[petsc-users] Load balancing problem with DMDA

[Matthew Knepley]

On Thu, Oct 15, 2015 at 8:55 AM, Xiao, Jianjun (IKET) <jianjun.xiao at kit.edu>
wrote:

> Matt,
>
>
> Yes. I would like to try. Where should I start?
>
I would take a small 2D problem that you care about and try to make an
equivalent Plex code to the DMDA code.

I think it will be slower than DMDA, but trying a simple thing does not
hurt.

I can make you a simple 2D lattice in Plex.

  Thanks,

    Matt



> ------------------------------
> *From:* Matthew Knepley <knepley at gmail.com>
> *Sent:* Thursday, October 15, 2015 3:43 PM
> *To:* Barry Smith
> *Cc:* Xiao, Jianjun (IKET); petsc-users at mcs.anl.gov
> *Subject:* Re: [petsc-users] Load balancing problem with DMDA
>
> 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
>



-- 
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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