[petsc-users] Prometheus vs GAMG for elasticity/plasticity problems

[Jed Brown]

Thomas Gross <tgross at ilsb.tuwien.ac.at> writes:

> I have now compiled Petsc 3.2.0 with Prometheus and Petsc 3.4.3 with GAMG using the same compiler. Furthermore I am using the same MPI implementation for both runs. Still Prometheus is considerably faster (see attached log files).
>
> Prometheus:
> -ksp_type cg -pc_type prometheus -log_summary -ksp_monitor -ksp_view -options_left > Prometheus_Large_Log_New.txt
>
> Gamg:
> -ksp_type cg -pc_type gamg -pc_gamg_type agg -pc_gamg_agg_nsmooths 1 -log_summary -ksp_monitor -ksp_view -options_left -mg_levels_ksp_max_it 1 > GAMG_Large_max_it_log_New.txt
> -ksp_type cg -pc_type gamg -pc_gamg_type agg -pc_gamg_agg_nsmooths 1 -log_summary -ksp_monitor -ksp_view -options_left mg_levels_ksp_type richardson -mg_levels_pc_type sor > GAMG_Large_Rich_Log_New.txt

Can you add -mg_levels_ksp_max_it 1 to this last configuration?  I see a
lot of time in MatSOR.  We can actually speed that up slightly with some
extra caching, which may be worthwhile.

We're seeing a bit lower performance in MatMult with GAMG, perhaps
because we are not using block formats specialized for elasticity.

Mark, what else is different?  What does Prometheus do differently in
setup (not the bottleneck here, but I'm curious).
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