The Impact of Hyperselection on Lexicase Selection

Abstract

Lexicase selection is a parent selection method that has been shown to improve the problem solving power of genetic programming over a range of problems. Previous work has shown that it can also produce hyperselection events, in which a single individual is selected many more times than other individuals. Here we investigate the role that hyperselection plays in the problem-solving performance of lexicase selection. We run genetic programming on a set of program synthesis benchmark problems using lexicase and tournament selection, confirming that hyperselection occurs significantly more often and more drastically with lexicase selection, which also performs significantly better. We then show results from an experiment indicating that hyperselection is not integral to the problem-solving performance or diversity maintenance observed when using lexicase selection. We conclude that the power of lexicase selection stems from the collection of individuals that it selects, not from the unusual frequencies with which it sometimes selects them.