

1678:   Not Collective

1680:   Input Parameter:
1681: . snes - `SNES` context

1683:   Output Parameter:
1684: . lits - number of linear iterations

1686:   Level: intermediate

1688:   Notes:
1689:   This counter is reset to zero for each successive call to `SNESSolve()` unless `SNESSetCountersReset()` is used.

1691:   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
1692:   then call `KSPGetIterationNumber()` after the failed solve.

1694: .seealso: [](ch_snes), `SNES`, `SNESGetIterationNumber()`, `SNESGetLinearSolveFailures()`, `SNESGetMaxLinearSolveFailures()`, `SNESSetCountersReset()`
1695: @*/
1696: PetscErrorCode SNESGetLinearSolveIterations(SNES snes, PetscInt *lits)
1697: {
1698:   PetscFunctionBegin;
1700:   PetscAssertPointer(lits, 2);
1701:   *lits = snes->linear_its;
1702:   PetscFunctionReturn(PETSC_SUCCESS);
1703: }

1705: /*@
1706:   SNESSetCountersReset - Sets whether or not the counters for linear iterations and function evaluations
1707:   are reset every time `SNESSolve()` is called.

1709:   Logically Collective

1711:   Input Parameters:
1712: + snes  - `SNES` context
1713: - reset - whether to reset the counters or not, defaults to `PETSC_TRUE`

1715:   Level: developer

1717: .seealso: [](ch_snes), `SNESGetNumberFunctionEvals()`, `SNESGetLinearSolveIterations()`, `SNESGetNPC()`
1718: @*/
1719: PetscErrorCode SNESSetCountersReset(SNES snes, PetscBool reset)
1720: {
1721:   PetscFunctionBegin;
1724:   snes->counters_reset = reset;
1725:   PetscFunctionReturn(PETSC_SUCCESS);
1726: }

1728: /*@
1729:   SNESResetCounters - Reset counters for linear iterations and function evaluations.

1731:   Logically Collective

1733:   Input Parameters:
1734: . snes - `SNES` context

1736:   Level: developer

1738:   Note:
1739:   It honors the flag set with `SNESSetCountersReset()`

1741: .seealso: [](ch_snes), `SNESGetNumberFunctionEvals()`, `SNESGetLinearSolveIterations()`, `SNESGetNPC()`
1742: @*/
1743: PetscErrorCode SNESResetCounters(SNES snes)
1744: {
1745:   PetscFunctionBegin;
1747:   if (snes->counters_reset) {
1748:     snes->nfuncs      = 0;
1749:     snes->linear_its  = 0;
1750:     snes->numFailures = 0;
1751:   }
1752:   PetscFunctionReturn(PETSC_SUCCESS);
1753: }

1755: /*@
1756:   SNESSetKSP - Sets a `KSP` context for the `SNES` object to use

1758:   Not Collective, but the `SNES` and `KSP` objects must live on the same `MPI_Comm`

1760:   Input Parameters:
1761: + snes - the `SNES` context
1762: - ksp  - the `KSP` context

1764:   Level: developer

1766:   Notes:
1767:   The `SNES` object already has its `KSP` object, you can obtain with `SNESGetKSP()`
1768:   so this routine is rarely needed.

1770:   The `KSP` object that is already in the `SNES` object has its reference count
1771:   decreased by one when this is called.

1773: .seealso: [](ch_snes), `SNES`, `KSP`, `KSPGetPC()`, `SNESCreate()`, `KSPCreate()`
1774: @*/
1775: PetscErrorCode SNESSetKSP(SNES snes, KSP ksp)
1776: {
1777:   PetscFunctionBegin;
1780:   PetscCheckSameComm(snes, 1, ksp, 2);
1781:   PetscCall(PetscObjectReference((PetscObject)ksp));
1782:   if (snes->ksp) PetscCall(PetscObjectDereference((PetscObject)snes->ksp));
1783:   snes->ksp = ksp;
1784:   PetscFunctionReturn(PETSC_SUCCESS);
1785: }

1787: /*@
1788:   SNESParametersInitialize - Sets all the parameters in `snes` to their default value (when `SNESCreate()` was called) if they
1789:   currently contain default values

1791:   Collective

1793:   Input Parameter:
1794: . snes - the `SNES` object

1796:   Level: developer

1798:   Developer Note:
1799:   This is called by all the `SNESCreate_XXX()` routines.

1801: .seealso: [](ch_snes), `SNES`, `SNESSolve()`, `SNESDestroy()`, `SNESSetLagPreconditioner()`, `SNESSetLagJacobian()`,
1802:           `PetscObjectParameterSetDefault()`
1803: @*/
1804: PetscErrorCode SNESParametersInitialize(SNES snes)
1805: {
1806:   PetscObjectParameterSetDefault(snes, max_its, 50);
1807:   PetscObjectParameterSetDefault(snes, max_funcs, 10000);
1808:   PetscObjectParameterSetDefault(snes, rtol, PetscDefined(USE_REAL_SINGLE) ? 1.e-5 : 1.e-8);
1809:   PetscObjectParameterSetDefault(snes, abstol, PetscDefined(USE_REAL_SINGLE) ? 1.e-25 : 1.e-50);
1810:   PetscObjectParameterSetDefault(snes, stol, PetscDefined(USE_REAL_SINGLE) ? 1.e-5 : 1.e-8);
1811:   PetscObjectParameterSetDefault(snes, divtol, 1.e4);
1812:   return PETSC_SUCCESS;
1813: }

1815: /*@
1816:   SNESCreate - Creates a nonlinear solver context used to manage a set of nonlinear solves

1818:   Collective

1820:   Input Parameter:
1821: . comm - MPI communicator

1823:   Output Parameter:
1824: . outsnes - the new `SNES` context

1826:   Options Database Keys:
1827: + -snes_mf          - Activates default matrix-free Jacobian-vector products, and no matrix to construct a preconditioner
1828: . -snes_mf_operator - Activates default matrix-free Jacobian-vector products, and a user-provided matrix as set by `SNESSetJacobian()`
1829: . -snes_fd_coloring - uses a relative fast computation of the Jacobian using finite differences and a graph coloring
1830: - -snes_fd          - Uses (slow!) finite differences to compute Jacobian

1832:   Level: beginner

1834:   Developer Notes:
1835:   `SNES` always creates a `KSP` object even though many `SNES` methods do not use it. This is
1836:   unfortunate and should be fixed at some point. The flag snes->usesksp indicates if the
1837:   particular method does use `KSP` and regulates if the information about the `KSP` is printed
1838:   in `SNESView()`.

1840:   `TSSetFromOptions()` does call `SNESSetFromOptions()` which can lead to users being confused
1841:   by help messages about meaningless `SNES` options.

1843:   `SNES` always creates the `snes->kspconvctx` even though it is used by only one type. This should be fixed.

1845: .seealso: [](ch_snes), `SNES`, `SNESSolve()`, `SNESDestroy()`, `SNESSetLagPreconditioner()`, `SNESSetLagJacobian()`
1846: @*/
1847: PetscErrorCode SNESCreate(MPI_Comm comm, SNES *outsnes)
1848: {
1849:   SNES       snes;
1850:   SNESKSPEW *kctx;

1852:   PetscFunctionBegin;
1853:   PetscAssertPointer(outsnes, 2);
1854:   PetscCall(SNESInitializePackage());

1856:   PetscCall(PetscHeaderCreate(snes, SNES_CLASSID, "SNES", "Nonlinear solver", "SNES", comm, SNESDestroy, SNESView));
1857:   snes->ops->converged = SNESConvergedDefault;
1858:   snes->usesksp        = PETSC_TRUE;
1859:   snes->norm           = 0.0;
1860:   snes->xnorm          = 0.0;
1861:   snes->ynorm          = 0.0;
1862:   snes->normschedule   = SNES_NORM_ALWAYS;
1863:   snes->functype       = SNES_FUNCTION_DEFAULT;
1864:   snes->ttol           = 0.0;

1866:   snes->rnorm0               = 0;
1867:   snes->nfuncs               = 0;
1868:   snes->numFailures          = 0;
1869:   snes->maxFailures          = 1;
1870:   snes->linear_its           = 0;
1871:   snes->lagjacobian          = 1;
1872:   snes->jac_iter             = 0;
1873:   snes->lagjac_persist       = PETSC_FALSE;
1874:   snes->lagpreconditioner    = 1;
1875:   snes->pre_iter             = 0;
1876:   snes->lagpre_persist       = PETSC_FALSE;
1877:   snes->numbermonitors       = 0;
1878:   snes->numberreasonviews    = 0;
1879:   snes->data                 = NULL;
1880:   snes->setupcalled          = PETSC_FALSE;
1881:   snes->ksp_ewconv           = PETSC_FALSE;
1882:   snes->nwork                = 0;
1883:   snes->work                 = NULL;
1884:   snes->nvwork               = 0;
1885:   snes->vwork                = NULL;
1886:   snes->conv_hist_len        = 0;
1887:   snes->conv_hist_max        = 0;
1888:   snes->conv_hist            = NULL;
1889:   snes->conv_hist_its        = NULL;
1890:   snes->conv_hist_reset      = PETSC_TRUE;
1891:   snes->counters_reset       = PETSC_TRUE;
1892:   snes->vec_func_init_set    = PETSC_FALSE;
1893:   snes->reason               = SNES_CONVERGED_ITERATING;
1894:   snes->npcside              = PC_RIGHT;
1895:   snes->setfromoptionscalled = 0;

1897:   snes->mf          = PETSC_FALSE;
1898:   snes->mf_operator = PETSC_FALSE;
1899:   snes->mf_version  = 1;

1901:   snes->numLinearSolveFailures = 0;
1902:   snes->maxLinearSolveFailures = 1;

1904:   snes->vizerotolerance     = 1.e-8;
1905:   snes->checkjacdomainerror = PetscDefined(USE_DEBUG) ? PETSC_TRUE : PETSC_FALSE;

1907:   /* Set this to true if the implementation of SNESSolve_XXX does compute the residual at the final solution. */
1908:   snes->alwayscomputesfinalresidual = PETSC_FALSE;

1910:   /* Create context to compute Eisenstat-Walker relative tolerance for KSP */
1911:   PetscCall(PetscNew(&kctx));

1913:   snes->kspconvctx  = kctx;
1914:   kctx->version     = 2;
1915:   kctx->rtol_0      = 0.3; /* Eisenstat and Walker suggest rtol_0=.5, but
1916:                              this was too large for some test cases */
1917:   kctx->rtol_last   = 0.0;
1918:   kctx->rtol_max    = 0.9;
1919:   kctx->gamma       = 1.0;
1920:   kctx->alpha       = 0.5 * (1.0 + PetscSqrtReal(5.0));
1921:   kctx->alpha2      = kctx->alpha;
1922:   kctx->threshold   = 0.1;
1923:   kctx->lresid_last = 0.0;
1924:   kctx->norm_last   = 0.0;

1926:   kctx->rk_last     = 0.0;
1927:   kctx->rk_last_2   = 0.0;
1928:   kctx->rtol_last_2 = 0.0;
1929:   kctx->v4_p1       = 0.1;
1930:   kctx->v4_p2       = 0.4;
1931:   kctx->v4_p3       = 0.7;
1932:   kctx->v4_m1       = 0.8;
1933:   kctx->v4_m2       = 0.5;
1934:   kctx->v4_m3       = 0.1;
1935:   kctx->v4_m4       = 0.5;

1937:   PetscCall(SNESParametersInitialize(snes));
1938:   *outsnes = snes;
1939:   PetscFunctionReturn(PETSC_SUCCESS);
1940: }

1942: /*@C
1943:   SNESSetFunction - Sets the function evaluation routine and function
1944:   vector for use by the `SNES` routines in solving systems of nonlinear
1945:   equations.

1947:   Logically Collective

1949:   Input Parameters:
1950: + snes - the `SNES` context
1951: . r    - vector to store function values, may be `NULL`
1952: . f    - function evaluation routine;  for calling sequence see `SNESFunctionFn`
1953: - ctx  - [optional] user-defined context for private data for the
1954:          function evaluation routine (may be `NULL`)

1956:   Level: beginner

1958: .seealso: [](ch_snes), `SNES`, `SNESGetFunction()`, `SNESComputeFunction()`, `SNESSetJacobian()`, `SNESSetPicard()`, `SNESFunctionFn`
1959: @*/
1960: PetscErrorCode SNESSetFunction(SNES snes, Vec r, SNESFunctionFn *f, void *ctx)
1961: {
1962:   DM dm;

1964:   PetscFunctionBegin;
1966:   if (r) {
1968:     PetscCheckSameComm(snes, 1, r, 2);
1969:     PetscCall(PetscObjectReference((PetscObject)r));
1970:     PetscCall(VecDestroy(&snes->vec_func));
1971:     snes->vec_func = r;
1972:   }
1973:   PetscCall(SNESGetDM(snes, &dm));
1974:   PetscCall(DMSNESSetFunction(dm, f, ctx));
1975:   if (f == SNESPicardComputeFunction) PetscCall(DMSNESSetMFFunction(dm, SNESPicardComputeMFFunction, ctx));
1976:   PetscFunctionReturn(PETSC_SUCCESS);
1977: }

1979: /*@C
1980:   SNESSetInitialFunction - Set an already computed function evaluation at the initial guess to be reused by `SNESSolve()`.

1982:   Logically Collective

1984:   Input Parameters:
1985: + snes - the `SNES` context
1986: - f    - vector to store function value

1988:   Level: developer

1990:   Notes:
1991:   This should not be modified during the solution procedure.

1993:   This is used extensively in the `SNESFAS` hierarchy and in nonlinear preconditioning.

1995: .seealso: [](ch_snes), `SNES`, `SNESFAS`, `SNESSetFunction()`, `SNESComputeFunction()`, `SNESSetInitialFunctionNorm()`
1996: @*/
1997: PetscErrorCode SNESSetInitialFunction(SNES snes, Vec f)
1998: {
1999:   Vec vec_func;

2001:   PetscFunctionBegin;
2004:   PetscCheckSameComm(snes, 1, f, 2);
2005:   if (snes->npcside == PC_LEFT && snes->functype == SNES_FUNCTION_PRECONDITIONED) {
2006:     snes->vec_func_init_set = PETSC_FALSE;
2007:     PetscFunctionReturn(PETSC_SUCCESS);
2008:   }
2009:   PetscCall(SNESGetFunction(snes, &vec_func, NULL, NULL));
2010:   PetscCall(VecCopy(f, vec_func));

2012:   snes->vec_func_init_set = PETSC_TRUE;
2013:   PetscFunctionReturn(PETSC_SUCCESS);
2014: }

2016: /*@
2017:   SNESSetNormSchedule - Sets the `SNESNormSchedule` used in convergence and monitoring
2018:   of the `SNES` method, when norms are computed in the solving process

2020:   Logically Collective

2022:   Input Parameters:
2023: + snes         - the `SNES` context
2024: - normschedule - the frequency of norm computation

2026:   Options Database Key:
2027: . -snes_norm_schedule <none, always, initialonly, finalonly, initialfinalonly> - set the schedule

2029:   Level: advanced

2031:   Notes:
2032:   Only certain `SNES` methods support certain `SNESNormSchedules`.  Most require evaluation
2033:   of the nonlinear function and the taking of its norm at every iteration to
2034:   even ensure convergence at all.  However, methods such as custom Gauss-Seidel methods
2035:   `SNESNGS` and the like do not require the norm of the function to be computed, and therefore
2036:   may either be monitored for convergence or not.  As these are often used as nonlinear
2037:   preconditioners, monitoring the norm of their error is not a useful enterprise within
2038:   their solution.

2040: .seealso: [](ch_snes), `SNESNormSchedule`, `SNESGetNormSchedule()`, `SNESComputeFunction()`, `VecNorm()`, `SNESSetFunction()`, `SNESSetInitialFunction()`
2041: @*/
2042: PetscErrorCode SNESSetNormSchedule(SNES snes, SNESNormSchedule normschedule)
2043: {
2044:   PetscFunctionBegin;
2046:   snes->normschedule = normschedule;
2047:   PetscFunctionReturn(PETSC_SUCCESS);
2048: }

2050: /*@
2051:   SNESGetNormSchedule - Gets the `SNESNormSchedule` used in convergence and monitoring
2052:   of the `SNES` method.

2054:   Logically Collective

2056:   Input Parameters:
2057: + snes         - the `SNES` context
2058: - normschedule - the type of the norm used

2060:   Level: advanced

2062: .seealso: [](ch_snes), `SNES`, `SNESSetNormSchedule()`, `SNESComputeFunction()`, `VecNorm()`, `SNESSetFunction()`, `SNESSetInitialFunction()`, `SNESNormSchedule`
2063: @*/
2064: PetscErrorCode SNESGetNormSchedule(SNES snes, SNESNormSchedule *normschedule)
2065: {
2066:   PetscFunctionBegin;
2068:   *normschedule = snes->normschedule;
2069:   PetscFunctionReturn(PETSC_SUCCESS);
2070: }

2072: /*@
2073:   SNESSetFunctionNorm - Sets the last computed residual norm.

2075:   Logically Collective

2077:   Input Parameters:
2078: + snes - the `SNES` context
2079: - norm - the value of the norm

2081:   Level: developer

2083: .seealso: [](ch_snes), `SNES`, `SNESGetNormSchedule()`, `SNESComputeFunction()`, `VecNorm()`, `SNESSetFunction()`, `SNESSetInitialFunction()`, `SNESNormSchedule`
2084: @*/
2085: PetscErrorCode SNESSetFunctionNorm(SNES snes, PetscReal norm)
2086: {
2087:   PetscFunctionBegin;
2089:   snes->norm = norm;
2090:   PetscFunctionReturn(PETSC_SUCCESS);
2091: }

2093: /*@
2094:   SNESGetFunctionNorm - Gets the last computed norm of the residual

2096:   Not Collective

2098:   Input Parameter:
2099: . snes - the `SNES` context

2101:   Output Parameter:
2102: . norm - the last computed residual norm

2104:   Level: developer

2106: .seealso: [](ch_snes), `SNES`, `SNESSetNormSchedule()`, `SNESComputeFunction()`, `VecNorm()`, `SNESSetFunction()`, `SNESSetInitialFunction()`, `SNESNormSchedule`
2107: @*/
2108: PetscErrorCode SNESGetFunctionNorm(SNES snes, PetscReal *norm)
2109: {
2110:   PetscFunctionBegin;
2112:   PetscAssertPointer(norm, 2);
2113:   *norm = snes->norm;
2114:   PetscFunctionReturn(PETSC_SUCCESS);
2115: }

2117: /*@
2118:   SNESGetUpdateNorm - Gets the last computed norm of the solution update

2120:   Not Collective

2122:   Input Parameter:
2123: . snes - the `SNES` context

2125:   Output Parameter:
2126: . ynorm - the last computed update norm

2128:   Level: developer

2130:   Note:
2131:   The new solution is the current solution plus the update, so this norm is an indication of the size of the update

2133: .seealso: [](ch_snes), `SNES`, `SNESSetNormSchedule()`, `SNESComputeFunction()`, `SNESGetFunctionNorm()`
2134: @*/
2135: PetscErrorCode SNESGetUpdateNorm(SNES snes, PetscReal *ynorm)
2136: {
2137:   PetscFunctionBegin;
2139:   PetscAssertPointer(ynorm, 2);
2140:   *ynorm = snes->ynorm;
2141:   PetscFunctionReturn(PETSC_SUCCESS);
2142: }

2144: /*@
2145:   SNESGetSolutionNorm - Gets the last computed norm of the solution

2147:   Not Collective

2149:   Input Parameter:
2150: . snes - the `SNES` context

2152:   Output Parameter:
2153: . xnorm - the last computed solution norm

2155:   Level: developer

2157: .seealso: [](ch_snes), `SNES`, `SNESSetNormSchedule()`, `SNESComputeFunction()`, `SNESGetFunctionNorm()`, `SNESGetUpdateNorm()`
2158: @*/
2159: PetscErrorCode SNESGetSolutionNorm(SNES snes, PetscReal *xnorm)
2160: {
2161:   PetscFunctionBegin;
2163:   PetscAssertPointer(xnorm, 2);
2164:   *xnorm = snes->xnorm;
2165:   PetscFunctionReturn(PETSC_SUCCESS);
2166: }

2168: /*@
2169:   SNESSetFunctionType - Sets the `SNESFunctionType`
2170:   of the `SNES` method.

2172:   Logically Collective

2174:   Input Parameters:
2175: + snes - the `SNES` context
2176: - type - the function type

2178:   Level: developer

2180:   Values of the function type\:
2181: +  `SNES_FUNCTION_DEFAULT`          - the default for the given `SNESType`
2182: .  `SNES_FUNCTION_UNPRECONDITIONED` - an unpreconditioned function evaluation (this is the function provided with `SNESSetFunction()`
2183: -  `SNES_FUNCTION_PRECONDITIONED`   - a transformation of the function provided with `SNESSetFunction()`

2185:   Note:
2186:   Different `SNESType`s use this value in different ways

2188: .seealso: [](ch_snes), `SNES`, `SNESFunctionType`, `SNESGetNormSchedule()`, `SNESComputeFunction()`, `VecNorm()`, `SNESSetFunction()`, `SNESSetInitialFunction()`, `SNESNormSchedule`
2189: @*/
2190: PetscErrorCode SNESSetFunctionType(SNES snes, SNESFunctionType type)
2191: {
2192:   PetscFunctionBegin;
2194:   snes->functype = type;
2195:   PetscFunctionReturn(PETSC_SUCCESS);
2196: }

2198: /*@
2199:   SNESGetFunctionType - Gets the `SNESFunctionType` used in convergence and monitoring set with `SNESSetFunctionType()`
2200:   of the SNES method.

2202:   Logically Collective

2204:   Input Parameters:
2205: + snes - the `SNES` context
2206: - type - the type of the function evaluation, see `SNESSetFunctionType()`

2208:   Level: advanced

2210: .seealso: [](ch_snes), `SNESSetFunctionType()`, `SNESFunctionType`, `SNESSetNormSchedule()`, `SNESComputeFunction()`, `VecNorm()`, `SNESSetFunction()`, `SNESSetInitialFunction()`, `SNESNormSchedule`
2211: @*/
2212: PetscErrorCode SNESGetFunctionType(SNES snes, SNESFunctionType *type)
2213: {
2214:   PetscFunctionBegin;
2216:   *type = snes->functype;
2217:   PetscFunctionReturn(PETSC_SUCCESS);
2218: }

2220: /*@C
2221:   SNESSetNGS - Sets the user nonlinear Gauss-Seidel routine for
2222:   use with composed nonlinear solvers.

2224:   Input Parameters:
2225: + snes - the `SNES` context, usually of the `SNESType` `SNESNGS`
2226: . f    - function evaluation routine to apply Gauss-Seidel, see `SNESNGSFn` for calling sequence
2227: - ctx  - [optional] user-defined context for private data for the smoother evaluation routine (may be `NULL`)

2229:   Level: intermediate

2231:   Note:
2232:   The `SNESNGS` routines are used by the composed nonlinear solver to generate
2233:   a problem appropriate update to the solution, particularly `SNESFAS`.

2235: .seealso: [](ch_snes), `SNESNGS`, `SNESGetNGS()`, `SNESNCG`, `SNESGetFunction()`, `SNESComputeNGS()`, `SNESNGSFn`
2236: @*/
2237: PetscErrorCode SNESSetNGS(SNES snes, SNESNGSFn *f, void *ctx)
2238: {
2239:   DM dm;

2241:   PetscFunctionBegin;
2243:   PetscCall(SNESGetDM(snes, &dm));
2244:   PetscCall(DMSNESSetNGS(dm, f, ctx));
2245:   PetscFunctionReturn(PETSC_SUCCESS);
2246: }

2248: /*
2249:      This is used for -snes_mf_operator; it uses a duplicate of snes->jacobian_pre because snes->jacobian_pre cannot be
2250:    changed during the KSPSolve()
2251: */
2252: PetscErrorCode SNESPicardComputeMFFunction(SNES snes, Vec x, Vec f, void *ctx)
2253: {
2254:   DM     dm;
2255:   DMSNES sdm;

2257:   PetscFunctionBegin;
2258:   PetscCall(SNESGetDM(snes, &dm));
2259:   PetscCall(DMGetDMSNES(dm, &sdm));
2260:   /*  A(x)*x - b(x) */
2261:   if (sdm->ops->computepfunction) {
2262:     PetscCallBack("SNES Picard callback function", (*sdm->ops->computepfunction)(snes, x, f, sdm->pctx));
2263:     PetscCall(VecScale(f, -1.0));
2264:     /* Cannot share nonzero pattern because of the possible use of SNESComputeJacobianDefault() */
2265:     if (!snes->picard) PetscCall(MatDuplicate(snes->jacobian_pre, MAT_DO_NOT_COPY_VALUES, &snes->picard));
2266:     PetscCallBack("SNES Picard callback Jacobian", (*sdm->ops->computepjacobian)(snes, x, snes->picard, snes->picard, sdm->pctx));
2267:     PetscCall(MatMultAdd(snes->picard, x, f, f));
2268:   } else {
2269:     PetscCallBack("SNES Picard callback Jacobian", (*sdm->ops->computepjacobian)(snes, x, snes->picard, snes->picard, sdm->pctx));
2270:     PetscCall(MatMult(snes->picard, x, f));
2271:   }
2272:   PetscFunctionReturn(PETSC_SUCCESS);
2273: }

2275: PetscErrorCode SNESPicardComputeFunction(SNES snes, Vec x, Vec f, void *ctx)
2276: {
2277:   DM     dm;
2278:   DMSNES sdm;

2280:   PetscFunctionBegin;
2281:   PetscCall(SNESGetDM(snes, &dm));
2282:   PetscCall(DMGetDMSNES(dm, &sdm));
2283:   /*  A(x)*x - b(x) */
2284:   if (sdm->ops->computepfunction) {
2285:     PetscCallBack("SNES Picard callback function", (*sdm->ops->computepfunction)(snes, x, f, sdm->pctx));
2286:     PetscCall(VecScale(f, -1.0));
2287:     PetscCallBack("SNES Picard callback Jacobian", (*sdm->ops->computepjacobian)(snes, x, snes->jacobian, snes->jacobian_pre, sdm->pctx));
2288:     PetscCall(MatMultAdd(snes->jacobian_pre, x, f, f));
2289:   } else {
2290:     PetscCallBack("SNES Picard callback Jacobian", (*sdm->ops->computepjacobian)(snes, x, snes->jacobian, snes->jacobian_pre, sdm->pctx));
2291:     PetscCall(MatMult(snes->jacobian_pre, x, f));
2292:   }
2293:   PetscFunctionReturn(PETSC_SUCCESS);
2294: }

2296: PetscErrorCode SNESPicardComputeJacobian(SNES snes, Vec x1, Mat J, Mat B, void *ctx)
2297: {
2298:   PetscFunctionBegin;
2299:   /* the jacobian matrix should be pre-filled in SNESPicardComputeFunction */
2300:   /* must assembly if matrix-free to get the last SNES solution */
2301:   PetscCall(MatAssemblyBegin(J, MAT_FINAL_ASSEMBLY));
2302:   PetscCall(MatAssemblyEnd(J, MAT_FINAL_ASSEMBLY));
2303:   PetscFunctionReturn(PETSC_SUCCESS);
2304: }

2306: /*@C
2307:   SNESSetPicard - Use `SNES` to solve the system $A(x) x = bp(x) + b $ via a Picard type iteration (Picard linearization)

2309:   Logically Collective

2311:   Input Parameters:
2312: + snes - the `SNES` context
2313: . r    - vector to store function values, may be `NULL`
2314: . bp   - function evaluation routine, may be `NULL`, for the calling sequence see `SNESFunctionFn`
2315: . Amat - matrix with which $A(x) x - bp(x) - b$ is to be computed
2316: . Pmat - matrix from which preconditioner is computed (usually the same as `Amat`)
2317: . J    - function to compute matrix values, for the calling sequence see `SNESJacobianFn`
2318: - ctx  - [optional] user-defined context for private data for the function evaluation routine (may be `NULL`)

2320:   Level: intermediate

2322:   Notes:
2323:   It is often better to provide the nonlinear function $F()$ and some approximation to its Jacobian directly and use
2324:   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.

