Actual source code: mpits.c

  1: #include <petscsys.h>
  2: #include <petsc/private/petscimpl.h>

  4: PetscLogEvent PETSC_BuildTwoSided;
  5: PetscLogEvent PETSC_BuildTwoSidedF;

  7: const char *const PetscBuildTwoSidedTypes[] = {"ALLREDUCE", "IBARRIER", "REDSCATTER", "PetscBuildTwoSidedType", "PETSC_BUILDTWOSIDED_", NULL};

  9: static PetscBuildTwoSidedType _twosided_type = PETSC_BUILDTWOSIDED_NOTSET;

 11: /*@
 12:   PetscCommBuildTwoSidedSetType - set algorithm to use when building two-sided communication

 14:   Logically Collective

 16:   Input Parameters:
 17: + comm     - `PETSC_COMM_WORLD`
 18: - twosided - algorithm to use in subsequent calls to `PetscCommBuildTwoSided()`

 20:   Level: developer

 22:   Note:
 23:   This option is currently global, but could be made per-communicator.

 25: .seealso: `PetscCommBuildTwoSided()`, `PetscCommBuildTwoSidedGetType()`, `PetscBuildTwoSidedType`
 26: @*/
 27: PetscErrorCode PetscCommBuildTwoSidedSetType(MPI_Comm comm, PetscBuildTwoSidedType twosided)
 28: {
 29:   PetscFunctionBegin;
 31:     PetscMPIInt b1[2], b2[2];
 32:     b1[0] = -(PetscMPIInt)twosided;
 33:     b1[1] = (PetscMPIInt)twosided;
 34:     PetscCall(MPIU_Allreduce(b1, b2, 2, MPI_INT, MPI_MAX, comm));
 35:     PetscCheck(-b2[0] == b2[1], comm, PETSC_ERR_ARG_WRONG, "Enum value must be same on all processes");
 36:   }
 37:   _twosided_type = twosided;
 38:   PetscFunctionReturn(PETSC_SUCCESS);
 39: }

 41: /*@
 42:   PetscCommBuildTwoSidedGetType - get algorithm used when building two-sided communication

 44:   Logically Collective

 46:   Output Parameters:
 47: + comm     - communicator on which to query algorithm
 48: - twosided - algorithm to use for `PetscCommBuildTwoSided()`

 50:   Level: developer

 52: .seealso: `PetscCommBuildTwoSided()`, `PetscCommBuildTwoSidedSetType()`, `PetscBuildTwoSidedType`
 53: @*/
 54: PetscErrorCode PetscCommBuildTwoSidedGetType(MPI_Comm comm, PetscBuildTwoSidedType *twosided)
 55: {
 56:   PetscMPIInt size;

 58:   PetscFunctionBegin;
 59:   *twosided = PETSC_BUILDTWOSIDED_NOTSET;
 60:   if (_twosided_type == PETSC_BUILDTWOSIDED_NOTSET) {
 61:     PetscCallMPI(MPI_Comm_size(comm, &size));
 62:     _twosided_type = PETSC_BUILDTWOSIDED_ALLREDUCE; /* default for small comms, see https://gitlab.com/petsc/petsc/-/merge_requests/2611 */
 63: #if defined(PETSC_HAVE_MPI_NONBLOCKING_COLLECTIVES)
 64:     if (size > 1024) _twosided_type = PETSC_BUILDTWOSIDED_IBARRIER;
 65: #endif
 66:     PetscCall(PetscOptionsGetEnum(NULL, NULL, "-build_twosided", PetscBuildTwoSidedTypes, (PetscEnum *)&_twosided_type, NULL));
 67:   }
 68:   *twosided = _twosided_type;
 69:   PetscFunctionReturn(PETSC_SUCCESS);
 70: }

 72: #if defined(PETSC_HAVE_MPI_NONBLOCKING_COLLECTIVES)
 73: static PetscErrorCode PetscCommBuildTwoSided_Ibarrier(MPI_Comm comm, PetscMPIInt count, MPI_Datatype dtype, PetscMPIInt nto, const PetscMPIInt *toranks, const void *todata, PetscMPIInt *nfrom, PetscMPIInt **fromranks, void *fromdata)
 74: {
 75:   PetscMPIInt    nrecvs, tag, done, i;
 76:   MPI_Aint       lb, unitbytes;
 77:   char          *tdata;
 78:   MPI_Request   *sendreqs, barrier;
 79:   PetscSegBuffer segrank, segdata;
 80:   PetscBool      barrier_started;

