Actual source code: redundant.c

petsc-3.7.4 2016-10-02
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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>           /*I "petscksp.h" I*/

  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;

 24: PetscErrorCode  PCFactorSetShiftType_Redundant(PC pc,MatFactorShiftType shifttype)
 25: {
 26:   PC_Redundant   *red = (PC_Redundant*)pc->data;

 30:   if (red->ksp) {
 31:     PC pc;
 32:     KSPGetPC(red->ksp,&pc);
 33:     PCFactorSetShiftType(pc,shifttype);
 34:   } else {
 35:     red->shifttypeset = PETSC_TRUE;
 36:     red->shifttype    = shifttype;
 37:   }
 38:   return(0);
 39: }

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

 51:   PetscObjectTypeCompare((PetscObject)viewer,PETSCVIEWERASCII,&iascii);
 52:   PetscObjectTypeCompare((PetscObject)viewer,PETSCVIEWERSTRING,&isstring);
 53:   if (iascii) {
 54:     if (!red->psubcomm) {
 55:       PetscViewerASCIIPrintf(viewer,"  Redundant preconditioner: Not yet setup\n");
 56:     } else {
 57:       PetscViewerASCIIPrintf(viewer,"  Redundant preconditioner: First (color=0) of %D PCs follows\n",red->nsubcomm);
 58:       PetscViewerGetSubViewer(viewer,((PetscObject)red->pc)->comm,&subviewer);
 59:       if (!red->psubcomm->color) { /* only view first redundant pc */
 60:         PetscViewerASCIIPushTab(subviewer);
 61:         KSPView(red->ksp,subviewer);
 62:         PetscViewerASCIIPopTab(subviewer);
 63:       }
 64:       PetscViewerRestoreSubViewer(viewer,((PetscObject)red->pc)->comm,&subviewer);
 65:     }
 66:   } else if (isstring) {
 67:     PetscViewerStringSPrintf(viewer," Redundant solver preconditioner");
 68:   }
 69:   return(0);
 70: }

 74: static PetscErrorCode PCSetUp_Redundant(PC pc)
 75: {
 76:   PC_Redundant   *red = (PC_Redundant*)pc->data;
 78:   PetscInt       mstart,mend,mlocal,M;
 79:   PetscMPIInt    size;
 80:   MPI_Comm       comm,subcomm;
 81:   Vec            x;

 84:   PetscObjectGetComm((PetscObject)pc,&comm);
 85: 
 86:   /* if pmatrix set by user is sequential then we do not need to gather the parallel matrix */
 87:   MPI_Comm_size(comm,&size);
 88:   if (size == 1) red->useparallelmat = PETSC_FALSE;

 90:   if (!pc->setupcalled) {
 91:     PetscInt mloc_sub;
 92:     if (!red->psubcomm) { /* create red->psubcomm, new ksp and pc over subcomm */
 93:       KSP ksp;
 94:       PCRedundantGetKSP(pc,&ksp);
 95:     }
 96:     subcomm = PetscSubcommChild(red->psubcomm);

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

102:       MPI_Comm_size(subcomm,&size);
103:       if (size > 1) {
104:         PetscBool foundpack;
105:         MatGetFactorAvailable(red->pmats,NULL,MAT_FACTOR_LU,&foundpack);
106:         if (!foundpack) { /* reset default ksp and pc */
107:           KSPSetType(red->ksp,KSPGMRES);
108:           PCSetType(red->pc,PCBJACOBI);
109:         } else {
110:           PCFactorSetMatSolverPackage(red->pc,NULL);
111:         }
112:       }

114:       KSPSetOperators(red->ksp,red->pmats,red->pmats);
115: 
116:       /* get working vectors xsub and ysub */
117:       MatCreateVecs(red->pmats,&red->xsub,&red->ysub);

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

127:       /* create vecscatters */
128:       if (!red->scatterin) { /* efficiency of scatterin is independent from psubcomm_type! */
129:         IS       is1,is2;
130:         PetscInt *idx1,*idx2,i,j,k;

