Actual source code: ms.c

petsc-master 2020-10-23
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  1: #include <petsc/private/snesimpl.h>

  3: static SNESMSType SNESMSDefault = SNESMSM62;
  4: static PetscBool  SNESMSRegisterAllCalled;
  5: static PetscBool  SNESMSPackageInitialized;

  7: typedef struct _SNESMSTableau *SNESMSTableau;
  8: struct _SNESMSTableau {
  9:   char      *name;
 10:   PetscInt  nstages;            /* Number of stages */
 11:   PetscInt  nregisters;         /* Number of registers */
 12:   PetscReal stability;          /* Scaled stability region */
 13:   PetscReal *gamma;             /* Coefficients of 3S* method */
 14:   PetscReal *delta;             /* Coefficients of 3S* method */
 15:   PetscReal *betasub;           /* Subdiagonal of beta in Shu-Osher form */
 16: };

 18: typedef struct _SNESMSTableauLink *SNESMSTableauLink;
 19: struct _SNESMSTableauLink {
 20:   struct _SNESMSTableau tab;
 21:   SNESMSTableauLink     next;
 22: };
 23: static SNESMSTableauLink SNESMSTableauList;

 25: typedef struct {
 26:   SNESMSTableau tableau;        /* Tableau in low-storage form */
 27:   PetscReal     damping;        /* Damping parameter, like length of (pseudo) time step */
 28:   PetscBool     norms;          /* Compute norms, usually only for monitoring purposes */
 29: } SNES_MS;

 31: /*@C
 32:   SNESMSRegisterAll - Registers all of the multi-stage methods in SNESMS

 34:   Not Collective, but should be called by all processes which will need the schemes to be registered

 36:   Level: advanced

 38: .seealso:  SNESMSRegisterDestroy()
 39: @*/
 40: PetscErrorCode SNESMSRegisterAll(void)
 41: {

 45:   if (SNESMSRegisterAllCalled) return(0);
 46:   SNESMSRegisterAllCalled = PETSC_TRUE;

 48:   {
 49:     PetscReal alpha[1] = {1.0};
 50:     SNESMSRegister(SNESMSEULER,1,1,1.0,NULL,NULL,alpha);
 51:   }

 53:   {
 54:     PetscReal gamma[3][6] = {
 55:       {0.0000000000000000E+00, -7.0304722367110606E-01, -1.9836719667506464E-01, -1.6023843981863788E+00,  9.4483822882855284E-02, -1.4204296130641869E-01},
 56:       {1.0000000000000000E+00,  1.1111025767083920E+00,  5.6150921583923230E-01,  7.4151723494934041E-01,  3.1714538168600587E-01,  4.6479276238548706E-01},
 57:       {0.0000000000000000E+00,  0.0000000000000000E+00,  0.0000000000000000E+00,  6.7968174970583317E-01, -4.1755042846051737E-03, -1.9115668129923846E-01}
 58:     };
 59:     PetscReal delta[6]   = {1.0000000000000000E+00, 5.3275427433201750E-01, 6.0143544663985238E-01, 4.5874077053842177E-01, 2.7544386906104651E-01, 0.0000000000000000E+00};
 60:     PetscReal betasub[6] = {8.4753115429481929E-01, 7.4018896368655618E-01, 6.5963574086583309E-03, 4.6747795645517759E-01, 1.3314545813643919E-01, 5.3260800028018784E-01};
 61:     SNESMSRegister(SNESMSM62,6,3,1.0,&gamma[0][0],delta,betasub);
 62:   }

 64:   { /* Jameson (1983) */
 65:     PetscReal alpha[4] = {0.25, 0.5, 0.55, 1.0};
 66:     SNESMSRegister(SNESMSJAMESON83,4,1,1.0,NULL,NULL,alpha);
 67:   }

