[petsc-users] Load balancing problem with DMDA

[Matthew Knepley]

On Wed, Oct 14, 2015 at 3:32 PM, Barry Smith <bsmith at mcs.anl.gov> wrote:

>
> > On Oct 14, 2015, at 3:11 PM, Xiao, Jianjun (IKET) <jianjun.xiao at kit.edu>
> wrote:
> >
> > Hello,
> >
> > We have a finite volume code with structured grid. We use the DMDA data
> structure.
> >
> > Now we have the load balancing problem as shown in the attached picture.
> The domain is decomposed into 4 partitions. The sub-domain in black (proc
> 2) is solid which is of no interest. We would like to calculate only the
> fluid part in proc 1, 3 and 4 which means the resource in proc 2 is wasted.
> Does DMDA now support multi-block with communication between blocks? I mean
> I build block 1 and assign to proc1, block 2 to proc 3 and block 3 to proc
> 4. So the solid sub-domain does not exist. Any suggestion?
>
> No
>
> >
> > Or I have to do it using DMPLEX? Since data structure of the whole code
> is based on  DMDA, is there any "simple way" to switch from DMDA to DMPLEX
> without changing the loop structure in the code?
>
>   No
>
>   DMDA is for simple structured grids.


Using Plex would be some work since no one has ever used it to do FD. In
fact, now I think the way to do this
is to only represent the vertices and edges. I would help you if you want
to experiment with that.

  Thanks,

     Matt


>
> >
> > Thank you.
> >
> > Best regards
> > Jianjun
> > <pic.JPG>
>
>


-- 
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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