132:         MatCreateVecs(pc->pmat,&x,0);
133:         VecGetSize(x,&M);
134:         VecGetOwnershipRange(x,&mstart,&mend);
135:         mlocal = mend - mstart;
136:         PetscMalloc2(red->psubcomm->n*mlocal,&idx1,red->psubcomm->n*mlocal,&idx2);
137:         j    = 0;
138:         for (k=0; k<red->psubcomm->n; k++) {
139:           for (i=mstart; i<mend; i++) {
140:             idx1[j]   = i;
141:             idx2[j++] = i + M*k;
142:           }
143:         }
144:         ISCreateGeneral(comm,red->psubcomm->n*mlocal,idx1,PETSC_COPY_VALUES,&is1);
145:         ISCreateGeneral(comm,red->psubcomm->n*mlocal,idx2,PETSC_COPY_VALUES,&is2);
146:         VecScatterCreate(x,is1,red->xdup,is2,&red->scatterin);
147:         ISDestroy(&is1);
148:         ISDestroy(&is2);

150:         /* Impl below is good for PETSC_SUBCOMM_INTERLACED (no inter-process communication) and PETSC_SUBCOMM_CONTIGUOUS (communication within subcomm) */
151:         ISCreateStride(comm,mlocal,mstart+ red->psubcomm->color*M,1,&is1);
152:         ISCreateStride(comm,mlocal,mstart,1,&is2);
153:         VecScatterCreate(red->xdup,is1,x,is2,&red->scatterout);
154:         ISDestroy(&is1);
155:         ISDestroy(&is2);
156:         PetscFree2(idx1,idx2);
157:         VecDestroy(&x);
158:       }
159:     } else { /* !red->useparallelmat */
160:       KSPSetOperators(red->ksp,pc->mat,pc->pmat);
161:     }
162:   } else { /* pc->setupcalled */
163:     if (red->useparallelmat) {
164:       MatReuse       reuse;
165:       /* grab the parallel matrix and put it into processors of a subcomminicator */
166:       /*--------------------------------------------------------------------------*/
167:       if (pc->flag == DIFFERENT_NONZERO_PATTERN) {
168:         /* destroy old matrices */
169:         MatDestroy(&red->pmats);
170:         reuse = MAT_INITIAL_MATRIX;
171:       } else {
172:         reuse = MAT_REUSE_MATRIX;
173:       }
174:       MatCreateRedundantMatrix(pc->pmat,red->psubcomm->n,PetscSubcommChild(red->psubcomm),reuse,&red->pmats);
175:       KSPSetOperators(red->ksp,red->pmats,red->pmats);
176:     } else { /* !red->useparallelmat */
177:       KSPSetOperators(red->ksp,pc->mat,pc->pmat);
178:     }
179:   }

181:   if (pc->setfromoptionscalled) {
182:     KSPSetFromOptions(red->ksp);
183:   }
184:   KSPSetUp(red->ksp);
185:   return(0);
186: }

190: static PetscErrorCode PCApply_Redundant(PC pc,Vec x,Vec y)
191: {
192:   PC_Redundant   *red = (PC_Redundant*)pc->data;
194:   PetscScalar    *array;

197:   if (!red->useparallelmat) {
198:     KSPSolve(red->ksp,x,y);
199:     return(0);
200:   }

202:   /* scatter x to xdup */
203:   VecScatterBegin(red->scatterin,x,red->xdup,INSERT_VALUES,SCATTER_FORWARD);
204:   VecScatterEnd(red->scatterin,x,red->xdup,INSERT_VALUES,SCATTER_FORWARD);

206:   /* place xdup's local array into xsub */
207:   VecGetArray(red->xdup,&array);
208:   VecPlaceArray(red->xsub,(const PetscScalar*)array);

