On Wed, Apr 6, 2011 at 09:34, Thomas Witkowski < [email protected]> wrote:

I have not a very good overview of PETSc's internal matters, but wouldn't be it correct that MatGetBlockSize returns the number of nested matrices of a MatNest?

No, and it would not make sense to do so because that is semantically different information. We can add support for automatically detecting splits when MatNest is used, but it really is better to set the splits using PCFieldSplitSetIS() or by using DMComposite because then it will do the correct thing regardless of whether MatNest is used underneath.