An adverse interaction between crossover and restricted tree depth in genetic programming

  • Authors:
  • Chris Gathercole;Peter Ross

  • Affiliations:
  • University of Edinburgh, Edinburgh, U.K.;University of Edinburgh, Edinburgh, U.K.

  • Venue:
  • GECCO '96 Proceedings of the 1st annual conference on Genetic and evolutionary computation
  • Year:
  • 1996

Quantified Score

Hi-index 0.00

Visualization

Abstract

The Crossover operator is common to most implementations of Genetic Programming (GP). Often, there is some form of restriction on the size of trees in the GP population. This paper concentrates on the interaction between the standard crossover operator and a restriction on tree depth demonstrated by the MAX problem, which involves returning the largest possible value for given function and terminal sets and maximum tree depth. Some characteristics and inadequacies of crossover in normal use are highlighted and discussed. Subtree discovery and movement takes place mostly near the leaf nodes, with nodes near the root left untouched, where diversity drops quickly to zero in the tree population. GP is then unable to create fitter trees via the crossover operator, leaving a mutation operator as the only common, but ineffective, route to discovery of fitter trees.