Author: Don Dailey
Date: 07:06:53 08/16/98
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On August 15, 1998 at 22:18:24, Jeff Anderson wrote: >Can someone perhaps give me a rundown of the piece values used by different >chess programs? How do small changes piece values in programs affect their >play? >Thanks, >Jeff Here are some values Larry Kaufman recommended that he felt would make most decisions reasonably correct. It is based on 1/3 pawn units, which he felt was the lowest unit that can return good values. He also considered finer resolution like 1/4 units but thinks the 1/3 unit is the best if you want the unit size to be relatively grainy: pawn 3 knight 3 bishop 10 rook 15 queen 29 Bish Pair 1 As someone else posted, the bishops are slightly more valuable than the knights, and this should be reflected in the various positional bonuses each piece gets. Larry however once believed that there is no intrinsic difference in value between the two, as long as your program has a bishop pair bonus. His latest thinking since then is that the bishop probably is just slightly more valuable after all, even when you have no bishop pair. All of this assumes some big global average though, a good evaluation will try to take into account more specific information about whether a knight or bishop is better in some given situation. Larry also had another table for several "piece cooperation" terms. I can't remember them all or what the values are but a couple are: a rook pair penalty a knight pair penalty I think he had these also, I'm not sure: a penalty for each rook if there is a queen. a penalty for each bishop if there is a queen. a bonus for each kight if there is a queen. a penalty for rooks based on how many pawns there are. These are all static terms and are pretty small, designed mainly to sway the program one way or the other when an exchange can go either way. A good thing to do might be to see how these various terms act when there are NO other positional considerations. Will it tend to make the common sense decisions in various trade down situations? - Don
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