Actual source code: mpimesg.c

  1: #define PETSC_DLL

 3:  #include petscsys.h


  8: /*@C
  9:   PetscGatherNumberOfMessages -  Computes the number of messages a node expects to receive

 11:   Collective on MPI_Comm

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

 20:   Output Parameters:
 21: . nrecvs    - number of messages received

 23:   Level: developer

 25:   Concepts: mpi utility

 27:   Notes:
 28:   With this info, the correct message lengths can be determined using
 29:   PetscGatherMessageLengths()

 31:   Either iflags or ilengths should be provided.  If iflags is not
 32:   provided (PETSC_NULL) it can be computed from ilengths. If iflags is
 33:   provided, ilengths is not required.

 35: .seealso: PetscGatherMessageLengths()
 36: @*/
 37: PetscErrorCode  PetscGatherNumberOfMessages(MPI_Comm comm,PetscMPIInt *iflags,PetscMPIInt *ilengths,PetscMPIInt *nrecvs)
 38: {
 39:   PetscMPIInt    size,rank,*recv_buf,i,*iflags_local = PETSC_NULL,*iflags_localm = PETSC_NULL;


 44:   MPI_Comm_size(comm,&size);
 45:   MPI_Comm_rank(comm,&rank);

 47:   PetscMalloc2(size,PetscMPIInt,&recv_buf,size,PetscMPIInt,&iflags_localm);

 49:   /* If iflags not provided, compute iflags from ilengths */
 50:   if (!iflags) {
 51:     if (!ilengths) SETERRQ(PETSC_ERR_ARG_WRONGSTATE,"Either iflags or ilengths should be provided");
 52:     iflags_local = iflags_localm;
 53:     for (i=0; i<size; i++) {
 54:       if (ilengths[i])  iflags_local[i] = 1;
 55:       else iflags_local[i] = 0;
 56:     }
 57:   } else {
 58:     iflags_local = iflags;
 59:   }

 61:   /* Post an allreduce to determine the numer of messages the current node will receive */
 62:   MPI_Allreduce(iflags_local,recv_buf,size,MPI_INT,MPI_SUM,comm);
 63:   *nrecvs = recv_buf[rank];

 65:   PetscFree2(recv_buf,iflags_localm);
 66:   return(0);
 67: }


 72: /*@C
 73:   PetscGatherMessageLengths - Computes info about messages that a MPI-node will receive, 
 74:   including (from-id,length) pairs for each message.

 76:   Collective on MPI_Comm

 78:   Input Parameters:
 79: + comm      - Communicator
 80: . nsends    - number of messages that are to be sent.
 81: . nrecvs    - number of messages being received
 82: - ilengths  - an array of integers of length sizeof(comm)
 83:               a non zero ilengths[i] represent a message to i of length ilengths[i] 


 86:   Output Parameters:
 87: + onodes    - list of node-ids from which messages are expected
 88: - olengths  - corresponding message lengths

 90:   Level: developer

 92:   Concepts: mpi utility

 94:   Notes:
 95:   With this info, the correct MPI_Irecv() can be posted with the correct
 96:   from-id, with a buffer with the right amount of memory required.

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

100:   To determine nrecevs, one can use PetscGatherNumberOfMessages()

102: .seealso: PetscGatherNumberOfMessages()
103: @*/
104: PetscErrorCode  PetscGatherMessageLengths(MPI_Comm comm,PetscMPIInt nsends,PetscMPIInt nrecvs,PetscMPIInt *ilengths,PetscMPIInt **onodes,PetscMPIInt **olengths)
105: {
107:   PetscMPIInt    size,tag,i,j;
108:   MPI_Request    *s_waits = PETSC_NULL,*r_waits = PETSC_NULL;
109:   MPI_Status     *w_status = PETSC_NULL;

112:   MPI_Comm_size(comm,&size);
113:   PetscCommGetNewTag(comm,&tag);

115:   /* cannot use PetscMalloc3() here because in the call to MPI_Waitall() they MUST be contiguous */
116:   PetscMalloc2(nrecvs+nsends,MPI_Request,&r_waits,nrecvs+nsends,MPI_Status,&w_status);
117:   s_waits = r_waits+nrecvs;

