Improved Speedup Bounds for Parallel Alpha–Beta Search

In this paper we investigate the “mandatory-work-first” approach to parallel alpha–beta search first proposed by Akl, Barnard, and Doran. This approach is based on a version of alpha–beta search without deep cutoffs and a two-stage evaluation process, the second stage of which is often pruned. Our analysis shows that for best-first ordering on the lookahead tree, this approach provides greater speedup than the Palphabeta tree-splitting technique, and that for worst-first ordering, mandatory work first provides only slightly worse speedup than Palphabeta.