Actual source code: redundant.c

petsc-3.8.3 2017-12-09
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  2: /*
  3:   This file defines a "solve the problem redundantly on each subgroup of processor" preconditioner.
  4: */
  5:  #include <petsc/private/pcimpl.h>
  6:  #include <petscksp.h>

  8: typedef struct {
  9:   KSP                ksp;
 10:   PC                 pc;                   /* actual preconditioner used on each processor */
 11:   Vec                xsub,ysub;            /* vectors of a subcommunicator to hold parallel vectors of PetscObjectComm((PetscObject)pc) */
 12:   Vec                xdup,ydup;            /* parallel vector that congregates xsub or ysub facilitating vector scattering */
 13:   Mat                pmats;                /* matrix and optional preconditioner matrix belong to a subcommunicator */
 14:   VecScatter         scatterin,scatterout; /* scatter used to move all values to each processor group (subcommunicator) */
 15:   PetscBool          useparallelmat;
 16:   PetscSubcomm       psubcomm;
 17:   PetscInt           nsubcomm;             /* num of data structure PetscSubcomm */
 18:   PetscBool          shifttypeset;
 19:   MatFactorShiftType shifttype;
 20: } PC_Redundant;

 22: PetscErrorCode  PCFactorSetShiftType_Redundant(PC pc,MatFactorShiftType shifttype)
 23: {
 24:   PC_Redundant   *red = (PC_Redundant*)pc->data;

 28:   if (red->ksp) {
 29:     PC pc;
 30:     KSPGetPC(red->ksp,&pc);
 31:     PCFactorSetShiftType(pc,shifttype);
 32:   } else {
 33:     red->shifttypeset = PETSC_TRUE;
 34:     red->shifttype    = shifttype;
 35:   }
 36:   return(0);
 37: }

 39: static PetscErrorCode PCView_Redundant(PC pc,PetscViewer viewer)
 40: {
 41:   PC_Redundant   *red = (PC_Redundant*)pc->data;
 43:   PetscBool      iascii,isstring;
 44:   PetscViewer    subviewer;

 47:   PetscObjectTypeCompare((PetscObject)viewer,PETSCVIEWERASCII,&iascii);
 48:   PetscObjectTypeCompare((PetscObject)viewer,PETSCVIEWERSTRING,&isstring);
 49:   if (iascii) {
 50:     if (!red->psubcomm) {
 51:       PetscViewerASCIIPrintf(viewer,"  Not yet setup\n");
 52:     } else {
 53:       PetscViewerASCIIPrintf(viewer,"  First (color=0) of %D PCs follows\n",red->nsubcomm);
 54:       PetscViewerGetSubViewer(viewer,((PetscObject)red->pc)->comm,&subviewer);
 55:       if (!red->psubcomm->color) { /* only view first redundant pc */
 56:         PetscViewerASCIIPushTab(subviewer);
 57:         KSPView(red->ksp,subviewer);
 58:         PetscViewerASCIIPopTab(subviewer);
 59:       }
 60:       PetscViewerRestoreSubViewer(viewer,((PetscObject)red->pc)->comm,&subviewer);
 61:     }
 62:   } else if (isstring) {
 63:     PetscViewerStringSPrintf(viewer," Redundant solver preconditioner");
 64:   }
 65:   return(0);
 66: }

 68: static PetscErrorCode PCSetUp_Redundant(PC pc)
 69: {
 70:   PC_Redundant   *red = (PC_Redundant*)pc->data;
 72:   PetscInt       mstart,mend,mlocal,M;
 73:   PetscMPIInt    size;
 74:   MPI_Comm       comm,subcomm;
 75:   Vec            x;

 78:   PetscObjectGetComm((PetscObject)pc,&comm);
 79: 
 80:   /* if pmatrix set by user is sequential then we do not need to gather the parallel matrix */
 81:   MPI_Comm_size(comm,&size);
 82:   if (size == 1) red->useparallelmat = PETSC_FALSE;

 84:   if (!pc->setupcalled) {
 85:     PetscInt mloc_sub;
 86:     if (!red->psubcomm) { /* create red->psubcomm, new ksp and pc over subcomm */
 87:       KSP ksp;
 88:       PCRedundantGetKSP(pc,&ksp);
 89:     }
 90:     subcomm = PetscSubcommChild(red->psubcomm);

 92:     if (red->useparallelmat) {
 93:       /* grab the parallel matrix and put it into processors of a subcomminicator */
 94:       MatCreateRedundantMatrix(pc->pmat,red->psubcomm->n,subcomm,MAT_INITIAL_MATRIX,&red->pmats);

