Actual source code: taolinesearch.c

petsc-master 2019-11-16
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  1:  #include <petsctaolinesearch.h>
  2:  #include <petsc/private/taolinesearchimpl.h>

  4: PetscFunctionList TaoLineSearchList = NULL;

  6: PetscClassId TAOLINESEARCH_CLASSID=0;

  8: PetscLogEvent TAOLINESEARCH_Apply;
  9: PetscLogEvent TAOLINESEARCH_Eval;

 11: /*@C
 12:    TaoLineSearchViewFromOptions - View from Options

 14:    Collective on TaoLineSearch

 16:    Input Parameters:
 17: +  A - the Tao context
 18: .  obj - Optional object
 19: -  name - command line option

 21:    Level: intermediate
 22: .seealso:  TaoLineSearch, TaoLineSearchView, PetscObjectViewFromOptions(), TaoLineSearchCreate()
 23: @*/
 24: PetscErrorCode  TaoLineSearchViewFromOptions(TaoLineSearch A,PetscObject obj,const char name[])
 25: {

 30:   PetscObjectViewFromOptions((PetscObject)A,obj,name);
 31:   return(0);
 32: }

 34: /*@C
 35:   TaoLineSearchView - Prints information about the TaoLineSearch

 37:   Collective on TaoLineSearch

 39:   InputParameters:
 40: + ls - the Tao context
 41: - viewer - visualization context

 43:   Options Database Key:
 44: . -tao_ls_view - Calls TaoLineSearchView() at the end of each line search

 46:   Notes:
 47:   The available visualization contexts include
 48: +     PETSC_VIEWER_STDOUT_SELF - standard output (default)
 49: -     PETSC_VIEWER_STDOUT_WORLD - synchronized standard
 50:          output where only the first processor opens
 51:          the file.  All other processors send their
 52:          data to the first processor to print.

 54:   Level: beginner

 56: .seealso: PetscViewerASCIIOpen()
 57: @*/

 59: PetscErrorCode TaoLineSearchView(TaoLineSearch ls, PetscViewer viewer)
 60: {
 61:   PetscErrorCode          ierr;
 62:   PetscBool               isascii, isstring;
 63:   TaoLineSearchType       type;

 67:   if (!viewer) {
 68:     PetscViewerASCIIGetStdout(((PetscObject)ls)->comm, &viewer);
 69:   }

 73:   PetscObjectTypeCompare((PetscObject)viewer,PETSCVIEWERASCII,&isascii);
 74:   PetscObjectTypeCompare((PetscObject)viewer,PETSCVIEWERSTRING,&isstring);
 75:   if (isascii) {
 76:     PetscObjectPrintClassNamePrefixType((PetscObject)ls, viewer);
 77:     if (ls->ops->view) {
 78:       PetscViewerASCIIPushTab(viewer);
 79:       (*ls->ops->view)(ls,viewer);
 80:       PetscViewerASCIIPopTab(viewer);
 81:     }
 82:     PetscViewerASCIIPushTab(viewer);
 83:     PetscViewerASCIIPrintf(viewer,"maximum function evaluations=%D\n",ls->max_funcs);
 84:     PetscViewerASCIIPrintf(viewer,"tolerances: ftol=%g, rtol=%g, gtol=%g\n",(double)ls->ftol,(double)ls->rtol,(double)ls->gtol);
 85:     PetscViewerASCIIPrintf(viewer,"total number of function evaluations=%D\n",ls->nfeval);
 86:     PetscViewerASCIIPrintf(viewer,"total number of gradient evaluations=%D\n",ls->ngeval);
 87:     PetscViewerASCIIPrintf(viewer,"total number of function/gradient evaluations=%D\n",ls->nfgeval);

 89:     if (ls->bounded) {
 90:       PetscViewerASCIIPrintf(viewer,"using variable bounds\n");
 91:     }
 92:     PetscViewerASCIIPrintf(viewer,"Termination reason: %d\n",(int)ls->reason);
 93:     PetscViewerASCIIPopTab(viewer);
 94:   } else if (isstring) {
 95:     TaoLineSearchGetType(ls,&type);
 96:     PetscViewerStringSPrintf(viewer," %-3.3s",type);
 97:   }
 98:   return(0);
 99: }

101: /*@C
102:   TaoLineSearchCreate - Creates a TAO Line Search object.  Algorithms in TAO that use
103:   line-searches will automatically create one.

105:   Collective

107:   Input Parameter:
108: . comm - MPI communicator

110:   Output Parameter:
111: . newls - the new TaoLineSearch context

113:   Available methods include:
114: + more-thuente
115: . gpcg
116: - unit - Do not perform any line search


119:    Options Database Keys:
120: .   -tao_ls_type - select which method TAO should use

122:    Level: beginner

124: .seealso: TaoLineSearchSetType(), TaoLineSearchApply(), TaoLineSearchDestroy()
125: @*/

127: PetscErrorCode TaoLineSearchCreate(MPI_Comm comm, TaoLineSearch *newls)
128: {
130:   TaoLineSearch  ls;

134:   *newls = NULL;

136:   TaoLineSearchInitializePackage();

138:   PetscHeaderCreate(ls,TAOLINESEARCH_CLASSID,"TaoLineSearch","Linesearch","Tao",comm,TaoLineSearchDestroy,TaoLineSearchView);
139:   ls->bounded = 0;
140:   ls->max_funcs=30;
141:   ls->ftol = 0.0001;
142:   ls->gtol = 0.9;
143: #if defined(PETSC_USE_REAL_SINGLE)
144:   ls->rtol = 1.0e-5;
145: #else
146:   ls->rtol = 1.0e-10;
147: #endif
148:   ls->stepmin=1.0e-20;
149:   ls->stepmax=1.0e+20;
150:   ls->step=1.0;
151:   ls->nfeval=0;
152:   ls->ngeval=0;
153:   ls->nfgeval=0;

155:   ls->ops->computeobjective=0;
156:   ls->ops->computegradient=0;
157:   ls->ops->computeobjectiveandgradient=0;
158:   ls->ops->computeobjectiveandgts=0;
159:   ls->ops->setup=0;
160:   ls->ops->apply=0;
161:   ls->ops->view=0;
162:   ls->ops->setfromoptions=0;
163:   ls->ops->reset=0;
164:   ls->ops->destroy=0;
165:   ls->ops->monitor=0;
166:   ls->usemonitor=PETSC_FALSE;
167:   ls->setupcalled=PETSC_FALSE;
168:   ls->usetaoroutines=PETSC_FALSE;
169:   *newls = ls;
170:   return(0);
171: }

173: /*@
174:   TaoLineSearchSetUp - Sets up the internal data structures for the later use
175:   of a Tao solver

177:   Collective on ls

179:   Input Parameters:
180: . ls - the TaoLineSearch context

182:   Notes:
183:   The user will not need to explicitly call TaoLineSearchSetUp(), as it will
184:   automatically be called in TaoLineSearchSolve().  However, if the user
185:   desires to call it explicitly, it should come after TaoLineSearchCreate()
186:   but before TaoLineSearchApply().

