A polylogarithmic approximation for computing non-metric terminal Steiner trees.
ABSTRACT The main contribution of this short note is to provide improved bounds on the approximability of constructing terminal Steiner trees in arbitrary undirected graphs. Technically speaking, our results are obtained by relating this computational task to that of computing group Steiner trees. As a secondary objective, we make a concentrated effort to distinguish between the factor by which constructed trees exceed the optimal backbone cost and between the deviation from the optimal terminal linking cost.
SourceAvailable from: Ryan Ryan Williams
Chapter: Approximation Algorithms[Show abstract] [Hide abstract]
ABSTRACT: Most interesting real-world optimization problems are very challenging from a computational point of view. In fact, quite often, finding an optimal or even a near-optimal solution to a large-scale optimization problem may require computational resources far beyond what is practically available. There is a substantial body of literature exploring the computational properties of optimization problems by considering how the computational demands of a solution method grow with the size of the problem instance to be solved (see e.g. Chapter 11 or Aho et al., 1979). A key distinction is made between problems that require computational resources that grow polynomially with problem size versus those for which the required resources grow exponentially. The former category of problems are called efficiently solvable, whereas problems in the latter category are deemed intractable because the exponential growth in required computational resources renders all but the smallest instances of such problems unsolvable.03/2006: pages 557-585;
Conference Paper: Polylogarithmic inapproximability.[Show abstract] [Hide abstract]
ABSTRACT: We provide the first hardness result of a polylogarithmic approximation ratio for a natural NP-hard optimization problem. We show that for every fixed ε>0, the GROUP-STEINER-TREE problem admits no efficient log2-ε k approximation, where k denotes the number of groups (or, alternatively, the input size), unless NP has quasi polynomial Las-Vegas algorithms. This hardness result holds even for input graphs which are Hierarchically Well-Separated Trees, introduced by Bartal [FOCS, 1996]. For these trees (and also for general trees), our bound is nearly tight with the log-squared approximation currently known. Our results imply that for every fixed ε>0, the DIRECTED-STEINER TREE problem admits no log2-ε n--approximation, where n is the number of vertices in the graph, under the same complexity assumption.Proceedings of the 35th Annual ACM Symposium on Theory of Computing, June 9-11, 2003, San Diego, CA, USA; 01/2003
Article: The full Steiner tree problem[Show abstract] [Hide abstract]
ABSTRACT: Motivated by the reconstruction of phylogenetic tree in biology, we study the full Steiner tree problem in this paper. Given a complete graph G=(V,E) with a length function on E and a proper subset R⊂V, the problem is to find a full Steiner tree of minimum length in G, which is a kind of Steiner tree with all the vertices of R as its leaves. In this paper, we show that this problem is NP-complete and MAX SNP-hard, even when the lengths of the edges are restricted to either 1 or 2. For the instances with lengths either 1 or 2, we give a -approximation algorithm to find an approximate solution for the problem.Theoretical Computer Science 09/2003; 306(1-3-306):55-67. DOI:10.1016/S0304-3975(03)00209-3 · 0.52 Impact Factor