APHID: Asynchronous Parallel Game-Tree Search

Most parallel game-tree search approaches use synchronous methods, where the work is concentrated within a specific part of the tree, or at a given search depth. This article shows that asynchronous game-tree search algorithms can be as efficient as or better than synchronous methods in determining the minimax value. APHID, a new asynchronous parallel game-tree search algorithm, is presented. APHID is implemented as a freely-available portable library, making the algorithm easy to integrate into a sequential game-tree searching program. APHID has been added to four programs written by different authors. APHID yields better speedups than synchronous search methods for an Othello and a checkers program, and comparable speedups on two chess programs.