Extended Null-Move Reductions

Abstract. In this paper we review the conventional versions of nullmove pruning, and present our enhancements which allow for a deeper search with greater accuracy. While the conventional versions of nullmove pruning use reduction values of R 3, we use an aggressive reduction value of R = 4 within a verified adaptive configuration which maximizes the benefit from the more aggressive pruning, while limiting its tactical liabilities. Our experimental results using our grandmasterlevel chess program, Falcon, show that our null-move reductions (NMR) outperform the conventional methods, with the tactical benefits of the deeper search dominating the deficiencies. Moreover, unlike standard null-move pruning, which fails badly in zugzwang positions, NMR is impervious to zugzwangs. Finally, the implementation of NMR in any program already using null-move pruning requires a modification of only a few lines of code.

• Type: Conference
• Year: 2008
• Where: CG
• Authors: Omid David-Tabibi, Nathan S. Netanyahu
• Keywords: CG 2008, Computer Graphics, Conventional Versions, Null-move Pruning, Nullmove Pruning