Conservative AMR

[andrewwinters5000]

Now the Jacobian weighted solution Ju rather than only the solution u is interpolated and/or projected during the coarsen and refinement of the AMR procedure. This maintains conservation on 2D and 3D curvilinear meshes. Some tests may need updated now that the refine/coarsen procedures change.

Update: My hopes were too optimistic. It seems many test values need updated :(

[github-actions]

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[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 96.29%. Comparing base (26ab5fa) to head (b650fff).
Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2028      +/-   ##
==========================================
+ Coverage   96.27%   96.29%   +0.02%     
==========================================
  Files         462      466       +4     
  Lines       37052    37226     +174     
==========================================
+ Hits        35671    35845     +174     
  Misses       1381     1381              

Flag	Coverage Δ
unittests	96.29% <100.00%> (+0.02%)	⬆️

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[DanielDoehring]

Thanks a lot Andrew! One thing it would suggest is that we add (possibly only in the test directory) a test for conservation. This way we can ensure this issue does not pop up later on again.

[DanielDoehring]

I have two suggestions for explanatory comments which I feel would be useful when added. The code formatter does cruel things, though.

[andrewwinters5000]

I have two suggestions for explanatory comments which I feel would be useful when added. The code formatter does cruel things, though.

Thanks! I can add comments to explain why the element_id is incremented in this way.

[andrewwinters5000]

I think the (occasional) failing MPI test on T8codeMesh is due to an existing issue that these tests occasionally segfault. Do I remember this correctly @jmark ? Or did this issue get fixed?

[jmark]

I think the (occasional) failing MPI test on T8codeMesh is due to an existing issue that these tests occasionally segfault. Do I remember this correctly @jmark ? Or did this issue get fixed?

Yes, indeed. I could narrow it down to the interaction between t8code, MPI and Julia's garbage collector. I offer a workaround in #1980.

It boils down to explicitly finalizing the mesh object of a T8codeMesh in each elixir.

# Finalize `T8codeMesh` to make sure MPI related objects in t8code are
# released before `MPI` finalizes.
!isinteractive() && finalize(mesh)

I think it is best to push a PR just doing this. I'll do it right now. Then you can merge it in. Give me a minute.

[jmark]

Just pushed this PR #2043.

[ranocha]

Thanks a lot! I just have a last round of suggestions

[ranocha]

Thanks!

[ranocha]

@andrewwinters5000 I added a NEWS.md entry since this is a kind of bigger change. Could you please check whether it looks good to you?

[ranocha]

Thanks

[sloede]

Nice work - thanks a lot for investigating and fixing this, @andrewwinters5000 ♥️