Fix strength calculation axis in SPEA2Survival._do to match SPEA2 algorithm definition #755
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This pull request resolves anyoptimization/pymoo#748 by correcting the axis used for strength calculation in the
SPEA2Survival._domethod.Previously, strength
Swas computed asS = (M == 1).sum(axis=0), which incorrectly counts the number of times each individual is dominated by others.According to the SPEA2 algorithm (see Zitzler, E., Laumanns, M., & Thiele, L. (2001). SPEA2: Improving the Strength Pareto Evolutionary Algorithm. TIK-Report 103), strength should be calculated as the number of individuals each solution dominates:
S = (M == 1).sum(axis=1).