Actual source code: linesearch.c

  1: #include <petsc/private/linesearchimpl.h>

  3: PetscBool         SNESLineSearchRegisterAllCalled = PETSC_FALSE;
  4: PetscFunctionList SNESLineSearchList              = NULL;

  6: PetscClassId  SNESLINESEARCH_CLASSID;
  7: PetscLogEvent SNESLINESEARCH_Apply;

  9: /*@
 10:   SNESLineSearchMonitorCancel - Clears all the monitor functions for a `SNESLineSearch` object.

 12:   Logically Collective

 14:   Input Parameter:
 15: . ls - the `SNESLineSearch` context

 17:   Options Database Key:
 18: . -snes_linesearch_monitor_cancel - cancels all monitors that have been hardwired
 19:     into a code by calls to `SNESLineSearchMonitorSet()`, but does not cancel those
 20:     set via the options database

 22:   Level: advanced

 24:   Notes:
 25:   There is no way to clear one specific monitor from a `SNESLineSearch` object.

 27:   This does not clear the monitor set with `SNESLineSearchSetDefaultMonitor()` use `SNESLineSearchSetDefaultMonitor`(`ls`,`NULL`) to cancel it
 28:   that one.

 30: .seealso: [](ch_snes), `SNES`, `SNESLineSearch`, `SNESGetLineSearch()`, `SNESLineSearchMonitorDefault()`, `SNESLineSearchMonitorSet()`
 31: @*/
 32: PetscErrorCode SNESLineSearchMonitorCancel(SNESLineSearch ls)
 33: {
 34:   PetscInt i;

 36:   PetscFunctionBegin;
 38:   for (i = 0; i < ls->numbermonitors; i++) {
 39:     if (ls->monitordestroy[i]) PetscCall((*ls->monitordestroy[i])(&ls->monitorcontext[i]));
 40:   }
 41:   ls->numbermonitors = 0;
 42:   PetscFunctionReturn(PETSC_SUCCESS);
 43: }

 45: /*@
 46:   SNESLineSearchMonitor - runs the user provided monitor routines, if they exist

 48:   Collective

 50:   Input Parameter:
 51: . ls - the linesearch object

 53:   Level: developer

 55:   Note:
 56:   This routine is called by the `SNESLineSearch` implementations.
 57:   It does not typically need to be called by the user.

 59: .seealso: [](ch_snes), `SNES`, `SNESLineSearch`, `SNESGetLineSearch()`, `SNESLineSearchMonitorSet()`
 60: @*/
 61: PetscErrorCode SNESLineSearchMonitor(SNESLineSearch ls)
 62: {
 63:   PetscInt i, n = ls->numbermonitors;

 65:   PetscFunctionBegin;
 66:   for (i = 0; i < n; i++) PetscCall((*ls->monitorftns[i])(ls, ls->monitorcontext[i]));
 67:   PetscFunctionReturn(PETSC_SUCCESS);
 68: }

 70: /*@C
 71:   SNESLineSearchMonitorSet - Sets an ADDITIONAL function that is to be used at every
 72:   iteration of the nonlinear solver to display the iteration's
 73:   progress.

 75:   Logically Collective

 77:   Input Parameters:
 78: + ls             - the `SNESLineSearch` context
 79: . f              - the monitor function
 80: . mctx           - [optional] user-defined context for private data for the monitor routine (use `NULL` if no context is desired)
 81: - monitordestroy - [optional] routine that frees monitor context (may be `NULL`), see `PetscCtxDestroyFn` for the calling sequence

 83:   Calling sequence of `f`:
 84: + ls   - the `SNESLineSearch` context
 85: - mctx - [optional] user-defined context for private data for the monitor routine

 87:   Level: intermediate

 89:   Note:
 90:   Several different monitoring routines may be set by calling
 91:   `SNESLineSearchMonitorSet()` multiple times; all will be called in the
 92:   order in which they were set.

 94:   Fortran Note:
 95:   Only a single monitor function can be set for each `SNESLineSearch` object

 97: .seealso: [](ch_snes), `SNES`, `SNESLineSearch`, `SNESGetLineSearch()`, `SNESLineSearchMonitorDefault()`, `SNESLineSearchMonitorCancel()`, `PetscCtxDestroyFn`
 98: @*/
 99: PetscErrorCode SNESLineSearchMonitorSet(SNESLineSearch ls, PetscErrorCode (*f)(SNESLineSearch ls, void *mctx), void *mctx, PetscCtxDestroyFn *monitordestroy)
100: {
101:   PetscFunctionBegin;
103:   for (PetscInt i = 0; i < ls->numbermonitors; i++) {
104:     PetscBool identical;

106:     PetscCall(PetscMonitorCompare((PetscErrorCode (*)(void))(PetscVoidFn *)f, mctx, monitordestroy, (PetscErrorCode (*)(void))(PetscVoidFn *)ls->monitorftns[i], ls->monitorcontext[i], ls->monitordestroy[i], &identical));
107:     if (identical) PetscFunctionReturn(PETSC_SUCCESS);
108:   }
109:   PetscCheck(ls->numbermonitors < MAXSNESLSMONITORS, PETSC_COMM_SELF, PETSC_ERR_ARG_OUTOFRANGE, "Too many monitors set");
110:   ls->monitorftns[ls->numbermonitors]      = f;
111:   ls->monitordestroy[ls->numbermonitors]   = monitordestroy;
112:   ls->monitorcontext[ls->numbermonitors++] = mctx;
113:   PetscFunctionReturn(PETSC_SUCCESS);
114: }

116: /*@C
117:   SNESLineSearchMonitorSolutionUpdate - Monitors each update of the function value the linesearch tries

119:   Collective

121:   Input Parameters:
122: + ls - the `SNESLineSearch` object
123: - vf - the context for the monitor, in this case it is an `PetscViewerAndFormat`

125:   Options Database Key:
126: . -snes_linesearch_monitor_solution_update [viewer:filename:format] - view each update tried by line search routine

128:   Level: developer

130:   This is not normally called directly but is passed to `SNESLineSearchMonitorSet()`

132: .seealso: [](ch_snes), `SNES`, `SNESLineSearch`, `SNESGetLineSearch()`, `SNESLineSearchMonitorSet()`, `SNESMonitorSolution()`
133: @*/
134: PetscErrorCode SNESLineSearchMonitorSolutionUpdate(SNESLineSearch ls, PetscViewerAndFormat *vf)
135: {
136:   PetscViewer viewer = vf->viewer;
137:   Vec         Y, W, G;

139:   PetscFunctionBegin;
140:   PetscCall(SNESLineSearchGetVecs(ls, NULL, NULL, &Y, &W, &G));
141:   PetscCall(PetscViewerPushFormat(viewer, vf->format));
142:   PetscCall(PetscViewerASCIIPrintf(viewer, "LineSearch attempted update to solution \n"));
143:   PetscCall(VecView(Y, viewer));
144:   PetscCall(PetscViewerASCIIPrintf(viewer, "LineSearch attempted new solution \n"));
145:   PetscCall(VecView(W, viewer));
146:   PetscCall(PetscViewerASCIIPrintf(viewer, "LineSearch attempted updated function value\n"));
147:   PetscCall(VecView(G, viewer));
148:   PetscCall(PetscViewerPopFormat(viewer));
149:   PetscFunctionReturn(PETSC_SUCCESS);
150: }

152: /*@
153:   SNESLineSearchCreate - Creates a `SNESLineSearch` context.

155:   Logically Collective

157:   Input Parameter:
158: . comm - MPI communicator for the line search (typically from the associated `SNES` context).

160:   Output Parameter:
161: . outlinesearch - the new line search context

163:   Level: developer

165:   Note:
166:   The preferred calling sequence is to use `SNESGetLineSearch()` to acquire the `SNESLineSearch` instance
167:   already associated with the `SNES`.

169: .seealso: [](ch_snes), `SNES`, `SNESLineSearch`, `LineSearchDestroy()`, `SNESGetLineSearch()`
170: @*/
171: PetscErrorCode SNESLineSearchCreate(MPI_Comm comm, SNESLineSearch *outlinesearch)
172: {
173:   SNESLineSearch linesearch;

175:   PetscFunctionBegin;
176:   PetscAssertPointer(outlinesearch, 2);
177:   PetscCall(SNESInitializePackage());

179:   PetscCall(PetscHeaderCreate(linesearch, SNESLINESEARCH_CLASSID, "SNESLineSearch", "Linesearch", "SNESLineSearch", comm, SNESLineSearchDestroy, SNESLineSearchView));
180:   linesearch->vec_sol_new  = NULL;
181:   linesearch->vec_func_new = NULL;
182:   linesearch->vec_sol      = NULL;
183:   linesearch->vec_func     = NULL;
184:   linesearch->vec_update   = NULL;

186:   linesearch->lambda       = 1.0;
187:   linesearch->fnorm        = 1.0;
188:   linesearch->ynorm        = 1.0;
189:   linesearch->xnorm        = 1.0;
190:   linesearch->result       = SNES_LINESEARCH_SUCCEEDED;
191:   linesearch->norms        = PETSC_TRUE;
192:   linesearch->keeplambda   = PETSC_FALSE;
193:   linesearch->damping      = 1.0;
194:   linesearch->maxlambda    = 1.0;
195:   linesearch->minlambda    = 1e-12;
196:   linesearch->rtol         = 1e-8;
197:   linesearch->atol         = 1e-15;
198:   linesearch->ltol         = 1e-8;
199:   linesearch->precheckctx  = NULL;
200:   linesearch->postcheckctx = NULL;
201:   linesearch->max_it       = 1;
202:   linesearch->setupcalled  = PETSC_FALSE;
203:   linesearch->monitor      = NULL;
204:   *outlinesearch           = linesearch;
205:   PetscFunctionReturn(PETSC_SUCCESS);
206: }

208: /*@
209:   SNESLineSearchSetUp - Prepares the line search for being applied by allocating
210:   any required vectors.

212:   Collective

214:   Input Parameter:
215: . linesearch - The `SNESLineSearch` instance.

217:   Level: advanced

219:   Note:
220:   For most cases, this needn't be called by users or outside of `SNESLineSearchApply()`.
221:   The only current case where this is called outside of this is for the VI
222:   solvers, which modify the solution and work vectors before the first call
223:   of `SNESLineSearchApply()`, requiring the `SNESLineSearch` work vectors to be
224:   allocated upfront.

