On Mon, Feb 4, 2013 at 3:44 PM, Derek Gaston <fried...@gmail.com> wrote:
> After updating to Petsc 3.3 (and the new libMesh... so it's not clear
> where the error is). One of our fancier preconditioning routines that
> relies on matrices added using system.add_matrix() calls is failing when we
> try to apply the preconditioner with an error that says:
>
> [0]PETSC ERROR: PCSetOperators() line 1049 in
> src/ksp/pc/interface/precon.c Cannot change local size of Amat after use
> old sizes 9 9 new sizes 25 25
>
> This is in an adaptivity problem that starts out with 2x2 quads (hence the
> 9x9 nature of the original matrix) and is being adapted (25x25 sounds
> right).
>
> Anyone seen this before? Is this some new checking in PETSc that is
> getting tripped...
>
PETSc has never supported changing the system size arbitrarily, but if you
set the matrix and changed it _before_ setting up the preconditioner, you
would have been okay in the past. We likely added the check when we added
PCReset (and KSPReset, etc). This tells PETSc to rebuild any size-dependent
structures, but does not change configuration. If you call this before
setting a new operator with different sizes, you should be fine.
If the code worked before, perhaps you never used the PC to solve a smaller
system before calling PCSetOperators() with a new system.
> or is libMesh possibly not resizing these matrices correctly?
>
> I'll provide more information as I have it... I just thought I would see
> if anyone had run into this before I get too deep in here...
>
> Derek
>
>
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