CRACKER: a general area router based on stepwise reshaping

CRACKER is an algorithm able to handle a large class of routing problems. Operating on a grid and using two wiring layers, it can deal with floating and fixed terminals, arbitrarily located in the routing area, and with obstacles in either of the two layers. The routing process consists of two stages. In the first stage, all nets are interconnected quickly, without avoiding conflicts with previously routed nets or obstacles. In the iterative second stage, connectivity-preserving local transformations are applied in a systematic way, such that, eventually, a solution without conflict is reached. There is no rip-up and reroute. The same algorithm is able to solve well-known examples of switchbox routing, routing with irregular boundaries, L-shaped channels, three-sided channels, etc.<>