Actual source code: vscatfce.c

petsc-master 2019-12-16
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  1:  #include <petsc/private/vecscatterimpl.h>
  2: #if defined(PETSC_HAVE_CUDA)
  3:  #include <../src/vec/vec/impls/seq/seqcuda/cudavecimpl.h>
  4: #endif
  5: /* ------------------------------------------------------------------*/
  6: /*@
  7:    VecScatterGetMerged - Returns true if the scatter is completed in the VecScatterBegin()
  8:       and the VecScatterEnd() does nothing

 10:    Not Collective

 12:    Input Parameter:
 13: .   ctx - scatter context created with VecScatterCreate()

 15:    Output Parameter:
 16: .   flg - PETSC_TRUE if the VecScatterBegin/End() are all done during the VecScatterBegin()

 18:    Level: developer

 20: .seealso: VecScatterCreate(), VecScatterEnd(), VecScatterBegin()
 21: @*/
 22: PetscErrorCode  VecScatterGetMerged(VecScatter ctx,PetscBool  *flg)
 23: {
 26:   *flg = ctx->beginandendtogether;
 27:   return(0);
 28: }

 30: /*@
 31:    VecScatterBegin - Begins a generalized scatter from one vector to
 32:    another. Complete the scattering phase with VecScatterEnd().

 34:    Neighbor-wise Collective on VecScatter

 36:    Input Parameters:
 37: +  ctx - scatter context generated by VecScatterCreate()
 38: .  x - the vector from which we scatter
 39: .  y - the vector to which we scatter
 40: .  addv - either ADD_VALUES, MAX_VALUES, MIN_VALUES or INSERT_VALUES, with INSERT_VALUES mode any location
 41:           not scattered to retains its old value; i.e. the vector is NOT first zeroed.
 42: -  mode - the scattering mode, usually SCATTER_FORWARD.  The available modes are:
 43:     SCATTER_FORWARD or SCATTER_REVERSE


 46:    Level: intermediate

 48:    Options Database: See VecScatterCreate()

 50:    Notes:
 51:    The vectors x and y need not be the same vectors used in the call
 52:    to VecScatterCreate(), but x must have the same parallel data layout
 53:    as that passed in as the x to VecScatterCreate(), similarly for the y.
 54:    Most likely they have been obtained from VecDuplicate().

 56:    You cannot change the values in the input vector between the calls to VecScatterBegin()
 57:    and VecScatterEnd().

 59:    If you use SCATTER_REVERSE the two arguments x and y should be reversed, from
 60:    the SCATTER_FORWARD.

 62:    y[iy[i]] = x[ix[i]], for i=0,...,ni-1

 64:    This scatter is far more general than the conventional
 65:    scatter, since it can be a gather or a scatter or a combination,
 66:    depending on the indices ix and iy.  If x is a parallel vector and y
 67:    is sequential, VecScatterBegin() can serve to gather values to a
 68:    single processor.  Similarly, if y is parallel and x sequential, the
 69:    routine can scatter from one processor to many processors.


 72: .seealso: VecScatterCreate(), VecScatterEnd()
 73: @*/
 74: PetscErrorCode  VecScatterBegin(VecScatter ctx,Vec x,Vec y,InsertMode addv,ScatterMode mode)
 75: {
 77: #if defined(PETSC_USE_DEBUG)
 78:   PetscInt       to_n,from_n;
 79: #endif
 84:   if (ctx->inuse) SETERRQ(PETSC_COMM_SELF,PETSC_ERR_ARG_WRONGSTATE," Scatter ctx already in use");

