[petsc-users] DMPlex and Boundary facets

[Matthew Knepley]

On Wed, May 19, 2021 at 9:57 AM Karin&NiKo <niko.karin at gmail.com> wrote:

> Thank you very much Lawrence.
> Are the names lost or are they saved somewhere ?
> If I do : "./ex2 -filename /tmp/test/Cube_with_facets.msh4 -dm_view
> vtk:/tmp/foo.vtk" , I only get the tets of the initial mesh.
>

Yes, the names are lost. Jed, Lisandro and Stefano have also asked me about
this. I have not done since everything is currently done by
number in Plex. It would involve either

a) making a separate table in the DM which translates names to numbers

or

b) putting such a translation table in the DMLabel itself

I am putting it off because doing some short is not hard, but getting it to
work with everything else would be somewhat of a pain.
It would need to distribute properly, propagate to refined/coarsened/subset
meshes, etc. which labels currently do. It would not
be properly passed on when you just set an int on a point. I think it will
happen eventually, but I don't think I have time in the next
few weeks.

  Thanks,

     Matt


> Thanks,
> Nicolas
>
> Le mer. 19 mai 2021 à 15:49, Lawrence Mitchell <wence at gmx.li> a écrit :
>
>>
>>
>> > On 19 May 2021, at 14:46, Karin&NiKo <niko.karin at gmail.com> wrote:
>> >
>> > Dear Matthew,
>> >
>> > You are (again) right. This Gmsh test file is "dirty" : some triangles
>> do not belong to tests. Sorry for that.
>> > I have tried with another geo file (which is clean in that sense) and
>> PETSc reads with no error.
>> >
>> > I take this opportunity to ask my initial question : are the labels of
>> the Physical Entities saved somewhere ?
>> > A gmsh test file with several Physical entities is attached to this
>> email.
>>
>> Yes, plex represents Physical entities as "labels". In particular, for
>> facets, they are loaded as the "Face Sets" label, plex also loads markers
>> on cells in the "Cell Sets" label.
>>
>> e.g. here's the DMView output of your mesh.
>>
>> DM Object: DM_0x84000000_0 1 MPI processes
>>   type: plex
>> DM_0x84000000_0 in 3 dimensions:
>>   0-cells: 64
>>   1-cells: 279
>>   2-cells: 378
>>   3-cells: 162
>> Labels:
>>   celltype: 4 strata with value/size (0 (64), 6 (162), 3 (378), 1 (279))
>>   depth: 4 strata with value/size (0 (64), 1 (279), 2 (378), 3 (162))
>>   Cell Sets: 1 strata with value/size (7 (162))
>>   Face Sets: 6 strata with value/size (3 (18), 6 (18), 2 (18), 5 (18), 1
>> (18), 4 (18))
>>
>>
>> Lawrence
>
>

-- 
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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