[petsc-users] PETSc-gamg default setting

[Barry Smith]

   Run with -ksp_view (or -snes_view etc). If that does not provide all relevant information then tell us what is missing so we can add that to the output. Defaults etc change over time so you should never rely on what someone thinks it is or what it “should be”, just run with the viewer.

   barry

On Apr 25, 2014, at 11:31 AM, Matthew Knepley <knepley at gmail.com> wrote:

> 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