Actual source code: redundant.c

petsc-3.4.4 2014-03-13
  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,mlocal_sub,rstart_sub,rend_sub,mloc_sub;
 58:   PetscMPIInt    size;
 59:   MatReuse       reuse = MAT_INITIAL_MATRIX;
 60:   MatStructure   str   = DIFFERENT_NONZERO_PATTERN;
 61:   MPI_Comm       comm,subcomm;
 62:   Vec            vec;
 63:   PetscMPIInt    subsize,subrank;
 64:   const char     *prefix;
 65:   const PetscInt *range;

 68:   PetscObjectGetComm((PetscObject)pc,&comm);
 69:   MatGetVecs(pc->pmat,&vec,0);
 70:   VecGetSize(vec,&m);

 72:   if (!pc->setupcalled) {
 73:     if (!red->psubcomm) {
 74:       PetscSubcommCreate(comm,&red->psubcomm);
 75:       PetscSubcommSetNumber(red->psubcomm,red->nsubcomm);
 76:       PetscSubcommSetType(red->psubcomm,PETSC_SUBCOMM_INTERLACED);
 77:       PetscLogObjectMemory(pc,sizeof(PetscSubcomm));

 79:       /* create a new PC that processors in each subcomm have copy of */
 80:       subcomm = red->psubcomm->comm;

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

 89:       PCGetOptionsPrefix(pc,&prefix);
 90:       KSPSetOptionsPrefix(red->ksp,prefix);
 91:       KSPAppendOptionsPrefix(red->ksp,"redundant_");
 92:     } else subcomm = red->psubcomm->comm;

 94:     /* create working vectors xsub/ysub and xdup/ydup */
 95:     VecGetLocalSize(vec,&mlocal);
 96:     VecGetOwnershipRange(vec,&mstart,&mend);

 98:     /* get local size of xsub/ysub */
 99:     MPI_Comm_size(subcomm,&subsize);
100:     MPI_Comm_rank(subcomm,&subrank);
101:     MatGetOwnershipRanges(pc->pmat,&range);
102:     rstart_sub = range[red->psubcomm->n*subrank]; /* rstart in xsub/ysub */
103:     if (subrank+1 < subsize) rend_sub = range[red->psubcomm->n*(subrank+1)];
104:     else rend_sub = m;

106:     mloc_sub = rend_sub - rstart_sub;
107:     VecCreateMPI(subcomm,mloc_sub,PETSC_DECIDE,&red->ysub);
108:     /* create xsub with empty local arrays, because xdup's arrays will be placed into it */
109:     VecCreateMPIWithArray(subcomm,1,mloc_sub,PETSC_DECIDE,NULL,&red->xsub);

111:     /* create xdup and ydup. ydup has empty local arrays because ysub's arrays will be place into it.
112:        Note: we use communicator dupcomm, not PetscObjectComm((PetscObject)pc)! */
113:     VecCreateMPI(red->psubcomm->dupparent,mloc_sub,PETSC_DECIDE,&red->xdup);
114:     VecCreateMPIWithArray(red->psubcomm->dupparent,1,mloc_sub,PETSC_DECIDE,NULL,&red->ydup);

116:     /* create vec scatters */
117:     if (!red->scatterin) {
118:       IS       is1,is2;
119:       PetscInt *idx1,*idx2,i,j,k;

121:       PetscMalloc2(red->psubcomm->n*mlocal,PetscInt,&idx1,red->psubcomm->n*mlocal,PetscInt,&idx2);
122:       j    = 0;
123:       for (k=0; k<red->psubcomm->n; k++) {
124:         for (i=mstart; i<mend; i++) {
125:           idx1[j]   = i;
126:           idx2[j++] = i + m*k;
127:         }
128:       }
129:       ISCreateGeneral(comm,red->psubcomm->n*mlocal,idx1,PETSC_COPY_VALUES,&is1);
130:       ISCreateGeneral(comm,red->psubcomm->n*mlocal,idx2,PETSC_COPY_VALUES,&is2);
131:       VecScatterCreate(vec,is1,red->xdup,is2,&red->scatterin);
132:       ISDestroy(&is1);
133:       ISDestroy(&is2);

