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Subject: Calculating Computer Ratings????

Author: Shaun Graham

Date: 21:48:21 07/29/98


  How are computer chess program ratings calculated, what is the formula?
It has occurred to me that perhaps it makes no sense to calculate computer
ratings in the way that human ratings are calculated.  It's hard to describe my
point so i will give an example.

A human rated 2200(base rating) plays a tournament of ten games, after the
tournament his rating is calculated to be 2280.  Arriving at this calculation
his initial rating of 2200 was used.  In his next tournament of ten games his
rating is calculated to be 2320.  To arrive at this rating 2280 was used in the
base calculation.  This seems to work for humans because you can hypothesize
improvement thus a new base rating works, but for computers it seems as if
having a new base rating may be problematic because their is no so called
"improvement".  In a way it seems to me that it all works fine and I know the
rating is supposed to just measure performance but i just have an intuitive feel
that there should be a difference in the calculations.

Another problem that i have is that say i have 50 tourney games played, and i
calculate the rating in ten game increments.  I use the new rating achieved
after each ten as the base to do my calculation.  my final rating is different
than if i acted as if all the games happened in one tournament.  Perhaps i'm
screwing the calculation?


I have hypothesized that to calculate the rating of a program based upon all the
games played at once you should use the provisional formula

For example Chessmaster 5555 on Kai Luebke's web page
"http://www.geocities.com/TimesSquare/Ring/8448/chessindex2.html" in 40/2 games
has won 29 games, drawn 13, lost 11 games.  I gave a flat rating of 2400 to all
opponents

the calculation went as follows [(29wins * 2400)+(29wins*400)] + [(13draws * 0)+
(13draws * 2400)] + [(11Loss * 2400)-(11Loss * 400)] = 2535(Chessmaster is a
MONSTER)

This is the standard uscf formula of adding 400 points to opponents ratings for
wins, and subtracting 400 for losses, then dividing by the number of games
played for a provisional rating.

The opponents were Rebel9 & 8, Mchess 7, Fritz 5, Hiarcs 4 & 6, crafty 14.8,
Junior 4.6, and Genius 5.



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