188:   Level: developer

190: .seealso: TaoLineSearchCreate(), TaoLineSearchApply()
191: @*/

193: PetscErrorCode TaoLineSearchSetUp(TaoLineSearch ls)
194: {
196:   const char     *default_type=TAOLINESEARCHMT;
197:   PetscBool      flg;

201:   if (ls->setupcalled) return(0);
202:   if (!((PetscObject)ls)->type_name) {
203:     TaoLineSearchSetType(ls,default_type);
204:   }
205:   if (ls->ops->setup) {
206:     (*ls->ops->setup)(ls);
207:   }
208:   if (ls->usetaoroutines) {
209:     TaoIsObjectiveDefined(ls->tao,&flg);
210:     ls->hasobjective = flg;
211:     TaoIsGradientDefined(ls->tao,&flg);
212:     ls->hasgradient = flg;
213:     TaoIsObjectiveAndGradientDefined(ls->tao,&flg);
214:     ls->hasobjectiveandgradient = flg;
215:   } else {
216:     if (ls->ops->computeobjective) {
217:       ls->hasobjective = PETSC_TRUE;
218:     } else {
219:       ls->hasobjective = PETSC_FALSE;
220:     }
221:     if (ls->ops->computegradient) {
222:       ls->hasgradient = PETSC_TRUE;
223:     } else {
224:       ls->hasgradient = PETSC_FALSE;
225:     }
226:     if (ls->ops->computeobjectiveandgradient) {
227:       ls->hasobjectiveandgradient = PETSC_TRUE;
228:     } else {
229:       ls->hasobjectiveandgradient = PETSC_FALSE;
230:     }
231:   }
232:   ls->setupcalled = PETSC_TRUE;
233:   return(0);
234: }

236: /*@
237:   TaoLineSearchReset - Some line searches may carry state information
238:   from one TaoLineSearchApply() to the next.  This function resets this
239:   state information.

241:   Collective on TaoLineSearch

243:   Input Parameter:
244: . ls - the TaoLineSearch context

246:   Level: developer

248: .seealso: TaoLineSearchCreate(), TaoLineSearchApply()
249: @*/
250: PetscErrorCode TaoLineSearchReset(TaoLineSearch ls)
251: {

256:   if (ls->ops->reset) {
257:     (*ls->ops->reset)(ls);
258:   }
259:   return(0);
260: }

262: /*@
263:   TaoLineSearchDestroy - Destroys the TAO context that was created with
264:   TaoLineSearchCreate()

266:   Collective on TaoLineSearch

268:   Input Parameter
269: . ls - the TaoLineSearch context

271:   Level: beginner

273: .seealse: TaoLineSearchCreate(), TaoLineSearchSolve()
274: @*/
275: PetscErrorCode TaoLineSearchDestroy(TaoLineSearch *ls)
276: {

280:   if (!*ls) return(0);
282:   if (--((PetscObject)*ls)->refct > 0) {*ls=0; return(0);}
283:   VecDestroy(&(*ls)->stepdirection);
284:   VecDestroy(&(*ls)->start_x);
285:   if ((*ls)->ops->destroy) {
286:     (*(*ls)->ops->destroy)(*ls);
287:   }
288:   if ((*ls)->usemonitor) {
289:     PetscViewerDestroy(&(*ls)->viewer);
290:   }
291:   PetscHeaderDestroy(ls);
292:   return(0);
293: }

295: /*@
296:   TaoLineSearchApply - Performs a line-search in a given step direction.  Criteria for acceptable step length depends on the line-search algorithm chosen

298:   Collective on TaoLineSearch

300:   Input Parameters:
301: + ls - the Tao context
302: . x - The current solution (on output x contains the new solution determined by the line search)
303: . f - objective function value at current solution (on output contains the objective function value at new solution)
304: . g - gradient evaluated at x (on output contains the gradient at new solution)
305: - s - search direction

307:   Output Parameters:
308: + x - new solution
309: . f - objective function value at x
310: . g - gradient vector at x
311: . steplength - scalar multiplier of s used ( x = x0 + steplength * x )
312: - reason - reason why the line-search stopped

314:   reason will be set to one of:

316: + TAOLINESEARCH_FAILED_ASCENT - initial line search step * g is not descent direction
317: . TAOLINESEARCH_FAILED_INFORNAN - function evaluation gives Inf or Nan value
318: . TAOLINESEARCH_FAILED_BADPARAMETER - negative value set as parameter
319: . TAOLINESEARCH_HALTED_MAXFCN - maximum number of function evaluation reached
320: . TAOLINESEARCH_HALTED_UPPERBOUND - step is at upper bound
321: . TAOLINESEARCH_HALTED_LOWERBOUND - step is at lower bound
322: . TAOLINESEARCH_HALTED_RTOL - range of uncertainty is smaller than given tolerance
323: . TAOLINESEARCH_HALTED_USER - user can set this reason to stop line search
324: . TAOLINESEARCH_HALTED_OTHER - any other reason
325: - TAOLINESEARCH_SUCCESS - successful line search

327:   Note:
328:   The algorithm developer must set up the TaoLineSearch with calls to
329:   TaoLineSearchSetObjectiveRoutine() and TaoLineSearchSetGradientRoutine(), TaoLineSearchSetObjectiveAndGradientRoutine(), or TaoLineSearchUseTaoRoutines()

331:   Note:
332:   You may or may not need to follow this with a call to
333:   TaoAddLineSearchCounts(), depending on whether you want these
334:   evaluations to count toward the total function/gradient evaluations.

