k-Layer Straightline Crossing Minimization by Speeding Up Sifting
Recently, a technique called sifting has been proposed for k-layer straightline crossing minimization. This approach outperforms the traditional layer by layer sweep based heuristics by far when applied to k-layered graphs with k≥3. In this paper, we present two methods to speed up sifting. First, it is shown how the crossing matrix can be computed and updated efficiently. Then, we study lower bounds which can be incorporated in the sifting algorithm, allowing to prune large parts of the search space. Experimental results show that it is possible to speed up sifting by more than a factor of 20 using the new methods.
- 2.R. Drechsler and W. Günther. Using lower bounds during dynamic BDD minimization. In Design Automation Conf., pages 29–32, 1999.Google Scholar
- 6.C. Matuszewski, R. Schönfeld, and P. Molitor. Using sifting for k-layer straightline crossing minimization. In Graph Drawing Conference, LNCS 1731, pages 217–224, 1999.Google Scholar
- 7.K. Mehlhorn and S. Näher. The Leda Platform of Combinatorial and Geometric Computing. Cambridge University Press, 1999. Project home page at http://www.mpi-sb.mpg.de/LEDA/.
- 9.S. Panda and F. Somenzi. Who are the variables in your neighborhood. In Int’l Conf. on CAD, pages 74–77, 1995.Google Scholar
- 10.R. Rudell. Dynamic variable ordering for ordered binary decision diagrams. In Int’l Conf. on CAD, pages 42–47, 1993.Google Scholar