Length-bounded cuts and flows

  • Authors:
  • Georg Baier;Thomas Erlebach;Alexander Hall;Ekkehard Köhler;Heiko Schilling;Martin Skutella

  • Affiliations:
  • Institute of Mathematics, TU Berlin, Germany;Department of Computer Science, U Leicester, England;Institute of TCS, ETH Zurich, Switzerland;Institute of Mathematics, TU Berlin, Germany;Institute of Mathematics, TU Berlin, Germany;Department of Mathematics, U Dortmund, Germany

  • Venue:
  • ICALP'06 Proceedings of the 33rd international conference on Automata, Languages and Programming - Volume Part I
  • Year:
  • 2006

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Abstract

An L-length-bounded cut in a graph G with source s, and sink t is a cut that destroys all s-t-paths of length at most L. An L-length-bounded flow is a flow in which only flow paths of length at most L are used. We show that the minimum length-bounded cut problem in graphs with unit edge lengths is $\mathcal{NP}$-hard to approximate within a factor of at least 1.1377 for L ≥5 in the case of node-cuts and for L ≥4 in the case of edge-cuts. We also give approximation algorithms of ratio min {L,n/L} in the node case and $\min\{L,n^2/L^2,\sqrt{m}\}$ in the edge case, where n denotes the number of nodes and m denotes the number of edges. We discuss the integrality gaps of the LP relaxations of length-bounded flow and cut problems, analyze the structure of optimal solutions, and present further complexity results for special cases.