 82:   PetscFunctionBegin;
 83:   PetscCall(PetscCommDuplicate(comm, &comm, &tag));
 84:   PetscCallMPI(MPI_Type_get_extent(dtype, &lb, &unitbytes));
 85:   PetscCheck(lb == 0, comm, PETSC_ERR_SUP, "Datatype with nonzero lower bound %ld", (long)lb);
 86:   tdata = (char *)todata;
 87:   PetscCall(PetscMalloc1(nto, &sendreqs));
 88:   for (i = 0; i < nto; i++) PetscCallMPI(MPI_Issend((void *)(tdata + count * unitbytes * i), count, dtype, toranks[i], tag, comm, sendreqs + i));
 89:   PetscCall(PetscSegBufferCreate(sizeof(PetscMPIInt), 4, &segrank));
 90:   PetscCall(PetscSegBufferCreate(unitbytes, 4 * count, &segdata));

 92:   nrecvs  = 0;
 93:   barrier = MPI_REQUEST_NULL;
 94:   /* MPICH-3.2 sometimes does not create a request in some "optimized" cases.  This is arguably a standard violation,
 95:    * but we need to work around it. */
 96:   barrier_started = PETSC_FALSE;
 97:   for (done = 0; !done;) {
 98:     PetscMPIInt flag;
 99:     MPI_Status  status;
100:     PetscCallMPI(MPI_Iprobe(MPI_ANY_SOURCE, tag, comm, &flag, &status));
101:     if (flag) { /* incoming message */
102:       PetscMPIInt *recvrank;
103:       void        *buf;
104:       PetscCall(PetscSegBufferGet(segrank, 1, &recvrank));
105:       PetscCall(PetscSegBufferGet(segdata, count, &buf));
106:       *recvrank = status.MPI_SOURCE;
107:       PetscCallMPI(MPI_Recv(buf, count, dtype, status.MPI_SOURCE, tag, comm, MPI_STATUS_IGNORE));
108:       nrecvs++;
109:     }
110:     if (!barrier_started) {
111:       PetscMPIInt sent, nsends;
112:       PetscCall(PetscMPIIntCast(nto, &nsends));
113:       PetscCallMPI(MPI_Testall(nsends, sendreqs, &sent, MPI_STATUSES_IGNORE));
114:       if (sent) {
115:         PetscCallMPI(MPI_Ibarrier(comm, &barrier));
116:         barrier_started = PETSC_TRUE;
117:         PetscCall(PetscFree(sendreqs));
118:       }
119:     } else {
120:       PetscCallMPI(MPI_Test(&barrier, &done, MPI_STATUS_IGNORE));
121:     }
122:   }
123:   *nfrom = nrecvs;
124:   PetscCall(PetscSegBufferExtractAlloc(segrank, fromranks));
125:   PetscCall(PetscSegBufferDestroy(&segrank));
126:   PetscCall(PetscSegBufferExtractAlloc(segdata, fromdata));
127:   PetscCall(PetscSegBufferDestroy(&segdata));
128:   PetscCall(PetscCommDestroy(&comm));
129:   PetscFunctionReturn(PETSC_SUCCESS);
130: }
131: #endif

133: static PetscErrorCode PetscCommBuildTwoSided_Allreduce(MPI_Comm comm, PetscMPIInt count, MPI_Datatype dtype, PetscMPIInt nto, const PetscMPIInt *toranks, const void *todata, PetscMPIInt *nfrom, PetscMPIInt **fromranks, void *fromdata)
134: {
135:   PetscMPIInt       size, rank, *iflags, nrecvs, tag, *franks, i, flg;
136:   MPI_Aint          lb, unitbytes;
137:   char             *tdata, *fdata;
138:   MPI_Request      *reqs, *sendreqs = NULL;
139:   MPI_Status       *statuses;
140:   PetscCommCounter *counter;

