Author: Amir Ban
Date: 04:49:14 07/31/98
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On July 31, 1998 at 04:01:08, blass uri wrote: > >On July 31, 1998 at 02:24:20, Jouni Uski wrote: > >>On July 31, 1998 at 01:51:57, blass uri wrote: >> >>>The programs I know give me evaluation in pawns and I prefer to see >>>in the evaluation function the predicted result of the game(number between 0 >>>and 1) and not an evaluation in pawns. >>> >>>Uri >> >>What are You meaning? Predicted result evaluation has only 3 values: 0, 0.5 and >>1! Not very informative... > >I mean the average resultI expect to have >for example it can be 0.7 if I believe the probability to win is 50% >and the probability of a draw is 40% > >Uri >> >>Jouni You can see from a few responses you got, that the interpretation of the eval in terms of expected result is not obvious to many. What are you asking for is not so simple. Suppose I printed out the score as a value between -1 and 1 that represents the expected outcome. You would scan a database of games and find that there are say 9000 positions that I evaluate as 0.20, but you would find that the average outcome of those positions is actually 0.35. You would complain that I'm giving you wrong information, and you would be right in a sense. Even if my score would be right for any game database that you can find, it's not obvious to me that it would still be correct in say a Fritz vs. Junior match, for many reasons. One is that computers tend to have different positions than humans, another that Junior has a better understanding of the games it plays itself, and the fact that one program is stronger than the other would also skew the "correct" score in some direction. Currently program scores don't have much objective meaning, so there is no problem, and you can't argue that they are wrong except by showing that the program loses a lot, which is a weak argument, because many programs have wrong evaluations and win. A few months ago I suggested here (or maybe in rgcc I don't remember) to use the score interpretation as expected outcome as a way of tuning the evaluation function. The idea was simply that what the program evaluates should match the actual percentages that occurred in many games. This method of tuning looked to me very attractive because it uses evaluation only and doesn't depend on search. I'm using this method as a rough test if a change I'm doing is in the right direction. It had some nice successes, and also a few failures. I don't trust it on its own. A change in formulation may perhaps make it more successful. Amir
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