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

[Mark Adams]

I'm not sure what MG is doing with an "unstructured" problem. I assume you
are not using DMDA.
-pc_type gamg should work
I would configure with hypre and try that also: -pc_type hypre

As Matt said MG should be faster. How many iterations was it taking?
Try a 100^3 and check that the iteration count does not change much, if at
all.

Mark


On Mon, Jun 26, 2023 at 11:35 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,
> Marcos
>
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