 69:   { /* Van Leer, Tai, and Powell (1989) 1 stage, order 1 */
 70:     PetscReal alpha[1]  = {1.0};
 71:     SNESMSRegister(SNESMSVLTP11,1,1,0.5,NULL,NULL,alpha);
 72:   }
 73:   { /* Van Leer, Tai, and Powell (1989) 2 stage, order 1 */
 74:     PetscReal alpha[2] = {0.3333, 1.0};
 75:     SNESMSRegister(SNESMSVLTP21,2,1,1.0,NULL,NULL,alpha);
 76:   }
 77:   { /* Van Leer, Tai, and Powell (1989) 3 stage, order 1 */
 78:     PetscReal alpha[3] = {0.1481, 0.4000, 1.0};
 79:     SNESMSRegister(SNESMSVLTP31,3,1,1.5,NULL,NULL,alpha);
 80:   }
 81:   { /* Van Leer, Tai, and Powell (1989) 4 stage, order 1 */
 82:     PetscReal alpha[4] = {0.0833, 0.2069, 0.4265, 1.0};
 83:     SNESMSRegister(SNESMSVLTP41,4,1,2.0,NULL,NULL,alpha);
 84:   }
 85:   { /* Van Leer, Tai, and Powell (1989) 5 stage, order 1 */
 86:     PetscReal alpha[5] = {0.0533, 0.1263, 0.2375, 0.4414,1.0};
 87:     SNESMSRegister(SNESMSVLTP51,5,1,2.5,NULL,NULL,alpha);
 88:   }
 89:   { /* Van Leer, Tai, and Powell (1989) 6 stage, order 1 */
 90:     PetscReal alpha[6] = {0.0370, 0.0851, 0.1521, 0.2562, 0.4512, 1.0};
 91:     SNESMSRegister(SNESMSVLTP61,6,1,3.0,NULL,NULL,alpha);
 92:   }
 93:   return(0);
 94: }

 96: /*@C
 97:    SNESMSRegisterDestroy - Frees the list of schemes that were registered by SNESMSRegister().

 99:    Not Collective

101:    Level: advanced

103: .seealso: SNESMSRegister(), SNESMSRegisterAll()
104: @*/
105: PetscErrorCode SNESMSRegisterDestroy(void)
106: {
107:   PetscErrorCode    ierr;
108:   SNESMSTableauLink link;

111:   while ((link = SNESMSTableauList)) {
112:     SNESMSTableau t = &link->tab;
113:     SNESMSTableauList = link->next;

115:     PetscFree(t->name);
116:     PetscFree(t->gamma);
117:     PetscFree(t->delta);
118:     PetscFree(t->betasub);
119:     PetscFree(link);
120:   }
121:   SNESMSRegisterAllCalled = PETSC_FALSE;
122:   return(0);
123: }

125: /*@C
126:   SNESMSInitializePackage - This function initializes everything in the SNESMS package. It is called
127:   from SNESInitializePackage().

129:   Level: developer

131: .seealso: PetscInitialize()
132: @*/
133: PetscErrorCode SNESMSInitializePackage(void)
134: {

138:   if (SNESMSPackageInitialized) return(0);
139:   SNESMSPackageInitialized = PETSC_TRUE;

141:   SNESMSRegisterAll();
142:   PetscRegisterFinalize(SNESMSFinalizePackage);
143:   return(0);
144: }

146: /*@C
147:   SNESMSFinalizePackage - This function destroys everything in the SNESMS package. It is
148:   called from PetscFinalize().

150:   Level: developer

152: .seealso: PetscFinalize()
153: @*/
154: PetscErrorCode SNESMSFinalizePackage(void)
155: {

159:   SNESMSPackageInitialized = PETSC_FALSE;

161:   SNESMSRegisterDestroy();
162:   return(0);
163: }

165: /*@C
166:    SNESMSRegister - register a multistage scheme

168:    Not Collective, but the same schemes should be registered on all processes on which they will be used

170:    Input Parameters:
171: +  name - identifier for method
172: .  nstages - number of stages
173: .  nregisters - number of registers used by low-storage implementation
174: .  stability - scaled stability region
175: .  gamma - coefficients, see Ketcheson's paper
176: .  delta - coefficients, see Ketcheson's paper
177: -  betasub - subdiagonal of Shu-Osher form

179:    Notes:
180:    The notation is described in Ketcheson (2010) Runge-Kutta methods with minimum storage implementations.