210:   /* apply preconditioner on each processor */
211:   KSPSolve(red->ksp,red->xsub,red->ysub);
212:   VecResetArray(red->xsub);
213:   VecRestoreArray(red->xdup,&array);

215:   /* place ysub's local array into ydup */
216:   VecGetArray(red->ysub,&array);
217:   VecPlaceArray(red->ydup,(const PetscScalar*)array);

219:   /* scatter ydup to y */
220:   VecScatterBegin(red->scatterout,red->ydup,y,INSERT_VALUES,SCATTER_FORWARD);
221:   VecScatterEnd(red->scatterout,red->ydup,y,INSERT_VALUES,SCATTER_FORWARD);
222:   VecResetArray(red->ydup);
223:   VecRestoreArray(red->ysub,&array);
224:   return(0);
225: }

229: static PetscErrorCode PCApplyTranspose_Redundant(PC pc,Vec x,Vec y)
230: {
231:   PC_Redundant   *red = (PC_Redundant*)pc->data;
233:   PetscScalar    *array;

236:   if (!red->useparallelmat) {
237:     KSPSolveTranspose(red->ksp,x,y);
238:     return(0);
239:   }

241:   /* scatter x to xdup */
242:   VecScatterBegin(red->scatterin,x,red->xdup,INSERT_VALUES,SCATTER_FORWARD);
243:   VecScatterEnd(red->scatterin,x,red->xdup,INSERT_VALUES,SCATTER_FORWARD);

245:   /* place xdup's local array into xsub */
246:   VecGetArray(red->xdup,&array);
247:   VecPlaceArray(red->xsub,(const PetscScalar*)array);

249:   /* apply preconditioner on each processor */
250:   KSPSolveTranspose(red->ksp,red->xsub,red->ysub);
251:   VecResetArray(red->xsub);
252:   VecRestoreArray(red->xdup,&array);

254:   /* place ysub's local array into ydup */
255:   VecGetArray(red->ysub,&array);
256:   VecPlaceArray(red->ydup,(const PetscScalar*)array);

258:   /* scatter ydup to y */
259:   VecScatterBegin(red->scatterout,red->ydup,y,INSERT_VALUES,SCATTER_FORWARD);
260:   VecScatterEnd(red->scatterout,red->ydup,y,INSERT_VALUES,SCATTER_FORWARD);
261:   VecResetArray(red->ydup);
262:   VecRestoreArray(red->ysub,&array);
263:   return(0);
264: }

268: static PetscErrorCode PCReset_Redundant(PC pc)
269: {
270:   PC_Redundant   *red = (PC_Redundant*)pc->data;

274:   if (red->useparallelmat) {
275:     VecScatterDestroy(&red->scatterin);
276:     VecScatterDestroy(&red->scatterout);
277:     VecDestroy(&red->ysub);
278:     VecDestroy(&red->xsub);
279:     VecDestroy(&red->xdup);
280:     VecDestroy(&red->ydup);
281:   }
282:   MatDestroy(&red->pmats);
283:   KSPReset(red->ksp);
284:   return(0);
285: }

289: static PetscErrorCode PCDestroy_Redundant(PC pc)
290: {
291:   PC_Redundant   *red = (PC_Redundant*)pc->data;

295:   PCReset_Redundant(pc);
296:   KSPDestroy(&red->ksp);
297:   PetscSubcommDestroy(&red->psubcomm);
298:   PetscFree(pc->data);
299:   return(0);
300: }

304: static PetscErrorCode PCSetFromOptions_Redundant(PetscOptionItems *PetscOptionsObject,PC pc)
305: {
307:   PC_Redundant   *red = (PC_Redundant*)pc->data;

310:   PetscOptionsHead(PetscOptionsObject,"Redundant options");
311:   PetscOptionsInt("-pc_redundant_number","Number of redundant pc","PCRedundantSetNumber",red->nsubcomm,&red->nsubcomm,0);
312:   PetscOptionsTail();
313:   return(0);
314: }

318: static PetscErrorCode PCRedundantSetNumber_Redundant(PC pc,PetscInt nreds)
319: {
320:   PC_Redundant *red = (PC_Redundant*)pc->data;

323:   red->nsubcomm = nreds;
324:   return(0);
325: }

329: /*@
330:    PCRedundantSetNumber - Sets the number of redundant preconditioner contexts.

