[petsc-users] wrong no of nonzeros

[Jed Brown]

Derek Gaston <friedmud at gmail.com> writes:

> I am changing the stencil of my preconditioning matrix in the middle of a
> solve a solve... and I'm running into this:

Can you PCReset() after changing the stencil?

The implementation of MatGetSubMatrices_MPIAIJ caches some intermediate
structures to speed up subsequent calls.  I'll grant that Mat should do
a better job of remembering what has changed so that it can
automatically invalidate caches in this case.  There are only two things
hard in computer science...
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