Saving mesh and mesh_tags using adios4dolfinx

[dokken]

@charithjeewantha

there a difference between mesh vs new_mesh or facet_tags vs new_ft?
Just by the looks of it, both should be the same, but I’m worried whether adios4dolfinx is doing any sort of changes when saving the file.

Adios does not do any sort changes, But it uses the dolfinx mesh, which is repartitioned when read in. This has been explained in:

Parallel function saving and reading it back using PETSc or adios4dolfinx

The issue is that the mesh has been re-ordered, as it has been repartitioned when executed on more than 1 process. A long term goal would maybe be to write the data out in its original order (however, I am not 100 % certain how easy that will be, due to dof transformations/cell permutations). Another note is that this would increase the runtime of write_function, as data is no longer written in a contiguous fashion.

I have just made a checkpointing function that writes the data in the same order as the input mesh, see:

Checkpointing to original mesh

This means that you can read your mesh and meshtags from an XDMFFile, and only read the function from the checkpoint.