 96:       MPI_Comm_size(subcomm,&size);
 97:       if (size > 1) {
 98:         PetscBool foundpack;
 99:         MatGetFactorAvailable(red->pmats,NULL,MAT_FACTOR_LU,&foundpack);
100:         if (!foundpack) { /* reset default ksp and pc */
101:           KSPSetType(red->ksp,KSPGMRES);
102:           PCSetType(red->pc,PCBJACOBI);
103:         } else {
104:           PCFactorSetMatSolverPackage(red->pc,NULL);
105:         }
106:       }

108:       KSPSetOperators(red->ksp,red->pmats,red->pmats);
109: 
110:       /* get working vectors xsub and ysub */
111:       MatCreateVecs(red->pmats,&red->xsub,&red->ysub);

113:       /* create working vectors xdup and ydup.
114:        xdup concatenates all xsub's contigously to form a mpi vector over dupcomm  (see PetscSubcommCreate_interlaced())
115:        ydup concatenates all ysub and has empty local arrays because ysub's arrays will be place into it.
116:        Note: we use communicator dupcomm, not PetscObjectComm((PetscObject)pc)! */
117:       MatGetLocalSize(red->pmats,&mloc_sub,NULL);
118:       VecCreateMPI(PetscSubcommContiguousParent(red->psubcomm),mloc_sub,PETSC_DECIDE,&red->xdup);
119:       VecCreateMPIWithArray(PetscSubcommContiguousParent(red->psubcomm),1,mloc_sub,PETSC_DECIDE,NULL,&red->ydup);

121:       /* create vecscatters */
122:       if (!red->scatterin) { /* efficiency of scatterin is independent from psubcomm_type! */
123:         IS       is1,is2;
124:         PetscInt *idx1,*idx2,i,j,k;

126:         MatCreateVecs(pc->pmat,&x,0);
127:         VecGetSize(x,&M);
128:         VecGetOwnershipRange(x,&mstart,&mend);
129:         mlocal = mend - mstart;
130:         PetscMalloc2(red->psubcomm->n*mlocal,&idx1,red->psubcomm->n*mlocal,&idx2);
131:         j    = 0;
132:         for (k=0; k<red->psubcomm->n; k++) {
133:           for (i=mstart; i<mend; i++) {
134:             idx1[j]   = i;
135:             idx2[j++] = i + M*k;
136:           }
137:         }
138:         ISCreateGeneral(comm,red->psubcomm->n*mlocal,idx1,PETSC_COPY_VALUES,&is1);
139:         ISCreateGeneral(comm,red->psubcomm->n*mlocal,idx2,PETSC_COPY_VALUES,&is2);
140:         VecScatterCreate(x,is1,red->xdup,is2,&red->scatterin);
141:         ISDestroy(&is1);
142:         ISDestroy(&is2);

144:         /* Impl below is good for PETSC_SUBCOMM_INTERLACED (no inter-process communication) and PETSC_SUBCOMM_CONTIGUOUS (communication within subcomm) */
145:         ISCreateStride(comm,mlocal,mstart+ red->psubcomm->color*M,1,&is1);
146:         ISCreateStride(comm,mlocal,mstart,1,&is2);
147:         VecScatterCreate(red->xdup,is1,x,is2,&red->scatterout);
148:         ISDestroy(&is1);
149:         ISDestroy(&is2);
150:         PetscFree2(idx1,idx2);
151:         VecDestroy(&x);
152:       }
153:     } else { /* !red->useparallelmat */
154:       KSPSetOperators(red->ksp,pc->mat,pc->pmat);
155:     }
156:   } else { /* pc->setupcalled */
157:     if (red->useparallelmat) {
158:       MatReuse       reuse;
159:       /* grab the parallel matrix and put it into processors of a subcomminicator */
160:       /*--------------------------------------------------------------------------*/
161:       if (pc->flag == DIFFERENT_NONZERO_PATTERN) {
162:         /* destroy old matrices */
163:         MatDestroy(&red->pmats);
164:         reuse = MAT_INITIAL_MATRIX;
165:       } else {
166:         reuse = MAT_REUSE_MATRIX;
167:       }
168:       MatCreateRedundantMatrix(pc->pmat,red->psubcomm->n,PetscSubcommChild(red->psubcomm),reuse,&red->pmats);
169:       KSPSetOperators(red->ksp,red->pmats,red->pmats);
170:     } else { /* !red->useparallelmat */
171:       KSPSetOperators(red->ksp,pc->mat,pc->pmat);
172:     }
173:   }

