Set TreeMesh capacity attribute also when using MPI

[benegee]

Resolves #1861

[github-actions]

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[ranocha]

Thanks! Did you check whether loading a mesh in serial works when you save it in parallel with a small capacity?
I don't remember right now whether the capacity is a local one or needs to be big enough to store the data from all MPI ranks in parallel. That's why I'm asking.

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 1 lines in your changes are missing coverage. Please review.

Project coverage is 89.44%. Comparing base (b11bc10) to head (485355a).
Report is 1 commits behind head on main.

Files	Patch %	Lines
src/meshes/mesh_io.jl	0.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1862      +/-   ##
==========================================
- Coverage   89.45%   89.44%   -0.00%     
==========================================
  Files         438      438              
  Lines       35592    35593       +1     
==========================================
  Hits        31836    31836              
- Misses       3756     3757       +1     

Flag	Coverage Δ
unittests	89.44% <0.00%> (-<0.01%)	⬇️

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[sloede]

Looks reasonable to me

[sloede]

Thanks! Did you check whether loading a mesh in serial works when you save it in parallel with a small capacity? I don't remember right now whether the capacity is a local one or needs to be big enough to store the data from all MPI ranks in parallel. That's why I'm asking.

The capacity is always global. Since the TreeMesh is parallelized by keeping a full copy on each rank and just syncing it between the processes, a "local" capacity does not make much sense anyways

[benegee]

Thanks for the explanation. I would not have known.

I only tested running the simulation in parallel and reading the results in serial via Trixi2Vtk.