Inefficiency in WeightedKendallTauDistance #182
Description
Describe the bug
The way in which WeightedKendallTauDistance currently computes the weighted inversions within the modified mergesort potentially impacts worst case runtime. When an inversion is detected, it currently iterates over remaining left half to sum weights. This can lead to redundant work if the next element in right half is also part of a sequence of inversions. This can be done more efficiently if sum of left half weights is determined first, and modified as left half elements are chosen during the modified mergesort.