Jed Brown wrote: > On Wed, Apr 6, 2011 at 09:34, Thomas Witkowski > <thomas.witkowski at tu-dresden.de > <mailto:thomas.witkowski at tu-dresden.de>> 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. This brings me back to the starting point of my current problem: how to set splits for MatNest correctly? PCFieldSplitSetFields seems not to work in my case. When I want to make use of PCFieldSplitSetIS for splitting MatNest, which indices should I provide? The MatNest I've created consists of the to main diagonal blocks with indices 0 to n and 0 to m. I'm not sure which index sets must be provided for PCFieldSplitSetIS.
Thomas
