Fix #1194: Unify signatures of mesh constructors

[vincmarks]

I added mesh constructors so that mesh types become interchangeable.

What's new

• initial_refinement_level (like TreeMesh):

# Before: only worked for TreeMesh
TreeMesh((-1.0, -1.0), (1.0, 1.0); initial_refinement_level = 4, n_cells_max = 30_000)

# Now: remove n_cells_max and just swap the mesh type
StructuredMesh((-1.0, -1.0), (1.0, 1.0); initial_refinement_level = 4)
P4estMesh((-1.0, -1.0), (1.0, 1.0);     initial_refinement_level = 4, polydeg = 3)
T8codeMesh((-1.0, -1.0), (1.0, 1.0);    initial_refinement_level = 4)
DGMultiMesh(dg;  initial_refinement_level = 4, coordinates_min = (-1.0, -1.0), coordinates_max = (1.0, 1.0))

• cells_per_dimension positional (now also for P4estMesh/T8codeMesh)

P4estMesh((16, 16), (-1.0, -1.0), (1.0, 1.0); polydeg = 3)
T8codeMesh((16, 16), (-1.0, -1.0), (1.0, 1.0))

• keyword-based (now also for StructuredMesh/T8codeMesh/DGMultiMesh)

StructuredMesh((16, 16); coordinates_min = (-1.0, -1.0), coordinates_max = (1.0, 1.0))
DGMultiMesh(dg; cells_per_dimension = (16, 16), coordinates_min = (-1.0, -1.0), coordinates_max = (1.0, 1.0))

I already added some explanation in the docs and an example file (examples/special_elixirs/elixir_advection_mesh_swap.jl).

[github-actions]

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[ranocha]

Thanks a lot! We just had a developer meeting and brainstormed a bit about the desired interface. Something like T8codeMesh((16, 16), (-1.0, -1.0), (1.0, 1.0)) looks a bit obscure. Thus, we thought it would be best if the constructor working for all mesh types uses keyword arguments only, e.g.,

TreeMesh(coordinates_min = (-1.0, -1.0),
         coordinates_max = (1.0, 1.0), 
         initial_refinement_level = 4, n_cells_max = 30_000)
StructuredMesh(coordinates_min = (-1.0, -1.0),
               coordinates_max = (1.0, 1.0), 
               initial_refinement_level = 4)
P4estMesh(coordinates_min = (-1.0, -1.0),
          coordinates_max = (1.0, 1.0), 
          initial_refinement_level = 4)
T8codeMesh(coordinates_min = (-1.0, -1.0),
           coordinates_max = (1.0, 1.0), 
           initial_refinement_level = 4)
DGMultiMesh(dg; coordinates_min = (-1.0, -1.0),
            coordinates_max = (1.0, 1.0), 
            initial_refinement_level = 4)

Under the hood, these keyword-only constructors should forward the keyword arguments to constructors taking positional arguments (to be able to use dispatch there). Could you please update the API accordingly?

[vincmarks]

Thanks a lot! We just had a developer meeting and brainstormed a bit about the desired interface. Something like T8codeMesh((16, 16), (-1.0, -1.0), (1.0, 1.0)) looks a bit obscure. Thus, we thought it would be best if the constructor working for all mesh types uses keyword arguments only, e.g.,

TreeMesh(coordinates_min = (-1.0, -1.0),
         coordinates_max = (1.0, 1.0), 
         initial_refinement_level = 4, n_cells_max = 30_000)
StructuredMesh(coordinates_min = (-1.0, -1.0),
               coordinates_max = (1.0, 1.0), 
               initial_refinement_level = 4)
P4estMesh(coordinates_min = (-1.0, -1.0),
          coordinates_max = (1.0, 1.0), 
          initial_refinement_level = 4)
T8codeMesh(coordinates_min = (-1.0, -1.0),
           coordinates_max = (1.0, 1.0), 
           initial_refinement_level = 4)
DGMultiMesh(dg; coordinates_min = (-1.0, -1.0),
            coordinates_max = (1.0, 1.0), 
            initial_refinement_level = 4)

Under the hood, these keyword-only constructors should forward the keyword arguments to constructors taking positional arguments (to be able to use dispatch there). Could you please update the API accordingly?

Thanks for the feedback, I'll update the API accordingly.

[ranocha]

Please ping me when this PR is ready for a review.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 97.09%. Comparing base (bc1048b) to head (8554ea4).

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #3000   +/-   ##
=======================================
  Coverage   97.09%   97.09%           
=======================================
  Files         630      630           
  Lines       48855    48881   +26     
=======================================
+ Hits        47435    47461   +26     
  Misses       1420     1420           

Flag	Coverage Δ
unittests	97.09% <100.00%> (+<0.01%)	⬆️

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[vincmarks]

@ranocha, the PR is ready for review

[vincmarks]

Thanks for the feedback! In the last view commits (ad76138, 60ec745,ebe65fc,1eda211) I made the following changes:

• Renamed initial_refinement_level to refinement_level
• Removed DGMultiMesh from the docstrings
• Documented the P4estMesh kwargs accordingly
• Added a length check for coordinates_min/coordinates_max with testing
• Deleted the elixir file and replaced it with runnable examples in the docs. Let me know if you prefer to remove those as well.

[ranocha]

Thanks!