[petsc-users] DMPlexDistributeField

[Matthew Knepley]

On Thu, Jun 27, 2019 at 6:15 PM Adrian Croucher <a.croucher at auckland.ac.nz>
wrote:

>
> On 28/06/19 10:09 AM, Zhang, Junchao wrote:
>
>
> Check how the graph is created and then whether the parameters to
> PetscSFSetGraph() are correct.
>
>
> Yes, unfortunately I don't have a good enough understanding of how
> DMPlexDistribute() works to see what the problem is.
>
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.
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.

  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/>
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