On Tue, Jun 12, 2012 at 3:35 PM, Barry Smith <bsmith at mcs.anl.gov> wrote:
> G-S and Shur complement type fieldsplit PCs almost always work right so > long as you have decent preconditioners for the original block(s). Often > you don't need much of anything to precondition the Schur complement. > Thomas, note that you'll need Schur or some surrogate preconditioner to deal with incompressibility. It'll be worth understanding fieldsplit variants while working with Navier-Stokes and Cahn-Hilliard separately. Once you understand how to "drive" fieldsplit on those systems separately, you can put them together. > > As I said before you can construct a preconditioner for the N.S. block > by again using a PCFIELDSPLIT on that (recursive use of PCs). > > Note that once you have defined your blocks (in the simple case if you > have all your degrees of freedom collocated (no staggered grid) just set > the Vec and Mat block size; otherwise you need to construct an IS that > defines each block) then experimenting is easy and can be done at the > command line without changing the code. > -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.mcs.anl.gov/pipermail/petsc-users/attachments/20120612/53a9de03/attachment.html>
