Fix getNeighboringCellIndices

[mgjarrett]

What is the change?

The staticmethod to get neighboring cell indices in a StructuredGrid is implemented incorrectly:

armi/armi/reactor/grids/structuredgrid.py

Lines 379 to 382 in 14c951a

	@staticmethod
	def getNeighboringCellIndices(i, j=0, k=0):
	"""Return the indices of the immediate neighbors of a mesh point in the plane."""
	return ((i + 1, j, k), (1, j + 1, k), (i - 1, j, k), (i, j - 1, k))

It looks like a typo; there is a 1 where there should be an i.

Also, a unit test is added to cover this function.

Why is the change being made?

The previous implementation is incorrect.

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Checklist

• This PR has only one purpose or idea.
• Tests have been added/updated to verify that the new/changed code works.

• The code style follows good practices.
• The commit message(s) follow good practices.

• The release notes (location doc/release/0.X.rst) are up-to-date with any important changes.
• The documentation is still up-to-date in the doc folder.
• If any requirements were affected, mention it in the release notes.
• The dependencies are still up-to-date in pyproject.toml.

[opotowsky]

Whoah nice catch! Will this affect internal integration testing?

[john-science]

Whoah nice catch! Will this affect internal integration testing?

Michael did that testing. This is ready for prime time.

[drewj-usnctech]

FWIW this existed prior to the refactoring in #1373

armi/armi/reactor/grids.py

Lines 929 to 932 in da28372

	@staticmethod
	def getNeighboringCellIndices(i, j=0, k=0):
	"""Return the indices of the immediate neighbors of a mesh point in the plane."""
	return ((i + 1, j, k), (1, j + 1, k), (i - 1, j, k), (i, j - 1, k))

My intention there was just to copy code off Grid and move it to StructuredGrid. But I'm glad it has been discovered and fixed!

[mgjarrett]

Ah, I didn't look that closely. Didn't see the side-by-side diff because it was moved to a new file.

It looks like this had been around for over 5 years (probably much longer). I guess this shows how little exercise the Cartesian code gets.