Primal-dual approaches to the Steiner problem

  • Authors:
  • Tobias Polzin;Siavash Vahdati Daneshmand

  • Affiliations:
  • -;-

  • Venue:
  • APPROX '00 Proceedings of the Third International Workshop on Approximation Algorithms for Combinatorial Optimization
  • Year:
  • 2000

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Abstract

We study several old and new algorithms for computing lower and upper bounds for the Steiner problem in networks using dual-ascent and primal-dual strategies. We show that none of the known algorithms can both generate tight lower bounds empirically and guarantee their quality theoretically; and we present a new algorithm which combines both features. The new algorithm has running time O(re log n) and guarantees a ratio of at most two between the generated upper and lower bounds, whereas the fastest previous algorithm with comparably tight empirical bounds has running time O(e2) without a constant approximation ratio. Furthermore, we show that the approximation ratio two between the bounds can even be achieved in time O(e + n log n), improving the previous time bound of O(n2 log n).