Implement more detailed __lt__ for component sorting

[mgjarrett]

Components on a block are sorted by their getBoundingCircleOuterDiameter.

armi/armi/reactor/components/component.py

Lines 272 to 288 in abd1db4

	def __lt__(self, other):
	"""
	True if a circle encompassing this object has a smaller diameter than one encompassing another component.
	This allows sorting because the Python sort functions only use this method.
	"""
	thisOD = self.getBoundingCircleOuterDiameter(cold=True)
	thatOD = other.getBoundingCircleOuterDiameter(cold=True)
	try:
	return thisOD < thatOD
	except Exception:
	raise ValueError(
	"Components 1 ({} with OD {}) and 2 ({} and OD {}) cannot be ordered because their "
	"bounding circle outer diameters are not comparable.".format(
	self, thisOD, other, thatOD
	)
	)

Sometimes, two components have the same outer diameter, in which case the sorting done by __lt__ will depend on the order of comparison. i.e.,

a < b evaluates to False
b < a also evaluates to False

As a result,

sorted([a, b]) = [a, b]
while
sorted([b, a]) = [b, a]

Ideally, the outcome of sorted will not be dependent on the order of the input.

We should fall back to getCircleInnerDiameter for comparison when sorting components when getBoundingCircleOuterDiameter is equivalent. I pushed an example of what I think the sorting should do here:

main...component_sort

[john-science]

Love it.

Improved consistency, I support this idea.