Actual source code: sfalltoall.c
petsc-3.15.0 2021-03-30
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      1: #include <../src/vec/is/sf/impls/basic/allgatherv/sfallgatherv.h>
      2: #include <../src/vec/is/sf/impls/basic/allgather/sfallgather.h>
      3: #include <../src/vec/is/sf/impls/basic/gatherv/sfgatherv.h>

      5: /* Reuse the type. The difference is some fields (i.e., displs, recvcounts) are not used, which is not a big deal */
      6: typedef PetscSF_Allgatherv PetscSF_Alltoall;

      8: /*===================================================================================*/
      9: /*              Implementations of SF public APIs                                    */
     10: /*===================================================================================*/
     11: static PetscErrorCode PetscSFGetGraph_Alltoall(PetscSF sf,PetscInt *nroots,PetscInt *nleaves,const PetscInt **ilocal,const PetscSFNode **iremote)
     12: {
     14:   PetscInt       i;

     17:   if (nroots)  *nroots  = sf->nroots;
     18:   if (nleaves) *nleaves = sf->nleaves;
     19:   if (ilocal)  *ilocal  = NULL; /* Contiguous local indices */
     20:   if (iremote) {
     21:     if (!sf->remote) {
     22:       PetscMalloc1(sf->nleaves,&sf->remote);
     23:       sf->remote_alloc = sf->remote;
     24:       for (i=0; i<sf->nleaves; i++) {
     25:         sf->remote[i].rank  = i;
     26:         sf->remote[i].index = i;
     27:       }
     28:     }
     29:     *iremote = sf->remote;
     30:   }
     31:   return(0);
     32: }

     34: static PetscErrorCode PetscSFBcastBegin_Alltoall(PetscSF sf,MPI_Datatype unit,PetscMemType rootmtype,const void *rootdata,PetscMemType leafmtype,void *leafdata,MPI_Op op)
     35: {
     36:   PetscErrorCode       ierr;
     37:   PetscSFLink          link;
     38:   MPI_Comm             comm;
     39:   void                 *rootbuf = NULL,*leafbuf = NULL; /* buffer used by MPI */
     40:   MPI_Request          *req;

     43:   PetscSFLinkCreate(sf,unit,rootmtype,rootdata,leafmtype,leafdata,op,PETSCSF_BCAST,&link);
     44:   PetscSFLinkPackRootData(sf,link,PETSCSF_REMOTE,rootdata);
     45:   PetscSFLinkCopyRootBufferInCaseNotUseGpuAwareMPI(sf,link,PETSC_TRUE/* device2host before sending */);
     46:   PetscObjectGetComm((PetscObject)sf,&comm);
     47:   PetscSFLinkGetMPIBuffersAndRequests(sf,link,PETSCSF_../../../../../..2LEAF,&rootbuf,&leafbuf,&req,NULL);
     48:   PetscSFLinkSyncStreamBeforeCallMPI(sf,link,PETSCSF_../../../../../..2LEAF);
     49:   MPIU_Ialltoall(rootbuf,1,unit,leafbuf,1,unit,comm,req);
     50:   return(0);
     51: }

     53: static PetscErrorCode PetscSFReduceBegin_Alltoall(PetscSF sf,MPI_Datatype unit,PetscMemType leafmtype,const void *leafdata,PetscMemType rootmtype,void *rootdata,MPI_Op op)
     54: {
     55:   PetscErrorCode       ierr;
     56:   PetscSFLink          link;
     57:   MPI_Comm             comm;
     58:   void                 *rootbuf = NULL,*leafbuf = NULL; /* buffer used by MPI */
     59:   MPI_Request          *req;

     62:   PetscSFLinkCreate(sf,unit,rootmtype,rootdata,leafmtype,leafdata,op,PETSCSF_REDUCE,&link);
     63:   PetscSFLinkPackLeafData(sf,link,PETSCSF_REMOTE,leafdata);
     64:   PetscSFLinkCopyLeafBufferInCaseNotUseGpuAwareMPI(sf,link,PETSC_TRUE/* device2host before sending */);
     65:   PetscObjectGetComm((PetscObject)sf,&comm);
     66:   PetscSFLinkGetMPIBuffersAndRequests(sf,link,PETSCSF_LEAF2../../../../../..,&rootbuf,&leafbuf,&req,NULL);
     67:   PetscSFLinkSyncStreamBeforeCallMPI(sf,link,PETSCSF_LEAF2../../../../../..);
     68:   MPIU_Ialltoall(leafbuf,1,unit,rootbuf,1,unit,comm,req);
     69:   return(0);
     70: }