175:   if (pc->setfromoptionscalled) {
176:     KSPSetFromOptions(red->ksp);
177:   }
178:   KSPSetUp(red->ksp);
179:   return(0);
180: }

182: static PetscErrorCode PCApply_Redundant(PC pc,Vec x,Vec y)
183: {
184:   PC_Redundant   *red = (PC_Redundant*)pc->data;
186:   PetscScalar    *array;

189:   if (!red->useparallelmat) {
190:     KSPSolve(red->ksp,x,y);
191:     return(0);
192:   }

194:   /* scatter x to xdup */
195:   VecScatterBegin(red->scatterin,x,red->xdup,INSERT_VALUES,SCATTER_FORWARD);
196:   VecScatterEnd(red->scatterin,x,red->xdup,INSERT_VALUES,SCATTER_FORWARD);

198:   /* place xdup's local array into xsub */
199:   VecGetArray(red->xdup,&array);
200:   VecPlaceArray(red->xsub,(const PetscScalar*)array);

202:   /* apply preconditioner on each processor */
203:   KSPSolve(red->ksp,red->xsub,red->ysub);
204:   VecResetArray(red->xsub);
205:   VecRestoreArray(red->xdup,&array);

207:   /* place ysub's local array into ydup */
208:   VecGetArray(red->ysub,&array);
209:   VecPlaceArray(red->ydup,(const PetscScalar*)array);

211:   /* scatter ydup to y */
212:   VecScatterBegin(red->scatterout,red->ydup,y,INSERT_VALUES,SCATTER_FORWARD);
213:   VecScatterEnd(red->scatterout,red->ydup,y,INSERT_VALUES,SCATTER_FORWARD);
214:   VecResetArray(red->ydup);
215:   VecRestoreArray(red->ysub,&array);
216:   return(0);
217: }

219: static PetscErrorCode PCApplyTranspose_Redundant(PC pc,Vec x,Vec y)
220: {
221:   PC_Redundant   *red = (PC_Redundant*)pc->data;
223:   PetscScalar    *array;

226:   if (!red->useparallelmat) {
227:     KSPSolveTranspose(red->ksp,x,y);
228:     return(0);
229:   }

231:   /* scatter x to xdup */
232:   VecScatterBegin(red->scatterin,x,red->xdup,INSERT_VALUES,SCATTER_FORWARD);
233:   VecScatterEnd(red->scatterin,x,red->xdup,INSERT_VALUES,SCATTER_FORWARD);

235:   /* place xdup's local array into xsub */
236:   VecGetArray(red->xdup,&array);
237:   VecPlaceArray(red->xsub,(const PetscScalar*)array);

239:   /* apply preconditioner on each processor */
240:   KSPSolveTranspose(red->ksp,red->xsub,red->ysub);
241:   VecResetArray(red->xsub);
242:   VecRestoreArray(red->xdup,&array);

244:   /* place ysub's local array into ydup */
245:   VecGetArray(red->ysub,&array);
246:   VecPlaceArray(red->ydup,(const PetscScalar*)array);

248:   /* scatter ydup to y */
249:   VecScatterBegin(red->scatterout,red->ydup,y,INSERT_VALUES,SCATTER_FORWARD);
250:   VecScatterEnd(red->scatterout,red->ydup,y,INSERT_VALUES,SCATTER_FORWARD);
251:   VecResetArray(red->ydup);
252:   VecRestoreArray(red->ysub,&array);
253:   return(0);
254: }

256: static PetscErrorCode PCReset_Redundant(PC pc)
257: {
258:   PC_Redundant   *red = (PC_Redundant*)pc->data;

262:   if (red->useparallelmat) {
263:     VecScatterDestroy(&red->scatterin);
264:     VecScatterDestroy(&red->scatterout);
265:     VecDestroy(&red->ysub);
266:     VecDestroy(&red->xsub);
267:     VecDestroy(&red->xdup);
268:     VecDestroy(&red->ydup);
269:   }
270:   MatDestroy(&red->pmats);
271:   KSPReset(red->ksp);
272:   return(0);
273: }

275: static PetscErrorCode PCDestroy_Redundant(PC pc)
276: {
277:   PC_Redundant   *red = (PC_Redundant*)pc->data;

281:   PCReset_Redundant(pc);
282:   KSPDestroy(&red->ksp);
283:   PetscSubcommDestroy(&red->psubcomm);
284:   PetscFree(pc->data);
285:   return(0);
286: }

288: static PetscErrorCode PCSetFromOptions_Redundant(PetscOptionItems *PetscOptionsObject,PC pc)
289: {
291:   PC_Redundant   *red = (PC_Redundant*)pc->data;

294:   PetscOptionsHead(PetscOptionsObject,"Redundant options");
295:   PetscOptionsInt("-pc_redundant_number","Number of redundant pc","PCRedundantSetNumber",red->nsubcomm,&red->nsubcomm,0);
296:   PetscOptionsTail();
297:   return(0);
298: }

300: static PetscErrorCode PCRedundantSetNumber_Redundant(PC pc,PetscInt nreds)
301: {
302:   PC_Redundant *red = (PC_Redundant*)pc->data;

305:   red->nsubcomm = nreds;
306:   return(0);
307: }

309: /*@
310:    PCRedundantSetNumber - Sets the number of redundant preconditioner contexts.

