Author: José de Jesús García Ruvalcaba
Date: 09:57:18 01/12/99
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On January 11, 1999 at 20:58:11, Graham Laight wrote: >On January 11, 1999 at 13:57:31, José de Jesús García Ruvalcaba wrote: > >>On January 09, 1999 at 05:55:25, Graham Laight wrote: >> >>>As I was sitting eating my breakfast just now, it occured to me that there are >>>basically 3 items that, between them, will influence how close an evaluation of >>>a chess position is to how good that position really is: >>> >>>1. The number of pieces of knowledge the evaluation function can call upon >>> >>>2. The quality of those pieces of knowledge >>> >>>3. The accuracy of selecting the right pieces of knowledge (and their >>>appropriate weightings) for the position at hand >>> >>> >>>Does anybody have any thoughts about this? >> >>I think that different evaluation functions are not comparable by themselves. > >Why not? > >You take a chess position, and run 2 different evaluation functions against it. > >The one that more accurately scores the position is the better evaluation >function. > Now the problem is, how to measure this accuracy? There are only three posible theoretical values for a chess position (white wins, draw or black wins), and it is unknown for most positions. An evaluation function would be theoretically accurate if it gives every white win a better score than any draw and every draw a better score than a black win, but I can not imagine a way to find out other than solving the game of chess. Also, for a moment let us assume that the contempt factor is zero. If you take an evaluation function and multiply it for *any* positive number, you get different evaluation function which will *always* lead to the same best move! Which one is more accurate? >>Overall program strength is. I mean, you can compare two evaluation functions >>once you have all the other components of the programs fixed; but with a >>different set of other components you can get different results. >>Among the "other components" I can see: >>1. Hardware: processor speed, and amount of memory used for hash tables. >>2. The search algorithm, including extensions. >>3. The opening book. >>4. Endgame tablebases. >>5. The time control. > >This is like saying, "You cannot evaluate the engine in a car unless you take >into consideration the door handles and the headlights". > >I wanted to discuss the evaluation function of a program on its own - not the >other stuff - important though I agree it is. > Your original statement is essentially correct. I did not mean to disagree (in fact I agree). My point is that I can not see a way to measure the quality of an evaluation function by itself; but it is clear for me how to measure overall program strength. José. >Ah well - I have to admit that sometimes it's the door handles that sell the >car. > >Graham. > >> I think that the correct "accuracy" of the weightings can dramatically change >>with these factors.
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