135:       ISCreateStride(comm,mlocal,mstart+ red->psubcomm->color*m,1,&is1);
136:       ISCreateStride(comm,mlocal,mstart,1,&is2);
137:       VecScatterCreate(red->xdup,is1,vec,is2,&red->scatterout);
138:       ISDestroy(&is1);
139:       ISDestroy(&is2);
140:       PetscFree2(idx1,idx2);
141:     }
142:   }
143:   VecDestroy(&vec);

145:   /* if pmatrix set by user is sequential then we do not need to gather the parallel matrix */
146:   MPI_Comm_size(comm,&size);
147:   if (size == 1) red->useparallelmat = PETSC_FALSE;

149:   if (red->useparallelmat) {
150:     if (pc->setupcalled == 1 && pc->flag == DIFFERENT_NONZERO_PATTERN) {
151:       /* destroy old matrices */
152:       MatDestroy(&red->pmats);
153:     } else if (pc->setupcalled == 1) {
154:       reuse = MAT_REUSE_MATRIX;
155:       str   = SAME_NONZERO_PATTERN;
156:     }

158:     /* grab the parallel matrix and put it into processors of a subcomminicator */
159:     /*--------------------------------------------------------------------------*/
160:     VecGetLocalSize(red->ysub,&mlocal_sub);
161:     MatGetRedundantMatrix(pc->pmat,red->psubcomm->n,red->psubcomm->comm,mlocal_sub,reuse,&red->pmats);
162:     /* tell PC of the subcommunicator its operators */
163:     KSPSetOperators(red->ksp,red->pmats,red->pmats,str);
164:   } else {
165:     KSPSetOperators(red->ksp,pc->mat,pc->pmat,pc->flag);
166:   }
167:   if (pc->setfromoptionscalled) {
168:     KSPSetFromOptions(red->ksp);
169:   }
170:   KSPSetUp(red->ksp);
171:   return(0);
172: }

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

183:   /* scatter x to xdup */
184:   VecScatterBegin(red->scatterin,x,red->xdup,INSERT_VALUES,SCATTER_FORWARD);
185:   VecScatterEnd(red->scatterin,x,red->xdup,INSERT_VALUES,SCATTER_FORWARD);

187:   /* place xdup's local array into xsub */
188:   VecGetArray(red->xdup,&array);
189:   VecPlaceArray(red->xsub,(const PetscScalar*)array);

191:   /* apply preconditioner on each processor */
192:   KSPSolve(red->ksp,red->xsub,red->ysub);
193:   VecResetArray(red->xsub);
194:   VecRestoreArray(red->xdup,&array);

196:   /* place ysub's local array into ydup */
197:   VecGetArray(red->ysub,&array);
198:   VecPlaceArray(red->ydup,(const PetscScalar*)array);

200:   /* scatter ydup to y */
201:   VecScatterBegin(red->scatterout,red->ydup,y,INSERT_VALUES,SCATTER_FORWARD);
202:   VecScatterEnd(red->scatterout,red->ydup,y,INSERT_VALUES,SCATTER_FORWARD);
203:   VecResetArray(red->ydup);
204:   VecRestoreArray(red->ysub,&array);
205:   return(0);
206: }

210: static PetscErrorCode PCReset_Redundant(PC pc)
211: {
212:   PC_Redundant   *red = (PC_Redundant*)pc->data;

216:   VecScatterDestroy(&red->scatterin);
217:   VecScatterDestroy(&red->scatterout);
218:   VecDestroy(&red->ysub);
219:   VecDestroy(&red->xsub);
220:   VecDestroy(&red->xdup);
221:   VecDestroy(&red->ydup);
222:   MatDestroy(&red->pmats);
223:   if (red->ksp) {KSPReset(red->ksp);}
224:   return(0);
225: }

229: static PetscErrorCode PCDestroy_Redundant(PC pc)
230: {
231:   PC_Redundant   *red = (PC_Redundant*)pc->data;

