[petsc-users] non-manifold DMPLEX

[Matthew Knepley]

On Sun, Dec 12, 2021 at 6:11 AM Patrick Sanan <patrick.sanan at gmail.com>
wrote:

> Here you have the following "points":
>
> - 1 3-cell (the cube volume)
> - 7 2-cells (the 6 faces of the cube plus the extra one)
> - 16 1-cells  (the 12 edges of the cube, plus 3 extra ones from the extra
> face, plus the extra edge)
> - 11 0-cells (the 8 vertices of the cube, pus 2 extra ones from the extra
> face, plus the extra vertex)
>
> You could encode your mesh as here, by directly specifying relationships
> between these points in the Hasse diagram:
>
> https://petsc.org/release/docs/manual/dmplex/#representing-unstructured-grids
>
> Then, maybe the special relation is captured because you've defined the
> "cone" or "support" for each "point", which tells you about the local
> topology everywhere. E.g. to take the simpler case, three of the faces have
> the yellow edge in their "cone", or equivalently the yellow edge has those
> three faces in its "support".
>

This is correct. I can help you make this if you want. I think if you
assign cell types, you can even get Plex to automatically interpolate.

Note that with this kind of mesh, algorithms which assume a uniform cell
dimension will break, but I am guessing you would not
be interested in those anyway.

  Thanks,

    Matt


> Am Fr., 10. Dez. 2021 um 17:04 Uhr schrieb TARDIEU Nicolas via petsc-users
> <petsc-users at mcs.anl.gov>:
>
>> Dear PETSc Team,
>>
>> Following a previous discussion on the mailing list, I'd like to
>> experiment with DMPLEX with a very simple non-manifold mesh as shown in the
>> attached picture : a cube connected to a square by an edge and to an edge
>> by a point.
>> I have read some of the papers that Matthew et al. have written, but I
>> must admit that I do not see how to start...
>> I see how the define the different elements but I do not see how to
>> specify the special relationship between the cube and the square and
>> between the cube and the edge.
>> Once it will have been set correctly, what I am hoping is to be able to
>> use all the nice features of the DMPLEX object.
>>
>> Best regards,
>> Nicolas
>>
>>
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-- 
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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