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

[Vanella, Marcos (Fed)]

Than you Matt and Mark, I'll try your suggestions. To configure with hypre can I just use the --download-hypre configure line?
That is what I did with suitesparse, very nice.
________________________________
From: Mark Adams <mfadams at lbl.gov>
Sent: Monday, June 26, 2023 12:05 PM
To: Vanella, Marcos (Fed) <marcos.vanella at nist.gov>
Cc: petsc-users at mcs.anl.gov <petsc-users at mcs.anl.gov>
Subject: Re: [petsc-users] SOLVE + PC combination for 7 point stencil (unstructured) poisson solution

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<mailto: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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