International Workshop on Approximation and Online Algorithms

Approximation and Online Algorithms pp 47-58 | Cite as

Tight Bounds for Double Coverage Against Weak Adversaries

  • Nikhil Bansal
  • Marek Eliáš
  • Łukasz Jeż
  • Grigorios Koumoutsos
  • Kirk Pruhs
Conference paper
Part of the Lecture Notes in Computer Science book series (LNCS, volume 9499)


We study the Double Coverage (DC) algorithm for the k-server problem in the (hk)-setting, i.e. when DC with k servers is compared against an offline optimum algorithm with \(h \le k\) servers. It is well-known that DC is k-competitive for \(h=k\). We prove that even if \(k>h\) the competitive ratio of DC does not improve; in fact, it increases up to \(h+1\) as k grows. In particular, we show matching upper and lower bounds of \(\frac{k(h+1)}{k+1}\) on the competitive ratio of DC on any tree metric.


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Copyright information

© Springer International Publishing Switzerland 2015

Authors and Affiliations

  • Nikhil Bansal
    • 1
  • Marek Eliáš
    • 1
  • Łukasz Jeż
    • 1
    • 2
  • Grigorios Koumoutsos
    • 1
  • Kirk Pruhs
    • 3
  1. 1.Eindhoven University of TechnologyEindhovenThe Netherlands
  2. 2.Institute of Computer ScienceUniversity of WrocławWrocławPoland
  3. 3.University of PittsburghPittsburghUSA

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