Author: James Swafford
Date: 10:54:55 01/16/02
Go up one level in this thread
On January 16, 2002 at 13:13:17, Ricardo Gibert wrote: >On January 16, 2002 at 12:56:06, James Swafford wrote: > >>On January 16, 2002 at 07:41:28, Graham Laight wrote: >> >>I don't have time right now to read all the previous posts, but >>I'd like to point out something I thought interesting when >>playing with TDLeaf... >> >>Temporal difference algorithms needs exactly what you mention - >>a probability (or a certainty factor I guess) of winning, and >>it needs to be in the interval -1 .. 1. Of course -1 = loss, >>0 = draw, 1 = win. .9 is 'almost certainly a win', etc. >> >>You can scale the raw scores from your evaluator and plug >>that into a hyperbolic tangent function, and the result of that >>will be in that closed interval. What I think is so neat about >>using a hyerbolic tangent is that it predicts +5 pawns to >>be almost as sure to win as +9 pawns or +15 pawns. If I get >>a chance later and you're interested I can throw up a little >>chart... it's interesting when you think about it. Say a >>1 pawn advantage yields a certainty factor of .74 (I'm making that >>up). A 2 pawn advantage might yield a cf of .89, then 3 .95, etc. >>The 'obviousness' starts to set it. >> >>Ok, enough rambling... I've got to get going. > >What you propose is a tranformation that will not cause an engine to select a >different move that it would have without the tranformation being applied. It >burns up cpu time with no benefit. Fine for TD, but no help in a regular >program. I completely agree... just pointing out something I thought was pretty neat. It'd be insane to compute that for every eval, but it's interesting to look at the value of the pv move at the end of the search. > >> >>-- >>James >> >> >>>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
This page took 0 seconds to execute
Last modified: Thu, 15 Apr 21 08:11:13 -0700
Current Computer Chess Club Forums at Talkchess. This site by Sean Mintz.