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

[Praveen C]

Thank you very much. I do see correct normals now.

Is there a way to set the option

>> -dm_localize_height 1

within the code ?

best
praveen

> On 15-Dec-2022, at 9:53 PM, Matthew Knepley <knepley at gmail.com> wrote:
> 
> On Wed, Dec 14, 2022 at 9:20 AM Praveen C <praveen at gmx.net <mailto: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 <mailto:knepley at gmail.com>> wrote:
>>> 
>>> On Wed, Dec 14, 2022 at 2:38 AM Praveen C <praveen at gmx.net <mailto: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 <mailto:knepley at gmail.com>> wrote:
>>>>> 
>>>>> On Tue, Dec 13, 2022 at 10:57 AM Matthew Knepley <knepley at gmail.com <mailto:knepley at gmail.com>> wrote:
>>>>>> On Tue, Dec 13, 2022 at 6:11 AM Praveen C <praveen at gmx.net <mailto: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/>
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