336:   Level: beginner

338:   .seealso: TaoLineSearchCreate(), TaoLineSearchSetType(), TaoLineSearchSetInitialStepLength(), TaoAddLineSearchCounts()
339:  @*/

341: PetscErrorCode TaoLineSearchApply(TaoLineSearch ls, Vec x, PetscReal *f, Vec g, Vec s, PetscReal *steplength, TaoLineSearchConvergedReason *reason)
342: {
344:   PetscInt       low1,low2,low3,high1,high2,high3;

347:   *reason = TAOLINESEARCH_CONTINUE_ITERATING;
357:   VecGetOwnershipRange(x, &low1, &high1);
358:   VecGetOwnershipRange(g, &low2, &high2);
359:   VecGetOwnershipRange(s, &low3, &high3);
360:   if (low1!= low2 || low1!= low3 || high1!= high2 || high1!= high3) SETERRQ(PETSC_COMM_SELF,PETSC_ERR_ARG_SIZ,"Incompatible vector local lengths");

362:   PetscObjectReference((PetscObject)s);
363:   VecDestroy(&ls->stepdirection);
364:   ls->stepdirection = s;

366:   TaoLineSearchSetUp(ls);
367:   if (!ls->ops->apply) SETERRQ(PetscObjectComm((PetscObject)ls),PETSC_ERR_ARG_WRONGSTATE,"Line Search Object does not have 'apply' routine");
368:   ls->nfeval=0;
369:   ls->ngeval=0;
370:   ls->nfgeval=0;
371:   /* Check parameter values */
372:   if (ls->ftol < 0.0) {
373:     PetscInfo1(ls,"Bad Line Search Parameter: ftol (%g) < 0\n",(double)ls->ftol);
374:     *reason=TAOLINESEARCH_FAILED_BADPARAMETER;
375:   }
376:   if (ls->rtol < 0.0) {
377:     PetscInfo1(ls,"Bad Line Search Parameter: rtol (%g) < 0\n",(double)ls->rtol);
378:     *reason=TAOLINESEARCH_FAILED_BADPARAMETER;
379:   }
380:   if (ls->gtol < 0.0) {
381:     PetscInfo1(ls,"Bad Line Search Parameter: gtol (%g) < 0\n",(double)ls->gtol);
382:     *reason=TAOLINESEARCH_FAILED_BADPARAMETER;
383:   }
384:   if (ls->stepmin < 0.0) {
385:     PetscInfo1(ls,"Bad Line Search Parameter: stepmin (%g) < 0\n",(double)ls->stepmin);
386:     *reason=TAOLINESEARCH_FAILED_BADPARAMETER;
387:   }
388:   if (ls->stepmax < ls->stepmin) {
389:     PetscInfo2(ls,"Bad Line Search Parameter: stepmin (%g) > stepmax (%g)\n",(double)ls->stepmin,(double)ls->stepmax);
390:     *reason=TAOLINESEARCH_FAILED_BADPARAMETER;
391:   }
392:   if (ls->max_funcs < 0) {
393:     PetscInfo1(ls,"Bad Line Search Parameter: max_funcs (%D) < 0\n",ls->max_funcs);
394:     *reason=TAOLINESEARCH_FAILED_BADPARAMETER;
395:   }
396:   if (PetscIsInfOrNanReal(*f)) {
397:     PetscInfo1(ls,"Initial Line Search Function Value is Inf or Nan (%g)\n",(double)*f);
398:     *reason=TAOLINESEARCH_FAILED_INFORNAN;
399:   }

401:   PetscObjectReference((PetscObject)x);
402:   VecDestroy(&ls->start_x);
403:   ls->start_x = x;

405:   PetscLogEventBegin(TAOLINESEARCH_Apply,ls,0,0,0);
406:   (*ls->ops->apply)(ls,x,f,g,s);
407:   PetscLogEventEnd(TAOLINESEARCH_Apply, ls, 0,0,0);
408:   *reason=ls->reason;
409:   ls->new_f = *f;

411:   if (steplength) {
412:     *steplength=ls->step;
413:   }

415:   TaoLineSearchViewFromOptions(ls,NULL,"-tao_ls_view");
416:   return(0);
417: }

419: /*@C
420:    TaoLineSearchSetType - Sets the algorithm used in a line search

422:    Collective on TaoLineSearch

424:    Input Parameters:
425: +  ls - the TaoLineSearch context
426: -  type - a known method

428:   Available methods include:
429: + more-thuente
430: . gpcg
431: - unit - Do not perform any line search


434:   Options Database Keys:
435: .   -tao_ls_type - select which method TAO should use

437:   Level: beginner


440: .seealso: TaoLineSearchCreate(), TaoLineSearchGetType(), TaoLineSearchApply()

442: @*/

444: PetscErrorCode TaoLineSearchSetType(TaoLineSearch ls, TaoLineSearchType type)
445: {
447:   PetscErrorCode (*r)(TaoLineSearch);
448:   PetscBool      flg;

453:   PetscObjectTypeCompare((PetscObject)ls, type, &flg);
454:   if (flg) return(0);

456:   PetscFunctionListFind(TaoLineSearchList,type, (void (**)(void)) &r);
457:   if (!r) SETERRQ1(PetscObjectComm((PetscObject)ls),PETSC_ERR_ARG_UNKNOWN_TYPE,"Unable to find requested TaoLineSearch type %s",type);
458:   if (ls->ops->destroy) {
459:     (*(ls)->ops->destroy)(ls);
460:   }
461:   ls->max_funcs=30;
462:   ls->ftol = 0.0001;
463:   ls->gtol = 0.9;
464: #if defined(PETSC_USE_REAL_SINGLE)
465:   ls->rtol = 1.0e-5;
466: #else
467:   ls->rtol = 1.0e-10;
468: #endif
469:   ls->stepmin=1.0e-20;
470:   ls->stepmax=1.0e+20;

472:   ls->nfeval=0;
473:   ls->ngeval=0;
474:   ls->nfgeval=0;
475:   ls->ops->setup=0;
476:   ls->ops->apply=0;
477:   ls->ops->view=0;
478:   ls->ops->setfromoptions=0;
479:   ls->ops->destroy=0;
480:   ls->setupcalled = PETSC_FALSE;
481:   (*r)(ls);
482:   PetscObjectChangeTypeName((PetscObject)ls, type);
483:   return(0);
484: }

486: /*@C
487:   TaoLineSearchMonitor - Monitor the line search steps. This routine will otuput the
488:   iteration number, step length, and function value before calling the implementation 
489:   specific monitor.

