On Tue, Aug 21, 2012 at 8:51 PM, Matthew Knepley <knepley at gmail.com> wrote:
> I thought we agreed in this thread that we were (for now) going with >> Matt's bastardized model of attaching the Schur null space to A11. Doesn't >> that mean that this hunk should also be reverted (and have a comment >> explaining this indirect effect)? >> > > For future reference, this was my bastardized model in 3.3, but in > petsc-dev I either > > a) attach them to IS on input, which works beautifully > > or > > b) Tell the DM about them > In either case, what happens when you switch back and forth between Schur and, e.g. multiplicative? Does that cause there to be a different IS or a different DM? I fear that by including the physics in the DM, we may be obligated to have a DMGetSchurComplement() (or, in the more general nonlinear language, DMEliminate()). Note that some mixed discretizations have sparse Schur complements and it could even make sense to implement a nonlinear smoother in the reduced space. -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.mcs.anl.gov/pipermail/petsc-dev/attachments/20120821/6013dbf5/attachment.html>