Actual source code: mpimesg.c

  1: #include <petscsys.h>

  3: PETSC_EXTERN PetscErrorCode PetscGatherNumberOfMessages_Private(MPI_Comm, const PetscMPIInt[], const PetscInt[], PetscMPIInt *);
  4: PETSC_EXTERN PetscErrorCode PetscGatherMessageLengths_Private(MPI_Comm, PetscMPIInt, PetscMPIInt, const PetscInt[], PetscMPIInt **, PetscInt **);

  6: /*@C
  7:   PetscGatherNumberOfMessages -  Computes the number of messages an MPI rank expects to receive during a neighbor communication

  9:   Collective, No Fortran Support

 11:   Input Parameters:
 12: + comm     - Communicator
 13: . iflags   - an array of integers of length sizeof(comm). A '1' in `ilengths`[i] represent a
 14:              message from current node to ith node. Optionally `NULL`
 15: - ilengths - Non zero ilengths[i] represent a message to i of length `ilengths`[i].
 16:              Optionally `NULL`.

 18:   Output Parameter:
 19: . nrecvs - number of messages received

 21:   Level: developer

 23:   Notes:
 24:   With this info, the correct message lengths can be determined using
 25:   `PetscGatherMessageLengths()`

 27:   Either `iflags` or `ilengths` should be provided.  If `iflags` is not
 28:   provided (`NULL`) it can be computed from `ilengths`. If `iflags` is
 29:   provided, `ilengths` is not required.

 31: .seealso: `PetscGatherMessageLengths()`, `PetscGatherMessageLengths2()`, `PetscCommBuildTwoSided()`
 32: @*/
 33: PetscErrorCode PetscGatherNumberOfMessages(MPI_Comm comm, const PetscMPIInt iflags[], const PetscMPIInt ilengths[], PetscMPIInt *nrecvs)
 34: {
 35:   PetscMPIInt size, rank, *recv_buf, i, *iflags_local = NULL, *iflags_localm;

 37:   PetscFunctionBegin;
 38:   PetscCallMPI(MPI_Comm_size(comm, &size));
 39:   PetscCallMPI(MPI_Comm_rank(comm, &rank));

 41:   PetscCall(PetscMalloc2(size, &recv_buf, size, &iflags_localm));

 43:   /* If iflags not provided, compute iflags from ilengths */
 44:   if (!iflags) {
 45:     PetscCheck(ilengths, PETSC_COMM_SELF, PETSC_ERR_ARG_WRONGSTATE, "Either iflags or ilengths should be provided");
 46:     iflags_local = iflags_localm;
 47:     for (i = 0; i < size; i++) {
 48:       if (ilengths[i]) iflags_local[i] = 1;
 49:       else iflags_local[i] = 0;
 50:     }
 51:   } else iflags_local = (PetscMPIInt *)iflags;

 53:   /* Post an allreduce to determine the number of messages the current MPI rank will receive */
 54:   PetscCallMPI(MPIU_Allreduce(iflags_local, recv_buf, size, MPI_INT, MPI_SUM, comm));
 55:   *nrecvs = recv_buf[rank];

 57:   PetscCall(PetscFree2(recv_buf, iflags_localm));
 58:   PetscFunctionReturn(PETSC_SUCCESS);
 59: }

 61: /*@C
 62:   PetscGatherMessageLengths - Computes information about messages that an MPI rank will receive,
 63:   including (from-id,length) pairs for each message.

 65:   Collective, No Fortran Support

 67:   Input Parameters:
 68: + comm     - Communicator
 69: . nsends   - number of messages that are to be sent.
 70: . nrecvs   - number of messages being received
 71: - ilengths - an array of integers of length sizeof(comm)
 72:               a non zero `ilengths`[i] represent a message to i of length `ilengths`[i]

 74:   Output Parameters:
 75: + onodes   - list of ranks from which messages are expected
 76: - olengths - corresponding message lengths

 78:   Level: developer

 80:   Notes:
 81:   With this info, the correct `MPIU_Irecv()` can be posted with the correct
 82:   from-id, with a buffer with the right amount of memory required.

