Author: Robert Hyatt
Date: 13:49:36 03/22/98
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On March 22, 1998 at 16:01:00, Komputer Korner wrote: >What you are also forgetting is How is your big varied book made? If you >make it by dumping in PGN games and cutting it off at say 60 ply, then >you are also including a lot of bad lines. How do you weed these bad >lines out? Crafty has had this problem for the last couple of years, and >only now is finally resolving it because of it's learning feature. there are several answers, and I use 'em all. First, you can cull moves that were only played once or twice, as those are nothing but moves from a single game and are not worth considering without a search to verify them. I use the "minplay" option set to 3 when I build a book for Crafty, meaning that in the 330,000 game file I use, if a move was not played at least 3 times, it is tossed out. I also pay attention to several things about a book move, and give the user a chance to indicate the "weight" each factor should influence the move choice decision... the weights are (1) frequency, which is nothing but a count of how many times each book move was played; (2) win/lose ratio, (3) static evaluation (which would tend to avoid some book lines like Bxf3 gxf3 where gxf3 was played as a speculative attacking move but which shreds the kingside) (4) learned results. You can also add a normal search on top of these if you want. But the bottom line is, even if you take games between GM players, the games are filled with tactical mistakes. And I mean *filled*. I have yet to run thru a game that didn't have at least one, and often more, such mistakes, which means you can't even play GM moves "safely." >Testing a book at blitz is not the same as testing at longer time >controls. So the bottom line is that making a huge book is no panacea >because your program will lose a lot of games from all the bad lines in >the book. making and adjusting a good opening book is somewhat the same >for a human. While I'd partially agree, blitz games *do* eliminate a ton of bad openings. Standard time controls will eliminate more, but I'd bet that blitz will take care of 95% of the truly bad openings and at that speed, it doesn't take years...
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