[petsc-users] SOLVE + PC combination for 7 point stencil (unstructured) poisson solution

[Matthew Knepley]

On Mon, Jun 26, 2023 at 11:34 AM Vanella, Marcos (Fed) via petsc-users <
petsc-users at mcs.anl.gov> wrote:

> Hi, I was wondering if anyone has experience on what combinations are more
> efficient to solve a Poisson problem derived from a 7 point stencil on a
> single mesh (serial).
> I've been doing some tests of multigrid and cholesky on a 50^3 mesh. *-pc_type
> mg* takes about 75% more time than *-pc_type cholesky
> -pc_factor_mat_solver_type cholmod* for the case I'm testing.
> I'm new to PETSc so any suggestions are most welcome and appreciated,
>

Hmm, that does not match my experience. We can help look at it if you send
the output of

  -log_view -ksp_view -ksp_monitor_true_residual

for both cases. I would expect MG to start being faster above maybe 25-50K
unknowns.

  Thanks,

    Matt


> Marcos
>


-- 
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.cse.buffalo.edu/~knepley/>
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