[petsc-users] dmplex normal vector incorrect for periodic gmsh grids

[Matthew Knepley]

On Wed, Dec 14, 2022 at 9:20 AM Praveen C <praveen at gmx.net> wrote:

> Hello
>
> I tried this with the attached code but I still get wrong normals.
>
> ./dmplex -dm_plex_filename ug_periodic.msh -dm_localize_height 1
>
>
> Code and grid file are attached
>

I have fixed the code. The above options should now work for you.

  Thanks,

      Matt


> Thank you
> praveen
>
>
>
> On 14-Dec-2022, at 6:40 PM, Matthew Knepley <knepley at gmail.com> wrote:
>
> On Wed, Dec 14, 2022 at 2:38 AM Praveen C <praveen at gmx.net> wrote:
>
>> Thank you, this MR works if I generate the mesh within the code.
>>
>> But using a mesh made in gmsh, I see the same issue.
>>
>
> Because the operations happen in a different order. If you read in your
> mesh with
>
>   -dm_plex_filename mymesh.gmsh -dm_localize_height 1
>
> then it should work.
>
>   Thanks,
>
>      Matt
>
>
>> Thanks
>> praveen
>>
>> On 14-Dec-2022, at 12:51 AM, Matthew Knepley <knepley at gmail.com> wrote:
>>
>> On Tue, Dec 13, 2022 at 10:57 AM Matthew Knepley <knepley at gmail.com>
>> wrote:
>>
>>> On Tue, Dec 13, 2022 at 6:11 AM Praveen C <praveen at gmx.net> wrote:
>>>
>>>> Hello
>>>>
>>>> In the attached test, I read a small grid made in gmsh with periodic bc.
>>>>
>>>> This is a 2d mesh.
>>>>
>>>> The cell numbers are shown in the figure.
>>>>
>>>> All faces have length = 2.5
>>>>
>>>> But using PetscFVFaceGeom I am getting length of 7.5 for some faces.
>>>> E.g.,
>>>>
>>>> face: 59, centroid = 3.750000, 2.500000, normal = 0.000000, -7.500000
>>>> ===> Face length incorrect = 7.500000, should be 2.5
>>>> support[0] = 11, cent = 8.750000, 3.750000, area = 6.250000
>>>> support[1] = 15, cent = 8.750000, 1.250000, area = 6.250000
>>>>
>>>> There are also errors in the orientation of normal.
>>>>
>>>> If we disable periodicity in geo file, this error goes away.
>>>>
>>>
>>> Yes, by default we only localize coordinates for cells. I can put in
>>> code to localize faces.
>>>
>>
>> Okay, I now have a MR for this:
>> https://gitlab.com/petsc/petsc/-/merge_requests/5917
>>
>> I am attaching your code, slightly modified. You can run
>>
>>   ./dmplex -malloc_debug 0 -dm_plex_box_upper 10,10 -dm_plex_box_faces
>> 4,4 -dm_plex_simplex 0 -dm_view ::ascii_info_detail -draw_pause 3
>> -dm_plex_box_bd periodic,periodic -dm_localize_height 0
>>
>> which shows incorrect edges and
>>
>> ./dmplex -malloc_debug 0 -dm_plex_box_upper 10,10 -dm_plex_box_faces 4,4
>> -dm_plex_simplex 0 -dm_view ::ascii_info_detail -draw_pause 3
>> -dm_plex_box_bd periodic,periodic -dm_localize_height 1
>>
>> which is correct. If you want to control things yourself, instead of
>> using the option you can call DMPlexSetMaxProjectionHeight() on the
>> coordinate DM yourself.
>>
>>   Thanks,
>>
>>      Matt
>>
>>
>>>   Thanks,
>>>
>>>     Matt
>>>
>>>
>>>> Thanks
>>>> praveen
>>>>
>>> --
>>>
>>>
>>
>
> --
> 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/>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.mcs.anl.gov/pipermail/petsc-users/attachments/20221215/0f596300/attachment-0001.html>