     72: static PetscErrorCode PetscSFCreateLocalSF_Alltoall(PetscSF sf,PetscSF *out)
     73: {
     75:   PetscInt       nroots = 1,nleaves = 1,*ilocal;
     76:   PetscSFNode    *iremote = NULL;
     77:   PetscSF        lsf;
     78:   PetscMPIInt    rank;

     81:   nroots  = 1;
     82:   nleaves = 1;
     83:   MPI_Comm_rank(PetscObjectComm((PetscObject)sf),&rank);
     84:   PetscMalloc1(nleaves,&ilocal);
     85:   PetscMalloc1(nleaves,&iremote);
     86:   ilocal[0]        = rank;
     87:   iremote[0].rank  = 0;    /* rank in PETSC_COMM_SELF */
     88:   iremote[0].index = rank; /* LocalSF is an embedded SF. Indices are not remapped */

     90:   PetscSFCreate(PETSC_COMM_SELF,&lsf);
     91:   PetscSFSetGraph(lsf,nroots,nleaves,NULL/*contiguous leaves*/,PETSC_OWN_POINTER,iremote,PETSC_OWN_POINTER);
     92:   PetscSFSetUp(lsf);
     93:   *out = lsf;
     94:   return(0);
     95: }

     97: static PetscErrorCode PetscSFCreateEmbeddedRootSF_Alltoall(PetscSF sf,PetscInt nselected,const PetscInt *selected,PetscSF *newsf)
     98: {
    100:   PetscInt       i,*tmproots,*ilocal,ndranks,ndiranks;
    101:   PetscSFNode    *iremote;
    102:   PetscMPIInt    nroots,*roots,nleaves,*leaves,rank;
    103:   MPI_Comm       comm;
    104:   PetscSF_Basic  *bas;
    105:   PetscSF        esf;

    108:   PetscObjectGetComm((PetscObject)sf,&comm);
    109:   MPI_Comm_rank(comm,&rank);

    111:   /* Uniq selected[] and store the result in roots[] */
    112:   PetscMalloc1(nselected,&tmproots);
    113:   PetscArraycpy(tmproots,selected,nselected);
    114:   PetscSortRemoveDupsInt(&nselected,tmproots); /* nselected might be changed */
    115:   if (tmproots[0] < 0 || tmproots[nselected-1] >= sf->nroots) SETERRQ3(comm,PETSC_ERR_ARG_OUTOFRANGE,"Min/Max root indices %D/%D are not in [0,%D)",tmproots[0],tmproots[nselected-1],sf->nroots);
    116:   nroots = nselected;   /* For Alltoall, we know root indices will not overflow MPI_INT */
    117:   PetscMalloc1(nselected,&roots);
    118:   for (i=0; i<nselected; i++) roots[i] = tmproots[i];
    119:   PetscFree(tmproots);

    121:   /* Find out which leaves are still connected to roots in the embedded sf. Expect PetscCommBuildTwoSided is more scalable than MPI_Alltoall */
    122:   PetscCommBuildTwoSided(comm,0/*empty msg*/,MPI_INT/*fake*/,nroots,roots,NULL/*todata*/,&nleaves,&leaves,NULL/*fromdata*/);

    124:   /* Move myself ahead if rank is in leaves[], since I am a distinguished rank */
    125:   ndranks = 0;
    126:   for (i=0; i<nleaves; i++) {
    127:     if (leaves[i] == rank) {leaves[i] = -rank; ndranks = 1; break;}
    128:   }
    129:   PetscSortMPIInt(nleaves,leaves);
    130:   if (nleaves && leaves[0] < 0) leaves[0] = rank;

    132:   /* Build esf and fill its fields manually (without calling PetscSFSetUp) */
    133:   PetscMalloc1(nleaves,&ilocal);
    134:   PetscMalloc1(nleaves,&iremote);
    135:   for (i=0; i<nleaves; i++) { /* 1:1 map from roots to leaves */
    136:     ilocal[i]        = leaves[i];
    137:     iremote[i].rank  = leaves[i];
    138:     iremote[i].index = leaves[i];
    139:   }
    140:   PetscSFCreate(comm,&esf);
    141:   PetscSFSetType(esf,PETSCSFBASIC); /* This optimized routine can only create a basic sf */
    142:   PetscSFSetGraph(esf,sf->nleaves,nleaves,ilocal,PETSC_OWN_POINTER,iremote,PETSC_OWN_POINTER);

