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: }