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

     27:   buflen = (direction == PETSCSF_../../../../../..2LEAF) ? bas->rootbuflen[PETSCSF_REMOTE] : sf->leafbuflen[PETSCSF_REMOTE];
     28:   if (buflen) {
     29:     if (direction == PETSCSF_../../../../../..2LEAF) {
     30:       nreqs  = bas->nrootreqs;
     31:       PetscSFLinkCopyRootBufferInCaseNotUseGpuAwareMPI(sf,link,PETSC_TRUE/*device2host before sending */);
     32:       PetscSFLinkGetMPIBuffersAndRequests(sf,link,direction,NULL,NULL,&reqs,NULL);
     33:     } else { /* leaf to root */
     34:       nreqs  = sf->nleafreqs;
     35:       PetscSFLinkCopyLeafBufferInCaseNotUseGpuAwareMPI(sf,link,PETSC_TRUE);
     36:       PetscSFLinkGetMPIBuffersAndRequests(sf,link,direction,NULL,NULL,NULL,&reqs);
     37:     }
     38:     PetscSFLinkSyncStreamBeforeCallMPI(sf,link,direction);
     39:     MPI_Startall_isend(buflen,link->unit,nreqs,reqs);
     40:   }
     41:   return 0;
     42: }

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

     50:   MPI_Waitall(bas->nrootreqs,link->rootreqs[direction][rootmtype_mpi][rootdirect_mpi],MPI_STATUSES_IGNORE);
     51:   MPI_Waitall(sf->nleafreqs, link->leafreqs[direction][leafmtype_mpi][leafdirect_mpi],MPI_STATUSES_IGNORE);
     52:   if (direction == PETSCSF_../../../../../..2LEAF) {
     53:     PetscSFLinkCopyLeafBufferInCaseNotUseGpuAwareMPI(sf,link,PETSC_FALSE/* host2device after recving */);
     54:   } else {
     55:     PetscSFLinkCopyRootBufferInCaseNotUseGpuAwareMPI(sf,link,PETSC_FALSE);
     56:   }
     57:   return 0;
     58: }

     60: /*
     61:    The routine Creates a communication link for the given operation. It first looks up its link cache. If
     62:    there is a free & suitable one, it uses it. Otherwise it creates a new one.

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

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

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

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

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

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

    114:   direction = (sfop == PETSCSF_BCAST)? PETSCSF_../../../../../..2LEAF : PETSCSF_LEAF2../../../../../..;
    115:   nrootreqs = bas->nrootreqs;
    116:   nleafreqs = sf->nleafreqs;

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

    142:   PetscNew(&link);
    143:   PetscSFLinkSetUp_Host(sf,link,unit);
    144:   PetscCommGetNewTag(PetscObjectComm((PetscObject)sf),&link->tag); /* One tag per link */

    146:   nreqs = (nrootreqs+nleafreqs)*8;
    147:   PetscMalloc1(nreqs,&link->reqs);
    148:   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 */

    150:   for (i=0; i<2; i++) { /* Two communication directions */
    151:     for (j=0; j<2; j++) { /* Two memory types */
    152:       for (k=0; k<2; k++) { /* root/leafdirect 0 or 1 */
    153:         link->rootreqs[i][j][k] = link->reqs + nrootreqs*(4*i+2*j+k);
    154:         link->leafreqs[i][j][k] = link->reqs + nrootreqs*8 + nleafreqs*(4*i+2*j+k);
    155:       }
    156:     }
    157:   }
    158:   link->StartCommunication    = PetscSFLinkStartRequests_MPI;
    159:   link->FinishCommunication   = PetscSFLinkWaitRequests_MPI;

    161: found:

    163: #if defined(PETSC_HAVE_DEVICE)
    164:   if ((PetscMemTypeDevice(xrootmtype) || PetscMemTypeDevice(xleafmtype)) && !link->deviceinited) {
    165:     #if defined(PETSC_HAVE_CUDA)
    166:       if (sf->backend == PETSCSF_BACKEND_CUDA)   PetscSFLinkSetUp_CUDA(sf,link,unit); /* Setup streams etc */
    167:     #endif
    168:     #if defined(PETSC_HAVE_HIP)
    169:       if (sf->backend == PETSCSF_BACKEND_HIP)    PetscSFLinkSetUp_HIP(sf,link,unit); /* Setup streams etc */
    170:     #endif
    171:     #if defined(PETSC_HAVE_KOKKOS)
    172:       if (sf->backend == PETSCSF_BACKEND_KOKKOS) PetscSFLinkSetUp_Kokkos(sf,link,unit);
    173:     #endif
    174:   }
    175: #endif

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

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

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

    220:   /* Set `current` state of the link. They may change between different SF invocations with the same link */
    221:   if (sf->persistent) { /* If data is directly passed to MPI and inits MPI requests, record the data for comparison on future invocations */
    222:     if (rootdirect_mpi) link->rootdatadirect[direction][rootmtype] = rootdata;
    223:     if (leafdirect_mpi) link->leafdatadirect[direction][leafmtype] = leafdata;
    224:   }

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

    239:   link->next            = bas->inuse;
    240:   bas->inuse            = link;
    241:   *mylink               = link;
    242:   return 0;
    243: }