182:    Many multistage schemes are of the form
183:    $ X_0 = X^{(n)}
184:    $ X_k = X_0 + \alpha_k * F(X_{k-1}), k = 1,\ldots,s
185:    $ X^{(n+1)} = X_s
186:    These methods can be registered with
187: .vb
188:    SNESMSRegister("name",s,1,stability,NULL,NULL,alpha);
189: .ve

191:    Level: advanced

193: .seealso: SNESMS
194: @*/
195: PetscErrorCode SNESMSRegister(SNESMSType name,PetscInt nstages,PetscInt nregisters,PetscReal stability,const PetscReal gamma[],const PetscReal delta[],const PetscReal betasub[])
196: {
197:   PetscErrorCode    ierr;
198:   SNESMSTableauLink link;
199:   SNESMSTableau     t;

203:   if (nstages < 1) SETERRQ(PETSC_COMM_SELF,PETSC_ERR_ARG_OUTOFRANGE,"Must have at least one stage");
204:   if (gamma || delta) {
205:     if (nregisters != 3) SETERRQ(PETSC_COMM_SELF,PETSC_ERR_SUP,"Only support for methods written in 3-register form");
208:   } else {
209:     if (nregisters != 1) SETERRQ(PETSC_COMM_SELF,PETSC_ERR_SUP,"Only support for methods written in 1-register form");
210:   }

213:   SNESMSInitializePackage();
214:   PetscNew(&link);
215:   t             = &link->tab;
216:   PetscStrallocpy(name,&t->name);
217:   t->nstages    = nstages;
218:   t->nregisters = nregisters;
219:   t->stability  = stability;

221:   if (gamma && delta) {
222:     PetscMalloc1(nstages*nregisters,&t->gamma);
223:     PetscMalloc1(nstages,&t->delta);
224:     PetscArraycpy(t->gamma,gamma,nstages*nregisters);
225:     PetscArraycpy(t->delta,delta,nstages);
226:   }
227:   PetscMalloc1(nstages,&t->betasub);
228:   PetscArraycpy(t->betasub,betasub,nstages);

230:   link->next        = SNESMSTableauList;
231:   SNESMSTableauList = link;
232:   return(0);
233: }

235: /*
236:   X - initial state, updated in-place.
237:   F - residual, computed at the initial X on input
238: */
239: static PetscErrorCode SNESMSStep_3Sstar(SNES snes,Vec X,Vec F)
240: {
241:   PetscErrorCode  ierr;
242:   SNES_MS         *ms    = (SNES_MS*)snes->data;
243:   SNESMSTableau   t      = ms->tableau;
244:   const PetscReal *gamma = t->gamma,*delta = t->delta,*betasub = t->betasub;
245:   Vec             S1,S2,S3,Y;
246:   PetscInt        i,nstages = t->nstages;

249:   Y    = snes->work[0];
250:   S1   = X;
251:   S2   = snes->work[1];
252:   S3   = snes->work[2];
253:   VecZeroEntries(S2);
254:   VecCopy(X,S3);
255:   for (i = 0; i < nstages; i++) {
256:     Vec         Ss[4];
257:     PetscScalar scoeff[4];

259:     Ss[0] = S1; Ss[1] = S2; Ss[2] = S3; Ss[3] = Y;

261:     scoeff[0] = gamma[0*nstages+i] - 1;
262:     scoeff[1] = gamma[1*nstages+i];
263:     scoeff[2] = gamma[2*nstages+i];
264:     scoeff[3] = -betasub[i]*ms->damping;

