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

[Thomas Gross]

Please find enclosed the output for GAMG using  -mg_levels_ksp_max_it 1:

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_type richardson -mg_levels_pc_type sor -mg_levels_ksp_max_it 1 >GAMG_Rich_max_it.txt

Best regards,
Thomas

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On Jan 30, 2014, at 2:14 AM, Jed Brown <jed at jedbrown.org> wrote:

> 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).