The Innuence of Domain Properties on the Performance of Real-time Search Algorithms
The views and conclusions contained in this document are those of the authors and should not be interpreted as representing the oocial policies, either expressed or implied, of the sponsoring organizations. Abstract In this report, we investigate the innuence of domain properties on the performance of real-time search algorithms. We study uninformed, revolving real-time search algorithms with minimal lookahead that solve suboptimal search problems, for example variants of Korf's LRTA* algorithm and edge counting (these algorithms have been used successfully in the literature). We demonstrate, both theoretically and experimentally , that they can search Eulerian domains (a superset of undirected domains) very easily: even the real-time search algorithms that can be intractable are always ef-cient in Eulerian domains. Because traditional real-time search testbeds (such as the eight puzzle and gridworlds) are Eulerian, they cannot be used to distinguish between eecient and ineecient real-time search algorithms. It follows that one has to use non-Eulerian domains to demonstrate the superiority of a real-time search algorithm across a wide range of domains { the studied real-time search algorithms diier in this respect from traditional search algorithms. To this end, we describe two classes of domains (\reset state spaces" and \quicksand state spaces") that do not suuer as much from the problems of the standard test domains and demonstrate the performance of various real-time search algorithms in them.