Actual source code: vecstash.c

  1: #define PETSCVEC_DLL

 3:  #include private/vecimpl.h

  5: #define DEFAULT_STASH_SIZE   100

  7: /*
  8:   VecStashCreate_Private - Creates a stash,currently used for all the parallel 
  9:   matrix implementations. The stash is where elements of a matrix destined 
 10:   to be stored on other processors are kept until matrix assembly is done.

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

 14:   Input Parameters:
 15:   comm - communicator, required for scatters.
 16:   bs   - stash block size. used when stashing blocks of values

 18:   Output Parameters:
 19:   stash    - the newly created stash
 20: */
 23: PetscErrorCode VecStashCreate_Private(MPI_Comm comm,PetscInt bs,VecStash *stash)
 24: {
 26:   PetscInt       max,*opt,nopt;
 27:   PetscTruth     flg;

 30:   /* Require 2 tags, get the second using PetscCommGetNewTag() */
 31:   stash->comm = comm;
 32:   PetscCommGetNewTag(stash->comm,&stash->tag1);
 33:   PetscCommGetNewTag(stash->comm,&stash->tag2);
 34:   MPI_Comm_size(stash->comm,&stash->size);
 35:   MPI_Comm_rank(stash->comm,&stash->rank);

 37:   nopt = stash->size;
 38:   PetscMalloc(nopt*sizeof(PetscInt),&opt);
 39:   PetscOptionsGetIntArray(PETSC_NULL,"-vecstash_initial_size",opt,&nopt,&flg);
 40:   if (flg) {
 41:     if (nopt == 1)                max = opt[0];
 42:     else if (nopt == stash->size) max = opt[stash->rank];
 43:     else if (stash->rank < nopt)  max = opt[stash->rank];
 44:     else                          max = 0; /* use default */
 45:     stash->umax = max;
 46:   } else {
 47:     stash->umax = 0;
 48:   }
 49:   PetscFree(opt);

 51:   if (bs <= 0) bs = 1;

 53:   stash->bs       = bs;
 54:   stash->nmax     = 0;
 55:   stash->oldnmax  = 0;
 56:   stash->n        = 0;
 57:   stash->reallocs = -1;
 58:   stash->idx      = 0;
 59:   stash->array    = 0;

 61:   stash->send_waits  = 0;
 62:   stash->recv_waits  = 0;
 63:   stash->send_status = 0;
 64:   stash->nsends      = 0;
 65:   stash->nrecvs      = 0;
 66:   stash->svalues     = 0;
 67:   stash->rvalues     = 0;
 68:   stash->rmax        = 0;
 69:   stash->nprocs      = 0;
 70:   stash->nprocessed  = 0;
 71:   stash->donotstash  = PETSC_FALSE;
 72:   return(0);
 73: }

 75: /* 
 76:    VecStashDestroy_Private - Destroy the stash
 77: */
 80: PetscErrorCode VecStashDestroy_Private(VecStash *stash)
 81: {

 85:   PetscFree(stash->array);
 86:   stash->array = 0;
 87:   PetscFree(stash->bowners);
 88:   return(0);
 89: }

 91: /* 
 92:    VecStashScatterEnd_Private - This is called as the fial stage of
 93:    scatter. The final stages of message passing is done here, and
 94:    all the memory used for message passing is cleanedu up. This
 95:    routine also resets the stash, and deallocates the memory used
 96:    for the stash. It also keeps track of the current memory usage
 97:    so that the same value can be used the next time through.
 98: */
101: PetscErrorCode VecStashScatterEnd_Private(VecStash *stash)
102: {
104:   PetscInt       nsends=stash->nsends,oldnmax;
105:   MPI_Status     *send_status;

108:   /* wait on sends */
109:   if (nsends) {
110:     PetscMalloc(2*nsends*sizeof(MPI_Status),&send_status);
111:     MPI_Waitall(2*nsends,stash->send_waits,send_status);
112:     PetscFree(send_status);
113:   }

