Actual source code: matstash.c

  1: #define PETSCMAT_DLL

 3:  #include include/private/matimpl.h

  5: /*
  6:        The input to the stash is ALWAYS in MatScalar precision, and the 
  7:     internal storage and output is also in MatScalar.
  8: */
  9: #define DEFAULT_STASH_SIZE   10000

 11: /*
 12:   MatStashCreate_Private - Creates a stash,currently used for all the parallel 
 13:   matrix implementations. The stash is where elements of a matrix destined 
 14:   to be stored on other processors are kept until matrix assembly is done.

 16:   This is a simple minded stash. Simply adds entries to end of stash.

 18:   Input Parameters:
 19:   comm - communicator, required for scatters.
 20:   bs   - stash block size. used when stashing blocks of values

 22:   Output Parameters:
 23:   stash    - the newly created stash
 24: */
 27: PetscErrorCode MatStashCreate_Private(MPI_Comm comm,PetscInt bs,MatStash *stash)
 28: {
 30:   PetscInt       max,*opt,nopt;
 31:   PetscTruth     flg;

 34:   /* Require 2 tags,get the second using PetscCommGetNewTag() */
 35:   stash->comm = comm;
 36:   PetscCommGetNewTag(stash->comm,&stash->tag1);
 37:   PetscCommGetNewTag(stash->comm,&stash->tag2);
 38:   MPI_Comm_size(stash->comm,&stash->size);
 39:   MPI_Comm_rank(stash->comm,&stash->rank);

 41:   nopt = stash->size;
 42:   PetscMalloc(nopt*sizeof(PetscInt),&opt);
 43:   PetscOptionsGetIntArray(PETSC_NULL,"-matstash_initial_size",opt,&nopt,&flg);
 44:   if (flg) {
 45:     if (nopt == 1)                max = opt[0];
 46:     else if (nopt == stash->size) max = opt[stash->rank];
 47:     else if (stash->rank < nopt)  max = opt[stash->rank];
 48:     else                          max = 0; /* Use default */
 49:     stash->umax = max;
 50:   } else {
 51:     stash->umax = 0;
 52:   }
 53:   PetscFree(opt);
 54:   if (bs <= 0) bs = 1;

 56:   stash->bs       = bs;
 57:   stash->nmax     = 0;
 58:   stash->oldnmax  = 0;
 59:   stash->n        = 0;
 60:   stash->reallocs = -1;
 61:   stash->space_head = 0;
 62:   stash->space      = 0;

 64:   stash->send_waits  = 0;
 65:   stash->recv_waits  = 0;
 66:   stash->send_status = 0;
 67:   stash->nsends      = 0;
 68:   stash->nrecvs      = 0;
 69:   stash->svalues     = 0;
 70:   stash->rvalues     = 0;
 71:   stash->rindices    = 0;
 72:   stash->nprocs      = 0;
 73:   stash->nprocessed  = 0;
 74:   return(0);
 75: }

 77: /* 
 78:    MatStashDestroy_Private - Destroy the stash
 79: */
 82: PetscErrorCode MatStashDestroy_Private(MatStash *stash)
 83: {

 87:   if (stash->space_head){
 88:     PetscMatStashSpaceDestroy(stash->space_head);
 89:     stash->space_head = 0;
 90:     stash->space      = 0;
 91:   }
 92:   return(0);
 93: }

 95: /* 
 96:    MatStashScatterEnd_Private - This is called as the fial stage of
 97:    scatter. The final stages of messagepassing is done here, and
 98:    all the memory used for messagepassing is cleanedu up. This
 99:    routine also resets the stash, and deallocates the memory used
100:    for the stash. It also keeps track of the current memory usage
101:    so that the same value can be used the next time through.
102: */
105: PetscErrorCode MatStashScatterEnd_Private(MatStash *stash)
106: {
108:   PetscInt       nsends=stash->nsends,bs2,oldnmax;
109:   MPI_Status     *send_status;

112:   /* wait on sends */
113:   if (nsends) {
114:     PetscMalloc(2*nsends*sizeof(MPI_Status),&send_status);
115:     MPI_Waitall(2*nsends,stash->send_waits,send_status);
116:     PetscFree(send_status);
117:   }

