Actual source code: sfmpi.c

  1: /* Mainly for MPI_Isend in SFBASIC. Once SFNEIGHBOR, SFALLGHATERV etc have a persistent version,
  2:    we can also do abstractions like Prepare/StartCommunication.
  3: */

  5: #include <../src/vec/is/sf/impls/basic/sfpack.h>

  7: /* Start MPI requests. If use non-GPU aware MPI, we might need to copy data from device buf to host buf */
  8: static PetscErrorCode PetscSFLinkStartRequests_MPI(PetscSF sf, PetscSFLink link, PetscSFDirection direction)
  9: {
 10:   PetscMPIInt    nreqs;
 11:   MPI_Request   *reqs = NULL;
 12:   PetscSF_Basic *bas  = (PetscSF_Basic *)sf->data;
 13:   PetscInt       buflen;

 15:   PetscFunctionBegin;
 16:   buflen = (direction == PETSCSF_../../../../../..2LEAF) ? sf->leafbuflen[PETSCSF_REMOTE] : bas->rootbuflen[PETSCSF_REMOTE];
 17:   if (buflen) {
 18:     if (direction == PETSCSF_../../../../../..2LEAF) {
 19:       nreqs = sf->nleafreqs;
 20:       PetscCall(PetscSFLinkGetMPIBuffersAndRequests(sf, link, direction, NULL, NULL, NULL, &reqs));
 21:     } else { /* leaf to root */
 22:       nreqs = bas->nrootreqs;
 23:       PetscCall(PetscSFLinkGetMPIBuffersAndRequests(sf, link, direction, NULL, NULL, &reqs, NULL));
 24:     }
 25:     PetscCallMPI(MPI_Startall_irecv(buflen, link->unit, nreqs, reqs));
 26:   }

 28:   buflen = (direction == PETSCSF_../../../../../..2LEAF) ? bas->rootbuflen[PETSCSF_REMOTE] : sf->leafbuflen[PETSCSF_REMOTE];
 29:   if (buflen) {
 30:     if (direction == PETSCSF_../../../../../..2LEAF) {
 31:       nreqs = bas->nrootreqs;
 32:       PetscCall(PetscSFLinkCopyRootBufferInCaseNotUseGpuAwareMPI(sf, link, PETSC_TRUE /*device2host before sending */));
 33:       PetscCall(PetscSFLinkGetMPIBuffersAndRequests(sf, link, direction, NULL, NULL, &reqs, NULL));
 34:     } else { /* leaf to root */
 35:       nreqs = sf->nleafreqs;
 36:       PetscCall(PetscSFLinkCopyLeafBufferInCaseNotUseGpuAwareMPI(sf, link, PETSC_TRUE));
 37:       PetscCall(PetscSFLinkGetMPIBuffersAndRequests(sf, link, direction, NULL, NULL, NULL, &reqs));
 38:     }
 39:     PetscCall(PetscSFLinkSyncStreamBeforeCallMPI(sf, link, direction));
 40:     PetscCallMPI(MPI_Startall_isend(buflen, link->unit, nreqs, reqs));
 41:   }
 42:   PetscFunctionReturn(PETSC_SUCCESS);
 43: }

 45: static PetscErrorCode PetscSFLinkWaitRequests_MPI(PetscSF sf, PetscSFLink link, PetscSFDirection direction)
 46: {
 47:   PetscSF_Basic     *bas           = (PetscSF_Basic *)sf->data;
 48:   const PetscMemType rootmtype_mpi = link->rootmtype_mpi, leafmtype_mpi = link->leafmtype_mpi;
 49:   const PetscInt     rootdirect_mpi = link->rootdirect_mpi, leafdirect_mpi = link->leafdirect_mpi;

 51:   PetscFunctionBegin;
 52:   PetscCallMPI(MPI_Waitall(bas->nrootreqs, link->rootreqs[direction][rootmtype_mpi][rootdirect_mpi], MPI_STATUSES_IGNORE));
 53:   PetscCallMPI(MPI_Waitall(sf->nleafreqs, link->leafreqs[direction][leafmtype_mpi][leafdirect_mpi], MPI_STATUSES_IGNORE));
 54:   if (direction == PETSCSF_../../../../../..2LEAF) {
 55:     PetscCall(PetscSFLinkCopyLeafBufferInCaseNotUseGpuAwareMPI(sf, link, PETSC_FALSE /* host2device after recving */));
 56:   } else {
 57:     PetscCall(PetscSFLinkCopyRootBufferInCaseNotUseGpuAwareMPI(sf, link, PETSC_FALSE));
 58:   }
 59:   PetscFunctionReturn(PETSC_SUCCESS);
 60: }

 62: /*
 63:    The routine Creates a communication link for the given operation. It first looks up its link cache. If
 64:    there is a free & suitable one, it uses it. Otherwise it creates a new one.

