Actual source code: mpimesg.c

      2: #include <petscsys.h>

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

      8:   Collective

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

     17:   Output Parameters:
     18: . nrecvs    - number of messages received

     20:   Level: developer

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

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

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

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

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

     43:   /* If iflags not provided, compute iflags from ilengths */
     44:   if (!iflags) {
     45:     if (!ilengths) SETERRQ(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 numer of messages the current node will receive */
     54:   MPIU_Allreduce(iflags_local,recv_buf,size,MPI_INT,MPI_SUM,comm);
     55:   *nrecvs = recv_buf[rank];

     57:   PetscFree2(recv_buf,iflags_localm);
     58:   return(0);
     59: }

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

     66:   Collective

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

     76:   Output Parameters:
     77: + onodes    - list of node-ids from which messages are expected
     78: - olengths  - corresponding message lengths

     80:   Level: developer

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

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

     88:   To determine nrecvs, one can use PetscGatherNumberOfMessages()

     90: .seealso: PetscGatherNumberOfMessages()
     91: @*/
     92: PetscErrorCode  PetscGatherMessageLengths(MPI_Comm comm,PetscMPIInt nsends,PetscMPIInt nrecvs,const PetscMPIInt ilengths[],PetscMPIInt **onodes,PetscMPIInt **olengths)
     93: {
     95:   PetscMPIInt    size,rank,tag,i,j;
     96:   MPI_Request    *s_waits  = NULL,*r_waits = NULL;
     97:   MPI_Status     *w_status = NULL;

    100:   MPI_Comm_size(comm,&size);
    101:   MPI_Comm_rank(comm,&rank);
    102:   PetscCommGetNewTag(comm,&tag);

    104:   /* cannot use PetscMalloc3() here because in the call to MPI_Waitall() they MUST be contiguous */
    105:   PetscMalloc2(nrecvs+nsends,&r_waits,nrecvs+nsends,&w_status);
    106:   s_waits = r_waits+nrecvs;

    108:   /* Post the Irecv to get the message length-info */
    109:   PetscMalloc1(nrecvs,olengths);
    110:   for (i=0; i<nrecvs; i++) {
    111:     MPI_Irecv((*olengths)+i,1,MPI_INT,MPI_ANY_SOURCE,tag,comm,r_waits+i);
    112:   }

    114:   /* Post the Isends with the message length-info */
    115:   for (i=0,j=0; i<size; ++i) {
    116:     if (ilengths[i]) {
    117:       MPI_Isend((void*)(ilengths+i),1,MPI_INT,i,tag,comm,s_waits+j);
    118:       j++;
    119:     }
    120:   }

    122:   /* Post waits on sends and receivs */
    123:   if (nrecvs+nsends) {MPI_Waitall(nrecvs+nsends,r_waits,w_status);}

    125:   /* Pack up the received data */
    126:   PetscMalloc1(nrecvs,onodes);
    127:   for (i=0; i<nrecvs; ++i) {
    128:     (*onodes)[i] = w_status[i].MPI_SOURCE;
    129: #if defined(PETSC_HAVE_OMPI_MAJOR_VERSION)
    130:     /* This line is a workaround for a bug in OpenMPI-2.1.1 distributed by Ubuntu-18.04.2 LTS.
    131:        It happens in self-to-self MPI_Send/Recv using MPI_ANY_SOURCE for message matching. OpenMPI
    132:        does not put correct value in recv buffer. See also
    133:        https://lists.mcs.anl.gov/pipermail/petsc-dev/2019-July/024803.html
    134:        https://www.mail-archive.com/users@lists.open-mpi.org//msg33383.html
    135:      */
    136:     if (w_status[i].MPI_SOURCE == rank) (*olengths)[i] = ilengths[rank];
    137: #endif
    138:   }
    139:   PetscFree2(r_waits,w_status);
    140:   return(0);
    141: }

    143: /*@C
    144:   PetscGatherMessageLengths2 - Computes info about messages that a MPI-node will receive,
    145:   including (from-id,length) pairs for each message. Same functionality as PetscGatherMessageLengths()
    146:   except it takes TWO ilenths and output TWO olengths.

    148:   Collective

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

    157:   Output Parameters:
    158: + onodes    - list of node-ids from which messages are expected
    159: - olengths1, olengths2 - corresponding message lengths

    161:   Level: developer

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

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

    169:   To determine nrecvs, one can use PetscGatherNumberOfMessages()

    171: .seealso: PetscGatherMessageLengths() and PetscGatherNumberOfMessages()
    172: @*/
    173: PetscErrorCode  PetscGatherMessageLengths2(MPI_Comm comm,PetscMPIInt nsends,PetscMPIInt nrecvs,const PetscMPIInt ilengths1[],const PetscMPIInt ilengths2[],PetscMPIInt **onodes,PetscMPIInt **olengths1,PetscMPIInt **olengths2)
    174: {
    176:   PetscMPIInt    size,tag,i,j,*buf_s = NULL,*buf_r = NULL,*buf_j = NULL;
    177:   MPI_Request    *s_waits  = NULL,*r_waits = NULL;
    178:   MPI_Status     *w_status = NULL;

