On the Locality of Grammatical Evolution

It is well known that using high-locality representations is important for efficient evolutionary search. This paper investigates the locality of the genotype-phenotype mapping (representation) used in grammatical evolution (GE). The results show that the representation used in GE has problems with locality as many neighboring genotypes do not correspond to neighboring phenotypes. Experiments with a simple local search strategy reveal that the GE representation leads to lower performance for mutationbased search approaches in comparison to standard GP representations. The results suggest that locality issues should be considered for further development of the representation used in GE.