On 11 Sep 2015, at 17:05, Eike Mueller <E.Mueller@bath.ac.uk> wrote:
Dear firedrakers (and Colin),
is there an easy way of building a PETSc-based block-Jacobi preconditioner for a mixed system in firedrake? So if I have the mixed system in velocity, buoyancy, pressure, can I tell PETSc that the dofs in one vertical column belong together, i.e. the full vector has a block-structure, and then use a block-Jacobi preconditioner? Or does that make no sense if I have a horizontally continuous space?
Block Jacobi is a broad church, can you describe what you mean in more detail? Do you want to use a block diagonal preconditioner where the blocks are the three variables. Or do you want to decouple into columns and invert all the variables in the same column simultaneously. Or something else? Cheers, Lawrence