Author: Gordon Rattray
Date: 05:48:56 01/16/02
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On January 16, 2002 at 08:09:58, Graham Laight wrote: >On January 16, 2002 at 07:49:25, Albert Silver 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 >> >>Not so strange considering that chess is a game of absolutes, whether we know >>them or not. A positions is either a win (with best play), a draw, or a loss. >>How are you going to estimate how many times a player _should_ win? --> >> >>Hmmm... Normally, I'd say John is going to win this, but having seen him drink 5 >>beers during lunch shortly before the game, I'd say he only has a 60% chance.... >>:-) >> >> Albert > >I don't say that the evaluations would be more "accurate" - but I do say that >the number produced, accurate or not, would be on a more sensible scale. More sensible in what sense? Chess players are used to assessing positions in terms of pawns. Queen is about 9, rook is about 5, etc. Positional aspects can be compared against these material values. e.g. consider a sacrifice. How do the resulting positional factors (e.g. open lines, exposed king position) compare to the material loss? Annotators often use phrases like "White has compensation for the pawn". I've seen general chess priciples like "a pawn is worth two tempi" (or is it three?! ;-)). It seems like a good unit to compare against. Alternatively, if I said "White has a 70% chance to win". Is this equilavent to being a knight up? A rook? Players would have to learn what each percentage meant in terms of their current understanding. So why not stick with the current evaluation method? Gordon
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