Author: Norm Pollock
Date: 11:33:33 01/06/05
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On January 06, 2005 at 13:20:27, Eric Oldre wrote: >I have added the ability to add opening books to my latest version of Latista. >I'll release it once I create a decent opening and add a couple other smaller >features. > >So far I created a book my parsing the gm2600.pgn file and saving all positions >which occur at least 5 times. > >This is certainly much better than no book at all but leaves much much room for >improvment I'm sure. > >What general advice do you book makers have for me? > >Thanks, >Eric First, may I suggest that you have two opening books, one for white's moves and one for black's moves. This way you can "feed" pgns into white's book that have white winning (and drawing). Likewise for black's book, you can "feed" pgns into black's book that have black winning (and drawing). Second, I would also use more recent pgns than in gm2600.pgn because current over-the-board players know what the latest changes are in openings, and they have the benefit of computer analysis. (Btw, I have made a pgn collection of recent games that is available at crafty-chess.com in the user download section.) Also limiting the book to games with both players elo 2600+ will mean a small book, unless you allow the number of position occurrences to be very small (see next paragraph). Third, no matter how hard you try, bad opening moves are going to be in the opening book. The question is how to limit the number of them. I believe the best and only reliable approach is to have a very high number for the number of occurrences before including that position in the book. I recommend that you use 12 occurrences if you are starting from a pgn collection of 60K games. Another approach to quality control is "book learning". I'm not a fan of book learning. All I think it does is adjust the statistics for each position (# occurrences, win-lose-draw) based on the engine's performance. But if your engine is playing an engine 100 elo stronger, why punish the opening because your engine lost. The opening might have been excellent. Likewise, why reward a poor opening because your engine defeated a weaker opponent. Another point. Some pgn collections have loads of old games, low elo games, duplicate games, twin games, blitz, rapid, lightning, email, Internet, simultaneous exhibition games and grandmaster short draws. My collection that I mentioned before is one of those that has filtered those types of games out. So be careful. Good luck, Norm
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