2326:   One can call `SNESSetPicard()` or `SNESSetFunction()` (and possibly `SNESSetJacobian()`) but cannot call both

2328:   Solves the equation $A(x) x = bp(x) - b$ via the defect correction algorithm $A(x^{n}) (x^{n+1} - x^{n}) = bp(x^{n}) + b - A(x^{n})x^{n}$.
2329:   When an exact solver is used this corresponds to the "classic" Picard $A(x^{n}) x^{n+1} = bp(x^{n}) + b$ iteration.

2331:   Run with `-snes_mf_operator` to solve the system with Newton's method using $A(x^{n})$ to construct the preconditioner.

2333:   We implement the defect correction form of the Picard iteration because it converges much more generally when inexact linear solvers are used then
2334:   the direct Picard iteration $A(x^n) x^{n+1} = bp(x^n) + b$

2336:   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
2337:   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
2338:   different please contact us at petsc-dev@mcs.anl.gov and we'll have an entirely new argument \:-).

2340:   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
2341:   $A(x^{n})$ is used to build the preconditioner

2343:   When used with `-snes_fd` this will compute the true Jacobian (very slowly one column at a time) and thus represent Newton's method.

2345:   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
2346:   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
2347:   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`.
2348:   See the comment in src/snes/tutorials/ex15.c.

2350: .seealso: [](ch_snes), `SNES`, `SNESGetFunction()`, `SNESSetFunction()`, `SNESComputeFunction()`, `SNESSetJacobian()`, `SNESGetPicard()`, `SNESLineSearchPreCheckPicard()`,
2351:           `SNESFunctionFn`, `SNESJacobianFn`
2352: @*/
2353: PetscErrorCode SNESSetPicard(SNES snes, Vec r, SNESFunctionFn *bp, Mat Amat, Mat Pmat, SNESJacobianFn *J, void *ctx)
2354: {
2355:   DM dm;

2357:   PetscFunctionBegin;
2359:   PetscCall(SNESGetDM(snes, &dm));
2360:   PetscCall(DMSNESSetPicard(dm, bp, J, ctx));
2361:   PetscCall(DMSNESSetMFFunction(dm, SNESPicardComputeMFFunction, ctx));
2362:   PetscCall(SNESSetFunction(snes, r, SNESPicardComputeFunction, ctx));
2363:   PetscCall(SNESSetJacobian(snes, Amat, Pmat, SNESPicardComputeJacobian, ctx));
2364:   PetscFunctionReturn(PETSC_SUCCESS);
2365: }

2367: /*@C
2368:   SNESGetPicard - Returns the context for the Picard iteration

2370:   Not Collective, but `Vec` is parallel if `SNES` is parallel. Collective if `Vec` is requested, but has not been created yet.

2372:   Input Parameter:
2373: . snes - the `SNES` context

2375:   Output Parameters:
2376: + r    - the function (or `NULL`)
2377: . f    - the function (or `NULL`);  for calling sequence see `SNESFunctionFn`
2378: . Amat - the matrix used to defined the operation A(x) x - b(x) (or `NULL`)
2379: . Pmat - the matrix from which the preconditioner will be constructed (or `NULL`)
2380: . J    - the function for matrix evaluation (or `NULL`);  for calling sequence see `SNESJacobianFn`
2381: - ctx  - the function context (or `NULL`)

2383:   Level: advanced

2385: .seealso: [](ch_snes), `SNESSetFunction()`, `SNESSetPicard()`, `SNESGetFunction()`, `SNESGetJacobian()`, `SNESGetDM()`, `SNESFunctionFn`, `SNESJacobianFn`
2386: @*/
2387: PetscErrorCode SNESGetPicard(SNES snes, Vec *r, SNESFunctionFn **f, Mat *Amat, Mat *Pmat, SNESJacobianFn **J, void **ctx)
2388: {
2389:   DM dm;

2391:   PetscFunctionBegin;
2393:   PetscCall(SNESGetFunction(snes, r, NULL, NULL));
2394:   PetscCall(SNESGetJacobian(snes, Amat, Pmat, NULL, NULL));
2395:   PetscCall(SNESGetDM(snes, &dm));
2396:   PetscCall(DMSNESGetPicard(dm, f, J, ctx));
2397:   PetscFunctionReturn(PETSC_SUCCESS);
2398: }

2400: /*@C
2401:   SNESSetComputeInitialGuess - Sets a routine used to compute an initial guess for the nonlinear problem

2403:   Logically Collective

2405:   Input Parameters:
2406: + snes - the `SNES` context
2407: . func - function evaluation routine, see `SNESInitialGuessFn` for the calling sequence
2408: - ctx  - [optional] user-defined context for private data for the
2409:          function evaluation routine (may be `NULL`)

2411:   Level: intermediate

2413: .seealso: [](ch_snes), `SNES`, `SNESSolve()`, `SNESSetFunction()`, `SNESGetFunction()`, `SNESComputeFunction()`, `SNESSetJacobian()`, `SNESInitialGuessFn`
2414: @*/
2415: PetscErrorCode SNESSetComputeInitialGuess(SNES snes, SNESInitialGuessFn *func, void *ctx)
2416: {
2417:   PetscFunctionBegin;
2419:   if (func) snes->ops->computeinitialguess = func;
2420:   if (ctx) snes->initialguessP = ctx;
2421:   PetscFunctionReturn(PETSC_SUCCESS);
2422: }

2424: /*@C
2425:   SNESGetRhs - Gets the vector for solving F(x) = `rhs`. If `rhs` is not set
2426:   it assumes a zero right-hand side.

2428:   Logically Collective

2430:   Input Parameter:
2431: . snes - the `SNES` context

2433:   Output Parameter:
2434: . rhs - the right-hand side vector or `NULL` if there is no right-hand side vector

2436:   Level: intermediate

2438: .seealso: [](ch_snes), `SNES`, `SNESGetSolution()`, `SNESGetFunction()`, `SNESComputeFunction()`, `SNESSetJacobian()`, `SNESSetFunction()`
2439: @*/
2440: PetscErrorCode SNESGetRhs(SNES snes, Vec *rhs)
2441: {
2442:   PetscFunctionBegin;
2444:   PetscAssertPointer(rhs, 2);
2445:   *rhs = snes->vec_rhs;
2446:   PetscFunctionReturn(PETSC_SUCCESS);
2447: }

2449: /*@
2450:   SNESComputeFunction - Calls the function that has been set with `SNESSetFunction()`.

2452:   Collective

2454:   Input Parameters:
2455: + snes - the `SNES` context
2456: - x    - input vector

2458:   Output Parameter:
2459: . y - function vector, as set by `SNESSetFunction()`

2461:   Level: developer

2463:   Notes:
2464:   `SNESComputeFunction()` is typically used within nonlinear solvers
2465:   implementations, so users would not generally call this routine themselves.

2467:   When solving for $F(x) = b$, this routine computes $y = F(x) - b$.

2469: .seealso: [](ch_snes), `SNES`, `SNESSetFunction()`, `SNESGetFunction()`, `SNESComputeMFFunction()`
2470: @*/
2471: PetscErrorCode SNESComputeFunction(SNES snes, Vec x, Vec y)
2472: {
2473:   DM     dm;
2474:   DMSNES sdm;

2476:   PetscFunctionBegin;
2480:   PetscCheckSameComm(snes, 1, x, 2);
2481:   PetscCheckSameComm(snes, 1, y, 3);
2482:   PetscCall(VecValidValues_Internal(x, 2, PETSC_TRUE));

2484:   PetscCall(SNESGetDM(snes, &dm));
2485:   PetscCall(DMGetDMSNES(dm, &sdm));
2486:   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().");
2487:   if (sdm->ops->computefunction) {
2488:     if (sdm->ops->computefunction != SNESObjectiveComputeFunctionDefaultFD) PetscCall(PetscLogEventBegin(SNES_FunctionEval, snes, x, y, 0));
2489:     PetscCall(VecLockReadPush(x));
2490:     /* ensure domainerror is false prior to computefunction evaluation (may not have been reset) */
2491:     snes->domainerror = PETSC_FALSE;
2492:     {
2493:       void           *ctx;
2494:       SNESFunctionFn *computefunction;
2495:       PetscCall(DMSNESGetFunction(dm, &computefunction, &ctx));
2496:       PetscCallBack("SNES callback function", (*computefunction)(snes, x, y, ctx));
2497:     }
2498:     PetscCall(VecLockReadPop(x));
2499:     if (sdm->ops->computefunction != SNESObjectiveComputeFunctionDefaultFD) PetscCall(PetscLogEventEnd(SNES_FunctionEval, snes, x, y, 0));
2500:   } else /* if (snes->vec_rhs) */ {
2501:     PetscCall(MatMult(snes->jacobian, x, y));
2502:   }
2503:   if (snes->vec_rhs) PetscCall(VecAXPY(y, -1.0, snes->vec_rhs));
2504:   snes->nfuncs++;
2505:   /*
2506:      domainerror might not be set on all processes; so we tag vector locally with Inf and the next inner product or norm will
2507:      propagate the value to all processes
2508:   */
2509:   PetscCall(VecFlag(y, snes->domainerror));
2510:   PetscFunctionReturn(PETSC_SUCCESS);
2511: }

2513: /*@
2514:   SNESComputeMFFunction - Calls the function that has been set with `DMSNESSetMFFunction()`.

2516:   Collective

2518:   Input Parameters:
2519: + snes - the `SNES` context
2520: - x    - input vector

2522:   Output Parameter:
2523: . y - output vector

2525:   Level: developer

2527:   Notes:
2528:   `SNESComputeMFFunction()` is used within the matrix-vector products called by the matrix created with `MatCreateSNESMF()`
2529:   so users would not generally call this routine themselves.

2531:   Since this function is intended for use with finite differencing it does not subtract the right-hand side vector provided with `SNESSolve()`
2532:   while `SNESComputeFunction()` does. As such, this routine cannot be used with  `MatMFFDSetBase()` with a provided F function value even if it applies the
2533:   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.

2535: .seealso: [](ch_snes), `SNES`, `SNESSetFunction()`, `SNESGetFunction()`, `SNESComputeFunction()`, `MatCreateSNESMF()`, `DMSNESSetMFFunction()`
2536: @*/
2537: PetscErrorCode SNESComputeMFFunction(SNES snes, Vec x, Vec y)
2538: {
2539:   DM     dm;
2540:   DMSNES sdm;

2542:   PetscFunctionBegin;
2546:   PetscCheckSameComm(snes, 1, x, 2);
2547:   PetscCheckSameComm(snes, 1, y, 3);
2548:   PetscCall(VecValidValues_Internal(x, 2, PETSC_TRUE));

2550:   PetscCall(SNESGetDM(snes, &dm));
2551:   PetscCall(DMGetDMSNES(dm, &sdm));
2552:   PetscCall(PetscLogEventBegin(SNES_FunctionEval, snes, x, y, 0));
2553:   PetscCall(VecLockReadPush(x));
2554:   /* ensure domainerror is false prior to computefunction evaluation (may not have been reset) */
2555:   snes->domainerror = PETSC_FALSE;
2556:   PetscCallBack("SNES callback function", (*sdm->ops->computemffunction)(snes, x, y, sdm->mffunctionctx));
2557:   PetscCall(VecLockReadPop(x));
2558:   PetscCall(PetscLogEventEnd(SNES_FunctionEval, snes, x, y, 0));
2559:   snes->nfuncs++;
2560:   /*
2561:      domainerror might not be set on all processes; so we tag vector locally with Inf and the next inner product or norm will
2562:      propagate the value to all processes
2563:   */
2564:   PetscCall(VecFlag(y, snes->domainerror));
2565:   PetscFunctionReturn(PETSC_SUCCESS);
2566: }

2568: /*@
2569:   SNESComputeNGS - Calls the Gauss-Seidel function that has been set with `SNESSetNGS()`.

2571:   Collective

2573:   Input Parameters:
2574: + snes - the `SNES` context
2575: . x    - input vector
2576: - b    - rhs vector

2578:   Output Parameter:
2579: . x - new solution vector

2581:   Level: developer

2583:   Note:
2584:   `SNESComputeNGS()` is typically used within composed nonlinear solver
2585:   implementations, so most users would not generally call this routine
2586:   themselves.

2588: .seealso: [](ch_snes), `SNESNGSFn`, `SNESSetNGS()`, `SNESComputeFunction()`, `SNESNGS`
2589: @*/
2590: PetscErrorCode SNESComputeNGS(SNES snes, Vec b, Vec x)
2591: {
2592:   DM     dm;
2593:   DMSNES sdm;

2595:   PetscFunctionBegin;
2599:   PetscCheckSameComm(snes, 1, x, 3);
2600:   if (b) PetscCheckSameComm(snes, 1, b, 2);
2601:   if (b) PetscCall(VecValidValues_Internal(b, 2, PETSC_TRUE));
2602:   PetscCall(PetscLogEventBegin(SNES_NGSEval, snes, x, b, 0));
2603:   PetscCall(SNESGetDM(snes, &dm));
2604:   PetscCall(DMGetDMSNES(dm, &sdm));
2605:   PetscCheck(sdm->ops->computegs, PETSC_COMM_SELF, PETSC_ERR_ARG_WRONGSTATE, "Must call SNESSetNGS() before SNESComputeNGS(), likely called from SNESSolve().");
2606:   if (b) PetscCall(VecLockReadPush(b));
2607:   PetscCallBack("SNES callback NGS", (*sdm->ops->computegs)(snes, x, b, sdm->gsctx));
2608:   if (b) PetscCall(VecLockReadPop(b));
2609:   PetscCall(PetscLogEventEnd(SNES_NGSEval, snes, x, b, 0));
2610:   PetscFunctionReturn(PETSC_SUCCESS);
2611: }

2613: static PetscErrorCode SNESComputeFunction_FD(SNES snes, Vec Xin, Vec G)
2614: {
2615:   Vec          X;
2616:   PetscScalar *g;
2617:   PetscReal    f, f2;
2618:   PetscInt     low, high, N, i;
2619:   PetscBool    flg;
2620:   PetscReal    h = .5 * PETSC_SQRT_MACHINE_EPSILON;

2622:   PetscFunctionBegin;
2623:   PetscCall(PetscOptionsGetReal(((PetscObject)snes)->options, ((PetscObject)snes)->prefix, "-snes_fd_delta", &h, &flg));
2624:   PetscCall(VecDuplicate(Xin, &X));
2625:   PetscCall(VecCopy(Xin, X));
2626:   PetscCall(VecGetSize(X, &N));
2627:   PetscCall(VecGetOwnershipRange(X, &low, &high));
2628:   PetscCall(VecSetOption(X, VEC_IGNORE_OFF_PROC_ENTRIES, PETSC_TRUE));
2629:   PetscCall(VecGetArray(G, &g));
2630:   for (i = 0; i < N; i++) {
2631:     PetscCall(VecSetValue(X, i, -h, ADD_VALUES));
2632:     PetscCall(VecAssemblyBegin(X));
2633:     PetscCall(VecAssemblyEnd(X));
2634:     PetscCall(SNESComputeObjective(snes, X, &f));
2635:     PetscCall(VecSetValue(X, i, 2.0 * h, ADD_VALUES));
2636:     PetscCall(VecAssemblyBegin(X));
2637:     PetscCall(VecAssemblyEnd(X));
2638:     PetscCall(SNESComputeObjective(snes, X, &f2));
2639:     PetscCall(VecSetValue(X, i, -h, ADD_VALUES));
2640:     PetscCall(VecAssemblyBegin(X));
2641:     PetscCall(VecAssemblyEnd(X));
2642:     if (i >= low && i < high) g[i - low] = (f2 - f) / (2.0 * h);
2643:   }
2644:   PetscCall(VecRestoreArray(G, &g));
2645:   PetscCall(VecDestroy(&X));
2646:   PetscFunctionReturn(PETSC_SUCCESS);
2647: }

2649: /*@
2650:   SNESTestFunction - Computes the difference between the computed and finite-difference functions

2652:   Collective

2654:   Input Parameter:
2655: . snes - the `SNES` context

2657:   Options Database Keys:
2658: + -snes_test_function      - compare the user provided function with one compute via finite differences to check for errors.
2659: - -snes_test_function_view - display the user provided function, the finite difference function and the difference

2661:   Level: developer

2663: .seealso: [](ch_snes), `SNESTestJacobian()`, `SNESSetFunction()`, `SNESComputeFunction()`
2664: @*/
2665: PetscErrorCode SNESTestFunction(SNES snes)
2666: {
2667:   Vec               x, g1, g2, g3;
2668:   PetscBool         complete_print = PETSC_FALSE;
2669:   PetscReal         hcnorm, fdnorm, hcmax, fdmax, diffmax, diffnorm;
2670:   PetscScalar       dot;
2671:   MPI_Comm          comm;
2672:   PetscViewer       viewer, mviewer;
2673:   PetscViewerFormat format;
2674:   PetscInt          tabs;
2675:   static PetscBool  directionsprinted = PETSC_FALSE;
2676:   SNESObjectiveFn  *objective;

2678:   PetscFunctionBegin;
2679:   PetscCall(SNESGetObjective(snes, &objective, NULL));
2680:   if (!objective) PetscFunctionReturn(PETSC_SUCCESS);

2682:   PetscObjectOptionsBegin((PetscObject)snes);
2683:   PetscCall(PetscOptionsViewer("-snes_test_function_view", "View difference between hand-coded and finite difference function element entries", "None", &mviewer, &format, &complete_print));
2684:   PetscOptionsEnd();

2686:   PetscCall(PetscObjectGetComm((PetscObject)snes, &comm));
2687:   PetscCall(PetscViewerASCIIGetStdout(comm, &viewer));
2688:   PetscCall(PetscViewerASCIIGetTab(viewer, &tabs));
2689:   PetscCall(PetscViewerASCIISetTab(viewer, ((PetscObject)snes)->tablevel));
2690:   PetscCall(PetscViewerASCIIPrintf(viewer, "  ---------- Testing Function -------------\n"));
2691:   if (!complete_print && !directionsprinted) {
2692:     PetscCall(PetscViewerASCIIPrintf(viewer, "  Run with -snes_test_function_view and optionally -snes_test_function <threshold> to show difference\n"));
2693:     PetscCall(PetscViewerASCIIPrintf(viewer, "    of hand-coded and finite difference function entries greater than <threshold>.\n"));
2694:   }
2695:   if (!directionsprinted) {
2696:     PetscCall(PetscViewerASCIIPrintf(viewer, "  Testing hand-coded Function, if (for double precision runs) ||F - Ffd||/||F|| is\n"));
2697:     PetscCall(PetscViewerASCIIPrintf(viewer, "    O(1.e-8), the hand-coded Function is probably correct.\n"));
2698:     directionsprinted = PETSC_TRUE;
2699:   }
2700:   if (complete_print) PetscCall(PetscViewerPushFormat(mviewer, format));

2702:   PetscCall(SNESGetSolution(snes, &x));
2703:   PetscCall(VecDuplicate(x, &g1));
2704:   PetscCall(VecDuplicate(x, &g2));
2705:   PetscCall(VecDuplicate(x, &g3));
2706:   PetscCall(SNESComputeFunction(snes, x, g1));
2707:   PetscCall(SNESComputeFunction_FD(snes, x, g2));

2709:   PetscCall(VecNorm(g2, NORM_2, &fdnorm));
2710:   PetscCall(VecNorm(g1, NORM_2, &hcnorm));
2711:   PetscCall(VecNorm(g2, NORM_INFINITY, &fdmax));
2712:   PetscCall(VecNorm(g1, NORM_INFINITY, &hcmax));
2713:   PetscCall(VecDot(g1, g2, &dot));
2714:   PetscCall(VecCopy(g1, g3));
2715:   PetscCall(VecAXPY(g3, -1.0, g2));
2716:   PetscCall(VecNorm(g3, NORM_2, &diffnorm));
2717:   PetscCall(VecNorm(g3, NORM_INFINITY, &diffmax));
2718:   PetscCall(PetscViewerASCIIPrintf(viewer, "  ||Ffd|| %g, ||F|| = %g, angle cosine = (Ffd'F)/||Ffd||||F|| = %g\n", (double)fdnorm, (double)hcnorm, (double)(PetscRealPart(dot) / (fdnorm * hcnorm))));
2719:   PetscCall(PetscViewerASCIIPrintf(viewer, "  2-norm ||F - Ffd||/||F|| = %g, ||F - Ffd|| = %g\n", (double)(diffnorm / PetscMax(hcnorm, fdnorm)), (double)diffnorm));
2720:   PetscCall(PetscViewerASCIIPrintf(viewer, "  max-norm ||F - Ffd||/||F|| = %g, ||F - Ffd|| = %g\n", (double)(diffmax / PetscMax(hcmax, fdmax)), (double)diffmax));

2722:   if (complete_print) {
2723:     PetscCall(PetscViewerASCIIPrintf(viewer, "  Hand-coded function ----------\n"));
2724:     PetscCall(VecView(g1, mviewer));
2725:     PetscCall(PetscViewerASCIIPrintf(viewer, "  Finite difference function ----------\n"));
2726:     PetscCall(VecView(g2, mviewer));
2727:     PetscCall(PetscViewerASCIIPrintf(viewer, "  Hand-coded minus finite-difference function ----------\n"));
2728:     PetscCall(VecView(g3, mviewer));
2729:   }
2730:   PetscCall(VecDestroy(&g1));
2731:   PetscCall(VecDestroy(&g2));
2732:   PetscCall(VecDestroy(&g3));

2734:   if (complete_print) {
2735:     PetscCall(PetscViewerPopFormat(mviewer));
2736:     PetscCall(PetscViewerDestroy(&mviewer));
2737:   }
2738:   PetscCall(PetscViewerASCIISetTab(viewer, tabs));
2739:   PetscFunctionReturn(PETSC_SUCCESS);
2740: }

2742: /*@
2743:   SNESTestJacobian - Computes the difference between the computed and finite-difference Jacobians

2745:   Collective

2747:   Input Parameter:
2748: . snes - the `SNES` context

2750:   Output Parameters:
2751: + Jnorm    - the Frobenius norm of the computed Jacobian, or `NULL`
2752: - diffNorm - the Frobenius norm of the difference of the computed and finite-difference Jacobians, or `NULL`

2754:   Options Database Keys:
2755: + -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.
2756: - -snes_test_jacobian_view                 - display the user provided Jacobian, the finite difference Jacobian and the difference

2758:   Level: developer

2760:   Note:
2761:   Directions and norms are printed to stdout if `diffNorm` is `NULL`.

