[petsc-users] [GPU] Jacobi preconditioner

[Junchao Zhang]

Yes, MatGetDiagonal_SeqAIJCUSPARSE hasn't been implemented.  petsc/cuda and
petsc/kokkos backends are separate code.
If petsc/kokkos meet your needs, then just use them.  For petsc users, we
hope it will be just a difference of extra --download-kokkos
--download-kokkos-kernels in configuration.

--Junchao Zhang


On Mon, Jul 28, 2025 at 2:51 AM LEDAC Pierre <Pierre.LEDAC at cea.fr> wrote:

> Hello all,
>
>
> We are solving with PETSc a linear system updated every time step
> (constant stencil but coefficients changing).
>
>
> The matrix is preallocated once with MatSetPreallocationCOO() then filled
> each time step with MatSetValuesCOO() and we use device pointers for
> coo_i, coo_j, and coefficients values.
>
>
> It is working fine with a GMRES Ksp solver and PC Jacobi but we are
> surprised to see that every time step, during PCSetUp,
> MatGetDiagonal_SeqAIJ is called whereas the matrix is on the device.
> Looking at the API, it seems there is no MatGetDiagonal_SeqAIJCUSPARSE()
> but a MatGetDiagonal_SeqAIJKOKKOS().
>
>
> Does it mean we should use Kokkos backend in PETSc to have Jacobi
> preconditioner built directly on device ? Or I am doing something wrong ?
>
> NB: Gmres is running well on device.
>
>
> I could use -ksp_reuse_preconditioner to avoid Jacobi being recreated each
> solve on host but it increases significantly the number of iterations.
>
>
> Thanks,
>
>
>
>
>
> Pierre LEDAC
> Commissariat à l’énergie atomique et aux énergies alternatives
> Centre de SACLAY
> DES/ISAS/DM2S/SGLS/LCAN
> Bâtiment 451 – point courrier n°41
> F-91191 Gif-sur-Yvette
> +33 1 69 08 04 03
> +33 6 83 42 05 79
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.mcs.anl.gov/pipermail/petsc-users/attachments/20250728/9a982040/attachment-0001.html>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: pastedImage.png
Type: image/png
Size: 519712 bytes
Desc: not available
URL: <http://lists.mcs.anl.gov/pipermail/petsc-users/attachments/20250728/9a982040/attachment-0001.png>