New primal-dual algorithms for Steiner tree problems

13 years 4 months ago

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We present new primal-dual algorithms for several network design problems. The problems considered are the generalized Steiner tree problem (GST), the directed Steiner tree problem (DST), and the set cover problem (SC) which is a subcase of DST. All our problems are NP-hard; so we are interested in approximation algorithms for them. First we give an algorithm for DST which is based on the traditional approach of designing primal-dual approximation algorithms. We show that the approximation factor of the algorithm is k, where k is the the number of terminals, in the case when the problem is restricted to quasibipartite graphs. We also give pathologically bad examples for the algorithm performance. To overcome the problems exposed by the bad examples, we design a new framework for primal-dual algorithms which can be applied to all of our problems. The main feature of the new approach is that, unlike the traditional primal-dual algorithms, it keeps the dual solution in the interior of th...

Vardges Melkonian

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