ALPHA-BETA-CONSPIRACY SEARCH¹

Article type: Research Article

Authors: McAllester, David^{; 2} | Yuret, Denize^{; 3}

Affiliations: New Providence NJ, USA

Note: [1] This article is a republication of an internal report by the same authors published under the same title. The authors have given permission for republication. The report is frequently cited by insiders but rather unknown to others. Therefore we believe that this republication serves our readers (-Ed.).

Note: [2] AutoReason, 85 Magnolia Drive, New Providence NJ 07974, USA. Email: mcallester@autoreason.com

Note: [3] Koc University, Rumeli Feneri Yolu, 80910 Sariyer, Istanbul, Turkey. Email: dyuret@ku.edu.tr

Abstract: We introduce a variant of α-β search in which each node is associated with two depths rather than one. The purpose of α-β search is to find strategics for each player that together establish a value for the root position. A max strategy establishes a lower bound and the min strategy establishes an upper bound. It has long been observed that forced moves should be searched more deeply. Here we make the observation that in the max strategy we are only concerned with the forcedness of max moves and in the min strategy we are only concerned with the forcedness of min moves. This leads to two measures of depth — one for each strategy — and to a two-depth variant of α-β called ABC search. The two-depth approach can be formally derived from conspiracy theory and the structure of the ABC procedure is justified by two theorems relating ABC search and conspiracy numbers.

DOI: 10.3233/ICG-2002-25103

Journal: ICGA Journal, vol. 25, no. 1, pp. 16-35, 2002