266:     VecAXPY(S2,delta[i],S1);
267:     if (i > 0) {
268:       SNESComputeFunction(snes,S1,F);
269:     }
270:     KSPSolve(snes->ksp,F,Y);
271:     VecMAXPY(S1,4,scoeff,Ss);
272:   }
273:   return(0);
274: }

276: /*
277:   X - initial state, updated in-place.
278:   F - residual, computed at the initial X on input
279: */
280: static PetscErrorCode SNESMSStep_Basic(SNES snes,Vec X,Vec F)
281: {
282:   PetscErrorCode  ierr;
283:   SNES_MS         *ms    = (SNES_MS*)snes->data;
284:   SNESMSTableau   tab    = ms->tableau;
285:   const PetscReal *alpha = tab->betasub, h = ms->damping;
286:   PetscInt        i,nstages = tab->nstages;
287:   Vec             X0 = snes->work[0];

290:   VecCopy(X,X0);
291:   for (i = 0; i < nstages; i++) {
292:     if (i > 0) {
293:       SNESComputeFunction(snes,X,F);
294:     }
295:     KSPSolve(snes->ksp,F,X);
296:     VecAYPX(X,-alpha[i]*h,X0);
297:   }
298:   return(0);
299: }

301: static PetscErrorCode SNESMSStep_Step(SNES snes,Vec X,Vec F)
302: {
303:   SNES_MS        *ms = (SNES_MS*)snes->data;
304:   SNESMSTableau  tab = ms->tableau;

308:   if (tab->gamma && tab->delta) {
309:     SNESMSStep_3Sstar(snes,X,F);
310:   } else {
311:     SNESMSStep_Basic(snes,X,F);
312:   }
313:   return(0);
314: }

316: static PetscErrorCode SNESMSStep_Norms(SNES snes,PetscInt iter,Vec F)
317: {
318:   SNES_MS        *ms = (SNES_MS*)snes->data;
319:   PetscReal      fnorm;

323:   if (ms->norms) {
324:     VecNorm(F,NORM_2,&fnorm); /* fnorm <- ||F||  */
325:     SNESCheckFunctionNorm(snes,fnorm);
326:     /* Monitor convergence */
327:     PetscObjectSAWsTakeAccess((PetscObject)snes);
328:     snes->iter = iter;
329:     snes->norm = fnorm;
330:     PetscObjectSAWsGrantAccess((PetscObject)snes);
331:     SNESLogConvergenceHistory(snes,snes->norm,0);
332:     SNESMonitor(snes,snes->iter,snes->norm);
333:     /* Test for convergence */
334:     (*snes->ops->converged)(snes,snes->iter,0.0,0.0,fnorm,&snes->reason,snes->cnvP);
335:   } else if (iter > 0) {
336:     PetscObjectSAWsTakeAccess((PetscObject)snes);
337:     snes->iter = iter;
338:     PetscObjectSAWsGrantAccess((PetscObject)snes);
339:   }
340:   return(0);
341: }

343: static PetscErrorCode SNESSolve_MS(SNES snes)
344: {
345:   SNES_MS        *ms = (SNES_MS*)snes->data;
346:   Vec            X   = snes->vec_sol,F = snes->vec_func;
347:   PetscInt       i;

351:   if (snes->xl || snes->xu || snes->ops->computevariablebounds) SETERRQ1(PetscObjectComm((PetscObject)snes),PETSC_ERR_ARG_WRONGSTATE, "SNES solver %s does not support bounds", ((PetscObject)snes)->type_name);
352:   PetscCitationsRegister(SNESCitation,&SNEScite);

354:   snes->reason = SNES_CONVERGED_ITERATING;
355:   PetscObjectSAWsTakeAccess((PetscObject)snes);
356:   snes->iter   = 0;
357:   snes->norm   = 0;
358:   PetscObjectSAWsGrantAccess((PetscObject)snes);

360:   if (!snes->vec_func_init_set) {
361:     SNESComputeFunction(snes,X,F);
362:   } else snes->vec_func_init_set = PETSC_FALSE;

