Breaking cycles and vertical constraints in Deutsch's new and more difficult channel-routing problems

In the past decade, D. Deutsch's (1976) difficult example has been used extensively as a benchmark to test various channel-routing algorithms. Since more and more channel routers are able to achieve an optimal or near-optimal solution for the original difficult example. Deutsch recently (1989) proposed two new and more difficult channel-routing problems to provide new challenges for researchers in this area. Due to off-grid terminal locations in the new examples, the number of vertical constraints are almost doubled, and many cycles are present in the vertical constraint graph. A gridless channel router which intelligently generates doglegs to break cycles and vertical constraints and successfully completes the routing of Deutsch's new and more difficult examples is presented. This gridless router is among the first routers to report results on these new benchmarks.<
>