 84:   The calling function deallocates the memory in onodes and olengths

 86:   To determine `nrecvs`, one can use `PetscGatherNumberOfMessages()`

 88: .seealso: `PetscGatherNumberOfMessages()`, `PetscGatherMessageLengths2()`, `PetscCommBuildTwoSided()`
 89: @*/
 90: PetscErrorCode PetscGatherMessageLengths(MPI_Comm comm, PetscMPIInt nsends, PetscMPIInt nrecvs, const PetscMPIInt ilengths[], PetscMPIInt **onodes, PetscMPIInt **olengths)
 91: {
 92:   PetscMPIInt  size, rank, tag, i, j;
 93:   MPI_Request *s_waits, *r_waits;
 94:   MPI_Status  *w_status;

 96:   PetscFunctionBegin;
 97:   PetscCallMPI(MPI_Comm_size(comm, &size));
 98:   PetscCallMPI(MPI_Comm_rank(comm, &rank));
 99:   PetscCall(PetscCommGetNewTag(comm, &tag));

101:   /* cannot use PetscMalloc3() here because in the call to MPI_Waitall() they MUST be contiguous */
102:   PetscCall(PetscMalloc2(nrecvs + nsends, &r_waits, nrecvs + nsends, &w_status));
103:   s_waits = PetscSafePointerPlusOffset(r_waits, nrecvs);

105:   /* Post the Irecv to get the message length-info */
106:   PetscCall(PetscMalloc1(nrecvs, olengths));
107:   for (i = 0; i < nrecvs; i++) PetscCallMPI(MPIU_Irecv((*olengths) + i, 1, MPI_INT, MPI_ANY_SOURCE, tag, comm, r_waits + i));

109:   /* Post the Isends with the message length-info */
110:   for (i = 0, j = 0; i < size; ++i) {
111:     if (ilengths[i]) {
112:       PetscCallMPI(MPIU_Isend((void *)(ilengths + i), 1, MPI_INT, i, tag, comm, s_waits + j));
113:       j++;
114:     }
115:   }

117:   /* Post waits on sends and receives */
118:   if (nrecvs + nsends) PetscCallMPI(MPI_Waitall(nrecvs + nsends, r_waits, w_status));

120:   /* Pack up the received data */
121:   PetscCall(PetscMalloc1(nrecvs, onodes));
122:   for (i = 0; i < nrecvs; ++i) {
123:     (*onodes)[i] = w_status[i].MPI_SOURCE;
124: #if defined(PETSC_HAVE_OPENMPI)
125:     /* This line is a workaround for a bug in Open MPI 2.1.1 distributed by Ubuntu-18.04.2 LTS.
126:        It happens in self-to-self MPI_Send/Recv using MPI_ANY_SOURCE for message matching. Open MPI
127:        does not put correct value in recv buffer. See also
128:        https://lists.mcs.anl.gov/pipermail/petsc-dev/2019-July/024803.html
129:        https://www.mail-archive.com/users@lists.open-mpi.org//msg33383.html
130:      */
131:     if (w_status[i].MPI_SOURCE == rank) (*olengths)[i] = ilengths[rank];
132: #endif
133:   }
134:   PetscCall(PetscFree2(r_waits, w_status));
135:   PetscFunctionReturn(PETSC_SUCCESS);
136: }

138: /* Same as PetscGatherNumberOfMessages(), except using PetscInt for ilengths[] */
139: PetscErrorCode PetscGatherNumberOfMessages_Private(MPI_Comm comm, const PetscMPIInt iflags[], const PetscInt ilengths[], PetscMPIInt *nrecvs)
140: {
141:   PetscMPIInt size, rank, *recv_buf, i, *iflags_local = NULL, *iflags_localm;

143:   PetscFunctionBegin;
144:   PetscCallMPI(MPI_Comm_size(comm, &size));
145:   PetscCallMPI(MPI_Comm_rank(comm, &rank));

147:   PetscCall(PetscMalloc2(size, &recv_buf, size, &iflags_localm));

149:   /* If iflags not provided, compute iflags from ilengths */
150:   if (!iflags) {
151:     PetscCheck(ilengths, PETSC_COMM_SELF, PETSC_ERR_ARG_WRONGSTATE, "Either iflags or ilengths should be provided");
152:     iflags_local = iflags_localm;
153:     for (i = 0; i < size; i++) {
154:       if (ilengths[i]) iflags_local[i] = 1;
155:       else iflags_local[i] = 0;
156:     }
157:   } else iflags_local = (PetscMPIInt *)iflags;

159:   /* Post an allreduce to determine the number of messages the current MPI rank will receive */
160:   PetscCallMPI(MPIU_Allreduce(iflags_local, recv_buf, size, MPI_INT, MPI_SUM, comm));
161:   *nrecvs = recv_buf[rank];

163:   PetscCall(PetscFree2(recv_buf, iflags_localm));
164:   PetscFunctionReturn(PETSC_SUCCESS);
165: }

167: /* Same as PetscGatherMessageLengths(), except using PetscInt for message lengths */
168: PetscErrorCode PetscGatherMessageLengths_Private(MPI_Comm comm, PetscMPIInt nsends, PetscMPIInt nrecvs, const PetscInt ilengths[], PetscMPIInt **onodes, PetscInt **olengths)
169: {
170:   PetscMPIInt  size, rank, tag, i, j;
171:   MPI_Request *s_waits, *r_waits;
172:   MPI_Status  *w_status;