 66:    A link contains buffers and MPI requests for send/recv. It also contains pack/unpack routines to pack/unpack
 67:    root/leafdata to/from these buffers. Buffers are allocated at our discretion. When we find root/leafata
 68:    can be directly passed to MPI, we won't allocate them. Even we allocate buffers, we only allocate
 69:    those that are needed by the given `sfop` and `op`, in other words, we do lazy memory-allocation.

 71:    The routine also allocates buffers on CPU when one does not use gpu-aware MPI but data is on GPU.

 73:    In SFBasic, MPI requests are persistent. They are init'ed until we try to get requests from a link.

 75:    The routine is shared by SFBasic and SFNeighbor based on the fact they all deal with sparse graphs and
 76:    need pack/unpack data.
 77: */
 78: PetscErrorCode PetscSFLinkCreate_MPI(PetscSF sf, MPI_Datatype unit, PetscMemType xrootmtype, const void *rootdata, PetscMemType xleafmtype, const void *leafdata, MPI_Op op, PetscSFOperation sfop, PetscSFLink *mylink)
 79: {
 80:   PetscSF_Basic   *bas = (PetscSF_Basic *)sf->data;
 81:   PetscInt         i, j, k, nrootreqs, nleafreqs, nreqs;
 82:   PetscSFLink     *p, link;
 83:   PetscSFDirection direction;
 84:   MPI_Request     *reqs = NULL;
 85:   PetscBool        match, rootdirect[2], leafdirect[2];
 86:   PetscMemType     rootmtype = PetscMemTypeHost(xrootmtype) ? PETSC_MEMTYPE_HOST : PETSC_MEMTYPE_DEVICE; /* Convert to 0/1 as we will use it in subscript */
 87:   PetscMemType     leafmtype = PetscMemTypeHost(xleafmtype) ? PETSC_MEMTYPE_HOST : PETSC_MEMTYPE_DEVICE;
 88:   PetscMemType     rootmtype_mpi, leafmtype_mpi;   /* mtypes seen by MPI */
 89:   PetscInt         rootdirect_mpi, leafdirect_mpi; /* root/leafdirect seen by MPI*/

 91:   PetscFunctionBegin;

 93:   /* Can we directly use root/leafdirect with the given sf, sfop and op? */
 94:   for (i = PETSCSF_LOCAL; i <= PETSCSF_REMOTE; i++) {
 95:     if (sfop == PETSCSF_BCAST) {
 96:       rootdirect[i] = bas->rootcontig[i];                                                  /* Pack roots */
 97:       leafdirect[i] = (sf->leafcontig[i] && op == MPI_REPLACE) ? PETSC_TRUE : PETSC_FALSE; /* Unpack leaves */
 98:     } else if (sfop == PETSCSF_REDUCE) {
 99:       leafdirect[i] = sf->leafcontig[i];                                                    /* Pack leaves */
100:       rootdirect[i] = (bas->rootcontig[i] && op == MPI_REPLACE) ? PETSC_TRUE : PETSC_FALSE; /* Unpack roots */
101:     } else {                                                                                /* PETSCSF_FETCH */
102:       rootdirect[i] = PETSC_FALSE;                                                          /* FETCH always need a separate rootbuf */
103:       leafdirect[i] = PETSC_FALSE;                                                          /* We also force allocating a separate leafbuf so that leafdata and leafupdate can share mpi requests */
104:     }
105:   }

107:   if (sf->use_gpu_aware_mpi) {
108:     rootmtype_mpi = rootmtype;
109:     leafmtype_mpi = leafmtype;
110:   } else {
111:     rootmtype_mpi = leafmtype_mpi = PETSC_MEMTYPE_HOST;
112:   }
113:   /* Will root/leafdata be directly accessed by MPI?  Without use_gpu_aware_mpi, device data is buffered on host and then passed to MPI */
114:   rootdirect_mpi = rootdirect[PETSCSF_REMOTE] && (rootmtype_mpi == rootmtype) ? 1 : 0;
115:   leafdirect_mpi = leafdirect[PETSCSF_REMOTE] && (leafmtype_mpi == leafmtype) ? 1 : 0;