142:   PetscFunctionBegin;
143:   PetscCallMPI(MPI_Comm_size(comm, &size));
144:   PetscCallMPI(MPI_Comm_rank(comm, &rank));
145:   PetscCall(PetscCommDuplicate(comm, &comm, &tag));
146:   PetscCallMPI(MPI_Comm_get_attr(comm, Petsc_Counter_keyval, &counter, &flg));
147:   PetscCheck(flg, PETSC_COMM_SELF, PETSC_ERR_PLIB, "Inner PETSc communicator does not have its tag/name counter attribute set");
148:   if (!counter->iflags) {
149:     PetscCall(PetscCalloc1(size, &counter->iflags));
150:     iflags = counter->iflags;
151:   } else {
152:     iflags = counter->iflags;
153:     PetscCall(PetscArrayzero(iflags, size));
154:   }
155:   for (i = 0; i < nto; i++) iflags[toranks[i]] = 1;
156:   PetscCall(MPIU_Allreduce(MPI_IN_PLACE, iflags, size, MPI_INT, MPI_SUM, comm));
157:   nrecvs = iflags[rank];
158:   PetscCallMPI(MPI_Type_get_extent(dtype, &lb, &unitbytes));
159:   PetscCheck(lb == 0, comm, PETSC_ERR_SUP, "Datatype with nonzero lower bound %ld", (long)lb);
160:   PetscCall(PetscMalloc(nrecvs * count * unitbytes, &fdata));
161:   tdata = (char *)todata;
162:   PetscCall(PetscMalloc2(nto + nrecvs, &reqs, nto + nrecvs, &statuses));
163:   if (nto) sendreqs = reqs + nrecvs;
164:   for (i = 0; i < nrecvs; i++) PetscCallMPI(MPI_Irecv((void *)(fdata + count * unitbytes * i), count, dtype, MPI_ANY_SOURCE, tag, comm, reqs + i));
165:   for (i = 0; i < nto; i++) PetscCallMPI(MPI_Isend((void *)(tdata + count * unitbytes * i), count, dtype, toranks[i], tag, comm, sendreqs + i));
166:   PetscCallMPI(MPI_Waitall(nto + nrecvs, reqs, statuses));
167:   PetscCall(PetscMalloc1(nrecvs, &franks));
168:   for (i = 0; i < nrecvs; i++) franks[i] = statuses[i].MPI_SOURCE;
169:   PetscCall(PetscFree2(reqs, statuses));
170:   PetscCall(PetscCommDestroy(&comm));

172:   *nfrom             = nrecvs;
173:   *fromranks         = franks;
174:   *(void **)fromdata = fdata;
175:   PetscFunctionReturn(PETSC_SUCCESS);
176: }

178: #if defined(PETSC_HAVE_MPI_REDUCE_SCATTER_BLOCK)
179: static PetscErrorCode PetscCommBuildTwoSided_RedScatter(MPI_Comm comm, PetscMPIInt count, MPI_Datatype dtype, PetscMPIInt nto, const PetscMPIInt *toranks, const void *todata, PetscMPIInt *nfrom, PetscMPIInt **fromranks, void *fromdata)
180: {
181:   PetscMPIInt       size, *iflags, nrecvs, tag, *franks, i, flg;
182:   MPI_Aint          lb, unitbytes;
183:   char             *tdata, *fdata;
184:   MPI_Request      *reqs, *sendreqs;
185:   MPI_Status       *statuses;
186:   PetscCommCounter *counter;

188:   PetscFunctionBegin;
189:   PetscCallMPI(MPI_Comm_size(comm, &size));
190:   PetscCall(PetscCommDuplicate(comm, &comm, &tag));
191:   PetscCallMPI(MPI_Comm_get_attr(comm, Petsc_Counter_keyval, &counter, &flg));
192:   PetscCheck(flg, PETSC_COMM_SELF, PETSC_ERR_PLIB, "Inner PETSc communicator does not have its tag/name counter attribute set");
193:   if (!counter->iflags) {
194:     PetscCall(PetscCalloc1(size, &counter->iflags));
195:     iflags = counter->iflags;
196:   } else {
197:     iflags = counter->iflags;
198:     PetscCall(PetscArrayzero(iflags, size));
199:   }
200:   for (i = 0; i < nto; i++) iflags[toranks[i]] = 1;
201:   PetscCallMPI(MPI_Reduce_scatter_block(iflags, &nrecvs, 1, MPI_INT, MPI_SUM, comm));
202:   PetscCallMPI(MPI_Type_get_extent(dtype, &lb, &unitbytes));
203:   PetscCheck(lb == 0, comm, PETSC_ERR_SUP, "Datatype with nonzero lower bound %ld", (long)lb);
204:   PetscCall(PetscMalloc(nrecvs * count * unitbytes, &fdata));
205:   tdata = (char *)todata;
206:   PetscCall(PetscMalloc2(nto + nrecvs, &reqs, nto + nrecvs, &statuses));
207:   sendreqs = reqs + nrecvs;
208:   for (i = 0; i < nrecvs; i++) PetscCallMPI(MPI_Irecv((void *)(fdata + count * unitbytes * i), count, dtype, MPI_ANY_SOURCE, tag, comm, reqs + i));
209:   for (i = 0; i < nto; i++) PetscCallMPI(MPI_Isend((void *)(tdata + count * unitbytes * i), count, dtype, toranks[i], tag, comm, sendreqs + i));
210:   PetscCallMPI(MPI_Waitall(nto + nrecvs, reqs, statuses));
211:   PetscCall(PetscMalloc1(nrecvs, &franks));
212:   for (i = 0; i < nrecvs; i++) franks[i] = statuses[i].MPI_SOURCE;
213:   PetscCall(PetscFree2(reqs, statuses));
214:   PetscCall(PetscCommDestroy(&comm));

