Actual source code: redundant.c

petsc-3.6.1 2015-07-22
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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: } PC_Redundant;

 22: static PetscErrorCode PCView_Redundant(PC pc,PetscViewer viewer)
 23: {
 24:   PC_Redundant   *red = (PC_Redundant*)pc->data;
 26:   PetscBool      iascii,isstring;
 27:   PetscViewer    subviewer;

 30:   PetscObjectTypeCompare((PetscObject)viewer,PETSCVIEWERASCII,&iascii);
 31:   PetscObjectTypeCompare((PetscObject)viewer,PETSCVIEWERSTRING,&isstring);
 32:   if (iascii) {
 33:     if (!red->psubcomm) {
 34:       PetscViewerASCIIPrintf(viewer,"  Redundant preconditioner: Not yet setup\n");
 35:     } else {
 36:       PetscViewerASCIIPrintf(viewer,"  Redundant preconditioner: First (color=0) of %D PCs follows\n",red->nsubcomm);
 37:       PetscViewerGetSubcomm(viewer,((PetscObject)red->pc)->comm,&subviewer);
 38:       if (!red->psubcomm->color) { /* only view first redundant pc */
 39:         PetscViewerASCIIPushTab(viewer);
 40:         KSPView(red->ksp,subviewer);
 41:         PetscViewerASCIIPopTab(viewer);
 42:       }
 43:       PetscViewerRestoreSubcomm(viewer,((PetscObject)red->pc)->comm,&subviewer);
 44:     }
 45:   } else if (isstring) {
 46:     PetscViewerStringSPrintf(viewer," Redundant solver preconditioner");
 47:   }
 48:   return(0);
 49: }

 53: static PetscErrorCode PCSetUp_Redundant(PC pc)
 54: {
 55:   PC_Redundant   *red = (PC_Redundant*)pc->data;
 57:   PetscInt       mstart,mend,mlocal,M;
 58:   PetscMPIInt    size;
 59:   MPI_Comm       comm,subcomm;
 60:   Vec            x;
 61:   const char     *prefix;

 64:   PetscObjectGetComm((PetscObject)pc,&comm);
 65: 
 66:   /* if pmatrix set by user is sequential then we do not need to gather the parallel matrix */
 67:   MPI_Comm_size(comm,&size);
 68:   if (size == 1) red->useparallelmat = PETSC_FALSE;

 70:   if (!pc->setupcalled) {
 71:     PetscInt mloc_sub;
 72:     if (!red->psubcomm) {
 73:       PetscSubcommCreate(comm,&red->psubcomm);
 74:       PetscSubcommSetNumber(red->psubcomm,red->nsubcomm);
 75:       PetscSubcommSetType(red->psubcomm,PETSC_SUBCOMM_CONTIGUOUS);
 76:       /* enable runtime switch of psubcomm type, e.g., '-psubcomm_type interlaced */
 77:       PetscSubcommSetFromOptions(red->psubcomm);
 78:       PetscLogObjectMemory((PetscObject)pc,sizeof(PetscSubcomm));

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

 83:       KSPCreate(subcomm,&red->ksp);
 84:       KSPSetErrorIfNotConverged(red->ksp,pc->erroriffailure);
 85:       PetscObjectIncrementTabLevel((PetscObject)red->ksp,(PetscObject)pc,1);
 86:       PetscLogObjectParent((PetscObject)pc,(PetscObject)red->ksp);
 87:       KSPSetType(red->ksp,KSPPREONLY);
 88:       KSPGetPC(red->ksp,&red->pc);
 89:       PCSetType(red->pc,PCLU);

 91:       PCGetOptionsPrefix(pc,&prefix);
 92:       KSPSetOptionsPrefix(red->ksp,prefix);
 93:       KSPAppendOptionsPrefix(red->ksp,"redundant_");
 94:     } else {
 95:       subcomm = PetscSubcommChild(red->psubcomm);
 96:     }

 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);
101:       KSPSetOperators(red->ksp,red->pmats,red->pmats);
102: 
103:       /* get working vectors xsub and ysub */
104:       MatCreateVecs(red->pmats,&red->xsub,&red->ysub);

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

114:       /* create vecscatters */
115:       if (!red->scatterin) { /* efficiency of scatterin is independent from psubcomm_type! */
116:         IS       is1,is2;
117:         PetscInt *idx1,*idx2,i,j,k;

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

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

168:   if (pc->setfromoptionscalled) {
169:     KSPSetFromOptions(red->ksp);
170:   }
171:   KSPSetUp(red->ksp);
172:   return(0);
173: }

177: static PetscErrorCode PCApply_Redundant(PC pc,Vec x,Vec y)
178: {
179:   PC_Redundant   *red = (PC_Redundant*)pc->data;
181:   PetscScalar    *array;

184:   if (!red->useparallelmat) {
185:     KSPSolve(red->ksp,x,y);
186:     return(0);
187:   }

189:   /* scatter x to xdup */
190:   VecScatterBegin(red->scatterin,x,red->xdup,INSERT_VALUES,SCATTER_FORWARD);
191:   VecScatterEnd(red->scatterin,x,red->xdup,INSERT_VALUES,SCATTER_FORWARD);

