[petsc-users] Inquiry regarding DMAdaptLabel function

[Zongze Yang]

Hi, Matt,

I tested coarsening a mesh by using ParMMg without firedrake, and found
some issues:
 see the code and results here:
https://gitlab.com/petsc/petsc/-/issues/1331

Could you have a look and give some comments or suggestions?

Best wishes,
Zongze


On Mon, 27 Feb 2023 at 20:19, Matthew Knepley <knepley at gmail.com> wrote:

> On Sat, Feb 18, 2023 at 6:41 AM Zongze Yang <yangzongze at gmail.com> wrote:
>
>> Another question on mesh coarsening is about `DMCoarsen` which will fail
>> when running in parallel.
>>
>> I generate a mesh in Firedrake, and then create function space and
>> functions, after that, I get the dmplex and coarsen it.
>> When running in serials, I get the mesh coarsened correctly. But it
>> failed with errors in ParMMG when running parallel.
>>
>> However, If I did not create function space and functions on the original
>> mesh, everything works fine too.
>>
>> The code and the error logs are attached.
>>
>
> I believe the problem is that Firedrake and PETSc currently have
> incompatible coordinate spaces. We are working
> to fix this, and I expect it to work by this summer.
>
>   Thanks,
>
>      Matt
>
>
>> Thank you for your time and attention。
>>
>> Best wishes,
>> Zongze
>>
>>
>> On Sat, 18 Feb 2023 at 15:24, Zongze Yang <yangzongze at gmail.com> wrote:
>>
>>> Dear PETSc Group,
>>>
>>> I am writing to inquire about the function DMAdaptLabel in PETSc.
>>> I am trying to use it coarse a mesh, but the resulting mesh is refined.
>>>
>>> In the following code, all of the `adpat` label values were set to 2
>>> (DM_ADAPT_COARSEN).
>>> There must be something wrong. Could you give some suggestions?
>>>
>>> ```python
>>> from firedrake import *
>>> from firedrake.petsc import PETSc
>>>
>>> def mark_all_cells(mesh):
>>>     plex = mesh.topology_dm
>>>     with PETSc.Log.Event("ADD_ADAPT_LABEL"):
>>>         plex.createLabel('adapt')
>>>         cs, ce = plex.getHeightStratum(0)
>>>         for i in range(cs, ce):
>>>             plex.setLabelValue('adapt', i, 2)
>>>
>>>     return plex
>>>
>>> mesh = RectangleMesh(10, 10, 1, 1)
>>>
>>> x = SpatialCoordinate(mesh)
>>> V = FunctionSpace(mesh, 'CG', 1)
>>> f = Function(V).interpolate(10 + 10*sin(x[0]))
>>> triplot(mesh)
>>>
>>> plex = mark_all_cells(mesh)
>>> new_plex = plex.adaptLabel('adapt')
>>> mesh = Mesh(new_plex)
>>> triplot(mesh)
>>> ```
>>>
>>> Thank you very much for your time.
>>>
>>> Best wishes,
>>> Zongze
>>>
>>
>
> --
> 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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