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

[Thomas Gross]

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

> Make sure to use the same smoother you used with Prometheus.
How can I make sure, that the same smoothing is applied in both cases?

Many thanks and best regards,
Thomas



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On Jan 27, 2014, at 4:34 PM, Jed Brown <jed at jedbrown.org> wrote:

> Thomas Gross <tgross at ilsb.tuwien.ac.at> writes:
> 
>> Dear petsc users/developers,
>> 
>> I am using petsc in a parallel FEAP framework (http://www.ce.berkeley.edu/projects/feap/) for mechanics oriented problems (mainly linear elasticity or plasticity).
>> In earlier petsc versions (3.2.7) I always used the petsc options:
>> -ksp_type cg -pc_type prometheus (with standard settings) and achieved a great level of performance.
>> 
>> After updating to petsc 3.4.3, where the ?Prometheus? preconditioner was replaced by ?GAMG?, I can not reach the same level of performance. My settings are:
>> -ksp_type cg -pc_type gamg -pc_gamg_type agg -pc_gamg_agg_nsmooths 1 (settings recommended for FEAP).
>> 
>> Is there a set of GAMG settings, which are equivalent to the standard Prometheus settings?
> 
> Please send -log_summary -ksp_monitor -ksp_view output for both cases.
> Make sure to use the same smoother you used with Prometheus.