 86: #if defined(PETSC_USE_DEBUG)
 87:   /*
 88:      Error checking to make sure these vectors match the vectors used
 89:    to create the vector scatter context. -1 in the from_n and to_n indicate the
 90:    vector lengths are unknown (for example with mapped scatters) and thus
 91:    no error checking is performed.
 92:   */
 93:   if (ctx->from_n >= 0 && ctx->to_n >= 0) {
 94:     VecGetLocalSize(x,&from_n);
 95:     VecGetLocalSize(y,&to_n);
 96:     if (mode & SCATTER_REVERSE) {
 97:       if (to_n != ctx->from_n) SETERRQ2(PETSC_COMM_SELF,PETSC_ERR_ARG_SIZ,"Vector wrong size %D for scatter %D (scatter reverse and vector to != ctx from size)",to_n,ctx->from_n);
 98:       if (from_n != ctx->to_n) SETERRQ2(PETSC_COMM_SELF,PETSC_ERR_ARG_SIZ,"Vector wrong size %D for scatter %D (scatter reverse and vector from != ctx to size)",from_n,ctx->to_n);
 99:     } else {
100:       if (to_n != ctx->to_n)     SETERRQ2(PETSC_COMM_SELF,PETSC_ERR_ARG_SIZ,"Vector wrong size %D for scatter %D (scatter forward and vector to != ctx to size)",to_n,ctx->to_n);
101:       if (from_n != ctx->from_n) SETERRQ2(PETSC_COMM_SELF,PETSC_ERR_ARG_SIZ,"Vector wrong size %D for scatter %D (scatter forward and vector from != ctx from size)",from_n,ctx->from_n);
102:     }
103:   }
104: #endif

106:   ctx->inuse = PETSC_TRUE;
107:   PetscLogEventBegin(VEC_ScatterBegin,ctx,x,y,0);
108:   (*ctx->ops->begin)(ctx,x,y,addv,mode);
109:   if (ctx->beginandendtogether && ctx->ops->end) {
110:     ctx->inuse = PETSC_FALSE;
111:     (*ctx->ops->end)(ctx,x,y,addv,mode);
112:   }
113:   PetscLogEventEnd(VEC_ScatterBegin,ctx,x,y,0);
114:   return(0);
115: }

117: /* --------------------------------------------------------------------*/
118: /*@
119:    VecScatterEnd - Ends a generalized scatter from one vector to another.  Call
120:    after first calling VecScatterBegin().

122:    Neighbor-wise Collective on VecScatter

124:    Input Parameters:
125: +  ctx - scatter context generated by VecScatterCreate()
126: .  x - the vector from which we scatter
127: .  y - the vector to which we scatter
128: .  addv - one of ADD_VALUES, MAX_VALUES, MIN_VALUES or INSERT_VALUES
129: -  mode - the scattering mode, usually SCATTER_FORWARD.  The available modes are:
130:      SCATTER_FORWARD, SCATTER_REVERSE

132:    Level: intermediate

134:    Notes:
135:    If you use SCATTER_REVERSE the arguments x and y should be reversed, from the SCATTER_FORWARD.

137:    y[iy[i]] = x[ix[i]], for i=0,...,ni-1

139: .seealso: VecScatterBegin(), VecScatterCreate()
140: @*/
141: PetscErrorCode  VecScatterEnd(VecScatter ctx,Vec x,Vec y,InsertMode addv,ScatterMode mode)
142: {

149:   ctx->inuse = PETSC_FALSE;
150:   if (!ctx->ops->end) return(0);
151:   if (!ctx->beginandendtogether) {
152:     PetscLogEventBegin(VEC_ScatterEnd,ctx,x,y,0);
153:     (*(ctx)->ops->end)(ctx,x,y,addv,mode);
154:     PetscLogEventEnd(VEC_ScatterEnd,ctx,x,y,0);
155:   }
156:   return(0);
157: }

159: /*@
160:    VecScatterDestroy - Destroys a scatter context created by VecScatterCreate()

162:    Collective on VecScatter

164:    Input Parameter:
165: .  ctx - the scatter context

167:    Level: intermediate

169: .seealso: VecScatterCreate(), VecScatterCopy()
170: @*/
171: PetscErrorCode VecScatterDestroy(VecScatter *ctx)
172: {

176:   if (!*ctx) return(0);
178:   if ((*ctx)->inuse && ((PetscObject)(*ctx))->refct == 1) SETERRQ(((PetscObject)(*ctx))->comm,PETSC_ERR_ARG_WRONGSTATE,"Scatter context is in use");
179:   if (--((PetscObject)(*ctx))->refct > 0) {*ctx = 0; return(0);}

181:   /* if memory was published with SAWs then destroy it */
182:   PetscObjectSAWsViewOff((PetscObject)(*ctx));
183:   if ((*ctx)->ops->destroy) {(*(*ctx)->ops->destroy)(*ctx);}
184: #if defined(PETSC_HAVE_CUDA)
185:   VecScatterCUDAIndicesDestroy((PetscCUDAIndices*)&((*ctx)->spptr));
186: #endif
187:   PetscHeaderDestroy(ctx);
188:   return(0);
189: }

191: /*@
192:    VecScatterSetUp - Sets up the VecScatter to be able to actually scatter information between vectors

194:    Collective on VecScatter

196:    Input Parameter:
197: .  ctx - the scatter context

199:    Level: intermediate

201: .seealso: VecScatterCreate(), VecScatterCopy()
202: @*/
203: PetscErrorCode VecScatterSetUp(VecScatter ctx)
204: {

209:   (*ctx->ops->setup)(ctx);
210:   return(0);
211: }

213: /*@
214:    VecScatterCopy - Makes a copy of a scatter context.

