GEOMETRIC COMPACTION ON CHANNEL ROUTING

A channel compaction algorithm incorporating via minimization and lateral via shifting is discussed. Bump propagation from the center of vias is the crucial phenomenon preventing compaction results from attaining the lower bound. Via minimization reduces the sources of the bumps, and lateral via shifting splits the critical paths which dominate the height of the channel. We adopt a contour-following approach as the basic operation to compact and straighten each wire. The sequence of the wires is determined by a topological sorting algorithm which also resolves any ordering conflicts by splitting the wires. We test 24 circuits reported by Cong and Xiong. An improvement of up to 22.9% over one-dimensional compaction has been observed. Experiments on various solutions of Deutsch's difficult example indicate no significant relationship between the compacted channel height and the number of tracks in the routing solution. Therefore, we conjecture that the compacted height is affected by the topology of the routing results rather than by the number of tracks.