491:    Input Parameters:
492: +  ls - the TaoLineSearch context
493: .  its - the current iterate number (>=0)
494: .  f - the current objective function value
495: -  step - the step length

497:    Options Database Key:
498: .  -tao_ls_monitor - Use the default monitor, which prints statistics to standard output

500:    Level: developer

502: @*/
503: PetscErrorCode TaoLineSearchMonitor(TaoLineSearch ls, PetscInt its, PetscReal f, PetscReal step)
504: {
506:   PetscInt       tabs;

510:   if (ls->usemonitor) {
511:     PetscViewerASCIIGetTab(ls->viewer, &tabs);
512:     PetscViewerASCIISetTab(ls->viewer, ((PetscObject)ls)->tablevel);
513:     PetscViewerASCIIPrintf(ls->viewer, "%3D LS", its);
514:     PetscViewerASCIIPrintf(ls->viewer, "  Function value: %g,", (double)f);
515:     PetscViewerASCIIPrintf(ls->viewer, "  Step length: %g\n", (double)step);
516:     if (ls->ops->monitor && its > 0) {
517:       PetscViewerASCIISetTab(ls->viewer, ((PetscObject)ls)->tablevel + 3);
518:       (*ls->ops->monitor)(ls);
519:     }
520:     PetscViewerASCIISetTab(ls->viewer, tabs);
521:   }
522:   return(0);
523: }

525: /*@
526:   TaoLineSearchSetFromOptions - Sets various TaoLineSearch parameters from user
527:   options.

529:   Collective on TaoLineSearch

531:   Input Paremeter:
532: . ls - the TaoLineSearch context

534:   Options Database Keys:
535: + -tao_ls_type <type> - The algorithm that TAO uses (more-thuente, gpcg, unit)
536: . -tao_ls_ftol <tol> - tolerance for sufficient decrease
537: . -tao_ls_gtol <tol> - tolerance for curvature condition
538: . -tao_ls_rtol <tol> - relative tolerance for acceptable step
539: . -tao_ls_stepmin <step> - minimum steplength allowed
540: . -tao_ls_stepmax <step> - maximum steplength allowed
541: . -tao_ls_max_funcs <n> - maximum number of function evaluations allowed
542: - -tao_ls_view - display line-search results to standard output

544:   Level: beginner
545: @*/
546: PetscErrorCode TaoLineSearchSetFromOptions(TaoLineSearch ls)
547: {
549:   const char     *default_type=TAOLINESEARCHMT;
550:   char           type[256],monfilename[PETSC_MAX_PATH_LEN];
551:   PetscViewer    monviewer;
552:   PetscBool      flg;

556:   PetscObjectOptionsBegin((PetscObject)ls);
557:   if (((PetscObject)ls)->type_name) {
558:     default_type = ((PetscObject)ls)->type_name;
559:   }
560:   /* Check for type from options */
561:   PetscOptionsFList("-tao_ls_type","Tao Line Search type","TaoLineSearchSetType",TaoLineSearchList,default_type,type,256,&flg);
562:   if (flg) {
563:     TaoLineSearchSetType(ls,type);
564:   } else if (!((PetscObject)ls)->type_name) {
565:     TaoLineSearchSetType(ls,default_type);
566:   }

568:   PetscOptionsInt("-tao_ls_max_funcs","max function evals in line search","",ls->max_funcs,&ls->max_funcs,NULL);
569:   PetscOptionsReal("-tao_ls_ftol","tol for sufficient decrease","",ls->ftol,&ls->ftol,NULL);
570:   PetscOptionsReal("-tao_ls_gtol","tol for curvature condition","",ls->gtol,&ls->gtol,NULL);
571:   PetscOptionsReal("-tao_ls_rtol","relative tol for acceptable step","",ls->rtol,&ls->rtol,NULL);
572:   PetscOptionsReal("-tao_ls_stepmin","lower bound for step","",ls->stepmin,&ls->stepmin,NULL);
573:   PetscOptionsReal("-tao_ls_stepmax","upper bound for step","",ls->stepmax,&ls->stepmax,NULL);
574:   PetscOptionsString("-tao_ls_monitor","enable the basic monitor","TaoLineSearchSetMonitor","stdout",monfilename,PETSC_MAX_PATH_LEN,&flg);
575:   if (flg) {
576:     PetscViewerASCIIOpen(PetscObjectComm((PetscObject)ls),monfilename,&monviewer);
577:     ls->viewer = monviewer;
578:     ls->usemonitor = PETSC_TRUE;
579:   }
580:   if (ls->ops->setfromoptions) {
581:     (*ls->ops->setfromoptions)(PetscOptionsObject,ls);
582:   }
583:   PetscOptionsEnd();
584:   return(0);
585: }

587: /*@C
588:   TaoLineSearchGetType - Gets the current line search algorithm

590:   Not Collective

592:   Input Parameter:
593: . ls - the TaoLineSearch context

595:   Output Paramter:
596: . type - the line search algorithm in effect

598:   Level: developer

600: @*/
601: PetscErrorCode TaoLineSearchGetType(TaoLineSearch ls, TaoLineSearchType *type)
602: {
606:   *type = ((PetscObject)ls)->type_name;
607:   return(0);
608: }

610: /*@
611:   TaoLineSearchGetNumberFunctionEvaluations - Gets the number of function and gradient evaluation
612:   routines used by the line search in last application (not cumulative).

614:   Not Collective

616:   Input Parameter:
617: . ls - the TaoLineSearch context

619:   Output Parameters:
620: + nfeval   - number of function evaluations
621: . ngeval   - number of gradient evaluations
622: - nfgeval  - number of function/gradient evaluations

624:   Level: intermediate

626:   Note:
627:   If the line search is using the Tao objective and gradient
628:   routines directly (see TaoLineSearchUseTaoRoutines()), then TAO
629:   is already counting the number of evaluations.

631: @*/
632: PetscErrorCode TaoLineSearchGetNumberFunctionEvaluations(TaoLineSearch ls, PetscInt *nfeval, PetscInt *ngeval, PetscInt *nfgeval)
633: {
636:   *nfeval = ls->nfeval;
637:   *ngeval = ls->ngeval;
638:   *nfgeval = ls->nfgeval;
639:   return(0);
640: }

642: /*@
643:   TaoLineSearchIsUsingTaoRoutines - Checks whether the line search is using
644:   Tao evaluation routines.

