Actual source code: getcolv.c
petsc-3.10.5 2019-03-28
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      2:  #include <petsc/private/matimpl.h>

      4: /*@
      5:    MatGetColumnVector - Gets the values from a given column of a matrix.

      7:    Not Collective

      9:    Input Parameters:
     10: +  A - the matrix
     11: .  yy - the vector
     12: -  col - the column requested (in global numbering)

     14:    Level: advanced

     16:    Notes:
     17:    Each processor for which this is called gets the values for its rows.

     19:    Since PETSc matrices are usually stored in compressed row format, this routine
     20:    will generally be slow.

     22:    The vector must have the same parallel row layout as the matrix.

     24:    Contributed by: Denis Vanderstraeten

     26: .keywords: matrix, column, get

     28: .seealso: MatGetRow(), MatGetDiagonal()

     30: @*/
     31: PetscErrorCode  MatGetColumnVector(Mat A,Vec yy,PetscInt col)
     32: {
     33:   PetscScalar       *y;
     34:   const PetscScalar *v;
     35:   PetscErrorCode    ierr;
     36:   PetscInt          i,j,nz,N,Rs,Re,rs,re;
     37:   const PetscInt    *idx;

     42:   if (col < 0) SETERRQ1(PETSC_COMM_SELF,PETSC_ERR_ARG_OUTOFRANGE,"Requested negative column: %D",col);
     43:   MatGetSize(A,NULL,&N);
     44:   if (col >= N) SETERRQ2(PETSC_COMM_SELF,PETSC_ERR_ARG_OUTOFRANGE,"Requested column %D larger than number columns in matrix %D",col,N);
     45:   MatGetOwnershipRange(A,&Rs,&Re);
     46:   VecGetOwnershipRange(yy,&rs,&re);
     47:   if (Rs != rs || Re != re) SETERRQ4(PETSC_COMM_SELF,PETSC_ERR_ARG_INCOMP,"Matrix %D %D does not have same ownership range (size) as vector %D %D",Rs,Re,rs,re);

     49:   if (A->ops->getcolumnvector) {
     50:     (*A->ops->getcolumnvector)(A,yy,col);
     51:   } else {
     52:     VecSet(yy,0.0);
     53:     VecGetArray(yy,&y);

     55:     for (i=Rs; i<Re; i++) {
     56:       MatGetRow(A,i,&nz,&idx,&v);
     57:       if (nz && idx[0] <= col) {
     58:         /*
     59:           Should use faster search here
     60:         */
     61:         for (j=0; j<nz; j++) {
     62:           if (idx[j] >= col) {
     63:             if (idx[j] == col) y[i-rs] = v[j];
     64:             break;
     65:           }
     66:         }
     67:       }
     68:       MatRestoreRow(A,i,&nz,&idx,&v);
     69:     }
     70:     VecRestoreArray(yy,&y);
     71:   }
     72:   return(0);
     73: }

     78: /*@
     79:     MatGetColumnNorms - Gets the norms of each column of a sparse or dense matrix.

     81:   Input Parameter:
     82: +  A - the matrix
     83: -  type - NORM_2, NORM_1 or NORM_INFINITY

     85:   Output Parameter:
     86: .  norms - an array as large as the TOTAL number of columns in the matrix

     88:    Level: intermediate

     90:    Notes:
     91:     Each process has ALL the column norms after the call. Because of the way this is computed each process gets all the values,
     92:     if each process wants only some of the values it should extract the ones it wants from the array.

     94: .seealso: NormType, MatNorm()

     96: @*/
     97: PetscErrorCode MatGetColumnNorms(Mat A,NormType type,PetscReal norms[])
     98: {

    103:   if (A->ops->getcolumnnorms) {
    104:     (*A->ops->getcolumnnorms)(A,type,norms);
    105:   } else SETERRQ(PetscObjectComm((PetscObject)A),PETSC_ERR_SUP,"Not coded for this matrix type");
    106:   return(0);
    107: }