2763: .seealso: [](ch_snes), `SNESTestFunction()`, `SNESSetJacobian()`, `SNESComputeJacobian()`
2764: @*/
2765: PetscErrorCode SNESTestJacobian(SNES snes, PetscReal *Jnorm, PetscReal *diffNorm)
2766: {
2767:   Mat               A, B, C, D, jacobian;
2768:   Vec               x = snes->vec_sol, f;
2769:   PetscReal         nrm, gnorm;
2770:   PetscReal         threshold = 1.e-5;
2771:   MatType           mattype;
2772:   PetscInt          m, n, M, N;
2773:   void             *functx;
2774:   PetscBool         complete_print = PETSC_FALSE, threshold_print = PETSC_FALSE, flg, istranspose;
2775:   PetscBool         silent = diffNorm != PETSC_NULLPTR ? PETSC_TRUE : PETSC_FALSE;
2776:   PetscViewer       viewer, mviewer;
2777:   MPI_Comm          comm;
2778:   PetscInt          tabs;
2779:   static PetscBool  directionsprinted = PETSC_FALSE;
2780:   PetscViewerFormat format;

2782:   PetscFunctionBegin;
2783:   PetscObjectOptionsBegin((PetscObject)snes);
2784:   PetscCall(PetscOptionsReal("-snes_test_jacobian", "Threshold for element difference between hand-coded and finite difference being meaningful", "None", threshold, &threshold, NULL));
2785:   PetscCall(PetscOptionsDeprecated("-snes_test_jacobian_display", "-snes_test_jacobian_view", "3.13", NULL));
2786:   PetscCall(PetscOptionsViewer("-snes_test_jacobian_view", "View difference between hand-coded and finite difference Jacobians element entries", "None", &mviewer, &format, &complete_print));
2787:   PetscCall(PetscOptionsDeprecated("-snes_test_jacobian_display_threshold", "-snes_test_jacobian", "3.13", "-snes_test_jacobian accepts an optional threshold (since v3.10)"));
2788:   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));
2789:   PetscOptionsEnd();

2791:   PetscCall(PetscObjectGetComm((PetscObject)snes, &comm));
2792:   PetscCall(PetscViewerASCIIGetStdout(comm, &viewer));
2793:   PetscCall(PetscViewerASCIIGetTab(viewer, &tabs));
2794:   PetscCall(PetscViewerASCIISetTab(viewer, ((PetscObject)snes)->tablevel));
2795:   if (!silent) PetscCall(PetscViewerASCIIPrintf(viewer, "  ---------- Testing Jacobian -------------\n"));
2796:   if (!complete_print && !silent && !directionsprinted) {
2797:     PetscCall(PetscViewerASCIIPrintf(viewer, "  Run with -snes_test_jacobian_view and optionally -snes_test_jacobian <threshold> to show difference\n"));
2798:     PetscCall(PetscViewerASCIIPrintf(viewer, "    of hand-coded and finite difference Jacobian entries greater than <threshold>.\n"));
2799:   }
2800:   if (!directionsprinted && !silent) {
2801:     PetscCall(PetscViewerASCIIPrintf(viewer, "  Testing hand-coded Jacobian, if (for double precision runs) ||J - Jfd||_F/||J||_F is\n"));
2802:     PetscCall(PetscViewerASCIIPrintf(viewer, "    O(1.e-8), the hand-coded Jacobian is probably correct.\n"));
2803:     directionsprinted = PETSC_TRUE;
2804:   }
2805:   if (complete_print) PetscCall(PetscViewerPushFormat(mviewer, format));

2807:   PetscCall(PetscObjectTypeCompare((PetscObject)snes->jacobian, MATMFFD, &flg));
2808:   if (!flg) jacobian = snes->jacobian;
2809:   else jacobian = snes->jacobian_pre;

2811:   if (!x) PetscCall(MatCreateVecs(jacobian, &x, NULL));
2812:   else PetscCall(PetscObjectReference((PetscObject)x));
2813:   PetscCall(VecDuplicate(x, &f));

2815:   /* evaluate the function at this point because SNESComputeJacobianDefault() assumes that the function has been evaluated and put into snes->vec_func */
2816:   PetscCall(SNESComputeFunction(snes, x, f));
2817:   PetscCall(VecDestroy(&f));
2818:   PetscCall(PetscObjectTypeCompare((PetscObject)snes, SNESKSPTRANSPOSEONLY, &istranspose));
2819:   while (jacobian) {
2820:     Mat JT = NULL, Jsave = NULL;

2822:     if (istranspose) {
2823:       PetscCall(MatCreateTranspose(jacobian, &JT));
2824:       Jsave    = jacobian;
2825:       jacobian = JT;
2826:     }
2827:     PetscCall(PetscObjectBaseTypeCompareAny((PetscObject)jacobian, &flg, MATSEQAIJ, MATMPIAIJ, MATSEQDENSE, MATMPIDENSE, MATSEQBAIJ, MATMPIBAIJ, MATSEQSBAIJ, MATMPISBAIJ, ""));
2828:     if (flg) {
2829:       A = jacobian;
2830:       PetscCall(PetscObjectReference((PetscObject)A));
2831:     } else {
2832:       PetscCall(MatComputeOperator(jacobian, MATAIJ, &A));
2833:     }

2835:     PetscCall(MatGetType(A, &mattype));
2836:     PetscCall(MatGetSize(A, &M, &N));
2837:     PetscCall(MatGetLocalSize(A, &m, &n));
2838:     PetscCall(MatCreate(PetscObjectComm((PetscObject)A), &B));
2839:     PetscCall(MatSetType(B, mattype));
2840:     PetscCall(MatSetSizes(B, m, n, M, N));
2841:     PetscCall(MatSetBlockSizesFromMats(B, A, A));
2842:     PetscCall(MatSetUp(B));
2843:     PetscCall(MatSetOption(B, MAT_NEW_NONZERO_ALLOCATION_ERR, PETSC_FALSE));

2845:     PetscCall(SNESGetFunction(snes, NULL, NULL, &functx));
2846:     PetscCall(SNESComputeJacobianDefault(snes, x, B, B, functx));

2848:     PetscCall(MatDuplicate(B, MAT_COPY_VALUES, &D));
2849:     PetscCall(MatAYPX(D, -1.0, A, DIFFERENT_NONZERO_PATTERN));
2850:     PetscCall(MatNorm(D, NORM_FROBENIUS, &nrm));
2851:     PetscCall(MatNorm(A, NORM_FROBENIUS, &gnorm));
2852:     PetscCall(MatDestroy(&D));
2853:     if (!gnorm) gnorm = 1; /* just in case */
2854:     if (!silent) PetscCall(PetscViewerASCIIPrintf(viewer, "  ||J - Jfd||_F/||J||_F = %g, ||J - Jfd||_F = %g\n", (double)(nrm / gnorm), (double)nrm));
2855:     if (complete_print) {
2856:       PetscCall(PetscViewerASCIIPrintf(viewer, "  Hand-coded Jacobian ----------\n"));
2857:       PetscCall(MatView(A, mviewer));
2858:       PetscCall(PetscViewerASCIIPrintf(viewer, "  Finite difference Jacobian ----------\n"));
2859:       PetscCall(MatView(B, mviewer));
2860:     }

2862:     if (threshold_print || complete_print) {
2863:       PetscInt           Istart, Iend, *ccols, bncols, cncols, j, row;
2864:       PetscScalar       *cvals;
2865:       const PetscInt    *bcols;
2866:       const PetscScalar *bvals;

2868:       PetscCall(MatCreate(PetscObjectComm((PetscObject)A), &C));
2869:       PetscCall(MatSetType(C, mattype));
2870:       PetscCall(MatSetSizes(C, m, n, M, N));
2871:       PetscCall(MatSetBlockSizesFromMats(C, A, A));
2872:       PetscCall(MatSetUp(C));
2873:       PetscCall(MatSetOption(C, MAT_NEW_NONZERO_ALLOCATION_ERR, PETSC_FALSE));

2875:       PetscCall(MatAYPX(B, -1.0, A, DIFFERENT_NONZERO_PATTERN));
2876:       PetscCall(MatGetOwnershipRange(B, &Istart, &Iend));

2878:       for (row = Istart; row < Iend; row++) {
2879:         PetscCall(MatGetRow(B, row, &bncols, &bcols, &bvals));
2880:         PetscCall(PetscMalloc2(bncols, &ccols, bncols, &cvals));
2881:         for (j = 0, cncols = 0; j < bncols; j++) {
2882:           if (PetscAbsScalar(bvals[j]) > threshold) {
2883:             ccols[cncols] = bcols[j];
2884:             cvals[cncols] = bvals[j];
2885:             cncols += 1;
2886:           }
2887:         }
2888:         if (cncols) PetscCall(MatSetValues(C, 1, &row, cncols, ccols, cvals, INSERT_VALUES));
2889:         PetscCall(MatRestoreRow(B, row, &bncols, &bcols, &bvals));
2890:         PetscCall(PetscFree2(ccols, cvals));
2891:       }
2892:       PetscCall(MatAssemblyBegin(C, MAT_FINAL_ASSEMBLY));
2893:       PetscCall(MatAssemblyEnd(C, MAT_FINAL_ASSEMBLY));
2894:       PetscCall(PetscViewerASCIIPrintf(viewer, "  Hand-coded minus finite-difference Jacobian with tolerance %g ----------\n", (double)threshold));
2895:       PetscCall(MatView(C, complete_print ? mviewer : viewer));
2896:       PetscCall(MatDestroy(&C));
2897:     }
2898:     PetscCall(MatDestroy(&A));
2899:     PetscCall(MatDestroy(&B));
2900:     PetscCall(MatDestroy(&JT));
2901:     if (Jsave) jacobian = Jsave;
2902:     if (jacobian != snes->jacobian_pre) {
2903:       jacobian = snes->jacobian_pre;
2904:       if (!silent) PetscCall(PetscViewerASCIIPrintf(viewer, "  ---------- Testing Jacobian for preconditioner -------------\n"));
2905:     } else jacobian = NULL;
2906:   }
2907:   PetscCall(VecDestroy(&x));
2908:   if (complete_print) PetscCall(PetscViewerPopFormat(mviewer));
2909:   if (mviewer) PetscCall(PetscViewerDestroy(&mviewer));
2910:   PetscCall(PetscViewerASCIISetTab(viewer, tabs));

2912:   if (Jnorm) *Jnorm = gnorm;
2913:   if (diffNorm) *diffNorm = nrm;
2914:   PetscFunctionReturn(PETSC_SUCCESS);
2915: }

2917: /*@
2918:   SNESComputeJacobian - Computes the Jacobian matrix that has been set with `SNESSetJacobian()`.

2920:   Collective

2922:   Input Parameters:
2923: + snes - the `SNES` context
2924: - X    - input vector

2926:   Output Parameters:
2927: + A - Jacobian matrix
2928: - B - optional matrix for building the preconditioner, usually the same as `A`

2930:   Options Database Keys:
2931: + -snes_lag_preconditioner <lag>           - how often to rebuild preconditioner
2932: . -snes_lag_jacobian <lag>                 - how often to rebuild Jacobian
2933: . -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.
2934: . -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
2935: . -snes_compare_explicit                   - Compare the computed Jacobian to the finite difference Jacobian and output the differences
2936: . -snes_compare_explicit_draw              - Compare the computed Jacobian to the finite difference Jacobian and draw the result
2937: . -snes_compare_explicit_contour           - Compare the computed Jacobian to the finite difference Jacobian and draw a contour plot with the result
2938: . -snes_compare_operator                   - Make the comparison options above use the operator instead of the matrix used to construct the preconditioner
2939: . -snes_compare_coloring                   - Compute the finite difference Jacobian using coloring and display norms of difference
2940: . -snes_compare_coloring_display           - Compute the finite difference Jacobian using coloring and display verbose differences
2941: . -snes_compare_coloring_threshold         - Display only those matrix entries that differ by more than a given threshold
2942: . -snes_compare_coloring_threshold_atol    - Absolute tolerance for difference in matrix entries to be displayed by `-snes_compare_coloring_threshold`
2943: . -snes_compare_coloring_threshold_rtol    - Relative tolerance for difference in matrix entries to be displayed by `-snes_compare_coloring_threshold`
2944: . -snes_compare_coloring_draw              - Compute the finite difference Jacobian using coloring and draw differences
2945: - -snes_compare_coloring_draw_contour      - Compute the finite difference Jacobian using coloring and show contours of matrices and differences

2947:   Level: developer

2949:   Note:
2950:   Most users should not need to explicitly call this routine, as it
2951:   is used internally within the nonlinear solvers.

2953:   Developer Note:
2954:   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
2955:   with the `SNESType` of test that has been removed.

2957: .seealso: [](ch_snes), `SNESSetJacobian()`, `KSPSetOperators()`, `MatStructure`, `SNESSetLagPreconditioner()`, `SNESSetLagJacobian()`
2958: @*/
2959: PetscErrorCode SNESComputeJacobian(SNES snes, Vec X, Mat A, Mat B)
2960: {
2961:   PetscBool flag;
2962:   DM        dm;
2963:   DMSNES    sdm;
2964:   KSP       ksp;

2966:   PetscFunctionBegin;
2969:   PetscCheckSameComm(snes, 1, X, 2);
2970:   PetscCall(VecValidValues_Internal(X, 2, PETSC_TRUE));
2971:   PetscCall(SNESGetDM(snes, &dm));
2972:   PetscCall(DMGetDMSNES(dm, &sdm));

2974:   /* make sure that MatAssemblyBegin/End() is called on A matrix if it is matrix-free */
2975:   if (snes->lagjacobian == -2) {
2976:     snes->lagjacobian = -1;

2978:     PetscCall(PetscInfo(snes, "Recomputing Jacobian/preconditioner because lag is -2 (means compute Jacobian, but then never again) \n"));
2979:   } else if (snes->lagjacobian == -1) {
2980:     PetscCall(PetscInfo(snes, "Reusing Jacobian/preconditioner because lag is -1\n"));
2981:     PetscCall(PetscObjectTypeCompare((PetscObject)A, MATMFFD, &flag));
2982:     if (flag) {
2983:       PetscCall(MatAssemblyBegin(A, MAT_FINAL_ASSEMBLY));
2984:       PetscCall(MatAssemblyEnd(A, MAT_FINAL_ASSEMBLY));
2985:     }
2986:     PetscFunctionReturn(PETSC_SUCCESS);
2987:   } else if (snes->lagjacobian > 1 && (snes->iter + snes->jac_iter) % snes->lagjacobian) {
2988:     PetscCall(PetscInfo(snes, "Reusing Jacobian/preconditioner because lag is %" PetscInt_FMT " and SNES iteration is %" PetscInt_FMT "\n", snes->lagjacobian, snes->iter));
2989:     PetscCall(PetscObjectTypeCompare((PetscObject)A, MATMFFD, &flag));
2990:     if (flag) {
2991:       PetscCall(MatAssemblyBegin(A, MAT_FINAL_ASSEMBLY));
2992:       PetscCall(MatAssemblyEnd(A, MAT_FINAL_ASSEMBLY));
2993:     }
2994:     PetscFunctionReturn(PETSC_SUCCESS);
2995:   }
2996:   if (snes->npc && snes->npcside == PC_LEFT) {
2997:     PetscCall(MatAssemblyBegin(A, MAT_FINAL_ASSEMBLY));
2998:     PetscCall(MatAssemblyEnd(A, MAT_FINAL_ASSEMBLY));
2999:     PetscFunctionReturn(PETSC_SUCCESS);
3000:   }

3002:   PetscCall(PetscLogEventBegin(SNES_JacobianEval, snes, X, A, B));
3003:   PetscCall(VecLockReadPush(X));
3004:   {
3005:     void           *ctx;
3006:     SNESJacobianFn *J;
3007:     PetscCall(DMSNESGetJacobian(dm, &J, &ctx));
3008:     PetscCallBack("SNES callback Jacobian", (*J)(snes, X, A, B, ctx));
3009:   }
3010:   PetscCall(VecLockReadPop(X));
3011:   PetscCall(PetscLogEventEnd(SNES_JacobianEval, snes, X, A, B));

3013:   /* attach latest linearization point to the matrix used to construct the preconditioner */
3014:   PetscCall(PetscObjectCompose((PetscObject)B, "__SNES_latest_X", (PetscObject)X));

3016:   /* the next line ensures that snes->ksp exists */
3017:   PetscCall(SNESGetKSP(snes, &ksp));
3018:   if (snes->lagpreconditioner == -2) {
3019:     PetscCall(PetscInfo(snes, "Rebuilding preconditioner exactly once since lag is -2\n"));
3020:     PetscCall(KSPSetReusePreconditioner(snes->ksp, PETSC_FALSE));
3021:     snes->lagpreconditioner = -1;
3022:   } else if (snes->lagpreconditioner == -1) {
3023:     PetscCall(PetscInfo(snes, "Reusing preconditioner because lag is -1\n"));
3024:     PetscCall(KSPSetReusePreconditioner(snes->ksp, PETSC_TRUE));
3025:   } else if (snes->lagpreconditioner > 1 && (snes->iter + snes->pre_iter) % snes->lagpreconditioner) {
3026:     PetscCall(PetscInfo(snes, "Reusing preconditioner because lag is %" PetscInt_FMT " and SNES iteration is %" PetscInt_FMT "\n", snes->lagpreconditioner, snes->iter));
3027:     PetscCall(KSPSetReusePreconditioner(snes->ksp, PETSC_TRUE));
3028:   } else {
3029:     PetscCall(PetscInfo(snes, "Rebuilding preconditioner\n"));
3030:     PetscCall(KSPSetReusePreconditioner(snes->ksp, PETSC_FALSE));
3031:   }

3033:   /* monkey business to allow testing Jacobians in multilevel solvers.
3034:      This is needed because the SNESTestXXX interface does not accept vectors and matrices */
3035:   {
3036:     Vec xsave            = snes->vec_sol;
3037:     Mat jacobiansave     = snes->jacobian;
3038:     Mat jacobian_presave = snes->jacobian_pre;

3040:     snes->vec_sol      = X;
3041:     snes->jacobian     = A;
3042:     snes->jacobian_pre = B;
3043:     if (snes->testFunc) PetscCall(SNESTestFunction(snes));
3044:     if (snes->testJac) PetscCall(SNESTestJacobian(snes, NULL, NULL));

3046:     snes->vec_sol      = xsave;
3047:     snes->jacobian     = jacobiansave;
3048:     snes->jacobian_pre = jacobian_presave;
3049:   }

3051:   {
3052:     PetscBool flag = PETSC_FALSE, flag_draw = PETSC_FALSE, flag_contour = PETSC_FALSE, flag_operator = PETSC_FALSE;
3053:     PetscCall(PetscOptionsCreateViewer(PetscObjectComm((PetscObject)snes), ((PetscObject)snes)->options, ((PetscObject)snes)->prefix, "-snes_compare_explicit", NULL, NULL, &flag));
3054:     PetscCall(PetscOptionsCreateViewer(PetscObjectComm((PetscObject)snes), ((PetscObject)snes)->options, ((PetscObject)snes)->prefix, "-snes_compare_explicit_draw", NULL, NULL, &flag_draw));
3055:     PetscCall(PetscOptionsCreateViewer(PetscObjectComm((PetscObject)snes), ((PetscObject)snes)->options, ((PetscObject)snes)->prefix, "-snes_compare_explicit_draw_contour", NULL, NULL, &flag_contour));
3056:     PetscCall(PetscOptionsCreateViewer(PetscObjectComm((PetscObject)snes), ((PetscObject)snes)->options, ((PetscObject)snes)->prefix, "-snes_compare_operator", NULL, NULL, &flag_operator));
3057:     if (flag || flag_draw || flag_contour) {
3058:       Mat         Bexp_mine = NULL, Bexp, FDexp;
3059:       PetscViewer vdraw, vstdout;
3060:       PetscBool   flg;
3061:       if (flag_operator) {
3062:         PetscCall(MatComputeOperator(A, MATAIJ, &Bexp_mine));
3063:         Bexp = Bexp_mine;
3064:       } else {
3065:         /* See if the matrix used to construct the preconditioner can be viewed and added directly */
3066:         PetscCall(PetscObjectBaseTypeCompareAny((PetscObject)B, &flg, MATSEQAIJ, MATMPIAIJ, MATSEQDENSE, MATMPIDENSE, MATSEQBAIJ, MATMPIBAIJ, MATSEQSBAIJ, MATMPIBAIJ, ""));
3067:         if (flg) Bexp = B;
3068:         else {
3069:           /* If the "preconditioning" matrix is itself MATSHELL or some other type without direct support */
3070:           PetscCall(MatComputeOperator(B, MATAIJ, &Bexp_mine));
3071:           Bexp = Bexp_mine;
3072:         }
3073:       }
3074:       PetscCall(MatConvert(Bexp, MATSAME, MAT_INITIAL_MATRIX, &FDexp));
3075:       PetscCall(SNESComputeJacobianDefault(snes, X, FDexp, FDexp, NULL));
3076:       PetscCall(PetscViewerASCIIGetStdout(PetscObjectComm((PetscObject)snes), &vstdout));
3077:       if (flag_draw || flag_contour) {
3078:         PetscCall(PetscViewerDrawOpen(PetscObjectComm((PetscObject)snes), NULL, "Explicit Jacobians", PETSC_DECIDE, PETSC_DECIDE, 300, 300, &vdraw));
3079:         if (flag_contour) PetscCall(PetscViewerPushFormat(vdraw, PETSC_VIEWER_DRAW_CONTOUR));
3080:       } else vdraw = NULL;
3081:       PetscCall(PetscViewerASCIIPrintf(vstdout, "Explicit %s\n", flag_operator ? "Jacobian" : "preconditioning Jacobian"));
3082:       if (flag) PetscCall(MatView(Bexp, vstdout));
3083:       if (vdraw) PetscCall(MatView(Bexp, vdraw));
3084:       PetscCall(PetscViewerASCIIPrintf(vstdout, "Finite difference Jacobian\n"));
3085:       if (flag) PetscCall(MatView(FDexp, vstdout));
3086:       if (vdraw) PetscCall(MatView(FDexp, vdraw));
3087:       PetscCall(MatAYPX(FDexp, -1.0, Bexp, SAME_NONZERO_PATTERN));
3088:       PetscCall(PetscViewerASCIIPrintf(vstdout, "User-provided matrix minus finite difference Jacobian\n"));
3089:       if (flag) PetscCall(MatView(FDexp, vstdout));
3090:       if (vdraw) { /* Always use contour for the difference */
3091:         PetscCall(PetscViewerPushFormat(vdraw, PETSC_VIEWER_DRAW_CONTOUR));
3092:         PetscCall(MatView(FDexp, vdraw));
3093:         PetscCall(PetscViewerPopFormat(vdraw));
3094:       }
3095:       if (flag_contour) PetscCall(PetscViewerPopFormat(vdraw));
3096:       PetscCall(PetscViewerDestroy(&vdraw));
3097:       PetscCall(MatDestroy(&Bexp_mine));
3098:       PetscCall(MatDestroy(&FDexp));
3099:     }
3100:   }
3101:   {
3102:     PetscBool flag = PETSC_FALSE, flag_display = PETSC_FALSE, flag_draw = PETSC_FALSE, flag_contour = PETSC_FALSE, flag_threshold = PETSC_FALSE;
3103:     PetscReal threshold_atol = PETSC_SQRT_MACHINE_EPSILON, threshold_rtol = 10 * PETSC_SQRT_MACHINE_EPSILON;
3104:     PetscCall(PetscOptionsCreateViewer(PetscObjectComm((PetscObject)snes), ((PetscObject)snes)->options, ((PetscObject)snes)->prefix, "-snes_compare_coloring", NULL, NULL, &flag));
3105:     PetscCall(PetscOptionsCreateViewer(PetscObjectComm((PetscObject)snes), ((PetscObject)snes)->options, ((PetscObject)snes)->prefix, "-snes_compare_coloring_display", NULL, NULL, &flag_display));
3106:     PetscCall(PetscOptionsCreateViewer(PetscObjectComm((PetscObject)snes), ((PetscObject)snes)->options, ((PetscObject)snes)->prefix, "-snes_compare_coloring_draw", NULL, NULL, &flag_draw));
3107:     PetscCall(PetscOptionsCreateViewer(PetscObjectComm((PetscObject)snes), ((PetscObject)snes)->options, ((PetscObject)snes)->prefix, "-snes_compare_coloring_draw_contour", NULL, NULL, &flag_contour));
3108:     PetscCall(PetscOptionsCreateViewer(PetscObjectComm((PetscObject)snes), ((PetscObject)snes)->options, ((PetscObject)snes)->prefix, "-snes_compare_coloring_threshold", NULL, NULL, &flag_threshold));
3109:     if (flag_threshold) {
3110:       PetscCall(PetscOptionsGetReal(((PetscObject)snes)->options, ((PetscObject)snes)->prefix, "-snes_compare_coloring_threshold_rtol", &threshold_rtol, NULL));
3111:       PetscCall(PetscOptionsGetReal(((PetscObject)snes)->options, ((PetscObject)snes)->prefix, "-snes_compare_coloring_threshold_atol", &threshold_atol, NULL));
3112:     }
3113:     if (flag || flag_display || flag_draw || flag_contour || flag_threshold) {
3114:       Mat             Bfd;
3115:       PetscViewer     vdraw, vstdout;
3116:       MatColoring     coloring;
3117:       ISColoring      iscoloring;
3118:       MatFDColoring   matfdcoloring;
3119:       SNESFunctionFn *func;
3120:       void           *funcctx;
3121:       PetscReal       norm1, norm2, normmax;

3123:       PetscCall(MatDuplicate(B, MAT_DO_NOT_COPY_VALUES, &Bfd));
3124:       PetscCall(MatColoringCreate(Bfd, &coloring));
3125:       PetscCall(MatColoringSetType(coloring, MATCOLORINGSL));
3126:       PetscCall(MatColoringSetFromOptions(coloring));
3127:       PetscCall(MatColoringApply(coloring, &iscoloring));
3128:       PetscCall(MatColoringDestroy(&coloring));
3129:       PetscCall(MatFDColoringCreate(Bfd, iscoloring, &matfdcoloring));
3130:       PetscCall(MatFDColoringSetFromOptions(matfdcoloring));
3131:       PetscCall(MatFDColoringSetUp(Bfd, iscoloring, matfdcoloring));
3132:       PetscCall(ISColoringDestroy(&iscoloring));

3134:       /* This method of getting the function is currently unreliable since it doesn't work for DM local functions. */
3135:       PetscCall(SNESGetFunction(snes, NULL, &func, &funcctx));
3136:       PetscCall(MatFDColoringSetFunction(matfdcoloring, (MatFDColoringFn *)func, funcctx));
3137:       PetscCall(PetscObjectSetOptionsPrefix((PetscObject)matfdcoloring, ((PetscObject)snes)->prefix));
3138:       PetscCall(PetscObjectAppendOptionsPrefix((PetscObject)matfdcoloring, "coloring_"));
3139:       PetscCall(MatFDColoringSetFromOptions(matfdcoloring));
3140:       PetscCall(MatFDColoringApply(Bfd, matfdcoloring, X, snes));
3141:       PetscCall(MatFDColoringDestroy(&matfdcoloring));

3143:       PetscCall(PetscViewerASCIIGetStdout(PetscObjectComm((PetscObject)snes), &vstdout));
3144:       if (flag_draw || flag_contour) {
3145:         PetscCall(PetscViewerDrawOpen(PetscObjectComm((PetscObject)snes), NULL, "Colored Jacobians", PETSC_DECIDE, PETSC_DECIDE, 300, 300, &vdraw));
3146:         if (flag_contour) PetscCall(PetscViewerPushFormat(vdraw, PETSC_VIEWER_DRAW_CONTOUR));
3147:       } else vdraw = NULL;
3148:       PetscCall(PetscViewerASCIIPrintf(vstdout, "Explicit preconditioning Jacobian\n"));
3149:       if (flag_display) PetscCall(MatView(B, vstdout));
3150:       if (vdraw) PetscCall(MatView(B, vdraw));
3151:       PetscCall(PetscViewerASCIIPrintf(vstdout, "Colored Finite difference Jacobian\n"));
3152:       if (flag_display) PetscCall(MatView(Bfd, vstdout));
3153:       if (vdraw) PetscCall(MatView(Bfd, vdraw));
3154:       PetscCall(MatAYPX(Bfd, -1.0, B, SAME_NONZERO_PATTERN));
3155:       PetscCall(MatNorm(Bfd, NORM_1, &norm1));
3156:       PetscCall(MatNorm(Bfd, NORM_FROBENIUS, &norm2));
3157:       PetscCall(MatNorm(Bfd, NORM_MAX, &normmax));
3158:       PetscCall(PetscViewerASCIIPrintf(vstdout, "User-provided matrix minus finite difference Jacobian, norm1=%g normFrob=%g normmax=%g\n", (double)norm1, (double)norm2, (double)normmax));
3159:       if (flag_display) PetscCall(MatView(Bfd, vstdout));
3160:       if (vdraw) { /* Always use contour for the difference */
3161:         PetscCall(PetscViewerPushFormat(vdraw, PETSC_VIEWER_DRAW_CONTOUR));
3162:         PetscCall(MatView(Bfd, vdraw));
3163:         PetscCall(PetscViewerPopFormat(vdraw));
3164:       }
3165:       if (flag_contour) PetscCall(PetscViewerPopFormat(vdraw));

3167:       if (flag_threshold) {
3168:         PetscInt bs, rstart, rend, i;
3169:         PetscCall(MatGetBlockSize(B, &bs));
3170:         PetscCall(MatGetOwnershipRange(B, &rstart, &rend));
3171:         for (i = rstart; i < rend; i++) {
3172:           const PetscScalar *ba, *ca;
3173:           const PetscInt    *bj, *cj;
3174:           PetscInt           bn, cn, j, maxentrycol = -1, maxdiffcol = -1, maxrdiffcol = -1;
3175:           PetscReal          maxentry = 0, maxdiff = 0, maxrdiff = 0;
3176:           PetscCall(MatGetRow(B, i, &bn, &bj, &ba));
3177:           PetscCall(MatGetRow(Bfd, i, &cn, &cj, &ca));
3178:           PetscCheck(bn == cn, ((PetscObject)A)->comm, PETSC_ERR_PLIB, "Unexpected different nonzero pattern in -snes_compare_coloring_threshold");
3179:           for (j = 0; j < bn; j++) {
3180:             PetscReal rdiff = PetscAbsScalar(ca[j]) / (threshold_atol + threshold_rtol * PetscAbsScalar(ba[j]));
3181:             if (PetscAbsScalar(ba[j]) > PetscAbs(maxentry)) {
3182:               maxentrycol = bj[j];
3183:               maxentry    = PetscRealPart(ba[j]);
3184:             }
3185:             if (PetscAbsScalar(ca[j]) > PetscAbs(maxdiff)) {
3186:               maxdiffcol = bj[j];
3187:               maxdiff    = PetscRealPart(ca[j]);
3188:             }
3189:             if (rdiff > maxrdiff) {
3190:               maxrdiffcol = bj[j];
3191:               maxrdiff    = rdiff;
3192:             }
3193:           }
3194:           if (maxrdiff > 1) {
3195:             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));
3196:             for (j = 0; j < bn; j++) {
3197:               PetscReal rdiff;
3198:               rdiff = PetscAbsScalar(ca[j]) / (threshold_atol + threshold_rtol * PetscAbsScalar(ba[j]));
3199:               if (rdiff > 1) PetscCall(PetscViewerASCIIPrintf(vstdout, " (%" PetscInt_FMT ",%g:%g)", bj[j], (double)PetscRealPart(ba[j]), (double)PetscRealPart(ca[j])));
3200:             }
3201:             PetscCall(PetscViewerASCIIPrintf(vstdout, "\n"));
3202:           }
3203:           PetscCall(MatRestoreRow(B, i, &bn, &bj, &ba));
3204:           PetscCall(MatRestoreRow(Bfd, i, &cn, &cj, &ca));
3205:         }
3206:       }
3207:       PetscCall(PetscViewerDestroy(&vdraw));
3208:       PetscCall(MatDestroy(&Bfd));
3209:     }
3210:   }
3211:   PetscFunctionReturn(PETSC_SUCCESS);
3212: }

3214: /*@C
3215:   SNESSetJacobian - Sets the function to compute Jacobian as well as the
3216:   location to store the matrix.