119:   /* Now update nmaxold to be app 10% more than max n used, this way the
120:      wastage of space is reduced the next time this stash is used.
121:      Also update the oldmax, only if it increases */
122:   if (stash->n) {
123:     bs2      = stash->bs*stash->bs;
124:     oldnmax  = ((int)(stash->n * 1.1) + 5)*bs2;
125:     if (oldnmax > stash->oldnmax) stash->oldnmax = oldnmax;
126:   }

128:   stash->nmax       = 0;
129:   stash->n          = 0;
130:   stash->reallocs   = -1;
131:   stash->nprocessed = 0;
132:   if (stash->space_head){
133:     PetscMatStashSpaceDestroy(stash->space_head);
134:     stash->space_head = 0;
135:     stash->space      = 0;
136:   }
137:   PetscFree(stash->send_waits);
138:   stash->send_waits = 0;
139:   PetscFree(stash->recv_waits);
140:   stash->recv_waits = 0;
141:   PetscFree(stash->svalues);
142:   stash->svalues = 0;
143:   PetscFree(stash->rvalues);
144:   stash->rvalues = 0;
145:   PetscFree(stash->rindices);
146:   stash->rindices = 0;
147:   PetscFree(stash->nprocs);
148:   stash->nprocs = 0;
149:   return(0);
150: }

152: /* 
153:    MatStashGetInfo_Private - Gets the relavant statistics of the stash

155:    Input Parameters:
156:    stash    - the stash
157:    nstash   - the size of the stash. Indicates the number of values stored.
158:    reallocs - the number of additional mallocs incurred.
159:    
160: */
163: PetscErrorCode MatStashGetInfo_Private(MatStash *stash,PetscInt *nstash,PetscInt *reallocs)
164: {
165:   PetscInt bs2 = stash->bs*stash->bs;

168:   if (nstash) *nstash   = stash->n*bs2;
169:   if (reallocs) {
170:     if (stash->reallocs < 0) *reallocs = 0;
171:     else                     *reallocs = stash->reallocs;
172:   }
173:   return(0);
174: }

176: /* 
177:    MatStashSetInitialSize_Private - Sets the initial size of the stash

179:    Input Parameters:
180:    stash  - the stash
181:    max    - the value that is used as the max size of the stash. 
182:             this value is used while allocating memory.
183: */
186: PetscErrorCode MatStashSetInitialSize_Private(MatStash *stash,PetscInt max)
187: {
189:   stash->umax = max;
190:   return(0);
191: }

193: /* MatStashExpand_Private - Expand the stash. This function is called
194:    when the space in the stash is not sufficient to add the new values
195:    being inserted into the stash.
196:    
197:    Input Parameters:
198:    stash - the stash
199:    incr  - the minimum increase requested
200:    
201:    Notes: 
202:    This routine doubles the currently used memory. 
203:  */
206: static PetscErrorCode MatStashExpand_Private(MatStash *stash,PetscInt incr)
207: {
209:   PetscInt       newnmax,bs2= stash->bs*stash->bs;

212:   /* allocate a larger stash */
213:   if (!stash->oldnmax && !stash->nmax) { /* new stash */
214:     if (stash->umax)                  newnmax = stash->umax/bs2;
215:     else                              newnmax = DEFAULT_STASH_SIZE/bs2;
216:   } else if (!stash->nmax) { /* resuing stash */
217:     if (stash->umax > stash->oldnmax) newnmax = stash->umax/bs2;
218:     else                              newnmax = stash->oldnmax/bs2;
219:   } else                              newnmax = stash->nmax*2;
220:   if (newnmax  < (stash->nmax + incr)) newnmax += 2*incr;

222:   /* Get a MatStashSpace and attach it to stash */
223:   PetscMatStashSpaceGet(bs2,newnmax,&stash->space);
224:   if (!stash->space_head) { /* new stash or resuing stash->oldnmax */
225:     stash->space_head = stash->space;
226:   }

228:   stash->reallocs++;
229:   stash->nmax = newnmax;
230:   return(0);
231: }
232: /*
233:   MatStashValuesRow_Private - inserts values into the stash. This function
234:   expects the values to be roworiented. Multiple columns belong to the same row
235:   can be inserted with a single call to this function.

