Approximability and Parameterized Complexity of Minmax Values
Kristoffer Arnsfelt Hansen3
, Thomas Dueholm Hansen3
, Peter Bro Miltersen3
and Troels Bjerre Sørensen3 
| (3) |
Department of Computer Science, University of Aarhus, Denmark |
Abstract
We consider approximating the minmax value of a multi-player game in strategic form. Tightening recent bounds by Borgs et al., we observe that approximating the value with a precision of εlogn digits (for any constant ε> 0) is NP-hard, where n is the size of the game. On the other hand, approximating the value with a precision of c loglogn digits (for any constant c ≥ 1) can be done in quasi-polynomial time. We consider the parameterized complexity of the problem, with the parameter being
the number of pure strategies k of the player for which the minmax value is computed. We show that if there are three players, k = 2 and there are only two possible rational payoffs, the minmax value is a rational number and can be computed exactly in linear time. In the general case, we show that the value can be approximated with any polynomial number of digits of accuracy
in time n
O(k). On the other hand, we show that minmax value approximation is W[1]-hard and hence not likely to be fixed parameter tractable. Concretely, we show that if k-Clique requires time n
Ω(k) then so does minmax value computation.
Work supported by Center for Algorithmic Game Theory, funded by the Carlsberg Foundation.
References secured to subscribers.