3218:   Logically Collective

3220:   Input Parameters:
3221: + snes - the `SNES` context
3222: . Amat - the matrix that defines the (approximate) Jacobian
3223: . Pmat - the matrix to be used in constructing the preconditioner, usually the same as `Amat`.
3224: . J    - Jacobian evaluation routine (if `NULL` then `SNES` retains any previously set value), see `SNESJacobianFn` for details
3225: - ctx  - [optional] user-defined context for private data for the
3226:          Jacobian evaluation routine (may be `NULL`) (if `NULL` then `SNES` retains any previously set value)

3228:   Level: beginner

3230:   Notes:
3231:   If the `Amat` matrix and `Pmat` matrix are different you must call `MatAssemblyBegin()`/`MatAssemblyEnd()` on
3232:   each matrix.

3234:   If you know the operator `Amat` has a null space you can use `MatSetNullSpace()` and `MatSetTransposeNullSpace()` to supply the null
3235:   space to `Amat` and the `KSP` solvers will automatically use that null space as needed during the solution process.

3237:   If using `SNESComputeJacobianDefaultColor()` to assemble a Jacobian, the `ctx` argument
3238:   must be a `MatFDColoring`.

3240:   Other defect-correction schemes can be used by computing a different matrix in place of the Jacobian.  One common
3241:   example is to use the "Picard linearization" which only differentiates through the highest order parts of each term using `SNESSetPicard()`

3243: .seealso: [](ch_snes), `SNES`, `KSPSetOperators()`, `SNESSetFunction()`, `MatMFFDComputeJacobian()`, `SNESComputeJacobianDefaultColor()`, `MatStructure`,
3244:           `SNESSetPicard()`, `SNESJacobianFn`, `SNESFunctionFn`
3245: @*/
3246: PetscErrorCode SNESSetJacobian(SNES snes, Mat Amat, Mat Pmat, SNESJacobianFn *J, void *ctx)
3247: {
3248:   DM dm;

3250:   PetscFunctionBegin;
3254:   if (Amat) PetscCheckSameComm(snes, 1, Amat, 2);
3255:   if (Pmat) PetscCheckSameComm(snes, 1, Pmat, 3);
3256:   PetscCall(SNESGetDM(snes, &dm));
3257:   PetscCall(DMSNESSetJacobian(dm, J, ctx));
3258:   if (Amat) {
3259:     PetscCall(PetscObjectReference((PetscObject)Amat));
3260:     PetscCall(MatDestroy(&snes->jacobian));

3262:     snes->jacobian = Amat;
3263:   }
3264:   if (Pmat) {
3265:     PetscCall(PetscObjectReference((PetscObject)Pmat));
3266:     PetscCall(MatDestroy(&snes->jacobian_pre));

3268:     snes->jacobian_pre = Pmat;
3269:   }
3270:   PetscFunctionReturn(PETSC_SUCCESS);
3271: }

3273: /*@C
3274:   SNESGetJacobian - Returns the Jacobian matrix and optionally the user
3275:   provided context for evaluating the Jacobian.

3277:   Not Collective, but `Mat` object will be parallel if `SNES` is

3279:   Input Parameter:
3280: . snes - the nonlinear solver context

3282:   Output Parameters:
3283: + Amat - location to stash (approximate) Jacobian matrix (or `NULL`)
3284: . Pmat - location to stash matrix used to compute the preconditioner (or `NULL`)
3285: . J    - location to put Jacobian function (or `NULL`), for calling sequence see `SNESJacobianFn`
3286: - ctx  - location to stash Jacobian ctx (or `NULL`)

3288:   Level: advanced

3290: .seealso: [](ch_snes), `SNES`, `Mat`, `SNESSetJacobian()`, `SNESComputeJacobian()`, `SNESJacobianFn`, `SNESGetFunction()`
3291: @*/
3292: PetscErrorCode SNESGetJacobian(SNES snes, Mat *Amat, Mat *Pmat, SNESJacobianFn **J, void **ctx)
3293: {
3294:   DM dm;

3296:   PetscFunctionBegin;
3298:   if (Amat) *Amat = snes->jacobian;
3299:   if (Pmat) *Pmat = snes->jacobian_pre;
3300:   PetscCall(SNESGetDM(snes, &dm));
3301:   PetscCall(DMSNESGetJacobian(dm, J, ctx));
3302:   PetscFunctionReturn(PETSC_SUCCESS);
3303: }

3305: static PetscErrorCode SNESSetDefaultComputeJacobian(SNES snes)
3306: {
3307:   DM     dm;
3308:   DMSNES sdm;

3310:   PetscFunctionBegin;
3311:   PetscCall(SNESGetDM(snes, &dm));
3312:   PetscCall(DMGetDMSNES(dm, &sdm));
3313:   if (!sdm->ops->computejacobian && snes->jacobian_pre) {
3314:     DM        dm;
3315:     PetscBool isdense, ismf;

3317:     PetscCall(SNESGetDM(snes, &dm));
3318:     PetscCall(PetscObjectTypeCompareAny((PetscObject)snes->jacobian_pre, &isdense, MATSEQDENSE, MATMPIDENSE, MATDENSE, NULL));
3319:     PetscCall(PetscObjectTypeCompareAny((PetscObject)snes->jacobian_pre, &ismf, MATMFFD, MATSHELL, NULL));
3320:     if (isdense) {
3321:       PetscCall(DMSNESSetJacobian(dm, SNESComputeJacobianDefault, NULL));
3322:     } else if (!ismf) {
3323:       PetscCall(DMSNESSetJacobian(dm, SNESComputeJacobianDefaultColor, NULL));
3324:     }
3325:   }
3326:   PetscFunctionReturn(PETSC_SUCCESS);
3327: }

3329: /*@
3330:   SNESSetUp - Sets up the internal data structures for the later use
3331:   of a nonlinear solver `SNESSolve()`.

3333:   Collective

3335:   Input Parameter:
3336: . snes - the `SNES` context

3338:   Level: advanced

3340:   Note:
3341:   For basic use of the `SNES` solvers the user does not need to explicitly call
3342:   `SNESSetUp()`, since these actions will automatically occur during
3343:   the call to `SNESSolve()`.  However, if one wishes to control this
3344:   phase separately, `SNESSetUp()` should be called after `SNESCreate()`
3345:   and optional routines of the form SNESSetXXX(), but before `SNESSolve()`.

3347: .seealso: [](ch_snes), `SNES`, `SNESCreate()`, `SNESSolve()`, `SNESDestroy()`, `SNESSetFromOptions()`
3348: @*/
3349: PetscErrorCode SNESSetUp(SNES snes)
3350: {
3351:   DM             dm;
3352:   DMSNES         sdm;
3353:   SNESLineSearch linesearch, pclinesearch;
3354:   void          *lsprectx, *lspostctx;
3355:   PetscBool      mf_operator, mf;
3356:   Vec            f, fpc;
3357:   void          *funcctx;
3358:   void          *jacctx, *appctx;
3359:   Mat            j, jpre;
3360:   PetscErrorCode (*precheck)(SNESLineSearch, Vec, Vec, PetscBool *, void *);
3361:   PetscErrorCode (*postcheck)(SNESLineSearch, Vec, Vec, Vec, PetscBool *, PetscBool *, void *);
3362:   SNESFunctionFn *func;
3363:   SNESJacobianFn *jac;

3365:   PetscFunctionBegin;
3367:   if (snes->setupcalled) PetscFunctionReturn(PETSC_SUCCESS);
3368:   PetscCall(PetscLogEventBegin(SNES_SetUp, snes, 0, 0, 0));

3370:   if (!((PetscObject)snes)->type_name) PetscCall(SNESSetType(snes, SNESNEWTONLS));

3372:   PetscCall(SNESGetFunction(snes, &snes->vec_func, NULL, NULL));

3374:   PetscCall(SNESGetDM(snes, &dm));
3375:   PetscCall(DMGetDMSNES(dm, &sdm));
3376:   PetscCall(SNESSetDefaultComputeJacobian(snes));

3378:   if (!snes->vec_func) PetscCall(DMCreateGlobalVector(dm, &snes->vec_func));

3380:   if (!snes->ksp) PetscCall(SNESGetKSP(snes, &snes->ksp));

3382:   if (snes->linesearch) {
3383:     PetscCall(SNESGetLineSearch(snes, &snes->linesearch));
3384:     PetscCall(SNESLineSearchSetFunction(snes->linesearch, SNESComputeFunction));
3385:   }

3387:   PetscCall(SNESGetUseMatrixFree(snes, &mf_operator, &mf));
3388:   if (snes->npc && snes->npcside == PC_LEFT) {
3389:     snes->mf          = PETSC_TRUE;
3390:     snes->mf_operator = PETSC_FALSE;
3391:   }

3393:   if (snes->npc) {
3394:     /* copy the DM over */
3395:     PetscCall(SNESGetDM(snes, &dm));
3396:     PetscCall(SNESSetDM(snes->npc, dm));

3398:     PetscCall(SNESGetFunction(snes, &f, &func, &funcctx));
3399:     PetscCall(VecDuplicate(f, &fpc));
3400:     PetscCall(SNESSetFunction(snes->npc, fpc, func, funcctx));
3401:     PetscCall(SNESGetJacobian(snes, &j, &jpre, &jac, &jacctx));
3402:     PetscCall(SNESSetJacobian(snes->npc, j, jpre, jac, jacctx));
3403:     PetscCall(SNESGetApplicationContext(snes, &appctx));
3404:     PetscCall(SNESSetApplicationContext(snes->npc, appctx));
3405:     PetscCall(SNESSetUseMatrixFree(snes->npc, mf_operator, mf));
3406:     PetscCall(VecDestroy(&fpc));

3408:     /* copy the function pointers over */
3409:     PetscCall(PetscObjectCopyFortranFunctionPointers((PetscObject)snes, (PetscObject)snes->npc));

3411:     /* default to 1 iteration */
3412:     PetscCall(SNESSetTolerances(snes->npc, 0.0, 0.0, 0.0, 1, snes->npc->max_funcs));
3413:     if (snes->npcside == PC_RIGHT) {
3414:       PetscCall(SNESSetNormSchedule(snes->npc, SNES_NORM_FINAL_ONLY));
3415:     } else {
3416:       PetscCall(SNESSetNormSchedule(snes->npc, SNES_NORM_NONE));
3417:     }
3418:     PetscCall(SNESSetFromOptions(snes->npc));

3420:     /* copy the line search context over */
3421:     if (snes->linesearch && snes->npc->linesearch) {
3422:       PetscCall(SNESGetLineSearch(snes, &linesearch));
3423:       PetscCall(SNESGetLineSearch(snes->npc, &pclinesearch));
3424:       PetscCall(SNESLineSearchGetPreCheck(linesearch, &precheck, &lsprectx));
3425:       PetscCall(SNESLineSearchGetPostCheck(linesearch, &postcheck, &lspostctx));
3426:       PetscCall(SNESLineSearchSetPreCheck(pclinesearch, precheck, lsprectx));
3427:       PetscCall(SNESLineSearchSetPostCheck(pclinesearch, postcheck, lspostctx));
3428:       PetscCall(PetscObjectCopyFortranFunctionPointers((PetscObject)linesearch, (PetscObject)pclinesearch));
3429:     }
3430:   }
3431:   if (snes->mf) PetscCall(SNESSetUpMatrixFree_Private(snes, snes->mf_operator, snes->mf_version));
3432:   if (snes->ops->usercompute && !snes->ctx) PetscCallBack("SNES callback compute application context", (*snes->ops->usercompute)(snes, &snes->ctx));

3434:   snes->jac_iter = 0;
3435:   snes->pre_iter = 0;

3437:   PetscTryTypeMethod(snes, setup);

3439:   PetscCall(SNESSetDefaultComputeJacobian(snes));

3441:   if (snes->npc && snes->npcside == PC_LEFT) {
3442:     if (snes->functype == SNES_FUNCTION_PRECONDITIONED) {
3443:       if (snes->linesearch) {
3444:         PetscCall(SNESGetLineSearch(snes, &linesearch));
3445:         PetscCall(SNESLineSearchSetFunction(linesearch, SNESComputeFunctionDefaultNPC));
3446:       }
3447:     }
3448:   }
3449:   PetscCall(PetscLogEventEnd(SNES_SetUp, snes, 0, 0, 0));
3450:   snes->setupcalled = PETSC_TRUE;
3451:   PetscFunctionReturn(PETSC_SUCCESS);
3452: }

3454: /*@
3455:   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

3457:   Collective

3459:   Input Parameter:
3460: . snes - the nonlinear iterative solver context obtained from `SNESCreate()`

3462:   Level: intermediate

3464:   Notes:
3465:   Any options set on the `SNES` object, including those set with `SNESSetFromOptions()` remain.

3467:   Call this if you wish to reuse a `SNES` but with different size vectors

3469:   Also calls the application context destroy routine set with `SNESSetComputeApplicationContext()`

3471: .seealso: [](ch_snes), `SNES`, `SNESDestroy()`, `SNESCreate()`, `SNESSetUp()`, `SNESSolve()`
3472: @*/
3473: PetscErrorCode SNESReset(SNES snes)
3474: {
3475:   PetscFunctionBegin;
3477:   if (snes->ops->ctxdestroy && snes->ctx) {
3478:     PetscCallBack("SNES callback destroy application context", (*snes->ops->ctxdestroy)(&snes->ctx));
3479:     snes->ctx = NULL;
3480:   }
3481:   if (snes->npc) PetscCall(SNESReset(snes->npc));

3483:   PetscTryTypeMethod(snes, reset);
3484:   if (snes->ksp) PetscCall(KSPReset(snes->ksp));

3486:   if (snes->linesearch) PetscCall(SNESLineSearchReset(snes->linesearch));

3488:   PetscCall(VecDestroy(&snes->vec_rhs));
3489:   PetscCall(VecDestroy(&snes->vec_sol));
3490:   PetscCall(VecDestroy(&snes->vec_sol_update));
3491:   PetscCall(VecDestroy(&snes->vec_func));
3492:   PetscCall(MatDestroy(&snes->jacobian));
3493:   PetscCall(MatDestroy(&snes->jacobian_pre));
3494:   PetscCall(MatDestroy(&snes->picard));
3495:   PetscCall(VecDestroyVecs(snes->nwork, &snes->work));
3496:   PetscCall(VecDestroyVecs(snes->nvwork, &snes->vwork));

3498:   snes->alwayscomputesfinalresidual = PETSC_FALSE;

3500:   snes->nwork = snes->nvwork = 0;
3501:   snes->setupcalled          = PETSC_FALSE;
3502:   PetscFunctionReturn(PETSC_SUCCESS);
3503: }

3505: /*@
3506:   SNESConvergedReasonViewCancel - Clears all the reason view functions for a `SNES` object provided with `SNESConvergedReasonViewSet()` also
3507:   removes the default viewer.

3509:   Collective

3511:   Input Parameter:
3512: . snes - the nonlinear iterative solver context obtained from `SNESCreate()`

3514:   Level: intermediate

3516: .seealso: [](ch_snes), `SNES`, `SNESCreate()`, `SNESDestroy()`, `SNESReset()`, `SNESConvergedReasonViewSet()`
3517: @*/
3518: PetscErrorCode SNESConvergedReasonViewCancel(SNES snes)
3519: {
3520:   PetscInt i;

3522:   PetscFunctionBegin;
3524:   for (i = 0; i < snes->numberreasonviews; i++) {
3525:     if (snes->reasonviewdestroy[i]) PetscCall((*snes->reasonviewdestroy[i])(&snes->reasonviewcontext[i]));
3526:   }
3527:   snes->numberreasonviews = 0;
3528:   PetscCall(PetscViewerDestroy(&snes->convergedreasonviewer));
3529:   PetscFunctionReturn(PETSC_SUCCESS);
3530: }

3532: /*@
3533:   SNESDestroy - Destroys the nonlinear solver context that was created
3534:   with `SNESCreate()`.

3536:   Collective

3538:   Input Parameter:
3539: . snes - the `SNES` context

3541:   Level: beginner

3543: .seealso: [](ch_snes), `SNES`, `SNESCreate()`, `SNESSolve()`
3544: @*/
3545: PetscErrorCode SNESDestroy(SNES *snes)
3546: {
3547:   DM dm;

3549:   PetscFunctionBegin;
3550:   if (!*snes) PetscFunctionReturn(PETSC_SUCCESS);
3552:   if (--((PetscObject)*snes)->refct > 0) {
3553:     *snes = NULL;
3554:     PetscFunctionReturn(PETSC_SUCCESS);
3555:   }

3557:   PetscCall(SNESReset(*snes));
3558:   PetscCall(SNESDestroy(&(*snes)->npc));

3560:   /* if memory was published with SAWs then destroy it */
3561:   PetscCall(PetscObjectSAWsViewOff((PetscObject)*snes));
3562:   PetscTryTypeMethod(*snes, destroy);

3564:   dm = (*snes)->dm;
3565:   while (dm) {
3566:     PetscCall(DMCoarsenHookRemove(dm, DMCoarsenHook_SNESVecSol, DMRestrictHook_SNESVecSol, *snes));
3567:     PetscCall(DMGetCoarseDM(dm, &dm));
3568:   }

3570:   PetscCall(DMDestroy(&(*snes)->dm));
3571:   PetscCall(KSPDestroy(&(*snes)->ksp));
3572:   PetscCall(SNESLineSearchDestroy(&(*snes)->linesearch));

3574:   PetscCall(PetscFree((*snes)->kspconvctx));
3575:   if ((*snes)->ops->convergeddestroy) PetscCall((*(*snes)->ops->convergeddestroy)((*snes)->cnvP));
3576:   if ((*snes)->conv_hist_alloc) PetscCall(PetscFree2((*snes)->conv_hist, (*snes)->conv_hist_its));
3577:   PetscCall(SNESMonitorCancel(*snes));
3578:   PetscCall(SNESConvergedReasonViewCancel(*snes));
3579:   PetscCall(PetscHeaderDestroy(snes));
3580:   PetscFunctionReturn(PETSC_SUCCESS);
3581: }

3583: /* ----------- Routines to set solver parameters ---------- */

3585: /*@
3586:   SNESSetLagPreconditioner - Sets when the preconditioner is rebuilt in the nonlinear solve `SNESSolve()`.

3588:   Logically Collective

3590:   Input Parameters:
3591: + snes - the `SNES` context
3592: - lag  - 1 means rebuild every time the Jacobian is computed within a single nonlinear solve, 2 means every second time
3593:          the Jacobian is built etc. -2 indicates rebuild preconditioner at next chance but then never rebuild after that

3595:   Options Database Keys:
3596: + -snes_lag_jacobian_persists <true,false>       - sets the persistence through multiple `SNESSolve()`
3597: . -snes_lag_jacobian <-2,1,2,...>                - sets the lag
3598: . -snes_lag_preconditioner_persists <true,false> - sets the persistence through multiple `SNESSolve()`
3599: - -snes_lag_preconditioner <-2,1,2,...>          - sets the lag

3601:   Level: intermediate

3603:   Notes:
3604:   The default is 1

3606:   The preconditioner is ALWAYS built in the first iteration of a nonlinear solve unless lag is -1 or `SNESSetLagPreconditionerPersists()` was called

3608:   `SNESSetLagPreconditionerPersists()` allows using the same uniform lagging (for example every second linear solve) across multiple nonlinear solves.

3610: .seealso: [](ch_snes), `SNESGetLagPreconditioner()`, `SNESSetLagJacobian()`, `SNESGetLagJacobian()`, `SNESSetLagPreconditionerPersists()`,
3611:           `SNESSetLagJacobianPersists()`, `SNES`, `SNESSolve()`
3612: @*/
3613: PetscErrorCode SNESSetLagPreconditioner(SNES snes, PetscInt lag)
3614: {
3615:   PetscFunctionBegin;
3617:   PetscCheck(lag >= -2, PETSC_COMM_SELF, PETSC_ERR_ARG_OUTOFRANGE, "Lag must be -2, -1, 1 or greater");
3618:   PetscCheck(lag, PETSC_COMM_SELF, PETSC_ERR_ARG_OUTOFRANGE, "Lag cannot be 0");
3620:   snes->lagpreconditioner = lag;
3621:   PetscFunctionReturn(PETSC_SUCCESS);
3622: }

3624: /*@
3625:   SNESSetGridSequence - sets the number of steps of grid sequencing that `SNES` will do

3627:   Logically Collective

3629:   Input Parameters:
3630: + snes  - the `SNES` context
3631: - steps - the number of refinements to do, defaults to 0

3633:   Options Database Key:
3634: . -snes_grid_sequence <steps> - Use grid sequencing to generate initial guess

3636:   Level: intermediate

3638:   Notes:
3639:   Once grid sequencing is turned on `SNESSolve()` will automatically perform the solve on each grid refinement.

3641:   Use `SNESGetSolution()` to extract the fine grid solution after grid sequencing.

3643: .seealso: [](ch_snes), `SNES`, `SNESGetLagPreconditioner()`, `SNESSetLagJacobian()`, `SNESGetLagJacobian()`, `SNESGetGridSequence()`,
3644:           `SNESSetDM()`, `SNESSolve()`
3645: @*/
3646: PetscErrorCode SNESSetGridSequence(SNES snes, PetscInt steps)
3647: {
3648:   PetscFunctionBegin;
3651:   snes->gridsequence = steps;
3652:   PetscFunctionReturn(PETSC_SUCCESS);
3653: }

3655: /*@
3656:   SNESGetGridSequence - gets the number of steps of grid sequencing that `SNES` will do

3658:   Logically Collective

3660:   Input Parameter:
3661: . snes - the `SNES` context

3663:   Output Parameter:
3664: . steps - the number of refinements to do, defaults to 0

3666:   Level: intermediate

3668: .seealso: [](ch_snes), `SNESGetLagPreconditioner()`, `SNESSetLagJacobian()`, `SNESGetLagJacobian()`, `SNESSetGridSequence()`
3669: @*/
3670: PetscErrorCode SNESGetGridSequence(SNES snes, PetscInt *steps)
3671: {
3672:   PetscFunctionBegin;
3674:   *steps = snes->gridsequence;
3675:   PetscFunctionReturn(PETSC_SUCCESS);
3676: }

3678: /*@
3679:   SNESGetLagPreconditioner - Return how often the preconditioner is rebuilt

3681:   Not Collective

3683:   Input Parameter:
3684: . snes - the `SNES` context

3686:   Output Parameter:
3687: . lag - -1 indicates NEVER rebuild, 1 means rebuild every time the Jacobian is computed within a single nonlinear solve, 2 means every second time
3688:          the Jacobian is built etc. -2 indicates rebuild preconditioner at next chance but then never rebuild after that

3690:   Level: intermediate

3692:   Notes:
3693:   The default is 1

3695:   The preconditioner is ALWAYS built in the first iteration of a nonlinear solve unless lag is -1

3697: .seealso: [](ch_snes), `SNES`, `SNESSetLagPreconditioner()`, `SNESSetLagJacobianPersists()`, `SNESSetLagPreconditionerPersists()`
3698: @*/
3699: PetscErrorCode SNESGetLagPreconditioner(SNES snes, PetscInt *lag)
3700: {
3701:   PetscFunctionBegin;
3703:   *lag = snes->lagpreconditioner;
3704:   PetscFunctionReturn(PETSC_SUCCESS);
3705: }

3707: /*@
3708:   SNESSetLagJacobian - Set when the Jacobian is rebuilt in the nonlinear solve. See `SNESSetLagPreconditioner()` for determining how
3709:   often the preconditioner is rebuilt.

