Evolving numerical constants in grammatical evolution with the ephemeral constant method

Abstract

This paper assesses the new numerical-constant generation method called ephemeral constant, which can be seen as a translation of the classical genetic programming's ephemeral random constant to the grammatical evolution framework. Its most distinctive feature is that it decouples the number of bits used to encode the grammar's production rules from the number of bits used to represent a constant. This makes it possible to increase the method's representational power without incurring in an overly redundant encoding scheme. We present experiments comparing ephemeral constant with the three most popular approaches for constant handling: the traditional approach, digit concatenation, and persistent random constant. By varying the number of bits to represent a constant, we can increase the numerical precision to the desired level of accuracy, overcoming by a large margin the other approaches. © 2011 Springer-Verlag.