332:    Logically Collective on PC

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

339:    Level: advanced

341: .keywords: PC, redundant solve
342: @*/
343: PetscErrorCode PCRedundantSetNumber(PC pc,PetscInt nredundant)
344: {

349:   if (nredundant <= 0) SETERRQ1(PetscObjectComm((PetscObject)pc),PETSC_ERR_ARG_WRONG, "num of redundant pc %D must be positive",nredundant);
350:   PetscTryMethod(pc,"PCRedundantSetNumber_C",(PC,PetscInt),(pc,nredundant));
351:   return(0);
352: }

356: static PetscErrorCode PCRedundantSetScatter_Redundant(PC pc,VecScatter in,VecScatter out)
357: {
358:   PC_Redundant   *red = (PC_Redundant*)pc->data;

362:   PetscObjectReference((PetscObject)in);
363:   VecScatterDestroy(&red->scatterin);

365:   red->scatterin  = in;

367:   PetscObjectReference((PetscObject)out);
368:   VecScatterDestroy(&red->scatterout);
369:   red->scatterout = out;
370:   return(0);
371: }

375: /*@
376:    PCRedundantSetScatter - Sets the scatter used to copy values into the
377:      redundant local solve and the scatter to move them back into the global
378:      vector.

380:    Logically Collective on PC

382:    Input Parameters:
383: +  pc - the preconditioner context
384: .  in - the scatter to move the values in
385: -  out - the scatter to move them out

387:    Level: advanced

389: .keywords: PC, redundant solve
390: @*/
391: PetscErrorCode PCRedundantSetScatter(PC pc,VecScatter in,VecScatter out)
392: {

399:   PetscTryMethod(pc,"PCRedundantSetScatter_C",(PC,VecScatter,VecScatter),(pc,in,out));
400:   return(0);
401: }

405: static PetscErrorCode PCRedundantGetKSP_Redundant(PC pc,KSP *innerksp)
406: {
408:   PC_Redundant   *red = (PC_Redundant*)pc->data;
409:   MPI_Comm       comm,subcomm;
410:   const char     *prefix;

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

416:     PetscObjectGetComm((PetscObject)pc,&comm);
417:     PetscSubcommCreate(comm,&red->psubcomm);
418:     PetscSubcommSetNumber(red->psubcomm,red->nsubcomm);
419:     PetscSubcommSetType(red->psubcomm,PETSC_SUBCOMM_CONTIGUOUS);

421:     PetscSubcommSetOptionsPrefix(red->psubcomm,prefix);
422:     PetscSubcommSetFromOptions(red->psubcomm);
423:     PetscLogObjectMemory((PetscObject)pc,sizeof(PetscSubcomm));

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

428:     KSPCreate(subcomm,&red->ksp);
429:     KSPSetErrorIfNotConverged(red->ksp,pc->erroriffailure);
430:     PetscObjectIncrementTabLevel((PetscObject)red->ksp,(PetscObject)pc,1);
431:     PetscLogObjectParent((PetscObject)pc,(PetscObject)red->ksp);
432:     KSPSetType(red->ksp,KSPPREONLY);
433:     KSPGetPC(red->ksp,&red->pc);
434:     PCSetType(red->pc,PCLU);
435:     if (red->shifttypeset) {
436:       PCFactorSetShiftType(red->pc,red->shifttype);
437:       red->shifttypeset = PETSC_FALSE;
438:     }
439:     KSPSetOptionsPrefix(red->ksp,prefix);
440:     KSPAppendOptionsPrefix(red->ksp,"redundant_");
441:   }
442:   *innerksp = red->ksp;
443:   return(0);
444: }

448: /*@
449:    PCRedundantGetKSP - Gets the less parallel KSP created by the redundant PC.

