[petsc-dev] ML Reuse redux

[John Fettig]

On Mon, Aug 29, 2011 at 12:16 PM, Jed Brown <jedbrown at mcs.anl.gov> wrote:
> Would you be willing to make this into a Mercurial patch against petsc-dev?
> Just commit your changes locally, hg export them, and send us the patch.

Here's the patch.  I left in the serial code that creates the matrices
in PETSc rather than letting ML take care of it, just in case you
wanted that for any reason.  One thing that I notice is that when I
use UMFPACK for the coarse grid solve, the preconditioner is different
(e.g. minres takes more iterations) when I do:

KSPSetOperators(gridctx[fine_level].ksp,gridctx[level].A,gridctx[fine_level].A,SAME_NONZERO_PATTERN);

versus

KSPSetOperators(gridctx[fine_level].ksp,gridctx[level].A,gridctx[fine_level].A,DIFFERENT_NONZERO_PATTERN);

This shouldn't be the case, should it?  It doesn't do this with the
PETSc builtin lu, so I suspect a bug in the UMFPACK interface.

John
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