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

123:   stash->nmax       = 0;
124:   stash->n          = 0;
125:   stash->reallocs   = -1;
126:   stash->rmax       = 0;
127:   stash->nprocessed = 0;

129:   PetscFree(stash->array);
130:   stash->array = 0;
131:   stash->idx   = 0;
132:   PetscFree(stash->send_waits);
133:   stash->send_waits = 0;
134:   PetscFree(stash->recv_waits);
135:   stash->recv_waits = 0;
136:   PetscFree(stash->svalues);
137:   stash->svalues = 0;
138:   PetscFree(stash->rvalues);
139:   stash->rvalues = 0;
140:   PetscFree(stash->nprocs);
141:   stash->nprocs = 0;
142:   return(0);
143: }

145: /* 
146:    VecStashGetInfo_Private - Gets the relavant statistics of the stash

148:    Input Parameters:
149:    stash    - the stash
150:    nstash   - the size of the stash
151:    reallocs - the number of additional mallocs incurred.
152:    
153: */
156: PetscErrorCode VecStashGetInfo_Private(VecStash *stash,PetscInt *nstash,PetscInt *reallocs)
157: {

160:   if (nstash)  *nstash   = stash->n*stash->bs;
161:   if (reallocs) {
162:     if (stash->reallocs < 0) *reallocs = 0;
163:     else                     *reallocs = stash->reallocs;
164:   }
165:   return(0);
166: }


169: /* 
170:    VecStashSetInitialSize_Private - Sets the initial size of the stash

172:    Input Parameters:
173:    stash  - the stash
174:    max    - the value that is used as the max size of the stash. 
175:             this value is used while allocating memory. It specifies
176:             the number of vals stored, even with the block-stash
177: */
180: PetscErrorCode VecStashSetInitialSize_Private(VecStash *stash,PetscInt max)
181: {
183:   stash->umax = max;
184:   return(0);
185: }

187: /* VecStashExpand_Private - Expand the stash. This function is called
188:    when the space in the stash is not sufficient to add the new values
189:    being inserted into the stash.
190:    
191:    Input Parameters:
192:    stash - the stash
193:    incr  - the minimum increase requested
194:    
195:    Notes: 
196:    This routine doubles the currently used memory. 
197: */
200: PetscErrorCode VecStashExpand_Private(VecStash *stash,PetscInt incr)
201: {
203:   PetscInt       *n_idx,newnmax,bs=stash->bs;
204:   PetscScalar    *n_array;

207:   /* allocate a larger stash. */
208:   if (!stash->oldnmax && !stash->nmax) { /* new stash */
209:     if (stash->umax)                  newnmax = stash->umax/bs;
210:     else                              newnmax = DEFAULT_STASH_SIZE/bs;
211:   } else if (!stash->nmax) { /* resuing stash */
212:     if (stash->umax > stash->oldnmax) newnmax = stash->umax/bs;
213:     else                              newnmax = stash->oldnmax/bs;
214:   } else                              newnmax = stash->nmax*2;

216:   if (newnmax  < (stash->nmax + incr)) newnmax += 2*incr;

218:   PetscMalloc((newnmax)*(sizeof(PetscInt)+bs*sizeof(PetscScalar)),&n_array);
219:   n_idx = (PetscInt*)(n_array + bs*newnmax);
220:   PetscMemcpy(n_array,stash->array,bs*stash->nmax*sizeof(PetscScalar));
221:   PetscMemcpy(n_idx,stash->idx,stash->nmax*sizeof(PetscInt));
222:   PetscFree(stash->array);
223:   stash->array   = n_array;
224:   stash->idx     = n_idx;
225:   stash->nmax    = newnmax;
226:   stash->reallocs++;
227:   return(0);
228: }
229: /*
230:   VecStashScatterBegin_Private - Initiates the transfer of values to the
231:   correct owners. This function goes through the stash, and check the
232:   owners of each stashed value, and sends the values off to the owner
233:   processors.