646:   Not Collective

648:   Input Parameter:
649: . ls - the TaoLineSearch context

651:   Output Parameter:
652: . flg - PETSC_TRUE if the line search is using Tao evaluation routines,
653:         otherwise PETSC_FALSE

655:   Level: developer
656: @*/
657: PetscErrorCode TaoLineSearchIsUsingTaoRoutines(TaoLineSearch ls, PetscBool *flg)
658: {
661:   *flg = ls->usetaoroutines;
662:   return(0);
663: }

665: /*@C
666:   TaoLineSearchSetObjectiveRoutine - Sets the function evaluation routine for the line search

668:   Logically Collective on TaoLineSearch

670:   Input Parameter:
671: + ls - the TaoLineSearch context
672: . func - the objective function evaluation routine
673: - ctx - the (optional) user-defined context for private data

675:   Calling sequence of func:
676: $      func (TaoLinesearch ls, Vec x, PetscReal *f, void *ctx);

678: + x - input vector
679: . f - function value
680: - ctx (optional) user-defined context

682:   Level: beginner

684:   Note:
685:   Use this routine only if you want the line search objective
686:   evaluation routine to be different from the Tao's objective
687:   evaluation routine. If you use this routine you must also set
688:   the line search gradient and/or function/gradient routine.

690:   Note:
691:   Some algorithms (lcl, gpcg) set their own objective routine for the
692:   line search, application programmers should be wary of overriding the
693:   default objective routine.

695: .seealso: TaoLineSearchCreate(), TaoLineSearchSetGradientRoutine(), TaoLineSearchSetObjectiveAndGradientRoutine(), TaoLineSearchUseTaoRoutines()
696: @*/
697: PetscErrorCode TaoLineSearchSetObjectiveRoutine(TaoLineSearch ls, PetscErrorCode(*func)(TaoLineSearch ls, Vec x, PetscReal*, void*), void *ctx)
698: {

702:   ls->ops->computeobjective=func;
703:   if (ctx) ls->userctx_func=ctx;
704:   ls->usetaoroutines=PETSC_FALSE;
705:   return(0);
706: }

708: /*@C
709:   TaoLineSearchSetGradientRoutine - Sets the gradient evaluation routine for the line search

711:   Logically Collective on TaoLineSearch

713:   Input Parameter:
714: + ls - the TaoLineSearch context
715: . func - the gradient evaluation routine
716: - ctx - the (optional) user-defined context for private data

718:   Calling sequence of func:
719: $      func (TaoLinesearch ls, Vec x, Vec g, void *ctx);

721: + x - input vector
722: . g - gradient vector
723: - ctx (optional) user-defined context

725:   Level: beginner

727:   Note:
728:   Use this routine only if you want the line search gradient
729:   evaluation routine to be different from the Tao's gradient
730:   evaluation routine. If you use this routine you must also set
731:   the line search function and/or function/gradient routine.

733:   Note:
734:   Some algorithms (lcl, gpcg) set their own gradient routine for the
735:   line search, application programmers should be wary of overriding the
736:   default gradient routine.

738: .seealso: TaoLineSearchCreate(), TaoLineSearchSetObjectiveRoutine(), TaoLineSearchSetObjectiveAndGradientRoutine(), TaoLineSearchUseTaoRoutines()
739: @*/
740: PetscErrorCode TaoLineSearchSetGradientRoutine(TaoLineSearch ls, PetscErrorCode(*func)(TaoLineSearch ls, Vec x, Vec g, void*), void *ctx)
741: {
744:   ls->ops->computegradient=func;
745:   if (ctx) ls->userctx_grad=ctx;
746:   ls->usetaoroutines=PETSC_FALSE;
747:   return(0);
748: }

750: /*@C
751:   TaoLineSearchSetObjectiveAndGradientRoutine - Sets the objective/gradient evaluation routine for the line search

753:   Logically Collective on TaoLineSearch

755:   Input Parameter:
756: + ls - the TaoLineSearch context
757: . func - the objective and gradient evaluation routine
758: - ctx - the (optional) user-defined context for private data

760:   Calling sequence of func:
761: $      func (TaoLinesearch ls, Vec x, PetscReal *f, Vec g, void *ctx);

763: + x - input vector
764: . f - function value
765: . g - gradient vector
766: - ctx (optional) user-defined context

768:   Level: beginner

770:   Note:
771:   Use this routine only if you want the line search objective and gradient
772:   evaluation routines to be different from the Tao's objective
773:   and gradient evaluation routines.

775:   Note:
776:   Some algorithms (lcl, gpcg) set their own objective routine for the
777:   line search, application programmers should be wary of overriding the
778:   default objective routine.

780: .seealso: TaoLineSearchCreate(), TaoLineSearchSetObjectiveRoutine(), TaoLineSearchSetGradientRoutine(), TaoLineSearchUseTaoRoutines()
781: @*/
782: PetscErrorCode TaoLineSearchSetObjectiveAndGradientRoutine(TaoLineSearch ls, PetscErrorCode(*func)(TaoLineSearch ls, Vec x, PetscReal *, Vec g, void*), void *ctx)
783: {
786:   ls->ops->computeobjectiveandgradient=func;
787:   if (ctx) ls->userctx_funcgrad=ctx;
788:   ls->usetaoroutines = PETSC_FALSE;
789:   return(0);
790: }

792: /*@C
793:   TaoLineSearchSetObjectiveAndGTSRoutine - Sets the objective and
794:   (gradient'*stepdirection) evaluation routine for the line search.
795:   Sometimes it is more efficient to compute the inner product of the gradient
796:   and the step direction than it is to compute the gradient, and this is all
797:   the line search typically needs of the gradient.

799:   Logically Collective on TaoLineSearch

801:   Input Parameter:
802: + ls - the TaoLineSearch context
803: . func - the objective and gradient evaluation routine
804: - ctx - the (optional) user-defined context for private data

806:   Calling sequence of func:
807: $      func (TaoLinesearch ls, Vec x, PetscReal *f, PetscReal *gts, void *ctx);

809: + x - input vector
810: . s - step direction
811: . f - function value
812: . gts - inner product of gradient and step direction vectors
813: - ctx (optional) user-defined context

815:   Note: The gradient will still need to be computed at the end of the line
816:   search, so you will still need to set a line search gradient evaluation
817:   routine

819:   Note: Bounded line searches (those used in bounded optimization algorithms)
820:   don't use g's directly, but rather (g'x - g'x0)/steplength.  You can get the
821:   x0 and steplength with TaoLineSearchGetStartingVector() and TaoLineSearchGetStepLength()

823:   Level: advanced

825:   Note:
826:   Some algorithms (lcl, gpcg) set their own objective routine for the
827:   line search, application programmers should be wary of overriding the
828:   default objective routine.

