A Comparative Study on Crossover in Cartesian Genetic Programming

Cartesian Genetic Programming is often used with mutation as the sole genetic operator. Compared to the fundamental knowledge about the effect and use of mutation in CGP, the use of crossover has been less investigated and studied. In this paper, we present a comparative study of previously proposed crossover techniques for Cartesian Genetic Programming. This work also includes the proposal of a new crossover technique which swaps block of the CGP phenotype between two selected parents. The experiments of our study open a new perspective on comparative studies on crossover in CGP and its challenges. Our results show that it is possible for a crossover operator to outperform the standard (1 + lambda) strategy on a limited number of tasks. The question of finding a universal crossover operator in CGP remains open.