216:    Collective on VecScatter

218:    Input Parameter:
219: .  sctx - the scatter context

221:    Output Parameter:
222: .  ctx - the context copy

224:    Level: advanced

226: .seealso: VecScatterCreate(), VecScatterDestroy()
227: @*/
228: PetscErrorCode  VecScatterCopy(VecScatter sctx,VecScatter *ctx)
229: {
231:   VecScatterType type;

236:   if (!sctx->ops->copy) SETERRQ(PETSC_COMM_SELF,PETSC_ERR_SUP,"Cannot copy this type");
237:   PetscHeaderCreate(*ctx,VEC_SCATTER_CLASSID,"VecScatter","VecScatter","Vec",PetscObjectComm((PetscObject)sctx),VecScatterDestroy,VecScatterView);
238:   (*ctx)->to_n   = sctx->to_n;
239:   (*ctx)->from_n = sctx->from_n;
240:   (*sctx->ops->copy)(sctx,*ctx);

242:   VecScatterGetType(sctx,&type);
243:   PetscObjectChangeTypeName((PetscObject)(*ctx),type);
244:   return(0);
245: }

247: /*@C
248:    VecScatterViewFromOptions - View from Options

250:    Collective on VecScatter

252:    Input Parameters:
253: +  A - the scatter context
254: .  obj - Optional object
255: -  name - command line option

257:    Level: intermediate
258: .seealso:  VecScatter, VecScatterView, PetscObjectViewFromOptions(), VecScatterCreate()
259: @*/
260: PetscErrorCode  VecScatterViewFromOptions(VecScatter A,PetscObject obj,const char name[])
261: {

266:   PetscObjectViewFromOptions((PetscObject)A,obj,name);
267:   return(0);
268: }

270: /* ------------------------------------------------------------------*/
271: /*@C
272:    VecScatterView - Views a vector scatter context.

274:    Collective on VecScatter

276:    Input Parameters:
277: +  ctx - the scatter context
278: -  viewer - the viewer for displaying the context

280:    Level: intermediate

282: @*/
283: PetscErrorCode  VecScatterView(VecScatter ctx,PetscViewer viewer)
284: {

289:   if (!viewer) {
290:     PetscViewerASCIIGetStdout(PetscObjectComm((PetscObject)ctx),&viewer);
291:   }
293:   if (ctx->ops->view) {
294:     (*ctx->ops->view)(ctx,viewer);
295:   }
296:   return(0);
297: }

299: /*@C
300:    VecScatterRemap - Remaps the "from" and "to" indices in a
301:    vector scatter context. FOR EXPERTS ONLY!

303:    Collective on VecScatter

305:    Input Parameters:
306: +  scat    - vector scatter context
307: .  tomap   - remapping plan for "to" indices (may be NULL).
308: -  frommap - remapping plan for "from" indices (may be NULL)

310:    Level: developer

312:    Notes:
313:      In the parallel case the todata contains indices from where the data is taken
314:      (and then sent to others)! The fromdata contains indices from where the received
315:      data is finally put locally.

317:      In the sequential case the todata contains indices from where the data is put
318:      and the fromdata contains indices from where the data is taken from.
319:      This is backwards from the paralllel case!

