[petsc-users] MatEqual and explicit zero behaviour

[Jørgen Kvalsvik]

Hi,

I was unable to find this in the PETSc docs nor any relevant example 
through search engines.

I have two matrices, A and B.

A:
PetscScalar values[] = {
10.0, 0, 0, 0, 0, 5.72,
0.2, 0, 0, 0, 0, 0,
0, 0, 4.2, 0, 0, 0,
0, 0, 0, 3.4, 0, 0,
0, 0, 3.14, 0, 0, 0,
0, 0, 0, 0, 0, 0 };

And an array [0..6] passed to both row and columns in my MatSetValues call.
err = MatSetValues( A,
       6, indices,
       6, indices,
       values, INSERT_VALUES );

B is constructed from CSR:
PetscInt csr_rows[] = { 0, 2, 3, 4, 5, 6, 6 };
PetscInt csr_cols[] = { 0, 5, 0, 2, 3, 2 };
PetscScalar csr_vals[] = { 10.0, 5.72, 0.2, 4.2, 3.4, 3.14 };

for( int i = 0; i < rows - 1; ++i ) {
     PetscInt row_entries = csr_rows[ i + 1 ] - csr_rows[ i ];

     PetscInt row_index[] = { i };
     PetscInt offset = csr_rows[ i ];

     err = MatSetValues( A,
           1, row_index,
           row_entries, csr_cols + offset,
           csr_vals + offset, INSERT_VALUES );
}

Printing them with PetscView gives:

A:
Matrix Object: 1 MPI processes
   type: seqaij
row 0: (0, 10)  (1, 0)  (2, 0)  (3, 0)  (4, 0)  (5, 5.72)
row 1: (0, 0.2)  (1, 0)  (2, 0)  (3, 0)  (4, 0)  (5, 0)
row 2: (0, 0)  (1, 0)  (2, 4.2)  (3, 0)  (4, 0)  (5, 0)
row 3: (0, 0)  (1, 0)  (2, 0)  (3, 3.4)  (4, 0)  (5, 0)
row 4: (0, 0)  (1, 0)  (2, 3.14)  (3, 0)  (4, 0)  (5, 0)
row 5: (0, 0)  (1, 0)  (2, 0)  (3, 0)  (4, 0)  (5, 0)

B:
Matrix Object: 1 MPI processes
   type: seqaij
row 0: (0, 10)  (5, 5.72)
row 1: (0, 0.2)
row 2: (2, 4.2)
row 3: (3, 3.4)
row 4: (2, 3.14)
row 5:

Which, as far as I can tell, are identical matrices.

But here's the problem. When I compare them with MatEqual it gives me 
false, which I did not expect. Is there some undocumented behaviour 
regarding explicit and implicit zeroes, and is this intentional? Is it 
not possible to compare matrices with different structures?

Thanks