Author: Artem Pyatakov
Date: 22:15:31 03/31/04
Hello again CCC, I've been doing some simple last-minute experiments for my thesis, and stumbled onto this interesting idea. It's in the area of the killer move heuristic. My original engine (the one I wrote 3 years ago), used the same killer move scheme as the one used by Crafty (2 killers per ply). As I mentioned in my previous post, I began experimenting with using the moves from plies ply-2, ply-4 and ply+2 as well, with very nice results (about 3% tree size reduction on both WAC and Bratko-Kopec). I decided to then go further and implemented this scheme: In addition to the regular Crafty-style (replace-always) killers, I decided to add a limited number of killer moves on each ply that where the least "popular" killer move would be replaced in favor of the new. I tried different numbers of these popularity-based moves (starting with 10), but it seemed that (with a very small dataset of a couple problems) the optimal number of these additional killers was only 2. With these additions, I ran the WAC and Bratko-Kope testsuites and found they had reduced the node count by 8%, which I was excited about. Yes, these results need to be taken with a grain of salt. Yes, this is not even my original program - but one that I actually made simpler (and dumber) by taking out a lot of chess-specific heuristics. But I still think this is a promising result. Someone else care to try this in their engine? Any comments? Artem
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