830: .seealso: TaoLineSearchCreate(), TaoLineSearchSetObjective(), TaoLineSearchSetGradient(), TaoLineSearchUseTaoRoutines()
831: @*/
832: PetscErrorCode TaoLineSearchSetObjectiveAndGTSRoutine(TaoLineSearch ls, PetscErrorCode(*func)(TaoLineSearch ls, Vec x, Vec s, PetscReal *, PetscReal *, void*), void *ctx)
833: {
836:   ls->ops->computeobjectiveandgts=func;
837:   if (ctx) ls->userctx_funcgts=ctx;
838:   ls->usegts = PETSC_TRUE;
839:   ls->usetaoroutines=PETSC_FALSE;
840:   return(0);
841: }

843: /*@C
844:   TaoLineSearchUseTaoRoutines - Informs the TaoLineSearch to use the
845:   objective and gradient evaluation routines from the given Tao object.

847:   Logically Collective on TaoLineSearch

849:   Input Parameter:
850: + ls - the TaoLineSearch context
851: - ts - the Tao context with defined objective/gradient evaluation routines

853:   Level: developer

855: .seealso: TaoLineSearchCreate()
856: @*/
857: PetscErrorCode TaoLineSearchUseTaoRoutines(TaoLineSearch ls, Tao ts)
858: {
862:   ls->tao = ts;
863:   ls->usetaoroutines=PETSC_TRUE;
864:   return(0);
865: }

867: /*@
868:   TaoLineSearchComputeObjective - Computes the objective function value at a given point

870:   Collective on TaoLineSearch

872:   Input Parameters:
873: + ls - the TaoLineSearch context
874: - x - input vector

876:   Output Parameter:
877: . f - Objective value at X

879:   Notes:
880:     TaoLineSearchComputeObjective() is typically used within line searches
881:   so most users would not generally call this routine themselves.

883:   Level: developer

885: .seealso: TaoLineSearchComputeGradient(), TaoLineSearchComputeObjectiveAndGradient(), TaoLineSearchSetObjectiveRoutine()
886: @*/
887: PetscErrorCode TaoLineSearchComputeObjective(TaoLineSearch ls, Vec x, PetscReal *f)
888: {
890:   Vec            gdummy;
891:   PetscReal      gts;

898:   if (ls->usetaoroutines) {
899:     TaoComputeObjective(ls->tao,x,f);
900:   } else {
901:     if (!ls->ops->computeobjective && !ls->ops->computeobjectiveandgradient && !ls->ops->computeobjectiveandgts) SETERRQ(PetscObjectComm((PetscObject)ls),PETSC_ERR_ARG_WRONGSTATE,"Line Search does not have objective function set");
902:     PetscLogEventBegin(TAOLINESEARCH_Eval,ls,0,0,0);
903:     PetscStackPush("TaoLineSearch user objective routine");
904:     if (ls->ops->computeobjective) {
905:       (*ls->ops->computeobjective)(ls,x,f,ls->userctx_func);
906:     } else if (ls->ops->computeobjectiveandgradient) {
907:       VecDuplicate(x,&gdummy);
908:       (*ls->ops->computeobjectiveandgradient)(ls,x,f,gdummy,ls->userctx_funcgrad);
909:       VecDestroy(&gdummy);
910:     } else {
911:       (*ls->ops->computeobjectiveandgts)(ls,x,ls->stepdirection,f,&gts,ls->userctx_funcgts);
912:     }
913:     PetscStackPop;
914:     PetscLogEventEnd(TAOLINESEARCH_Eval,ls,0,0,0);
915:   }
916:   ls->nfeval++;
917:   return(0);
918: }

920: /*@
921:   TaoLineSearchComputeObjectiveAndGradient - Computes the objective function value at a given point

923:   Collective on Tao

925:   Input Parameters:
926: + ls - the TaoLineSearch context
927: - x - input vector

929:   Output Parameter:
930: + f - Objective value at X
931: - g - Gradient vector at X

933:   Notes:
934:     TaoLineSearchComputeObjectiveAndGradient() is typically used within line searches
935:   so most users would not generally call this routine themselves.

937:   Level: developer

939: .seealso: TaoLineSearchComputeGradient(), TaoLineSearchComputeObjectiveAndGradient(), TaoLineSearchSetObjectiveRoutine()
940: @*/
941: PetscErrorCode TaoLineSearchComputeObjectiveAndGradient(TaoLineSearch ls, Vec x, PetscReal *f, Vec g)
942: {

952:   if (ls->usetaoroutines) {
953:       TaoComputeObjectiveAndGradient(ls->tao,x,f,g);
954:   } else {
955:     if (!ls->ops->computeobjective && !ls->ops->computeobjectiveandgradient) SETERRQ(PetscObjectComm((PetscObject)ls),PETSC_ERR_ARG_WRONGSTATE,"Line Search does not have objective function set");
956:     if (!ls->ops->computegradient  && !ls->ops->computeobjectiveandgradient) SETERRQ(PetscObjectComm((PetscObject)ls),PETSC_ERR_ARG_WRONGSTATE,"Line Search does not have gradient function set");
957:     PetscLogEventBegin(TAOLINESEARCH_Eval,ls,0,0,0);
958:     PetscStackPush("TaoLineSearch user objective/gradient routine");
959:     if (ls->ops->computeobjectiveandgradient) {
960:       (*ls->ops->computeobjectiveandgradient)(ls,x,f,g,ls->userctx_funcgrad);
961:     } else {
962:       (*ls->ops->computeobjective)(ls,x,f,ls->userctx_func);
963:       (*ls->ops->computegradient)(ls,x,g,ls->userctx_grad);
964:     }
965:     PetscStackPop;
966:     PetscLogEventEnd(TAOLINESEARCH_Eval,ls,0,0,0);
967:     PetscInfo1(ls,"TaoLineSearch Function evaluation: %14.12e\n",(double)(*f));
968:   }
969:   ls->nfgeval++;
970:   return(0);
971: }

973: /*@
974:   TaoLineSearchComputeGradient - Computes the gradient of the objective function

976:   Collective on TaoLineSearch

978:   Input Parameters:
979: + ls - the TaoLineSearch context
980: - x - input vector

982:   Output Parameter:
983: . g - gradient vector

985:   Notes:
986:     TaoComputeGradient() is typically used within line searches
987:   so most users would not generally call this routine themselves.

