Evolving Control Structures with Automatically De ned

Koza has previously shown that the power of a genetic programming system can often be enhanced by allowing for the simultaneous evolution of a main program and a collection of automatically deened functions (ADFs). In this paper I show how related techniques can be used to simultaneously evolve a collection of automatically deened macros (ADMs). I show how ADMs can be used to produce new control structures during the evolution of a program, and I present data showing that ADMs sometimes provide a greater beneet than do ADFs. I discuss the characteristics of problems that may beneet most from the use of ADMs, or from architectures that include both ADFs and ADMs, and I discuss directions for further research .