226: .seealso: [](ch_snes), `SNES`, `SNESLineSearch`, `SNESGetLineSearch()`, `SNESLineSearchReset()`
227: @*/
228: PetscErrorCode SNESLineSearchSetUp(SNESLineSearch linesearch)
229: {
230:   PetscFunctionBegin;
231:   if (!((PetscObject)linesearch)->type_name) PetscCall(SNESLineSearchSetType(linesearch, SNESLINESEARCHBASIC));
232:   if (!linesearch->setupcalled) {
233:     if (!linesearch->vec_sol_new) PetscCall(VecDuplicate(linesearch->vec_sol, &linesearch->vec_sol_new));
234:     if (!linesearch->vec_func_new) PetscCall(VecDuplicate(linesearch->vec_sol, &linesearch->vec_func_new));
235:     PetscTryTypeMethod(linesearch, setup);
236:     if (!linesearch->ops->snesfunc) PetscCall(SNESLineSearchSetFunction(linesearch, SNESComputeFunction));
237:     linesearch->lambda      = linesearch->damping;
238:     linesearch->setupcalled = PETSC_TRUE;
239:   }
240:   PetscFunctionReturn(PETSC_SUCCESS);
241: }

243: /*@
244:   SNESLineSearchReset - Undoes the `SNESLineSearchSetUp()` and deletes any `Vec`s or `Mat`s allocated by the line search.

246:   Collective

248:   Input Parameter:
249: . linesearch - The `SNESLineSearch` instance.

251:   Level: developer

253:   Note:
254:   Usually only called by `SNESReset()`

256: .seealso: [](ch_snes), `SNES`, `SNESLineSearch`, `SNESGetLineSearch()`, `SNESLineSearchSetUp()`
257: @*/
258: PetscErrorCode SNESLineSearchReset(SNESLineSearch linesearch)
259: {
260:   PetscFunctionBegin;
261:   PetscTryTypeMethod(linesearch, reset);

263:   PetscCall(VecDestroy(&linesearch->vec_sol_new));
264:   PetscCall(VecDestroy(&linesearch->vec_func_new));

266:   PetscCall(VecDestroyVecs(linesearch->nwork, &linesearch->work));

268:   linesearch->nwork       = 0;
269:   linesearch->setupcalled = PETSC_FALSE;
270:   PetscFunctionReturn(PETSC_SUCCESS);
271: }

273: /*@C
274:   SNESLineSearchSetFunction - Sets the function evaluation used by the `SNES` line search
275:   `

277:   Input Parameters:
278: + linesearch - the `SNESLineSearch` context
279: - func       - function evaluation routine, this is usually the function provided with `SNESSetFunction()`

281:   Calling sequence of `func`:
282: + snes - the `SNES` with which the `SNESLineSearch` context is associated with
283: . x    - the input vector
284: - f    - the computed value of the function

286:   Level: developer

288:   Note:
289:   By default the `SNESLineSearch` uses the function provided by `SNESSetFunction()` so this is rarely needed

291: .seealso: [](ch_snes), `SNES`, `SNESLineSearch`, `SNESGetLineSearch()`, `SNESSetFunction()`
292: @*/
293: PetscErrorCode SNESLineSearchSetFunction(SNESLineSearch linesearch, PetscErrorCode (*func)(SNES snes, Vec x, Vec f))
294: {
295:   PetscFunctionBegin;
297:   linesearch->ops->snesfunc = func;
298:   PetscFunctionReturn(PETSC_SUCCESS);
299: }

301: /*@C
302:   SNESLineSearchSetPreCheck - Sets a function that is called after the initial search direction has been computed but
303:   before the line search routine has been applied. Allows adjusting the result of (usually a linear solve) that
304:   determined the search direction.

306:   Logically Collective

308:   Input Parameters:
309: + linesearch - the `SNESLineSearch` context
310: . func       - [optional] function evaluation routine
311: - ctx        - [optional] user-defined context for private data for the function evaluation routine (may be `NULL`)

313:   Calling sequence of `func`:
314: + ls        - the `SNESLineSearch` context
315: . x         - the current solution
316: . d         - the current search direction
317: . changed_d - indicates if the search direction has been changed
318: - ctx       - the context passed to `SNESLineSearchSetPreCheck()`

320:   Level: intermediate

322:   Note:
323:   Use `SNESLineSearchSetPostCheck()` to change the step after the line search is complete.

325:   Use `SNESVISetVariableBounds()` and `SNESVISetComputeVariableBounds()` to cause `SNES` to automatically control the ranges of variables allowed.

327: .seealso: [](ch_snes), `SNES`, `SNESGetLineSearch()`, `SNESLineSearchPreCheck()`, `SNESLineSearchSetPostCheck()`, `SNESLineSearchGetPostCheck()`, `SNESLineSearchGetPreCheck()`,
328:           `SNESVISetVariableBounds()`, `SNESVISetComputeVariableBounds()`, `SNESSetFunctionDomainError()`, `SNESSetJacobianDomainError()`

330: @*/
331: PetscErrorCode SNESLineSearchSetPreCheck(SNESLineSearch linesearch, PetscErrorCode (*func)(SNESLineSearch ls, Vec x, Vec d, PetscBool *changed_d, void *ctx), void *ctx)
332: {
333:   PetscFunctionBegin;
335:   if (func) linesearch->ops->precheck = func;
336:   if (ctx) linesearch->precheckctx = ctx;
337:   PetscFunctionReturn(PETSC_SUCCESS);
338: }

340: /*@C
341:   SNESLineSearchGetPreCheck - Gets the pre-check function for the line search routine.

343:   Input Parameter:
344: . linesearch - the `SNESLineSearch` context

346:   Output Parameters:
347: + func - [optional] function evaluation routine,  for calling sequence see `SNESLineSearchSetPreCheck()`
348: - ctx  - [optional] user-defined context for private data for the function evaluation routine (may be `NULL`)

350:   Level: intermediate

352: .seealso: [](ch_snes), `SNES`, `SNESLineSearch`, `SNESGetLineSearch()`, `SNESLineSearchPreCheck()`, `SNESLineSearchGetPostCheck()`, `SNESLineSearchSetPreCheck()`, `SNESLineSearchSetPostCheck()`
353: @*/
354: PetscErrorCode SNESLineSearchGetPreCheck(SNESLineSearch linesearch, PetscErrorCode (**func)(SNESLineSearch, Vec, Vec, PetscBool *, void *), void **ctx)
355: {
356:   PetscFunctionBegin;
358:   if (func) *func = linesearch->ops->precheck;
359:   if (ctx) *ctx = linesearch->precheckctx;
360:   PetscFunctionReturn(PETSC_SUCCESS);
361: }

363: /*@C
364:   SNESLineSearchSetPostCheck - Sets a user function that is called after the line search has been applied to determine the step
365:   direction and length. Allows the user a chance to change or override the decision of the line search routine

367:   Logically Collective

369:   Input Parameters:
370: + linesearch - the `SNESLineSearch` context
371: . func       - [optional] function evaluation routine
372: - ctx        - [optional] user-defined context for private data for the function evaluation routine (may be `NULL`)

374:   Calling sequence of `func`:
375: + ls        - the `SNESLineSearch` context
376: . x         - the current solution
377: . d         - the current search direction
378: . w         - $ w = x + lambda*d $ for some lambda
379: . changed_d - indicates if the search direction `d` has been changed
380: . changed_w - indicates `w` has been changed
381: - ctx       - the context passed to `SNESLineSearchSetPreCheck()`

383:   Level: intermediate

385:   Notes:
386:   Use `SNESLineSearchSetPreCheck()` to change the step before the line search is completed.
387:   The calling sequence of the callback does not contain the current scaling factor. To access the value, use `SNESLineSearchGetLambda()`.

389:   Use `SNESVISetVariableBounds()` and `SNESVISetComputeVariableBounds()` to cause `SNES` to automatically control the ranges of variables allowed.

391: .seealso: [](ch_snes), `SNES`, `SNESLineSearch`, `SNESGetLineSearch()`, `SNESLineSearchPostCheck()`, `SNESLineSearchSetPreCheck()`, `SNESLineSearchGetPreCheck()`, `SNESLineSearchGetPostCheck()`,
392:           `SNESVISetVariableBounds()`, `SNESVISetComputeVariableBounds()`, `SNESSetFunctionDomainError()`, `SNESSetJacobianDomainError()`
393: @*/
394: PetscErrorCode SNESLineSearchSetPostCheck(SNESLineSearch linesearch, PetscErrorCode (*func)(SNESLineSearch ls, Vec x, Vec d, Vec w, PetscBool *changed_d, PetscBool *changed_w, void *ctx), void *ctx)
395: {
396:   PetscFunctionBegin;
398:   if (func) linesearch->ops->postcheck = func;
399:   if (ctx) linesearch->postcheckctx = ctx;
400:   PetscFunctionReturn(PETSC_SUCCESS);
401: }

403: /*@C
404:   SNESLineSearchGetPostCheck - Gets the post-check function for the line search routine.

406:   Input Parameter:
407: . linesearch - the `SNESLineSearch` context

409:   Output Parameters:
410: + func - [optional] function evaluation routine, see for the calling sequence `SNESLineSearchSetPostCheck()`
411: - ctx  - [optional] user-defined context for private data for the function evaluation routine (may be `NULL`)

413:   Level: intermediate

415: .seealso: [](ch_snes), `SNES`, `SNESLineSearch`, `SNESGetLineSearch()`, `SNESLineSearchGetPreCheck()`, `SNESLineSearchSetPostCheck()`, `SNESLineSearchPostCheck()`, `SNESLineSearchSetPreCheck()`
416: @*/
417: PetscErrorCode SNESLineSearchGetPostCheck(SNESLineSearch linesearch, PetscErrorCode (**func)(SNESLineSearch, Vec, Vec, Vec, PetscBool *, PetscBool *, void *), void **ctx)
418: {
419:   PetscFunctionBegin;
421:   if (func) *func = linesearch->ops->postcheck;
422:   if (ctx) *ctx = linesearch->postcheckctx;
423:   PetscFunctionReturn(PETSC_SUCCESS);
424: }

426: /*@
427:   SNESLineSearchPreCheck - Prepares the line search for being applied.