237:   Input Parameters:
238:   stash  - the stash
239:   row    - the global row correspoiding to the values
240:   n      - the number of elements inserted. All elements belong to the above row.
241:   idxn   - the global column indices corresponding to each of the values.
242:   values - the values inserted
243: */
246: PetscErrorCode MatStashValuesRow_Private(MatStash *stash,PetscInt row,PetscInt n,const PetscInt idxn[],const MatScalar values[])
247: {
248:   PetscErrorCode     ierr;
249:   PetscInt           i,k;
250:   PetscMatStashSpace space=stash->space;

253:   /* Check and see if we have sufficient memory */
254:   if (!space || space->local_remaining < n){
255:     MatStashExpand_Private(stash,n);
256:   }
257:   space = stash->space;
258:   k     = space->local_used;
259:   for (i=0; i<n; i++) {
260:     space->idx[k] = row;
261:     space->idy[k] = idxn[i];
262:     space->val[k] = values[i];
263:     k++;
264:   }
265:   stash->n               += n;
266:   space->local_used      += n;
267:   space->local_remaining -= n;
268:   return(0);
269: }

271: /*
272:   MatStashValuesCol_Private - inserts values into the stash. This function
273:   expects the values to be columnoriented. Multiple columns belong to the same row
274:   can be inserted with a single call to this function.

276:   Input Parameters:
277:   stash   - the stash
278:   row     - the global row correspoiding to the values
279:   n       - the number of elements inserted. All elements belong to the above row.
280:   idxn    - the global column indices corresponding to each of the values.
281:   values  - the values inserted
282:   stepval - the consecutive values are sepated by a distance of stepval.
283:             this happens because the input is columnoriented.
284: */
287: PetscErrorCode MatStashValuesCol_Private(MatStash *stash,PetscInt row,PetscInt n,const PetscInt idxn[],const MatScalar values[],PetscInt stepval)
288: {
289:   PetscErrorCode     ierr;
290:   PetscInt           i,k;
291:   PetscMatStashSpace space=stash->space;

294:   /* Check and see if we have sufficient memory */
295:   if (!space || space->local_remaining < n){
296:     MatStashExpand_Private(stash,n);
297:   }
298:   space = stash->space;
299:   k = space->local_used;
300:   for (i=0; i<n; i++) {
301:     space->idx[k] = row;
302:     space->idy[k] = idxn[i];
303:     space->val[k] = values[i*stepval];
304:     k++;
305:   }
306:   stash->n               += n;
307:   space->local_used      += n;
308:   space->local_remaining -= n;
309:   return(0);
310: }

312: /*
313:   MatStashValuesRowBlocked_Private - inserts blocks of values into the stash. 
314:   This function expects the values to be roworiented. Multiple columns belong 
315:   to the same block-row can be inserted with a single call to this function.
316:   This function extracts the sub-block of values based on the dimensions of
317:   the original input block, and the row,col values corresponding to the blocks.

319:   Input Parameters:
320:   stash  - the stash
321:   row    - the global block-row correspoiding to the values
322:   n      - the number of elements inserted. All elements belong to the above row.
323:   idxn   - the global block-column indices corresponding to each of the blocks of 
324:            values. Each block is of size bs*bs.
325:   values - the values inserted
326:   rmax   - the number of block-rows in the original block.
327:   cmax   - the number of block-columsn on the original block.
328:   idx    - the index of the current block-row in the original block.
329: */
332: PetscErrorCode MatStashValuesRowBlocked_Private(MatStash *stash,PetscInt row,PetscInt n,const PetscInt idxn[],const MatScalar values[],PetscInt rmax,PetscInt cmax,PetscInt idx)
333: {
334:   PetscErrorCode     ierr;
335:   PetscInt           i,j,k,bs2,bs=stash->bs,l;
336:   const MatScalar    *vals;
337:   MatScalar          *array;
338:   PetscMatStashSpace space=stash->space;

341:   if (!space || space->local_remaining < n){
342:     MatStashExpand_Private(stash,n);
343:   }
344:   space = stash->space;
345:   l     = space->local_used;
346:   bs2   = bs*bs;
347:   for (i=0; i<n; i++) {
348:     space->idx[l] = row;
349:     space->idy[l] = idxn[i];
350:     /* Now copy over the block of values. Store the values column oriented.
351:        This enables inserting multiple blocks belonging to a row with a single
352:        funtion call */
353:     array = space->val + bs2*l;
354:     vals  = values + idx*bs2*n + bs*i;
355:     for (j=0; j<bs; j++) {
356:       for (k=0; k<bs; k++) array[k*bs] = vals[k];
357:       array++;
358:       vals  += cmax*bs;
359:     }
360:     l++;
361:   }
362:   stash->n               += n;
363:   space->local_used      += n;
364:   space->local_remaining -= n;
365:   return(0);
366: }

368: /*
369:   MatStashValuesColBlocked_Private - inserts blocks of values into the stash. 
370:   This function expects the values to be roworiented. Multiple columns belong 
371:   to the same block-row can be inserted with a single call to this function.
372:   This function extracts the sub-block of values based on the dimensions of
373:   the original input block, and the row,col values corresponding to the blocks.

