Maximizing pin alignment by pin permutations

The problem considered here is that of permuting the pins of modules in order to maximize the number of connections which can be achieved in the polysilicon level. Using a graph-theoretic formulation, the problem is shown to be equivalent to that of removing fewest edges in a certain graph to break all cycles. The problem is proved to be NP-complete. A heuristic based on branch-and-bound is proposed. © 1984.