Illinois Genetic Algorithms Laboratory

Butz, M. V., Sastry, K., Goldberg, D. E. (2002)
TR No.: 2002020 | Download PDF | Download PS

Abstract:
Selection in the accuracy-based learning classifier system XCS, introduced by Wilson in 1995, has always been done by the means of proportionate selection. Although it is known from GA literature that proportionate selection is subject to many pitfalls, the LCS community adhered to proportionate selection. In XCS, the accuracy-based fitness is scaled which made proportionate selection work in many problems. This paper investigates performance in Boolean functions in which proportionate selection fails to solve the function. Tournament selection with
tournament sizes proportionate to the actual set size is shown to outperform proportionate selection in all investigated problems. Moreover, it is shown that tournament selection makes XCS more independent from various parameter settings. The message of this paper is plain and simple: Who works with XCS should use tournament selection with tournament sizes proportionate to the actual set size.