A robust channel router

A robust channel router with simple heuristics is discussed. This router is able to handle two-layer channels, three-layer channels with two horizontal layers and one vertical layer (HVH), and three-layer channels with two vertical layers and one horizontal layer (VHV). This router uses horizontal layers only for horizontal wires and the vertical layer only for vertical wires. It is robust in the sense that small changes in the input or in the algorithm do not have a major effect on the results, which is a key feature of its ability to support the wide variety of routing models. The Deutsch difficult example, which has a channel density of 19, was routed in 19 tracks on two layers and in 10 tracks on three layers, with no stacked vias