3711:   Logically Collective

3713:   Input Parameters:
3714: + snes - the `SNES` context
3715: - lag  - -1 indicates NEVER rebuild, 1 means rebuild every time the Jacobian is computed within a single nonlinear solve, 2 means every second time
3716:          the Jacobian is built etc. -2 means rebuild at next chance but then never again

3718:   Options Database Keys:
3719: + -snes_lag_jacobian_persists <true,false>       - sets the persistence through multiple SNES solves
3720: . -snes_lag_jacobian <-2,1,2,...>                - sets the lag
3721: . -snes_lag_preconditioner_persists <true,false> - sets the persistence through multiple SNES solves
3722: - -snes_lag_preconditioner <-2,1,2,...>          - sets the lag.

3724:   Level: intermediate

3726:   Notes:
3727:   The default is 1

3729:   The Jacobian is ALWAYS built in the first iteration of a nonlinear solve unless lag is -1

3731:   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
3732:   at the next Newton step but never again (unless it is reset to another value)

3734: .seealso: [](ch_snes), `SNES`, `SNESGetLagPreconditioner()`, `SNESSetLagPreconditioner()`, `SNESGetLagJacobianPersists()`, `SNESSetLagPreconditionerPersists()`
3735: @*/
3736: PetscErrorCode SNESSetLagJacobian(SNES snes, PetscInt lag)
3737: {
3738:   PetscFunctionBegin;
3740:   PetscCheck(lag >= -2, PETSC_COMM_SELF, PETSC_ERR_ARG_OUTOFRANGE, "Lag must be -2, -1, 1 or greater");
3741:   PetscCheck(lag, PETSC_COMM_SELF, PETSC_ERR_ARG_OUTOFRANGE, "Lag cannot be 0");
3743:   snes->lagjacobian = lag;
3744:   PetscFunctionReturn(PETSC_SUCCESS);
3745: }

3747: /*@
3748:   SNESGetLagJacobian - Get how often the Jacobian is rebuilt. See `SNESGetLagPreconditioner()` to determine when the preconditioner is rebuilt

3750:   Not Collective

3752:   Input Parameter:
3753: . snes - the `SNES` context

3755:   Output Parameter:
3756: . lag - -1 indicates NEVER rebuild, 1 means rebuild every time the Jacobian is computed within a single nonlinear solve, 2 means every second time
3757:          the Jacobian is built etc.

3759:   Level: intermediate

3761:   Notes:
3762:   The default is 1

3764:   The jacobian is ALWAYS built in the first iteration of a nonlinear solve unless lag is -1 or `SNESSetLagJacobianPersists()` was called.

3766: .seealso: [](ch_snes), `SNES`, `SNESSetLagJacobian()`, `SNESSetLagPreconditioner()`, `SNESGetLagPreconditioner()`, `SNESSetLagJacobianPersists()`, `SNESSetLagPreconditionerPersists()`

3768: @*/
3769: PetscErrorCode SNESGetLagJacobian(SNES snes, PetscInt *lag)
3770: {
3771:   PetscFunctionBegin;
3773:   *lag = snes->lagjacobian;
3774:   PetscFunctionReturn(PETSC_SUCCESS);
3775: }

3777: /*@
3778:   SNESSetLagJacobianPersists - Set whether or not the Jacobian lagging persists through multiple nonlinear solves

3780:   Logically collective

3782:   Input Parameters:
3783: + snes - the `SNES` context
3784: - flg  - jacobian lagging persists if true

3786:   Options Database Keys:
3787: + -snes_lag_jacobian_persists <true,false>       - sets the persistence through multiple SNES solves
3788: . -snes_lag_jacobian <-2,1,2,...>                - sets the lag
3789: . -snes_lag_preconditioner_persists <true,false> - sets the persistence through multiple SNES solves
3790: - -snes_lag_preconditioner <-2,1,2,...>          - sets the lag

3792:   Level: advanced

3794:   Notes:
3795:   Normally when `SNESSetLagJacobian()` is used, the Jacobian is always rebuilt at the beginning of each new nonlinear solve, this removes that behavior

3797:   This is useful both for nonlinear preconditioning, where it's appropriate to have the Jacobian be stale by
3798:   several solves, and for implicit time-stepping, where Jacobian lagging in the inner nonlinear solve over several
3799:   timesteps may present huge efficiency gains.

3801: .seealso: [](ch_snes), `SNES`, `SNESSetLagPreconditionerPersists()`, `SNESSetLagJacobian()`, `SNESGetLagJacobian()`, `SNESGetNPC()`
3802: @*/
3803: PetscErrorCode SNESSetLagJacobianPersists(SNES snes, PetscBool flg)
3804: {
3805:   PetscFunctionBegin;
3808:   snes->lagjac_persist = flg;
3809:   PetscFunctionReturn(PETSC_SUCCESS);
3810: }

3812: /*@
3813:   SNESSetLagPreconditionerPersists - Set whether or not the preconditioner lagging persists through multiple nonlinear solves

3815:   Logically Collective

3817:   Input Parameters:
3818: + snes - the `SNES` context
3819: - flg  - preconditioner lagging persists if true

3821:   Options Database Keys:
3822: + -snes_lag_jacobian_persists <true,false>       - sets the persistence through multiple SNES solves
3823: . -snes_lag_jacobian <-2,1,2,...>                - sets the lag
3824: . -snes_lag_preconditioner_persists <true,false> - sets the persistence through multiple SNES solves
3825: - -snes_lag_preconditioner <-2,1,2,...>          - sets the lag

3827:   Level: developer

3829:   Notes:
3830:   Normally when `SNESSetLagPreconditioner()` is used, the preconditioner is always rebuilt at the beginning of each new nonlinear solve, this removes that behavior

3832:   This is useful both for nonlinear preconditioning, where it's appropriate to have the preconditioner be stale
3833:   by several solves, and for implicit time-stepping, where preconditioner lagging in the inner nonlinear solve over
3834:   several timesteps may present huge efficiency gains.

3836: .seealso: [](ch_snes), `SNES`, `SNESSetLagJacobianPersists()`, `SNESSetLagJacobian()`, `SNESGetLagJacobian()`, `SNESGetNPC()`, `SNESSetLagPreconditioner()`
3837: @*/
3838: PetscErrorCode SNESSetLagPreconditionerPersists(SNES snes, PetscBool flg)
3839: {
3840:   PetscFunctionBegin;
3843:   snes->lagpre_persist = flg;
3844:   PetscFunctionReturn(PETSC_SUCCESS);
3845: }

3847: /*@
3848:   SNESSetForceIteration - force `SNESSolve()` to take at least one iteration regardless of the initial residual norm

3850:   Logically Collective

3852:   Input Parameters:
3853: + snes  - the `SNES` context
3854: - force - `PETSC_TRUE` require at least one iteration

3856:   Options Database Key:
3857: . -snes_force_iteration <force> - Sets forcing an iteration

3859:   Level: intermediate

3861:   Note:
3862:   This is used sometimes with `TS` to prevent `TS` from detecting a false steady state solution

3864: .seealso: [](ch_snes), `SNES`, `TS`, `SNESSetDivergenceTolerance()`
3865: @*/
3866: PetscErrorCode SNESSetForceIteration(SNES snes, PetscBool force)
3867: {
3868:   PetscFunctionBegin;
3870:   snes->forceiteration = force;
3871:   PetscFunctionReturn(PETSC_SUCCESS);
3872: }

3874: /*@
3875:   SNESGetForceIteration - Check whether or not `SNESSolve()` take at least one iteration regardless of the initial residual norm

3877:   Logically Collective

3879:   Input Parameter:
3880: . snes - the `SNES` context

3882:   Output Parameter:
3883: . force - `PETSC_TRUE` requires at least one iteration.

3885:   Level: intermediate

3887: .seealso: [](ch_snes), `SNES`, `SNESSetForceIteration()`, `SNESSetDivergenceTolerance()`
3888: @*/
3889: PetscErrorCode SNESGetForceIteration(SNES snes, PetscBool *force)
3890: {
3891:   PetscFunctionBegin;
3893:   *force = snes->forceiteration;
3894:   PetscFunctionReturn(PETSC_SUCCESS);
3895: }

3897: /*@
3898:   SNESSetTolerances - Sets various parameters used in `SNES` convergence tests.

3900:   Logically Collective

3902:   Input Parameters:
3903: + snes   - the `SNES` context
3904: . abstol - the absolute convergence tolerance, $ F(x^n) \le abstol $
3905: . rtol   - the relative convergence tolerance, $ F(x^n) \le reltol * F(x^0) $
3906: . stol   - convergence tolerance in terms of the norm of the change in the solution between steps,  || delta x || < stol*|| x ||
3907: . maxit  - the maximum number of iterations allowed in the solver, default 50.
3908: - maxf   - the maximum number of function evaluations allowed in the solver (use `PETSC_UNLIMITED` indicates no limit), default 10,000

3910:   Options Database Keys:
3911: + -snes_atol <abstol>    - Sets `abstol`
3912: . -snes_rtol <rtol>      - Sets `rtol`
3913: . -snes_stol <stol>      - Sets `stol`
3914: . -snes_max_it <maxit>   - Sets `maxit`
3915: - -snes_max_funcs <maxf> - Sets `maxf` (use `unlimited` to have no maximum)

3917:   Level: intermediate

3919:   Note:
3920:   All parameters must be non-negative

3922:   Use `PETSC_CURRENT` to retain the current value of any parameter and `PETSC_DETERMINE` to use the default value for the given `SNES`.
3923:   The default value is the value in the object when its type is set.

3925:   Use `PETSC_UNLIMITED` on `maxit` or `maxf` to indicate there is no bound on the number of iterations or number of function evaluations.

3927:   Fortran Note:
3928:   Use `PETSC_CURRENT_INTEGER`, `PETSC_CURRENT_REAL`, `PETSC_UNLIMITED_INTEGER`, `PETSC_DETERMINE_INTEGER`, or `PETSC_DETERMINE_REAL`

3930: .seealso: [](ch_snes), `SNESSolve()`, `SNES`, `SNESSetDivergenceTolerance()`, `SNESSetForceIteration()`
3931: @*/
3932: PetscErrorCode SNESSetTolerances(SNES snes, PetscReal abstol, PetscReal rtol, PetscReal stol, PetscInt maxit, PetscInt maxf)
3933: {
3934:   PetscFunctionBegin;

3942:   if (abstol == (PetscReal)PETSC_DETERMINE) {
3943:     snes->abstol = snes->default_abstol;
3944:   } else if (abstol != (PetscReal)PETSC_CURRENT) {
3945:     PetscCheck(abstol >= 0.0, PetscObjectComm((PetscObject)snes), PETSC_ERR_ARG_OUTOFRANGE, "Absolute tolerance %g must be non-negative", (double)abstol);
3946:     snes->abstol = abstol;
3947:   }

3949:   if (rtol == (PetscReal)PETSC_DETERMINE) {
3950:     snes->rtol = snes->default_rtol;
3951:   } else if (rtol != (PetscReal)PETSC_CURRENT) {
3952:     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);
3953:     snes->rtol = rtol;
3954:   }

3956:   if (stol == (PetscReal)PETSC_DETERMINE) {
3957:     snes->stol = snes->default_stol;
3958:   } else if (stol != (PetscReal)PETSC_CURRENT) {
3959:     PetscCheck(stol >= 0.0, PetscObjectComm((PetscObject)snes), PETSC_ERR_ARG_OUTOFRANGE, "Step tolerance %g must be non-negative", (double)stol);
3960:     snes->stol = stol;
3961:   }

3963:   if (maxit == PETSC_DETERMINE) {
3964:     snes->max_its = snes->default_max_its;
3965:   } else if (maxit == PETSC_UNLIMITED) {
3966:     snes->max_its = PETSC_INT_MAX;
3967:   } else if (maxit != PETSC_CURRENT) {
3968:     PetscCheck(maxit >= 0, PetscObjectComm((PetscObject)snes), PETSC_ERR_ARG_OUTOFRANGE, "Maximum number of iterations %" PetscInt_FMT " must be non-negative", maxit);
3969:     snes->max_its = maxit;
3970:   }

3972:   if (maxf == PETSC_DETERMINE) {
3973:     snes->max_funcs = snes->default_max_funcs;
3974:   } else if (maxf == PETSC_UNLIMITED || maxf == -1) {
3975:     snes->max_funcs = PETSC_UNLIMITED;
3976:   } else if (maxf != PETSC_CURRENT) {
3977:     PetscCheck(maxf >= 0, PetscObjectComm((PetscObject)snes), PETSC_ERR_ARG_OUTOFRANGE, "Maximum number of function evaluations %" PetscInt_FMT " must be nonnegative", maxf);
3978:     snes->max_funcs = maxf;
3979:   }
3980:   PetscFunctionReturn(PETSC_SUCCESS);
3981: }

3983: /*@
3984:   SNESSetDivergenceTolerance - Sets the divergence tolerance used for the `SNES` divergence test.

3986:   Logically Collective

3988:   Input Parameters:
3989: + snes   - the `SNES` context
3990: - 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
3991:            is stopped due to divergence.

3993:   Options Database Key:
3994: . -snes_divergence_tolerance <divtol> - Sets `divtol`

3996:   Level: intermediate

3998:   Notes:
3999:   Use `PETSC_DETERMINE` to use the default value from when the object's type was set.

4001:   Fortran Note:
4002:   Use ``PETSC_DETERMINE_REAL` or `PETSC_UNLIMITED_REAL`

4004: .seealso: [](ch_snes), `SNES`, `SNESSolve()`, `SNESSetTolerances()`, `SNESGetDivergenceTolerance()`
4005: @*/
4006: PetscErrorCode SNESSetDivergenceTolerance(SNES snes, PetscReal divtol)
4007: {
4008:   PetscFunctionBegin;

4012:   if (divtol == (PetscReal)PETSC_DETERMINE) {
4013:     snes->divtol = snes->default_divtol;
4014:   } else if (divtol == (PetscReal)PETSC_UNLIMITED || divtol == -1) {
4015:     snes->divtol = PETSC_UNLIMITED;
4016:   } else if (divtol != (PetscReal)PETSC_CURRENT) {
4017:     PetscCheck(divtol >= 1.0, PetscObjectComm((PetscObject)snes), PETSC_ERR_ARG_OUTOFRANGE, "Divergence tolerance %g must be greater than 1.0", (double)divtol);
4018:     snes->divtol = divtol;
4019:   }
4020:   PetscFunctionReturn(PETSC_SUCCESS);
4021: }

4023: /*@
4024:   SNESGetTolerances - Gets various parameters used in `SNES` convergence tests.

4026:   Not Collective

4028:   Input Parameter:
4029: . snes - the `SNES` context

4031:   Output Parameters:
4032: + atol  - the absolute convergence tolerance
4033: . rtol  - the relative convergence tolerance
4034: . stol  - convergence tolerance in terms of the norm of the change in the solution between steps
4035: . maxit - the maximum number of iterations allowed
4036: - maxf  - the maximum number of function evaluations allowed, `PETSC_UNLIMITED` indicates no bound

4038:   Level: intermediate

4040:   Notes:
4041:   See `SNESSetTolerances()` for details on the parameters.

4043:   The user can specify `NULL` for any parameter that is not needed.

4045: .seealso: [](ch_snes), `SNES`, `SNESSetTolerances()`
4046: @*/
4047: PetscErrorCode SNESGetTolerances(SNES snes, PetscReal *atol, PetscReal *rtol, PetscReal *stol, PetscInt *maxit, PetscInt *maxf)
4048: {
4049:   PetscFunctionBegin;
4051:   if (atol) *atol = snes->abstol;
4052:   if (rtol) *rtol = snes->rtol;
4053:   if (stol) *stol = snes->stol;
4054:   if (maxit) *maxit = snes->max_its;
4055:   if (maxf) *maxf = snes->max_funcs;
4056:   PetscFunctionReturn(PETSC_SUCCESS);
4057: }

4059: /*@
4060:   SNESGetDivergenceTolerance - Gets divergence tolerance used in divergence test.

4062:   Not Collective

4064:   Input Parameters:
4065: + snes   - the `SNES` context
4066: - divtol - divergence tolerance

4068:   Level: intermediate

4070: .seealso: [](ch_snes), `SNES`, `SNESSetDivergenceTolerance()`
4071: @*/
4072: PetscErrorCode SNESGetDivergenceTolerance(SNES snes, PetscReal *divtol)
4073: {
4074:   PetscFunctionBegin;
4076:   if (divtol) *divtol = snes->divtol;
4077:   PetscFunctionReturn(PETSC_SUCCESS);
4078: }

4080: PETSC_INTERN PetscErrorCode SNESMonitorRange_Private(SNES, PetscInt, PetscReal *);

4082: PetscErrorCode SNESMonitorLGRange(SNES snes, PetscInt n, PetscReal rnorm, void *monctx)
4083: {
4084:   PetscDrawLG      lg;
4085:   PetscReal        x, y, per;
4086:   PetscViewer      v = (PetscViewer)monctx;
4087:   static PetscReal prev; /* should be in the context */
4088:   PetscDraw        draw;

4090:   PetscFunctionBegin;
4092:   PetscCall(PetscViewerDrawGetDrawLG(v, 0, &lg));
4093:   if (!n) PetscCall(PetscDrawLGReset(lg));
4094:   PetscCall(PetscDrawLGGetDraw(lg, &draw));
4095:   PetscCall(PetscDrawSetTitle(draw, "Residual norm"));
4096:   x = (PetscReal)n;
4097:   if (rnorm > 0.0) y = PetscLog10Real(rnorm);
4098:   else y = -15.0;
4099:   PetscCall(PetscDrawLGAddPoint(lg, &x, &y));
4100:   if (n < 20 || !(n % 5) || snes->reason) {
4101:     PetscCall(PetscDrawLGDraw(lg));
4102:     PetscCall(PetscDrawLGSave(lg));
4103:   }

4105:   PetscCall(PetscViewerDrawGetDrawLG(v, 1, &lg));
4106:   if (!n) PetscCall(PetscDrawLGReset(lg));
4107:   PetscCall(PetscDrawLGGetDraw(lg, &draw));
4108:   PetscCall(PetscDrawSetTitle(draw, "% elements > .2*max element"));
4109:   PetscCall(SNESMonitorRange_Private(snes, n, &per));
4110:   x = (PetscReal)n;
4111:   y = 100.0 * per;
4112:   PetscCall(PetscDrawLGAddPoint(lg, &x, &y));
4113:   if (n < 20 || !(n % 5) || snes->reason) {
4114:     PetscCall(PetscDrawLGDraw(lg));
4115:     PetscCall(PetscDrawLGSave(lg));
4116:   }

4118:   PetscCall(PetscViewerDrawGetDrawLG(v, 2, &lg));
4119:   if (!n) {
4120:     prev = rnorm;
4121:     PetscCall(PetscDrawLGReset(lg));
4122:   }
4123:   PetscCall(PetscDrawLGGetDraw(lg, &draw));
4124:   PetscCall(PetscDrawSetTitle(draw, "(norm -oldnorm)/oldnorm"));
4125:   x = (PetscReal)n;
4126:   y = (prev - rnorm) / prev;
4127:   PetscCall(PetscDrawLGAddPoint(lg, &x, &y));
4128:   if (n < 20 || !(n % 5) || snes->reason) {
4129:     PetscCall(PetscDrawLGDraw(lg));
4130:     PetscCall(PetscDrawLGSave(lg));
4131:   }

4133:   PetscCall(PetscViewerDrawGetDrawLG(v, 3, &lg));
4134:   if (!n) PetscCall(PetscDrawLGReset(lg));
4135:   PetscCall(PetscDrawLGGetDraw(lg, &draw));
4136:   PetscCall(PetscDrawSetTitle(draw, "(norm -oldnorm)/oldnorm*(% > .2 max)"));
4137:   x = (PetscReal)n;
4138:   y = (prev - rnorm) / (prev * per);
4139:   if (n > 2) { /*skip initial crazy value */
4140:     PetscCall(PetscDrawLGAddPoint(lg, &x, &y));
4141:   }
4142:   if (n < 20 || !(n % 5) || snes->reason) {
4143:     PetscCall(PetscDrawLGDraw(lg));
4144:     PetscCall(PetscDrawLGSave(lg));
4145:   }
4146:   prev = rnorm;
4147:   PetscFunctionReturn(PETSC_SUCCESS);
4148: }

4150: /*@
4151:   SNESConverged - Run the convergence test and update the `SNESConvergedReason`.

4153:   Collective

4155:   Input Parameters:
4156: + snes  - the `SNES` context
4157: . it    - current iteration
4158: . xnorm - 2-norm of current iterate
4159: . snorm - 2-norm of current step
4160: - fnorm - 2-norm of function

4162:   Level: developer

4164:   Note:
4165:   This routine is called by the `SNESSolve()` implementations.
4166:   It does not typically need to be called by the user.

4168: .seealso: [](ch_snes), `SNES`, `SNESSolve`, `SNESSetConvergenceTest()`
4169: @*/
4170: PetscErrorCode SNESConverged(SNES snes, PetscInt it, PetscReal xnorm, PetscReal snorm, PetscReal fnorm)
4171: {
4172:   PetscFunctionBegin;
4173:   if (!snes->reason) {
4174:     if (snes->normschedule == SNES_NORM_ALWAYS) PetscUseTypeMethod(snes, converged, it, xnorm, snorm, fnorm, &snes->reason, snes->cnvP);
4175:     if (it == snes->max_its && !snes->reason) {
4176:       if (snes->normschedule == SNES_NORM_ALWAYS) {
4177:         PetscCall(PetscInfo(snes, "Maximum number of iterations has been reached: %" PetscInt_FMT "\n", snes->max_its));
4178:         snes->reason = SNES_DIVERGED_MAX_IT;
4179:       } else snes->reason = SNES_CONVERGED_ITS;
4180:     }
4181:   }
4182:   PetscFunctionReturn(PETSC_SUCCESS);
4183: }

4185: /*@
4186:   SNESMonitor - runs any `SNES` monitor routines provided with `SNESMonitor()` or the options database

4188:   Collective

4190:   Input Parameters:
4191: + snes  - nonlinear solver context obtained from `SNESCreate()`
4192: . iter  - current iteration number
4193: - rnorm - current relative norm of the residual

4195:   Level: developer

4197:   Note:
4198:   This routine is called by the `SNESSolve()` implementations.
4199:   It does not typically need to be called by the user.

4201: .seealso: [](ch_snes), `SNES`, `SNESMonitorSet()`
4202: @*/
4203: PetscErrorCode SNESMonitor(SNES snes, PetscInt iter, PetscReal rnorm)
4204: {
4205:   PetscInt i, n = snes->numbermonitors;

4207:   PetscFunctionBegin;
4208:   PetscCall(VecLockReadPush(snes->vec_sol));
4209:   for (i = 0; i < n; i++) PetscCall((*snes->monitor[i])(snes, iter, rnorm, snes->monitorcontext[i]));
4210:   PetscCall(VecLockReadPop(snes->vec_sol));
4211:   PetscFunctionReturn(PETSC_SUCCESS);
4212: }

4214: /* ------------ Routines to set performance monitoring options ----------- */

4216: /*MC
4217:     SNESMonitorFunction - functional form passed to `SNESMonitorSet()` to monitor convergence of nonlinear solver

4219:      Synopsis:
4220: #include <petscsnes.h>
4221:     PetscErrorCode SNESMonitorFunction(SNES snes, PetscInt its, PetscReal norm, void *mctx)

4223:      Collective

4225:     Input Parameters:
4226: +    snes - the `SNES` context
4227: .    its - iteration number
4228: .    norm - 2-norm function value (may be estimated)
4229: -    mctx - [optional] monitoring context

4231:    Level: advanced

4233: .seealso: [](ch_snes), `SNESMonitorSet()`
4234: M*/

4236: /*@C
4237:   SNESMonitorSet - Sets an ADDITIONAL function that is to be used at every
4238:   iteration of the `SNES` nonlinear solver to display the iteration's
4239:   progress.

4241:   Logically Collective

4243:   Input Parameters:
4244: + snes           - the `SNES` context
4245: . f              - the monitor function,  for the calling sequence see `SNESMonitorFunction`
4246: . mctx           - [optional] user-defined context for private data for the monitor routine (use `NULL` if no context is desired)
4247: - monitordestroy - [optional] routine that frees monitor context (may be `NULL`), see `PetscCtxDestroyFn` for the calling sequence

4249:   Options Database Keys:
4250: + -snes_monitor               - sets `SNESMonitorDefault()`
4251: . -snes_monitor draw::draw_lg - sets line graph monitor,
4252: - -snes_monitor_cancel        - cancels all monitors that have been hardwired into a code by calls to `SNESMonitorSet()`, but does not cancel those set via
4253:                                 the options database.

4255:   Level: intermediate

4257:   Note:
4258:   Several different monitoring routines may be set by calling
4259:   `SNESMonitorSet()` multiple times; all will be called in the
4260:   order in which they were set.

4262:   Fortran Note:
4263:   Only a single monitor function can be set for each `SNES` object

4265: .seealso: [](ch_snes), `SNES`, `SNESSolve()`, `SNESMonitorDefault()`, `SNESMonitorCancel()`, `SNESMonitorFunction`, `PetscCtxDestroyFn`
4266: @*/
4267: PetscErrorCode SNESMonitorSet(SNES snes, PetscErrorCode (*f)(SNES, PetscInt, PetscReal, void *), void *mctx, PetscCtxDestroyFn *monitordestroy)
4268: {
4269:   PetscFunctionBegin;
4271:   for (PetscInt i = 0; i < snes->numbermonitors; i++) {
4272:     PetscBool identical;

4274:     PetscCall(PetscMonitorCompare((PetscErrorCode (*)(void))(PetscVoidFn *)f, mctx, monitordestroy, (PetscErrorCode (*)(void))(PetscVoidFn *)snes->monitor[i], snes->monitorcontext[i], snes->monitordestroy[i], &identical));
4275:     if (identical) PetscFunctionReturn(PETSC_SUCCESS);
4276:   }
4277:   PetscCheck(snes->numbermonitors < MAXSNESMONITORS, PETSC_COMM_SELF, PETSC_ERR_ARG_OUTOFRANGE, "Too many monitors set");
4278:   snes->monitor[snes->numbermonitors]          = f;
4279:   snes->monitordestroy[snes->numbermonitors]   = monitordestroy;
4280:   snes->monitorcontext[snes->numbermonitors++] = mctx;
4281:   PetscFunctionReturn(PETSC_SUCCESS);
4282: }

4284: /*@
4285:   SNESMonitorCancel - Clears all the monitor functions for a `SNES` object.

