摘要
In this paper we consider two channel pin assignment problems which take circuit performance into account. The first one is the module implementation selection problem. We are given a net span bound for each critical net and each module has several possible placements of its pins. Our objective is to minimize channel density while satisfying net span constraints. We proved that this problem is NP-complete. For the case when each module has at most 2 pin placements, the problem can be transformed to the 2-SAT problem and hence is polynomial time solvable. We present a heuristic based on this algorithm to solve the general case. The second problem we consider is the module shifting problem. We are given a set of modules whose relative ordering is fixed on each side of the channel but their exact positions are not fixed. We present a polynomial time algorithm to test the feasibility of satisfying the net span constraints by shifting the modules. The algorithm is based on formulating the problem as a special integer linear programming problem which is solvable in polynomial time. We also extend our algorithms to handle multiple channels