Author: Dieter Buerssner
Date: 11:38:29 04/28/05
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On April 27, 2005 at 18:40:23, Eelco de Groot wrote: >I sure wish I could follow all your C code, but I never did Study C seriously. The code should be understandable, even for an "Excel is fine, I don't now much more"-user. The formulas I used are given in comments (and in the post of Odd Gunnar for the Schmitt formula). How I exactly implemented the Schmitt formula does not really matter. If you are curious, I used Horner's scheme, and some obfuscation may be the "return sign ? 0.5-p : 0.5+p", which is just a shorthand in C for saying if the Elo difference was negative, the result is 0.5-p; otherwise it is 0.5+p. p was exactly calculated with the formula given in Odd Gunnar's post (and technically avoided some multiplications and all those absolute value terms). >Are there any good compilers that are not expensive and work under Windows? There are many free choices available. One can be found at www.mingw.org. This particular choice has the advantage, that the download size is (almost) reasonable, even for a modem. Free command line compiler can be found at www.microsoft.com; also a beta version of their soon to be released new compiler. If you are really interested, I can find links. >I think I can guess where FIDE got its numbers, I suspect they are mainly >interpolations of the original table in Arpad E. Elo's 'The Rating of >Chessplayers, Past & Present' (Batsford Books, 1978). Prof. Elo gave the >following table: Wow! Did you really type this in? I checked a few data points - exactly equal to the data on fide.com (link is in a comment of the source code, I posted yesterday). But now, my mystery is: How did Elo calculate those numbers? (My program calculates very similar numbers, but they differ significantly in the last decimal place given). Of course, this all is not too interesting - all numbers are about right, and the amount they differ, will not really matter. Cheers, Dieter
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