[petsc-users] Parallel vs. single processor

Jed Brown jedbrown at mcs.anl.gov
Mon Nov 12 10:31:27 CST 2012

Try (e.g., -pc_type gamg) and additive Schwarz. Also try using ASM as a

On Mon, Nov 12, 2012 at 10:21 AM, Rob Kunz <rfk102 at arl.psu.edu> wrote:

>  Hi:****
> I have a pressure based CFD code using PETSC for nearly SPD pressure
> equation.****
> PETSC default solver + preconditioner (GMRES+BJ for n-proc) is very
> reliable for me.****
> However I have a very tough bearing problem with extremely high aspect
> ratio cells and the 1-processor run works fine (GMRES+ILU0), but for
> nproc>1 the code does not converge.****
> Of course I can get the code to return identical 1-proc and 12-proc
> convergence histories if I choose a point preconditioner like Jacobi, but
> that kills the convergence of both.****
> Any recommendations?****
> Thanks
> Rob Kunz****
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