Also return errorsmatrix in convergence_test

[JoshuaLampert]

Closes #2749.

[github-actions]

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 97.03%. Comparing base (21e5576) to head (2372a1b).

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2753      +/-   ##
==========================================
- Coverage   97.03%   97.03%   -0.00%     
==========================================
  Files         570      570              
  Lines       44644    44643       -1     
==========================================
- Hits        43320    43319       -1     
  Misses       1324     1324              

Flag	Coverage Δ
unittests	97.03% <100.00%> (-<0.01%)	⬇️

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[ranocha]

Thanks! I converted this to a draft PR so that nobody merges it accidentally.

[ranocha]

Do we need to adapt https://trixi-framework.github.io/TrixiDocumentation/stable/#Performing-a-convergence-analysis as well?

[JoshuaLampert]

Do we need to adapt trixi-framework.github.io/TrixiDocumentation/stable#Performing-a-convergence-analysis as well?

Everything explained in that section still works because it didn't say anything about the returned values of convergence_test. We could, however, extend the section a bit to explain what is returned.

[ranocha]

That would be nice indeed 👍

[JoshuaLampert]

Should we maybe also return the whole eocs instead of only eoc_mean_values? The mean values can easily be computed from eocs, but often one want to print the eocs in a table and not (only) the mean values. So one would like to have the complete eocs. Alternatively, since returning eocs and errorsmatrix feels a bit redundant, we could also only return errorsmatrix and add a utility function, which computes the eocs from the errors matrix.

[ranocha]

Good suggestion. I would slightly prefer returning the EOCs and the errors. A general-purpose method to compute EOCs may be helpful but also confusing, since we use a fixed refinement by a factor of two and do not need the flexibility to use something that is increasing (number of time steps) or decreasing (time step size).

[ranocha]

Thanks a lot! This looks mostly good to me - I just have a minor suggestion.