[petsc-users] How to use multigrid?

[Mark F. Adams]

On Nov 9, 2012, at 10:05 AM, w_ang_temp <w_ang_temp at 163.com> wrote:

> Hello,Jed
>    
>     Sorry again for the interruption.
>     
>     As you said, if I want to use Algebraic multigrid, I can just use '-pc_type gamg
> -pc_gamg_agg_nsmooths 1' in the command line. I think there are many other -pc_gamg_XXX
> parameters. How can I find all the -pc_gamg_XXX? 

-help

>     
>     Besides, I want to know more about AMG. Are there any details from PETSc, like manual,
> documentaion, FAQ, etc?

I would recommend the book "Multigrid" by Trottenberg, et al, and the classic "Multigrid Tutorial" is good to look at also.

>     Also, from the above post, I want to know that if AMG can not be used in 3.2 by command
> line option, because now I have to use 3.3 for using AMG. I just donot want to change my
> version 3.2 now.

You can use 3.2 if you like (free country) but this code was developed a lot between 3.2 and 3.3.  I forget what was in 3.2 exactly.  If you have a straight forward problem and 3.2 works then its is probably OK for your current purposes.

>     
>     I am major in Civil Engineering and not good at math and programming. So please
> forgive my weakness.
>     Thanks.
>                                 Jim 
>  
> 
> 
> 
> 
> 
> >At 2012-10-28 21:17:00,"Jed Brown" <jedbrown at mcs.anl.gov> wrote:
> >Algebraic multigrid can be used directly, -pc_type gamg -pc_gamg_agg_nsmooths 1. Geometric either required that you use the PCMG interface to set >interpolation (and provide a coarse operator for non-Galerkin) or use a DM that provides coarsening capability.
> 
> >What kind of problem are you solving?
> 
> >>On Oct 28, 2012 6:09 AM, "w_ang_temp" <w_ang_temp at 163.com> wrote:
> >>Hello,
>  >>  I want to use the multigrid as a preconditioner. The introduction about it in the manual is little.
> >>So are there some typical examples or details about multigrid? Is it used just like other preconditioners
> >>like jacobi, sor, which can be simply used in the cammand line options?
>  >>  Thanks.
>  > >                                                                     Jim
> 
> 
> 
> 

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