Reusing mesh when saving to Fides

[massimiliano-leoni]

Currently FidesWriter saves the mesh whenever the write method is called. This is natural for time-dependent problems with a moving mesh but it's a waste of disk space for problems with an unchanging mesh.

I asked on the Fides issue tracker [see https://gitlab.kitware.com/vtk/fides/-/issues/15 ] and I found out that if a new mesh is not saved then Fides will automagically reuse the previous one.
This pull request adds a flag to let the user reuse a previously-saved mesh and does not change the previous default behaviour.

[garth-wells]

Does it work if the mesh is periodically re-written?

@massimiliano-leoni

[massimiliano-leoni]

Does it work if the mesh is periodically re-written?

@massimiliano-leoni

From a first test it seems that it doesn't work. I think it either wants as many meshes as there are time steps or just one.

[garth-wells]

Does it work if the mesh is periodically re-written?
@massimiliano-leoni

From a first test it seems that it doesn't work. I think it either wants as many meshes as there are time steps or just one.

If that's the case, maybe the re-write/don't re-write the mesh setting should go in the file constructor?

[massimiliano-leoni]

If that's the case, maybe the re-write/don't re-write the mesh setting should go in the file constructor?

Yes, that makes more sense then. I will apply the change shortly.

[massimiliano-leoni]

@garth-wells it's done, let me know if you like the implementation.

[massimiliano-leoni]

By the way, I checked if VTX can do the same but apparently it can't. Or rather, the file is created successfully but then Paraview can't read it properly and crashes.