Approximating the minmax value of three-player games within a constant is as hard as detecting planted cliques

  • Authors:
  • Kord Eickmeyer;Kristoffer Arnstfelt Hansen;Elad Verbin

  • Affiliations:
  • National Institute of Informatics, Tokyo, Japan;Aarhus University, Denmark;Aarhus University, Denmark

  • Venue:
  • SAGT'12 Proceedings of the 5th international conference on Algorithmic Game Theory
  • Year:
  • 2012

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Abstract

We consider the problem of approximating the minmax value of a multi-player game in strategic form. We argue that in three-player games with 0-1 payoffs, approximating the minmax value within an additive constant smaller than ξ/2, where $\xi = \frac{3-\sqrt5}{2} \approx 0.382$, is not possible by a polynomial time algorithm. This is based on assuming hardness of a version of the so-called planted clique problem in Erdős-Rényi random graphs, namely that of detecting a planted clique. Our results are stated as reductions from a promise graph problem to the problem of approximating the minmax value, and we use the detection problem for planted cliques to argue for its hardness. We present two reductions: a randomised many-one reduction and a deterministic Turing reduction. The latter, which may be seen as a derandomisation of the former, may be used to argue for hardness of approximating the minmax value based on a hardness assumption about deterministic algorithms. Our technique for derandomisation is general enough to also apply to related work about ε-Nash equilibria.