Evolution of Binary Decision Diagrams for Digital Circuit Design Using Genetic Programming

This paper proposes the methodology for hardware evolution by genetic programming (GP). By adopting Binary Decision Diagrams (BDDs) as hardware representation, larger circuits can be evolved, and they will be easily verified by utilizing commercial CAD software. The hardware descriptions specified in BDDs are improved by GP operators, to synthesize various combinatorial logical circuits. From the viewpoint of GP, however, some constraints of BDD must be satisfied during its search process. In other words, GP must search not only in phenotype space, but also in genotype space. In order to resolve this problem, in this paper, we attempt two approaches. One concerns the operations to obtain BDDs satisfying the genotypical constraints, and the other is the method for balancing phenotypic and genotypic evaluations.