[petsc-users] DMPlexDistributeField

[Matthew Knepley]

On Sun, Jul 7, 2019 at 8:48 PM Matthew Knepley <knepley at gmail.com> wrote:

> On Sun, Jul 7, 2019 at 8:37 PM Adrian Croucher <a.croucher at auckland.ac.nz>
> wrote:
>
>> hi Matt,
>> On 29/06/19 12:07 AM, Matthew Knepley wrote:
>>
>>
>> Okay, I ran through this. I am attaching my C version which was easier
>> for me to play with in the debugger, but it should not be
>> hard to put the few lines into yours. The problem comes from using
>> overlap in the redistribution. You can see this by running
>>
>>   mpiexec -n 2 ./distgeom2 -overlap 1 -overlap2 0
>>
>> which works fine. If overlap2 is 1, then the face data is shifted.
>>
>>
>> Yes, that's the same thing I found.
>>
>> Something in DistributeField() does not know that we changed
>> the topology after we distributed by adding overlap cells. This is
>> strange since DMPlexMigrate() works on the coordinates for
>> the overlapped mesh, however they always start at 0 in the vector, so it
>> must be that some offset is missing. I am looking for it now.
>>
>>
>> It looked to me like the problem might lie not in DMPlexDistributeField()
>> but in DMPlexDistribute(), because if you view the redistribution SF coming
>> out of the second call to DMPlexDistribute() it looks wrong.
>>
>> DMPlexDistributeField() appeared to be doing what it was told, but the SF
>> it was given didn't look right to me.
>>
>> True. I fixed it, but I am just getting the PR in order. Should have it
> tomorrow morning.
>

Sorry this took so long. I put in a PR for this:


https://bitbucket.org/petsc/petsc/pull-requests/1858/knepley-fix-plex-distribute-overlap/diff

I think it fixes your problem.

  Thanks,

     Matt


>    Thanks,
>
>       Matt
>
>> - Adrian
>>
>> --
>> Dr Adrian Croucher
>> Senior Research Fellow
>> Department of Engineering Science
>> University of Auckland, New Zealand
>> email: a.croucher at auckland.ac.nz
>> tel: +64 (0)9 923 4611
>>
>>
>
> --
> 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
>
> https://www.cse.buffalo.edu/~knepley/
> <http://www.cse.buffalo.edu/~knepley/>
>


-- 
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

https://www.cse.buffalo.edu/~knepley/ <http://www.cse.buffalo.edu/~knepley/>
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