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

[Vanella, Marcos (Fed)]

Hi Mark and Matt, I tried swapping the preconditioner to cholmod and also the hypre Boomer AMG. They work just fine for my case. I also got my hands on a machine with NVIDIA gpus in one of our AI clusters. I compiled PETSc to make use of cuda and cuda-enabled openmpi (with gcc).
I'm running the previous tests and want to also check some of the cuda enabled solvers. I was able to submit a case for the default Krylov solver with these runtime flags: -vec_type seqcuda -mat_type seqaijcusparse -pc_type cholesky -pc_factor_mat_solver_type cusparse. The case run to completion.

I guess my question now is how do I monitor (if there is a way) that the GPU is being used in the calculation, and any other stats? Also, which other solver combination using GPU would you recommend for me to try? Can we compile PETSc with the cuda enabled version for CHOLMOD and HYPRE?

Thank you for your help!
Marcos

________________________________
From: Matthew Knepley <knepley at gmail.com>
Sent: Monday, June 26, 2023 12:11 PM
To: Vanella, Marcos (Fed) <marcos.vanella at nist.gov>
Cc: Mark Adams <mfadams at lbl.gov>; 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

On Mon, Jun 26, 2023 at 12:08 PM Vanella, Marcos (Fed) via petsc-users <petsc-users at mcs.anl.gov<mailto:petsc-users at mcs.anl.gov>> wrote:
Than you Matt and Mark, I'll try your suggestions. To configure with hypre can I just use the --download-hypre configure line?

Yes,

  Thanks,

    Matt

That is what I did with suitesparse, very nice.
________________________________
From: Mark Adams <mfadams at lbl.gov<mailto:mfadams at lbl.gov>>
Sent: Monday, June 26, 2023 12:05 PM
To: Vanella, Marcos (Fed) <marcos.vanella at nist.gov<mailto:marcos.vanella at nist.gov>>
Cc: petsc-users at mcs.anl.gov<mailto:petsc-users at mcs.anl.gov> <petsc-users at mcs.anl.gov<mailto: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


--
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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