    181:   MPI_Comm_size(comm,&size);
    182:   PetscCommGetNewTag(comm,&tag);

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

    188:   /* Post the Irecv to get the message length-info */
    189:   PetscMalloc1(nrecvs+1,olengths1);
    190:   PetscMalloc1(nrecvs+1,olengths2);
    191:   for (i=0; i<nrecvs; i++) {
    192:     buf_j = buf_r + (2*i);
    193:     MPI_Irecv(buf_j,2,MPI_INT,MPI_ANY_SOURCE,tag,comm,r_waits+i);
    194:   }

    196:   /* Post the Isends with the message length-info */
    197:   for (i=0,j=0; i<size; ++i) {
    198:     if (ilengths1[i]) {
    199:       buf_j    = buf_s + (2*j);
    200:       buf_j[0] = *(ilengths1+i);
    201:       buf_j[1] = *(ilengths2+i);
    202:       MPI_Isend(buf_j,2,MPI_INT,i,tag,comm,s_waits+j);
    203:       j++;
    204:     }
    205:   }
    206:   if (j != nsends) SETERRQ2(PETSC_COMM_SELF,PETSC_ERR_PLIB,"j %d not equal to expected number of sends %d\n",j,nsends);

    208:   /* Post waits on sends and receivs */
    209:   if (nrecvs+nsends) {MPI_Waitall(nrecvs+nsends,r_waits,w_status);}

    212:   /* Pack up the received data */
    213:   PetscMalloc1(nrecvs+1,onodes);
    214:   for (i=0; i<nrecvs; ++i) {
    215:     (*onodes)[i]    = w_status[i].MPI_SOURCE;
    216:     buf_j           = buf_r + (2*i);
    217:     (*olengths1)[i] = buf_j[0];
    218:     (*olengths2)[i] = buf_j[1];
    219:   }

    221:   PetscFree4(r_waits,buf_r,buf_s,w_status);
    222:   return(0);
    223: }

    225: /*

    227:   Allocate a bufffer sufficient to hold messages of size specified in olengths.
    228:   And post Irecvs on these buffers using node info from onodes

    230:  */
    231: PetscErrorCode  PetscPostIrecvInt(MPI_Comm comm,PetscMPIInt tag,PetscMPIInt nrecvs,const PetscMPIInt onodes[],const PetscMPIInt olengths[],PetscInt ***rbuf,MPI_Request **r_waits)
    232: {
    234:   PetscInt       **rbuf_t,i,len = 0;
    235:   MPI_Request    *r_waits_t;

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

    241:   /* allocate memory for recv buffers */
    242:   PetscMalloc1(nrecvs+1,&rbuf_t);
    243:   PetscMalloc1(len,&rbuf_t[0]);
    244:   for (i=1; i<nrecvs; ++i) rbuf_t[i] = rbuf_t[i-1] + olengths[i-1];

    246:   /* Post the receives */
    247:   PetscMalloc1(nrecvs,&r_waits_t);
    248:   for (i=0; i<nrecvs; ++i) {
    249:     MPI_Irecv(rbuf_t[i],olengths[i],MPIU_INT,onodes[i],tag,comm,r_waits_t+i);
    250:   }

    252:   *rbuf    = rbuf_t;
    253:   *r_waits = r_waits_t;
    254:   return(0);
    255: }

    257: PetscErrorCode  PetscPostIrecvScalar(MPI_Comm comm,PetscMPIInt tag,PetscMPIInt nrecvs,const PetscMPIInt onodes[],const PetscMPIInt olengths[],PetscScalar ***rbuf,MPI_Request **r_waits)
    258: {
    260:   PetscMPIInt    i;
    261:   PetscScalar    **rbuf_t;
    262:   MPI_Request    *r_waits_t;
    263:   PetscInt       len = 0;

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

    269:   /* allocate memory for recv buffers */
    270:   PetscMalloc1(nrecvs+1,&rbuf_t);
    271:   PetscMalloc1(len,&rbuf_t[0]);
    272:   for (i=1; i<nrecvs; ++i) rbuf_t[i] = rbuf_t[i-1] + olengths[i-1];

    274:   /* Post the receives */
    275:   PetscMalloc1(nrecvs,&r_waits_t);
    276:   for (i=0; i<nrecvs; ++i) {
    277:     MPI_Irecv(rbuf_t[i],olengths[i],MPIU_SCALAR,onodes[i],tag,comm,r_waits_t+i);
    278:   }

    280:   *rbuf    = rbuf_t;
    281:   *r_waits = r_waits_t;
    282:   return(0);
    283: }