119:   /* Post the Irecv to get the message length-info */
120:   PetscMalloc(nrecvs*sizeof(PetscMPIInt),olengths);
121:   for (i=0; i<nrecvs; i++) {
122:     MPI_Irecv((*olengths)+i,1,MPI_INT,MPI_ANY_SOURCE,tag,comm,r_waits+i);
123:   }

125:   /* Post the Isends with the message length-info */
126:   for (i=0,j=0; i<size; ++i) {
127:     if (ilengths[i]) {
128:       MPI_Isend(ilengths+i,1,MPI_INT,i,tag,comm,s_waits+j);
129:       j++;
130:     }
131:   }

133:   /* Post waits on sends and receivs */
134:   if (nrecvs+nsends) {MPI_Waitall(nrecvs+nsends,r_waits,w_status);}
135: 
136:   /* Pack up the received data */
137:   PetscMalloc(nrecvs*sizeof(PetscMPIInt),onodes);
138:   for (i=0; i<nrecvs; ++i) {
139:     (*onodes)[i] = w_status[i].MPI_SOURCE;
140:   }
141:   PetscFree2(r_waits,w_status);
142:   return(0);
143: }
146: /*@C
147:   PetscGatherMessageLengths2 - Computes info about messages that a MPI-node will receive, 
148:   including (from-id,length) pairs for each message. Same functionality as PetscGatherMessageLengths()
149:   except it takes TWO ilenths and output TWO olengths.

151:   Collective on MPI_Comm

153:   Input Parameters:
154: + comm      - Communicator
155: . nsends    - number of messages that are to be sent.
156: . nrecvs    - number of messages being received
157: - ilengths1, ilengths2 - array of integers of length sizeof(comm)
158:               a non zero ilengths[i] represent a message to i of length ilengths[i] 

160:   Output Parameters:
161: + onodes    - list of node-ids from which messages are expected
162: - olengths1, olengths2 - corresponding message lengths

164:   Level: developer

166:   Concepts: mpi utility

168:   Notes:
169:   With this info, the correct MPI_Irecv() can be posted with the correct
170:   from-id, with a buffer with the right amount of memory required.

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

174:   To determine nrecevs, one can use PetscGatherNumberOfMessages()

176: .seealso: PetscGatherMessageLengths() and PetscGatherNumberOfMessages()
177: @*/
178: PetscErrorCode  PetscGatherMessageLengths2(MPI_Comm comm,PetscMPIInt nsends,PetscMPIInt nrecvs,PetscMPIInt *ilengths1,PetscMPIInt *ilengths2,PetscMPIInt **onodes,PetscMPIInt **olengths1,PetscMPIInt **olengths2)
179: {
181:   PetscMPIInt    size,tag,i,j,*buf_s = PETSC_NULL,*buf_r = PETSC_NULL,*buf_j = PETSC_NULL;
182:   MPI_Request    *s_waits = PETSC_NULL,*r_waits = PETSC_NULL;
183:   MPI_Status     *w_status = PETSC_NULL;

186:   MPI_Comm_size(comm,&size);
187:   PetscCommGetNewTag(comm,&tag);

189:   /* cannot use PetscMalloc5() because r_waits and s_waits must be contiquous for the call to MPI_Waitall() */
190:   PetscMalloc4(nrecvs+nsends,MPI_Request,&r_waits,2*nrecvs,PetscMPIInt,&buf_r,2*nsends,PetscMPIInt,&buf_s,nrecvs+nsends,MPI_Status,&w_status);
191:   s_waits = r_waits + nrecvs;

193:   /* Post the Irecv to get the message length-info */
194:   PetscMalloc((nrecvs+1)*sizeof(PetscMPIInt),olengths1);
195:   PetscMalloc((nrecvs+1)*sizeof(PetscMPIInt),olengths2);
196:   for (i=0; i<nrecvs; i++) {
197:     buf_j = buf_r + (2*i);
198:     MPI_Irecv(buf_j,2,MPI_INT,MPI_ANY_SOURCE,tag,comm,r_waits+i);
199:   }

