Min-cost multiflows in node-capacitated undirected networks

  • Authors:
  • Maxim A. Babenko;Alexander V. Karzanov

  • Affiliations:
  • Department of Mechanics and Mathematics, Moscow State University, Moscow, Russia 119991;Institute for System Analysis of the RAS, Moscow, Russia 117312

  • Venue:
  • Journal of Combinatorial Optimization
  • Year:
  • 2012

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Abstract

We consider an undirected graph G=(VG,EG) with a set T驴VG of terminals, and with nonnegative integer capacities c(v) and costs a(v) of nodes v驴VG. A path in G is a T-path if its ends are distinct terminals. By a multiflow we mean a function F assigning to each T-path P a nonnegative rational weight F(P), and a multiflow is called feasible if the sum of weights of T-paths through each node v does not exceed c(v). The value of F is the sum of weights F(P), and the cost of F is the sum of F(P) times the cost of P w.r.t. a, over all T-paths P.Generalizing known results on edge-capacitated multiflows, we show that the problem of finding a minimum cost multiflow among the feasible multiflows of maximum possible value admits half-integer optimal primal and dual solutions. Moreover, we devise a strongly polynomial algorithm for finding such optimal solutions.