Provably good moat routing

Moat routing is the routing of nets between the input/output pads and the core circuit. In this paper, it is proved that moat routing is NP-complete under the routing model in which there are no vertical con icts and doglegs are disallowed (i.e., every net is routed within a single track). This contrasts with the fact that channel routing is e ciently solvable under these restrictions. The paper then presents an approximation algorithm for moat routing that computes moat routing solutions that are guaranteed to use at most three times the optimal number of tracks. Empirical results are presented indicating that for a number of industrial benchmarks, the algorithm produces solutions that are near optimal and that use signi cantly fewer tracks than previous moat routing strategies.