[petsc-users] How rto use multigrid?

[TAY wee-beng]

On 30/10/2012 1:44 PM, Matthew Knepley wrote:
> On Tue, Oct 30, 2012 at 7:41 AM, TAY wee-beng <zonexo at gmail.com 
> <mailto:zonexo at gmail.com>> wrote:
>
>     On 28/10/2012 2:17 PM, Jed Brown 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?
>>
>
>     Hi,
>
>     May I know if there is an example which explains using the
>     geometric MG, either using PCMG or DM?
>
>
> SNES ex5 and ex19 both use MG.
>
>    Matt
Are there examples which uses ksp and geometric MG? I want to solve a 
Poisson eqn which has been discretized to give a sys of linear eqns.

I also found this thread :

http://lists.mcs.anl.gov/pipermail/petsc-users/2012-August/015073.html

Is it using geometric MG to solve a sys of linear eqns?
>
>     Yours sincerely,
>
>     TAY wee-beng
>
>
>>     On Oct 28, 2012 6:09 AM, "w_ang_temp" <w_ang_temp at 163.com
>>     <mailto: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
>>
>>
>
>
>
>
> -- 
> 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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