Approximation Guarantees for the Non-Dominated Sorting Genetic Algorithm
II (NSGA-II)
- URL: http://arxiv.org/abs/2203.02693v3
- Date: Sun, 1 Oct 2023 13:30:48 GMT
- Title: Approximation Guarantees for the Non-Dominated Sorting Genetic Algorithm
II (NSGA-II)
- Authors: Weijie Zheng, Benjamin Doerr
- Abstract summary: We study how well the NSGA-II approximates the Pareto front when the population size is smaller.
This is the first mathematical work on the approximation ability of the NSGA-II and the first runtime analysis for the steady-state NSGA-II.
- Score: 16.904475483445452
- License: http://arxiv.org/licenses/nonexclusive-distrib/1.0/
- Abstract: Recent theoretical works have shown that the NSGA-II efficiently computes the
full Pareto front when the population size is large enough. In this work, we
study how well it approximates the Pareto front when the population size is
smaller.
For the OneMinMax benchmark, we point out situations in which the parents and
offspring cover well the Pareto front, but the next population has large gaps
on the Pareto front. Our mathematical proofs suggest as reason for this
undesirable behavior that the NSGA-II in the selection stage computes the
crowding distance once and then removes individuals with smallest crowding
distance without considering that a removal increases the crowding distance of
some individuals.
We then analyze two variants not prone to this problem. For the NSGA-II that
updates the crowding distance after each removal (Kukkonen and Deb (2006)) and
the steady-state NSGA-II (Nebro and Durillo (2009)), we prove that the gaps in
the Pareto front are never more than a small constant factor larger than the
theoretical minimum. This is the first mathematical work on the approximation
ability of the NSGA-II and the first runtime analysis for the steady-state
NSGA-II. Experiments also show the superior approximation ability of the two
NSGA-II variants.
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