Actual source code: getcolv.c
petsc-3.13.6 2020-09-29
Report Typos and Errors

      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: .seealso: MatGetRow(), MatGetDiagonal()

     28: @*/
     29: PetscErrorCode  MatGetColumnVector(Mat A,Vec yy,PetscInt col)
     30: {
     31:   PetscScalar       *y;
     32:   const PetscScalar *v;
     33:   PetscErrorCode    ierr;
     34:   PetscInt          i,j,nz,N,Rs,Re,rs,re;
     35:   const PetscInt    *idx;

     40:   if (col < 0) SETERRQ1(PETSC_COMM_SELF,PETSC_ERR_ARG_OUTOFRANGE,"Requested negative column: %D",col);
     41:   MatGetSize(A,NULL,&N);
     42:   if (col >= N) SETERRQ2(PETSC_COMM_SELF,PETSC_ERR_ARG_OUTOFRANGE,"Requested column %D larger than number columns in matrix %D",col,N);
     43:   MatGetOwnershipRange(A,&Rs,&Re);
     44:   VecGetOwnershipRange(yy,&rs,&re);
     45:   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);

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

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

     76: /*@
     77:     MatGetColumnNorms - Gets the norms of each column of a sparse or dense matrix.

     79:   Input Parameter:
     80: +  A - the matrix
     81: -  type - NORM_2, NORM_1 or NORM_INFINITY

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

     86:    Level: intermediate

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

     92: .seealso: NormType, MatNorm()

     94: @*/
     95: PetscErrorCode MatGetColumnNorms(Mat A,NormType type,PetscReal norms[])
     96: {

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