[petsc-dev] MatZeroRows(), MatZeroRowsIS() have new arguments

[Jed Brown]

On Wed, Oct 27, 2010 at 14:47, Barry Smith <bsmith at mcs.anl.gov> wrote:

> I've considered it but have not seen a specific need. Do you have examples
> where it really matters?


The natural one would be Dirichlet boundary conditions for
(non-Galerkin) geometric multigrid with either variable coefficients or
non-uniform mesh size.  I still prefer modifying the element matrices before
assembly (which also maintains symmetry), but if you want to use MatZeroRows
to impose the boundary condition, you would also need a non-constant
diagonal.

Jed
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