- Artist's concept of the Phoenix Mars lander by NASA/JPL/Corby Waste, from Phoenix Mars Mission - Gallery - Images, Wikimedia Commons, Mars-Scout-Programm from Wikipedia.de↩︎
Scout,
an Alpha-Beta enhancement introduced by Judea Pearl in 1980 1 2 . 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 3 .
Enhancements
In 1983 Alexander Reinefeld turned Scout and Negamax with some fail-soft refinements into NegaScout 4 . Already in 1982, Tony Marsland and Murray Campbell introduced PVS 5 , based on Finkel's and Fishburn's routine Palphabeta 6 , in Fishburn's 1981 Thesis 7 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, [https://en.wikipedia.org/wiki/Washington,_D.C. Washington D.C.], 2011, YouTube Video
References
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↩︎
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↩︎
Alexander Reinefeld (1983). An Improvement to the Scout Tree-Search Algorithm. ICCA Journal, Vol. 6, No. 4↩︎
Tony Marsland, Murray Campbell (1982). Parallel Search of Strongly Ordered Game Trees. ACM Computing Surveys, Vol. 14, No. 4, 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, Calphabeta at page 167↩︎