235:   PCReset_Redundant(pc);
236:   KSPDestroy(&red->ksp);
237:   PetscSubcommDestroy(&red->psubcomm);
238:   PetscFree(pc->data);
239:   return(0);
240: }

244: static PetscErrorCode PCSetFromOptions_Redundant(PC pc)
245: {
247:   PC_Redundant   *red = (PC_Redundant*)pc->data;

250:   PetscOptionsHead("Redundant options");
251:   PetscOptionsInt("-pc_redundant_number","Number of redundant pc","PCRedundantSetNumber",red->nsubcomm,&red->nsubcomm,0);
252:   PetscOptionsTail();
253:   return(0);
254: }

258: static PetscErrorCode  PCRedundantSetNumber_Redundant(PC pc,PetscInt nreds)
259: {
260:   PC_Redundant *red = (PC_Redundant*)pc->data;

263:   red->nsubcomm = nreds;
264:   return(0);
265: }

269: /*@
270:    PCRedundantSetNumber - Sets the number of redundant preconditioner contexts.

272:    Logically Collective on PC

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

279:    Level: advanced

281: .keywords: PC, redundant solve
282: @*/
283: PetscErrorCode  PCRedundantSetNumber(PC pc,PetscInt nredundant)
284: {

289:   if (nredundant <= 0) SETERRQ1(PetscObjectComm((PetscObject)pc),PETSC_ERR_ARG_WRONG, "num of redundant pc %D must be positive",nredundant);
290:   PetscTryMethod(pc,"PCRedundantSetNumber_C",(PC,PetscInt),(pc,nredundant));
291:   return(0);
292: }

296: static PetscErrorCode  PCRedundantSetScatter_Redundant(PC pc,VecScatter in,VecScatter out)
297: {
298:   PC_Redundant   *red = (PC_Redundant*)pc->data;

302:   PetscObjectReference((PetscObject)in);
303:   VecScatterDestroy(&red->scatterin);

305:   red->scatterin  = in;

307:   PetscObjectReference((PetscObject)out);
308:   VecScatterDestroy(&red->scatterout);
309:   red->scatterout = out;
310:   return(0);
311: }

315: /*@
316:    PCRedundantSetScatter - Sets the scatter used to copy values into the
317:      redundant local solve and the scatter to move them back into the global
318:      vector.

320:    Logically Collective on PC

322:    Input Parameters:
323: +  pc - the preconditioner context
324: .  in - the scatter to move the values in
325: -  out - the scatter to move them out

327:    Level: advanced

329: .keywords: PC, redundant solve
330: @*/
331: PetscErrorCode  PCRedundantSetScatter(PC pc,VecScatter in,VecScatter out)
332: {

339:   PetscTryMethod(pc,"PCRedundantSetScatter_C",(PC,VecScatter,VecScatter),(pc,in,out));
340:   return(0);
341: }

345: static PetscErrorCode  PCRedundantGetKSP_Redundant(PC pc,KSP *innerksp)
346: {
348:   PC_Redundant   *red = (PC_Redundant*)pc->data;
349:   MPI_Comm       comm,subcomm;
350:   const char     *prefix;

353:   if (!red->psubcomm) {
354:     PetscObjectGetComm((PetscObject)pc,&comm);
355:     PetscSubcommCreate(comm,&red->psubcomm);
356:     PetscSubcommSetNumber(red->psubcomm,red->nsubcomm);
357:     PetscSubcommSetType(red->psubcomm,PETSC_SUBCOMM_INTERLACED);
358:     PetscLogObjectMemory(pc,sizeof(PetscSubcomm));

360:     /* create a new PC that processors in each subcomm have copy of */
361:     subcomm = red->psubcomm->comm;

363:     KSPCreate(subcomm,&red->ksp);
364:     PetscObjectIncrementTabLevel((PetscObject)red->ksp,(PetscObject)pc,1);
365:     PetscLogObjectParent(pc,red->ksp);
366:     KSPSetType(red->ksp,KSPPREONLY);
367:     KSPGetPC(red->ksp,&red->pc);
368:     PCSetType(red->pc,PCLU);

370:     PCGetOptionsPrefix(pc,&prefix);
371:     KSPSetOptionsPrefix(red->ksp,prefix);
372:     KSPAppendOptionsPrefix(red->ksp,"redundant_");
373:   }
374:   *innerksp = red->ksp;
375:   return(0);
376: }

380: /*@
381:    PCRedundantGetKSP - Gets the less parallel KSP created by the redundant PC.

