[petsc-users] PETSc-gamg default setting

[Matthew Knepley]

On Fri, Apr 25, 2014 at 11:26 AM, 藤井昭宏 <fujii at cc.kogakuin.ac.jp> wrote:

> Hello everybody,
>
> I’d like to compare a solver with PETSc-gamg for Poisson problems.
> I used PETSc version 3.4.3., and the following command line option.
>
>  -ksp_type “bcgs” -pc_type “gamg” -ksp_monitor -ksp_rtol 1.0E-7
> -log_summary -pc_mg_log
>
>
> Would you give me some information on the following questions?
>
> - Does this option correspond to BICGSTAB solver with smoothed aggregation
> algebraic multigrid method?
>

Yes


> - Are coarser level small distributed matrices re-distributed to reduce
> the parallelism, when the number of processes is very large?
>

Yes


> -  What kind of smoother will be used for this command line option?
>

Cheby(2)/Jacobi is the default in GAMG.


> -  pc_mg_log option shows the MG Apply stage. Does this stage time
> correspond to the solver time except for multi-level setup time?
>    Does it include the time for BICGSTAB?
>

Yes, and no.

 Thanks,

     Matt


> Thanks in advance.
>
> Akihiro Fujii
>
>




-- 
What most experimenters take for granted before they begin their
experiments is infinitely more interesting than any results to which their
experiments lead.
-- Norbert Wiener
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