989:   Level: developer

991: .seealso: TaoLineSearchComputeObjective(), TaoLineSearchComputeObjectiveAndGradient(), TaoLineSearchSetGradient()
992: @*/
993: PetscErrorCode TaoLineSearchComputeGradient(TaoLineSearch ls, Vec x, Vec g)
994: {
996:   PetscReal      fdummy;

1004:   if (ls->usetaoroutines) {
1005:     TaoComputeGradient(ls->tao,x,g);
1006:   } else {
1007:     if (!ls->ops->computegradient && !ls->ops->computeobjectiveandgradient) SETERRQ(PetscObjectComm((PetscObject)ls),PETSC_ERR_ARG_WRONGSTATE,"Line Search does not have gradient functions set");
1008:     PetscLogEventBegin(TAOLINESEARCH_Eval,ls,0,0,0);
1009:     PetscStackPush("TaoLineSearch user gradient routine");
1010:     if (ls->ops->computegradient) {
1011:       (*ls->ops->computegradient)(ls,x,g,ls->userctx_grad);
1012:     } else {
1013:       (*ls->ops->computeobjectiveandgradient)(ls,x,&fdummy,g,ls->userctx_funcgrad);
1014:     }
1015:     PetscStackPop;
1016:     PetscLogEventEnd(TAOLINESEARCH_Eval,ls,0,0,0);
1017:   }
1018:   ls->ngeval++;
1019:   return(0);
1020: }

1022: /*@
1023:   TaoLineSearchComputeObjectiveAndGTS - Computes the objective function value and inner product of gradient and step direction at a given point

1025:   Collective on Tao

1027:   Input Parameters:
1028: + ls - the TaoLineSearch context
1029: - x - input vector

1031:   Output Parameter:
1032: + f - Objective value at X
1033: - gts - inner product of gradient and step direction at X

1035:   Notes:
1036:     TaoLineSearchComputeObjectiveAndGTS() is typically used within line searches
1037:   so most users would not generally call this routine themselves.

1039:   Level: developer

1041: .seealso: TaoLineSearchComputeGradient(), TaoLineSearchComputeObjectiveAndGradient(), TaoLineSearchSetObjectiveRoutine()
1042: @*/
1043: PetscErrorCode TaoLineSearchComputeObjectiveAndGTS(TaoLineSearch ls, Vec x, PetscReal *f, PetscReal *gts)
1044: {
1052:   if (!ls->ops->computeobjectiveandgts) SETERRQ(PetscObjectComm((PetscObject)ls),PETSC_ERR_ARG_WRONGSTATE,"Line Search does not have objective and gts function set");
1053:   PetscLogEventBegin(TAOLINESEARCH_Eval,ls,0,0,0);
1054:   PetscStackPush("TaoLineSearch user objective/gts routine");
1055:   (*ls->ops->computeobjectiveandgts)(ls,x,ls->stepdirection,f,gts,ls->userctx_funcgts);
1056:   PetscStackPop;
1057:   PetscLogEventEnd(TAOLINESEARCH_Eval,ls,0,0,0);
1058:   PetscInfo1(ls,"TaoLineSearch Function evaluation: %14.12e\n",(double)(*f));
1059:   ls->nfeval++;
1060:   return(0);
1061: }

1063: /*@
1064:   TaoLineSearchGetSolution - Returns the solution to the line search

1066:   Collective on TaoLineSearch

1068:   Input Parameter:
1069: . ls - the TaoLineSearch context

1071:   Output Parameter:
1072: + x - the new solution
1073: . f - the objective function value at x
1074: . g - the gradient at x
1075: . steplength - the multiple of the step direction taken by the line search
1076: - reason - the reason why the line search terminated

1078:   reason will be set to one of:

1080: + TAOLINESEARCH_FAILED_INFORNAN - function evaluation gives Inf or Nan value
1081: . TAOLINESEARCH_FAILED_BADPARAMETER - negative value set as parameter
1082: . TAOLINESEARCH_FAILED_ASCENT - initial line search step * g is not descent direction
1083: . TAOLINESEARCH_HALTED_MAXFCN - maximum number of function evaluation reached
1084: . TAOLINESEARCH_HALTED_UPPERBOUND - step is at upper bound
1085: . TAOLINESEARCH_HALTED_LOWERBOUND - step is at lower bound
1086: . TAOLINESEARCH_HALTED_RTOL - range of uncertainty is smaller than given tolerance

1088: . TAOLINESEARCH_HALTED_USER - user can set this reason to stop line search
1089: . TAOLINESEARCH_HALTED_OTHER - any other reason

1091: - TAOLINESEARCH_SUCCESS - successful line search

1093:   Level: developer

1095: @*/
1096: PetscErrorCode TaoLineSearchGetSolution(TaoLineSearch ls, Vec x, PetscReal *f, Vec g, PetscReal *steplength, TaoLineSearchConvergedReason *reason)
1097: {

1106:   if (ls->new_x) {
1107:     VecCopy(ls->new_x,x);
1108:   }
1109:   *f = ls->new_f;
1110:   if (ls->new_g) {
1111:     VecCopy(ls->new_g,g);
1112:   }
1113:   if (steplength) {
1114:     *steplength=ls->step;
1115:   }
1116:   *reason = ls->reason;
1117:   return(0);
1118: }

1120: /*@
1121:   TaoLineSearchGetStartingVector - Gets a the initial point of the line
1122:   search.

1124:   Not Collective

1126:   Input Parameter:
1127: . ls - the TaoLineSearch context

1129:   Output Parameter:
1130: . x - The initial point of the line search

1132:   Level: intermediate
1133: @*/
1134: PetscErrorCode TaoLineSearchGetStartingVector(TaoLineSearch ls, Vec *x)
1135: {
1138:   if (x) {
1139:     *x = ls->start_x;
1140:   }
1141:   return(0);
1142: }

1144: /*@
1145:   TaoLineSearchGetStepDirection - Gets the step direction of the line
1146:   search.

1148:   Not Collective

1150:   Input Parameter:
1151: . ls - the TaoLineSearch context

1153:   Output Parameter:
1154: . s - the step direction of the line search

1156:   Level: advanced
1157: @*/
1158: PetscErrorCode TaoLineSearchGetStepDirection(TaoLineSearch ls, Vec *s)
1159: {
1162:   if (s) {
1163:     *s = ls->stepdirection;
1164:   }
1165:   return(0);

1167: }

1169: /*@
1170:   TaoLineSearchGetFullStepObjective - Returns the objective function value at the full step.  Useful for some minimization algorithms.

1172:   Not Collective

1174:   Input Parameter:
1175: . ls - the TaoLineSearch context

1177:   Output Parameter:
1178: . f - the objective value at the full step length

1180:   Level: developer
1181: @*/

1183: PetscErrorCode TaoLineSearchGetFullStepObjective(TaoLineSearch ls, PetscReal *f_fullstep)
1184: {
1187:   *f_fullstep = ls->f_fullstep;
1188:   return(0);
1189: }

1191: /*@
1192:   TaoLineSearchSetVariableBounds - Sets the upper and lower bounds.