216:   *nfrom             = nrecvs;
217:   *fromranks         = franks;
218:   *(void **)fromdata = fdata;
219:   PetscFunctionReturn(PETSC_SUCCESS);
220: }
221: #endif

223: /*@C
224:   PetscCommBuildTwoSided - discovers communicating ranks given one-sided information, moving constant-sized data in the process (often message lengths)

226:   Collective

228:   Input Parameters:
229: + comm    - communicator
230: . count   - number of entries to send/receive (must match on all ranks)
231: . dtype   - datatype to send/receive from each rank (must match on all ranks)
232: . nto     - number of ranks to send data to
233: . toranks - ranks to send to (array of length nto)
234: - todata  - data to send to each rank (packed)

236:   Output Parameters:
237: + nfrom     - number of ranks receiving messages from
238: . fromranks - ranks receiving messages from (length `nfrom`, caller should `PetscFree()`)
239: - fromdata  - packed data from each rank, each with count entries of type dtype (length nfrom, caller responsible for `PetscFree()`)

241:   Options Database Key:
242: . -build_twosided <allreduce|ibarrier|redscatter> - algorithm to set up two-sided communication. Default is allreduce for communicators with <= 1024 ranks,
243:                                                     otherwise ibarrier.

245:   Level: developer

247:   Notes:
248:   This memory-scalable interface is an alternative to calling `PetscGatherNumberOfMessages()` and
249:   `PetscGatherMessageLengths()`, possibly with a subsequent round of communication to send other constant-size data, see {cite}`hoeflersiebretlumsdaine10`.

251:   Basic data types as well as contiguous types are supported, but non-contiguous (e.g., strided) types are not.

253: .seealso: `PetscGatherNumberOfMessages()`, `PetscGatherMessageLengths()`, `PetscCommBuildTwoSidedSetType()`, `PetscCommBuildTwoSidedType`
254: @*/
255: PetscErrorCode PetscCommBuildTwoSided(MPI_Comm comm, PetscMPIInt count, MPI_Datatype dtype, PetscMPIInt nto, const PetscMPIInt *toranks, const void *todata, PetscMPIInt *nfrom, PetscMPIInt **fromranks, void *fromdata)
256: {
257:   PetscBuildTwoSidedType buildtype = PETSC_BUILDTWOSIDED_NOTSET;

259:   PetscFunctionBegin;
260:   PetscCall(PetscSysInitializePackage());
261:   PetscCall(PetscLogEventSync(PETSC_BuildTwoSided, comm));
262:   PetscCall(PetscLogEventBegin(PETSC_BuildTwoSided, 0, 0, 0, 0));
263:   PetscCall(PetscCommBuildTwoSidedGetType(comm, &buildtype));
264:   switch (buildtype) {
265:   case PETSC_BUILDTWOSIDED_IBARRIER:
266: #if defined(PETSC_HAVE_MPI_NONBLOCKING_COLLECTIVES)
267:     PetscCall(PetscCommBuildTwoSided_Ibarrier(comm, count, dtype, nto, toranks, todata, nfrom, fromranks, fromdata));
268:     break;
269: #else
270:     SETERRQ(comm, PETSC_ERR_PLIB, "MPI implementation does not provide MPI_Ibarrier (part of MPI-3)");
271: #endif
272:   case PETSC_BUILDTWOSIDED_ALLREDUCE:
273:     PetscCall(PetscCommBuildTwoSided_Allreduce(comm, count, dtype, nto, toranks, todata, nfrom, fromranks, fromdata));
274:     break;
275:   case PETSC_BUILDTWOSIDED_REDSCATTER:
276: #if defined(PETSC_HAVE_MPI_REDUCE_SCATTER_BLOCK)
277:     PetscCall(PetscCommBuildTwoSided_RedScatter(comm, count, dtype, nto, toranks, todata, nfrom, fromranks, fromdata));
278:     break;
279: #else
280:     SETERRQ(comm, PETSC_ERR_PLIB, "MPI implementation does not provide MPI_Reduce_scatter_block (part of MPI-2.2)");
281: #endif
282:   default:
283:     SETERRQ(comm, PETSC_ERR_PLIB, "Unknown method for building two-sided communication");
284:   }
285:   PetscCall(PetscLogEventEnd(PETSC_BuildTwoSided, 0, 0, 0, 0));
286:   PetscFunctionReturn(PETSC_SUCCESS);
287: }