321: @*/
322: PetscErrorCode  VecScatterRemap(VecScatter scat,PetscInt tomap[],PetscInt frommap[])
323: {
324:   VecScatter_MPI_General *to,*from;
325:   VecScatter_Seq_General *sgto,*sgfrom;
326:   VecScatter_Seq_Stride  *ssto;
327:   PetscInt               i,ierr;


334:   if (scat->ops->remap) {
335:     (*scat->ops->remap)(scat,tomap,frommap);
336:   } else {
337:     to     = (VecScatter_MPI_General*)scat->todata;
338:     from   = (VecScatter_MPI_General*)scat->fromdata;
339:     ssto   = (VecScatter_Seq_Stride*)scat->todata;
340:     sgto   = (VecScatter_Seq_General*)scat->todata;
341:     sgfrom = (VecScatter_Seq_General*)scat->fromdata;

343:     /* remap indices from where we take/read data */
344:     if (tomap) {
345:       if (to->format == VEC_SCATTER_MPI_TOALL) {
346:         SETERRQ(PETSC_COMM_SELF,PETSC_ERR_ARG_SIZ,"Not for to all scatter");
347:       } else if (to->format == VEC_SCATTER_MPI_GENERAL) {
348:         /* handle off processor parts */
349:         for (i=0; i<to->starts[to->n]; i++) to->indices[i] = tomap[to->indices[i]];

351:         /* handle local part */
352:         for (i=0; i<to->local.n; i++) to->local.vslots[i] = tomap[to->local.vslots[i]];

354:         /* the memcpy optimizations in vecscatter was based on index patterns it has.
355:            They need to be recalculated when indices are changed (remapped).
356:          */
357:         VecScatterMemcpyPlanDestroy_PtoP(to,from);
358:         VecScatterMemcpyPlanCreate_PtoP(to,from);
359:       } else if (sgfrom->format == VEC_SCATTER_SEQ_GENERAL) {
360:         /* remap indices*/
361:         for (i=0; i<sgfrom->n; i++) sgfrom->vslots[i] = tomap[sgfrom->vslots[i]];
362:         /* update optimizations, which happen when it is a Stride1toSG, SGtoStride1 or SGToSG vecscatter */
363:         if (ssto->format == VEC_SCATTER_SEQ_STRIDE && ssto->step == 1) {
364:           PetscInt tmp[2];
365:           tmp[0] = 0; tmp[1] = sgfrom->n;
366:           VecScatterMemcpyPlanDestroy(&sgfrom->memcpy_plan);
367:           VecScatterMemcpyPlanCreate_Index(1,tmp,sgfrom->vslots,1/*bs*/,&sgfrom->memcpy_plan);
368:         } else if (sgto->format == VEC_SCATTER_SEQ_GENERAL) {
369:           VecScatterMemcpyPlanDestroy(&sgto->memcpy_plan);
370:           VecScatterMemcpyPlanDestroy(&sgfrom->memcpy_plan);
371:           VecScatterMemcpyPlanCreate_SGToSG(1/*bs*/,sgto,sgfrom);
372:         }
373:       } else if (sgfrom->format == VEC_SCATTER_SEQ_STRIDE) {
374:         VecScatter_Seq_Stride *ssto = (VecScatter_Seq_Stride*)sgfrom;

376:         /* if the remapping is the identity and stride is identity then skip remap */
377:         if (ssto->step == 1 && ssto->first == 0) {
378:           for (i=0; i<ssto->n; i++) {
379:             if (tomap[i] != i) SETERRQ(PETSC_COMM_SELF,PETSC_ERR_ARG_SIZ,"Unable to remap such scatters");
380:           }
381:         } else SETERRQ(PETSC_COMM_SELF,PETSC_ERR_ARG_SIZ,"Unable to remap such scatters");
382:       } else SETERRQ(PETSC_COMM_SELF,PETSC_ERR_ARG_SIZ,"Unable to remap such scatters");
383:     }
384:   }
385:   if (frommap) SETERRQ(PETSC_COMM_SELF,PETSC_ERR_SUP,"Unable to remap the FROM in scatters yet");

387:   /*
388:     Mark then vector lengths as unknown because we do not know the
389:     lengths of the remapped vectors
390:   */
391:   scat->from_n = -1;
392:   scat->to_n   = -1;
393:   return(0);
394: }

396: /* Given a parallel VecScatter context, return number of procs and vector entries involved in remote (i.e., off-process) communication

398:   Input Parameters:
399: + ctx   - the context (must be a parallel vecscatter)
400: - send  - true to select the send info (i.e., todata), otherwise to select the recv info (i.e., fromdata)

402:   Output parameters:
403: + num_procs   - number of remote processors
404: - num_entries - number of vector entries to send or recv


407:   .seealso: VecScatterGetRemote_Private(), VecScatterGetRemoteOrdered_Private()

