1 /*$Id: getcolv.c,v 1.18 2000/09/28 21:12:12 bsmith Exp bsmith $*/ 2 3 #include "src/mat/matimpl.h" /*I "petscmat.h" I*/ 4 5 #undef __FUNC__ 6 #define __FUNC__ "MatGetColumnVector" 7 /*@ 8 MatGetColumnVector - Gets the values from a given column of a matrix. 9 10 Not Collective 11 12 Input Parameters: 13 + A - the matrix 14 . yy - the vector 15 - c - the column requested (in global numbering) 16 17 Level: advanced 18 19 Contributed by: Denis Vanderstraeten 20 21 .keywords: matrix, column, get 22 23 .seealso: MatGetRow(), MatGetDiagonal() 24 25 @*/ 26 int MatGetColumnVector(Mat A,Vec yy,int col) 27 { 28 Scalar *y,*v,zero = 0.0; 29 int ierr,i,j,nz,*idx,N,Rs,Re,rs,re,size; 30 MPI_Comm comm; 31 32 PetscFunctionBegin; 33 PetscValidHeaderSpecific(A,MAT_COOKIE); 34 PetscValidHeaderSpecific(yy,VEC_COOKIE); 35 36 if (col < 0) SETERRQ1(1,"Requested negative column: %d",col); 37 ierr = MatGetSize(A,PETSC_NULL,&N);CHKERRQ(ierr); 38 if (col >= N) SETERRQ2(1,"Requested column %d larger than number columns in matrix %d",col,N); 39 40 ierr = MatGetOwnershipRange(A,&Rs,&Re);CHKERRQ(ierr); 41 42 ierr = PetscObjectGetComm((PetscObject)yy,&comm);CHKERRQ(ierr); 43 ierr = MPI_Comm_size(comm,&size);CHKERRQ(ierr); 44 ierr = VecGetOwnershipRange(yy,&rs,&re);CHKERRQ(ierr); 45 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); 46 47 ierr = VecSet(&zero,yy);CHKERRQ(ierr); 48 ierr = VecGetArray(yy,&y);CHKERRQ(ierr); 49 50 for (i=Rs; i<Re; i++) { 51 ierr = MatGetRow(A,i,&nz,&idx,&v);CHKERRQ(ierr); 52 if (nz && idx[0] <= col) { 53 /* 54 Should use faster search here 55 */ 56 for (j=0; j<nz; j++) { 57 if (idx[j] >= col) { 58 if (idx[j] == col) y[i-rs] = v[j]; 59 break; 60 } 61 } 62 } 63 ierr = MatRestoreRow(A,i,&nz,&idx,&v);CHKERRQ(ierr); 64 } 65 66 ierr = VecRestoreArray(yy,&y);CHKERRQ(ierr); 67 PetscFunctionReturn(0); 68 } 69