On Thu, 5 Aug 2010 00:21:13 -0500, Matthew Knepley <knepley at gmail.com> wrote: > If someone tells us, "I have a Stokes problem", we could search for 0 > diagonals and create the partition for FS.
I suppose this would work for some common cases, but there are lot of discretizations and pressure-dependent constitutive relations/boundary conditions that have nonzeros in the pressure block. I think some slip conditions can also produce zero or negative values in the momentum block. I'm not convinced that it's so much to ask people to provide an index set, considering that FieldSplit is a somewhat advanced thing anyway (based on sheer number of choices available, and (typical) sensitivity to those choices). Jed