375:   Input Parameters:
376:   stash  - the stash
377:   row    - the global block-row correspoiding to the values
378:   n      - the number of elements inserted. All elements belong to the above row.
379:   idxn   - the global block-column indices corresponding to each of the blocks of 
380:            values. Each block is of size bs*bs.
381:   values - the values inserted
382:   rmax   - the number of block-rows in the original block.
383:   cmax   - the number of block-columsn on the original block.
384:   idx    - the index of the current block-row in the original block.
385: */
388: PetscErrorCode MatStashValuesColBlocked_Private(MatStash *stash,PetscInt row,PetscInt n,const PetscInt idxn[],const MatScalar values[],PetscInt rmax,PetscInt cmax,PetscInt idx)
389: {
390:   PetscErrorCode  ierr;
391:   PetscInt        i,j,k,bs2,bs=stash->bs,l;
392:   const MatScalar *vals;
393:   MatScalar       *array;
394:   PetscMatStashSpace space=stash->space;

397:   if (!space || space->local_remaining < n){
398:     MatStashExpand_Private(stash,n);
399:   }
400:   space = stash->space;
401:   l     = space->local_used;
402:   bs2   = bs*bs;
403:   for (i=0; i<n; i++) {
404:     space->idx[l] = row;
405:     space->idy[l] = idxn[i];
406:     /* Now copy over the block of values. Store the values column oriented.
407:      This enables inserting multiple blocks belonging to a row with a single
408:      funtion call */
409:     array = space->val + bs2*l;
410:     vals  = values + idx*bs2*n + bs*i;
411:     for (j=0; j<bs; j++) {
412:       for (k=0; k<bs; k++) {array[k] = vals[k];}
413:       array += bs;
414:       vals  += rmax*bs;
415:     }
416:     l++;
417:   }
418:   stash->n               += n;
419:   space->local_used      += n;
420:   space->local_remaining -= n;
421:   return(0);
422: }
423: /*
424:   MatStashScatterBegin_Private - Initiates the transfer of values to the
425:   correct owners. This function goes through the stash, and check the
426:   owners of each stashed value, and sends the values off to the owner
427:   processors.

429:   Input Parameters:
430:   stash  - the stash
431:   owners - an array of size 'no-of-procs' which gives the ownership range
432:            for each node.

434:   Notes: The 'owners' array in the cased of the blocked-stash has the 
435:   ranges specified blocked global indices, and for the regular stash in
436:   the proper global indices.
437: */
440: PetscErrorCode MatStashScatterBegin_Private(MatStash *stash,PetscInt *owners)
441: {
442:   PetscInt       *owner,*startv,*starti,tag1=stash->tag1,tag2=stash->tag2,bs2;
443:   PetscInt       size=stash->size,nsends;
445:   PetscInt       count,*sindices,**rindices,i,j,idx,lastidx,l;
446:   MatScalar      **rvalues,*svalues;
447:   MPI_Comm       comm = stash->comm;
448:   MPI_Request    *send_waits,*recv_waits,*recv_waits1,*recv_waits2;
449:   PetscMPIInt    *nprocs,*nlengths,nreceives;
450:   PetscInt       *sp_idx,*sp_idy;
451:   MatScalar      *sp_val;
452:   PetscMatStashSpace space,space_next;

455:   bs2 = stash->bs*stash->bs;
456: 
457:   /*  first count number of contributors to each processor */
458:   PetscMalloc(2*size*sizeof(PetscMPIInt),&nprocs);
459:   PetscMemzero(nprocs,2*size*sizeof(PetscMPIInt));
460:   PetscMalloc((stash->n+1)*sizeof(PetscInt),&owner);

