Ok, I just tried --enable-gpu-aware-mpi passed to Hypre,
Hypre_config.h defines now HYPRE_USING_GPU_AWARE_MPI 1 But still no D2D copy near MPI calls in ex46.c example. Probably an obvious thing I forgot during PETSc configure, but I don't see... 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 ________________________________ De : LEDAC Pierre Envoyé : dimanche 31 août 2025 19:13:36 À : Barry Smith Cc : petsc-users@mcs.anl.gov Objet : RE: [petsc-users] [MPI][GPU] Barry, It solved the unrecognized option but still exchanging MPI messages through the host. I switch to a simpler test case without reading a matrix (src/ksp/ksp/tutorials/ex46.c) but get the same behaviour. In the Nsys profile for ex46, the MPI synchronizations occurs during PCApply so now I am wondering if the issue is related to the fact than Hypre is not configured/enabled with MPI GPU-Aware in the PETSc build. I will give a try with --enable-gpu-aware-mpi passed to Hypre. Do you know an example in PETSc which specifically bench with/without Cuda-Aware enabled for MPI ? [cid:93d886d4-28ec-4b73-b602-3a559fffd435] 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 ________________________________ De : Barry Smith <bsm...@petsc.dev> Envoyé : dimanche 31 août 2025 16:33:38 À : LEDAC Pierre Cc : petsc-users@mcs.anl.gov Objet : Re: [petsc-users] [MPI][GPU] Ahh, that ex10.c is missing a VecSetFromOptions() call before the VecLoad() and friends. In contrast, the matrix has a MatSetFromOptions(). Can you try adding it to ex10.c and see if that resolves the problem with ex10.c (and may be a path forward for your code)? Barry On Aug 31, 2025, at 4:32 AM, LEDAC Pierre <pierre.le...@cea.fr> wrote: Yes, but was surprised it was not used, so I removed it (same for -vec_type mpicuda) mpirun -np 2 ./ex10 2 -f Matrix_3133717_rows_1_cpus.petsc -ksp_view -log_view -ksp_monitor -ksp_type cg -pc_type hypre -pc_hypre_type boomeramg -pc_hypre_boomeramg_strong_threshold 0.7 -mat_type aijcusparse -vec_type cuda ... WARNING! There are options you set that were not used! WARNING! could be spelling mistake, etc! There is one unused database option. It is: Option left: name:-vec_type value: cuda source: command lin 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 ________________________________ De : Barry Smith <bsm...@petsc.dev<mailto:bsm...@petsc.dev>> Envoyé : samedi 30 août 2025 21:47:07 À : LEDAC Pierre Cc : petsc-users@mcs.anl.gov<mailto:petsc-users@mcs.anl.gov> Objet : Re: [petsc-users] [MPI][GPU] Did you try the additional option -vec_type cuda with ex10.c ? On Aug 30, 2025, at 1:16 PM, LEDAC Pierre <pierre.le...@cea.fr<mailto:pierre.le...@cea.fr>> wrote: Hello, My code is built with PETSc 3.23+OpenMPI 4.1.6 (Cuda support enabled) and profling indicates that MPI communications are done between GPUs in all the code except PETSc part where D2H transfers occur. I reproduced the PETSc issue with the example under src/ksp/ksp/tutorials/ex10 on 2 MPI ranks. See output in ex10.log Also below the Nsys system profiling on ex10 with D2H and H2D copies before/after MPI calls. Thanks for your help, <pastedImage.png> 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 <ex10.log>