364:   SNESMSStep_Norms(snes,0,F);
365:   if (snes->reason) return(0);

367:   for (i = 0; i < snes->max_its; i++) {

369:     /* Call general purpose update function */
370:     if (snes->ops->update) {
371:       (*snes->ops->update)(snes,snes->iter);
372:     }

374:     if (i == 0 && snes->jacobian) {
375:       /* This method does not require a Jacobian, but it is usually preconditioned by PBJacobi */
376:       SNESComputeJacobian(snes,snes->vec_sol,snes->jacobian,snes->jacobian_pre);
377:       SNESCheckJacobianDomainerror(snes);
378:       KSPSetOperators(snes->ksp,snes->jacobian,snes->jacobian_pre);
379:     }

381:     SNESMSStep_Step(snes,X,F);

383:     if (i < snes->max_its-1 || ms->norms) {
384:       SNESComputeFunction(snes,X,F);
385:     }

387:     SNESMSStep_Norms(snes,i+1,F);
388:     if (snes->reason) return(0);
389:   }
390:   if (!snes->reason) snes->reason = SNES_CONVERGED_ITS;
391:   return(0);
392: }

394: static PetscErrorCode SNESSetUp_MS(SNES snes)
395: {
396:   SNES_MS        *ms   = (SNES_MS*)snes->data;
397:   SNESMSTableau  tab   = ms->tableau;
398:   PetscInt       nwork = tab->nregisters;

402:   SNESSetWorkVecs(snes,nwork);
403:   SNESSetUpMatrices(snes);
404:   return(0);
405: }

407: static PetscErrorCode SNESReset_MS(SNES snes)
408: {
410:   return(0);
411: }

413: static PetscErrorCode SNESDestroy_MS(SNES snes)
414: {

418:   SNESReset_MS(snes);
419:   PetscFree(snes->data);
420:   PetscObjectComposeFunction((PetscObject)snes,"SNESMSGetType_C",NULL);
421:   PetscObjectComposeFunction((PetscObject)snes,"SNESMSSetType_C",NULL);
422:   PetscObjectComposeFunction((PetscObject)snes,"SNESMSGetDamping_C",NULL);
423:   PetscObjectComposeFunction((PetscObject)snes,"SNESMSSetDamping_C",NULL);
424:   return(0);
425: }

427: static PetscErrorCode SNESView_MS(SNES snes,PetscViewer viewer)
428: {
429:   PetscBool      iascii;
431:   SNES_MS        *ms = (SNES_MS*)snes->data;
432:   SNESMSTableau  tab = ms->tableau;

435:   PetscObjectTypeCompare((PetscObject) viewer, PETSCVIEWERASCII, &iascii);
436:   if (iascii) {
437:     PetscViewerASCIIPrintf(viewer,"  multi-stage method type: %s\n",tab->name);
438:   }
439:   return(0);
440: }

442: static PetscErrorCode SNESSetFromOptions_MS(PetscOptionItems *PetscOptionsObject,SNES snes)
443: {
444:   SNES_MS        *ms = (SNES_MS*)snes->data;

448:   PetscOptionsHead(PetscOptionsObject,"SNES MS options");
449:   {
450:     SNESMSTableauLink link;
451:     PetscInt          count,choice;
452:     PetscBool         flg;
453:     const char        **namelist;
454:     SNESMSType        mstype;
455:     PetscReal         damping;

457:     SNESMSGetType(snes,&mstype);
458:     for (link=SNESMSTableauList,count=0; link; link=link->next,count++) ;
459:     PetscMalloc1(count,(char***)&namelist);
460:     for (link=SNESMSTableauList,count=0; link; link=link->next,count++) namelist[count] = link->tab.name;
461:     PetscOptionsEList("-snes_ms_type","Multistage smoother type","SNESMSSetType",(const char*const*)namelist,count,mstype,&choice,&flg);
462:     if (flg) {SNESMSSetType(snes,namelist[choice]);}
463:     PetscFree(namelist);
464:     SNESMSGetDamping(snes,&damping);
465:     PetscOptionsReal("-snes_ms_damping","Damping for multistage method","SNESMSSetDamping",damping,&damping,&flg);
466:     if (flg) {SNESMSSetDamping(snes,damping);}
467:     PetscOptionsBool("-snes_ms_norms","Compute norms for monitoring","none",ms->norms,&ms->norms,NULL);
468:   }
469:   PetscOptionsTail();
470:   return(0);
471: }