409:   Notes:
410:   Sometimes PETSc internally needs to use the matrix-vector-multiply vecscatter context for other purposes. The client code
411:   usually only uses MPI_Send/Recv. This group of subroutines provides info needed for such uses.
412:  */
413: PetscErrorCode VecScatterGetRemoteCount_Private(VecScatter ctx,PetscBool send,PetscInt *num_procs,PetscInt *num_entries)
414: {
415:   VecScatter_MPI_General *vs;
416:   PetscBool              par;
417:   PetscErrorCode         ierr;

420:   if (ctx->ops->getremotecount) {
421:     (*ctx->ops->getremotecount)(ctx,send,num_procs,num_entries);
422:   } else {
423:     vs = (VecScatter_MPI_General*)(send ? ctx->todata : ctx->fromdata);
424:     par = (vs->format == VEC_SCATTER_MPI_GENERAL)? PETSC_TRUE : PETSC_FALSE;
425:     if (num_procs)   *num_procs   = par ? vs->n             : 0;
426:     if (num_entries) *num_entries = par ? vs->starts[vs->n] : 0;
427:   }
428:   return(0);
429: }

431: /* Given a parallel VecScatter context, return a plan that represents the remote communication.
432:    Any output parameter can be NULL.

434:   Input Parameters:
435: + ctx   - the context
436: - send  - true to select the send info (i.e., todata), otherwise to select the recv info (i.e., fromdata)

438:   Output parameters:
439: + n        - number of remote processors
440: . starts   - starting point in indices for each proc. ATTENTION: starts[0] is not necessarily zero.
441:              Therefore, expressions like starts[i+1]-starts[i] and indices[starts[i]+j] work as
442:              expected for a CSR structure but buf[starts[i]+j] may be out of range if buf was allocated
443:              with length starts[n]-starts[0]. One should use buf[starts[i]-starts[0]+j] instead.
444: . indices  - indices of entries to send/recv
445: . procs    - ranks of remote processors
446: - bs       - block size

448:   .seealso: VecScatterRestoreRemote_Private(), VecScatterGetRemoteOrdered_Private()
449:  */
450: PetscErrorCode VecScatterGetRemote_Private(VecScatter ctx,PetscBool send,PetscInt *n,const PetscInt **starts,const PetscInt **indices,const PetscMPIInt **procs,PetscInt *bs)
451: {
452:   VecScatter_MPI_General *vs;
453:   PetscBool              par;
454:   PetscErrorCode         ierr;

457:   if (ctx->ops->getremote) {
458:     (*ctx->ops->getremote)(ctx,send,n,starts,indices,procs,bs);
459:   } else {
460:     vs = (VecScatter_MPI_General*)(send ? ctx->todata : ctx->fromdata);
461:     par = (vs->format == VEC_SCATTER_MPI_GENERAL)? PETSC_TRUE : PETSC_FALSE;
462:     if (n)       *n       = par ? vs->n       : 0;
463:     if (indices) *indices = par ? vs->indices : NULL;
464:     if (starts)  *starts  = par ? vs->starts  : NULL;
465:     if (procs)   *procs   = par ? vs->procs   : NULL;
466:     if (bs)      *bs      = par ? vs->bs      : 0;
467:   }
468:   return(0);
469: }


472: /* Given a parallel VecScatter context, return a plan that represents the remote communication. Ranks of remote
473:    processors returned in procs must be sorted in ascending order. Any output parameter can be NULL.

475:   Input Parameters:
476: + ctx   - the context
477: - send  - true to select the send info (i.e., todata), otherwise to select the recv info (i.e., fromdata)

479:   Output parameters:
480: + n        - number of remote processors
481: . starts   - starting point in indices for each proc. ATTENTION: starts[0] is not necessarily zero.
482:              Therefore, expressions like starts[i+1]-starts[i] and indices[starts[i]+j] work as
483:              expected for a CSR structure but buf[starts[i]+j] may be out of range if buf was allocated
484:              with length starts[n]-starts[0]. One should use buf[starts[i]-starts[0]+j] instead.
485: . indices  - indices of entries to send/recv
486: . procs    - ranks of remote processors
487: - bs       - block size

489:   .seealso: VecScatterRestoreRemoteOrdered_Private(), VecScatterGetRemote_Private()

