Optimal algorithms for bubble sort based non-Manhattan channel routing

It has been pointed out that, in many cases, results generated by non-Manhattan channel routers will be better than those generated by Manhattan routers. Non-optimal bubble sort based algorithms for non-Manhattan channel routing have been proposed in the literature by also allowing connections in the +45/spl deg/ and /spl minus/45/spl deg/ directions. In this paper, optimal algorithms are proposed for the two-layer and three-layer non-Manhattan channel routing problems based on an identical problem formulation. The time complexities of our algorithms and the existing algorithm (which produces the best results so far) are O(K/sup 2/ * N) and O(K * N/sup 2/), respectively, where N is the number of terminals (i.e., the length) of the channel and N is the number of routing tracks (i.e., the height) in the channel. K is always less than N, and in most cases is much smaller than N. Clearly, a significant improvement in time complexity over the existing algorithm (which produces the best results so far) is achieved, while ensuring optimality.<
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