429:   Logically Collective

431:   Input Parameters:
432: + linesearch - The linesearch instance.
433: . X          - The current solution
434: - Y          - The step direction

436:   Output Parameter:
437: . changed - Indicator that the precheck routine has changed `Y`

439:   Level: advanced

441:   Note:
442:   This calls any function provided with `SNESLineSearchSetPreCheck()` and is called automatically inside the line search routines

444:   Developer Note:
445:   The use of `PetscObjectGetState()` would eliminate the need for the `changed` argument to be provided

447: .seealso: [](ch_snes), `SNES`, `SNESLineSearch`, `SNESGetLineSearch()`, `SNESLineSearchPostCheck()`, `SNESLineSearchSetPreCheck()`, `SNESLineSearchGetPreCheck()`, `SNESLineSearchSetPostCheck()`,
448:           `SNESLineSearchGetPostCheck()`
449: @*/
450: PetscErrorCode SNESLineSearchPreCheck(SNESLineSearch linesearch, Vec X, Vec Y, PetscBool *changed)
451: {
452:   PetscFunctionBegin;
453:   *changed = PETSC_FALSE;
454:   if (linesearch->ops->precheck) {
455:     PetscUseTypeMethod(linesearch, precheck, X, Y, changed, linesearch->precheckctx);
457:   }
458:   PetscFunctionReturn(PETSC_SUCCESS);
459: }

461: /*@
462:   SNESLineSearchPostCheck - Hook to modify step direction or updated solution after a successful linesearch

464:   Logically Collective

466:   Input Parameters:
467: + linesearch - The line search context
468: . X          - The last solution
469: . Y          - The step direction
470: - W          - The updated solution, `W = X - lambda * Y` for some lambda

472:   Output Parameters:
473: + changed_Y - Indicator if the direction `Y` has been changed.
474: - changed_W - Indicator if the new candidate solution `W` has been changed.

476:   Level: developer

478:   Note:
479:   This calls any function provided with `SNESLineSearchSetPostCheck()` and is called automatically inside the line search routines

481:   Developer Note:
482:   The use of `PetscObjectGetState()` would eliminate the need for the `changed_Y` and `changed_W` arguments to be provided

484: .seealso: [](ch_snes), `SNES`, `SNESGetLineSearch()`, `SNESLineSearchPreCheck()`, `SNESLineSearchSetPostCheck()`, `SNESLineSearchGetPostCheck()`, `SNESLineSearchSetPrecheck()`, `SNESLineSearchGetPrecheck()`
485: @*/
486: PetscErrorCode SNESLineSearchPostCheck(SNESLineSearch linesearch, Vec X, Vec Y, Vec W, PetscBool *changed_Y, PetscBool *changed_W)
487: {
488:   PetscFunctionBegin;
489:   *changed_Y = PETSC_FALSE;
490:   *changed_W = PETSC_FALSE;
491:   if (linesearch->ops->postcheck) {
492:     PetscUseTypeMethod(linesearch, postcheck, X, Y, W, changed_Y, changed_W, linesearch->postcheckctx);
495:   }
496:   PetscFunctionReturn(PETSC_SUCCESS);
497: }

499: /*@C
500:   SNESLineSearchPreCheckPicard - Implements a correction that is sometimes useful to improve the convergence rate of Picard iteration {cite}`hindmarsh1996time`

502:   Logically Collective

504:   Input Parameters:
505: + linesearch - the line search context
506: . X          - base state for this step
507: - ctx        - context for this function

509:   Input/Output Parameter:
510: . Y - correction, possibly modified

512:   Output Parameter:
513: . changed - flag indicating that `Y` was modified

515:   Options Database Keys:
516: + -snes_linesearch_precheck_picard       - activate this routine
517: - -snes_linesearch_precheck_picard_angle - angle

519:   Level: advanced

521:   Notes:
522:   This function should be passed to `SNESLineSearchSetPreCheck()`

524:   The justification for this method involves the linear convergence of a Picard iteration
525:   so the Picard linearization should be provided in place of the "Jacobian"  {cite}`hindmarsh1996time`. This correction
526:   is generally not useful when using a Newton linearization.

528:   Developer Note:
529:   The use of `PetscObjectGetState()` would eliminate the need for the `changed` argument to be provided

531: .seealso: [](ch_snes), `SNES`, `SNESLineSearch`, `SNESSetPicard()`, `SNESGetLineSearch()`, `SNESLineSearchSetPreCheck()`, `SNESLineSearchSetPostCheck()`
532: @*/
533: PetscErrorCode SNESLineSearchPreCheckPicard(SNESLineSearch linesearch, Vec X, Vec Y, PetscBool *changed, void *ctx)
534: {
535:   PetscReal   angle = *(PetscReal *)linesearch->precheckctx;
536:   Vec         Ylast;
537:   PetscScalar dot;
538:   PetscInt    iter;
539:   PetscReal   ynorm, ylastnorm, theta, angle_radians;
540:   SNES        snes;

542:   PetscFunctionBegin;
543:   PetscCall(SNESLineSearchGetSNES(linesearch, &snes));
544:   PetscCall(PetscObjectQuery((PetscObject)snes, "SNESLineSearchPreCheckPicard_Ylast", (PetscObject *)&Ylast));
545:   if (!Ylast) {
546:     PetscCall(VecDuplicate(Y, &Ylast));
547:     PetscCall(PetscObjectCompose((PetscObject)snes, "SNESLineSearchPreCheckPicard_Ylast", (PetscObject)Ylast));
548:     PetscCall(PetscObjectDereference((PetscObject)Ylast));
549:   }
550:   PetscCall(SNESGetIterationNumber(snes, &iter));
551:   if (iter < 2) {
552:     PetscCall(VecCopy(Y, Ylast));
553:     *changed = PETSC_FALSE;
554:     PetscFunctionReturn(PETSC_SUCCESS);
555:   }

557:   PetscCall(VecDot(Y, Ylast, &dot));
558:   PetscCall(VecNorm(Y, NORM_2, &ynorm));
559:   PetscCall(VecNorm(Ylast, NORM_2, &ylastnorm));
560:   if (ynorm == 0. || ylastnorm == 0.) {
561:     *changed = PETSC_FALSE;
562:     PetscFunctionReturn(PETSC_SUCCESS);
563:   }
564:   /* Compute the angle between the vectors Y and Ylast, clip to keep inside the domain of acos() */
565:   theta         = PetscAcosReal((PetscReal)PetscClipInterval(PetscAbsScalar(dot) / (ynorm * ylastnorm), -1.0, 1.0));
566:   angle_radians = angle * PETSC_PI / 180.;
567:   if (PetscAbsReal(theta) < angle_radians || PetscAbsReal(theta - PETSC_PI) < angle_radians) {
568:     /* Modify the step Y */
569:     PetscReal alpha, ydiffnorm;
570:     PetscCall(VecAXPY(Ylast, -1.0, Y));
571:     PetscCall(VecNorm(Ylast, NORM_2, &ydiffnorm));
572:     alpha = (ydiffnorm > .001 * ylastnorm) ? ylastnorm / ydiffnorm : 1000.0;
573:     PetscCall(VecCopy(Y, Ylast));
574:     PetscCall(VecScale(Y, alpha));
575:     PetscCall(PetscInfo(snes, "Angle %14.12e degrees less than threshold %14.12e, corrected step by alpha=%14.12e\n", (double)(theta * 180 / PETSC_PI), (double)angle, (double)alpha));
576:     *changed = PETSC_TRUE;
577:   } else {
578:     PetscCall(PetscInfo(snes, "Angle %14.12e degrees exceeds threshold %14.12e, no correction applied\n", (double)(theta * 180 / PETSC_PI), (double)angle));
579:     PetscCall(VecCopy(Y, Ylast));
580:     *changed = PETSC_FALSE;
581:   }
582:   PetscFunctionReturn(PETSC_SUCCESS);
583: }

585: /*@
586:   SNESLineSearchApply - Computes the line-search update.

588:   Collective

590:   Input Parameter:
591: . linesearch - The line search context

593:   Input/Output Parameters:
594: + X     - The current solution, on output the new solution
595: . F     - The current function value, on output the new function value at the solution value `X`
596: . fnorm - The current norm of `F`, on output the new norm of `F`
597: - Y     - The current search direction, on output the direction determined by the linesearch, i.e. `Xnew = Xold - lambda*Y`

599:   Options Database Keys:
600: + -snes_linesearch_type                - basic (or equivalently none), bt, secant, cp, nleqerr, bisection, shell
601: . -snes_linesearch_monitor [:filename] - Print progress of line searches
602: . -snes_linesearch_damping             - The linesearch damping parameter, default is 1.0 (no damping)
603: . -snes_linesearch_norms               - Turn on/off the linesearch norms computation (SNESLineSearchSetComputeNorms())
604: . -snes_linesearch_keeplambda          - Keep the previous `lambda` as the initial guess
605: - -snes_linesearch_max_it              - The number of iterations for iterative line searches

607:   Level: intermediate

609:   Notes:
610:   This is typically called from within a `SNESSolve()` implementation in order to
611:   help with convergence of the nonlinear method.  Various `SNES` types use line searches
612:   in different ways, but the overarching theme is that a line search is used to determine
613:   an optimal damping parameter (that is `lambda`) of a step at each iteration of the method. Each
614:   application of the line search may invoke `SNESComputeFunction()` several times, and
615:   therefore may be fairly expensive.

617: .seealso: [](ch_snes), `SNES`, `SNESLineSearch`, `SNESGetLineSearch()`, `SNESLineSearchCreate()`, `SNESLineSearchGetLambda()`, `SNESLineSearchPreCheck()`, `SNESLineSearchPostCheck()`, `SNESSolve()`, `SNESComputeFunction()`, `SNESLineSearchSetComputeNorms()`,
618:           `SNESLineSearchType`, `SNESLineSearchSetType()`
619: @*/
620: PetscErrorCode SNESLineSearchApply(SNESLineSearch linesearch, Vec X, Vec F, PetscReal *fnorm, Vec Y)
621: {
622:   PetscFunctionBegin;

628:   linesearch->result = SNES_LINESEARCH_SUCCEEDED;

630:   linesearch->vec_sol    = X;
631:   linesearch->vec_update = Y;
632:   linesearch->vec_func   = F;

634:   PetscCall(SNESLineSearchSetUp(linesearch));

636:   if (!linesearch->keeplambda) linesearch->lambda = linesearch->damping; /* set the initial guess to lambda */

638:   if (fnorm) linesearch->fnorm = *fnorm;
639:   else PetscCall(VecNorm(F, NORM_2, &linesearch->fnorm));

641:   PetscCall(PetscLogEventBegin(SNESLINESEARCH_Apply, linesearch, X, F, Y));

643:   PetscUseTypeMethod(linesearch, apply);

645:   PetscCall(PetscLogEventEnd(SNESLINESEARCH_Apply, linesearch, X, F, Y));

647:   if (fnorm) *fnorm = linesearch->fnorm;
648:   PetscFunctionReturn(PETSC_SUCCESS);
649: }

651: /*@
652:   SNESLineSearchDestroy - Destroys the line search instance.

