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

[Thomas Gross]

I ran it with:
-ksp_type cg -pc_type gamg -pc_gamg_type agg -log_summary -ksp_monitor -ksp_view -options_left -mg_levels_ksp_max_it 1 > GAMG_log_max_it.txt
and
-ksp_type cg -pc_type gamg -pc_gamg_type agg -log_summary -ksp_monitor -ksp_view -options_left -mg_levels_ksp_type richardson -mg_levels_pc_type sor > GAMG_log_Rich.txt
(Log files attached)

However, the solution time did not decrease and I still needed to call KSPSolve 3 times although I had -mg_levels_ksp_max_it 1. 

Best
Thomas

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On Jan 27, 2014, at 5:53 PM, Jed Brown <jed at jedbrown.org> wrote:

> Thomas Gross <tgross at ilsb.tuwien.ac.at> writes:
> 
>> Please find enclosed the log summary for the runs.
>> 
>> I used the following options for Prometheus and GAMG:
>> Prometheus:
>> -ksp_type cg -pc_type prometheus -log_summary -ksp_monitor -ksp_view -aggmg_smooths 1 -options_left
>> GAMG:
>> -ksp_type cg -pc_type gamg -pc_gamg_type agg -pc_gamg_agg_nsmooths 1 -log_summary -ksp_monitor -ksp_view -options_left
> 
> This is a pretty small problem, but switch back to a single smoothing
> iteration -mg_levels_ksp_max_it 1.  An alternative is
> -mg_levels_ksp_type richardson -mg_levels_pc_type sor.
> 
> Note that you are calling KSPSolve 3 times with GAMG, but only once with
> Prometheus.