A Solution to Short PVS Caused by Exact Hash Matches

Article type: Research Article

Authors: Hyatt, Robert M.¹

Affiliations: Birmingham, USA

Note: [1] Computer Science, University of Alabama at Birmingham, Birmingham, USA. Email: hyatt@cis.uab.edu

Abstract: The problem of short principal variations (PVs) due to exact transposition / refutation (ttable) matches has been discussed frequently over the past 50 plus years. Richard Greenblatt introduced the idea of a transposition/refutation table in his 1967 article on Mac Hack, and the topic has since been discussed many times (CCC11, Greenblatt et al., 1967, Slate, 1977). The issue of exact score hash matches creates several problems that have led to draconian solutions that are generally worse than the original problem. For example, the most popular solution is not allowing exact hash matches on PV nodes, which does avoid the short PV problem, but at a computationally expensive cost. We have already reached this position once, and completed a full search. We now have reached it again, but we choose to repeat the search to extract the remainder of the PV, rather than using the ttable information to avoid this search completely. The author describes a simple and effective solution that all but eliminates this problem with no measurable computational cost or loss of efficiency.

DOI: 10.3233/ICG-2014-37307

Journal: ICGA Journal, vol. 37, no. 3, pp. 178-181, 2014