Kumara Sastry

Strong, stable, and reliable fitness pressure in XCS due to tournament selection

Butz, M. V., Sastry, K., Goldberg, D. E. (2005). Genetic Programming and Evolvable Machines, 6, 53—77. [Full paper - PDF] [Full paper - PS].

Abstract:

Recent analysis of the XCS classifier system have shown that successful genetic learning strongly depends on the amount of fitness pressure towards accurate classifiers. Since the traditionally used proportionate selection is dependent on fitness scaling and fitness distribution, the resulting evolutionary fitness pressure may be neither stable nor sufficiently strong. Thus, we apply tournament selection to XCS. In particular, we exhibit the weakness of proportionate selection and suggest tournament selection as a more reliable alternative. We show that tournament selection results in a learning classifier system that is more parameter independent, noise independent, and more efficient in exploiting fitness guidance in single-step problems as well as multistep problems. The evolving population is more focused on promising subregions of the problem space and thus finds the desired accurate, maximally general representation faster and more reliably.

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