473: static PetscErrorCode SNESMSGetType_MS(SNES snes,SNESMSType *mstype)
474: {
475:   SNES_MS        *ms = (SNES_MS*)snes->data;
476:   SNESMSTableau  tab = ms->tableau;

479:   *mstype = tab->name;
480:   return(0);
481: }

483: static PetscErrorCode SNESMSSetType_MS(SNES snes,SNESMSType mstype)
484: {
485:   SNES_MS           *ms = (SNES_MS*)snes->data;
486:   SNESMSTableauLink link;
487:   PetscBool         match;
488:   PetscErrorCode    ierr;

491:   if (ms->tableau) {
492:     PetscStrcmp(ms->tableau->name,mstype,&match);
493:     if (match) return(0);
494:   }
495:   for (link = SNESMSTableauList; link; link=link->next) {
496:     PetscStrcmp(link->tab.name,mstype,&match);
497:     if (match) {
498:       if (snes->setupcalled)  {SNESReset_MS(snes);}
499:       ms->tableau = &link->tab;
500:       if (snes->setupcalled)  {SNESSetUp_MS(snes);}
501:       return(0);
502:     }
503:   }
504:   SETERRQ1(PetscObjectComm((PetscObject)snes),PETSC_ERR_ARG_UNKNOWN_TYPE,"Could not find '%s'",mstype);
505:   return(0);
506: }

508: /*@C
509:   SNESMSGetType - Get the type of multistage smoother

511:   Not collective

513:   Input Parameter:
514: .  snes - nonlinear solver context

516:   Output Parameter:
517: .  mstype - type of multistage method

519:   Level: beginner

521: .seealso: SNESMSSetType(), SNESMSType, SNESMS
522: @*/
523: PetscErrorCode SNESMSGetType(SNES snes,SNESMSType *mstype)
524: {

530:   PetscUseMethod(snes,"SNESMSGetType_C",(SNES,SNESMSType*),(snes,mstype));
531:   return(0);
532: }

534: /*@C
535:   SNESMSSetType - Set the type of multistage smoother

537:   Logically collective

539:   Input Parameter:
540: +  snes - nonlinear solver context
541: -  mstype - type of multistage method

543:   Level: beginner

545: .seealso: SNESMSGetType(), SNESMSType, SNESMS
546: @*/
547: PetscErrorCode SNESMSSetType(SNES snes,SNESMSType mstype)
548: {

554:   PetscTryMethod(snes,"SNESMSSetType_C",(SNES,SNESMSType),(snes,mstype));
555:   return(0);
556: }

558: static PetscErrorCode SNESMSGetDamping_MS(SNES snes,PetscReal *damping)
559: {
560:   SNES_MS        *ms = (SNES_MS*)snes->data;

563:   *damping = ms->damping;
564:   return(0);
565: }

567: static PetscErrorCode SNESMSSetDamping_MS(SNES snes,PetscReal damping)
568: {
569:   SNES_MS           *ms = (SNES_MS*)snes->data;

572:   ms->damping = damping;
573:   return(0);
574: }

576: /*@C
577:   SNESMSGetDamping - Get the damping parameter

579:   Not collective

581:   Input Parameter:
582: .  snes - nonlinear solver context

584:   Output Parameter:
585: .  damping - damping parameter

587:   Level: advanced

589: .seealso: SNESMSSetDamping(), SNESMS
590: @*/
591: PetscErrorCode SNESMSGetDamping(SNES snes,PetscReal *damping)
592: {

