Scout

Home * Search * Scout



Scout, an Alpha-Beta enhancement introduced by Judea Pearl in 1980. Scout was originally introduced by a recursive function called EVAL, with {MAX, MIN} -parameter. A boolean function called TEST was used to prove all siblings of the first brother were either below or equal to MAX so far, or above or equal to MIN. If a condition did not hold, a re-search was necessary to get the real new MAX or MIN value. This was essentially a null-window search, with the idea that the saved nodes of the TEST would outweigh re-searches in reasonable well-ordered search trees. Therefor Pearl expected Scout's superiority over Alpha-Beta in practical game trees, which was confirmed in 1985 by Rajjan Shinghal and Agata Muszycka-Jones.

=Enhancements= In 1983 Alexander Reinefeld turned Scout and Negamax with some fail-soft refinements into NegaScout. Already in 1982, Tony Marsland and Murray Campbell introduced PVS, based on Finkel's and Fishburn's routine Palphabeta , in Fishburn's 1981 Thesis called Calphabeta, which in turn is similar to Judea Pearl's Scout.

=See also=
 * Alpha-Beta
 * Iterative Deepening
 * Jamboree
 * Move Ordering
 * MTD(f)
 * NegaScout
 * Null Window
 * Parallel Search
 * Principal Variation Search
 * PVS and Aspiration

=Publications=
 * Judea Pearl (1980). Asymptotic Properties of Minimax Trees and Game-Searching Procedures. Artificial Intelligence, Vol. 14, No. 2
 * Judea Pearl (1980). Scout: A Simple Game-Searching Algorithm with Proven Optimal Properties. Proceedings of the First Annual National Conference on Artificial Intelligence. Stanford. pdf
 * Raphael Finkel, John Philip Fishburn (1980). Parallel Alpha-Beta Search on Arachne. IEEE International Conference on Parallel Processing, pp. 235-243
 * John Philip Fishburn (1981). Analysis of Speedup in Distributed Algorithms Ph.D. Thesis, University of Wisconsin-Madison, pdf
 * Tony Marsland, Murray Campbell (1982). Parallel Search of Strongly Ordered Game Trees. ACM Computing Surveys, Vol. 14, No. 4, pdf
 * Alexander Reinefeld (1983). An Improvement to the Scout Tree-Search Algorithm. ICCA Journal, Vol. 6, No. 4
 * Agata Muszycka-Jones, Rajjan Shinghal (1985). An empirical comparison of pruning strategies in game trees. IEEE Transactions on Systems, Man, and Cybernetics, Vol. 15, No. 3
 * Yanjun Zhang (1998). The Variance of Two Game Tree Algorithms. Journal of Algorithms, Vol. 28, No. 1

=External Links=
 * Scout from Wikipedia
 * Flat Earth Society - Psychoscout, John F. Kennedy Center for the Performing Arts, Washington D.C., 2011, YouTube Video

=References=

Up one level