[petsc-users] [petsc-maint] two-level Schwarz

Matthew Knepley knepley at gmail.com
Sat Mar 17 06:28:59 CDT 2018

On Fri, Mar 16, 2018 at 11:35 PM, John <johnlucassaturday at gmail.com> wrote:

> Hi PETSc team:
> I am curious if the two-level Schwarz preconditioner, as is illustrated in
> R. Tuminaro's paper ``on a multilevel preconditioning module for
> unstructured mesh Krylov solvers: two-level Schwarz", is readily available
> from command line options?

Hopefully I understand from my quick look at the paper. It looks like 2
levels MG, using DD as the smoother for the fine grid:

  -pc_type mg -pc_mg_nlevels 2 -pc_mg_galerkin
    -mg_levels_pc_type asm

The coarse grid will automatically be LU as in the paper. You can use
PCTELESCOPE to move the coarse grid to a subset
of processes or one process (PCREDUNDANT also works here). You do not have
to use Galerkin projection, but could
rediscretize on the coarse grid.



> Thanks,
> John

What most experimenters take for granted before they begin their
experiments is infinitely more interesting than any results to which their
experiments lead.
-- Norbert Wiener

https://www.cse.buffalo.edu/~knepley/ <http://www.caam.rice.edu/~mk51/>
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