117:   direction = (sfop == PETSCSF_BCAST) ? PETSCSF_../../../../../..2LEAF : PETSCSF_LEAF2../../../../../..;
118:   nrootreqs = bas->nrootreqs;
119:   nleafreqs = sf->nleafreqs;

121:   /* Look for free links in cache */
122:   for (p = &bas->avail; (link = *p); p = &link->next) {
123:     if (!link->use_nvshmem) { /* Only check with MPI links */
124:       PetscCall(MPIPetsc_Type_compare(unit, link->unit, &match));
125:       if (match) {
126:         /* If root/leafdata will be directly passed to MPI, test if the data used to initialized the MPI requests matches with the current.
127:            If not, free old requests. New requests will be lazily init'ed until one calls PetscSFLinkGetMPIBuffersAndRequests().
128:         */
129:         if (rootdirect_mpi && sf->persistent && link->rootreqsinited[direction][rootmtype][1] && link->rootdatadirect[direction][rootmtype] != rootdata) {
130:           reqs = link->rootreqs[direction][rootmtype][1]; /* Here, rootmtype = rootmtype_mpi */
131:           for (i = 0; i < nrootreqs; i++) {
132:             if (reqs[i] != MPI_REQUEST_NULL) PetscCallMPI(MPI_Request_free(&reqs[i]));
133:           }
134:           link->rootreqsinited[direction][rootmtype][1] = PETSC_FALSE;
135:         }
136:         if (leafdirect_mpi && sf->persistent && link->leafreqsinited[direction][leafmtype][1] && link->leafdatadirect[direction][leafmtype] != leafdata) {
137:           reqs = link->leafreqs[direction][leafmtype][1];
138:           for (i = 0; i < nleafreqs; i++) {
139:             if (reqs[i] != MPI_REQUEST_NULL) PetscCallMPI(MPI_Request_free(&reqs[i]));
140:           }
141:           link->leafreqsinited[direction][leafmtype][1] = PETSC_FALSE;
142:         }
143:         *p = link->next; /* Remove from available list */
144:         goto found;
145:       }
146:     }
147:   }

149:   PetscCall(PetscNew(&link));
150:   PetscCall(PetscSFLinkSetUp_Host(sf, link, unit));
151:   PetscCall(PetscCommGetNewTag(PetscObjectComm((PetscObject)sf), &link->tag)); /* One tag per link */

153:   nreqs = (nrootreqs + nleafreqs) * 8;
154:   PetscCall(PetscMalloc1(nreqs, &link->reqs));
155:   for (i = 0; i < nreqs; i++) link->reqs[i] = MPI_REQUEST_NULL; /* Initialized to NULL so that we know which need to be freed in Destroy */

157:   for (i = 0; i < 2; i++) {     /* Two communication directions */
158:     for (j = 0; j < 2; j++) {   /* Two memory types */
159:       for (k = 0; k < 2; k++) { /* root/leafdirect 0 or 1 */
160:         link->rootreqs[i][j][k] = link->reqs + nrootreqs * (4 * i + 2 * j + k);
161:         link->leafreqs[i][j][k] = link->reqs + nrootreqs * 8 + nleafreqs * (4 * i + 2 * j + k);
162:       }
163:     }
164:   }
165:   link->StartCommunication  = PetscSFLinkStartRequests_MPI;
166:   link->FinishCommunication = PetscSFLinkWaitRequests_MPI;

168: found:

170: #if defined(PETSC_HAVE_DEVICE)
171:   if ((PetscMemTypeDevice(xrootmtype) || PetscMemTypeDevice(xleafmtype)) && !link->deviceinited) {
172:   #if defined(PETSC_HAVE_CUDA)
173:     if (sf->backend == PETSCSF_BACKEND_CUDA) PetscCall(PetscSFLinkSetUp_CUDA(sf, link, unit)); /* Setup streams etc */
174:   #endif
175:   #if defined(PETSC_HAVE_HIP)
176:     if (sf->backend == PETSCSF_BACKEND_HIP) PetscCall(PetscSFLinkSetUp_HIP(sf, link, unit)); /* Setup streams etc */
177:   #endif
178:   #if defined(PETSC_HAVE_KOKKOS)
179:     if (sf->backend == PETSCSF_BACKEND_KOKKOS) PetscCall(PetscSFLinkSetUp_Kokkos(sf, link, unit));
180:   #endif
181:   }
182: #endif