654:   Collective

656:   Input Parameter:
657: . linesearch - The line search context

659:   Level: developer

661:   Note:
662:   The line search in `SNES` is automatically called on `SNESDestroy()` so this call is rarely needed

664: .seealso: [](ch_snes), `SNES`, `SNESLineSearch`, `SNESGetLineSearch()`, `SNESLineSearchCreate()`, `SNESLineSearchReset()`, `SNESDestroy()`
665: @*/
666: PetscErrorCode SNESLineSearchDestroy(SNESLineSearch *linesearch)
667: {
668:   PetscFunctionBegin;
669:   if (!*linesearch) PetscFunctionReturn(PETSC_SUCCESS);
671:   if (--((PetscObject)*linesearch)->refct > 0) {
672:     *linesearch = NULL;
673:     PetscFunctionReturn(PETSC_SUCCESS);
674:   }
675:   PetscCall(PetscObjectSAWsViewOff((PetscObject)*linesearch));
676:   PetscCall(SNESLineSearchReset(*linesearch));
677:   PetscTryTypeMethod(*linesearch, destroy);
678:   PetscCall(PetscViewerDestroy(&(*linesearch)->monitor));
679:   PetscCall(SNESLineSearchMonitorCancel(*linesearch));
680:   PetscCall(PetscHeaderDestroy(linesearch));
681:   PetscFunctionReturn(PETSC_SUCCESS);
682: }

684: /*@
685:   SNESLineSearchSetDefaultMonitor - Turns on/off printing useful information and debugging output about the line search.

687:   Logically Collective

689:   Input Parameters:
690: + linesearch - the linesearch object
691: - viewer     - an `PETSCVIEWERASCII` `PetscViewer` or `NULL` to turn off monitor

693:   Options Database Key:
694: . -snes_linesearch_monitor [:filename] - enables the monitor

696:   Level: intermediate

698:   Developer Notes:
699:   This monitor is implemented differently than the other line search monitors that are set with
700:   `SNESLineSearchMonitorSet()` since it is called in many locations of the line search routines to display aspects of the
701:   line search that are not visible to the other monitors.

703: .seealso: [](ch_snes), `SNES`, `SNESLineSearch`, `PETSCVIEWERASCII`, `SNESGetLineSearch()`, `SNESLineSearchGetDefaultMonitor()`, `PetscViewer`, `SNESLineSearchSetMonitor()`,
704:           `SNESLineSearchMonitorSetFromOptions()`
705: @*/
706: PetscErrorCode SNESLineSearchSetDefaultMonitor(SNESLineSearch linesearch, PetscViewer viewer)
707: {
708:   PetscFunctionBegin;
709:   PetscCall(PetscViewerDestroy(&linesearch->monitor));
710:   linesearch->monitor = viewer;
711:   PetscFunctionReturn(PETSC_SUCCESS);
712: }

714: /*@
715:   SNESLineSearchGetDefaultMonitor - Gets the `PetscViewer` instance for the default line search monitor that is turned on with `SNESLineSearchSetDefaultMonitor()`

717:   Logically Collective

719:   Input Parameter:
720: . linesearch - the line search context

722:   Output Parameter:
723: . monitor - monitor context

725:   Level: intermediate

727: .seealso: [](ch_snes), `SNES`, `SNESLineSearch`, `SNESGetLineSearch()`, `SNESLineSearchSetDefaultMonitor()`, `PetscViewer`
728: @*/
729: PetscErrorCode SNESLineSearchGetDefaultMonitor(SNESLineSearch linesearch, PetscViewer *monitor)
730: {
731:   PetscFunctionBegin;
733:   *monitor = linesearch->monitor;
734:   PetscFunctionReturn(PETSC_SUCCESS);
735: }

737: /*@C
738:   SNESLineSearchMonitorSetFromOptions - Sets a monitor function and viewer appropriate for the type indicated in the options database

740:   Collective

742:   Input Parameters:
743: + ls           - `SNESLineSearch` object to monitor
744: . name         - the monitor type
745: . help         - message indicating what monitoring is done
746: . manual       - manual page for the monitor
747: . monitor      - the monitor function, must use `PetscViewerAndFormat` as its context
748: - monitorsetup - a function that is called once ONLY if the user selected this monitor that may set additional features of the `SNESLineSearch` or `PetscViewer`

750:   Calling sequence of `monitor`:
751: + ls - `SNESLineSearch` object being monitored
752: - vf - a `PetscViewerAndFormat` struct that provides the `PetscViewer` and `PetscViewerFormat` being used

754:   Calling sequence of `monitorsetup`:
755: + ls - `SNESLineSearch` object being monitored
756: - vf - a `PetscViewerAndFormat` struct that provides the `PetscViewer` and `PetscViewerFormat` being used

758:   Level: advanced

760: .seealso: [](ch_snes), `SNES`, `SNESLineSearch`, `SNESLineSearchSetMonitor()`, `PetscOptionsCreateViewer()`, `PetscOptionsGetReal()`, `PetscOptionsHasName()`, `PetscOptionsGetString()`,
761:           `PetscOptionsGetIntArray()`, `PetscOptionsGetRealArray()`, `PetscOptionsBool()`
762:           `PetscOptionsInt()`, `PetscOptionsString()`, `PetscOptionsReal()`,
763:           `PetscOptionsName()`, `PetscOptionsBegin()`, `PetscOptionsEnd()`, `PetscOptionsHeadBegin()`,
764:           `PetscOptionsStringArray()`, `PetscOptionsRealArray()`, `PetscOptionsScalar()`,
765:           `PetscOptionsBoolGroupBegin()`, `PetscOptionsBoolGroup()`, `PetscOptionsBoolGroupEnd()`,
766:           `PetscOptionsFList()`, `PetscOptionsEList()`
767: @*/
768: PetscErrorCode SNESLineSearchMonitorSetFromOptions(SNESLineSearch ls, const char name[], const char help[], const char manual[], PetscErrorCode (*monitor)(SNESLineSearch ls, PetscViewerAndFormat *vf), PetscErrorCode (*monitorsetup)(SNESLineSearch ls, PetscViewerAndFormat *vf))
769: {
770:   PetscViewer       viewer;
771:   PetscViewerFormat format;
772:   PetscBool         flg;

774:   PetscFunctionBegin;
775:   PetscCall(PetscOptionsCreateViewer(PetscObjectComm((PetscObject)ls), ((PetscObject)ls)->options, ((PetscObject)ls)->prefix, name, &viewer, &format, &flg));
776:   if (flg) {
777:     PetscViewerAndFormat *vf;
778:     PetscCall(PetscViewerAndFormatCreate(viewer, format, &vf));
779:     PetscCall(PetscViewerDestroy(&viewer));
780:     if (monitorsetup) PetscCall((*monitorsetup)(ls, vf));
781:     PetscCall(SNESLineSearchMonitorSet(ls, (PetscErrorCode (*)(SNESLineSearch, void *))monitor, vf, (PetscCtxDestroyFn *)PetscViewerAndFormatDestroy));
782:   }
783:   PetscFunctionReturn(PETSC_SUCCESS);
784: }

786: /*@
787:   SNESLineSearchSetFromOptions - Sets options for the line search

789:   Logically Collective

791:   Input Parameter:
792: . linesearch - a `SNESLineSearch` line search context

794:   Options Database Keys:
795: + -snes_linesearch_type <type>                                      - basic (or equivalently none), `bt`, `secant`, `cp`, `nleqerr`, `bisection`, `shell`
796: . -snes_linesearch_order <order>                                    - 1, 2, 3.  Most types only support certain orders (`bt` supports 1, 2 or 3)
797: . -snes_linesearch_norms                                            - Turn on/off the linesearch norms for the basic linesearch typem (`SNESLineSearchSetComputeNorms()`)
798: . -snes_linesearch_minlambda                                        - The minimum `lambda`
799: . -snes_linesearch_maxlambda                                        - The maximum `lambda`
800: . -snes_linesearch_rtol                                             - Relative tolerance for iterative line searches
801: . -snes_linesearch_atol                                             - Absolute tolerance for iterative line searches
802: . -snes_linesearch_ltol                                             - Change in `lambda` tolerance for iterative line searches
803: . -snes_linesearch_max_it                                           - The number of iterations for iterative line searches
804: . -snes_linesearch_monitor [:filename]                              - Print progress of line searches
805: . -snes_linesearch_monitor_solution_update [viewer:filename:format] - view each update tried by line search routine
806: . -snes_linesearch_damping                                          - The linesearch damping parameter
807: . -snes_linesearch_keeplambda                                       - Keep the previous `lambda` as the initial guess.
808: . -snes_linesearch_precheck_picard                                  - Use precheck that speeds up convergence of picard method
809: - -snes_linesearch_precheck_picard_angle                            - Angle used in Picard precheck method

811:   Level: intermediate

813: .seealso: [](ch_snes), `SNES`, `SNESLineSearch`, `SNESGetLineSearch()`, `SNESLineSearchCreate()`, `SNESLineSearchSetOrder()`, `SNESLineSearchSetType()`, `SNESLineSearchSetTolerances()`, `SNESLineSearchSetDamping()`, `SNESLineSearchPreCheckPicard()`,
814:           `SNESLineSearchType`, `SNESLineSearchSetComputeNorms()`
815: @*/
816: PetscErrorCode SNESLineSearchSetFromOptions(SNESLineSearch linesearch)
817: {
818:   const char *deft = SNESLINESEARCHBASIC;
819:   char        type[256];
820:   PetscBool   flg, set;
821:   PetscViewer viewer;

823:   PetscFunctionBegin;
824:   PetscCall(SNESLineSearchRegisterAll());

826:   PetscObjectOptionsBegin((PetscObject)linesearch);
827:   if (((PetscObject)linesearch)->type_name) deft = ((PetscObject)linesearch)->type_name;
828:   PetscCall(PetscOptionsFList("-snes_linesearch_type", "Linesearch type", "SNESLineSearchSetType", SNESLineSearchList, deft, type, 256, &flg));
829:   if (flg) {
830:     PetscCall(SNESLineSearchSetType(linesearch, type));
831:   } else if (!((PetscObject)linesearch)->type_name) {
832:     PetscCall(SNESLineSearchSetType(linesearch, deft));
833:   }

835:   PetscCall(PetscOptionsCreateViewer(PetscObjectComm((PetscObject)linesearch), ((PetscObject)linesearch)->options, ((PetscObject)linesearch)->prefix, "-snes_linesearch_monitor", &viewer, NULL, &set));
836:   if (set) PetscCall(SNESLineSearchSetDefaultMonitor(linesearch, viewer));
837:   PetscCall(SNESLineSearchMonitorSetFromOptions(linesearch, "-snes_linesearch_monitor_solution_update", "View correction at each iteration", "SNESLineSearchMonitorSolutionUpdate", SNESLineSearchMonitorSolutionUpdate, NULL));

