Actual source code: getcolv.c
1: /*$Id: getcolv.c,v 1.23 2001/08/08 15:47:19 bsmith Exp $*/
3: #include src/mat/matimpl.h
5: /*@
6: MatGetColumnVector - Gets the values from a given column of a matrix.
8: Not Collective
10: Input Parameters:
11: + A - the matrix
12: . yy - the vector
13: - c - the column requested (in global numbering)
15: Level: advanced
17: Notes:
18: Each processor for which this is called gets the values for its rows.
20: Since PETSc matrices are usually stored in compressed row format, this routine
21: will generally be slow.
23: The vector must have the same parallel row layout as the matrix.
25: Contributed by: Denis Vanderstraeten
27: .keywords: matrix, column, get
29: .seealso: MatGetRow(), MatGetDiagonal()
31: @*/
32: int MatGetColumnVector(Mat A,Vec yy,int col)
33: {
34: PetscScalar *y,*v,zero = 0.0;
35: int ierr,i,j,nz,*idx,N,Rs,Re,rs,re;
36: MPI_Comm comm;
37:
42: if (col < 0) SETERRQ1(1,"Requested negative column: %d",col);
43: MatGetSize(A,PETSC_NULL,&N);
44: if (col >= N) SETERRQ2(1,"Requested column %d larger than number columns in matrix %d",col,N);
46: MatGetOwnershipRange(A,&Rs,&Re);
48: PetscObjectGetComm((PetscObject)yy,&comm);
49: VecGetOwnershipRange(yy,&rs,&re);
50: if (Rs != rs || Re != re) SETERRQ4(1,"Matrix %d %d does not have same ownership range (size) as vector %d %d",Rs,Re,rs,re);
52: VecSet(&zero,yy);
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: }
71: VecRestoreArray(yy,&y);
72: return(0);
73: }