4287:   Logically Collective

4289:   Input Parameter:
4290: . snes - the `SNES` context

4292:   Options Database Key:
4293: . -snes_monitor_cancel - cancels all monitors that have been hardwired
4294:                          into a code by calls to `SNESMonitorSet()`, but does not cancel those
4295:                          set via the options database

4297:   Level: intermediate

4299:   Note:
4300:   There is no way to clear one specific monitor from a `SNES` object.

4302: .seealso: [](ch_snes), `SNES`, `SNESMonitorDefault()`, `SNESMonitorSet()`
4303: @*/
4304: PetscErrorCode SNESMonitorCancel(SNES snes)
4305: {
4306:   PetscInt i;

4308:   PetscFunctionBegin;
4310:   for (i = 0; i < snes->numbermonitors; i++) {
4311:     if (snes->monitordestroy[i]) PetscCall((*snes->monitordestroy[i])(&snes->monitorcontext[i]));
4312:   }
4313:   snes->numbermonitors = 0;
4314:   PetscFunctionReturn(PETSC_SUCCESS);
4315: }

4317: /*MC
4318:     SNESConvergenceTestFunction - functional form used for testing of convergence of nonlinear solver

4320:      Synopsis:
4321: #include <petscsnes.h>
4322:      PetscErrorCode SNESConvergenceTest(SNES snes, PetscInt it, PetscReal xnorm, PetscReal gnorm, PetscReal f, SNESConvergedReason *reason, void *cctx)

4324:      Collective

4326:     Input Parameters:
4327: +    snes - the `SNES` context
4328: .    it - current iteration (0 is the first and is before any Newton step)
4329: .    xnorm - 2-norm of current iterate
4330: .    gnorm - 2-norm of current step
4331: .    f - 2-norm of function
4332: -    cctx - [optional] convergence context

4334:     Output Parameter:
4335: .    reason - reason for convergence/divergence, only needs to be set when convergence or divergence is detected

4337:    Level: intermediate

4339: .seealso: [](ch_snes), `SNES`, `SNESSolve`, `SNESSetConvergenceTest()`
4340: M*/

4342: /*@C
4343:   SNESSetConvergenceTest - Sets the function that is to be used
4344:   to test for convergence of the nonlinear iterative solution.

4346:   Logically Collective

4348:   Input Parameters:
4349: + snes                        - the `SNES` context
4350: . SNESConvergenceTestFunction - routine to test for convergence
4351: . cctx                        - [optional] context for private data for the convergence routine  (may be `NULL`)
4352: - destroy                     - [optional] destructor for the context (may be `NULL`; `PETSC_NULL_FUNCTION` in Fortran)

4354:   Level: advanced

4356: .seealso: [](ch_snes), `SNES`, `SNESConvergedDefault()`, `SNESConvergedSkip()`, `SNESConvergenceTestFunction`
4357: @*/
4358: PetscErrorCode SNESSetConvergenceTest(SNES snes, PetscErrorCode (*SNESConvergenceTestFunction)(SNES, PetscInt, PetscReal, PetscReal, PetscReal, SNESConvergedReason *, void *), void *cctx, PetscErrorCode (*destroy)(void *))
4359: {
4360:   PetscFunctionBegin;
4362:   if (!SNESConvergenceTestFunction) SNESConvergenceTestFunction = SNESConvergedSkip;
4363:   if (snes->ops->convergeddestroy) PetscCall((*snes->ops->convergeddestroy)(snes->cnvP));
4364:   snes->ops->converged        = SNESConvergenceTestFunction;
4365:   snes->ops->convergeddestroy = destroy;
4366:   snes->cnvP                  = cctx;
4367:   PetscFunctionReturn(PETSC_SUCCESS);
4368: }

4370: /*@
4371:   SNESGetConvergedReason - Gets the reason the `SNES` iteration was stopped, which may be due to convergence, divergence, or stagnation

4373:   Not Collective

4375:   Input Parameter:
4376: . snes - the `SNES` context

4378:   Output Parameter:
4379: . reason - negative value indicates diverged, positive value converged, see `SNESConvergedReason` for the individual convergence tests for complete lists

4381:   Options Database Key:
4382: . -snes_converged_reason - prints the reason to standard out

4384:   Level: intermediate

4386:   Note:
4387:   Should only be called after the call the `SNESSolve()` is complete, if it is called earlier it returns the value `SNES__CONVERGED_ITERATING`.

4389: .seealso: [](ch_snes), `SNESSolve()`, `SNESSetConvergenceTest()`, `SNESSetConvergedReason()`, `SNESConvergedReason`, `SNESGetConvergedReasonString()`
4390: @*/
4391: PetscErrorCode SNESGetConvergedReason(SNES snes, SNESConvergedReason *reason)
4392: {
4393:   PetscFunctionBegin;
4395:   PetscAssertPointer(reason, 2);
4396:   *reason = snes->reason;
4397:   PetscFunctionReturn(PETSC_SUCCESS);
4398: }

4400: /*@C
4401:   SNESGetConvergedReasonString - Return a human readable string for `SNESConvergedReason`

4403:   Not Collective

4405:   Input Parameter:
4406: . snes - the `SNES` context

4408:   Output Parameter:
4409: . strreason - a human readable string that describes `SNES` converged reason

4411:   Level: beginner

4413: .seealso: [](ch_snes), `SNES`, `SNESGetConvergedReason()`
4414: @*/
4415: PetscErrorCode SNESGetConvergedReasonString(SNES snes, const char **strreason)
4416: {
4417:   PetscFunctionBegin;
4419:   PetscAssertPointer(strreason, 2);
4420:   *strreason = SNESConvergedReasons[snes->reason];
4421:   PetscFunctionReturn(PETSC_SUCCESS);
4422: }

4424: /*@
4425:   SNESSetConvergedReason - Sets the reason the `SNES` iteration was stopped.

4427:   Not Collective

4429:   Input Parameters:
4430: + snes   - the `SNES` context
4431: - reason - negative value indicates diverged, positive value converged, see `SNESConvergedReason` or the
4432:             manual pages for the individual convergence tests for complete lists

4434:   Level: developer

4436:   Developer Note:
4437:   Called inside the various `SNESSolve()` implementations

4439: .seealso: [](ch_snes), `SNESGetConvergedReason()`, `SNESSetConvergenceTest()`, `SNESConvergedReason`
4440: @*/
4441: PetscErrorCode SNESSetConvergedReason(SNES snes, SNESConvergedReason reason)
4442: {
4443:   PetscFunctionBegin;
4445:   PetscCheck(!snes->errorifnotconverged || reason > 0, PetscObjectComm((PetscObject)snes), PETSC_ERR_PLIB, "SNES code should have previously errored due to negative reason");
4446:   snes->reason = reason;
4447:   PetscFunctionReturn(PETSC_SUCCESS);
4448: }

4450: /*@
4451:   SNESSetConvergenceHistory - Sets the arrays used to hold the convergence history.

4453:   Logically Collective

4455:   Input Parameters:
4456: + snes  - iterative context obtained from `SNESCreate()`
4457: . a     - array to hold history, this array will contain the function norms computed at each step
4458: . its   - integer array holds the number of linear iterations for each solve.
4459: . na    - size of `a` and `its`
4460: - reset - `PETSC_TRUE` indicates each new nonlinear solve resets the history counter to zero,
4461:           else it continues storing new values for new nonlinear solves after the old ones

4463:   Level: intermediate

4465:   Notes:
4466:   If 'a' and 'its' are `NULL` then space is allocated for the history. If 'na' is `PETSC_DECIDE` (or, deprecated, `PETSC_DEFAULT`) then a
4467:   default array of length 1,000 is allocated.

4469:   This routine is useful, e.g., when running a code for purposes
4470:   of accurate performance monitoring, when no I/O should be done
4471:   during the section of code that is being timed.

4473:   If the arrays run out of space after a number of iterations then the later values are not saved in the history

4475: .seealso: [](ch_snes), `SNES`, `SNESSolve()`, `SNESGetConvergenceHistory()`
4476: @*/
4477: PetscErrorCode SNESSetConvergenceHistory(SNES snes, PetscReal a[], PetscInt its[], PetscInt na, PetscBool reset)
4478: {
4479:   PetscFunctionBegin;
4481:   if (a) PetscAssertPointer(a, 2);
4482:   if (its) PetscAssertPointer(its, 3);
4483:   if (!a) {
4484:     if (na == PETSC_DECIDE) na = 1000;
4485:     PetscCall(PetscCalloc2(na, &a, na, &its));
4486:     snes->conv_hist_alloc = PETSC_TRUE;
4487:   }
4488:   snes->conv_hist       = a;
4489:   snes->conv_hist_its   = its;
4490:   snes->conv_hist_max   = (size_t)na;
4491:   snes->conv_hist_len   = 0;
4492:   snes->conv_hist_reset = reset;
4493:   PetscFunctionReturn(PETSC_SUCCESS);
4494: }

4496: #if defined(PETSC_HAVE_MATLAB)
4497:   #include <engine.h> /* MATLAB include file */
4498:   #include <mex.h>    /* MATLAB include file */

4500: PETSC_EXTERN mxArray *SNESGetConvergenceHistoryMatlab(SNES snes)
4501: {
4502:   mxArray   *mat;
4503:   PetscInt   i;
4504:   PetscReal *ar;

4506:   mat = mxCreateDoubleMatrix(snes->conv_hist_len, 1, mxREAL);
4507:   ar  = (PetscReal *)mxGetData(mat);
4508:   for (i = 0; i < snes->conv_hist_len; i++) ar[i] = snes->conv_hist[i];
4509:   return mat;
4510: }
4511: #endif

4513: /*@C
4514:   SNESGetConvergenceHistory - Gets the arrays used to hold the convergence history.

4516:   Not Collective

4518:   Input Parameter:
4519: . snes - iterative context obtained from `SNESCreate()`

4521:   Output Parameters:
4522: + a   - array to hold history, usually was set with `SNESSetConvergenceHistory()`
4523: . its - integer array holds the number of linear iterations (or
4524:          negative if not converged) for each solve.
4525: - na  - size of `a` and `its`

4527:   Level: intermediate

4529:   Note:
4530:   This routine is useful, e.g., when running a code for purposes
4531:   of accurate performance monitoring, when no I/O should be done
4532:   during the section of code that is being timed.

4534:   Fortran Notes:
4535:   Return the arrays with ``SNESRestoreConvergenceHistory()`

4537:   Use the arguments
4538: .vb
4539:   PetscReal, pointer :: a(:)
4540:   PetscInt, pointer :: its(:)
4541: .ve

4543: .seealso: [](ch_snes), `SNES`, `SNESSolve()`, `SNESSetConvergenceHistory()`
4544: @*/
4545: PetscErrorCode SNESGetConvergenceHistory(SNES snes, PetscReal *a[], PetscInt *its[], PetscInt *na)
4546: {
4547:   PetscFunctionBegin;
4549:   if (a) *a = snes->conv_hist;
4550:   if (its) *its = snes->conv_hist_its;
4551:   if (na) *na = (PetscInt)snes->conv_hist_len;
4552:   PetscFunctionReturn(PETSC_SUCCESS);
4553: }

4555: /*@C
4556:   SNESSetUpdate - Sets the general-purpose update function called
4557:   at the beginning of every iteration of the nonlinear solve. Specifically
4558:   it is called just before the Jacobian is "evaluated" and after the function
4559:   evaluation.

4561:   Logically Collective

4563:   Input Parameters:
4564: + snes - The nonlinear solver context
4565: - func - The update function; for calling sequence see `SNESUpdateFn`

4567:   Level: advanced

4569:   Notes:
4570:   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
4571:   to `SNESSetFunction()`, or `SNESSetPicard()`
4572:   This is not used by most users, and it is intended to provide a general hook that is run
4573:   right before the direction step is computed.

4575:   Users are free to modify the current residual vector,
4576:   the current linearization point, or any other vector associated to the specific solver used.
4577:   If such modifications take place, it is the user responsibility to update all the relevant
4578:   vectors. For example, if one is adjusting the model parameters at each Newton step their code may look like
4579: .vb
4580:   PetscErrorCode update(SNES snes, PetscInt iteration)
4581:   {
4582:     PetscFunctionBeginUser;
4583:     if (iteration > 0) {
4584:       // update the model parameters here
4585:       Vec x,f;
4586:       PetscCall(SNESGetSolution(snes,&x));
4587:       PetcCall(SNESGetFunction(snes,&f,NULL,NULL));
4588:       PetscCall(SNESComputeFunction(snes,x,f));
4589:     }
4590:     PetscFunctionReturn(PETSC_SUCCESS);
4591:   }
4592: .ve

4594:   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.

4596: .seealso: [](ch_snes), `SNES`, `SNESSolve()`, `SNESSetJacobian()`, `SNESLineSearchSetPreCheck()`, `SNESLineSearchSetPostCheck()`, `SNESNewtonTRSetPreCheck()`, `SNESNewtonTRSetPostCheck()`,
4597:          `SNESMonitorSet()`
4598: @*/
4599: PetscErrorCode SNESSetUpdate(SNES snes, SNESUpdateFn *func)
4600: {
4601:   PetscFunctionBegin;
4603:   snes->ops->update = func;
4604:   PetscFunctionReturn(PETSC_SUCCESS);
4605: }

4607: /*@
4608:   SNESConvergedReasonView - Displays the reason a `SNES` solve converged or diverged to a viewer

4610:   Collective

4612:   Input Parameters:
4613: + snes   - iterative context obtained from `SNESCreate()`
4614: - viewer - the viewer to display the reason

4616:   Options Database Keys:
4617: + -snes_converged_reason          - print reason for converged or diverged, also prints number of iterations
4618: - -snes_converged_reason ::failed - only print reason and number of iterations when diverged

4620:   Level: beginner

4622:   Note:
4623:   To change the format of the output call `PetscViewerPushFormat`(viewer,format) before this call. Use `PETSC_VIEWER_DEFAULT` for the default,
4624:   use `PETSC_VIEWER_FAILED` to only display a reason if it fails.

4626: .seealso: [](ch_snes), `SNESConvergedReason`, `PetscViewer`, `SNES`,
4627:           `SNESCreate()`, `SNESSetUp()`, `SNESDestroy()`, `SNESSetTolerances()`, `SNESConvergedDefault()`, `SNESGetConvergedReason()`,
4628:           `SNESConvergedReasonViewFromOptions()`,
4629:           `PetscViewerPushFormat()`, `PetscViewerPopFormat()`
4630: @*/
4631: PetscErrorCode SNESConvergedReasonView(SNES snes, PetscViewer viewer)
4632: {
4633:   PetscViewerFormat format;
4634:   PetscBool         isAscii;

4636:   PetscFunctionBegin;
4637:   if (!viewer) viewer = PETSC_VIEWER_STDOUT_(PetscObjectComm((PetscObject)snes));
4638:   PetscCall(PetscObjectTypeCompare((PetscObject)viewer, PETSCVIEWERASCII, &isAscii));
4639:   if (isAscii) {
4640:     PetscCall(PetscViewerGetFormat(viewer, &format));
4641:     PetscCall(PetscViewerASCIIAddTab(viewer, ((PetscObject)snes)->tablevel + 1));
4642:     if (format == PETSC_VIEWER_ASCII_INFO_DETAIL) {
4643:       DM       dm;
4644:       Vec      u;
4645:       PetscDS  prob;
4646:       PetscInt Nf, f;
4647:       PetscErrorCode (**exactSol)(PetscInt, PetscReal, const PetscReal[], PetscInt, PetscScalar[], void *);
4648:       void    **exactCtx;
4649:       PetscReal error;

4651:       PetscCall(SNESGetDM(snes, &dm));
4652:       PetscCall(SNESGetSolution(snes, &u));
4653:       PetscCall(DMGetDS(dm, &prob));
4654:       PetscCall(PetscDSGetNumFields(prob, &Nf));
4655:       PetscCall(PetscMalloc2(Nf, &exactSol, Nf, &exactCtx));
4656:       for (f = 0; f < Nf; ++f) PetscCall(PetscDSGetExactSolution(prob, f, &exactSol[f], &exactCtx[f]));
4657:       PetscCall(DMComputeL2Diff(dm, 0.0, exactSol, exactCtx, u, &error));
4658:       PetscCall(PetscFree2(exactSol, exactCtx));
4659:       if (error < 1.0e-11) PetscCall(PetscViewerASCIIPrintf(viewer, "L_2 Error: < 1.0e-11\n"));
4660:       else PetscCall(PetscViewerASCIIPrintf(viewer, "L_2 Error: %g\n", (double)error));
4661:     }
4662:     if (snes->reason > 0 && format != PETSC_VIEWER_FAILED) {
4663:       if (((PetscObject)snes)->prefix) {
4664:         PetscCall(PetscViewerASCIIPrintf(viewer, "Nonlinear %s solve converged due to %s iterations %" PetscInt_FMT "\n", ((PetscObject)snes)->prefix, SNESConvergedReasons[snes->reason], snes->iter));
4665:       } else {
4666:         PetscCall(PetscViewerASCIIPrintf(viewer, "Nonlinear solve converged due to %s iterations %" PetscInt_FMT "\n", SNESConvergedReasons[snes->reason], snes->iter));
4667:       }
4668:     } else if (snes->reason <= 0) {
4669:       if (((PetscObject)snes)->prefix) {
4670:         PetscCall(PetscViewerASCIIPrintf(viewer, "Nonlinear %s solve did not converge due to %s iterations %" PetscInt_FMT "\n", ((PetscObject)snes)->prefix, SNESConvergedReasons[snes->reason], snes->iter));
4671:       } else {
4672:         PetscCall(PetscViewerASCIIPrintf(viewer, "Nonlinear solve did not converge due to %s iterations %" PetscInt_FMT "\n", SNESConvergedReasons[snes->reason], snes->iter));
4673:       }
4674:     }
4675:     PetscCall(PetscViewerASCIISubtractTab(viewer, ((PetscObject)snes)->tablevel + 1));
4676:   }
4677:   PetscFunctionReturn(PETSC_SUCCESS);
4678: }

4680: /*@C
4681:   SNESConvergedReasonViewSet - Sets an ADDITIONAL function that is to be used at the
4682:   end of the nonlinear solver to display the convergence reason of the nonlinear solver.

4684:   Logically Collective

4686:   Input Parameters:
4687: + snes              - the `SNES` context
4688: . f                 - the `SNESConvergedReason` view function
4689: . vctx              - [optional] user-defined context for private data for the `SNESConvergedReason` view function (use `NULL` if no context is desired)
4690: - reasonviewdestroy - [optional] routine that frees the context (may be `NULL`), see `PetscCtxDestroyFn` for the calling sequence

4692:   Calling sequence of `f`:
4693: + snes - the `SNES` context
4694: - vctx - [optional] context for private data for the function

4696:   Options Database Keys:
4697: + -snes_converged_reason             - sets a default `SNESConvergedReasonView()`
4698: - -snes_converged_reason_view_cancel - cancels all converged reason viewers that have been hardwired into a code by
4699:                                        calls to `SNESConvergedReasonViewSet()`, but does not cancel those set via the options database.

4701:   Level: intermediate

4703:   Note:
4704:   Several different converged reason view routines may be set by calling
4705:   `SNESConvergedReasonViewSet()` multiple times; all will be called in the
4706:   order in which they were set.

4708: .seealso: [](ch_snes), `SNES`, `SNESSolve()`, `SNESConvergedReason`, `SNESGetConvergedReason()`, `SNESConvergedReasonView()`, `SNESConvergedReasonViewCancel()`,
4709:           `PetscCtxDestroyFn`
4710: @*/
4711: PetscErrorCode SNESConvergedReasonViewSet(SNES snes, PetscErrorCode (*f)(SNES snes, void *vctx), void *vctx, PetscCtxDestroyFn *reasonviewdestroy)
4712: {
4713:   PetscFunctionBegin;
4715:   for (PetscInt i = 0; i < snes->numberreasonviews; i++) {
4716:     PetscBool identical;

4718:     PetscCall(PetscMonitorCompare((PetscErrorCode (*)(void))(PetscVoidFn *)f, vctx, reasonviewdestroy, (PetscErrorCode (*)(void))(PetscVoidFn *)snes->reasonview[i], snes->reasonviewcontext[i], snes->reasonviewdestroy[i], &identical));
4719:     if (identical) PetscFunctionReturn(PETSC_SUCCESS);
4720:   }
4721:   PetscCheck(snes->numberreasonviews < MAXSNESREASONVIEWS, PETSC_COMM_SELF, PETSC_ERR_ARG_OUTOFRANGE, "Too many SNES reasonview set");
4722:   snes->reasonview[snes->numberreasonviews]          = f;
4723:   snes->reasonviewdestroy[snes->numberreasonviews]   = reasonviewdestroy;
4724:   snes->reasonviewcontext[snes->numberreasonviews++] = vctx;
4725:   PetscFunctionReturn(PETSC_SUCCESS);
4726: }

4728: /*@
4729:   SNESConvergedReasonViewFromOptions - Processes command line options to determine if/how a `SNESConvergedReason` is to be viewed at the end of `SNESSolve()`
4730:   All the user-provided viewer routines set with `SNESConvergedReasonViewSet()` will be called, if they exist.

4732:   Collective

4734:   Input Parameter:
4735: . snes - the `SNES` object

4737:   Level: advanced

4739: .seealso: [](ch_snes), `SNES`, `SNESConvergedReason`, `SNESConvergedReasonViewSet()`, `SNESCreate()`, `SNESSetUp()`, `SNESDestroy()`,
4740:           `SNESSetTolerances()`, `SNESConvergedDefault()`, `SNESGetConvergedReason()`, `SNESConvergedReasonView()`
4741: @*/
4742: PetscErrorCode SNESConvergedReasonViewFromOptions(SNES snes)
4743: {
4744:   static PetscBool incall = PETSC_FALSE;

4746:   PetscFunctionBegin;
4747:   if (incall) PetscFunctionReturn(PETSC_SUCCESS);
4748:   incall = PETSC_TRUE;

4750:   /* All user-provided viewers are called first, if they exist. */
4751:   for (PetscInt i = 0; i < snes->numberreasonviews; i++) PetscCall((*snes->reasonview[i])(snes, snes->reasonviewcontext[i]));

4753:   /* Call PETSc default routine if users ask for it */
4754:   if (snes->convergedreasonviewer) {
4755:     PetscCall(PetscViewerPushFormat(snes->convergedreasonviewer, snes->convergedreasonformat));
4756:     PetscCall(SNESConvergedReasonView(snes, snes->convergedreasonviewer));
4757:     PetscCall(PetscViewerPopFormat(snes->convergedreasonviewer));
4758:   }
4759:   incall = PETSC_FALSE;
4760:   PetscFunctionReturn(PETSC_SUCCESS);
4761: }

4763: /*@
4764:   SNESSolve - Solves a nonlinear system $F(x) = b $ associated with a `SNES` object

4766:   Collective

4768:   Input Parameters:
4769: + snes - the `SNES` context
4770: . b    - the constant part of the equation $F(x) = b$, or `NULL` to use zero.
4771: - x    - the solution vector.

4773:   Level: beginner

4775:   Note:
4776:   The user should initialize the vector, `x`, with the initial guess
4777:   for the nonlinear solve prior to calling `SNESSolve()` .

