Approximation of Boolean Functions by Local Search

Usually, local search methods are considered to be slow. In ourpaper, we present a simulated annealing-based local search algorithm for the approximation of Boolean functions with a proven time complexity that behaves relatively fast on randomly generated functions. The functions are represented by disjunctive normal forms (DNFs). Given a set of m uniformly distributed positive and negative examples of length n generated by a target function F(x1,..., xn), where the DNF consists of conjunctions with at most ℓ literals only, the algorithm computes with high probability a hypothesis H of length m · ℓ such that the error is zero on all examples. Our algorithm can be implemented easily and we obtained a relatively high percentage of correct classifications on test examples that were not presented in the learning phase. For example, for randomly generated F with n = 64 variables and a training set of m = 16384 examples, the error on the same number of test examples was about 19% on positive and 29% on negative examples, respectively. The proven complexity bound provides the basis for further studies on the average case complexity.