491:   Notes:
492:   Output parameters like starts, indices must also be adapted according to the sorted ranks.
493:  */
494: PetscErrorCode VecScatterGetRemoteOrdered_Private(VecScatter ctx,PetscBool send,PetscInt *n,const PetscInt **starts,const PetscInt **indices,const PetscMPIInt **procs,PetscInt *bs)
495: {
496:   VecScatter_MPI_General *vs;
497:   PetscBool              par;
498:   PetscErrorCode         ierr;

501:   if (ctx->ops->getremoteordered) {
502:     (*ctx->ops->getremoteordered)(ctx,send,n,starts,indices,procs,bs);
503:   } else {
504:     vs = (VecScatter_MPI_General*)(send ? ctx->todata : ctx->fromdata);
505:     par = (vs->format == VEC_SCATTER_MPI_GENERAL)? PETSC_TRUE : PETSC_FALSE;
506:     if (n)       *n       = par ? vs->n       : 0;
507:     if (indices) *indices = par ? vs->indices : NULL;
508:     if (starts)  *starts  = par ? vs->starts  : NULL;
509:     if (procs)   *procs   = par ? vs->procs   : NULL;
510:     if (bs)      *bs      = par ? vs->bs      : 0;
511:   }
512: #if defined(PETSC_USE_DEBUG)
513:   if (n && procs) {
514:     PetscInt i;
515:     /* from back to front to also handle cases *n=0 */
516:     for (i=*n-1; i>0; i--) { if ((*procs)[i-1] > (*procs)[i]) SETERRQ(PETSC_COMM_SELF,PETSC_ERR_PLIB,"procs[] are not ordered"); }
517:   }
518: #endif
519:   return(0);
520: }

522: /* Given a parallel VecScatter context, restore the plan returned by VecScatterGetRemote_Private. This gives a chance for
523:    an implementation to free memory allocated in the VecScatterGetRemote_Private call.

525:   Input Parameters:
526: + ctx   - the context
527: - send  - true to select the send info (i.e., todata), otherwise to select the recv info (i.e., fromdata)

529:   Output parameters:
530: + n        - number of remote processors
531: . starts   - starting point in indices for each proc
532: . indices  - indices of entries to send/recv
533: . procs    - ranks of remote processors
534: - bs       - block size

536:   .seealso: VecScatterGetRemote_Private()
537:  */
538: PetscErrorCode VecScatterRestoreRemote_Private(VecScatter ctx,PetscBool send,PetscInt *n,const PetscInt **starts,const PetscInt **indices,const PetscMPIInt **procs,PetscInt *bs)
539: {
540:   PetscErrorCode         ierr;

543:   if (ctx->ops->restoreremote) {
544:     (*ctx->ops->restoreremote)(ctx,send,n,starts,indices,procs,bs);
545:   } else {
546:     if (starts)  *starts  = NULL;
547:     if (indices) *indices = NULL;
548:     if (procs)   *procs   = NULL;
549:   }
550:   return(0);
551: }

553: /* Given a parallel VecScatter context, restore the plan returned by VecScatterGetRemoteOrdered_Private. This gives a chance for
554:    an implementation to free memory allocated in the VecScatterGetRemoteOrdered_Private call.

556:   Input Parameters:
557: + ctx   - the context
558: - send  - true to select the send info (i.e., todata), otherwise to select the recv info (i.e., fromdata)

560:   Output parameters:
561: + n        - number of remote processors
562: . starts   - starting point in indices for each proc
563: . indices  - indices of entries to send/recv
564: . procs    - ranks of remote processors
565: - bs       - block size

567:   .seealso: VecScatterGetRemoteOrdered_Private()
568:  */
569: PetscErrorCode VecScatterRestoreRemoteOrdered_Private(VecScatter ctx,PetscBool send,PetscInt *n,const PetscInt **starts,const PetscInt **indices,const PetscMPIInt **procs,PetscInt *bs)
570: {
573:   if (ctx->ops->restoreremoteordered) {
574:     (*ctx->ops->restoreremoteordered)(ctx,send,n,starts,indices,procs,bs);
575:   } else {
576:     VecScatterRestoreRemote_Private(ctx,send,n,starts,indices,procs,bs);
577:   }
578:   return(0);
579: }

581: #if defined(PETSC_HAVE_CUDA)

583: /*@C
584:    VecScatterInitializeForGPU - Initializes a generalized scatter from one vector
585:    to another for GPU based computation.