839:   /* tolerances */
840:   PetscCall(PetscOptionsReal("-snes_linesearch_minlambda", "Minimum lambda", "SNESLineSearchSetTolerances", linesearch->minlambda, &linesearch->minlambda, NULL));
841:   PetscCall(PetscOptionsReal("-snes_linesearch_maxlambda", "Maximum lambda", "SNESLineSearchSetTolerances", linesearch->maxlambda, &linesearch->maxlambda, NULL));
842:   PetscCall(PetscOptionsReal("-snes_linesearch_rtol", "Relative tolerance for iterative line search", "SNESLineSearchSetTolerances", linesearch->rtol, &linesearch->rtol, NULL));
843:   PetscCall(PetscOptionsReal("-snes_linesearch_atol", "Absolute tolerance for iterative line search", "SNESLineSearchSetTolerances", linesearch->atol, &linesearch->atol, NULL));
844:   PetscCall(PetscOptionsReal("-snes_linesearch_ltol", "Change in lambda tolerance for iterative line search", "SNESLineSearchSetTolerances", linesearch->ltol, &linesearch->ltol, NULL));
845:   PetscCall(PetscOptionsInt("-snes_linesearch_max_it", "Maximum iterations for iterative line searches", "SNESLineSearchSetTolerances", linesearch->max_it, &linesearch->max_it, NULL));

847:   /* deprecated options */
848:   PetscCall(PetscOptionsDeprecated("-snes_linesearch_maxstep", "-snes_linesearch_maxlambda", "3.24.0", NULL));

850:   /* damping parameters */
851:   PetscCall(PetscOptionsReal("-snes_linesearch_damping", "Line search damping (and depending on chosen line search initial lambda guess)", "SNESLineSearchSetDamping", linesearch->damping, &linesearch->damping, NULL));

853:   PetscCall(PetscOptionsBool("-snes_linesearch_keeplambda", "Use previous lambda as damping", "SNESLineSearchSetKeepLambda", linesearch->keeplambda, &linesearch->keeplambda, NULL));

855:   /* precheck */
856:   PetscCall(PetscOptionsBool("-snes_linesearch_precheck_picard", "Use a correction that sometimes improves convergence of Picard iteration", "SNESLineSearchPreCheckPicard", flg, &flg, &set));
857:   if (set) {
858:     if (flg) {
859:       linesearch->precheck_picard_angle = 10.; /* correction only active if angle is less than 10 degrees */

861:       PetscCall(PetscOptionsReal("-snes_linesearch_precheck_picard_angle", "Maximum angle at which to activate the correction", "none", linesearch->precheck_picard_angle, &linesearch->precheck_picard_angle, NULL));
862:       PetscCall(SNESLineSearchSetPreCheck(linesearch, SNESLineSearchPreCheckPicard, &linesearch->precheck_picard_angle));
863:     } else {
864:       PetscCall(SNESLineSearchSetPreCheck(linesearch, NULL, NULL));
865:     }
866:   }
867:   PetscCall(PetscOptionsInt("-snes_linesearch_order", "Order of approximation used in the line search", "SNESLineSearchSetOrder", linesearch->order, &linesearch->order, NULL));
868:   PetscCall(PetscOptionsBool("-snes_linesearch_norms", "Compute final norms in line search", "SNESLineSearchSetComputeNorms", linesearch->norms, &linesearch->norms, NULL));

870:   PetscTryTypeMethod(linesearch, setfromoptions, PetscOptionsObject);

872:   PetscCall(PetscObjectProcessOptionsHandlers((PetscObject)linesearch, PetscOptionsObject));
873:   PetscOptionsEnd();
874:   PetscFunctionReturn(PETSC_SUCCESS);
875: }

877: /*@
878:   SNESLineSearchView - Prints useful information about the line search

880:   Logically Collective

882:   Input Parameters:
883: + linesearch - line search context
884: - viewer     - the `PetscViewer` to display the line search information to

886:   Level: intermediate

888: .seealso: [](ch_snes), `SNES`, `SNESLineSearch`, `PetscViewer`, `SNESLineSearchCreate()`
889: @*/
890: PetscErrorCode SNESLineSearchView(SNESLineSearch linesearch, PetscViewer viewer)
891: {
892:   PetscBool isascii;

894:   PetscFunctionBegin;
896:   if (!viewer) PetscCall(PetscViewerASCIIGetStdout(PetscObjectComm((PetscObject)linesearch), &viewer));
898:   PetscCheckSameComm(linesearch, 1, viewer, 2);

900:   PetscCall(PetscObjectTypeCompare((PetscObject)viewer, PETSCVIEWERASCII, &isascii));
901:   if (isascii) {
902:     PetscCall(PetscObjectPrintClassNamePrefixType((PetscObject)linesearch, viewer));
903:     PetscCall(PetscViewerASCIIPushTab(viewer));
904:     PetscTryTypeMethod(linesearch, view, viewer);
905:     PetscCall(PetscViewerASCIIPopTab(viewer));
906:     PetscCall(PetscViewerASCIIPrintf(viewer, "  maxlambda=%e, minlambda=%e\n", (double)linesearch->maxlambda, (double)linesearch->minlambda));
907:     PetscCall(PetscViewerASCIIPrintf(viewer, "  tolerances: relative=%e, absolute=%e, lambda=%e\n", (double)linesearch->rtol, (double)linesearch->atol, (double)linesearch->ltol));
908:     PetscCall(PetscViewerASCIIPrintf(viewer, "  maximum iterations=%" PetscInt_FMT "\n", linesearch->max_it));
909:     if (linesearch->ops->precheck) {
910:       if (linesearch->ops->precheck == SNESLineSearchPreCheckPicard) {
911:         PetscCall(PetscViewerASCIIPrintf(viewer, "  using precheck step to speed up Picard convergence\n"));
912:       } else {
913:         PetscCall(PetscViewerASCIIPrintf(viewer, "  using user-defined precheck step\n"));
914:       }
915:     }
916:     if (linesearch->ops->postcheck) PetscCall(PetscViewerASCIIPrintf(viewer, "  using user-defined postcheck step\n"));
917:   }
918:   PetscFunctionReturn(PETSC_SUCCESS);
919: }

921: /*@
922:   SNESLineSearchGetType - Gets the `SNESLinesearchType` of a `SNESLineSearch`

924:   Logically Collective

926:   Input Parameter:
927: . linesearch - the line search context

929:   Output Parameter:
930: . type - The type of line search, or `NULL` if not set

932:   Level: intermediate

934: .seealso: [](ch_snes), `SNES`, `SNESLineSearch`, `SNESLineSearchType`, `SNESLineSearchCreate()`, `SNESLineSearchSetFromOptions()`, `SNESLineSearchSetType()`
935: @*/
936: PetscErrorCode SNESLineSearchGetType(SNESLineSearch linesearch, SNESLineSearchType *type)
937: {
938:   PetscFunctionBegin;
940:   PetscAssertPointer(type, 2);
941:   *type = ((PetscObject)linesearch)->type_name;
942:   PetscFunctionReturn(PETSC_SUCCESS);
943: }

945: /*@
946:   SNESLineSearchSetType - Sets the `SNESLinesearchType` of a `SNESLineSearch` object to indicate the line search algorithm that should be used by a given `SNES` solver

948:   Logically Collective

950:   Input Parameters:
951: + linesearch - the line search context
952: - type       - The type of line search to be used, see `SNESLineSearchType`

954:   Options Database Key:
955: . -snes_linesearch_type <type> - basic (or equivalently none), bt, secant, cp, nleqerr, bisection, shell

957:   Level: intermediate

959:   Note:
960:   The `SNESLineSearch` object is generally obtained with `SNESGetLineSearch()`

962: .seealso: [](ch_snes), `SNES`, `SNESLineSearch`, `SNESLineSearchType`, `SNESLineSearchCreate()`, `SNESLineSearchSetFromOptions()`, `SNESLineSearchGetType()`,
963:           `SNESGetLineSearch()`
964: @*/
965: PetscErrorCode SNESLineSearchSetType(SNESLineSearch linesearch, SNESLineSearchType type)
966: {
967:   PetscBool match;
968:   PetscErrorCode (*r)(SNESLineSearch);

970:   PetscFunctionBegin;
972:   PetscAssertPointer(type, 2);

974:   PetscCall(PetscObjectTypeCompare((PetscObject)linesearch, type, &match));
975:   if (match) PetscFunctionReturn(PETSC_SUCCESS);

977:   PetscCall(PetscFunctionListFind(SNESLineSearchList, type, &r));
978:   PetscCheck(r, PetscObjectComm((PetscObject)linesearch), PETSC_ERR_ARG_UNKNOWN_TYPE, "Unable to find requested Line Search type %s", type);
979:   /* Destroy the previous private line search context */
980:   PetscTryTypeMethod(linesearch, destroy);
981:   linesearch->ops->destroy = NULL;
982:   /* Reinitialize function pointers in SNESLineSearchOps structure */
983:   linesearch->ops->apply          = NULL;
984:   linesearch->ops->view           = NULL;
985:   linesearch->ops->setfromoptions = NULL;
986:   linesearch->ops->destroy        = NULL;

988:   PetscCall(PetscObjectChangeTypeName((PetscObject)linesearch, type));
989:   PetscCall((*r)(linesearch));
990:   PetscFunctionReturn(PETSC_SUCCESS);
991: }

993: /*@
994:   SNESLineSearchSetSNES - Sets the `SNES` for the linesearch for function evaluation.

996:   Input Parameters:
997: + linesearch - the line search context
998: - snes       - The `SNES` instance

1000:   Level: developer

1002:   Note:
1003:   This happens automatically when the line search is obtained/created with
1004:   `SNESGetLineSearch()`.  This routine is therefore mainly called within `SNES`
1005:   implementations.

1007: .seealso: [](ch_snes), `SNES`, `SNESLineSearch`, `SNESLineSearchGetSNES()`, `SNESLineSearchSetVecs()`
1008: @*/
1009: PetscErrorCode SNESLineSearchSetSNES(SNESLineSearch linesearch, SNES snes)
1010: {
1011:   PetscFunctionBegin;
1014:   linesearch->snes = snes;
1015:   PetscFunctionReturn(PETSC_SUCCESS);
1016: }

1018: /*@
1019:   SNESLineSearchGetSNES - Gets the `SNES` instance associated with the line search.

