cient Algorithms for the Minimum Shortest Path Steiner

Given an undirected graph G = (V;E) with positive edge weights (lengths) w : E ! <, a set of terminals (sinks) N V , and a unique root node r 2 N , a shortest-path Steiner arborescence (simply called an arborescence in the following) is a Steiner tree rooted at r spanning all terminals in N such that every sourceto-sink path is a shortest path in G. Given a triple (G;N; r), the MinimumShortest-Path Steiner Arborescence (MSPSA) problem seeks an arborescence with minimum weight. The MSPSA problem has various applications in the areas of VLSI physical design, multicast network communication, and supercomputer message routing; various cases have been studied in the literature. In this paper, we propose several heuristics and exact algorithms for the MSPSA problem with applications to VLSI physical design. Experiments indicate that our heuristics generate near-optimal results and achieve speedups of orders of magnitude over existing algorithms.