On Tue, Aug 21, 2012 at 8:59 PM, Jed Brown <jedbrown at mcs.anl.gov> wrote:
> 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? > You are right, it has the same conceptual flaw. > 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. > I really do not want to do that, at least not now since we have not even shaken out all the FS implications or have a library of common split PCs, nor have we gotten nonlinear FS working. After that, we can do DMEliminate(), if DM still exists. Matt -- What most experimenters take for granted before they begin their experiments is infinitely more interesting than any results to which their experiments lead. -- Norbert Wiener -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.mcs.anl.gov/pipermail/petsc-dev/attachments/20120821/d966569e/attachment.html>