289: static PetscErrorCode PetscCommBuildTwoSidedFReq_Reference(MPI_Comm comm, PetscMPIInt count, MPI_Datatype dtype, PetscMPIInt nto, const PetscMPIInt *toranks, const void *todata, PetscMPIInt *nfrom, PetscMPIInt **fromranks, void *fromdata, PetscMPIInt ntags, MPI_Request **toreqs, MPI_Request **fromreqs, PetscErrorCode (*send)(MPI_Comm, const PetscMPIInt[], PetscMPIInt, PetscMPIInt, void *, MPI_Request[], void *), PetscErrorCode (*recv)(MPI_Comm, const PetscMPIInt[], PetscMPIInt, void *, MPI_Request[], void *), void *ctx)
290: {
291:   PetscMPIInt  i, *tag;
292:   MPI_Aint     lb, unitbytes;
293:   MPI_Request *sendreq, *recvreq;

295:   PetscFunctionBegin;
296:   PetscCall(PetscMalloc1(ntags, &tag));
297:   if (ntags > 0) PetscCall(PetscCommDuplicate(comm, &comm, &tag[0]));
298:   for (i = 1; i < ntags; i++) PetscCall(PetscCommGetNewTag(comm, &tag[i]));

300:   /* Perform complete initial rendezvous */
301:   PetscCall(PetscCommBuildTwoSided(comm, count, dtype, nto, toranks, todata, nfrom, fromranks, fromdata));

303:   PetscCall(PetscMalloc1(nto * ntags, &sendreq));
304:   PetscCall(PetscMalloc1(*nfrom * ntags, &recvreq));

306:   PetscCallMPI(MPI_Type_get_extent(dtype, &lb, &unitbytes));
307:   PetscCheck(lb == 0, comm, PETSC_ERR_SUP, "Datatype with nonzero lower bound %ld", (long)lb);
308:   for (i = 0; i < nto; i++) {
309:     PetscMPIInt k;
310:     for (k = 0; k < ntags; k++) sendreq[i * ntags + k] = MPI_REQUEST_NULL;
311:     PetscCall((*send)(comm, tag, i, toranks[i], ((char *)todata) + count * unitbytes * i, sendreq + i * ntags, ctx));
312:   }
313:   for (i = 0; i < *nfrom; i++) {
314:     void       *header = (*(char **)fromdata) + count * unitbytes * i;
315:     PetscMPIInt k;
316:     for (k = 0; k < ntags; k++) recvreq[i * ntags + k] = MPI_REQUEST_NULL;
317:     PetscCall((*recv)(comm, tag, (*fromranks)[i], header, recvreq + i * ntags, ctx));
318:   }
319:   PetscCall(PetscFree(tag));
320:   PetscCall(PetscCommDestroy(&comm));
321:   *toreqs   = sendreq;
322:   *fromreqs = recvreq;
323:   PetscFunctionReturn(PETSC_SUCCESS);
324: }

326: #if defined(PETSC_HAVE_MPI_NONBLOCKING_COLLECTIVES)

328: static PetscErrorCode PetscCommBuildTwoSidedFReq_Ibarrier(MPI_Comm comm, PetscMPIInt count, MPI_Datatype dtype, PetscMPIInt nto, const PetscMPIInt *toranks, const void *todata, PetscMPIInt *nfrom, PetscMPIInt **fromranks, void *fromdata, PetscMPIInt ntags, MPI_Request **toreqs, MPI_Request **fromreqs, PetscErrorCode (*send)(MPI_Comm, const PetscMPIInt[], PetscMPIInt, PetscMPIInt, void *, MPI_Request[], void *), PetscErrorCode (*recv)(MPI_Comm, const PetscMPIInt[], PetscMPIInt, void *, MPI_Request[], void *), void *ctx)
329: {
330:   PetscMPIInt    nrecvs, tag, *tags, done, i;
331:   MPI_Aint       lb, unitbytes;
332:   char          *tdata;
333:   MPI_Request   *sendreqs, *usendreqs, *req, barrier;
334:   PetscSegBuffer segrank, segdata, segreq;
335:   PetscBool      barrier_started;

