On Fri, Feb 10, 2012 at 3:58 PM, Dmitry Karpeev <karpeev at mcs.anl.gov> wrote:
> > > On Fri, Feb 10, 2012 at 3:53 PM, Jed Brown <jedbrown at mcs.anl.gov> wrote: > >> On Fri, Feb 10, 2012 at 15:50, Dmitry Karpeev <karpeev at mcs.anl.gov>wrote: >> >>> Why not simply allow DM to return two matrices as SNES and KSP would >>> want anyway? >> >> >> How do you specify the reduced stencil to use for the preconditioning >> matrix? Maybe it wouldn't add too many more if statements to the current >> code which is already polluted with them. >> > > It seems to me that the sparsity pattern (and even the type of the > matrices) is up to the particular DM type, > so it is, in principle, opaque. DMDA can control it by manipulating > stencil width or widths, while FEM-oriented DM > types (e.g., libMesh) could control it via the element type, etc. The > generic DM interface doesn't have a way to specify > the sparsity pattern. As it should be, in my opinion. > This makes no sense to me unless the two matrices being returned have different sparsity patterns, and we have no good way for specifying that, or even a good rationale for doing it. Matt > Dmitry. > -- 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/20120210/78bd9499/attachment.html>