235:   Input Parameters:
236:   stash  - the stash
237:   owners - an array of size 'no-of-procs' which gives the ownership range
238:            for each node.

240:   Notes: The 'owners' array in the cased of the blocked-stash has the 
241:   ranges specified blocked global indices, and for the regular stash in
242:   the proper global indices.
243: */
246: PetscErrorCode VecStashScatterBegin_Private(VecStash *stash,PetscInt *owners)
247: {
249:   PetscMPIInt    size = stash->size,tag1=stash->tag1,tag2=stash->tag2;
250:   PetscInt       *owner,*start,*nprocs,nsends,nreceives;
251:   PetscInt       nmax,count,*sindices,*rindices,i,j,idx,bs=stash->bs,lastidx;
252:   PetscScalar    *rvalues,*svalues;
253:   MPI_Comm       comm = stash->comm;
254:   MPI_Request    *send_waits,*recv_waits;


258:   /*  first count number of contributors to each processor */
259:   PetscMalloc(2*size*sizeof(PetscInt),&nprocs);
260:   PetscMemzero(nprocs,2*size*sizeof(PetscInt));
261:   PetscMalloc((stash->n+1)*sizeof(PetscInt),&owner);

263:   j       = 0;
264:   lastidx = -1;
265:   for (i=0; i<stash->n; i++) {
266:     /* if indices are NOT locally sorted, need to start search at the beginning */
267:     if (lastidx > (idx = stash->idx[i])) j = 0;
268:     lastidx = idx;
269:     for (; j<size; j++) {
270:       if (idx >= owners[j] && idx < owners[j+1]) {
271:         nprocs[2*j]++; nprocs[2*j+1] = 1; owner[i] = j; break;
272:       }
273:     }
274:   }
275:   nsends = 0;  for (i=0; i<size; i++) { nsends += nprocs[2*i+1];}
276: 
277:   /* inform other processors of number of messages and max length*/
278:   PetscMaxSum(comm,nprocs,&nmax,&nreceives);

280:   /* post receives: 
281:      since we don't know how long each individual message is we 
282:      allocate the largest needed buffer for each receive. Potentially 
283:      this is a lot of wasted space.
284:   */
285:   PetscMalloc((nreceives+1)*(nmax+1)*(bs*sizeof(PetscScalar)+sizeof(PetscInt)),&rvalues);
286:   rindices = (PetscInt*)(rvalues + bs*nreceives*nmax);
287:   PetscMalloc((nreceives+1)*2*sizeof(MPI_Request),&recv_waits);
288:   for (i=0,count=0; i<nreceives; i++) {
289:     MPI_Irecv(rvalues+bs*nmax*i,bs*nmax,MPIU_SCALAR,MPI_ANY_SOURCE,tag1,comm,recv_waits+count++);
290:     MPI_Irecv(rindices+nmax*i,nmax,MPIU_INT,MPI_ANY_SOURCE,tag2,comm,recv_waits+count++);
291:   }

293:   /* do sends:
294:       1) starts[i] gives the starting index in svalues for stuff going to 
295:          the ith processor
296:   */
297:   PetscMalloc((stash->n+1)*(bs*sizeof(PetscScalar)+sizeof(PetscInt)),&svalues);
298:   sindices   = (PetscInt*)(svalues + bs*stash->n);
299:   PetscMalloc(2*(nsends+1)*sizeof(MPI_Request),&send_waits);
300:   PetscMalloc(size*sizeof(PetscInt),&start);
301:   /* use 2 sends the first with all_v, the next with all_i */
302:   start[0] = 0;
303:   for (i=1; i<size; i++) {
304:     start[i] = start[i-1] + nprocs[2*i-2];
305:   }
306:   for (i=0; i<stash->n; i++) {
307:     j = owner[i];
308:     if (bs == 1) {
309:       svalues[start[j]] = stash->array[i];
310:     } else {
311:       PetscMemcpy(svalues+bs*start[j],stash->array+bs*i,bs*sizeof(PetscScalar));
312:     }
313:     sindices[start[j]]  = stash->idx[i];
314:     start[j]++;
315:   }
316:   start[0] = 0;
317:   for (i=1; i<size; i++) { start[i] = start[i-1] + nprocs[2*i-2];}
318:   for (i=0,count=0; i<size; i++) {
319:     if (nprocs[2*i+1]) {
320:       MPI_Isend(svalues+bs*start[i],bs*nprocs[2*i],MPIU_SCALAR,i,tag1,comm,send_waits+count++);
321:       MPI_Isend(sindices+start[i],nprocs[2*i],MPIU_INT,i,tag2,comm,send_waits+count++);
322:     }
323:   }
324:   PetscFree(owner);
325:   PetscFree(start);
326:   /* This memory is reused in scatter end  for a different purpose*/
327:   for (i=0; i<2*size; i++) nprocs[i] = -1;
328:   stash->nprocs      = nprocs;

