Analysing the effects of diverse operators in a genetic programming system

Abstract

Some Genetic Programming (GP) systems have fewer structural constraints than expression tree GP, permitting a wider range of operators. Using one such system, TAG3P, we compared the effects of such new operators with more standard ones on individual fitness, size and depth, comparing them on a number of symbolic regression and tree structuring problems. The operator effects were diverse, as the originators had claimed. The results confirm the overall primacy of crossover, but strongly suggest that new operators can usefully supplement, or even replace, subtree mutation. They give a better understanding of the features of each operator, and the contexts where it is likely to be useful. They illuminate the diverse effects of different operators, and provide justification for adaptive use of a range of operators.