On Tue, Jan 10, 2012 at 03:45, Thomas Witkowski < Thomas.Witkowski at tu-dresden.de> wrote:
> I'm about to implement the multigrid preconditioner for my FEM code for > the case of regulare 2D triangular meshes. My meshes have a union jack > pattern, thus the nodes are equidistributed in both directions but the > stencil varies between a 9-point and a 5-point stencil. Is it possible to > fit this into the DMDA framework? It's not easy to make DMCreateMatrix() preallocate for this arrangement, but you can overallocate (all 9-point), use http://www.mcs.anl.gov/petsc/petsc-current/docs/manualpages/DM/DMSetMatrixPreallocateOnly.html and then assemble what you have. The resulting matrix will be compacted so that the used part is contiguous, so the run-time performance will be the same as with perfect preallocation (but needed to allocate slightly more memory). -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.mcs.anl.gov/pipermail/petsc-users/attachments/20120110/1b502a95/attachment.htm>