174:   PetscFunctionBegin;
175:   PetscCallMPI(MPI_Comm_size(comm, &size));
176:   PetscCallMPI(MPI_Comm_rank(comm, &rank));
177:   PetscCall(PetscCommGetNewTag(comm, &tag));

179:   /* cannot use PetscMalloc3() here because in the call to MPI_Waitall() they MUST be contiguous */
180:   PetscCall(PetscMalloc2(nrecvs + nsends, &r_waits, nrecvs + nsends, &w_status));
181:   s_waits = PetscSafePointerPlusOffset(r_waits, nrecvs);

183:   /* Post the Irecv to get the message length-info */
184:   PetscCall(PetscMalloc1(nrecvs, olengths));
185:   for (i = 0; i < nrecvs; i++) PetscCallMPI(MPIU_Irecv((*olengths) + i, 1, MPIU_INT, MPI_ANY_SOURCE, tag, comm, r_waits + i));

187:   /* Post the Isends with the message length-info */
188:   for (i = 0, j = 0; i < size; ++i) {
189:     if (ilengths[i]) {
190:       PetscCallMPI(MPIU_Isend((void *)(ilengths + i), 1, MPIU_INT, i, tag, comm, s_waits + j));
191:       j++;
192:     }
193:   }

195:   /* Post waits on sends and receives */
196:   if (nrecvs + nsends) PetscCallMPI(MPI_Waitall(nrecvs + nsends, r_waits, w_status));

198:   /* Pack up the received data */
199:   PetscCall(PetscMalloc1(nrecvs, onodes));
200:   for (i = 0; i < nrecvs; ++i) {
201:     (*onodes)[i] = w_status[i].MPI_SOURCE;
202:     if (w_status[i].MPI_SOURCE == rank) (*olengths)[i] = ilengths[rank]; /* See comments in PetscGatherMessageLengths */
203:   }
204:   PetscCall(PetscFree2(r_waits, w_status));
205:   PetscFunctionReturn(PETSC_SUCCESS);
206: }

208: /*@C
209:   PetscGatherMessageLengths2 - Computes info about messages that a MPI rank will receive,
210:   including (from-id,length) pairs for each message. Same functionality as `PetscGatherMessageLengths()`
211:   except it takes TWO ilenths and output TWO olengths.

213:   Collective, No Fortran Support

215:   Input Parameters:
216: + comm      - Communicator
217: . nsends    - number of messages that are to be sent.
218: . nrecvs    - number of messages being received
219: . ilengths1 - first array of integers of length sizeof(comm)
220: - ilengths2 - second array of integers of length sizeof(comm)

222:   Output Parameters:
223: + onodes    - list of ranks from which messages are expected
224: . olengths1 - first corresponding message lengths
225: - olengths2 - second  message lengths

227:   Level: developer

229:   Notes:
230:   With this info, the correct `MPIU_Irecv()` can be posted with the correct
231:   from-id, with a buffer with the right amount of memory required.

233:   The calling function should `PetscFree()` the memory in `onodes` and `olengths`

235:   To determine `nrecvs`, one can use `PetscGatherNumberOfMessages()`

237: .seealso: `PetscGatherMessageLengths()`, `PetscGatherNumberOfMessages()`, `PetscCommBuildTwoSided()`
238: @*/
239: PetscErrorCode PetscGatherMessageLengths2(MPI_Comm comm, PetscMPIInt nsends, PetscMPIInt nrecvs, const PetscMPIInt ilengths1[], const PetscMPIInt ilengths2[], PetscMPIInt **onodes, PetscMPIInt **olengths1, PetscMPIInt **olengths2)
240: {
241:   PetscMPIInt  size, tag, i, j, *buf_s, *buf_r, *buf_j = NULL;
242:   MPI_Request *s_waits, *r_waits;
243:   MPI_Status  *w_status;

245:   PetscFunctionBegin;
246:   PetscCallMPI(MPI_Comm_size(comm, &size));
247:   PetscCall(PetscCommGetNewTag(comm, &tag));

249:   /* cannot use PetscMalloc5() because r_waits and s_waits must be contiguous for the call to MPI_Waitall() */
250:   PetscCall(PetscMalloc4(nrecvs + nsends, &r_waits, 2 * nrecvs, &buf_r, 2 * nsends, &buf_s, nrecvs + nsends, &w_status));
251:   s_waits = PetscSafePointerPlusOffset(r_waits, nrecvs);

253:   /* Post the Irecv to get the message length-info */
254:   PetscCall(PetscMalloc1(nrecvs + 1, olengths1));
255:   PetscCall(PetscMalloc1(nrecvs + 1, olengths2));
256:   for (i = 0; i < nrecvs; i++) {
257:     buf_j = buf_r + (2 * i);
258:     PetscCallMPI(MPIU_Irecv(buf_j, 2, MPI_INT, MPI_ANY_SOURCE, tag, comm, r_waits + i));
259:   }