193:   /* place xdup's local array into xsub */
194:   VecGetArray(red->xdup,&array);
195:   VecPlaceArray(red->xsub,(const PetscScalar*)array);

197:   /* apply preconditioner on each processor */
198:   KSPSolve(red->ksp,red->xsub,red->ysub);
199:   VecResetArray(red->xsub);
200:   VecRestoreArray(red->xdup,&array);

202:   /* place ysub's local array into ydup */
203:   VecGetArray(red->ysub,&array);
204:   VecPlaceArray(red->ydup,(const PetscScalar*)array);

206:   /* scatter ydup to y */
207:   VecScatterBegin(red->scatterout,red->ydup,y,INSERT_VALUES,SCATTER_FORWARD);
208:   VecScatterEnd(red->scatterout,red->ydup,y,INSERT_VALUES,SCATTER_FORWARD);
209:   VecResetArray(red->ydup);
210:   VecRestoreArray(red->ysub,&array);
211:   return(0);
212: }

216: static PetscErrorCode PCApplyTranspose_Redundant(PC pc,Vec x,Vec y)
217: {
218:   PC_Redundant   *red = (PC_Redundant*)pc->data;
220:   PetscScalar    *array;

223:   if (!red->useparallelmat) {
224:     KSPSolveTranspose(red->ksp,x,y);
225:     return(0);
226:   }

228:   /* scatter x to xdup */
229:   VecScatterBegin(red->scatterin,x,red->xdup,INSERT_VALUES,SCATTER_FORWARD);
230:   VecScatterEnd(red->scatterin,x,red->xdup,INSERT_VALUES,SCATTER_FORWARD);

232:   /* place xdup's local array into xsub */
233:   VecGetArray(red->xdup,&array);
234:   VecPlaceArray(red->xsub,(const PetscScalar*)array);

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

241:   /* place ysub's local array into ydup */
242:   VecGetArray(red->ysub,&array);
243:   VecPlaceArray(red->ydup,(const PetscScalar*)array);

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

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

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

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

282:   PCReset_Redundant(pc);
283:   KSPDestroy(&red->ksp);
284:   PetscSubcommDestroy(&red->psubcomm);
285:   PetscFree(pc->data);
286:   return(0);
287: }

291: static PetscErrorCode PCSetFromOptions_Redundant(PetscOptions *PetscOptionsObject,PC pc)
292: {
294:   PC_Redundant   *red = (PC_Redundant*)pc->data;

297:   PetscOptionsHead(PetscOptionsObject,"Redundant options");
298:   PetscOptionsInt("-pc_redundant_number","Number of redundant pc","PCRedundantSetNumber",red->nsubcomm,&red->nsubcomm,0);
299:   PetscOptionsTail();
300:   return(0);
301: }

305: static PetscErrorCode  PCRedundantSetNumber_Redundant(PC pc,PetscInt nreds)
306: {
307:   PC_Redundant *red = (PC_Redundant*)pc->data;

310:   red->nsubcomm = nreds;
311:   return(0);
312: }

316: /*@
317:    PCRedundantSetNumber - Sets the number of redundant preconditioner contexts.

319:    Logically Collective on PC

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

326:    Level: advanced

328: .keywords: PC, redundant solve
329: @*/
330: PetscErrorCode  PCRedundantSetNumber(PC pc,PetscInt nredundant)
331: {

336:   if (nredundant <= 0) SETERRQ1(PetscObjectComm((PetscObject)pc),PETSC_ERR_ARG_WRONG, "num of redundant pc %D must be positive",nredundant);
337:   PetscTryMethod(pc,"PCRedundantSetNumber_C",(PC,PetscInt),(pc,nredundant));
338:   return(0);
339: }

343: static PetscErrorCode  PCRedundantSetScatter_Redundant(PC pc,VecScatter in,VecScatter out)
344: {
345:   PC_Redundant   *red = (PC_Redundant*)pc->data;

349:   PetscObjectReference((PetscObject)in);
350:   VecScatterDestroy(&red->scatterin);

352:   red->scatterin  = in;

354:   PetscObjectReference((PetscObject)out);
355:   VecScatterDestroy(&red->scatterout);
356:   red->scatterout = out;
357:   return(0);
358: }

362: /*@
363:    PCRedundantSetScatter - Sets the scatter used to copy values into the
364:      redundant local solve and the scatter to move them back into the global
365:      vector.

