DEB
et al.: A FAST AND ELITIST MULTIOBJECTIVE GA: NSGA-II
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Fig. 1.
Crowding-distance calculation. Points marked in filled circles are
solutions of the same nondominated front.
2) Since each solution must be compared with all other so-
lutions in the population, the overall complexity of the
sharing function approach is
.
In the proposed NSGA-II, we replace the sharing function
approach with a crowded-comparison approach that eliminates
both the above difficulties to some extent. The new approach
does not require
any user-defined parameter for maintaining
diversity among population members. Also, the suggested ap-
proach has a better computational complexity. To describe this
approach, we first define a density-estimation metric and then
present the crowded-comparison operator.
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