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On the Symbolic Computation of the Hardest Configurations of the RUSH HOUR Game ⋆
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BibTeX
@MISC{Collette_onthe,
author = {Sébastien Collette and Jean-françois Raskin and Frédéric Servais and Université Libre De Bruxelles},
title = {On the Symbolic Computation of the Hardest Configurations of the RUSH HOUR Game ⋆},
year = {}
}
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Abstract
Abstract. RUSH HOUR is a sliding block game where blocks represent cars stuck in a traffic jam on a 6 × 6 board. The goal of the game is to allow one of the cars (the target car) to exit this traffic jam by moving the other cars out of its way. In this paper, we study the problem of finding difficult initial configurations for this game. An initial configuration is difficult if the number of car moves necessary to exit the target car is high. To solve the problem, we model the game in propositional logic and we apply symbolic model-checking techniques to study the huge graph of configurations that underlies the game. On the positive side, we show that this huge graph (containing 3.6 · 10 10 vertices) can be completely analyzed using symbolic model-checking techniques with reasonable computing resources. We have classified every possible initial configuration of the game according to the length of its shortest solution. On the negative side, we prove a general theorem that shows some limits of symbolic model-checking methods for board games. This result explains why some natural modeling of board games leads to the explosion of the size of symbolic data-structures. 1
Keyphrases
rush hour game symbolic computation hardest configuration board game target car huge graph traffic jam symbolic model-checking technique natural modeling block game symbolic data-structures rush hour initial configuration positive side general theorem symbolic model-checking method propositional logic car move possible initial configuration negative side difficult initial configuration
