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.<>