On Tue, Mar 15, 2011 at 6:09 PM, Barry Smith <bsmith at mcs.anl.gov> wrote:
> > On Mar 15, 2011, at 6:03 PM, Matthew Knepley wrote: > > > On Tue, Mar 15, 2011 at 6:00 PM, Jed Brown <jed at 59a2.org> wrote: > > On Tue, Mar 15, 2011 at 23:50, Matthew Knepley <knepley at gmail.com> > wrote: > > That is not what I have here. I want to change a portion, but outside of > that I want it to fall back to a global matrix. > > > > You were going to put your MatShell in the "pmat" slot, right? What are > you going to use for preconditioning the other blocks? If it's the same as > in "mat", you could use a MatNest for both operators and put the special > sauce in that slot of the "pmat". > > > > This is the same objection Barry has. I do not want this tied to a > particular matrix impl for the global matrix. > > But you are tying it to a MATSHELL, that is a particular impl > Only the precon thing is a MATSHELL, not my original matrix. The way Jed is saying to do it (I think) is to have my original matrix assembled as a MatNest. > Why not pass your Mat (maybe a global MPIAIJ) as the mat and pass your > MatNest as your pmat and have some of the subblocks in the MatNest be > defined by submatrices of of the MPIAIJ matrix. > > That is, introduce a new matrix class that contains a pointer to a big > matrix and two IS. The IS defines the part of the big matrix that this new > matrix object represent. In this way you can build your pmat as a MatNest > and put whatever stuff you want in some of its blocks but have the other > blocks be defined as parts of the original mat (which is the big assed AIJ > or anything else). That is what I have, without the MatNest (I do not see what it adds here). Matt > > > Barry > > > > > If you assemble the matrix entirely monolithically (using MatSetValues > globally instead of MatSetValuesLocal on each physics separately), then we > haven't written MatSetValues_Nest yet so maybe your MatShell is the right > idea. > > > > > > Related: What do people think about having MatGetSubMatrix() retain > ownership of the submatrix? > > > > Does it matter with our interface? Should be transparent. > > > > 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 > > -- 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/20110315/deba4456/attachment.html>
