Escaping local optima with diversity mechanisms and crossover

DC Dang, T Friedrich, T Kötzing, MS Krejca… - Proceedings of the …, 2016 - dl.acm.org
Proceedings of the Genetic and Evolutionary Computation Conference 2016, 2016dl.acm.org
Population diversity is essential for the effective use of any crossover operator. We compare
seven commonly used diversity mechanisms and prove rigorous run time bounds for the (μ+
1) GA using uniform crossover on the fitness function Jump k. All previous results in this
context only hold for unrealistically low crossover probability pc= O (k/n), while we give
analyses for the setting of constant pc< 1 in all but one case. Our bounds show a
dependence on the problem size~ n, the jump length k, the population size μ, and the …
Population diversity is essential for the effective use of any crossover operator. We compare seven commonly used diversity mechanisms and prove rigorous run time bounds for the (μ+1) GA using uniform crossover on the fitness function Jumpk. All previous results in this context only hold for unrealistically low crossover probability pc=O(k/n), while we give analyses for the setting of constant pc < 1 in all but one case. Our bounds show a dependence on the problem size~, the jump length k, the population size μ, and the crossover probability pc. For the typical case of constant k > 2 and constant pc, we can compare the resulting expected optimisation times for different diversity mechanisms assuming an optimal choice of μ:
  • O}(nk-1) for duplicate elimination/minimisation,
  • O}(n2 log n) for maximising the convex hull,
  • O(n log n) for det. crowding (assuming pc = k/n),
  • O(n log n) for maximising the Hamming distance,
  • O(n log n) for fitness sharing,
  • O(n log n) for the single-receiver island model.
This proves a sizeable advantage of all variants of the (μ+1) GA compared to the (1+1) EA, which requires θ(nk). In a short empirical study we confirm that the asymptotic differences can also be observed experimentally.
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