Mutation

As mentioned in Appendix A, there are two types of mutation operators: the standard jump mutation that acts on the chromosome (binary representation of the individual, sometimes called genotype) and creep mutations that act on the decoded individual, sometimes called phenotype. In any case, the mutation probabilities are expected to be low, since high values may cause strong disruption of promising schemata and therefore steer the algorithm away from the most promising regions of the search landscape. The top panels of Figure  show a comparison of convergence rates for three values of jump mutation probability 0.002, 0.004 and 0.008, without creep mutations. In this case a jump mutation of 0.002 is the best although a value of 0.005 would have been expected from the rule of thumb of the inverse of the population size. The bottom panels of Figure  show the effect of creep mutations with probabilities of 0.02, 0.04 and 0.08. Again, it seems that a small mutation is actually best. For the remaining I used creep mutation with probability 0.02.

 

SG_compare_mutation1
Figure 7 Comparison of convergence rates for different jump and creep mutation rates. Top panels for jump mutation rates of 0.002, 0.004 and 0.008. Bottom panels for creep mutation rates of 0.02, 0.04 and 0.08.