312:    Logically Collective on PC

314:    Input Parameters:
315: +  pc - the preconditioner context
316: -  nredundant - number of redundant preconditioner contexts; for example if you are using 64 MPI processes and
317:                               use an nredundant of 4 there will be 4 parallel solves each on 16 = 64/4 processes.

319:    Level: advanced

321: .keywords: PC, redundant solve
322: @*/
323: PetscErrorCode PCRedundantSetNumber(PC pc,PetscInt nredundant)
324: {

329:   if (nredundant <= 0) SETERRQ1(PetscObjectComm((PetscObject)pc),PETSC_ERR_ARG_WRONG, "num of redundant pc %D must be positive",nredundant);
330:   PetscTryMethod(pc,"PCRedundantSetNumber_C",(PC,PetscInt),(pc,nredundant));
331:   return(0);
332: }

334: static PetscErrorCode PCRedundantSetScatter_Redundant(PC pc,VecScatter in,VecScatter out)
335: {
336:   PC_Redundant   *red = (PC_Redundant*)pc->data;

340:   PetscObjectReference((PetscObject)in);
341:   VecScatterDestroy(&red->scatterin);

343:   red->scatterin  = in;

345:   PetscObjectReference((PetscObject)out);
346:   VecScatterDestroy(&red->scatterout);
347:   red->scatterout = out;
348:   return(0);
349: }

351: /*@
352:    PCRedundantSetScatter - Sets the scatter used to copy values into the
353:      redundant local solve and the scatter to move them back into the global
354:      vector.

356:    Logically Collective on PC

358:    Input Parameters:
359: +  pc - the preconditioner context
360: .  in - the scatter to move the values in
361: -  out - the scatter to move them out

363:    Level: advanced

365: .keywords: PC, redundant solve
366: @*/
367: PetscErrorCode PCRedundantSetScatter(PC pc,VecScatter in,VecScatter out)
368: {

375:   PetscTryMethod(pc,"PCRedundantSetScatter_C",(PC,VecScatter,VecScatter),(pc,in,out));
376:   return(0);
377: }

379: static PetscErrorCode PCRedundantGetKSP_Redundant(PC pc,KSP *innerksp)
380: {
382:   PC_Redundant   *red = (PC_Redundant*)pc->data;
383:   MPI_Comm       comm,subcomm;
384:   const char     *prefix;

387:   if (!red->psubcomm) {
388:     PCGetOptionsPrefix(pc,&prefix);

390:     PetscObjectGetComm((PetscObject)pc,&comm);
391:     PetscSubcommCreate(comm,&red->psubcomm);
392:     PetscSubcommSetNumber(red->psubcomm,red->nsubcomm);
393:     PetscSubcommSetType(red->psubcomm,PETSC_SUBCOMM_CONTIGUOUS);

395:     PetscSubcommSetOptionsPrefix(red->psubcomm,prefix);
396:     PetscSubcommSetFromOptions(red->psubcomm);
397:     PetscLogObjectMemory((PetscObject)pc,sizeof(PetscSubcomm));

399:     /* create a new PC that processors in each subcomm have copy of */
400:     subcomm = PetscSubcommChild(red->psubcomm);

402:     KSPCreate(subcomm,&red->ksp);
403:     KSPSetErrorIfNotConverged(red->ksp,pc->erroriffailure);
404:     PetscObjectIncrementTabLevel((PetscObject)red->ksp,(PetscObject)pc,1);
405:     PetscLogObjectParent((PetscObject)pc,(PetscObject)red->ksp);
406:     KSPSetType(red->ksp,KSPPREONLY);
407:     KSPGetPC(red->ksp,&red->pc);
408:     PCSetType(red->pc,PCLU);
409:     if (red->shifttypeset) {
410:       PCFactorSetShiftType(red->pc,red->shifttype);
411:       red->shifttypeset = PETSC_FALSE;
412:     }
413:     KSPSetOptionsPrefix(red->ksp,prefix);
414:     KSPAppendOptionsPrefix(red->ksp,"redundant_");
415:   }
416:   *innerksp = red->ksp;
417:   return(0);
418: }

420: /*@
421:    PCRedundantGetKSP - Gets the less parallel KSP created by the redundant PC.