    144:   /* As if we are calling PetscSFSetUpRanks(esf,self's group) */
    145:   PetscMalloc4(nleaves,&esf->ranks,nleaves+1,&esf->roffset,nleaves,&esf->rmine,nleaves,&esf->rremote);
    146:   esf->nranks     = nleaves;
    147:   esf->ndranks    = ndranks;
    148:   esf->roffset[0] = 0;
    149:   for (i=0; i<nleaves; i++) {
    150:     esf->ranks[i]     = leaves[i];
    151:     esf->roffset[i+1] = i+1;
    152:     esf->rmine[i]     = leaves[i];
    153:     esf->rremote[i]   = leaves[i];
    154:   }

    156:   /* Set up esf->data, the incoming communication (i.e., recv info), which is usually done by PetscSFSetUp_Basic */
    157:   bas  = (PetscSF_Basic*)esf->data;
    158:   PetscMalloc2(nroots,&bas->iranks,nroots+1,&bas->ioffset);
    159:   PetscMalloc1(nroots,&bas->irootloc);
    160:   /* Move myself ahead if rank is in roots[], since I am a distinguished irank */
    161:   ndiranks = 0;
    162:   for (i=0; i<nroots; i++) {
    163:     if (roots[i] == rank) {roots[i] = -rank; ndiranks = 1; break;}
    164:   }
    165:   PetscSortMPIInt(nroots,roots);
    166:   if (nroots && roots[0] < 0) roots[0] = rank;

    168:   bas->niranks    = nroots;
    169:   bas->ndiranks   = ndiranks;
    170:   bas->ioffset[0] = 0;
    171:   bas->itotal     = nroots;
    172:   for (i=0; i<nroots; i++) {
    173:     bas->iranks[i]    = roots[i];
    174:     bas->ioffset[i+1] = i+1;
    175:     bas->irootloc[i]  = roots[i];
    176:   }

    178:   /* See PetscSFCreateEmbeddedRootSF_Basic */
    179:   esf->nleafreqs  = esf->nranks - esf->ndranks;
    180:   bas->nrootreqs  = bas->niranks - bas->ndiranks;
    181:   esf->persistent = PETSC_TRUE;
    182:   /* Setup packing related fields */
    183:   PetscSFSetUpPackFields(esf);

    185:   esf->setupcalled = PETSC_TRUE; /* We have done setup ourselves! */
    186:   *newsf = esf;
    187:   return(0);
    188: }

    190: PETSC_INTERN PetscErrorCode PetscSFCreate_Alltoall(PetscSF sf)
    191: {
    192:   PetscErrorCode   ierr;
    193:   PetscSF_Alltoall *dat = (PetscSF_Alltoall*)sf->data;

    196:   sf->ops->BcastEnd        = PetscSFBcastEnd_Basic;
    197:   sf->ops->ReduceEnd       = PetscSFReduceEnd_Basic;

    199:   /* Inherit from Allgatherv. It is astonishing Alltoall can inherit so much from Allgather(v) */
    200:   sf->ops->Destroy         = PetscSFDestroy_Allgatherv;
    201:   sf->ops->Reset           = PetscSFReset_Allgatherv;
    202:   sf->ops->FetchAndOpEnd   = PetscSFFetchAndOpEnd_Allgatherv;
    203:   sf->ops->GetRootRanks    = PetscSFGetRootRanks_Allgatherv;

    205:   /* Inherit from Allgather. Every process gathers equal-sized data from others, which enables this inheritance. */
    206:   sf->ops->GetLeafRanks    = PetscSFGetLeafRanks_Allgatherv;
    207:   sf->ops->SetUp           = PetscSFSetUp_Allgather;

    209:   /* Inherit from Gatherv. Each root has only one leaf connected, which enables this inheritance */
    210:   sf->ops->FetchAndOpBegin = PetscSFFetchAndOpBegin_Gatherv;

    212:   /* Alltoall stuff */
    213:   sf->ops->GetGraph             = PetscSFGetGraph_Alltoall;
    214:   sf->ops->BcastBegin           = PetscSFBcastBegin_Alltoall;
    215:   sf->ops->ReduceBegin          = PetscSFReduceBegin_Alltoall;
    216:   sf->ops->CreateLocalSF        = PetscSFCreateLocalSF_Alltoall;
    217:   sf->ops->CreateEmbeddedRootSF = PetscSFCreateEmbeddedRootSF_Alltoall;

    219:   PetscNewLog(sf,&dat);
    220:   sf->data = (void*)dat;
    221:   return(0);
    222: }