[petsc-users] Inquiry regarding DMAdaptLabel function

[Zongze Yang]

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.

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
>
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