Author: Steve Timson
Date: 01:51:37 06/13/01
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>when I am trying to leech rating points from ChesterX. ;) Hey! Heh. Chester's book is very simple. It also is an in memory hash table (that resolves collisions). I just store a hash key and then win, draw, loss counts (from the PGN and learned separately). When playing I do a 1 deep search into the book basically. Play each legal move at the root, look up the position in the book and save it with its counts if it is there. Then I take the set of all hits into the book and use them to choose a move. I just use wins + draws/2 as a weight and choose randomly (ignoring the losses just means it is effectively a combination of frequency and winning %). I have a parameter that will multiply the weights and make it more likely to choose better lines. Against humans it is 1 (so it plays with quite a bit of variation) and against comps it is 2, to keep from playing crazy lines against comps quite so often. I also have a tournament mode where I raise the multiplier even higher, and limit the random number selection such that low probability lines have no chance of being chosen. This is extremely simple and really easy to get going. I too, however, have been thinking about moving to an on disk book after watching monsoon outbook chester game after game.. :) - Steve
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