1021:   Not Collective

1023:   Input Parameter:
1024: . linesearch - the line search context

1026:   Output Parameter:
1027: . snes - The `SNES` instance

1029:   Level: developer

1031: .seealso: [](ch_snes), `SNES`, `SNESLineSearch`, `SNESType`, `SNESLineSearchSetVecs()`
1032: @*/
1033: PetscErrorCode SNESLineSearchGetSNES(SNESLineSearch linesearch, SNES *snes)
1034: {
1035:   PetscFunctionBegin;
1037:   PetscAssertPointer(snes, 2);
1038:   *snes = linesearch->snes;
1039:   PetscFunctionReturn(PETSC_SUCCESS);
1040: }

1042: /*@
1043:   SNESLineSearchGetLambda - Gets the last line search `lambda` used

1045:   Not Collective

1047:   Input Parameter:
1048: . linesearch - the line search context

1050:   Output Parameter:
1051: . lambda - The last `lambda` (scaling of the solution update) computed during `SNESLineSearchApply()`

1053:   Level: advanced

1055:   Note:
1056:   This is useful in methods where the solver is ill-scaled and
1057:   requires some adaptive notion of the difference in scale between the
1058:   solution and the function.  For instance, `SNESQN` may be scaled by the
1059:   line search `lambda` using the argument -snes_qn_scaling ls.

1061: .seealso: [](ch_snes), `SNES`, `SNESLineSearch`, `SNESLineSearchSetLambda()`, `SNESLineSearchGetDamping()`, `SNESLineSearchApply()`
1062: @*/
1063: PetscErrorCode SNESLineSearchGetLambda(SNESLineSearch linesearch, PetscReal *lambda)
1064: {
1065:   PetscFunctionBegin;
1067:   PetscAssertPointer(lambda, 2);
1068:   *lambda = linesearch->lambda;
1069:   PetscFunctionReturn(PETSC_SUCCESS);
1070: }

1072: /*@
1073:   SNESLineSearchSetLambda - Sets the line search `lambda` (scaling of the solution update)

1075:   Input Parameters:
1076: + linesearch - line search context
1077: - lambda     - The `lambda` to use

1079:   Level: advanced

1081:   Note:
1082:   This routine is typically used within implementations of `SNESLineSearchApply()`
1083:   to set the final `lambda`.  This routine (and `SNESLineSearchGetLambda()`) were
1084:   added to facilitate Quasi-Newton methods that use the previous `lambda`
1085:   as an inner scaling parameter.

1087: .seealso: [](ch_snes), `SNES`, `SNESLineSearch`, `SNESLineSearchGetLambda()`
1088: @*/
1089: PetscErrorCode SNESLineSearchSetLambda(SNESLineSearch linesearch, PetscReal lambda)
1090: {
1091:   PetscFunctionBegin;
1093:   linesearch->lambda = lambda;
1094:   PetscFunctionReturn(PETSC_SUCCESS);
1095: }

1097: /*@
1098:   SNESLineSearchGetTolerances - Gets the tolerances for the line search.

1100:   Not Collective

1102:   Input Parameter:
1103: . linesearch - the line search context

1105:   Output Parameters:
1106: + minlambda - The minimum `lambda` allowed
1107: . maxlambda - The maximum `lambda` allowed
1108: . rtol      - The relative tolerance for iterative line searches
1109: . atol      - The absolute tolerance for iterative line searches
1110: . ltol      - The change in `lambda` tolerance for iterative line searches
1111: - max_it    - The maximum number of iterations of the line search

1113:   Level: intermediate

1115:   Note:
1116:   Different line searches may implement these parameters slightly differently as
1117:   the type requires.

1119: .seealso: [](ch_snes), `SNES`, `SNESLineSearch`, `SNESLineSearchSetTolerances()`
1120: @*/
1121: PetscErrorCode SNESLineSearchGetTolerances(SNESLineSearch linesearch, PetscReal *minlambda, PetscReal *maxlambda, PetscReal *rtol, PetscReal *atol, PetscReal *ltol, PetscInt *max_it)
1122: {
1123:   PetscFunctionBegin;
1125:   if (minlambda) {
1126:     PetscAssertPointer(minlambda, 2);
1127:     *minlambda = linesearch->minlambda;
1128:   }
1129:   if (maxlambda) {
1130:     PetscAssertPointer(maxlambda, 3);
1131:     *maxlambda = linesearch->maxlambda;
1132:   }
1133:   if (rtol) {
1134:     PetscAssertPointer(rtol, 4);
1135:     *rtol = linesearch->rtol;
1136:   }
1137:   if (atol) {
1138:     PetscAssertPointer(atol, 5);
1139:     *atol = linesearch->atol;
1140:   }
1141:   if (ltol) {
1142:     PetscAssertPointer(ltol, 6);
1143:     *ltol = linesearch->ltol;
1144:   }
1145:   if (max_it) {
1146:     PetscAssertPointer(max_it, 7);
1147:     *max_it = linesearch->max_it;
1148:   }
1149:   PetscFunctionReturn(PETSC_SUCCESS);
1150: }

1152: /*@
1153:   SNESLineSearchSetTolerances -  Sets the tolerances for the linesearch.

1155:   Collective

1157:   Input Parameters:
1158: + linesearch - the line search context
1159: . minlambda  - The minimum `lambda` allowed
1160: . maxlambda  - The maximum `lambda` allowed
1161: . rtol       - The relative tolerance for iterative line searches
1162: . atol       - The absolute tolerance for iterative line searches
1163: . ltol       - The change in `lambda` tolerance for iterative line searches
1164: - max_it     - The maximum number of iterations of the line search

1166:   Options Database Keys:
1167: + -snes_linesearch_minlambda - The minimum `lambda` allowed
1168: . -snes_linesearch_maxlambda - The maximum `lambda` allowed
1169: . -snes_linesearch_rtol      - Relative tolerance for iterative line searches
1170: . -snes_linesearch_atol      - Absolute tolerance for iterative line searches
1171: . -snes_linesearch_ltol      - Change in `lambda` tolerance for iterative line searches
1172: - -snes_linesearch_max_it    - The number of iterations for iterative line searches

1174:   Level: intermediate

1176:   Note:
1177:   The user may choose to not set any of the tolerances using `PETSC_DEFAULT` in place of an argument.

1179: .seealso: [](ch_snes), `SNES`, `SNESLineSearch`, `SNESLineSearchGetTolerances()`
1180: @*/
1181: PetscErrorCode SNESLineSearchSetTolerances(SNESLineSearch linesearch, PetscReal minlambda, PetscReal maxlambda, PetscReal rtol, PetscReal atol, PetscReal ltol, PetscInt max_it)
1182: {
1183:   PetscFunctionBegin;

1192:   if (minlambda != (PetscReal)PETSC_DEFAULT) {
1193:     PetscCheck(minlambda >= 0.0, PetscObjectComm((PetscObject)linesearch), PETSC_ERR_ARG_OUTOFRANGE, "Minimum lambda %14.12e must be non-negative", (double)minlambda);
1194:     PetscCheck(minlambda < maxlambda, PetscObjectComm((PetscObject)linesearch), PETSC_ERR_ARG_OUTOFRANGE, "Minimum lambda %14.12e must be smaller than maximum lambda %14.12e", (double)minlambda, (double)maxlambda);
1195:     linesearch->minlambda = minlambda;
1196:   }

1198:   if (maxlambda != (PetscReal)PETSC_DEFAULT) {
1199:     PetscCheck(maxlambda > 0.0, PetscObjectComm((PetscObject)linesearch), PETSC_ERR_ARG_OUTOFRANGE, "Maximum lambda %14.12e must be positive", (double)maxlambda);
1200:     linesearch->maxlambda = maxlambda;
1201:   }

1203:   if (rtol != (PetscReal)PETSC_DEFAULT) {
1204:     PetscCheck(rtol >= 0.0 && rtol < 1.0, PetscObjectComm((PetscObject)linesearch), PETSC_ERR_ARG_OUTOFRANGE, "Relative tolerance %14.12e must be non-negative and less than 1.0", (double)rtol);
1205:     linesearch->rtol = rtol;
1206:   }

1208:   if (atol != (PetscReal)PETSC_DEFAULT) {
1209:     PetscCheck(atol >= 0.0, PetscObjectComm((PetscObject)linesearch), PETSC_ERR_ARG_OUTOFRANGE, "Absolute tolerance %14.12e must be non-negative", (double)atol);
1210:     linesearch->atol = atol;
1211:   }

1213:   if (ltol != (PetscReal)PETSC_DEFAULT) {
1214:     PetscCheck(ltol >= 0.0, PetscObjectComm((PetscObject)linesearch), PETSC_ERR_ARG_OUTOFRANGE, "Lambda tolerance %14.12e must be non-negative", (double)ltol);
1215:     linesearch->ltol = ltol;
1216:   }

1218:   if (max_it != PETSC_DEFAULT) {
1219:     PetscCheck(max_it >= 0, PetscObjectComm((PetscObject)linesearch), PETSC_ERR_ARG_OUTOFRANGE, "Maximum number of iterations %" PetscInt_FMT " must be non-negative", max_it);
1220:     linesearch->max_it = max_it;
1221:   }
1222:   PetscFunctionReturn(PETSC_SUCCESS);
1223: }

1225: /*@
1226:   SNESLineSearchGetDamping - Gets the line search damping parameter.

1228:   Input Parameter:
1229: . linesearch - the line search context

1231:   Output Parameter:
1232: . damping - The damping parameter

1234:   Level: advanced

1236: .seealso: [](ch_snes), `SNES`, `SNESLineSearchGetStepTolerance()`, `SNESQN`
1237: @*/
1238: PetscErrorCode SNESLineSearchGetDamping(SNESLineSearch linesearch, PetscReal *damping)
1239: {
1240:   PetscFunctionBegin;
1242:   PetscAssertPointer(damping, 2);
1243:   *damping = linesearch->damping;
1244:   PetscFunctionReturn(PETSC_SUCCESS);
1245: }

1247: /*@
1248:   SNESLineSearchSetDamping - Sets the line search damping parameter.

1250:   Input Parameters:
1251: + linesearch - the line search context
1252: - damping    - The damping parameter

1254:   Options Database Key:
1255: . -snes_linesearch_damping <damping> - the damping value

1257:   Level: intermediate

1259:   Note:
1260:   The `SNESLINESEARCHNONE` line search merely takes the update step scaled by the damping parameter.
1261:   The use of the damping parameter in the `SNESLINESEARCHSECANT` and `SNESLINESEARCHCP` line searches is much more subtle;
1262:   it is used as a starting point for the secant method. Depending on the choice for `maxlambda`,
1263:   the eventual `lambda` may be greater than the damping parameter however.
1264:   For `SNESLINESEARCHBISECTION` and `SNESLINESEARCHBT` the damping is instead used as the initial guess,
1265:   below which the line search will not go. Hence, it is the maximum possible value for `lambda`.

1267: .seealso: [](ch_snes), `SNES`, `SNESLineSearch`, `SNESLineSearchGetDamping()`
1268: @*/
1269: PetscErrorCode SNESLineSearchSetDamping(SNESLineSearch linesearch, PetscReal damping)
1270: {
1271:   PetscFunctionBegin;
1273:   linesearch->damping = damping;
1274:   PetscFunctionReturn(PETSC_SUCCESS);
1275: }

1277: /*@
1278:   SNESLineSearchGetOrder - Gets the line search approximation order.