367:    Logically Collective on PC

369:    Input Parameters:
370: +  pc - the preconditioner context
371: .  in - the scatter to move the values in
372: -  out - the scatter to move them out

374:    Level: advanced

376: .keywords: PC, redundant solve
377: @*/
378: PetscErrorCode  PCRedundantSetScatter(PC pc,VecScatter in,VecScatter out)
379: {

386:   PetscTryMethod(pc,"PCRedundantSetScatter_C",(PC,VecScatter,VecScatter),(pc,in,out));
387:   return(0);
388: }

392: static PetscErrorCode  PCRedundantGetKSP_Redundant(PC pc,KSP *innerksp)
393: {
395:   PC_Redundant   *red = (PC_Redundant*)pc->data;
396:   MPI_Comm       comm,subcomm;
397:   const char     *prefix;

400:   if (!red->psubcomm) {
401:     PetscObjectGetComm((PetscObject)pc,&comm);
402:     PetscSubcommCreate(comm,&red->psubcomm);
403:     PetscSubcommSetNumber(red->psubcomm,red->nsubcomm);
404:     PetscSubcommSetType(red->psubcomm,PETSC_SUBCOMM_INTERLACED);
405:     PetscLogObjectMemory((PetscObject)pc,sizeof(PetscSubcomm));

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

410:     KSPCreate(subcomm,&red->ksp);
411:     KSPSetErrorIfNotConverged(red->ksp,pc->erroriffailure);
412:     PetscObjectIncrementTabLevel((PetscObject)red->ksp,(PetscObject)pc,1);
413:     PetscLogObjectParent((PetscObject)pc,(PetscObject)red->ksp);
414:     KSPSetType(red->ksp,KSPPREONLY);
415:     KSPGetPC(red->ksp,&red->pc);
416:     PCSetType(red->pc,PCLU);

418:     PCGetOptionsPrefix(pc,&prefix);
419:     KSPSetOptionsPrefix(red->ksp,prefix);
420:     KSPAppendOptionsPrefix(red->ksp,"redundant_");
421:   }
422:   *innerksp = red->ksp;
423:   return(0);
424: }

428: /*@
429:    PCRedundantGetKSP - Gets the less parallel KSP created by the redundant PC.

431:    Not Collective

433:    Input Parameter:
434: .  pc - the preconditioner context

436:    Output Parameter:
437: .  innerksp - the KSP on the smaller set of processes

439:    Level: advanced

441: .keywords: PC, redundant solve
442: @*/
443: PetscErrorCode  PCRedundantGetKSP(PC pc,KSP *innerksp)
444: {

450:   PetscTryMethod(pc,"PCRedundantGetKSP_C",(PC,KSP*),(pc,innerksp));
451:   return(0);
452: }

456: static PetscErrorCode  PCRedundantGetOperators_Redundant(PC pc,Mat *mat,Mat *pmat)
457: {
458:   PC_Redundant *red = (PC_Redundant*)pc->data;

461:   if (mat)  *mat  = red->pmats;
462:   if (pmat) *pmat = red->pmats;
463:   return(0);
464: }

468: /*@
469:    PCRedundantGetOperators - gets the sequential matrix and preconditioner matrix

471:    Not Collective

473:    Input Parameter:
474: .  pc - the preconditioner context

476:    Output Parameters:
477: +  mat - the matrix
478: -  pmat - the (possibly different) preconditioner matrix

480:    Level: advanced

482: .keywords: PC, redundant solve
483: @*/
484: PetscErrorCode  PCRedundantGetOperators(PC pc,Mat *mat,Mat *pmat)
485: {

492:   PetscTryMethod(pc,"PCRedundantGetOperators_C",(PC,Mat*,Mat*),(pc,mat,pmat));
493:   return(0);
494: }

496: /* -------------------------------------------------------------------------------------*/
497: /*MC
498:      PCREDUNDANT - Runs a KSP solver with preconditioner for the entire problem on subgroups of processors

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

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

506:    Level: intermediate

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

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

512: .seealso:  PCCreate(), PCSetType(), PCType (for list of available types), PCRedundantSetScatter(),
513:            PCRedundantGetKSP(), PCRedundantGetOperators(), PCRedundantSetNumber()
514: M*/

518: PETSC_EXTERN PetscErrorCode PCCreate_Redundant(PC pc)
519: {
521:   PC_Redundant   *red;
522:   PetscMPIInt    size;

525:   PetscNewLog(pc,&red);
526:   MPI_Comm_size(PetscObjectComm((PetscObject)pc),&size);

528:   red->nsubcomm       = size;
529:   red->useparallelmat = PETSC_TRUE;
530:   pc->data            = (void*)red;

532:   pc->ops->apply          = PCApply_Redundant;
533:   pc->ops->applytranspose = PCApplyTranspose_Redundant;
534:   pc->ops->setup          = PCSetUp_Redundant;
535:   pc->ops->destroy        = PCDestroy_Redundant;
536:   pc->ops->reset          = PCReset_Redundant;
537:   pc->ops->setfromoptions = PCSetFromOptions_Redundant;
538:   pc->ops->view           = PCView_Redundant;

540:   PetscObjectComposeFunction((PetscObject)pc,"PCRedundantSetScatter_C",PCRedundantSetScatter_Redundant);
541:   PetscObjectComposeFunction((PetscObject)pc,"PCRedundantSetNumber_C",PCRedundantSetNumber_Redundant);
542:   PetscObjectComposeFunction((PetscObject)pc,"PCRedundantGetKSP_C",PCRedundantGetKSP_Redundant);
543:   PetscObjectComposeFunction((PetscObject)pc,"PCRedundantGetOperators_C",PCRedundantGetOperators_Redundant);
544:   return(0);
545: }