337:   PetscFunctionBegin;
338:   PetscCall(PetscCommDuplicate(comm, &comm, &tag));
339:   PetscCall(PetscMalloc1(ntags, &tags));
340:   for (i = 0; i < ntags; i++) PetscCall(PetscCommGetNewTag(comm, &tags[i]));
341:   PetscCallMPI(MPI_Type_get_extent(dtype, &lb, &unitbytes));
342:   PetscCheck(lb == 0, comm, PETSC_ERR_SUP, "Datatype with nonzero lower bound %ld", (long)lb);
343:   tdata = (char *)todata;
344:   PetscCall(PetscMalloc1(nto, &sendreqs));
345:   PetscCall(PetscMalloc1(nto * ntags, &usendreqs));
346:   /* Post synchronous sends */
347:   for (i = 0; i < nto; i++) PetscCallMPI(MPI_Issend((void *)(tdata + count * unitbytes * i), count, dtype, toranks[i], tag, comm, sendreqs + i));
348:   /* Post actual payloads.  These are typically larger messages.  Hopefully sending these later does not slow down the
349:    * synchronous messages above. */
350:   for (i = 0; i < nto; i++) {
351:     PetscMPIInt k;
352:     for (k = 0; k < ntags; k++) usendreqs[i * ntags + k] = MPI_REQUEST_NULL;
353:     PetscCall((*send)(comm, tags, i, toranks[i], tdata + count * unitbytes * i, usendreqs + i * ntags, ctx));
354:   }

356:   PetscCall(PetscSegBufferCreate(sizeof(PetscMPIInt), 4, &segrank));
357:   PetscCall(PetscSegBufferCreate(unitbytes, 4 * count, &segdata));
358:   PetscCall(PetscSegBufferCreate(sizeof(MPI_Request), 4, &segreq));

360:   nrecvs  = 0;
361:   barrier = MPI_REQUEST_NULL;
362:   /* MPICH-3.2 sometimes does not create a request in some "optimized" cases.  This is arguably a standard violation,
363:    * but we need to work around it. */
364:   barrier_started = PETSC_FALSE;
365:   for (done = 0; !done;) {
366:     PetscMPIInt flag;
367:     MPI_Status  status;
368:     PetscCallMPI(MPI_Iprobe(MPI_ANY_SOURCE, tag, comm, &flag, &status));
369:     if (flag) { /* incoming message */
370:       PetscMPIInt *recvrank, k;
371:       void        *buf;
372:       PetscCall(PetscSegBufferGet(segrank, 1, &recvrank));
373:       PetscCall(PetscSegBufferGet(segdata, count, &buf));
374:       *recvrank = status.MPI_SOURCE;
375:       PetscCallMPI(MPI_Recv(buf, count, dtype, status.MPI_SOURCE, tag, comm, MPI_STATUS_IGNORE));
376:       PetscCall(PetscSegBufferGet(segreq, ntags, &req));
377:       for (k = 0; k < ntags; k++) req[k] = MPI_REQUEST_NULL;
378:       PetscCall((*recv)(comm, tags, status.MPI_SOURCE, buf, req, ctx));
379:       nrecvs++;
380:     }
381:     if (!barrier_started) {
382:       PetscMPIInt sent, nsends;
383:       PetscCall(PetscMPIIntCast(nto, &nsends));
384:       PetscCallMPI(MPI_Testall(nsends, sendreqs, &sent, MPI_STATUSES_IGNORE));
385:       if (sent) {
386:         PetscCallMPI(MPI_Ibarrier(comm, &barrier));
387:         barrier_started = PETSC_TRUE;
388:       }
389:     } else {
390:       PetscCallMPI(MPI_Test(&barrier, &done, MPI_STATUS_IGNORE));
391:     }
392:   }
393:   *nfrom = nrecvs;
394:   PetscCall(PetscSegBufferExtractAlloc(segrank, fromranks));
395:   PetscCall(PetscSegBufferDestroy(&segrank));
396:   PetscCall(PetscSegBufferExtractAlloc(segdata, fromdata));
397:   PetscCall(PetscSegBufferDestroy(&segdata));
398:   *toreqs = usendreqs;
399:   PetscCall(PetscSegBufferExtractAlloc(segreq, fromreqs));
400:   PetscCall(PetscSegBufferDestroy(&segreq));
401:   PetscCall(PetscFree(sendreqs));
402:   PetscCall(PetscFree(tags));
403:   PetscCall(PetscCommDestroy(&comm));
404:   PetscFunctionReturn(PETSC_SUCCESS);
405: }
406: #endif