383:    Not Collective

385:    Input Parameter:
386: .  pc - the preconditioner context

388:    Output Parameter:
389: .  innerksp - the KSP on the smaller set of processes

391:    Level: advanced

393: .keywords: PC, redundant solve
394: @*/
395: PetscErrorCode  PCRedundantGetKSP(PC pc,KSP *innerksp)
396: {

402:   PetscTryMethod(pc,"PCRedundantGetKSP_C",(PC,KSP*),(pc,innerksp));
403:   return(0);
404: }

408: static PetscErrorCode  PCRedundantGetOperators_Redundant(PC pc,Mat *mat,Mat *pmat)
409: {
410:   PC_Redundant *red = (PC_Redundant*)pc->data;

413:   if (mat)  *mat  = red->pmats;
414:   if (pmat) *pmat = red->pmats;
415:   return(0);
416: }

420: /*@
421:    PCRedundantGetOperators - gets the sequential matrix and preconditioner matrix

423:    Not Collective

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

428:    Output Parameters:
429: +  mat - the matrix
430: -  pmat - the (possibly different) preconditioner matrix

432:    Level: advanced

434: .keywords: PC, redundant solve
435: @*/
436: PetscErrorCode  PCRedundantGetOperators(PC pc,Mat *mat,Mat *pmat)
437: {

444:   PetscTryMethod(pc,"PCRedundantGetOperators_C",(PC,Mat*,Mat*),(pc,mat,pmat));
445:   return(0);
446: }

448: /* -------------------------------------------------------------------------------------*/
449: /*MC
450:      PCREDUNDANT - Runs a KSP solver with preconditioner for the entire problem on subgroups of processors

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

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

458:    Level: intermediate

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

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

464: .seealso:  PCCreate(), PCSetType(), PCType (for list of available types), PCRedundantSetScatter(),
465:            PCRedundantGetKSP(), PCRedundantGetOperators(), PCRedundantSetNumber()
466: M*/

470: PETSC_EXTERN PetscErrorCode PCCreate_Redundant(PC pc)
471: {
473:   PC_Redundant   *red;
474:   PetscMPIInt    size;

477:   PetscNewLog(pc,PC_Redundant,&red);
478:   MPI_Comm_size(PetscObjectComm((PetscObject)pc),&size);

480:   red->nsubcomm       = size;
481:   red->useparallelmat = PETSC_TRUE;
482:   pc->data            = (void*)red;

484:   pc->ops->apply          = PCApply_Redundant;
485:   pc->ops->applytranspose = 0;
486:   pc->ops->setup          = PCSetUp_Redundant;
487:   pc->ops->destroy        = PCDestroy_Redundant;
488:   pc->ops->reset          = PCReset_Redundant;
489:   pc->ops->setfromoptions = PCSetFromOptions_Redundant;
490:   pc->ops->view           = PCView_Redundant;

492:   PetscObjectComposeFunction((PetscObject)pc,"PCRedundantSetScatter_C",PCRedundantSetScatter_Redundant);
493:   PetscObjectComposeFunction((PetscObject)pc,"PCRedundantSetNumber_C",PCRedundantSetNumber_Redundant);
494:   PetscObjectComposeFunction((PetscObject)pc,"PCRedundantGetKSP_C",PCRedundantGetKSP_Redundant);
495:   PetscObjectComposeFunction((PetscObject)pc,"PCRedundantGetOperators_C",PCRedundantGetOperators_Redundant);
496:   return(0);
497: }