462:   nlengths = nprocs+size;
463:   i = j    = 0;
464:   lastidx  = -1;
465:   space    = stash->space_head;
466:   while (space != PETSC_NULL){
467:     space_next = space->next;
468:     sp_idx     = space->idx;
469:     for (l=0; l<space->local_used; l++){
470:       /* if indices are NOT locally sorted, need to start search at the beginning */
471:       if (lastidx > (idx = sp_idx[l])) j = 0;
472:       lastidx = idx;
473:       for (; j<size; j++) {
474:         if (idx >= owners[j] && idx < owners[j+1]) {
475:           nlengths[j]++; owner[i] = j; break;
476:         }
477:       }
478:       i++;
479:     }
480:     space = space_next;
481:   }
482:   /* Now check what procs get messages - and compute nsends. */
483:   for (i=0, nsends=0 ; i<size; i++) {
484:     if (nlengths[i]) { nprocs[i] = 1; nsends ++;}
485:   }

487:   { int  *onodes,*olengths;
488:   /* Determine the number of messages to expect, their lengths, from from-ids */
489:   PetscGatherNumberOfMessages(comm,nprocs,nlengths,&nreceives);
490:   PetscGatherMessageLengths(comm,nsends,nreceives,nlengths,&onodes,&olengths);
491:   /* since clubbing row,col - lengths are multiplied by 2 */
492:   for (i=0; i<nreceives; i++) olengths[i] *=2;
493:   PetscPostIrecvInt(comm,tag1,nreceives,onodes,olengths,&rindices,&recv_waits1);
494:   /* values are size 'bs2' lengths (and remove earlier factor 2 */
495:   for (i=0; i<nreceives; i++) olengths[i] = olengths[i]*bs2/2;
496:   PetscPostIrecvScalar(comm,tag2,nreceives,onodes,olengths,&rvalues,&recv_waits2);
497:   PetscFree(onodes);
498:   PetscFree(olengths);
499:   }

501:   /* do sends:
502:       1) starts[i] gives the starting index in svalues for stuff going to 
503:          the ith processor
504:   */
505:   PetscMalloc((stash->n+1)*(bs2*sizeof(MatScalar)+2*sizeof(PetscInt)),&svalues);
506:   sindices = (PetscInt*)(svalues + bs2*stash->n);
507:   PetscMalloc(2*(nsends+1)*sizeof(MPI_Request),&send_waits);
508:   PetscMalloc(2*size*sizeof(PetscInt),&startv);
509:   starti   = startv + size;
510:   /* use 2 sends the first with all_a, the next with all_i and all_j */
511:   startv[0]  = 0; starti[0] = 0;
512:   for (i=1; i<size; i++) {
513:     startv[i] = startv[i-1] + nlengths[i-1];
514:     starti[i] = starti[i-1] + nlengths[i-1]*2;
515:   }
516: 
517:   i     = 0;
518:   space = stash->space_head;
519:   while (space != PETSC_NULL){
520:     space_next = space->next;
521:     sp_idx = space->idx;
522:     sp_idy = space->idy;
523:     sp_val = space->val;
524:     for (l=0; l<space->local_used; l++){
525:       j = owner[i];
526:       if (bs2 == 1) {
527:         svalues[startv[j]] = sp_val[l];
528:       } else {
529:         PetscInt  k;
530:         MatScalar *buf1,*buf2;
531:         buf1 = svalues+bs2*startv[j];
532:         buf2 = space->val + bs2*l;
533:         for (k=0; k<bs2; k++){ buf1[k] = buf2[k]; }
534:       }
535:       sindices[starti[j]]             = sp_idx[l];
536:       sindices[starti[j]+nlengths[j]] = sp_idy[l];
537:       startv[j]++;
538:       starti[j]++;
539:       i++;
540:     }
541:     space = space_next;
542:   }
543:   startv[0] = 0;
544:   for (i=1; i<size; i++) { startv[i] = startv[i-1] + nlengths[i-1];}

