PACKER: a switchbox router based on conflict elimination by local transformations

PACKER is an algorithm for switchbox routing, based on a novel approach. In an initial phase, the connectivity of each net is established without taking the other nets into account. In general, this gives rise to conflicts (short circuits). In the second stage, the conflicts are removed iteratively using connectivity-preserving local transformations. They reshape a net by displacing one of its segments without disconnecting it from the net. The transformations are applied in a asystematic way using a scan line technique. The results obtained by PACKER are very positive: it solves all well-known benchmark example

Switchbox routing by stepwise reshaping

An algorithm for switchbox routing called PACKER is presented. In an initial phase, the connectivity of each net is established in a fast way without taking the other nets into account. In general, this gives rise to conflicts (short circuits). In the second stage the conflicts are removed iteratively using connectivity-preserving local transformations. They reshape a net by displacing one of its segments without disconnecting it from the net. The transformations are applied in a systematic way using a scan-line technique. During this process, a subset of the segments at the position of the scan line is densely packed in the (two) layers available for routing. The remaining segments are pushed to the next scan-line position. Scanning in the four available directions (left to right, right to left, top to bottom, and bottom to top) is performed until all conflicts have disappeared or no solution is found within a maximum number of iterations. It turns out that the new approach to routing, as implemented in PACKER, also has practical merits: most of the well-known benchmark examples are solve