On the approximation performance of fictitious play in finite games

  • Authors:
  • Paul W. Goldberg;Rahul Savani;Troels Bjerre Sørensen;Carmine Ventre

  • Affiliations:
  • Department of Computer Science, University of Liverpool, UK;Department of Computer Science, University of Liverpool, UK;Department of Computer Science, University of Warwick, UK;Department of Computer Science, University of Liverpool, UK

  • Venue:
  • ESA'11 Proceedings of the 19th European conference on Algorithms
  • Year:
  • 2011

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Abstract

We study the performance of Fictitious Play, when used as a heuristic for finding an approximate Nash equilibrium of a two-player game. We exhibit a class of two-player games having payoffs in the range [0, 1] that show that Fictitious Play fails to find a solution having an additive approximation guarantee significantly better than 1/2. Our construction shows that for n × n games, in the worst case both players may perpetually have mixed strategies whose payoffs fall short of the best response by an additive quantity 1/2-O(1/n1-δ) for arbitrarily small δ. We also show an essentially matching upper bound of 1/2 - O(1/n).