598:   PetscUseMethod(snes,"SNESMSGetDamping_C",(SNES,PetscReal*),(snes,damping));
599:   return(0);
600: }

602: /*@C
603:   SNESMSSetDamping - Set the damping parameter

605:   Logically collective

607:   Input Parameter:
608: +  snes - nonlinear solver context
609: -  damping - damping parameter

611:   Level: advanced

613: .seealso: SNESMSGetDamping(), SNESMS
614: @*/
615: PetscErrorCode SNESMSSetDamping(SNES snes,PetscReal damping)
616: {

622:   PetscTryMethod(snes,"SNESMSSetDamping_C",(SNES,PetscReal),(snes,damping));
623:   return(0);
624: }

626: /* -------------------------------------------------------------------------- */
627: /*MC
628:       SNESMS - multi-stage smoothers

630:       Options Database:

632: +     -snes_ms_type - type of multi-stage smoother
633: -     -snes_ms_damping - damping for multi-stage method

635:       Notes:
636:       These multistage methods are explicit Runge-Kutta methods that are often used as smoothers for
637:       FAS multigrid for transport problems. In the linear case, these are equivalent to polynomial smoothers (such as Chebyshev).

639:       Multi-stage smoothers should usually be preconditioned by point-block Jacobi to ensure proper scaling and to normalize the wave speeds.

641:       The methods are specified in low storage form (Ketcheson 2010). New methods can be registered with SNESMSRegister().

643:       References:
644: +   1. -   Ketcheson (2010) Runge Kutta methods with minimum storage implementations (https://doi.org/10.1016/j.jcp.2009.11.006).
645: .   2. -   Jameson (1983) Solution of the Euler equations for two dimensional transonic flow by a multigrid method (https://doi.org/10.1016/0096-3003(83)90019-X).
646: .   3. -   Pierce and Giles (1997) Preconditioned multigrid methods for compressible flow calculations on stretched meshes (https://doi.org/10.1006/jcph.1997.5772).
647: -   4. -   Van Leer, Tai, and Powell (1989) Design of optimally smoothing multi-stage schemes for the Euler equations (https://doi.org/10.2514/6.1989-1933).

649:       Level: beginner

651: .seealso:  SNESCreate(), SNES, SNESSetType(), SNESMS, SNESFAS, KSPCHEBYSHEV

653: M*/
654: PETSC_EXTERN PetscErrorCode SNESCreate_MS(SNES snes)
655: {
657:   SNES_MS        *ms;

660:   SNESMSInitializePackage();

662:   snes->ops->setup          = SNESSetUp_MS;
663:   snes->ops->solve          = SNESSolve_MS;
664:   snes->ops->destroy        = SNESDestroy_MS;
665:   snes->ops->setfromoptions = SNESSetFromOptions_MS;
666:   snes->ops->view           = SNESView_MS;
667:   snes->ops->reset          = SNESReset_MS;

669:   snes->usesnpc = PETSC_FALSE;
670:   snes->usesksp = PETSC_TRUE;

672:   snes->alwayscomputesfinalresidual = PETSC_FALSE;

674:   PetscNewLog(snes,&ms);
675:   snes->data  = (void*)ms;
676:   ms->damping = 0.9;
677:   ms->norms   = PETSC_FALSE;

679:   PetscObjectComposeFunction((PetscObject)snes,"SNESMSGetType_C",SNESMSGetType_MS);
680:   PetscObjectComposeFunction((PetscObject)snes,"SNESMSSetType_C",SNESMSSetType_MS);
681:   PetscObjectComposeFunction((PetscObject)snes,"SNESMSGetDamping_C",SNESMSGetDamping_MS);
682:   PetscObjectComposeFunction((PetscObject)snes,"SNESMSSetDamping_C",SNESMSSetDamping_MS);

684:   SNESMSSetType(snes,SNESMSDefault);
685:   return(0);
686: }