Could you try petsc/main to see if the problem persists? --Junchao Zhang
On Mon, Sep 16, 2024 at 10:51 AM LEDAC Pierre <pierre.le...@cea.fr> wrote: > Hi all, > > > We are using PETSc 3.20 in our code and running succesfully several > solvers on Nvidia GPU with OpenMPI library which are not GPU aware (so I > need to add the flag -use_gpu_aware_mpi 0). > > > But now, when using OpenMPI GPU Aware library (OpenMPI 4.0.5 ou 4.1.5 from > NVHPC), some parallel calculations failed with *KSP_DIVERGED_ITS* or > *KSP_DIVERGED_DTOL* > > with several configurations. It may run wells on a small test case with > (matrix is symmetric): > > > *-ksp_type cg -pc_type gamg -pc_gamg_type classical* > > > But suddenly with a number of devices for instance bigger than 4 or 8, it > may fail. > > > If I switch to another solver (BiCGstab), it may converge: > > > *-ksp_type bcgs -pc_type gamg -pc_gamg_type classical* > > > The more sensitive cases where it diverges are the following: > > > *-ksp_type cg -pc_type hypre -pc_hypre_type boomeramg * > > *-ksp_type cg -pc_type gamg -pc_gamg_type classical* > > > And the *bcgs* turnaroud doesn't work each time... > > > It seems to work without problem with aggregation (at least 128 GPUs on my > simulation): > > *-ksp_type cg -pc_type gamg -pc_gamg_type agg* > > > So I guess there is a weird thing happening in my code during the solve in > PETSc with MPI GPU Aware, as all the previous configurations works with non > GPU aware MPI. > > > Here is the -ksp_view log during one fail with the first configuration: > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > *KSP Object: () 8 MPI processes type: cg maximum iterations=10000, > nonzero initial guess tolerances: relative=0., absolute=0.0001, > divergence=10000. left preconditioning using UNPRECONDITIONED norm type > for convergence test PC Object: () 8 MPI processes type: hypre HYPRE > BoomerAMG preconditioning Cycle type V Maximum number of levels > 25 Maximum number of iterations PER hypre call 1 Convergence > tolerance PER hypre call 0. Threshold for strong coupling 0.7 > Interpolation truncation factor 0. Interpolation: max elements per > row 0 Number of levels of aggressive coarsening 0 Number of > paths for aggressive coarsening 1 Maximum row sums 0.9 Sweeps > down 1 Sweeps up 1 Sweeps on coarse 1 > Relax down l1scaled-Jacobi Relax up > l1scaled-Jacobi Relax on coarse Gaussian-elimination Relax > weight (all) 1. Outer relax weight (all) 1. Maximum size > of coarsest grid 9 Minimum size of coarsest grid 1 Not using > CF-relaxation Not using more complex smoothers. Measure > type local Coarsen type PMIS Interpolation type > ext+i SpGEMM type cusparse linear system matrix = precond > matrix: Mat Object: () 8 MPI processes type: mpiaijcusparse > rows=64000, cols=64000 total: nonzeros=311040, allocated > nonzeros=311040 total number of mallocs used during MatSetValues > calls=0 not using I-node (on process 0) routines* > > > I didn't succeed for the moment creating a reproducer with ex.c examples... > > > Did you see this kind of behaviour before? > > Should I update my PETSc version ? > > > Thanks for any advice, > > > Pierre LEDAC > Commissariat à l’énergie atomique et aux énergies alternatives > Centre de SACLAY > DES/ISAS/DM2S/SGLS/LCAN > Bâtiment 451 – point courrier n°43 > F-91191 Gif-sur-Yvette > +33 1 69 08 04 03 > +33 6 83 42 05 79 >