4779: .seealso: [](ch_snes), `SNES`, `SNESCreate()`, `SNESDestroy()`, `SNESSetFunction()`, `SNESSetJacobian()`, `SNESSetGridSequence()`, `SNESGetSolution()`,
4780:           `SNESNewtonTRSetPreCheck()`, `SNESNewtonTRGetPreCheck()`, `SNESNewtonTRSetPostCheck()`, `SNESNewtonTRGetPostCheck()`,
4781:           `SNESLineSearchSetPostCheck()`, `SNESLineSearchGetPostCheck()`, `SNESLineSearchSetPreCheck()`, `SNESLineSearchGetPreCheck()`
4782: @*/
4783: PetscErrorCode SNESSolve(SNES snes, Vec b, Vec x)
4784: {
4785:   PetscBool flg;
4786:   PetscInt  grid;
4787:   Vec       xcreated = NULL;
4788:   DM        dm;

4790:   PetscFunctionBegin;
4793:   if (x) PetscCheckSameComm(snes, 1, x, 3);
4795:   if (b) PetscCheckSameComm(snes, 1, b, 2);

4797:   /* High level operations using the nonlinear solver */
4798:   {
4799:     PetscViewer       viewer;
4800:     PetscViewerFormat format;
4801:     PetscInt          num;
4802:     PetscBool         flg;
4803:     static PetscBool  incall = PETSC_FALSE;

4805:     if (!incall) {
4806:       /* Estimate the convergence rate of the discretization */
4807:       PetscCall(PetscOptionsCreateViewer(PetscObjectComm((PetscObject)snes), ((PetscObject)snes)->options, ((PetscObject)snes)->prefix, "-snes_convergence_estimate", &viewer, &format, &flg));
4808:       if (flg) {
4809:         PetscConvEst conv;
4810:         DM           dm;
4811:         PetscReal   *alpha; /* Convergence rate of the solution error for each field in the L_2 norm */
4812:         PetscInt     Nf;

4814:         incall = PETSC_TRUE;
4815:         PetscCall(SNESGetDM(snes, &dm));
4816:         PetscCall(DMGetNumFields(dm, &Nf));
4817:         PetscCall(PetscCalloc1(Nf, &alpha));
4818:         PetscCall(PetscConvEstCreate(PetscObjectComm((PetscObject)snes), &conv));
4819:         PetscCall(PetscConvEstSetSolver(conv, (PetscObject)snes));
4820:         PetscCall(PetscConvEstSetFromOptions(conv));
4821:         PetscCall(PetscConvEstSetUp(conv));
4822:         PetscCall(PetscConvEstGetConvRate(conv, alpha));
4823:         PetscCall(PetscViewerPushFormat(viewer, format));
4824:         PetscCall(PetscConvEstRateView(conv, alpha, viewer));
4825:         PetscCall(PetscViewerPopFormat(viewer));
4826:         PetscCall(PetscViewerDestroy(&viewer));
4827:         PetscCall(PetscConvEstDestroy(&conv));
4828:         PetscCall(PetscFree(alpha));
4829:         incall = PETSC_FALSE;
4830:       }
4831:       /* Adaptively refine the initial grid */
4832:       num = 1;
4833:       PetscCall(PetscOptionsGetInt(NULL, ((PetscObject)snes)->prefix, "-snes_adapt_initial", &num, &flg));
4834:       if (flg) {
4835:         DMAdaptor adaptor;

4837:         incall = PETSC_TRUE;
4838:         PetscCall(DMAdaptorCreate(PetscObjectComm((PetscObject)snes), &adaptor));
4839:         PetscCall(DMAdaptorSetSolver(adaptor, snes));
4840:         PetscCall(DMAdaptorSetSequenceLength(adaptor, num));
4841:         PetscCall(DMAdaptorSetFromOptions(adaptor));
4842:         PetscCall(DMAdaptorSetUp(adaptor));
4843:         PetscCall(DMAdaptorAdapt(adaptor, x, DM_ADAPTATION_INITIAL, &dm, &x));
4844:         PetscCall(DMAdaptorDestroy(&adaptor));
4845:         incall = PETSC_FALSE;
4846:       }
4847:       /* Use grid sequencing to adapt */
4848:       num = 0;
4849:       PetscCall(PetscOptionsGetInt(NULL, ((PetscObject)snes)->prefix, "-snes_adapt_sequence", &num, NULL));
4850:       if (num) {
4851:         DMAdaptor   adaptor;
4852:         const char *prefix;

4854:         incall = PETSC_TRUE;
4855:         PetscCall(DMAdaptorCreate(PetscObjectComm((PetscObject)snes), &adaptor));
4856:         PetscCall(SNESGetOptionsPrefix(snes, &prefix));
4857:         PetscCall(DMAdaptorSetOptionsPrefix(adaptor, prefix));
4858:         PetscCall(DMAdaptorSetSolver(adaptor, snes));
4859:         PetscCall(DMAdaptorSetSequenceLength(adaptor, num));
4860:         PetscCall(DMAdaptorSetFromOptions(adaptor));
4861:         PetscCall(DMAdaptorSetUp(adaptor));
4862:         PetscCall(PetscObjectViewFromOptions((PetscObject)adaptor, NULL, "-snes_adapt_view"));
4863:         PetscCall(DMAdaptorAdapt(adaptor, x, DM_ADAPTATION_SEQUENTIAL, &dm, &x));
4864:         PetscCall(DMAdaptorDestroy(&adaptor));
4865:         incall = PETSC_FALSE;
4866:       }
4867:     }
4868:   }
4869:   if (!x) x = snes->vec_sol;
4870:   if (!x) {
4871:     PetscCall(SNESGetDM(snes, &dm));
4872:     PetscCall(DMCreateGlobalVector(dm, &xcreated));
4873:     x = xcreated;
4874:   }
4875:   PetscCall(SNESViewFromOptions(snes, NULL, "-snes_view_pre"));

4877:   for (grid = 0; grid < snes->gridsequence; grid++) PetscCall(PetscViewerASCIIPushTab(PETSC_VIEWER_STDOUT_(PetscObjectComm((PetscObject)snes))));
4878:   for (grid = 0; grid < snes->gridsequence + 1; grid++) {
4879:     /* set solution vector */
4880:     if (!grid) PetscCall(PetscObjectReference((PetscObject)x));
4881:     PetscCall(VecDestroy(&snes->vec_sol));
4882:     snes->vec_sol = x;
4883:     PetscCall(SNESGetDM(snes, &dm));

4885:     /* set affine vector if provided */
4886:     if (b) PetscCall(PetscObjectReference((PetscObject)b));
4887:     PetscCall(VecDestroy(&snes->vec_rhs));
4888:     snes->vec_rhs = b;

4890:     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");
4891:     PetscCheck(snes->vec_func != snes->vec_sol, PETSC_COMM_SELF, PETSC_ERR_ARG_IDN, "Solution vector cannot be function vector");
4892:     PetscCheck(snes->vec_rhs != snes->vec_sol, PETSC_COMM_SELF, PETSC_ERR_ARG_IDN, "Solution vector cannot be right-hand side vector");
4893:     if (!snes->vec_sol_update /* && snes->vec_sol */) PetscCall(VecDuplicate(snes->vec_sol, &snes->vec_sol_update));
4894:     PetscCall(DMShellSetGlobalVector(dm, snes->vec_sol));
4895:     PetscCall(SNESSetUp(snes));

4897:     if (!grid) {
4898:       if (snes->ops->computeinitialguess) PetscCallBack("SNES callback compute initial guess", (*snes->ops->computeinitialguess)(snes, snes->vec_sol, snes->initialguessP));
4899:     }

4901:     if (snes->conv_hist_reset) snes->conv_hist_len = 0;
4902:     PetscCall(SNESResetCounters(snes));
4903:     snes->reason = SNES_CONVERGED_ITERATING;
4904:     PetscCall(PetscLogEventBegin(SNES_Solve, snes, 0, 0, 0));
4905:     PetscUseTypeMethod(snes, solve);
4906:     PetscCall(PetscLogEventEnd(SNES_Solve, snes, 0, 0, 0));
4907:     PetscCheck(snes->reason, PETSC_COMM_SELF, PETSC_ERR_PLIB, "Internal error, solver %s returned without setting converged reason", ((PetscObject)snes)->type_name);
4908:     snes->domainerror = PETSC_FALSE; /* clear the flag if it has been set */

4910:     if (snes->lagjac_persist) snes->jac_iter += snes->iter;
4911:     if (snes->lagpre_persist) snes->pre_iter += snes->iter;

4913:     PetscCall(PetscOptionsCreateViewer(PetscObjectComm((PetscObject)snes), ((PetscObject)snes)->options, ((PetscObject)snes)->prefix, "-snes_test_local_min", NULL, NULL, &flg));
4914:     if (flg && !PetscPreLoadingOn) PetscCall(SNESTestLocalMin(snes));
4915:     /* Call converged reason views. This may involve user-provided viewers as well */
4916:     PetscCall(SNESConvergedReasonViewFromOptions(snes));

4918:     if (snes->errorifnotconverged) {
4919:       if (snes->reason < 0) PetscCall(SNESMonitorCancel(snes));
4920:       PetscCheck(snes->reason >= 0, PetscObjectComm((PetscObject)snes), PETSC_ERR_NOT_CONVERGED, "SNESSolve has not converged");
4921:     }
4922:     if (snes->reason < 0) break;
4923:     if (grid < snes->gridsequence) {
4924:       DM  fine;
4925:       Vec xnew;
4926:       Mat interp;

4928:       PetscCall(DMRefine(snes->dm, PetscObjectComm((PetscObject)snes), &fine));
4929:       PetscCheck(fine, PetscObjectComm((PetscObject)snes), PETSC_ERR_ARG_INCOMP, "DMRefine() did not perform any refinement, cannot continue grid sequencing");
4930:       PetscCall(DMGetCoordinatesLocalSetUp(fine));
4931:       PetscCall(DMCreateInterpolation(snes->dm, fine, &interp, NULL));
4932:       PetscCall(DMCreateGlobalVector(fine, &xnew));
4933:       PetscCall(MatInterpolate(interp, x, xnew));
4934:       PetscCall(DMInterpolate(snes->dm, interp, fine));
4935:       PetscCall(MatDestroy(&interp));
4936:       x = xnew;

4938:       PetscCall(SNESReset(snes));
4939:       PetscCall(SNESSetDM(snes, fine));
4940:       PetscCall(SNESResetFromOptions(snes));
4941:       PetscCall(DMDestroy(&fine));
4942:       PetscCall(PetscViewerASCIIPopTab(PETSC_VIEWER_STDOUT_(PetscObjectComm((PetscObject)snes))));
4943:     }
4944:   }
4945:   PetscCall(SNESViewFromOptions(snes, NULL, "-snes_view"));
4946:   PetscCall(VecViewFromOptions(snes->vec_sol, (PetscObject)snes, "-snes_view_solution"));
4947:   PetscCall(DMMonitor(snes->dm));
4948:   PetscCall(SNESMonitorPauseFinal_Internal(snes));

4950:   PetscCall(VecDestroy(&xcreated));
4951:   PetscCall(PetscObjectSAWsBlock((PetscObject)snes));
4952:   PetscFunctionReturn(PETSC_SUCCESS);
4953: }

4955: /* --------- Internal routines for SNES Package --------- */

4957: /*@
4958:   SNESSetType - Sets the algorithm/method to be used to solve the nonlinear system with the given `SNES`

4960:   Collective

4962:   Input Parameters:
4963: + snes - the `SNES` context
4964: - type - a known method

4966:   Options Database Key:
4967: . -snes_type <type> - Sets the method; use -help for a list
4968:    of available methods (for instance, newtonls or newtontr)

4970:   Level: intermediate

4972:   Notes:
4973:   See `SNESType` for available methods (for instance)
4974: +    `SNESNEWTONLS` - Newton's method with line search
4975:   (systems of nonlinear equations)
4976: -    `SNESNEWTONTR` - Newton's method with trust region
4977:   (systems of nonlinear equations)

4979:   Normally, it is best to use the `SNESSetFromOptions()` command and then
4980:   set the `SNES` solver type from the options database rather than by using
4981:   this routine.  Using the options database provides the user with
4982:   maximum flexibility in evaluating the many nonlinear solvers.
4983:   The `SNESSetType()` routine is provided for those situations where it
4984:   is necessary to set the nonlinear solver independently of the command
4985:   line or options database.  This might be the case, for example, when
4986:   the choice of solver changes during the execution of the program,
4987:   and the user's application is taking responsibility for choosing the
4988:   appropriate method.

4990:   Developer Note:
4991:   `SNESRegister()` adds a constructor for a new `SNESType` to `SNESList`, `SNESSetType()` locates
4992:   the constructor in that list and calls it to create the specific object.

4994: .seealso: [](ch_snes), `SNES`, `SNESSolve()`, `SNESType`, `SNESCreate()`, `SNESDestroy()`, `SNESGetType()`, `SNESSetFromOptions()`
4995: @*/
4996: PetscErrorCode SNESSetType(SNES snes, SNESType type)
4997: {
4998:   PetscBool match;
4999:   PetscErrorCode (*r)(SNES);

5001:   PetscFunctionBegin;
5003:   PetscAssertPointer(type, 2);

5005:   PetscCall(PetscObjectTypeCompare((PetscObject)snes, type, &match));
5006:   if (match) PetscFunctionReturn(PETSC_SUCCESS);

5008:   PetscCall(PetscFunctionListFind(SNESList, type, &r));
5009:   PetscCheck(r, PetscObjectComm((PetscObject)snes), PETSC_ERR_ARG_UNKNOWN_TYPE, "Unable to find requested SNES type %s", type);
5010:   /* Destroy the previous private SNES context */
5011:   PetscTryTypeMethod(snes, destroy);
5012:   /* Reinitialize type-specific function pointers in SNESOps structure */
5013:   snes->ops->reset          = NULL;
5014:   snes->ops->setup          = NULL;
5015:   snes->ops->solve          = NULL;
5016:   snes->ops->view           = NULL;
5017:   snes->ops->setfromoptions = NULL;
5018:   snes->ops->destroy        = NULL;

5020:   /* It may happen the user has customized the line search before calling SNESSetType */
5021:   if (((PetscObject)snes)->type_name) PetscCall(SNESLineSearchDestroy(&snes->linesearch));

5023:   /* Call the SNESCreate_XXX routine for this particular Nonlinear solver */
5024:   snes->setupcalled = PETSC_FALSE;

5026:   PetscCall(PetscObjectChangeTypeName((PetscObject)snes, type));
5027:   PetscCall((*r)(snes));
5028:   PetscFunctionReturn(PETSC_SUCCESS);
5029: }

5031: /*@
5032:   SNESGetType - Gets the `SNES` method type and name (as a string).

5034:   Not Collective

5036:   Input Parameter:
5037: . snes - nonlinear solver context

5039:   Output Parameter:
5040: . type - `SNES` method (a character string)

5042:   Level: intermediate

5044: .seealso: [](ch_snes), `SNESSetType()`, `SNESType`, `SNESSetFromOptions()`, `SNES`
5045: @*/
5046: PetscErrorCode SNESGetType(SNES snes, SNESType *type)
5047: {
5048:   PetscFunctionBegin;
5050:   PetscAssertPointer(type, 2);
5051:   *type = ((PetscObject)snes)->type_name;
5052:   PetscFunctionReturn(PETSC_SUCCESS);
5053: }

5055: /*@
5056:   SNESSetSolution - Sets the solution vector for use by the `SNES` routines.

5058:   Logically Collective

5060:   Input Parameters:
5061: + snes - the `SNES` context obtained from `SNESCreate()`
5062: - u    - the solution vector

5064:   Level: beginner

5066: .seealso: [](ch_snes), `SNES`, `SNESSolve()`, `SNESGetSolution()`, `Vec`
5067: @*/
5068: PetscErrorCode SNESSetSolution(SNES snes, Vec u)
5069: {
5070:   DM dm;

5072:   PetscFunctionBegin;
5075:   PetscCall(PetscObjectReference((PetscObject)u));
5076:   PetscCall(VecDestroy(&snes->vec_sol));

5078:   snes->vec_sol = u;

5080:   PetscCall(SNESGetDM(snes, &dm));
5081:   PetscCall(DMShellSetGlobalVector(dm, u));
5082:   PetscFunctionReturn(PETSC_SUCCESS);
5083: }

5085: /*@
5086:   SNESGetSolution - Returns the vector where the approximate solution is
5087:   stored. This is the fine grid solution when using `SNESSetGridSequence()`.

5089:   Not Collective, but `x` is parallel if `snes` is parallel

5091:   Input Parameter:
5092: . snes - the `SNES` context

5094:   Output Parameter:
5095: . x - the solution

5097:   Level: intermediate

5099: .seealso: [](ch_snes), `SNESSetSolution()`, `SNESSolve()`, `SNES`, `SNESGetSolutionUpdate()`, `SNESGetFunction()`
5100: @*/
5101: PetscErrorCode SNESGetSolution(SNES snes, Vec *x)
5102: {
5103:   PetscFunctionBegin;
5105:   PetscAssertPointer(x, 2);
5106:   *x = snes->vec_sol;
5107:   PetscFunctionReturn(PETSC_SUCCESS);
5108: }

5110: /*@
5111:   SNESGetSolutionUpdate - Returns the vector where the solution update is
5112:   stored.

5114:   Not Collective, but `x` is parallel if `snes` is parallel

5116:   Input Parameter:
5117: . snes - the `SNES` context

5119:   Output Parameter:
5120: . x - the solution update

5122:   Level: advanced

5124: .seealso: [](ch_snes), `SNES`, `SNESGetSolution()`, `SNESGetFunction()`
5125: @*/
5126: PetscErrorCode SNESGetSolutionUpdate(SNES snes, Vec *x)
5127: {
5128:   PetscFunctionBegin;
5130:   PetscAssertPointer(x, 2);
5131:   *x = snes->vec_sol_update;
5132:   PetscFunctionReturn(PETSC_SUCCESS);
5133: }

5135: /*@C
5136:   SNESGetFunction - Returns the function that defines the nonlinear system set with `SNESSetFunction()`

5138:   Not Collective, but `r` is parallel if `snes` is parallel. Collective if `r` is requested, but has not been created yet.

5140:   Input Parameter:
5141: . snes - the `SNES` context

5143:   Output Parameters:
5144: + r   - the vector that is used to store residuals (or `NULL` if you don't want it)
5145: . f   - the function (or `NULL` if you don't want it);  for calling sequence see `SNESFunctionFn`
5146: - ctx - the function context (or `NULL` if you don't want it)

5148:   Level: advanced

5150:   Note:
5151:   The vector `r` DOES NOT, in general, contain the current value of the `SNES` nonlinear function

5153: .seealso: [](ch_snes), `SNES`, `SNESSolve()`, `SNESSetFunction()`, `SNESGetSolution()`, `SNESFunctionFn`
5154: @*/
5155: PetscErrorCode SNESGetFunction(SNES snes, Vec *r, SNESFunctionFn **f, void **ctx)
5156: {
5157:   DM dm;

5159:   PetscFunctionBegin;
5161:   if (r) {
5162:     if (!snes->vec_func) {
5163:       if (snes->vec_rhs) {
5164:         PetscCall(VecDuplicate(snes->vec_rhs, &snes->vec_func));
5165:       } else if (snes->vec_sol) {
5166:         PetscCall(VecDuplicate(snes->vec_sol, &snes->vec_func));
5167:       } else if (snes->dm) {
5168:         PetscCall(DMCreateGlobalVector(snes->dm, &snes->vec_func));
5169:       }
5170:     }
5171:     *r = snes->vec_func;
5172:   }
5173:   PetscCall(SNESGetDM(snes, &dm));
5174:   PetscCall(DMSNESGetFunction(dm, f, ctx));
5175:   PetscFunctionReturn(PETSC_SUCCESS);
5176: }

5178: /*@C
5179:   SNESGetNGS - Returns the function and context set with `SNESSetNGS()`

5181:   Input Parameter:
5182: . snes - the `SNES` context

5184:   Output Parameters:
5185: + f   - the function (or `NULL`) see `SNESNGSFn` for calling sequence
5186: - ctx - the function context (or `NULL`)

5188:   Level: advanced

5190: .seealso: [](ch_snes), `SNESSetNGS()`, `SNESGetFunction()`, `SNESNGSFn`
5191: @*/
5192: PetscErrorCode SNESGetNGS(SNES snes, SNESNGSFn **f, void **ctx)
5193: {
5194:   DM dm;

5196:   PetscFunctionBegin;
5198:   PetscCall(SNESGetDM(snes, &dm));
5199:   PetscCall(DMSNESGetNGS(dm, f, ctx));
5200:   PetscFunctionReturn(PETSC_SUCCESS);
5201: }

5203: /*@
5204:   SNESSetOptionsPrefix - Sets the prefix used for searching for all
5205:   `SNES` options in the database.

5207:   Logically Collective

5209:   Input Parameters:
5210: + snes   - the `SNES` context
5211: - prefix - the prefix to prepend to all option names

5213:   Level: advanced

5215:   Note:
5216:   A hyphen (-) must NOT be given at the beginning of the prefix name.
5217:   The first character of all runtime options is AUTOMATICALLY the hyphen.

5219: .seealso: [](ch_snes), `SNES`, `SNESSetFromOptions()`, `SNESAppendOptionsPrefix()`
5220: @*/
5221: PetscErrorCode SNESSetOptionsPrefix(SNES snes, const char prefix[])
5222: {
5223:   PetscFunctionBegin;
5225:   PetscCall(PetscObjectSetOptionsPrefix((PetscObject)snes, prefix));
5226:   if (!snes->ksp) PetscCall(SNESGetKSP(snes, &snes->ksp));
5227:   if (snes->linesearch) {
5228:     PetscCall(SNESGetLineSearch(snes, &snes->linesearch));
5229:     PetscCall(PetscObjectSetOptionsPrefix((PetscObject)snes->linesearch, prefix));
5230:   }
5231:   PetscCall(KSPSetOptionsPrefix(snes->ksp, prefix));
5232:   PetscFunctionReturn(PETSC_SUCCESS);
5233: }

5235: /*@
5236:   SNESAppendOptionsPrefix - Appends to the prefix used for searching for all
5237:   `SNES` options in the database.

5239:   Logically Collective

5241:   Input Parameters:
5242: + snes   - the `SNES` context
5243: - prefix - the prefix to prepend to all option names

5245:   Level: advanced

5247:   Note:
5248:   A hyphen (-) must NOT be given at the beginning of the prefix name.
5249:   The first character of all runtime options is AUTOMATICALLY the hyphen.

5251: .seealso: [](ch_snes), `SNESGetOptionsPrefix()`, `SNESSetOptionsPrefix()`
5252: @*/
5253: PetscErrorCode SNESAppendOptionsPrefix(SNES snes, const char prefix[])
5254: {
5255:   PetscFunctionBegin;
5257:   PetscCall(PetscObjectAppendOptionsPrefix((PetscObject)snes, prefix));
5258:   if (!snes->ksp) PetscCall(SNESGetKSP(snes, &snes->ksp));
5259:   if (snes->linesearch) {
5260:     PetscCall(SNESGetLineSearch(snes, &snes->linesearch));
5261:     PetscCall(PetscObjectAppendOptionsPrefix((PetscObject)snes->linesearch, prefix));
5262:   }
5263:   PetscCall(KSPAppendOptionsPrefix(snes->ksp, prefix));
5264:   PetscFunctionReturn(PETSC_SUCCESS);
5265: }

5267: /*@
5268:   SNESGetOptionsPrefix - Gets the prefix used for searching for all
5269:   `SNES` options in the database.

5271:   Not Collective

5273:   Input Parameter:
5274: . snes - the `SNES` context

5276:   Output Parameter:
5277: . prefix - pointer to the prefix string used

5279:   Level: advanced

5281: .seealso: [](ch_snes), `SNES`, `SNESSetOptionsPrefix()`, `SNESAppendOptionsPrefix()`
5282: @*/
5283: PetscErrorCode SNESGetOptionsPrefix(SNES snes, const char *prefix[])
5284: {
5285:   PetscFunctionBegin;
5287:   PetscCall(PetscObjectGetOptionsPrefix((PetscObject)snes, prefix));
5288:   PetscFunctionReturn(PETSC_SUCCESS);
5289: }

5291: /*@C
5292:   SNESRegister - Adds a method to the nonlinear solver package.

5294:   Not Collective

5296:   Input Parameters:
5297: + sname    - name of a new user-defined solver
5298: - function - routine to create method context

5300:   Level: advanced

5302:   Note:
5303:   `SNESRegister()` may be called multiple times to add several user-defined solvers.

5305:   Example Usage:
5306: .vb
5307:    SNESRegister("my_solver", MySolverCreate);
5308: .ve

5310:   Then, your solver can be chosen with the procedural interface via
5311: .vb
5312:   SNESSetType(snes, "my_solver")
5313: .ve
5314:   or at runtime via the option
5315: .vb
5316:   -snes_type my_solver
5317: .ve

5319: .seealso: [](ch_snes), `SNESRegisterAll()`, `SNESRegisterDestroy()`
5320: @*/
5321: PetscErrorCode SNESRegister(const char sname[], PetscErrorCode (*function)(SNES))
5322: {
5323:   PetscFunctionBegin;
5324:   PetscCall(SNESInitializePackage());
5325:   PetscCall(PetscFunctionListAdd(&SNESList, sname, function));
5326:   PetscFunctionReturn(PETSC_SUCCESS);
5327: }

5329: PetscErrorCode SNESTestLocalMin(SNES snes)
5330: {
5331:   PetscInt    N, i, j;
5332:   Vec         u, uh, fh;
5333:   PetscScalar value;
5334:   PetscReal   norm;

5336:   PetscFunctionBegin;
5337:   PetscCall(SNESGetSolution(snes, &u));
5338:   PetscCall(VecDuplicate(u, &uh));
5339:   PetscCall(VecDuplicate(u, &fh));

5341:   /* currently only works for sequential */
5342:   PetscCall(PetscPrintf(PetscObjectComm((PetscObject)snes), "Testing FormFunction() for local min\n"));
5343:   PetscCall(VecGetSize(u, &N));
5344:   for (i = 0; i < N; i++) {
5345:     PetscCall(VecCopy(u, uh));
5346:     PetscCall(PetscPrintf(PetscObjectComm((PetscObject)snes), "i = %" PetscInt_FMT "\n", i));
5347:     for (j = -10; j < 11; j++) {
5348:       value = PetscSign(j) * PetscExpReal(PetscAbs(j) - 10.0);
5349:       PetscCall(VecSetValue(uh, i, value, ADD_VALUES));
5350:       PetscCall(SNESComputeFunction(snes, uh, fh));
5351:       PetscCall(VecNorm(fh, NORM_2, &norm));
5352:       PetscCall(PetscPrintf(PetscObjectComm((PetscObject)snes), "       j norm %" PetscInt_FMT " %18.16e\n", j, (double)norm));
5353:       value = -value;
5354:       PetscCall(VecSetValue(uh, i, value, ADD_VALUES));
5355:     }
5356:   }
5357:   PetscCall(VecDestroy(&uh));
5358:   PetscCall(VecDestroy(&fh));
5359:   PetscFunctionReturn(PETSC_SUCCESS);
5360: }

5362: /*@
5363:   SNESKSPSetUseEW - Sets `SNES` to the use Eisenstat-Walker method for
5364:   computing relative tolerance for linear solvers within an inexact
5365:   Newton method.

5367:   Logically Collective

5369:   Input Parameters:
5370: + snes - `SNES` context
5371: - flag - `PETSC_TRUE` or `PETSC_FALSE`

5373:   Options Database Keys:
5374: + -snes_ksp_ew                       - use Eisenstat-Walker method for determining linear system convergence
5375: . -snes_ksp_ew_version ver           - version of  Eisenstat-Walker method
5376: . -snes_ksp_ew_rtol0 <rtol0>         - Sets rtol0
5377: . -snes_ksp_ew_rtolmax <rtolmax>     - Sets rtolmax
5378: . -snes_ksp_ew_gamma <gamma>         - Sets gamma
5379: . -snes_ksp_ew_alpha <alpha>         - Sets alpha
5380: . -snes_ksp_ew_alpha2 <alpha2>       - Sets alpha2
5381: - -snes_ksp_ew_threshold <threshold> - Sets threshold

5383:   Level: advanced

5385:   Note:
5386:   The default is to use a constant relative tolerance for
5387:   the inner linear solvers.  Alternatively, one can use the
5388:   Eisenstat-Walker method {cite}`ew96`, where the relative convergence tolerance
5389:   is reset at each Newton iteration according progress of the nonlinear
5390:   solver.

5392: .seealso: [](ch_snes), `KSP`, `SNES`, `SNESKSPGetUseEW()`, `SNESKSPGetParametersEW()`, `SNESKSPSetParametersEW()`
5393: @*/
5394: PetscErrorCode SNESKSPSetUseEW(SNES snes, PetscBool flag)
5395: {
5396:   PetscFunctionBegin;
5399:   snes->ksp_ewconv = flag;
5400:   PetscFunctionReturn(PETSC_SUCCESS);
5401: }

5403: /*@
5404:   SNESKSPGetUseEW - Gets if `SNES` is using Eisenstat-Walker method
5405:   for computing relative tolerance for linear solvers within an
5406:   inexact Newton method.

