MatGetRowIJ#

Returns the compressed row storage i and j indices for the local rows of a sparse matrix

Synopsis#

#include "petscmat.h" 
PetscErrorCode MatGetRowIJ(Mat mat, PetscInt shift, PetscBool symmetric, PetscBool inodecompressed, PetscInt *n, const PetscInt *ia[], const PetscInt *ja[], PetscBool *done)

Collective

Input Parameters#

mat - the matrix
shift - 0 or 1 indicating we want the indices starting at 0 or 1
symmetric - PETSC_TRUE or PETSC_FALSE indicating the matrix data structure should be symmetrized
inodecompressed - PETSC_TRUE or PETSC_FALSE indicating if the nonzero structure of the inodes or the nonzero elements is wanted. For MATBAIJ matrices the compressed version is always used.

Output Parameters#

n - number of local rows in the (possibly compressed) matrix, use NULL if not needed
ia - the row pointers; that is ia[0] = 0, ia[row] = ia[row-1] + number of elements in that row of the matrix, use NULL if not needed
ja - the column indices, use NULL if not needed
done - indicates if the routine actually worked and returned appropriate ia[] and ja[] arrays; callers are responsible for handling the case when done == PETSC_FALSE and ia and ja are not set

Notes#

You CANNOT change any of the ia[] or ja[] values.

Use MatRestoreRowIJ() when you are finished accessing the ia[] and ja[] values.

Fortran Notes#

Use

    PetscInt, pointer :: ia(:),ja(:)
    call MatGetRowIJF90(mat,shift,symmetric,inodecompressed,n,ia,ja,done,ierr)
    ! Access the ith and jth entries via ia(i) and ja(j)

MatGetRowIJ() Fortran binding is deprecated (since PETSc 3.19), use MatGetRowIJF90()