On the k-server conjecture

  • Authors:
  • Elias Koutsoupias;Christos H. Papadimitriou

  • Affiliations:
  • Univ. of California at Los Angeles, Los Angeles;Univ. of California at San Diego, La Jolla

  • Venue:
  • Journal of the ACM (JACM)
  • Year:
  • 1995

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Abstract

We prove that the work function algorithm for the k-server problem has a competitive ratio at most 2k−1. Manasse et al. [1988] conjectured that the competitive ratio for the k-server problem is exactly k (it is trivially at least k); previously the best-known upper bound was exponential in k. Our proof involves three crucial ingredients: A quasiconvexity property of work functions, a duality lemma that uses quasiconvexity to characterize the configuration that achieve maximum increase of the work function, and a potential function that exploits the duality lemma.