201:   /* Post the Isends with the message length-info */
202:   for (i=0,j=0; i<size; ++i) {
203:     if (ilengths1[i]) {
204:       buf_j = buf_s + (2*j);
205:       buf_j[0] = *(ilengths1+i);
206:       buf_j[1] = *(ilengths2+i);
207:       MPI_Isend(buf_j,2,MPI_INT,i,tag,comm,s_waits+j);
208:       j++;
209:     }
210:   }
211: 
212:   /* Post waits on sends and receivs */
213:   if (nrecvs+nsends) {MPI_Waitall(nrecvs+nsends,r_waits,w_status);}

215: 
216:   /* Pack up the received data */
217:   PetscMalloc((nrecvs+1)*sizeof(PetscMPIInt),onodes);
218:   for (i=0; i<nrecvs; ++i) {
219:     (*onodes)[i] = w_status[i].MPI_SOURCE;
220:     buf_j = buf_r + (2*i);
221:     (*olengths1)[i] = buf_j[0];
222:     (*olengths2)[i] = buf_j[1];
223:   }

225:   PetscFree4(r_waits,buf_r,buf_s,w_status);
226:   return(0);
227: }

229: /*

231:   Allocate a bufffer sufficient to hold messages of size specified in olengths.
232:   And post Irecvs on these buffers using node info from onodes
233:   
234:  */
237: PetscErrorCode  PetscPostIrecvInt(MPI_Comm comm,PetscMPIInt tag,PetscMPIInt nrecvs,PetscMPIInt *onodes,PetscMPIInt *olengths,PetscInt ***rbuf,MPI_Request **r_waits)
238: {
240:   PetscInt       len=0,**rbuf_t,i;
241:   MPI_Request    *r_waits_t;


245:   /* compute memory required for recv buffers */
246:   for (i=0; i<nrecvs; i++) len += olengths[i];  /* each message length */
247:   len *= sizeof(PetscInt);
248:   len += (nrecvs+1)*sizeof(PetscInt*); /* Array of pointers for each message */

250:   /* allocate memory for recv buffers */
251:   PetscMalloc(len,&rbuf_t);
252:   rbuf_t[0] = (PetscInt*)(rbuf_t + nrecvs);
253:   for (i=1; i<nrecvs; ++i) rbuf_t[i] = rbuf_t[i-1] + olengths[i-1];

255:   /* Post the receives */
256:   PetscMalloc((nrecvs+1)*sizeof(MPI_Request),&r_waits_t);
257:   for (i=0; i<nrecvs; ++i) {
258:     MPI_Irecv(rbuf_t[i],olengths[i],MPIU_INT,onodes[i],tag,comm,r_waits_t+i);
259:   }

261:   *rbuf    = rbuf_t;
262:   *r_waits = r_waits_t;
263:   return(0);
264: }

268: PetscErrorCode  PetscPostIrecvScalar(MPI_Comm comm,PetscMPIInt tag,PetscMPIInt nrecvs,PetscMPIInt *onodes,PetscMPIInt *olengths,PetscScalar ***rbuf,MPI_Request **r_waits)
269: {
271:   PetscMPIInt    len=0,i;
272:   PetscScalar    **rbuf_t;
273:   MPI_Request    *r_waits_t;


277:   /* compute memory required for recv buffers */
278:   for (i=0; i<nrecvs; i++) len += olengths[i];  /* each message length */
279:   len *= sizeof(PetscScalar);
280:   len += (nrecvs+1)*sizeof(PetscScalar*); /* Array of pointers for each message */


283:   /* allocate memory for recv buffers */
284:   PetscMalloc(len,&rbuf_t);
285:   rbuf_t[0] = (PetscScalar*)(rbuf_t + nrecvs);
286:   for (i=1; i<nrecvs; ++i) rbuf_t[i] = rbuf_t[i-1] + olengths[i-1];

288:   /* Post the receives */
289:   PetscMalloc((nrecvs+1)*sizeof(MPI_Request),&r_waits_t);
290:   for (i=0; i<nrecvs; ++i) {
291:     MPI_Irecv(rbuf_t[i],olengths[i],MPIU_SCALAR,onodes[i],tag,comm,r_waits_t+i);
292:   }

294:   *rbuf    = rbuf_t;
295:   *r_waits = r_waits_t;
296:   return(0);
297: }