On Wed, Mar 20, 2013 at 5:14 PM, John Mousel <john.mousel at gmail.com> wrote:
> Can you comment on a GASM type approach to find a solution for the null > space? I notice that the null vectors that successfully make the true > residual drop are only complicated in a very thin band around the > interface. This band is easy to identify using a level set. Other than > that, the null space vector has a low frequency variation. My thought was > to break the matrix into two sub-matrices, and somehow apply GAMG as a > preconditioner on the far matrix, and ILU on the interface-adjacent matrix. > Is this dumb or a complete misunderstanding of GASM? What is the dimension of the null space? "Bootstrap AMG" might be applicable to your problem, but it has yet to be implemented in a library. It is still expensive to construct, but may be better than the alternatives (except that using a sane spatial discretization is still likely better). -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.mcs.anl.gov/pipermail/petsc-users/attachments/20130320/f4d51c36/attachment.html>
