Discretionary channel routing

Abstract

In the paper, the channel routing model is generalised to incorporate some design flexibilities into the channel routing process. The channel router then makes use of the additional flexibilities to obtain better overall routing solution (and hence more compact layouts). Specifically, the channel routing problem is generalised so that a given net is only required to connect some (not necessarily all) of the pins in that net. The generalised problem is called the discretionary channel routing problem (DCRP). Various applications of the DCRP are presented. Solution of the DCRP involves two phases: the selection phase in which the pins are selected, and the connection phase in which the selected pins are routed. Two classes of algorithms for solving the DCRP are studied. In the first class, a target router is selected and the pins are selected to enhance the performance of that router. In the second class, pins are selected according to some absolute criterion that is independent of the target router. The algorithms have been implemented and tested on various (benchmarks and randomly-generated) problems. For all the test problems, the algorithms produce results that are either nearoptimal or optimal. In particular, excellent results were obtained for all the benchmark problems. Comparisons of these methods are also given, together with recommendations for choice of method for a given situation. Finally, the results show that the additional flexibility in the DCRP model leads to substantial savings in the wiring area, thus leading to more compact layout.