408: /*@C
409:   PetscCommBuildTwoSidedF - discovers communicating ranks given one-sided information, calling user-defined functions during rendezvous

411:   Collective

413:   Input Parameters:
414: + comm    - communicator
415: . count   - number of entries to send/receive in initial rendezvous (must match on all ranks)
416: . dtype   - datatype to send/receive from each rank (must match on all ranks)
417: . nto     - number of ranks to send data to
418: . toranks - ranks to send to (array of length nto)
419: . todata  - data to send to each rank (packed)
420: . ntags   - number of tags needed by send/recv callbacks
421: . send    - callback invoked on sending process when ready to send primary payload
422: . recv    - callback invoked on receiving process after delivery of rendezvous message
423: - ctx     - context for callbacks

425:   Output Parameters:
426: + nfrom     - number of ranks receiving messages from
427: . fromranks - ranks receiving messages from (length nfrom; caller should `PetscFree()`)
428: - fromdata  - packed data from each rank, each with count entries of type dtype (length nfrom, caller responsible for `PetscFree()`)

430:   Level: developer

432:   Notes:
433:   This memory-scalable interface is an alternative to calling `PetscGatherNumberOfMessages()` and
434:   `PetscGatherMessageLengths()`, possibly with a subsequent round of communication to send other data, {cite}`hoeflersiebretlumsdaine10`.

436:   Basic data types as well as contiguous types are supported, but non-contiguous (e.g., strided) types are not.

438: .seealso: `PetscCommBuildTwoSided()`, `PetscCommBuildTwoSidedFReq()`, `PetscGatherNumberOfMessages()`, `PetscGatherMessageLengths()`
439: @*/
440: PetscErrorCode PetscCommBuildTwoSidedF(MPI_Comm comm, PetscMPIInt count, MPI_Datatype dtype, PetscMPIInt nto, const PetscMPIInt *toranks, const void *todata, PetscMPIInt *nfrom, PetscMPIInt **fromranks, void *fromdata, PetscMPIInt ntags, PetscErrorCode (*send)(MPI_Comm, const PetscMPIInt[], PetscMPIInt, PetscMPIInt, void *, MPI_Request[], void *), PetscErrorCode (*recv)(MPI_Comm, const PetscMPIInt[], PetscMPIInt, void *, MPI_Request[], void *), void *ctx)
441: {
442:   MPI_Request *toreqs, *fromreqs;

444:   PetscFunctionBegin;
445:   PetscCall(PetscCommBuildTwoSidedFReq(comm, count, dtype, nto, toranks, todata, nfrom, fromranks, fromdata, ntags, &toreqs, &fromreqs, send, recv, ctx));
446:   PetscCallMPI(MPI_Waitall(nto * ntags, toreqs, MPI_STATUSES_IGNORE));
447:   PetscCallMPI(MPI_Waitall(*nfrom * ntags, fromreqs, MPI_STATUSES_IGNORE));
448:   PetscCall(PetscFree(toreqs));
449:   PetscCall(PetscFree(fromreqs));
450:   PetscFunctionReturn(PETSC_SUCCESS);
451: }

453: /*@C
454:   PetscCommBuildTwoSidedFReq - discovers communicating ranks given one-sided information, calling user-defined functions during rendezvous, returns requests

456:   Collective

458:   Input Parameters:
459: + comm    - communicator
460: . count   - number of entries to send/receive in initial rendezvous (must match on all ranks)
461: . dtype   - datatype to send/receive from each rank (must match on all ranks)
462: . nto     - number of ranks to send data to
463: . toranks - ranks to send to (array of length nto)
464: . todata  - data to send to each rank (packed)
465: . ntags   - number of tags needed by send/recv callbacks
466: . send    - callback invoked on sending process when ready to send primary payload
467: . recv    - callback invoked on receiving process after delivery of rendezvous message
468: - ctx     - context for callbacks