451:    Not Collective

453:    Input Parameter:
454: .  pc - the preconditioner context

456:    Output Parameter:
457: .  innerksp - the KSP on the smaller set of processes

459:    Level: advanced

461: .keywords: PC, redundant solve
462: @*/
463: PetscErrorCode PCRedundantGetKSP(PC pc,KSP *innerksp)
464: {

470:   PetscUseMethod(pc,"PCRedundantGetKSP_C",(PC,KSP*),(pc,innerksp));
471:   return(0);
472: }

476: static PetscErrorCode PCRedundantGetOperators_Redundant(PC pc,Mat *mat,Mat *pmat)
477: {
478:   PC_Redundant *red = (PC_Redundant*)pc->data;

481:   if (mat)  *mat  = red->pmats;
482:   if (pmat) *pmat = red->pmats;
483:   return(0);
484: }

488: /*@
489:    PCRedundantGetOperators - gets the sequential matrix and preconditioner matrix

491:    Not Collective

493:    Input Parameter:
494: .  pc - the preconditioner context

496:    Output Parameters:
497: +  mat - the matrix
498: -  pmat - the (possibly different) preconditioner matrix

500:    Level: advanced

502: .keywords: PC, redundant solve
503: @*/
504: PetscErrorCode PCRedundantGetOperators(PC pc,Mat *mat,Mat *pmat)
505: {

512:   PetscUseMethod(pc,"PCRedundantGetOperators_C",(PC,Mat*,Mat*),(pc,mat,pmat));
513:   return(0);
514: }

516: /* -------------------------------------------------------------------------------------*/
517: /*MC
518:      PCREDUNDANT - Runs a KSP solver with preconditioner for the entire problem on subgroups of processors

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

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

526:    Level: intermediate

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

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

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

534: .seealso:  PCCreate(), PCSetType(), PCType (for list of available types), PCRedundantSetScatter(),
535:            PCRedundantGetKSP(), PCRedundantGetOperators(), PCRedundantSetNumber()
536: M*/

540: PETSC_EXTERN PetscErrorCode PCCreate_Redundant(PC pc)
541: {
543:   PC_Redundant   *red;
544:   PetscMPIInt    size;

547:   PetscNewLog(pc,&red);
548:   MPI_Comm_size(PetscObjectComm((PetscObject)pc),&size);

550:   red->nsubcomm       = size;
551:   red->useparallelmat = PETSC_TRUE;
552:   pc->data            = (void*)red;

554:   pc->ops->apply          = PCApply_Redundant;
555:   pc->ops->applytranspose = PCApplyTranspose_Redundant;
556:   pc->ops->setup          = PCSetUp_Redundant;
557:   pc->ops->destroy        = PCDestroy_Redundant;
558:   pc->ops->reset          = PCReset_Redundant;
559:   pc->ops->setfromoptions = PCSetFromOptions_Redundant;
560:   pc->ops->view           = PCView_Redundant;

562:   PetscObjectComposeFunction((PetscObject)pc,"PCRedundantSetScatter_C",PCRedundantSetScatter_Redundant);
563:   PetscObjectComposeFunction((PetscObject)pc,"PCRedundantSetNumber_C",PCRedundantSetNumber_Redundant);
564:   PetscObjectComposeFunction((PetscObject)pc,"PCRedundantGetKSP_C",PCRedundantGetKSP_Redundant);
565:   PetscObjectComposeFunction((PetscObject)pc,"PCRedundantGetOperators_C",PCRedundantGetOperators_Redundant);
566:   PetscObjectComposeFunction((PetscObject)pc,"PCFactorSetShiftType_C",PCFactorSetShiftType_Redundant);
567:   return(0);
568: }