1194:   Logically Collective on Tao

1196:   Input Parameters:
1197: + ls - the TaoLineSearch context
1198: . xl  - vector of lower bounds
1199: - xu  - vector of upper bounds

1201:   Note: If the variable bounds are not set with this routine, then
1202:   PETSC_NINFINITY and PETSC_INFINITY are assumed

1204:   Level: beginner

1206: .seealso: TaoSetVariableBounds(), TaoLineSearchCreate()
1207: @*/
1208: PetscErrorCode TaoLineSearchSetVariableBounds(TaoLineSearch ls,Vec xl, Vec xu)
1209: {
1214:   ls->lower = xl;
1215:   ls->upper = xu;
1216:   ls->bounded = 1;
1217:   return(0);
1218: }

1220: /*@
1221:   TaoLineSearchSetInitialStepLength - Sets the initial step length of a line
1222:   search.  If this value is not set then 1.0 is assumed.

1224:   Logically Collective on TaoLineSearch

1226:   Input Parameters:
1227: + ls - the TaoLineSearch context
1228: - s - the initial step size

1230:   Level: intermediate

1232: .seealso: TaoLineSearchGetStepLength(), TaoLineSearchApply()
1233: @*/
1234: PetscErrorCode TaoLineSearchSetInitialStepLength(TaoLineSearch ls,PetscReal s)
1235: {
1238:   ls->initstep = s;
1239:   return(0);
1240: }

1242: /*@
1243:   TaoLineSearchGetStepLength - Get the current step length

1245:   Not Collective

1247:   Input Parameters:
1248: . ls - the TaoLineSearch context

1250:   Output Parameters
1251: . s - the current step length

1253:   Level: beginner

1255: .seealso: TaoLineSearchSetInitialStepLength(), TaoLineSearchApply()
1256: @*/
1257: PetscErrorCode TaoLineSearchGetStepLength(TaoLineSearch ls,PetscReal *s)
1258: {
1261:   *s = ls->step;
1262:   return(0);
1263: }

1265: /*@C
1266:    TaoLineSearchRegister - Adds a line-search algorithm to the registry

1268:    Not collective

1270:    Input Parameters:
1271: +  sname - name of a new user-defined solver
1272: -  func - routine to Create method context

1274:    Notes:
1275:    TaoLineSearchRegister() may be called multiple times to add several user-defined solvers.

1277:    Sample usage:
1278: .vb
1279:    TaoLineSearchRegister("my_linesearch",MyLinesearchCreate);
1280: .ve

1282:    Then, your solver can be chosen with the procedural interface via
1283: $     TaoLineSearchSetType(ls,"my_linesearch")
1284:    or at runtime via the option
1285: $     -tao_ls_type my_linesearch

1287:    Level: developer

1289: @*/
1290: PetscErrorCode TaoLineSearchRegister(const char sname[], PetscErrorCode (*func)(TaoLineSearch))
1291: {
1294:   TaoLineSearchInitializePackage();
1295:   PetscFunctionListAdd(&TaoLineSearchList, sname, (void (*)(void))func);
1296:   return(0);
1297: }

1299: /*@C
1300:    TaoLineSearchAppendOptionsPrefix - Appends to the prefix used for searching
1301:    for all TaoLineSearch options in the database.


1304:    Collective on TaoLineSearch

1306:    Input Parameters:
1307: +  ls - the TaoLineSearch solver context
1308: -  prefix - the prefix string to prepend to all line search requests

1310:    Notes:
1311:    A hyphen (-) must NOT be given at the beginning of the prefix name.
1312:    The first character of all runtime options is AUTOMATICALLY the hyphen.


1315:    Level: advanced

1317: .seealso: TaoLineSearchSetOptionsPrefix(), TaoLineSearchGetOptionsPrefix()
1318: @*/
1319: PetscErrorCode TaoLineSearchAppendOptionsPrefix(TaoLineSearch ls, const char p[])
1320: {
1321:   return PetscObjectAppendOptionsPrefix((PetscObject)ls,p);
1322: }

1324: /*@C
1325:   TaoLineSearchGetOptionsPrefix - Gets the prefix used for searching for all
1326:   TaoLineSearch options in the database

1328:   Not Collective

1330:   Input Parameters:
1331: . ls - the TaoLineSearch context

1333:   Output Parameters:
1334: . prefix - pointer to the prefix string used is returned

1336:   Notes:
1337:     On the fortran side, the user should pass in a string 'prefix' of
1338:   sufficient length to hold the prefix.

1340:   Level: advanced

1342: .seealso: TaoLineSearchSetOptionsPrefix(), TaoLineSearchAppendOptionsPrefix()
1343: @*/
1344: PetscErrorCode TaoLineSearchGetOptionsPrefix(TaoLineSearch ls, const char *p[])
1345: {
1346:   return PetscObjectGetOptionsPrefix((PetscObject)ls,p);
1347: }

1349: /*@C
1350:    TaoLineSearchSetOptionsPrefix - Sets the prefix used for searching for all
1351:    TaoLineSearch options in the database.


1354:    Logically Collective on TaoLineSearch

1356:    Input Parameters:
1357: +  ls - the TaoLineSearch context
1358: -  prefix - the prefix string to prepend to all TAO option requests

1360:    Notes:
1361:    A hyphen (-) must NOT be given at the beginning of the prefix name.
1362:    The first character of all runtime options is AUTOMATICALLY the hyphen.

1364:    For example, to distinguish between the runtime options for two
1365:    different line searches, one could call
1366: .vb
1367:       TaoLineSearchSetOptionsPrefix(ls1,"sys1_")
1368:       TaoLineSearchSetOptionsPrefix(ls2,"sys2_")
1369: .ve

1371:    This would enable use of different options for each system, such as
1372: .vb
1373:       -sys1_tao_ls_type mt
1374:       -sys2_tao_ls_type armijo
1375: .ve

1377:    Level: advanced

1379: .seealso: TaoLineSearchAppendOptionsPrefix(), TaoLineSearchGetOptionsPrefix()
1380: @*/

1382: PetscErrorCode TaoLineSearchSetOptionsPrefix(TaoLineSearch ls, const char p[])
1383: {
1384:   return PetscObjectSetOptionsPrefix((PetscObject)ls,p);
1385: }