587:    Input Parameters:
588: +  inctx - scatter context generated by VecScatterCreate()
589: -  x - the vector from which we scatter

591:   Level: intermediate

593:   Notes:
594:    Effectively, this function creates all the necessary indexing buffers and work
595:    vectors needed to move only those data points in a vector which need to
596:    be communicated across ranks. This is done at the first time this function is
597:    called. Currently, this only used in the context of the parallel SpMV call in
598:    MatMult_MPIAIJCUSPARSE.

600:    This function is executed before the call to MatMult. This enables the memory
601:    transfers to be overlapped with the MatMult SpMV kernel call.

603: .seealso: VecScatterFinalizeForGPU(), VecScatterCreate(), VecScatterEnd()
604: @*/
605: PETSC_EXTERN PetscErrorCode VecScatterInitializeForGPU(VecScatter inctx,Vec x)
606: {
608:   PetscInt       i,nrecvs,nsends,sbs,rbs,ns,nr;
609:   const PetscInt *sstarts,*rstarts,*sindices,*rindices;

612:   if (use_gpu_aware_mpi) return(0);
613:   VecScatterGetRemote_Private(inctx,PETSC_TRUE/*send*/, &nsends,&sstarts,&sindices,NULL/*procs*/,&sbs);
614:   VecScatterGetRemote_Private(inctx,PETSC_FALSE/*recv*/,&nrecvs,&rstarts,&rindices,NULL/*procs*/,&rbs);
615:   ns   = nsends ? sstarts[nsends]-sstarts[0] : 0; /* s/rstarts[0] is not necessarily zero */
616:   nr   = nrecvs ? rstarts[nrecvs]-rstarts[0] : 0;

618:   if (x->offloadmask != PETSC_OFFLOAD_UNALLOCATED && (nsends>0 || nrecvs>0)) {
619:     if (!inctx->spptr) {
620:       PetscInt k,*tindicesSends,*sindicesSends,*tindicesRecvs,*sindicesRecvs;
621:       /* Here we create indices for both the senders and receivers. */
622:       PetscMalloc1(ns,&tindicesSends);
623:       PetscMalloc1(nr,&tindicesRecvs);

625:       /* s/rindices and s/rstarts could be NULL when ns or nr is zero */
626:       if (ns) {PetscArraycpy(tindicesSends,&sindices[sstarts[0]],ns);}
627:       if (nr) {PetscArraycpy(tindicesRecvs,&rindices[rstarts[0]],nr);}

629:       PetscSortRemoveDupsInt(&ns,tindicesSends);
630:       PetscSortRemoveDupsInt(&nr,tindicesRecvs);

632:       PetscMalloc1(sbs*ns,&sindicesSends);
633:       PetscMalloc1(rbs*nr,&sindicesRecvs);

635:       /* sender indices */
636:       for (i=0; i<ns; i++) {
637:         for (k=0; k<sbs; k++) sindicesSends[i*sbs+k] = tindicesSends[i]+k;
638:       }
639:       PetscFree(tindicesSends);

641:       /* receiver indices */
642:       for (i=0; i<nr; i++) {
643:         for (k=0; k<rbs; k++) sindicesRecvs[i*rbs+k] = tindicesRecvs[i]+k;
644:       }
645:       PetscFree(tindicesRecvs);

647:       /* create GPU indices, work vectors, ... */
648:       VecScatterCUDAIndicesCreate_PtoP(ns*sbs,sindicesSends,nr*rbs,sindicesRecvs,(PetscCUDAIndices*)&inctx->spptr);
649:       PetscFree(sindicesSends);
650:       PetscFree(sindicesRecvs);
651:     }
652:   }
653:   return(0);
654: }

656: /*@C
657:    VecScatterFinalizeForGPU - Finalizes a generalized scatter from one vector to
658:    another for GPU based computation.

660:    Input Parameter:
661: .  inctx - scatter context generated by VecScatterCreate()

663:   Level: intermediate

665:   Notes:
666:    Effectively, this function resets the temporary buffer flags. Currently, this
667:    only used in the context of the parallel SpMV call in in MatMult_MPIAIJCUSPARSE
668:    Once the MatMultAdd is finished, the GPU temporary buffers used for messaging are no longer valid.

670: .seealso: VecScatterInitializeForGPU(), VecScatterCreate(), VecScatterEnd()
671: @*/
672: PETSC_EXTERN PetscErrorCode VecScatterFinalizeForGPU(VecScatter inctx)
673: {
675:   return(0);
676: }

678: #endif