261:   /* Post the Isends with the message length-info */
262:   for (i = 0, j = 0; i < size; ++i) {
263:     if (ilengths1[i]) {
264:       buf_j    = buf_s + (2 * j);
265:       buf_j[0] = *(ilengths1 + i);
266:       buf_j[1] = *(ilengths2 + i);
267:       PetscCallMPI(MPIU_Isend(buf_j, 2, MPI_INT, i, tag, comm, s_waits + j));
268:       j++;
269:     }
270:   }
271:   PetscCheck(j == nsends, PETSC_COMM_SELF, PETSC_ERR_PLIB, "j %d not equal to expected number of sends %d", j, nsends);

273:   /* Post waits on sends and receives */
274:   if (nrecvs + nsends) PetscCallMPI(MPI_Waitall(nrecvs + nsends, r_waits, w_status));

276:   /* Pack up the received data */
277:   PetscCall(PetscMalloc1(nrecvs + 1, onodes));
278:   for (i = 0; i < nrecvs; ++i) {
279:     (*onodes)[i]    = w_status[i].MPI_SOURCE;
280:     buf_j           = buf_r + (2 * i);
281:     (*olengths1)[i] = buf_j[0];
282:     (*olengths2)[i] = buf_j[1];
283:   }

285:   PetscCall(PetscFree4(r_waits, buf_r, buf_s, w_status));
286:   PetscFunctionReturn(PETSC_SUCCESS);
287: }

289: /*
290:   Allocate a buffer sufficient to hold messages of size specified in olengths.
291:   And post Irecvs on these buffers using node info from onodes
292:  */
293: PetscErrorCode PetscPostIrecvInt(MPI_Comm comm, PetscMPIInt tag, PetscMPIInt nrecvs, const PetscMPIInt onodes[], const PetscMPIInt olengths[], PetscInt ***rbuf, MPI_Request **r_waits)
294: {
295:   PetscInt   **rbuf_t, i, len = 0;
296:   MPI_Request *r_waits_t;

298:   PetscFunctionBegin;
299:   /* compute memory required for recv buffers */
300:   for (i = 0; i < nrecvs; i++) len += olengths[i]; /* each message length */

302:   /* allocate memory for recv buffers */
303:   PetscCall(PetscMalloc1(nrecvs + 1, &rbuf_t));
304:   PetscCall(PetscMalloc1(len, &rbuf_t[0]));
305:   for (i = 1; i < nrecvs; ++i) rbuf_t[i] = rbuf_t[i - 1] + olengths[i - 1];

307:   /* Post the receives */
308:   PetscCall(PetscMalloc1(nrecvs, &r_waits_t));
309:   for (i = 0; i < nrecvs; ++i) PetscCallMPI(MPIU_Irecv(rbuf_t[i], olengths[i], MPIU_INT, onodes[i], tag, comm, r_waits_t + i));

311:   *rbuf    = rbuf_t;
312:   *r_waits = r_waits_t;
313:   PetscFunctionReturn(PETSC_SUCCESS);
314: }

316: PetscErrorCode PetscPostIrecvScalar(MPI_Comm comm, PetscMPIInt tag, PetscMPIInt nrecvs, const PetscMPIInt onodes[], const PetscMPIInt olengths[], PetscScalar ***rbuf, MPI_Request **r_waits)
317: {
318:   PetscMPIInt   i;
319:   PetscScalar **rbuf_t;
320:   MPI_Request  *r_waits_t;
321:   PetscInt      len = 0;

323:   PetscFunctionBegin;
324:   /* compute memory required for recv buffers */
325:   for (i = 0; i < nrecvs; i++) len += olengths[i]; /* each message length */

327:   /* allocate memory for recv buffers */
328:   PetscCall(PetscMalloc1(nrecvs + 1, &rbuf_t));
329:   PetscCall(PetscMalloc1(len, &rbuf_t[0]));
330:   for (i = 1; i < nrecvs; ++i) rbuf_t[i] = rbuf_t[i - 1] + olengths[i - 1];

332:   /* Post the receives */
333:   PetscCall(PetscMalloc1(nrecvs, &r_waits_t));
334:   for (i = 0; i < nrecvs; ++i) PetscCallMPI(MPIU_Irecv(rbuf_t[i], olengths[i], MPIU_SCALAR, onodes[i], tag, comm, r_waits_t + i));

336:   *rbuf    = rbuf_t;
337:   *r_waits = r_waits_t;
338:   PetscFunctionReturn(PETSC_SUCCESS);
339: }