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:    If a Mat type does not implement the operation, each processor for which this is called
 18:    gets the values for its rows using MatGetRow().

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

 22:    Contributed by: Denis Vanderstraeten

 24: .seealso: MatGetRow(), MatGetDiagonal(), MatMult()

 26: @*/
 27: PetscErrorCode  MatGetColumnVector(Mat A,Vec yy,PetscInt col)
 28: {
 29:   PetscScalar       *y;
 30:   const PetscScalar *v;
 31:   PetscErrorCode    ierr;
 32:   PetscInt          i,j,nz,N,Rs,Re,rs,re;
 33:   const PetscInt    *idx;

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

 46:   if (A->ops->getcolumnvector) {
 47:     (*A->ops->getcolumnvector)(A,yy,col);
 48:   } else {
 49:     VecSet(yy,0.0);
 50:     VecGetArray(yy,&y);
 51:     /* TODO for general matrices */
 52:     for (i=Rs; i<Re; i++) {
 53:       MatGetRow(A,i,&nz,&idx,&v);
 54:       if (nz && idx[0] <= col) {
 55:         /*
 56:           Should use faster search here
 57:         */
 58:         for (j=0; j<nz; j++) {
 59:           if (idx[j] >= col) {
 60:             if (idx[j] == col) y[i-rs] = v[j];
 61:             break;
 62:           }
 63:         }
 64:       }
 65:       MatRestoreRow(A,i,&nz,&idx,&v);
 66:     }
 67:     VecRestoreArray(yy,&y);
 68:   }
 69:   return(0);
 70: }

 72: /*@
 73:     MatGetColumnNorms - Gets the norms of each column of a sparse or dense matrix.

 75:   Input Parameter:
 76: +  A - the matrix
 77: -  type - NORM_2, NORM_1 or NORM_INFINITY

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

 82:    Level: intermediate

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

 88: .seealso: NormType, MatNorm()

 90: @*/
 91: PetscErrorCode MatGetColumnNorms(Mat A,NormType type,PetscReal norms[])
 92: {

 97:   if (A->ops->getcolumnnorms) {
 98:     (*A->ops->getcolumnnorms)(A,type,norms);
 99:   } else SETERRQ(PetscObjectComm((PetscObject)A),PETSC_ERR_SUP,"Not coded for this matrix type");
100:   return(0);
101: }