423:    Not Collective

425:    Input Parameter:
426: .  pc - the preconditioner context

428:    Output Parameter:
429: .  innerksp - the KSP on the smaller set of processes

431:    Level: advanced

433: .keywords: PC, redundant solve
434: @*/
435: PetscErrorCode PCRedundantGetKSP(PC pc,KSP *innerksp)
436: {

442:   PetscUseMethod(pc,"PCRedundantGetKSP_C",(PC,KSP*),(pc,innerksp));
443:   return(0);
444: }

446: static PetscErrorCode PCRedundantGetOperators_Redundant(PC pc,Mat *mat,Mat *pmat)
447: {
448:   PC_Redundant *red = (PC_Redundant*)pc->data;

451:   if (mat)  *mat  = red->pmats;
452:   if (pmat) *pmat = red->pmats;
453:   return(0);
454: }

456: /*@
457:    PCRedundantGetOperators - gets the sequential matrix and preconditioner matrix

459:    Not Collective

461:    Input Parameter:
462: .  pc - the preconditioner context

464:    Output Parameters:
465: +  mat - the matrix
466: -  pmat - the (possibly different) preconditioner matrix

468:    Level: advanced

470: .keywords: PC, redundant solve
471: @*/
472: PetscErrorCode PCRedundantGetOperators(PC pc,Mat *mat,Mat *pmat)
473: {

480:   PetscUseMethod(pc,"PCRedundantGetOperators_C",(PC,Mat*,Mat*),(pc,mat,pmat));
481:   return(0);
482: }

484: /* -------------------------------------------------------------------------------------*/
485: /*MC
486:      PCREDUNDANT - Runs a KSP solver with preconditioner for the entire problem on subgroups of processors

488:      Options for the redundant preconditioners can be set with -redundant_pc_xxx for the redundant KSP with -redundant_ksp_xxx

490:   Options Database:
491: .  -pc_redundant_number <n> - number of redundant solves, for example if you are using 64 MPI processes and
492:                               use an n of 4 there will be 4 parallel solves each on 16 = 64/4 processes.

494:    Level: intermediate

496:    Notes: The default KSP is preonly and the default PC is LU.

498:    PCFactorSetShiftType() applied to this PC will convey they shift type into the inner PC if it is factorization based.

500:    Developer Notes: Note that PCSetInitialGuessNonzero()  is not used by this class but likely should be.

502: .seealso:  PCCreate(), PCSetType(), PCType (for list of available types), PCRedundantSetScatter(),
503:            PCRedundantGetKSP(), PCRedundantGetOperators(), PCRedundantSetNumber()
504: M*/

506: PETSC_EXTERN PetscErrorCode PCCreate_Redundant(PC pc)
507: {
509:   PC_Redundant   *red;
510:   PetscMPIInt    size;

513:   PetscNewLog(pc,&red);
514:   MPI_Comm_size(PetscObjectComm((PetscObject)pc),&size);

516:   red->nsubcomm       = size;
517:   red->useparallelmat = PETSC_TRUE;
518:   pc->data            = (void*)red;

520:   pc->ops->apply          = PCApply_Redundant;
521:   pc->ops->applytranspose = PCApplyTranspose_Redundant;
522:   pc->ops->setup          = PCSetUp_Redundant;
523:   pc->ops->destroy        = PCDestroy_Redundant;
524:   pc->ops->reset          = PCReset_Redundant;
525:   pc->ops->setfromoptions = PCSetFromOptions_Redundant;
526:   pc->ops->view           = PCView_Redundant;

528:   PetscObjectComposeFunction((PetscObject)pc,"PCRedundantSetScatter_C",PCRedundantSetScatter_Redundant);
529:   PetscObjectComposeFunction((PetscObject)pc,"PCRedundantSetNumber_C",PCRedundantSetNumber_Redundant);
530:   PetscObjectComposeFunction((PetscObject)pc,"PCRedundantGetKSP_C",PCRedundantGetKSP_Redundant);
531:   PetscObjectComposeFunction((PetscObject)pc,"PCRedundantGetOperators_C",PCRedundantGetOperators_Redundant);
532:   PetscObjectComposeFunction((PetscObject)pc,"PCFactorSetShiftType_C",PCFactorSetShiftType_Redundant);
533:   return(0);
534: }