1280:   Input Parameter:
1281: . linesearch - the line search context

1283:   Output Parameter:
1284: . order - The order

1286:   Level: intermediate

1288: .seealso: [](ch_snes), `SNES`, `SNESLineSearch`, `SNESLineSearchSetOrder()`
1289: @*/
1290: PetscErrorCode SNESLineSearchGetOrder(SNESLineSearch linesearch, PetscInt *order)
1291: {
1292:   PetscFunctionBegin;
1294:   PetscAssertPointer(order, 2);
1295:   *order = linesearch->order;
1296:   PetscFunctionReturn(PETSC_SUCCESS);
1297: }

1299: /*@
1300:   SNESLineSearchSetOrder - Sets the maximum order of the polynomial fit used in the line search

1302:   Input Parameters:
1303: + linesearch - the line search context
1304: - order      - The order

1306:   Level: intermediate

1308:   Values for `order`\:
1309: +  1 or `SNES_LINESEARCH_ORDER_LINEAR` - linear order
1310: .  2 or `SNES_LINESEARCH_ORDER_QUADRATIC` - quadratic order
1311: -  3 or `SNES_LINESEARCH_ORDER_CUBIC` - cubic order

1313:   Options Database Key:
1314: . -snes_linesearch_order <order> - 1, 2, 3.  Most types only support certain orders (`SNESLINESEARCHBT` supports 2 or 3)

1316:   Note:
1317:   These orders are supported by `SNESLINESEARCHBT` and `SNESLINESEARCHCP`

1319: .seealso: [](ch_snes), `SNES`, `SNESLineSearch`, `SNESLineSearchGetOrder()`, `SNESLineSearchSetDamping()`
1320: @*/
1321: PetscErrorCode SNESLineSearchSetOrder(SNESLineSearch linesearch, PetscInt order)
1322: {
1323:   PetscFunctionBegin;
1325:   linesearch->order = order;
1326:   PetscFunctionReturn(PETSC_SUCCESS);
1327: }

1329: /*@
1330:   SNESLineSearchGetNorms - Gets the norms for the current solution `X`, the current update `Y`, and the current function value `F`.

1332:   Not Collective

1334:   Input Parameter:
1335: . linesearch - the line search context

1337:   Output Parameters:
1338: + xnorm - The norm of the current solution
1339: . fnorm - The norm of the current function, this is the `norm(function(X))` where `X` is the current solution.
1340: - ynorm - The norm of the current update (after scaling by the linesearch computed `lambda`)

1342:   Level: developer

1344:   Notes:
1345:   Some values may not be up-to-date at particular points in the code.

1347:   This, in combination with `SNESLineSearchSetNorms()`, allow the line search and the `SNESSolve_XXX()` to share
1348:   computed values.

1350: .seealso: [](ch_snes), `SNES`, `SNESLineSearch`, `SNESLineSearchSetNorms()`, `SNESLineSearchGetVecs()`
1351: @*/
1352: PetscErrorCode SNESLineSearchGetNorms(SNESLineSearch linesearch, PetscReal *xnorm, PetscReal *fnorm, PetscReal *ynorm)
1353: {
1354:   PetscFunctionBegin;
1356:   if (xnorm) *xnorm = linesearch->xnorm;
1357:   if (fnorm) *fnorm = linesearch->fnorm;
1358:   if (ynorm) *ynorm = linesearch->ynorm;
1359:   PetscFunctionReturn(PETSC_SUCCESS);
1360: }

1362: /*@
1363:   SNESLineSearchSetNorms - Sets the computed norms for the current solution `X`, the current update `Y`, and the current function value `F`.

1365:   Collective

1367:   Input Parameters:
1368: + linesearch - the line search context
1369: . xnorm      - The norm of the current solution
1370: . fnorm      - The norm of the current function, this is the `norm(function(X))` where `X` is the current solution
1371: - ynorm      - The norm of the current update (after scaling by the linesearch computed `lambda`)

1373:   Level: developer

1375:   Note:
1376:   This is called by the line search routines to store the values they have just computed

1378: .seealso: [](ch_snes), `SNES`, `SNESLineSearch`, `SNESLineSearchGetNorms()`, `SNESLineSearchSetVecs()`
1379: @*/
1380: PetscErrorCode SNESLineSearchSetNorms(SNESLineSearch linesearch, PetscReal xnorm, PetscReal fnorm, PetscReal ynorm)
1381: {
1382:   PetscFunctionBegin;
1384:   linesearch->xnorm = xnorm;
1385:   linesearch->fnorm = fnorm;
1386:   linesearch->ynorm = ynorm;
1387:   PetscFunctionReturn(PETSC_SUCCESS);
1388: }

1390: /*@
1391:   SNESLineSearchComputeNorms - Explicitly computes the norms of the current solution `X`, the current update `Y`, and the current function value `F`.

1393:   Input Parameter:
1394: . linesearch - the line search context

1396:   Options Database Key:
1397: . -snes_linesearch_norms - turn norm computation on or off

1399:   Level: intermediate

1401:   Developer Note:
1402:   The options database key is misnamed. It should be -snes_linesearch_compute_norms

1404: .seealso: [](ch_snes), `SNES`, `SNESLineSearch`, `SNESLineSearchGetNorms`, `SNESLineSearchSetNorms()`, `SNESLineSearchSetComputeNorms()`
1405: @*/
1406: PetscErrorCode SNESLineSearchComputeNorms(SNESLineSearch linesearch)
1407: {
1408:   SNES snes;

1410:   PetscFunctionBegin;
1411:   if (linesearch->norms) {
1412:     if (linesearch->ops->vinorm) {
1413:       PetscCall(SNESLineSearchGetSNES(linesearch, &snes));
1414:       PetscCall(VecNorm(linesearch->vec_sol, NORM_2, &linesearch->xnorm));
1415:       PetscCall(VecNorm(linesearch->vec_update, NORM_2, &linesearch->ynorm));
1416:       PetscCall((*linesearch->ops->vinorm)(snes, linesearch->vec_func, linesearch->vec_sol, &linesearch->fnorm));
1417:     } else {
1418:       PetscCall(VecNormBegin(linesearch->vec_func, NORM_2, &linesearch->fnorm));
1419:       PetscCall(VecNormBegin(linesearch->vec_sol, NORM_2, &linesearch->xnorm));
1420:       PetscCall(VecNormBegin(linesearch->vec_update, NORM_2, &linesearch->ynorm));
1421:       PetscCall(VecNormEnd(linesearch->vec_func, NORM_2, &linesearch->fnorm));
1422:       PetscCall(VecNormEnd(linesearch->vec_sol, NORM_2, &linesearch->xnorm));
1423:       PetscCall(VecNormEnd(linesearch->vec_update, NORM_2, &linesearch->ynorm));
1424:     }
1425:   }
1426:   PetscFunctionReturn(PETSC_SUCCESS);
1427: }

1429: /*@
1430:   SNESLineSearchSetComputeNorms - Turns on or off the computation of final norms in the line search.

1432:   Input Parameters:
1433: + linesearch - the line search context
1434: - flg        - indicates whether or not to compute norms

1436:   Options Database Key:
1437: . -snes_linesearch_norms <true> - Turns on/off computation of the norms for basic (none) `SNESLINESEARCHBASIC` line search

1439:   Level: intermediate

1441:   Note:
1442:   This is most relevant to the `SNESLINESEARCHBASIC` (or equivalently `SNESLINESEARCHNONE`) line search type since most line searches have a stopping criteria involving the norm.

1444:   Developer Note:
1445:   The options database key is misnamed. It should be -snes_linesearch_compute_norms

1447: .seealso: [](ch_snes), `SNES`, `SNESLineSearch`, `SNESLineSearchGetNorms()`, `SNESLineSearchSetNorms()`, `SNESLineSearchComputeNorms()`, `SNESLINESEARCHBASIC`
1448: @*/
1449: PetscErrorCode SNESLineSearchSetComputeNorms(SNESLineSearch linesearch, PetscBool flg)
1450: {
1451:   PetscFunctionBegin;
1452:   linesearch->norms = flg;
1453:   PetscFunctionReturn(PETSC_SUCCESS);
1454: }

1456: /*@
1457:   SNESLineSearchGetVecs - Gets the vectors from the `SNESLineSearch` context

1459:   Not Collective but the vectors are parallel

1461:   Input Parameter:
1462: . linesearch - the line search context

1464:   Output Parameters:
1465: + X - Solution vector
1466: . F - Function vector
1467: . Y - Search direction vector
1468: . W - Solution work vector
1469: - G - Function work vector

1471:   Level: advanced

1473:   Notes:
1474:   At the beginning of a line search application, `X` should contain a
1475:   solution and the vector `F` the function computed at `X`.  At the end of the
1476:   line search application, `X` should contain the new solution, and `F` the
1477:   function evaluated at the new solution.

1479:   These vectors are owned by the `SNESLineSearch` and should not be destroyed by the caller

1481: .seealso: [](ch_snes), `SNES`, `SNESLineSearch`, `SNESLineSearchGetNorms()`, `SNESLineSearchSetVecs()`
1482: @*/
1483: PetscErrorCode SNESLineSearchGetVecs(SNESLineSearch linesearch, Vec *X, Vec *F, Vec *Y, Vec *W, Vec *G)
1484: {
1485:   PetscFunctionBegin;
1487:   if (X) {
1488:     PetscAssertPointer(X, 2);
1489:     *X = linesearch->vec_sol;
1490:   }
1491:   if (F) {
1492:     PetscAssertPointer(F, 3);
1493:     *F = linesearch->vec_func;
1494:   }
1495:   if (Y) {
1496:     PetscAssertPointer(Y, 4);
1497:     *Y = linesearch->vec_update;
1498:   }
1499:   if (W) {
1500:     PetscAssertPointer(W, 5);
1501:     *W = linesearch->vec_sol_new;
1502:   }
1503:   if (G) {
1504:     PetscAssertPointer(G, 6);
1505:     *G = linesearch->vec_func_new;
1506:   }
1507:   PetscFunctionReturn(PETSC_SUCCESS);
1508: }

1510: /*@
1511:   SNESLineSearchSetVecs - Sets the vectors on the `SNESLineSearch` context

1513:   Logically Collective

1515:   Input Parameters:
1516: + linesearch - the line search context
1517: . X          - Solution vector
1518: . F          - Function vector
1519: . Y          - Search direction vector
1520: . W          - Solution work vector
1521: - G          - Function work vector

1523:   Level: developer

1525: .seealso: [](ch_snes), `SNES`, `SNESLineSearch`, `SNESLineSearchSetNorms()`, `SNESLineSearchGetVecs()`
1526: @*/
1527: PetscErrorCode SNESLineSearchSetVecs(SNESLineSearch linesearch, Vec X, Vec F, Vec Y, Vec W, Vec G)
1528: {
1529:   PetscFunctionBegin;
1531:   if (X) {
1533:     linesearch->vec_sol = X;
1534:   }
1535:   if (F) {
1537:     linesearch->vec_func = F;
1538:   }
1539:   if (Y) {
1541:     linesearch->vec_update = Y;
1542:   }
1543:   if (W) {
1545:     linesearch->vec_sol_new = W;
1546:   }
1547:   if (G) {
1549:     linesearch->vec_func_new = G;
1550:   }
1551:   PetscFunctionReturn(PETSC_SUCCESS);
1552: }

1554: /*@
1555:   SNESLineSearchAppendOptionsPrefix - Appends to the prefix used for searching for all
1556:   `SNESLineSearch` options in the database.

