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Abstract:

Shapley's stochastic games and Everett's recursive games are classical models of game theory describing two-player zero-sum games of potentially infinite duration. In this paper we describe algorithms for exactly solving these games. As the values of both kinds of games may be irrational numbers, our algorithms output the value of the game given as input in isolating interval representation. When the number of positions of the game is constant, our algorithms run in polynomial time and are the first algorithms with this property. As a byproduct, we give new improved upper and lower bounds on the algebraic degree of the values of stochastic and recursive games as a function of the combinatorial parameters of the game. As another byproduct, we give a new upper bound on the complexity of the strategy iteration algorithm for concurrent reachability games, a well-studied special case of recursive games. This upper bound is exponential even when the number of positions is constant, but prior to this paper only a doubly exponential upper bound on the complexity of strategy iteration was known, even for this case.

BibTeX:
@InProceedings{hklmt-stoc-2011,
  author =       {Kristoffer Arnsfelt Hansen and Michal Koucky and
                  Niels Lauritzen and Peter Bro Miltersen and Elias~P.
                  Tsigaridas},
  title =        {Exact algorithms for solving stochastic games},
  booktitle =    STOC_2011,
  year =         2011,
  abstract =     "Shapley's stochastic games and Everett's recursive
                  games are classical models of game theory describing
                  two-player zero-sum games of potentially infinite
                  duration.  In this paper we describe algorithms for
                  exactly solving these games. As the values of both
                  kinds of games may be irrational numbers, our
                  algorithms output the value of the game given as
                  input in isolating interval representation. When the
                  number of positions of the game is constant, our
                  algorithms run in polynomial time and are the first
                  algorithms with this property. As a byproduct, we
                  give new improved upper and lower bounds on the
                  algebraic degree of the values of stochastic and
                  recursive games as a function of the combinatorial
                  parameters of the game. As another byproduct, we
                  give a new upper bound on the complexity of the
                  strategy iteration algorithm for concurrent
                  reachability games, a well-studied special case of
                  recursive games. This upper bound is exponential
                  even when the number of positions is constant, but
                  prior to this paper only a doubly exponential upper
                  bound on the complexity of strategy iteration was
                  known, even for this case.",
}

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