5408:   Not Collective

5410:   Input Parameter:
5411: . snes - `SNES` context

5413:   Output Parameter:
5414: . flag - `PETSC_TRUE` or `PETSC_FALSE`

5416:   Level: advanced

5418: .seealso: [](ch_snes), `SNESKSPSetUseEW()`, `SNESKSPGetParametersEW()`, `SNESKSPSetParametersEW()`
5419: @*/
5420: PetscErrorCode SNESKSPGetUseEW(SNES snes, PetscBool *flag)
5421: {
5422:   PetscFunctionBegin;
5424:   PetscAssertPointer(flag, 2);
5425:   *flag = snes->ksp_ewconv;
5426:   PetscFunctionReturn(PETSC_SUCCESS);
5427: }

5429: /*@
5430:   SNESKSPSetParametersEW - Sets parameters for Eisenstat-Walker
5431:   convergence criteria for the linear solvers within an inexact
5432:   Newton method.

5434:   Logically Collective

5436:   Input Parameters:
5437: + snes      - `SNES` context
5438: . version   - version 1, 2 (default is 2), 3 or 4
5439: . rtol_0    - initial relative tolerance (0 <= rtol_0 < 1)
5440: . rtol_max  - maximum relative tolerance (0 <= rtol_max < 1)
5441: . gamma     - multiplicative factor for version 2 rtol computation
5442:              (0 <= gamma2 <= 1)
5443: . alpha     - power for version 2 rtol computation (1 < alpha <= 2)
5444: . alpha2    - power for safeguard
5445: - threshold - threshold for imposing safeguard (0 < threshold < 1)

5447:   Level: advanced

5449:   Notes:
5450:   Version 3 was contributed by Luis Chacon, June 2006.

5452:   Use `PETSC_CURRENT` to retain the default for any of the parameters.

5454: .seealso: [](ch_snes), `SNES`, `SNESKSPSetUseEW()`, `SNESKSPGetUseEW()`, `SNESKSPGetParametersEW()`
5455: @*/
5456: PetscErrorCode SNESKSPSetParametersEW(SNES snes, PetscInt version, PetscReal rtol_0, PetscReal rtol_max, PetscReal gamma, PetscReal alpha, PetscReal alpha2, PetscReal threshold)
5457: {
5458:   SNESKSPEW *kctx;

5460:   PetscFunctionBegin;
5462:   kctx = (SNESKSPEW *)snes->kspconvctx;
5463:   PetscCheck(kctx, PETSC_COMM_SELF, PETSC_ERR_ARG_WRONGSTATE, "No Eisenstat-Walker context existing");

5472:   if (version != PETSC_CURRENT) kctx->version = version;
5473:   if (rtol_0 != (PetscReal)PETSC_CURRENT) kctx->rtol_0 = rtol_0;
5474:   if (rtol_max != (PetscReal)PETSC_CURRENT) kctx->rtol_max = rtol_max;
5475:   if (gamma != (PetscReal)PETSC_CURRENT) kctx->gamma = gamma;
5476:   if (alpha != (PetscReal)PETSC_CURRENT) kctx->alpha = alpha;
5477:   if (alpha2 != (PetscReal)PETSC_CURRENT) kctx->alpha2 = alpha2;
5478:   if (threshold != (PetscReal)PETSC_CURRENT) kctx->threshold = threshold;

5480:   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);
5481:   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);
5482:   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);
5483:   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);
5484:   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);
5485:   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);
5486:   PetscFunctionReturn(PETSC_SUCCESS);
5487: }

5489: /*@
5490:   SNESKSPGetParametersEW - Gets parameters for Eisenstat-Walker
5491:   convergence criteria for the linear solvers within an inexact
5492:   Newton method.

5494:   Not Collective

5496:   Input Parameter:
5497: . snes - `SNES` context

5499:   Output Parameters:
5500: + version   - version 1, 2 (default is 2), 3 or 4
5501: . rtol_0    - initial relative tolerance (0 <= rtol_0 < 1)
5502: . rtol_max  - maximum relative tolerance (0 <= rtol_max < 1)
5503: . gamma     - multiplicative factor for version 2 rtol computation (0 <= gamma2 <= 1)
5504: . alpha     - power for version 2 rtol computation (1 < alpha <= 2)
5505: . alpha2    - power for safeguard
5506: - threshold - threshold for imposing safeguard (0 < threshold < 1)

5508:   Level: advanced

5510: .seealso: [](ch_snes), `SNES`, `SNESKSPSetUseEW()`, `SNESKSPGetUseEW()`, `SNESKSPSetParametersEW()`
5511: @*/
5512: PetscErrorCode SNESKSPGetParametersEW(SNES snes, PetscInt *version, PetscReal *rtol_0, PetscReal *rtol_max, PetscReal *gamma, PetscReal *alpha, PetscReal *alpha2, PetscReal *threshold)
5513: {
5514:   SNESKSPEW *kctx;

5516:   PetscFunctionBegin;
5518:   kctx = (SNESKSPEW *)snes->kspconvctx;
5519:   PetscCheck(kctx, PETSC_COMM_SELF, PETSC_ERR_ARG_WRONGSTATE, "No Eisenstat-Walker context existing");
5520:   if (version) *version = kctx->version;
5521:   if (rtol_0) *rtol_0 = kctx->rtol_0;
5522:   if (rtol_max) *rtol_max = kctx->rtol_max;
5523:   if (gamma) *gamma = kctx->gamma;
5524:   if (alpha) *alpha = kctx->alpha;
5525:   if (alpha2) *alpha2 = kctx->alpha2;
5526:   if (threshold) *threshold = kctx->threshold;
5527:   PetscFunctionReturn(PETSC_SUCCESS);
5528: }

5530: PetscErrorCode KSPPreSolve_SNESEW(KSP ksp, Vec b, Vec x, void *ctx)
5531: {
5532:   SNES       snes = (SNES)ctx;
5533:   SNESKSPEW *kctx = (SNESKSPEW *)snes->kspconvctx;
5534:   PetscReal  rtol = PETSC_CURRENT, stol;

5536:   PetscFunctionBegin;
5537:   if (!snes->ksp_ewconv) PetscFunctionReturn(PETSC_SUCCESS);
5538:   if (!snes->iter) {
5539:     rtol = kctx->rtol_0; /* first time in, so use the original user rtol */
5540:     PetscCall(VecNorm(snes->vec_func, NORM_2, &kctx->norm_first));
5541:   } else {
5542:     PetscCheck(kctx->version >= 1 && kctx->version <= 4, PETSC_COMM_SELF, PETSC_ERR_ARG_OUTOFRANGE, "Only versions 1-4 are supported: %" PetscInt_FMT, kctx->version);
5543:     if (kctx->version == 1) {
5544:       rtol = PetscAbsReal(snes->norm - kctx->lresid_last) / kctx->norm_last;
5545:       stol = PetscPowReal(kctx->rtol_last, kctx->alpha2);
5546:       if (stol > kctx->threshold) rtol = PetscMax(rtol, stol);
5547:     } else if (kctx->version == 2) {
5548:       rtol = kctx->gamma * PetscPowReal(snes->norm / kctx->norm_last, kctx->alpha);
5549:       stol = kctx->gamma * PetscPowReal(kctx->rtol_last, kctx->alpha);
5550:       if (stol > kctx->threshold) rtol = PetscMax(rtol, stol);
5551:     } else if (kctx->version == 3) { /* contributed by Luis Chacon, June 2006. */
5552:       rtol = kctx->gamma * PetscPowReal(snes->norm / kctx->norm_last, kctx->alpha);
5553:       /* safeguard: avoid sharp decrease of rtol */
5554:       stol = kctx->gamma * PetscPowReal(kctx->rtol_last, kctx->alpha);
5555:       stol = PetscMax(rtol, stol);
5556:       rtol = PetscMin(kctx->rtol_0, stol);
5557:       /* safeguard: avoid oversolving */
5558:       stol = kctx->gamma * (kctx->norm_first * snes->rtol) / snes->norm;
5559:       stol = PetscMax(rtol, stol);
5560:       rtol = PetscMin(kctx->rtol_0, stol);
5561:     } else /* if (kctx->version == 4) */ {
5562:       /* H.-B. An et al. Journal of Computational and Applied Mathematics 200 (2007) 47-60 */
5563:       PetscReal ared = PetscAbsReal(kctx->norm_last - snes->norm);
5564:       PetscReal pred = PetscAbsReal(kctx->norm_last - kctx->lresid_last);
5565:       PetscReal rk   = ared / pred;
5566:       if (rk < kctx->v4_p1) rtol = 1. - 2. * kctx->v4_p1;
5567:       else if (rk < kctx->v4_p2) rtol = kctx->rtol_last;
5568:       else if (rk < kctx->v4_p3) rtol = kctx->v4_m1 * kctx->rtol_last;
5569:       else rtol = kctx->v4_m2 * kctx->rtol_last;

5571:       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;
5572:       kctx->rtol_last_2 = kctx->rtol_last;
5573:       kctx->rk_last_2   = kctx->rk_last;
5574:       kctx->rk_last     = rk;
5575:     }
5576:   }
5577:   /* safeguard: avoid rtol greater than rtol_max */
5578:   rtol = PetscMin(rtol, kctx->rtol_max);
5579:   PetscCall(KSPSetTolerances(ksp, rtol, PETSC_CURRENT, PETSC_CURRENT, PETSC_CURRENT));
5580:   PetscCall(PetscInfo(snes, "iter %" PetscInt_FMT ", Eisenstat-Walker (version %" PetscInt_FMT ") KSP rtol=%g\n", snes->iter, kctx->version, (double)rtol));
5581:   PetscFunctionReturn(PETSC_SUCCESS);
5582: }

5584: PetscErrorCode KSPPostSolve_SNESEW(KSP ksp, Vec b, Vec x, void *ctx)
5585: {
5586:   SNES       snes = (SNES)ctx;
5587:   SNESKSPEW *kctx = (SNESKSPEW *)snes->kspconvctx;
5588:   PCSide     pcside;
5589:   Vec        lres;

5591:   PetscFunctionBegin;
5592:   if (!snes->ksp_ewconv) PetscFunctionReturn(PETSC_SUCCESS);
5593:   PetscCall(KSPGetTolerances(ksp, &kctx->rtol_last, NULL, NULL, NULL));
5594:   kctx->norm_last = snes->norm;
5595:   if (kctx->version == 1 || kctx->version == 4) {
5596:     PC        pc;
5597:     PetscBool getRes;

5599:     PetscCall(KSPGetPC(ksp, &pc));
5600:     PetscCall(PetscObjectTypeCompare((PetscObject)pc, PCNONE, &getRes));
5601:     if (!getRes) {
5602:       KSPNormType normtype;

5604:       PetscCall(KSPGetNormType(ksp, &normtype));
5605:       getRes = (PetscBool)(normtype == KSP_NORM_UNPRECONDITIONED);
5606:     }
5607:     PetscCall(KSPGetPCSide(ksp, &pcside));
5608:     if (pcside == PC_RIGHT || getRes) { /* KSP residual is true linear residual */
5609:       PetscCall(KSPGetResidualNorm(ksp, &kctx->lresid_last));
5610:     } else {
5611:       /* KSP residual is preconditioned residual */
5612:       /* compute true linear residual norm */
5613:       Mat J;
5614:       PetscCall(KSPGetOperators(ksp, &J, NULL));
5615:       PetscCall(VecDuplicate(b, &lres));
5616:       PetscCall(MatMult(J, x, lres));
5617:       PetscCall(VecAYPX(lres, -1.0, b));
5618:       PetscCall(VecNorm(lres, NORM_2, &kctx->lresid_last));
5619:       PetscCall(VecDestroy(&lres));
5620:     }
5621:   }
5622:   PetscFunctionReturn(PETSC_SUCCESS);
5623: }

5625: /*@
5626:   SNESGetKSP - Returns the `KSP` context for a `SNES` solver.

5628:   Not Collective, but if `snes` is parallel, then `ksp` is parallel

5630:   Input Parameter:
5631: . snes - the `SNES` context

5633:   Output Parameter:
5634: . ksp - the `KSP` context

5636:   Level: beginner

5638:   Notes:
5639:   The user can then directly manipulate the `KSP` context to set various
5640:   options, etc.  Likewise, the user can then extract and manipulate the
5641:   `PC` contexts as well.

5643:   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.

5645: .seealso: [](ch_snes), `SNES`, `KSP`, `PC`, `KSPGetPC()`, `SNESCreate()`, `KSPCreate()`, `SNESSetKSP()`
5646: @*/
5647: PetscErrorCode SNESGetKSP(SNES snes, KSP *ksp)
5648: {
5649:   PetscFunctionBegin;
5651:   PetscAssertPointer(ksp, 2);

5653:   if (!snes->ksp) {
5654:     PetscCall(KSPCreate(PetscObjectComm((PetscObject)snes), &snes->ksp));
5655:     PetscCall(PetscObjectIncrementTabLevel((PetscObject)snes->ksp, (PetscObject)snes, 1));

5657:     PetscCall(KSPSetPreSolve(snes->ksp, KSPPreSolve_SNESEW, snes));
5658:     PetscCall(KSPSetPostSolve(snes->ksp, KSPPostSolve_SNESEW, snes));

5660:     PetscCall(KSPMonitorSetFromOptions(snes->ksp, "-snes_monitor_ksp", "snes_preconditioned_residual", snes));
5661:     PetscCall(PetscObjectSetOptions((PetscObject)snes->ksp, ((PetscObject)snes)->options));
5662:   }
5663:   *ksp = snes->ksp;
5664:   PetscFunctionReturn(PETSC_SUCCESS);
5665: }

5667: #include <petsc/private/dmimpl.h>
5668: /*@
5669:   SNESSetDM - Sets the `DM` that may be used by some `SNES` nonlinear solvers or their underlying preconditioners

5671:   Logically Collective

5673:   Input Parameters:
5674: + snes - the nonlinear solver context
5675: - dm   - the `DM`, cannot be `NULL`

5677:   Level: intermediate

5679:   Note:
5680:   A `DM` can only be used for solving one problem at a time because information about the problem is stored on the `DM`,
5681:   even when not using interfaces like `DMSNESSetFunction()`.  Use `DMClone()` to get a distinct `DM` when solving different
5682:   problems using the same function space.

5684: .seealso: [](ch_snes), `DM`, `SNES`, `SNESGetDM()`, `KSPSetDM()`, `KSPGetDM()`
5685: @*/
5686: PetscErrorCode SNESSetDM(SNES snes, DM dm)
5687: {
5688:   KSP    ksp;
5689:   DMSNES sdm;

5691:   PetscFunctionBegin;
5694:   PetscCall(PetscObjectReference((PetscObject)dm));
5695:   if (snes->dm) { /* Move the DMSNES context over to the new DM unless the new DM already has one */
5696:     if (snes->dm->dmsnes && !dm->dmsnes) {
5697:       PetscCall(DMCopyDMSNES(snes->dm, dm));
5698:       PetscCall(DMGetDMSNES(snes->dm, &sdm));
5699:       if (sdm->originaldm == snes->dm) sdm->originaldm = dm; /* Grant write privileges to the replacement DM */
5700:     }
5701:     PetscCall(DMCoarsenHookRemove(snes->dm, DMCoarsenHook_SNESVecSol, DMRestrictHook_SNESVecSol, snes));
5702:     PetscCall(DMDestroy(&snes->dm));
5703:   }
5704:   snes->dm     = dm;
5705:   snes->dmAuto = PETSC_FALSE;

5707:   PetscCall(SNESGetKSP(snes, &ksp));
5708:   PetscCall(KSPSetDM(ksp, dm));
5709:   PetscCall(KSPSetDMActive(ksp, PETSC_FALSE));
5710:   if (snes->npc) {
5711:     PetscCall(SNESSetDM(snes->npc, snes->dm));
5712:     PetscCall(SNESSetNPCSide(snes, snes->npcside));
5713:   }
5714:   PetscFunctionReturn(PETSC_SUCCESS);
5715: }

5717: /*@
5718:   SNESGetDM - Gets the `DM` that may be used by some `SNES` nonlinear solvers/preconditioners

5720:   Not Collective but `dm` obtained is parallel on `snes`

5722:   Input Parameter:
5723: . snes - the `SNES` context

5725:   Output Parameter:
5726: . dm - the `DM`

5728:   Level: intermediate

5730: .seealso: [](ch_snes), `DM`, `SNES`, `SNESSetDM()`, `KSPSetDM()`, `KSPGetDM()`
5731: @*/
5732: PetscErrorCode SNESGetDM(SNES snes, DM *dm)
5733: {
5734:   PetscFunctionBegin;
5736:   if (!snes->dm) {
5737:     PetscCall(DMShellCreate(PetscObjectComm((PetscObject)snes), &snes->dm));
5738:     snes->dmAuto = PETSC_TRUE;
5739:   }
5740:   *dm = snes->dm;
5741:   PetscFunctionReturn(PETSC_SUCCESS);
5742: }

5744: /*@
5745:   SNESSetNPC - Sets the nonlinear preconditioner to be used.

5747:   Collective

5749:   Input Parameters:
5750: + snes - iterative context obtained from `SNESCreate()`
5751: - npc  - the `SNES` nonlinear preconditioner object

5753:   Options Database Key:
5754: . -npc_snes_type <type> - set the type of the `SNES` to use as the nonlinear preconditioner

5756:   Level: developer

5758:   Notes:
5759:   This is rarely used, rather use `SNESGetNPC()` to retrieve the preconditioner and configure it using the API.

5761:   Only some `SNESType` can use a nonlinear preconditioner

5763: .seealso: [](ch_snes), `SNES`, `SNESNGS`, `SNESFAS`, `SNESGetNPC()`, `SNESHasNPC()`
5764: @*/
5765: PetscErrorCode SNESSetNPC(SNES snes, SNES npc)
5766: {
5767:   PetscFunctionBegin;
5770:   PetscCheckSameComm(snes, 1, npc, 2);
5771:   PetscCall(PetscObjectReference((PetscObject)npc));
5772:   PetscCall(SNESDestroy(&snes->npc));
5773:   snes->npc = npc;
5774:   PetscFunctionReturn(PETSC_SUCCESS);
5775: }

5777: /*@
5778:   SNESGetNPC - Gets a nonlinear preconditioning solver SNES` to be used to precondition the original nonlinear solver.

5780:   Not Collective; but any changes to the obtained the `pc` object must be applied collectively

5782:   Input Parameter:
5783: . snes - iterative context obtained from `SNESCreate()`

5785:   Output Parameter:
5786: . pc - the `SNES` preconditioner context

5788:   Options Database Key:
5789: . -npc_snes_type <type> - set the type of the `SNES` to use as the nonlinear preconditioner

5791:   Level: advanced

5793:   Notes:
5794:   If a `SNES` was previously set with `SNESSetNPC()` then that value is returned, otherwise a new `SNES` object is created that will
5795:   be used as the nonlinear preconditioner for the current `SNES`.

5797:   The (preconditioner) `SNES` returned automatically inherits the same nonlinear function and Jacobian supplied to the original
5798:   `SNES`. These may be overwritten if needed.

5800:   Use the options database prefixes `-npc_snes`, `-npc_ksp`, etc., to control the configuration of the nonlinear preconditioner

5802: .seealso: [](ch_snes), `SNESSetNPC()`, `SNESHasNPC()`, `SNES`, `SNESCreate()`
5803: @*/
5804: PetscErrorCode SNESGetNPC(SNES snes, SNES *pc)
5805: {
5806:   const char *optionsprefix;

5808:   PetscFunctionBegin;
5810:   PetscAssertPointer(pc, 2);
5811:   if (!snes->npc) {
5812:     void *ctx;

5814:     PetscCall(SNESCreate(PetscObjectComm((PetscObject)snes), &snes->npc));
5815:     PetscCall(PetscObjectIncrementTabLevel((PetscObject)snes->npc, (PetscObject)snes, 1));
5816:     PetscCall(SNESGetOptionsPrefix(snes, &optionsprefix));
5817:     PetscCall(SNESSetOptionsPrefix(snes->npc, optionsprefix));
5818:     PetscCall(SNESAppendOptionsPrefix(snes->npc, "npc_"));
5819:     if (snes->ops->usercompute) {
5820:       PetscCall(SNESSetComputeApplicationContext(snes, snes->ops->usercompute, snes->ops->ctxdestroy));
5821:     } else {
5822:       PetscCall(SNESGetApplicationContext(snes, &ctx));
5823:       PetscCall(SNESSetApplicationContext(snes->npc, ctx));
5824:     }
5825:     PetscCall(SNESSetCountersReset(snes->npc, PETSC_FALSE));
5826:   }
5827:   *pc = snes->npc;
5828:   PetscFunctionReturn(PETSC_SUCCESS);
5829: }

5831: /*@
5832:   SNESHasNPC - Returns whether a nonlinear preconditioner is associated with the given `SNES`

5834:   Not Collective

5836:   Input Parameter:
5837: . snes - iterative context obtained from `SNESCreate()`

5839:   Output Parameter:
5840: . has_npc - whether the `SNES` has a nonlinear preconditioner or not

5842:   Level: developer

5844: .seealso: [](ch_snes), `SNESSetNPC()`, `SNESGetNPC()`
5845: @*/
5846: PetscErrorCode SNESHasNPC(SNES snes, PetscBool *has_npc)
5847: {
5848:   PetscFunctionBegin;
5850:   PetscAssertPointer(has_npc, 2);
5851:   *has_npc = snes->npc ? PETSC_TRUE : PETSC_FALSE;
5852:   PetscFunctionReturn(PETSC_SUCCESS);
5853: }

5855: /*@
5856:   SNESSetNPCSide - Sets the nonlinear preconditioning side used by the nonlinear preconditioner inside `SNES`.

5858:   Logically Collective

5860:   Input Parameter:
5861: . snes - iterative context obtained from `SNESCreate()`

5863:   Output Parameter:
5864: . side - the preconditioning side, where side is one of
5865: .vb
5866:       PC_LEFT  - left preconditioning
5867:       PC_RIGHT - right preconditioning (default for most nonlinear solvers)
5868: .ve

5870:   Options Database Key:
5871: . -snes_npc_side <right,left> - nonlinear preconditioner side

5873:   Level: intermediate

5875:   Note:
5876:   `SNESNRICHARDSON` and `SNESNCG` only support left preconditioning.

5878: .seealso: [](ch_snes), `SNES`, `SNESGetNPC()`, `SNESNRICHARDSON`, `SNESNCG`, `SNESType`, `SNESGetNPCSide()`, `KSPSetPCSide()`, `PC_LEFT`, `PC_RIGHT`, `PCSide`
5879: @*/
5880: PetscErrorCode SNESSetNPCSide(SNES snes, PCSide side)
5881: {
5882:   PetscFunctionBegin;
5885:   if (side == PC_SIDE_DEFAULT) side = PC_RIGHT;
5886:   PetscCheck((side == PC_LEFT) || (side == PC_RIGHT), PetscObjectComm((PetscObject)snes), PETSC_ERR_ARG_WRONG, "Only PC_LEFT and PC_RIGHT are supported");
5887:   snes->npcside = side;
5888:   PetscFunctionReturn(PETSC_SUCCESS);
5889: }

5891: /*@
5892:   SNESGetNPCSide - Gets the preconditioning side used by the nonlinear preconditioner inside `SNES`.

5894:   Not Collective

5896:   Input Parameter:
5897: . snes - iterative context obtained from `SNESCreate()`

5899:   Output Parameter:
5900: . side - the preconditioning side, where side is one of
5901: .vb
5902:       `PC_LEFT` - left preconditioning
5903:       `PC_RIGHT` - right preconditioning (default for most nonlinear solvers)
5904: .ve

5906:   Level: intermediate

5908: .seealso: [](ch_snes), `SNES`, `SNESGetNPC()`, `SNESSetNPCSide()`, `KSPGetPCSide()`, `PC_LEFT`, `PC_RIGHT`, `PCSide`
5909: @*/
5910: PetscErrorCode SNESGetNPCSide(SNES snes, PCSide *side)
5911: {
5912:   PetscFunctionBegin;
5914:   PetscAssertPointer(side, 2);
5915:   *side = snes->npcside;
5916:   PetscFunctionReturn(PETSC_SUCCESS);
5917: }

5919: /*@
5920:   SNESSetLineSearch - Sets the `SNESLineSearch` to be used for a given `SNES`

5922:   Collective

5924:   Input Parameters:
5925: + snes       - iterative context obtained from `SNESCreate()`
5926: - linesearch - the linesearch object

5928:   Level: developer

5930:   Note:
5931:   This is almost never used, rather one uses `SNESGetLineSearch()` to retrieve the line search and set options on it
5932:   to configure it using the API).

5934: .seealso: [](ch_snes), `SNES`, `SNESLineSearch`, `SNESGetLineSearch()`
5935: @*/
5936: PetscErrorCode SNESSetLineSearch(SNES snes, SNESLineSearch linesearch)
5937: {
5938:   PetscFunctionBegin;
5941:   PetscCheckSameComm(snes, 1, linesearch, 2);
5942:   PetscCall(PetscObjectReference((PetscObject)linesearch));
5943:   PetscCall(SNESLineSearchDestroy(&snes->linesearch));

5945:   snes->linesearch = linesearch;
5946:   PetscFunctionReturn(PETSC_SUCCESS);
5947: }

5949: /*@
5950:   SNESGetLineSearch - Returns the line search associated with the `SNES`.

5952:   Not Collective

5954:   Input Parameter:
5955: . snes - iterative context obtained from `SNESCreate()`

5957:   Output Parameter:
5958: . linesearch - linesearch context

5960:   Level: beginner

5962:   Notes:
5963:   It creates a default line search instance which can be configured as needed in case it has not been already set with `SNESSetLineSearch()`.

5965:   You can also use the options database keys `-snes_linesearch_*` to configure the line search. See `SNESLineSearchSetFromOptions()` for the possible options.

5967: .seealso: [](ch_snes), `SNESLineSearch`, `SNESSetLineSearch()`, `SNESLineSearchCreate()`, `SNESLineSearchSetFromOptions()`
5968: @*/
5969: PetscErrorCode SNESGetLineSearch(SNES snes, SNESLineSearch *linesearch)
5970: {
5971:   const char *optionsprefix;

5973:   PetscFunctionBegin;
5975:   PetscAssertPointer(linesearch, 2);
5976:   if (!snes->linesearch) {
5977:     PetscCall(SNESGetOptionsPrefix(snes, &optionsprefix));
5978:     PetscCall(SNESLineSearchCreate(PetscObjectComm((PetscObject)snes), &snes->linesearch));
5979:     PetscCall(SNESLineSearchSetSNES(snes->linesearch, snes));
5980:     PetscCall(SNESLineSearchAppendOptionsPrefix(snes->linesearch, optionsprefix));
5981:     PetscCall(PetscObjectIncrementTabLevel((PetscObject)snes->linesearch, (PetscObject)snes, 1));
5982:   }
5983:   *linesearch = snes->linesearch;
5984:   PetscFunctionReturn(PETSC_SUCCESS);
5985: }