1558:   Logically Collective

1560:   Input Parameters:
1561: + linesearch - the `SNESLineSearch` context
1562: - prefix     - the prefix to prepend to all option names

1564:   Level: advanced

1566:   Note:
1567:   A hyphen (-) must NOT be given at the beginning of the prefix name.
1568:   The first character of all runtime options is AUTOMATICALLY the hyphen.

1570: .seealso: [](ch_snes), `SNES`, `SNESLineSearch()`, `SNESLineSearchSetFromOptions()`, `SNESGetOptionsPrefix()`
1571: @*/
1572: PetscErrorCode SNESLineSearchAppendOptionsPrefix(SNESLineSearch linesearch, const char prefix[])
1573: {
1574:   PetscFunctionBegin;
1576:   PetscCall(PetscObjectAppendOptionsPrefix((PetscObject)linesearch, prefix));
1577:   PetscFunctionReturn(PETSC_SUCCESS);
1578: }

1580: /*@
1581:   SNESLineSearchGetOptionsPrefix - Gets the prefix used for searching for all
1582:   SNESLineSearch options in the database.

1584:   Not Collective

1586:   Input Parameter:
1587: . linesearch - the `SNESLineSearch` context

1589:   Output Parameter:
1590: . prefix - pointer to the prefix string used

1592:   Level: advanced

1594: .seealso: [](ch_snes), `SNES`, `SNESLineSearch`, `SNESAppendOptionsPrefix()`
1595: @*/
1596: PetscErrorCode SNESLineSearchGetOptionsPrefix(SNESLineSearch linesearch, const char *prefix[])
1597: {
1598:   PetscFunctionBegin;
1600:   PetscCall(PetscObjectGetOptionsPrefix((PetscObject)linesearch, prefix));
1601:   PetscFunctionReturn(PETSC_SUCCESS);
1602: }

1604: /*@C
1605:   SNESLineSearchSetWorkVecs - Sets work vectors for the line search.

1607:   Input Parameters:
1608: + linesearch - the `SNESLineSearch` context
1609: - nwork      - the number of work vectors

1611:   Level: developer

1613:   Developer Note:
1614:   This is called from within the set up routines for each of the line search types `SNESLineSearchType`

1616: .seealso: [](ch_snes), `SNES`, `SNESLineSearch`, `SNESSetWorkVecs()`
1617: @*/
1618: PetscErrorCode SNESLineSearchSetWorkVecs(SNESLineSearch linesearch, PetscInt nwork)
1619: {
1620:   PetscFunctionBegin;
1621:   PetscCheck(linesearch->vec_sol, PetscObjectComm((PetscObject)linesearch), PETSC_ERR_USER, "Cannot get linesearch work-vectors without setting a solution vec!");
1622:   PetscCall(VecDuplicateVecs(linesearch->vec_sol, nwork, &linesearch->work));
1623:   PetscFunctionReturn(PETSC_SUCCESS);
1624: }

1626: /*@
1627:   SNESLineSearchGetReason - Gets the success/failure status of the last line search application

1629:   Input Parameter:
1630: . linesearch - the line search context

1632:   Output Parameter:
1633: . result - The success or failure status

1635:   Level: developer

1637:   Note:
1638:   This is typically called after `SNESLineSearchApply()` in order to determine if the line search failed
1639:   (and set into the `SNES` convergence accordingly).

1641: .seealso: [](ch_snes), `SNES`, `SNESLineSearch`, `SNESLineSearchSetReason()`, `SNESLineSearchReason`
1642: @*/
1643: PetscErrorCode SNESLineSearchGetReason(SNESLineSearch linesearch, SNESLineSearchReason *result)
1644: {
1645:   PetscFunctionBegin;
1647:   PetscAssertPointer(result, 2);
1648:   *result = linesearch->result;
1649:   PetscFunctionReturn(PETSC_SUCCESS);
1650: }

1652: /*@
1653:   SNESLineSearchSetReason - Sets the success/failure status of the line search application

1655:   Logically Collective; No Fortran Support

1657:   Input Parameters:
1658: + linesearch - the line search context
1659: - result     - The success or failure status

1661:   Level: developer

1663:   Note:
1664:   This is typically called in a `SNESLineSearchType` implementation of `SNESLineSearchApply()` or a `SNESLINESEARCHSHELL` implementation to set
1665:   the success or failure of the line search method.

1667: .seealso: [](ch_snes), `SNES`, `SNESLineSearch`, `SNESLineSearchReason`, `SNESLineSearchGetSResult()`
1668: @*/
1669: PetscErrorCode SNESLineSearchSetReason(SNESLineSearch linesearch, SNESLineSearchReason result)
1670: {
1671:   PetscFunctionBegin;
1673:   linesearch->result = result;
1674:   PetscFunctionReturn(PETSC_SUCCESS);
1675: }

1677: // PetscClangLinter pragma disable: -fdoc-param-list-func-parameter-documentation
1678: /*@C
1679:   SNESLineSearchSetVIFunctions - Sets VI-specific functions for line search computation.

1681:   Logically Collective

1683:   Input Parameters:
1684: + linesearch   - the linesearch object
1685: . projectfunc  - function for projecting the function to the bounds, see `SNESLineSearchVIProjectFn` for calling sequence
1686: . normfunc     - function for computing the norm of an active set, see `SNESLineSearchVINormFn` for calling sequence
1687: - dirderivfunc - function for computing the directional derivative of an active set, see `SNESLineSearchVIDirDerivFn` for calling sequence

1689:   Level: advanced

1691:   Notes:
1692:   The VI solvers require projection of the solution to the feasible set.  `projectfunc` should implement this.

1694:   The VI solvers require special evaluation of the function norm such that the norm is only calculated
1695:   on the inactive set.  This should be implemented by `normfunc`.

1697:   The VI solvers further require special evaluation of the directional derivative (when assuming that there exists some $G(x)$
1698:   for which the `SNESFunctionFn` $F(x) = grad G(x)$) such that it is only calculated on the inactive set.
1699:   This should be implemented by `dirderivfunc`.

1701: .seealso: [](ch_snes), `SNES`, `SNESLineSearch`, `SNESLineSearchGetVIFunctions()`, `SNESLineSearchSetPostCheck()`, `SNESLineSearchSetPreCheck()`,
1702:           `SNESLineSearchVIProjectFn`, `SNESLineSearchVINormFn`, `SNESLineSearchVIDirDerivFn`
1703: @*/
1704: PetscErrorCode SNESLineSearchSetVIFunctions(SNESLineSearch linesearch, SNESLineSearchVIProjectFn *projectfunc, SNESLineSearchVINormFn *normfunc, SNESLineSearchVIDirDerivFn *dirderivfunc)
1705: {
1706:   PetscFunctionBegin;
1708:   if (projectfunc) linesearch->ops->viproject = projectfunc;
1709:   if (normfunc) linesearch->ops->vinorm = normfunc;
1710:   if (dirderivfunc) linesearch->ops->vidirderiv = dirderivfunc;
1711:   PetscFunctionReturn(PETSC_SUCCESS);
1712: }

1714: /*@C
1715:   SNESLineSearchGetVIFunctions - Sets VI-specific functions for line search computation.

1717:   Not Collective

1719:   Input Parameter:
1720: . linesearch - the line search context, obtain with `SNESGetLineSearch()`

1722:   Output Parameters:
1723: + projectfunc  - function for projecting the function to the bounds, see `SNESLineSearchVIProjectFn` for calling sequence
1724: . normfunc     - function for computing the norm of an active set, see `SNESLineSearchVINormFn ` for calling sequence
1725: - dirderivfunc - function for computing the directional derivative of an active set, see `SNESLineSearchVIDirDerivFn` for calling sequence

1727:   Level: advanced

1729: .seealso: [](ch_snes), `SNES`, `SNESLineSearch`, `SNESLineSearchSetVIFunctions()`, `SNESLineSearchGetPostCheck()`, `SNESLineSearchGetPreCheck()`,
1730:           `SNESLineSearchVIProjectFn`, `SNESLineSearchVINormFn`
1731: @*/
1732: PetscErrorCode SNESLineSearchGetVIFunctions(SNESLineSearch linesearch, SNESLineSearchVIProjectFn **projectfunc, SNESLineSearchVINormFn **normfunc, SNESLineSearchVIDirDerivFn **dirderivfunc)
1733: {
1734:   PetscFunctionBegin;
1735:   if (projectfunc) *projectfunc = linesearch->ops->viproject;
1736:   if (normfunc) *normfunc = linesearch->ops->vinorm;
1737:   if (dirderivfunc) *dirderivfunc = linesearch->ops->vidirderiv;
1738:   PetscFunctionReturn(PETSC_SUCCESS);
1739: }

1741: /*@C
1742:   SNESLineSearchRegister - register a line search type `SNESLineSearchType`

1744:   Logically Collective, No Fortran Support

1746:   Input Parameters:
1747: + sname    - name of the `SNESLineSearchType()`
1748: - function - the creation function for that type

1750:   Calling sequence of `function`:
1751: . ls - the line search context

1753:   Level: advanced

1755: .seealso: [](ch_snes), `SNES`, `SNESLineSearch`, `SNESLineSearchType`, `SNESLineSearchSetType()`
1756: @*/
1757: PetscErrorCode SNESLineSearchRegister(const char sname[], PetscErrorCode (*function)(SNESLineSearch ls))
1758: {
1759:   PetscFunctionBegin;
1760:   PetscCall(SNESInitializePackage());
1761:   PetscCall(PetscFunctionListAdd(&SNESLineSearchList, sname, function));
1762:   PetscFunctionReturn(PETSC_SUCCESS);
1763: }