Algorithms for permutation channel routing

In this paper the channel routing problem is generalized to allow the interchange of some of the pins in the channel. The generalized problem is called the Permutation Channel Routing Problem (PCRP). This model arises naturally when there are logically equivalent (and therefore interchangeable) pins. Various other applications of the model are also presented. We show that the PCRP is NP-complete for two different cost measures. An optimal algorithm is presented for a special case called the Single Permutable Block Model. For the general PCRP, we study two methods of solution: iterative improvement and simulated annealing. Our results show that allowing some of the pins to be interchanged can lead to a substantial reduction in the number of tracks needed for routing. For example, by randomly generating a few small groups of interchangeable pins, a savings of 42% was obtained for Deutsch's Difficult problem. For all the test problems, our algorithms produce results that are very close to the best possible ones. We also show that our algorithms outperform a previous method by Kobayashi and Drozd.

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