Evolving While-Loop Structures in Genetic Programming for Factorial and Ant Problems

Loop is an important structure in human written programs. However, it is seldom used in the evolved programs in genetic programming (GP). This paper describes an approach to the use of while-loop structure in GP for the factorial and the artificial ant problems. Two different forms of the while-loop structure, count-controlled loop and event-controlled loop, are investigated. The results suggest that both forms of the while-loop structure can be successfully evolved in GP, the system with the while-loop structure is more effective and more efficient than the standard GP system for the two problems, and the evolved genetic programs with the loop-structure are much easier to interpret.