On Mon, Dec 20, 2010 at 01:31, Barry Smith <bsmith at mcs.anl.gov> wrote:
> > 2. Is it as easy as PCSetDM? Or provide a coarse DM and get a > hierarchy? Is there an example? I agree about having FieldSplit forward the > pieces. I recall starting on that. Who is responsible for assembling > rediscretized coarse operators? > > src/ksp/ksp/examples/tutorials/ex45.c Neat, this does more than I thought. We currently pick up DMComposite and forward index sets and field names into the splits. Two issues remain 1. Forward DMs into splits. This is superficial, it pretty much just requires a non-vararg DMComposite accessor. It would be a massive simplification to create a DMRedundant instead of all the Array specialization in DMComposite. 2. What if the user wants to run PCMG in only one split? I think this one is actually hard. Suppose we have FormFunction1(dm1,X1,X2,F1,user1); FormFunction2(dm2,X1,X2,F2,user2); If we do monolithic multigrid, then we call both of these functions with (dm1,dm2) on each level and there is no conceptual difficulty relative to the single-level method. But if we only do multigrid on physics 2, then we still need a way to get X1 (interpolated into whatever form FormFunction2 needs) on coarse levels. If we want to call FormFunction2 from PCSetUp_FieldSplit:PCSetUp_MG, then we have lost all reference to X1. But handling all the MG stuff from PCSetUp_FieldSplit is breaking the abstraction. I'm not seeing an elegant way to handle this, perhaps we should have a way to cache coupling information on the DM. Any ideas? -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.mcs.anl.gov/pipermail/petsc-dev/attachments/20101221/6f340622/attachment.html>
