scheduler: normalize node affinity by the larger of the pos/neg weight sums

[larrasket]

Description

NodeAffinityIterator normalized a node's affinity score by the sum of the absolute value of every affinity weight. When a job mixed positive and negative weights, an anti-affinity on one node inflated the denominator for an unrelated node that only matched a positive affinity (and vice versa), the score does not reached the [-1, 1] range.

For example a +100 affinity on node A plus a -100 anti-affinity on node B scored node A at 0.5 instead of 1.0.

This divides by the larger of the total positive weight and the total negative weight instead. This restores the range while still keeping scores within [-1, 1], since the matched total is bounded by the positive sum above and the negative sum below.

Testing & Reproduction steps

Links

Fixes #11130

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