546:   for (i=0,count=0; i<size; i++) {
547:     if (nprocs[i]) {
548:       MPI_Isend(sindices+2*startv[i],2*nlengths[i],MPIU_INT,i,tag1,comm,send_waits+count++);
549:       MPI_Isend(svalues+bs2*startv[i],bs2*nlengths[i],MPIU_MATSCALAR,i,tag2,comm,send_waits+count++);
550:     }
551:   }
552: #if defined(PETSC_USE_INFO)
553:   PetscInfo1(0,"No of messages: %d \n",nsends);
554:   for (i=0; i<size; i++) {
555:     if (nprocs[i]) {
556:       PetscInfo2(0,"Mesg_to: %d: size: %d \n",i,nlengths[i]*bs2*sizeof(MatScalar)+2*sizeof(PetscInt));
557:     }
558:   }
559: #endif
560:   PetscFree(owner);
561:   PetscFree(startv);
562:   /* This memory is reused in scatter end  for a different purpose*/
563:   for (i=0; i<2*size; i++) nprocs[i] = -1;
564:   stash->nprocs = nprocs;
565: 
566:   /* recv_waits need to be contiguous for MatStashScatterGetMesg_Private() */
567:   PetscMalloc((nreceives+1)*2*sizeof(MPI_Request),&recv_waits);

569:   for (i=0; i<nreceives; i++) {
570:     recv_waits[2*i]   = recv_waits1[i];
571:     recv_waits[2*i+1] = recv_waits2[i];
572:   }
573:   stash->recv_waits = recv_waits;
574:   PetscFree(recv_waits1);
575:   PetscFree(recv_waits2);

577:   stash->svalues    = svalues;    stash->rvalues     = rvalues;
578:   stash->rindices   = rindices;   stash->send_waits  = send_waits;
579:   stash->nsends     = nsends;     stash->nrecvs      = nreceives;
580:   return(0);
581: }

583: /* 
584:    MatStashScatterGetMesg_Private - This function waits on the receives posted 
585:    in the function MatStashScatterBegin_Private() and returns one message at 
586:    a time to the calling function. If no messages are left, it indicates this
587:    by setting flg = 0, else it sets flg = 1.

589:    Input Parameters:
590:    stash - the stash

592:    Output Parameters:
593:    nvals - the number of entries in the current message.
594:    rows  - an array of row indices (or blocked indices) corresponding to the values
595:    cols  - an array of columnindices (or blocked indices) corresponding to the values
596:    vals  - the values
597:    flg   - 0 indicates no more message left, and the current call has no values associated.
598:            1 indicates that the current call successfully received a message, and the
599:              other output parameters nvals,rows,cols,vals are set appropriately.
600: */
603: PetscErrorCode MatStashScatterGetMesg_Private(MatStash *stash,PetscMPIInt *nvals,PetscInt **rows,PetscInt** cols,MatScalar **vals,PetscInt *flg)
604: {
606:   PetscMPIInt    i,*flg_v,i1,i2;
607:   PetscInt       bs2;
608:   MPI_Status     recv_status;
609:   PetscTruth     match_found = PETSC_FALSE;


613:   *flg = 0; /* When a message is discovered this is reset to 1 */
614:   /* Return if no more messages to process */
615:   if (stash->nprocessed == stash->nrecvs) { return(0); }

617:   flg_v = stash->nprocs;
618:   bs2   = stash->bs*stash->bs;
619:   /* If a matching pair of receieves are found, process them, and return the data to
620:      the calling function. Until then keep receiving messages */
621:   while (!match_found) {
622:     MPI_Waitany(2*stash->nrecvs,stash->recv_waits,&i,&recv_status);
623:     /* Now pack the received message into a structure which is useable by others */
624:     if (i % 2) {
625:       MPI_Get_count(&recv_status,MPIU_MATSCALAR,nvals);
626:       flg_v[2*recv_status.MPI_SOURCE] = i/2;
627:       *nvals = *nvals/bs2;
628:     } else {
629:       MPI_Get_count(&recv_status,MPIU_INT,nvals);
630:       flg_v[2*recv_status.MPI_SOURCE+1] = i/2;
631:       *nvals = *nvals/2; /* This message has both row indices and col indices */
632:     }
633: 
634:     /* Check if we have both the messages from this proc */
635:     i1 = flg_v[2*recv_status.MPI_SOURCE];
636:     i2 = flg_v[2*recv_status.MPI_SOURCE+1];
637:     if (i1 != -1 && i2 != -1) {
638:       *rows       = stash->rindices[i2];
639:       *cols       = *rows + *nvals;
640:       *vals       = stash->rvalues[i1];
641:       *flg        = 1;
642:       stash->nprocessed ++;
643:       match_found = PETSC_TRUE;
644:     }
645:   }
646:   return(0);
647: }