184:   /* Allocate buffers along root/leafdata */
185:   for (i = PETSCSF_LOCAL; i <= PETSCSF_REMOTE; i++) {
186:     /* For local communication, buffers are only needed when roots and leaves have different mtypes */
187:     if (i == PETSCSF_LOCAL && rootmtype == leafmtype) continue;
188:     if (bas->rootbuflen[i]) {
189:       if (rootdirect[i]) { /* Aha, we disguise rootdata as rootbuf */
190:         link->rootbuf[i][rootmtype] = (char *)rootdata + bas->rootstart[i] * link->unitbytes;
191:       } else { /* Have to have a separate rootbuf */
192:         if (!link->rootbuf_alloc[i][rootmtype]) PetscCall(PetscSFMalloc(sf, rootmtype, bas->rootbuflen[i] * link->unitbytes, (void **)&link->rootbuf_alloc[i][rootmtype]));
193:         link->rootbuf[i][rootmtype] = link->rootbuf_alloc[i][rootmtype];
194:       }
195:     }

197:     if (sf->leafbuflen[i]) {
198:       if (leafdirect[i]) {
199:         link->leafbuf[i][leafmtype] = (char *)leafdata + sf->leafstart[i] * link->unitbytes;
200:       } else {
201:         if (!link->leafbuf_alloc[i][leafmtype]) PetscCall(PetscSFMalloc(sf, leafmtype, sf->leafbuflen[i] * link->unitbytes, (void **)&link->leafbuf_alloc[i][leafmtype]));
202:         link->leafbuf[i][leafmtype] = link->leafbuf_alloc[i][leafmtype];
203:       }
204:     }
205:   }

207: #if defined(PETSC_HAVE_DEVICE)
208:   /* Allocate buffers on host for buffering data on device in cast not use_gpu_aware_mpi */
209:   if (PetscMemTypeDevice(rootmtype) && PetscMemTypeHost(rootmtype_mpi)) {
210:     if (!link->rootbuf_alloc[PETSCSF_REMOTE][PETSC_MEMTYPE_HOST]) PetscCall(PetscMalloc(bas->rootbuflen[PETSCSF_REMOTE] * link->unitbytes, &link->rootbuf_alloc[PETSCSF_REMOTE][PETSC_MEMTYPE_HOST]));
211:     link->rootbuf[PETSCSF_REMOTE][PETSC_MEMTYPE_HOST] = link->rootbuf_alloc[PETSCSF_REMOTE][PETSC_MEMTYPE_HOST];
212:   }
213:   if (PetscMemTypeDevice(leafmtype) && PetscMemTypeHost(leafmtype_mpi)) {
214:     if (!link->leafbuf_alloc[PETSCSF_REMOTE][PETSC_MEMTYPE_HOST]) PetscCall(PetscMalloc(sf->leafbuflen[PETSCSF_REMOTE] * link->unitbytes, &link->leafbuf_alloc[PETSCSF_REMOTE][PETSC_MEMTYPE_HOST]));
215:     link->leafbuf[PETSCSF_REMOTE][PETSC_MEMTYPE_HOST] = link->leafbuf_alloc[PETSCSF_REMOTE][PETSC_MEMTYPE_HOST];
216:   }
217: #endif

219:   /* Set `current` state of the link. They may change between different SF invocations with the same link */
220:   if (sf->persistent) { /* If data is directly passed to MPI and inits MPI requests, record the data for comparison on future invocations */
221:     if (rootdirect_mpi) link->rootdatadirect[direction][rootmtype] = rootdata;
222:     if (leafdirect_mpi) link->leafdatadirect[direction][leafmtype] = leafdata;
223:   }

225:   link->rootdata = rootdata; /* root/leafdata are keys to look up links in PetscSFXxxEnd */
226:   link->leafdata = leafdata;
227:   for (i = PETSCSF_LOCAL; i <= PETSCSF_REMOTE; i++) {
228:     link->rootdirect[i] = rootdirect[i];
229:     link->leafdirect[i] = leafdirect[i];
230:   }
231:   link->rootdirect_mpi = rootdirect_mpi;
232:   link->leafdirect_mpi = leafdirect_mpi;
233:   link->rootmtype      = rootmtype;
234:   link->leafmtype      = leafmtype;
235:   link->rootmtype_mpi  = rootmtype_mpi;
236:   link->leafmtype_mpi  = leafmtype_mpi;

238:   link->next = bas->inuse;
239:   bas->inuse = link;
240:   *mylink    = link;
241:   PetscFunctionReturn(PETSC_SUCCESS);
242: }