Hello,I'm having trouble with getting the AMG preconditioners working. I tried all of them (gamg, ml, hypre-boomeramg), with varying degrees of "success":
- GAMG:CMD options: -ksp_rtol 1e-8 -ksp_monitor_true_residual -ksp_max_it 20 -ksp_type fgmres -pc_type gamg -pc_gamg_sym_graph TRUE -pc_gamg_agg_nsmooths 1 -ksp_view
always crashes with the following error: Error: error code 77[0] KSPSolve() line 780 in /home/yoda/wern_mc/Programme/Anaconda/envs/GSA_27/weitere_programme/petsc-3.10.0/src/ksp/ksp/interface/itfunc.c [0] KSPSolve_GMRES() line 233 in /home/yoda/wern_mc/Programme/Anaconda/envs/GSA_27/weitere_programme/petsc-3.10.0/src/ksp/ksp/impls/gmres/gmres.c [0] KSPInitialResidual() line 67 in /home/yoda/wern_mc/Programme/Anaconda/envs/GSA_27/weitere_programme/petsc-3.10.0/src/ksp/ksp/interface/itres.c [0] KSP_PCApply() line 281 in /home/yoda/wern_mc/Programme/Anaconda/envs/GSA_27/weitere_programme/petsc-3.10.0/include/petsc/private/kspimpl.h [0] PCApply() line 462 in /home/yoda/wern_mc/Programme/Anaconda/envs/GSA_27/weitere_programme/petsc-3.10.0/src/ksp/pc/interface/precon.c [0] PCApply_MG() line 377 in /home/yoda/wern_mc/Programme/Anaconda/envs/GSA_27/weitere_programme/petsc-3.10.0/src/ksp/pc/impls/mg/mg.c [0] PCMGMCycle_Private() line 20 in /home/yoda/wern_mc/Programme/Anaconda/envs/GSA_27/weitere_programme/petsc-3.10.0/src/ksp/pc/impls/mg/mg.c [0] KSPSolve() line 780 in /home/yoda/wern_mc/Programme/Anaconda/envs/GSA_27/weitere_programme/petsc-3.10.0/src/ksp/ksp/interface/itfunc.c [0] KSPSolve_Chebyshev() line 381 in /home/yoda/wern_mc/Programme/Anaconda/envs/GSA_27/weitere_programme/petsc-3.10.0/src/ksp/ksp/impls/cheby/cheby.c
[0] Petsc has generated inconsistent data [0] Eigen estimator failed: DIVERGED_NANORINF at iteration 0When I'm using a different solver for -mg_levels_ksp_type, such as gmres, GAMG no longer crashes, but I don't see convergence of the problem (convergence history and ksp_view output are attached below).
- HypreWith the default settings, BoomerAMG just returns a Vector of all zeros after one iteration. When I change the relaxation type -pc_hypre_boomeramg_relax_type_all to Jacobi, I get similar results than with GAMG: the solver works without errors, but doesn't converge. The output for Hypre is also attached below.
- MLWith default settings the result is just like Boomeramg: a vector of all zeros after one iteration. When I change -mg_levels_ksp_type the behaviour is identical to GAMG.
Since none of the packages worked, I'm assuming that the error lies with me/ my code, so I'll give a short overview over what I'm trying to do. The matrix I'm trying to precondition is the Jacobian of a flow field originating from an unstructured finite-volume CFD code. It has a blocked structure as each node of the original mesh holds several variables (pressure, density, velocities). However, I'm not using a DM-Plex since I get the assembled Jacobian in binary format from the external CFD code. When I'm using direct (lu) I get correct results, so the basic code should be fine. However, for larger problems lu is not feasible due the very large memory requirements, therefore I wanted to switch over to multigrid.
Currently, PETSc has no information about the original geometry. I tried using setCoordinates, but for Hypre and ml it didn't make a difference, and GAMG crashed with an error:
[0] PCSetCoordinates() line 1883 in /home/yoda/wern_mc/Programme/Anaconda/envs/GSA_27/weitere_programme/petsc-3.10.0/src/ksp/pc/interface/precon.c [0] PCSetCoordinates_AGG() line 199 in /home/yoda/wern_mc/Programme/Anaconda/envs/GSA_27/weitere_programme/petsc-3.10.0/src/ksp/pc/impls/gamg/agg.c
[0] Petsc has generated inconsistent data[0] Don't know how to create null space for ndm=2, ndf=4. Use MatSetNearNullSpace.
I would be glad if you could give me some advice on how to deal with this.
Kind regards, Michael
GAMG_KSP_view
Description: Binary data
Hypre_KSP_view
Description: Binary data