330:   stash->svalues    = svalues;    stash->rvalues    = rvalues;
331:   stash->nsends     = nsends;     stash->nrecvs     = nreceives;
332:   stash->send_waits = send_waits; stash->recv_waits = recv_waits;
333:   stash->rmax       = nmax;
334:   return(0);
335: }

337: /* 
338:    VecStashScatterGetMesg_Private - This function waits on the receives posted 
339:    in the function VecStashScatterBegin_Private() and returns one message at 
340:    a time to the calling function. If no messages are left, it indicates this
341:    by setting flg = 0, else it sets flg = 1.

343:    Input Parameters:
344:    stash - the stash

346:    Output Parameters:
347:    nvals - the number of entries in the current message.
348:    rows  - an array of row indices (or blocked indices) corresponding to the values
349:    cols  - an array of columnindices (or blocked indices) corresponding to the values
350:    vals  - the values
351:    flg   - 0 indicates no more message left, and the current call has no values associated.
352:            1 indicates that the current call successfully received a message, and the
353:              other output parameters nvals,rows,cols,vals are set appropriately.
354: */
357: PetscErrorCode VecStashScatterGetMesg_Private(VecStash *stash,PetscMPIInt *nvals,PetscInt **rows,PetscScalar **vals,PetscInt *flg)
358: {
360:   PetscMPIInt    i;
361:   PetscInt       *flg_v;
362:   PetscInt       i1,i2,*rindices,bs=stash->bs;
363:   MPI_Status     recv_status;
364:   PetscTruth     match_found = PETSC_FALSE;


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

372:   flg_v = stash->nprocs;
373:   /* If a matching pair of receieves are found, process them, and return the data to
374:      the calling function. Until then keep receiving messages */
375:   while (!match_found) {
376:     MPI_Waitany(2*stash->nrecvs,stash->recv_waits,&i,&recv_status);
377:     /* Now pack the received message into a structure which is useable by others */
378:     if (i % 2) {
379:       MPI_Get_count(&recv_status,MPIU_INT,nvals);
380:       flg_v[2*recv_status.MPI_SOURCE+1] = i/2;
381:     } else {
382:       MPI_Get_count(&recv_status,MPIU_SCALAR,nvals);
383:       flg_v[2*recv_status.MPI_SOURCE] = i/2;
384:       *nvals = *nvals/bs;
385:     }
386: 
387:     /* Check if we have both the messages from this proc */
388:     i1 = flg_v[2*recv_status.MPI_SOURCE];
389:     i2 = flg_v[2*recv_status.MPI_SOURCE+1];
390:     if (i1 != -1 && i2 != -1) {
391:       rindices    = (PetscInt*)(stash->rvalues + bs*stash->rmax*stash->nrecvs);
392:       *rows       = rindices + i2*stash->rmax;
393:       *vals       = stash->rvalues + i1*bs*stash->rmax;
394:       *flg        = 1;
395:       stash->nprocessed ++;
396:       match_found = PETSC_TRUE;
397:     }
398:   }
399:   return(0);
400: }