Perhaps loosen strictness on LocationBase equality check grids?

[drewj-tp]

I stumbled on this weird quirk working on assembly rotation: If I deepcopy a block with a grid and grab the same component from the original and copied block, their locations will not be equal. In testing, I got weird errors like

<IndexLocation @ (0,0,0)> != <IndexLocation @ (0,0,0)>

which is confusing at first. These are both the center location on a hexagonal grid of the same pitch. Their locations should compare equal?

Turns out, two locations must have the exact same grid object attached, not an equivalent grid

armi/armi/reactor/grids/locations.py

Lines 100 to 109 in c6f46e5

	def __eq__(self, other: Union[Tuple[int, int, int], "LocationBase"]) -> bool:
	if isinstance(other, tuple):
	return (self.i, self.j, self.k) == other
	if isinstance(other, LocationBase):
	return (
	self.i == other.i
	and self.j == other.j
	and self.k == other.k
	and self.grid is other.grid
	)

Would it make sense to have the check on grids be self.grids == other.grids? We don't currently provide Grid.__eq__ so that'd be a need

[john-science]

My take is that there was no Grid.__eq__() method or SpatialGrid.__eq__() method, so someone got lazy. We'd have to look at how to compare grids, but if that's doable, do it. Sure.

[drewj-tp]

It should be relatively easy? Same type and same pitch? And I guess orientation for hex grids?

[drewj-tp]

But we also have these internal _locations default-dict like attributes that store indices for things that may or may not be on the grid. Should those factor into the equality?

armi/armi/reactor/grids/structuredGrid.py

Lines 263 to 280 in d3cc8e5

	try:
	return self._locations[ijk]
	except (KeyError, TypeError):
	pass
	if isinstance(ijk, tuple):
	i, j, k = ijk
	val = IndexLocation(i, j, k, self)
	self._locations[ijk] = val
	elif isinstance(ijk, list):
	val = MultiIndexLocation(self)
	locators = [self[idx] for idx in ijk]
	val.extend(locators)
	else:
	raise TypeError(
	"Unsupported index type `{}` for `{}`".format(type(ijk), ijk)
	)
	return val

So you could have two hex grids of the same pitch and orientation, but their length, as reported by __len__

armi/armi/reactor/grids/structuredGrid.py

Lines 182 to 183 in d3cc8e5

	def __len__(self) -> int:
	return len(self._locations)

could differ. And that feels weird?