Cofactoring-Based Upper Bound Computation for Covering Problems

This paper introduces an efficient technique to compute a tight upper bound for the unate and binate covering problems. It is known that a covering problem can be solved by finding a shortest path on a BDD representing a satisfiability formula. Our technique is based on finding an approximation to the shortest path by identifying a path on a BDD composed of as many negative edges as possible. This operation is performed by iterative cofactoring without actually building a BDD. The results show that our technique generates very tight upper bound, with more than half of the test cases resulting in the optimum solution in just a few iterations.