Note: [1] Department of Computer Science, Bar-Ilan University, Ramat-Gan 52900, Israel, Email: davoudo@cs.biu.ac.il. Http://www.cs.biu.ac.il/davoudo
Note: [2] Department of Computer Science, Bar-Ilan University, Ramat-Gan 52900, Israel, Email: nathan@cs.biu.ac.il, and Center for Automation Research, University of Maryland, College Park, MD 20742, USA, Email: nathan@cfar.umd.edu.
Abstract: In this article we review standard null-move pruning and introduce our extended version of it, which we call verified null-move pruning. In verified null-move pruning, whenever the shallow null-move search indicates a fail-high, instead of cutting off the search from the current node, the search is continued with reduced depth. Our experiments with verified null-move pruning show that on average, it constructs a smaller search tree with greater tactical strength in comparison to standard null-move pruning. Moreover, unlike standard null-move pruning, which fails badly in zugzwang positions, verified null-move pruning manages to detect most zugzwangs and in such cases conducts a re-search to obtain the correct result. In addition, verified null-move pruning is very easy to implement, and any standard null-move pruning program can use verified null-move pruning by modifying only a few lines of code.
DOI: 10.3233/ICG-2002-25305
Journal: ICGA Journal, vol. 25, no. 3, pp. 153-161, 2002
