Author: Ricardo Gibert
Date: 12:01:38 01/16/02
Go up one level in this thread
On January 16, 2002 at 14:06:37, Robert Hyatt wrote: >On January 16, 2002 at 12:58:13, James Swafford wrote: > >>On January 16, 2002 at 11:43:59, Robert Hyatt wrote: >> >>>On January 16, 2002 at 07:41:28, Graham Laight wrote: >>> >>>>It has occurred to me that it is wrong to evaluate a position in terms of >>>>relative pawns (the "de facto" standard - whereby an evaluation of 2 means that >>>>you're approximately the equivalent of 2 pawns ahead). >>>> >>>>This means that many aspects of evaluation have to be squeezed into a dimension >>>>which is not appropriate at all. >>>> >>>>A better way would be to evaluate "winning probability". If a position was a >>>>draw, the value would be 0.50 (or 50%). If the player should win 3 out of 4 >>>>times, the eval should be 75%. If the player must win from here, then the >>>>evaluation should be 100%. >>>> >>>>It seems strange when you think about it that all programmers have chosen to >>>>adopt the traditional "pawn equivalence" standard. >>>> >>>>-g >>> >>> >>>It is harder to do otherwise. IE KPP vs K is winning, except for some rare >>>cases, while KR vs KB is drawn. >>> >>>It would be very hard to translate some sort of material imbalance into a >>>winning percentage. As a general rule, the more material you are ahead, the >>>better your chances, with some exceptions that many engines know about... >> >>Right, but the gains are not linear, and raw scores from an evaluator >>typically are. Winning probability is not a linear function of material >>+ positional advantages. >> >>-- >>James > > >It could be linear. But perhaps the slope of the straight line is not 45 >degrees... Hmmm...an even position has about a 50% WE (=Win Expectation). It has been estimated statistically that a pawn advantage has about a 75% WE on average. Now how will you fit all the larger positive advantages in the remaining 75% to 100% and maintain a staight line?
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