470:   Output Parameters:
471: + nfrom     - number of ranks receiving messages from
472: . fromranks - ranks receiving messages from (length nfrom; caller should `PetscFree()`)
473: . fromdata  - packed data from each rank, each with count entries of type dtype (length nfrom, caller responsible for `PetscFree()`)
474: . toreqs    - array of nto*ntags sender requests (caller must wait on these, then `PetscFree()`)
475: - fromreqs  - array of nfrom*ntags receiver requests (caller must wait on these, then `PetscFree()`)

477:   Level: developer

479:   Notes:
480:   This memory-scalable interface is an alternative to calling `PetscGatherNumberOfMessages()` and
481:   `PetscGatherMessageLengths()`, possibly with a subsequent round of communication to send other data, {cite}`hoeflersiebretlumsdaine10`.

483:   Basic data types as well as contiguous types are supported, but non-contiguous (e.g., strided) types are not.

485: .seealso: `PetscCommBuildTwoSided()`, `PetscCommBuildTwoSidedF()`, `PetscGatherNumberOfMessages()`, `PetscGatherMessageLengths()`
486: @*/
487: PetscErrorCode PetscCommBuildTwoSidedFReq(MPI_Comm comm, PetscMPIInt count, MPI_Datatype dtype, PetscMPIInt nto, const PetscMPIInt *toranks, const void *todata, PetscMPIInt *nfrom, PetscMPIInt **fromranks, void *fromdata, PetscMPIInt ntags, MPI_Request **toreqs, MPI_Request **fromreqs, PetscErrorCode (*send)(MPI_Comm, const PetscMPIInt[], PetscMPIInt, PetscMPIInt, void *, MPI_Request[], void *), PetscErrorCode (*recv)(MPI_Comm, const PetscMPIInt[], PetscMPIInt, void *, MPI_Request[], void *), void *ctx)
488: {
489:   PetscErrorCode (*f)(MPI_Comm, PetscMPIInt, MPI_Datatype, PetscMPIInt, const PetscMPIInt[], const void *, PetscMPIInt *, PetscMPIInt **, void *, PetscMPIInt, MPI_Request **, MPI_Request **, PetscErrorCode (*send)(MPI_Comm, const PetscMPIInt[], PetscMPIInt, PetscMPIInt, void *, MPI_Request[], void *), PetscErrorCode (*recv)(MPI_Comm, const PetscMPIInt[], PetscMPIInt, void *, MPI_Request[], void *), void *ctx);
490:   PetscBuildTwoSidedType buildtype = PETSC_BUILDTWOSIDED_NOTSET;
491:   PetscMPIInt            i, size;

493:   PetscFunctionBegin;
494:   PetscCall(PetscSysInitializePackage());
495:   PetscCallMPI(MPI_Comm_size(comm, &size));
496:   for (i = 0; i < nto; i++) PetscCheck(toranks[i] >= 0 && size > toranks[i], comm, PETSC_ERR_ARG_OUTOFRANGE, "toranks[%d] %d not in comm size %d", i, toranks[i], size);
497:   PetscCall(PetscLogEventSync(PETSC_BuildTwoSidedF, comm));
498:   PetscCall(PetscLogEventBegin(PETSC_BuildTwoSidedF, 0, 0, 0, 0));
499:   PetscCall(PetscCommBuildTwoSidedGetType(comm, &buildtype));
500:   switch (buildtype) {
501:   case PETSC_BUILDTWOSIDED_IBARRIER:
502: #if defined(PETSC_HAVE_MPI_NONBLOCKING_COLLECTIVES)
503:     f = PetscCommBuildTwoSidedFReq_Ibarrier;
504:     break;
505: #else
506:     SETERRQ(comm, PETSC_ERR_PLIB, "MPI implementation does not provide MPI_Ibarrier (part of MPI-3)");
507: #endif
508:   case PETSC_BUILDTWOSIDED_ALLREDUCE:
509:   case PETSC_BUILDTWOSIDED_REDSCATTER:
510:     f = PetscCommBuildTwoSidedFReq_Reference;
511:     break;
512:   default:
513:     SETERRQ(comm, PETSC_ERR_PLIB, "Unknown method for building two-sided communication");
514:   }
515:   PetscCall((*f)(comm, count, dtype, nto, toranks, todata, nfrom, fromranks, fromdata, ntags, toreqs, fromreqs, send, recv, ctx));
516:   PetscCall(PetscLogEventEnd(PETSC_BuildTwoSidedF, 0, 0, 0, 0));
517:   PetscFunctionReturn(PETSC_SUCCESS);
518: }