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Not quite done, as pyproject.toml depends on PETSc4py? @garth-wells

This has not been supported for a long time (and is partially the reason why I made `dolfinx_mpc`. However, for the special case that the mesh nodes/facets align on each...

> Is there a reason why the `dolfinx_mpc` approach will be noticeably slower than a more integrated approach when facets match? DOLFINx_MPC does not alter the dofmap, as this is...

> @jorgensd thoughts? I guess we should be able to add a check when generating the form that we have the appropriate ghosting (at least for dS integrals). At least...

> No longer sure this is a good idea. #1989 maybe better starting point. Due to https://github.com/ornladios/ADIOS2/issues/3688 this is a no-go for now. Let's rather focus on 1989.

> Some preliminary comments. > > Could this be divided into a 'read' PR, and a checkpoint PR after? No, as this reads the mesh from the mesh format this...

> Some preliminary comments. > > Could this be divided into a 'read' PR, and a checkpoint PR after? Changes have been made according to your suggestions, any further comments?

@garth-wells Any further comments?

> Another round of comments. > > > > Would be helpful to have clear statement in the PR of what functionality is being add. The code can write meshes...

> What's a 'global array'? An ADIOS2 concept? Yes. Consider writing out a mesh with the VTXWriter in serial: ```bash root@dokken-XPS-9320:~/shared/dolfinx/cpp/demo/poisson# ./build-dir-real64/demo_poisson root@dokken-XPS-9320:~/shared/dolfinx/cpp/demo/poisson# bpls -l mesh.bp/ uint32_t NumberOfCells {1} =...