[petsc-users] How to use DMPlex_Distribute(_Overlap) without redistribution of the mesh

[Fabian.Jakub]

Hi Matt,
I see now that it does not have anything to do with the overlap, it is
just the distribute itself.

I attach two images with the cell ownership of the mesh on four ranks.
Once before and once after the distribute call.

I guess this comes from the way in which I generate the mesh.
I start with a 2D triangle mesh horizontally, which is distributed.
After that, I extrude the mesh vertically.

Now it seems that the partitioner deems a different partitioning better
for the 3D mesh.

Can I prevent DMPlexDistribute to do that?

Many Thanks,
Fabian


On 10/2/19 12:19 PM, Matthew Knepley wrote:
> On Tue, Oct 1, 2019 at 7:39 PM Fabian.Jakub via petsc-users <
> petsc-users at mcs.anl.gov> wrote:
> 
>> Dear Petsc team,
>> dear Matt,
>>
>> I have a 3D, distributed DMPlex with 0 overlap in FVM adjacency.
>> Now, I would like to add overlap but not change the local portions.
>> I was wondering if you could suggest how to do that best/easiest.
>>
>> My problem is that just using DMPlexDistribute changes the partitioning,
>> i.e. cells change owners.
>>
>> I guess I could trace the steps you took in
>> DMPlexDistributeOverlap
>>
> 
> DistributeOverlap() should not change the partition. Are you sure it does?
> I think you just call that.
> 
>   Thanks,
> 
>     Matt
> 
> 
>> and the following stuff you have in
>> DMPlexDistribute() { if overlap > 0 }
>>
>> Another thought was to use a custom partitioner so as not to change the
>> local layouts. Is this a good idea?
>>
>> In case that you suggest to go for first steps (the duplication of the
>> DMPlexDistributeOverlap stuff) could you add a fortran stub for it?
>>
>> Many thanks,
>>
>> Fabian
>>
> 
> 

-------------- next part --------------
A non-text attachment was scrubbed...
Name: partitioning_after0000.png
Type: image/png
Size: 54444 bytes
Desc: not available
URL: <http://lists.mcs.anl.gov/pipermail/petsc-users/attachments/20191002/fc175e0b/attachment-0002.png>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: partitioning_before0000.png
Type: image/png
Size: 31102 bytes
Desc: not available
URL: <http://lists.mcs.anl.gov/pipermail/petsc-users/attachments/20191002/fc175e0b/attachment-0003.png>