Alternating traps in Muller and parity games

  • Authors:
  • Andrey Grinshpun;Pakawat Phalitnonkiat;Sasha Rubin;Andrei Tarfulea

  • Affiliations:
  • Department of Mathematics, Massachusetts Institute of Technology, Cambridge, MA, United States;Department of Mathematics, Cornell University, Ithaca, NY, United States;IST Austria and TU Vienna, Austria;Department of Mathematics, Princeton University, Princeton, NJ, United States

  • Venue:
  • Theoretical Computer Science
  • Year:
  • 2014

Quantified Score

Hi-index 5.23

Visualization

Abstract

Muller games are played by two players moving a token along a graph; the winner is determined by the set of vertices that occur infinitely often. The central algorithmic problem is to compute the winning regions for the players. Different classes and representations of Muller games lead to problems of varying computational complexity. One such class are parity games; these are of particular significance in computational complexity, as they remain one of the few combinatorial problems known to be in NP @? co-NP but not known to be in P. We show that winning regions for a Muller game can be determined from the alternating structure of its traps. To every Muller game we then associate a natural number that we call its trap depth; this parameter measures how complicated the trap structure is. We present algorithms for parity games that run in polynomial time for graphs of bounded trap depth, and in general run in time exponential in the trap depth.