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

[Sanjay Govindjee]

Thomas,

   It looks like you are asking FEAP to solve the equations multiples 
times.  Perhaps you have a nonlinear problem with a Newton loop?

   This is not a fair comparison. Edit your run script to only perform 1 
(one) solve "tang,,1" (No Newton loops), then compare.

-sg

On 1/27/14 9:48 AM, Thomas Gross wrote:
> 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
>
>
>
>
> 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.

-- 
-----------------------------------------------
Sanjay Govindjee, PhD, PE
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