question on DMMG

Randall Mackie randy at
Tue Oct 10 19:28:34 CDT 2006


If I use DMMGSetUseGalerkinCoarse, then do I need DMMGSetKsp, and
where do you set up the finest level grid matrix and right hand


Barry Smith wrote:
>   Randy,
>      Take a look at src/ksp/ksp/examples/tutorials and
> DASetCoordinates(). 
>     You should do it all with a DMMG and then it should be
> pretty easy.
>    Barry
> Note also: if you do not want to compute coarse matrices
> you can use DMMGSetGalerkin() or -dmmg_galerkin and have
> PETSc compute them.
> On Tue, 10 Oct 2006, Randall Mackie wrote:
>> I'm interested in trying to use multi-grid techniques to solve my problem,
>> but it's unclear to me how to define the right-hand side and system matrix
>> for my case where the grids are not uniform (ie, the grid lengths x,y,z are
>> variable, and the grid properties are variable).
>> Right now I'm solving my equations using a DA. So, on the finest scale I know
>> how to compute the RHS and the Jacobian. It's unclear to me how PETSc
>> does the multi-gridding, and therefore how I would write my code.
>> Any pointers would be appreciated.
>> Thanks, Randy

Randall Mackie
PMB# 643
2261 Market St.,
San Francisco, CA 94114-1600
Tel (415) 469-8649
Fax (415) 469-5044

California Registered Geophysicist
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