Author: Chris Moreton
Date: 18:22:28 01/16/99
I am in the process of conduction a number of tests regarding the performance of alpha-beta and its various enhancements using Rival. Clearly a wealth of information and publications exist already on this subject and it may be considered no longer interesting but my reasons are also to see how much effect other search parameters have on the engine, notably, the quiescense search and search extensions. The tests searching the 10 nunn positions to depths 2 thru 7 for various combinations of AB enhancements. The question I would like to ask regards the history heuristic. Jonathon Schaeffer's work on the HH (The HH and AB search enhancments in practice) shows that it provides significant gains when applied to plain AB with no knowledge move ordering and slightly more gains when used in conjunction with knowledge ordering. JS mentions that in his test program that there was a certain amount of move ordering even when no knowledge was applied (e.g. capture moves were generated first). My results indicate that when the move order is fully randomised, the HH has no positive effect on node count when added to plain AB, often exceeding the pure AB figure. Other results from my tests regarding the HH seem consistent with JS's observations and show that at least up until depth 7, HH outperforms a transposition table with approx. 300,000 entries when applied to AB+Knowledge ordering + Minimal Window searching. Am I implementing the HH incorrectly, or are these results consistent with others observations? Chris
This page took 0.01 seconds to execute
Last modified: Thu, 15 Apr 21 08:11:13 -0700
Current Computer Chess Club Forums at Talkchess. This site by Sean Mintz.