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Multicommodity Demand Flow in a Tree

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Automata, Languages and Programming (ICALP 2003)

Part of the book series: Lecture Notes in Computer Science ((LNCS,volume 2719))

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Abstract

We consider requests for capacity in a given tree network T = (V,E) where each edge of the tree has some integer capacity u e. Each request consists of an integer demand d f and a profit w f which is obtained if the request is satisfied. The objective is to find a set of demands that can be feasibly routed in the tree and which provide a maximum profit. This generalizes well-known problems including the knapsack and b-matching problems.

When all demands are 1, we have the integer multicommodity flow problem. Garg, Vazirani, and Yannakakis [5] had shown that this problem is NP-hard and gave a 2-approximation algorithm for the cardinality case (all profits are 1) via a primal-dual algorithm. In this paper we establish for the first time that the natural linear programming relaxation has a constant factor gap, a factor of 4, for the case of arbitrary profits.

We then discuss the situation for arbitrary demands. When the maximum demand d max is at most the minimum edge capacity u min, we show that the integrality gap of the LP is at most 48. This result is obtained showing that the integrality gap for demand version of such a problem is at most 12 times that for the unit demand case. We use techniques of Kolliopoulos and Stein [8], [9] to obtain this. We also obtain, via this method, improved algorithms for the line and ring networks. Applications and connections to other combinatorial problems are discussed.

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Chekuri, C., Mydlarz, M., Shepherd, F.B. (2003). Multicommodity Demand Flow in a Tree. In: Baeten, J.C.M., Lenstra, J.K., Parrow, J., Woeginger, G.J. (eds) Automata, Languages and Programming. ICALP 2003. Lecture Notes in Computer Science, vol 2719. Springer, Berlin, Heidelberg. https://doi.org/10.1007/3-540-45061-0_34

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  • DOI: https://doi.org/10.1007/3-540-45061-0_34

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  • Print ISBN: 978-3-540-40493-4

  • Online ISBN: 978-3-540-45061-0

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