Author: Robert Hyatt
Date: 13:01:52 01/16/02
Go up one level in this thread
On January 16, 2002 at 15:01:38, Ricardo Gibert wrote: >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? First, I am not sure I believe the pawn advantage wins 3 of every 4 games. That seems high. I would expect a 2-pawn advantage to be closer to that kind of winning percentage. But if we plot this on some special graph, I could certainly envision a straight line result that connects material/positional score advantage to some reasonable winning percentage estimate. But it would be a pointless exercise, because if that can be done, then it would say that one could be derived from the other, and therefore the original score is "good enough"...
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