correct domain_dimensions in non-fixed block size uniform grid FLASH output

[acreyes]

PR Summary

In non-fixed block size grids FLASH output the domain is output as a single block, rather than being domain decomposed as is assumed for the fixed block size UG. This PR checks for this case
so that yt correctly determines domain_dimensions.

PR Checklist

• New features are documented, with docstrings and narrative docs
• Adds a test for any bugs fixed. Adds tests for new features.

[welcome]

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[neutrinoceros]

hi @acreyes , thank you for your contribution !
I don't think we need a new test for it, but could you share with us some additional insight, like a quote from Flash's documentation that references this, or maybe a small sample data file that uses it ?

Failure other than linting are unrelated, so I'm going to auto-format now.

[neutrinoceros]

pre-commit.ci autofix

[acreyes]

From the FLASH users guide:

Hierarchical Data Format (HDF) 5 output. A single HDF5 file is created, with each processor writing its data to the same file simultaneously. All data is written out as one block. This relies on the underlying MPIIO layer in HDF5. This particular implementation only works in non-fixedblocksize mode.

Here's an example of an 8x8 simulation run with 2 mpi ranks in each direction with the non-fixed block size mode in FLASH where I'm plotting a covering_grid using domain_dimensions to illustrate the issue.

assuming 1 block per mpi rank used in the simulation

checking the total number of blocks

[neutrinoceros]

Seems ok to me, but I'll give other maintainers a couple days to reply if they wish.

[matthewturk]

This looks good to me, and I'm happy to defer to this explanation. I'm going to merge. Thank you for your first contribution!

[matthewturk]

(sorry I accidentally hit the wrong button)

[welcome]

Hooray! Congratulations on your first merged pull request! We hope we keep seeing you around! 🎆