Actual source code: vscatcusp.c

petsc-3.6.1 2015-07-22
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  1: #include <petsc/private/isimpl.h>
  2: #include <petsc/private/vecimpl.h>             /*I "petscvec.h" I*/

  4: PETSC_INTERN PetscErrorCode VecScatterCUSPIndicesCreate_PtoP(PetscInt,PetscInt*,PetscInt,PetscInt*,PetscCUSPIndices*);

  8: /*@
  9:    VecScatterInitializeForGPU - Initializes a generalized scatter from one vector to
 10:  another for GPU based computation.  Effectively, this function creates all the
 11:  necessary indexing buffers and work vectors needed to move data only those data points
 12:  in a vector which need to be communicated across ranks. This is done at the first time
 13:  this function is called. Currently, this only used in the context of the parallel
 14:  SpMV call in MatMult_MPIAIJCUSP (in mpi/mpicusp/mpiaijcusp.cu) or MatMult_MPIAIJCUSPARSE
 15:  (in mpi/mpicusparse/mpiaijcusparse.cu). This function is executed before the call to
 16:  MatMult. This enables the memory transfers to be overlapped with the MatMult SpMV kernel
 17:  call.

 19:    Input Parameters:
 20: +  inctx - scatter context generated by VecScatterCreate()
 21: .  x - the vector from which we scatter
 22: -  mode - the scattering mode, usually SCATTER_FORWARD.  The available modes are:
 23:     SCATTER_FORWARD or SCATTER_REVERSE

 25:   Level: intermediate

 27: .seealso: VecScatterCreate(), VecScatterEnd()
 28: @*/
 29: PetscErrorCode  VecScatterInitializeForGPU(VecScatter inctx,Vec x,ScatterMode mode)
 30: {
 31:   VecScatter_MPI_General *to,*from;
 32:   PetscErrorCode         ierr;
 33:   PetscInt               i,*indices,*sstartsSends,*sstartsRecvs,nrecvs,nsends,bs;
 34:   PetscBool              isSeq1,isSeq2;

 37:   VecScatterIsSequential_Private((VecScatter_Common*)inctx->fromdata,&isSeq1);
 38:   VecScatterIsSequential_Private((VecScatter_Common*)inctx->todata,&isSeq2);
 39:   if (isSeq1 || isSeq2) {
 40:     return(0);
 41:   }
 42:   if (mode & SCATTER_REVERSE) {
 43:     to     = (VecScatter_MPI_General*)inctx->fromdata;
 44:     from   = (VecScatter_MPI_General*)inctx->todata;
 45:   } else {
 46:     to     = (VecScatter_MPI_General*)inctx->todata;
 47:     from   = (VecScatter_MPI_General*)inctx->fromdata;
 48:   }
 49:   bs           = to->bs;
 50:   nrecvs       = from->n;
 51:   nsends       = to->n;
 52:   indices      = to->indices;
 53:   sstartsSends = to->starts;
 54:   sstartsRecvs = from->starts;
 55:   if (x->valid_GPU_array != PETSC_CUSP_UNALLOCATED && (nsends>0 || nrecvs>0)) {
 56:     if (!inctx->spptr) {
 57:       PetscInt k,*tindicesSends,*sindicesSends,*tindicesRecvs,*sindicesRecvs;
 58:       PetscInt ns = sstartsSends[nsends],nr = sstartsRecvs[nrecvs];
 59:       /* Here we create indices for both the senders and receivers. */
 60:       PetscMalloc1(ns,&tindicesSends);
 61:       PetscMalloc1(nr,&tindicesRecvs);

 63:       PetscMemcpy(tindicesSends,indices,ns*sizeof(PetscInt));
 64:       PetscMemcpy(tindicesRecvs,from->indices,nr*sizeof(PetscInt));

 66:       PetscSortRemoveDupsInt(&ns,tindicesSends);
 67:       PetscSortRemoveDupsInt(&nr,tindicesRecvs);

 69:       PetscMalloc1(bs*ns,&sindicesSends);
 70:       PetscMalloc1(from->bs*nr,&sindicesRecvs);

 72:       /* sender indices */
 73:       for (i=0; i<ns; i++) {
 74:         for (k=0; k<bs; k++) sindicesSends[i*bs+k] = tindicesSends[i]+k;
 75:       }
 76:       PetscFree(tindicesSends);

 78:       /* receiver indices */
 79:       for (i=0; i<nr; i++) {
 80:         for (k=0; k<from->bs; k++) sindicesRecvs[i*from->bs+k] = tindicesRecvs[i]+k;
 81:       }
 82:       PetscFree(tindicesRecvs);

 84:       /* create GPU indices, work vectors, ... */
 85:       VecScatterCUSPIndicesCreate_PtoP(ns*bs,sindicesSends,nr*from->bs,sindicesRecvs,(PetscCUSPIndices*)&inctx->spptr);
 86:       PetscFree(sindicesSends);
 87:       PetscFree(sindicesRecvs);
 88:     }
 89:   }
 90:   return(0);
 91: }

 95: /*@
 96:    VecScatterFinalizeForGPU - Finalizes a generalized scatter from one vector to
 97:  another for GPU based computation. Effectively, this function resets the temporary
 98:  buffer flags. Currently, this only used in the context of the parallel SpMV call in
 99:  in MatMult_MPIAIJCUSP (in mpi/mpicusp/mpiaijcusp.cu) or MatMult_MPIAIJCUSPARSE
100:  (in mpi/mpicusparse/mpiaijcusparse.cu). Once the MatMultAdd is finished,
101:  the GPU temporary buffers used for messaging are no longer valid.

103:    Input Parameters:
104: +  inctx - scatter context generated by VecScatterCreate()

106:   Level: intermediate

108: @*/
109: PetscErrorCode  VecScatterFinalizeForGPU(VecScatter inctx)
110: {
112:   return(0);
113: }