Actual source code: mmbdiag.c

      1: #define PETSCMAT_DLL

      3: /*
      4:    Support for the MPIBDIAG matrix-vector multiply
      5: */
     6:  #include src/mat/impls/bdiag/mpi/mpibdiag.h

     10: PetscErrorCode MatSetUpMultiply_MPIBDiag(Mat mat)
     11: {
     12:   Mat_MPIBDiag   *mbd = (Mat_MPIBDiag*)mat->data;
     13:   Mat_SeqBDiag   *lmbd = (Mat_SeqBDiag*)mbd->A->data;
     15:   PetscInt       N = mat->N,*indices,*garray,ec=0;
     16:   PetscInt       bs = mat->bs,d,i,j,diag;
     17:   IS             to,from;
     18:   Vec            gvec;

     21:   /* We make an array as long as the number of columns */
     22:   /* mark those columns that are in mbd->A */
     23:   PetscMalloc((N+1)*sizeof(PetscInt),&indices);
     24:   PetscMemzero(indices,N*sizeof(PetscInt));

     26:   if (bs == 1) {
     27:     for (d=0; d<lmbd->nd; d++) {
     28:       diag = lmbd->diag[d];
     29:       if (diag > 0) { /* col = loc */
     30:         for (j=0; j<lmbd->bdlen[d]; j++) {
     31:           if (!indices[j]) ec++;
     32:           indices[j] = 1;
     33:         }
     34:       } else { /* col = loc-diag */
     35:         for (j=0; j<lmbd->bdlen[d]; j++) {
     36:           if (!indices[j-diag]) ec++;
     37:           indices[j-diag] = 1;
     38:         }
     39:       }
     40:     }
     41:   } else {
     42:     for (d=0; d<lmbd->nd; d++) {
     43:       diag = lmbd->diag[d];
     44:       if (diag > 0) { /* col = loc */
     45:         for (j=0; j<lmbd->bdlen[d]; j++) {
     46:           if (!indices[bs*j]) ec += bs;
     47:           for (i=0; i<bs; i++) indices[bs*j+i] = 1;
     48:         }
     49:       } else { /* col = loc-diag */
     50:         for (j=0; j<lmbd->bdlen[d]; j++) {
     51:           if (!indices[bs*(j-diag)]) ec += bs;
     52:           for (i=0; i<bs; i++) indices[bs*(j-diag)+i] = 1;
     53:         }
     54:       }
     55:     }
     56:   }

     58:   /* form array of columns we need */
     59:   PetscMalloc((ec+1)*sizeof(PetscInt),&garray);
     60:   ec   = 0;
     61:   for (i=0; i<N; i++) {
     62:     if (indices[i]) garray[ec++] = i;
     63:   }
     64:   PetscFree(indices);

     66:   /* create local vector that is used to scatter into */
     67:   VecCreateSeq(PETSC_COMM_SELF,N,&mbd->lvec);

     69:   /* create temporary index set for building scatter-gather */
     70:   ISCreateGeneral(mat->comm,ec,garray,&from);
     71:   ISCreateGeneral(PETSC_COMM_SELF,ec,garray,&to);
     72:   PetscFree(garray);

     74:   /* create temporary global vector to generate scatter context */
     75:   /* this is inefficient, but otherwise we must do either
     76:      1) save garray until the first actual scatter when the vector is known or
     77:      2) have another way of generating a scatter context without a vector.*/
     78:   /*
     79:      This is not correct for a rectangular matrix mbd->m?
     80:   */
     81:   VecCreateMPI(mat->comm,mat->m,mat->N,&gvec);

     83:   /* generate the scatter context */
     84:   VecScatterCreate(gvec,from,mbd->lvec,to,&mbd->Mvctx);
     85:   PetscLogObjectParent(mat,mbd->Mvctx);
     86:   PetscLogObjectParent(mat,mbd->lvec);
     87:   PetscLogObjectParent(mat,to);
     88:   PetscLogObjectParent(mat,from);
     89:   PetscLogObjectParent(mat,gvec);

     91:   ISDestroy(to);
     92:   ISDestroy(from);
     93:   VecDestroy(gvec);
     94:   return(0);
     95: }