On parallel evaluation of game trees

  • Authors:
  • Richard M. Karp;Yangun Zhang

  • Affiliations:
  • Univ. of Washington, Seattle;SABRE Group, Southlake, TX

  • Venue:
  • Journal of the ACM (JACM)
  • Year:
  • 1998

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Abstract

A class of parallel algorithms for evaluating game trees is presented. These algorithms parallelize a standard sequential algorithm for evaluating AND/OR trees and the &agr;-&bgr; pruning procedure for evaluating MIN/MAX trees. It is shown that, uniformly on all instances of uniform AND/OR trees, the parallel AND/OR tree algorithm achieves an asymptotic linear speedup using a polynomial number of processors in the height of the tree. The analysis of linear speedup using more than a linear number of processors is due to J. Harting. A numerical lower bound rigorously establishes a good speedup for the uniform AND/OR trees with parameters that are typical in practice. The performance of the parallel &agr;-&bgr; algorithm on best-ordered MIN/MAX trees is analyzed.