On Sun, Mar 18, 2012 at 18:55, Matthew Knepley <[email protected]> wrote:

No off-diagonal.

So I think the MatGetArray() should be MatDenseGetArray() because it's not directly useful otherwise. For in-place modification (if that is actually useful), I'd do it with a callback. Note that for your specific purpose, you can do in-place modification with MatMPIAIJGetAIJ() and MatGetArray() on each off-diagonal block.