Minimum Weakly Fundamental Cycle Bases Are Hard To Find

  • Authors:
  • Romeo Rizzi

  • Affiliations:
  • Università degli Studi di Udine, Dipartimento di Matematica e Informatica, Facoltà di Ingegneria, Via delle Scienze, 208, I-33100, Udine, Italy

  • Venue:
  • Algorithmica
  • Year:
  • 2009

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Abstract

In the last years, new variants of the minimum cycle basis (MCB) problem and new classes of cycle bases have been introduced, as motivated by several applications from disparate areas of scientific and technological inquiry. At present, the complexity status of the MCB problem is settled only for undirected, directed, and strictly fundamental cycle bases (SFCBs). Weakly fundamental cycle bases (WFCBs) form a natural superclass of SFCBs. A cycle basis of a graph G is a WFCB iff ½=0 or there exists an edge e of G and a circuit C i in such that is a WFCB of Ge. WFCBs still possess several of the nice properties offered by SFCBs. At the same time, several classes of graphs enjoying WFCBs of cost asymptotically inferior to the cost of the cheapest SFCBs have been found and exhibited in the literature. Considered also the computational difficulty of finding cheap SFCBs, these works advocated an in-depth study of WFCBs. In this paper, we settle the complexity status of the MCB problem for WFCBs (the MWFCB problem). The problem turns out to be -hard. However, in this paper, we also offer a simple and practical 2⌈log 2 n⌉-approximation algorithm for the MWFCB problem. In O(n ν) time, this algorithm actually returns a WFCB whose cost is at most 2⌈log 2 n⌉∑e∈E(G) w e, thus allowing a fast 2⌈log 2 n⌉-approximation also for the MCB problem. With this algorithm, we provide tight bounds on the cost of any MCB and MWFCB.