Recursive channel router

An extended true vertical-horizontal-vertical (VHV)-model three-layer channel routing algorithm is described. The algorithm is based on the observation that, after routing a track on either the top or bottom side of the channel, it is possible to define a new channel routing problem and call the router recursively. The routing task then is reduced to making optimal use of a track. Routing of track is done in two steps. For the first step, the authors present a segment selection method, which aims at reducing the channel density. The second step further fills up the track and, at the same time, aims at reducing the heights of the vertical constraint graphs