Chess::Elo - Perl module to calculate Chess ``Elo'' ratings
use Chess::Elo qw(:all);
# Alice is going to thump Bob... my ($alice_elo, $bob_elo) = (2100, 1200);
# Oh no, Alice lost to Bob! my $result = 0; # 0.5 for draw, 1 for win
my @new_elo_alice_bob = elo ($alice, 0, $bob); use Data::Dumper; warn Dumper(\@new_elo_alice_bob);
[ '2068.17894295388', # My, Alice took a hit on her rating :) '1231.82105704612' # Bob is setting pretty ];
This module provides a single function, elo
which allows one
to calculate individual ratings based on performance. Typically, a
player
is given an initial provisional rating of 1600 points.
In all cases, one gains and loses
points as a function of the playing strength of both parties and the result
of their encounter.
The formula used is the same one used at magi-nation:
http://www.magi-nation.com/Tournaments/ratingsfaq.htm
Or, quantitatively speaking:
A2 = A1 + 32 ( G - ( 1 / ( 1 + 10 ** ( ( B1 -A1) / 400 ) ) ) )
1, if A beats B
0, if A loses to B
0.5, if A draws to B
This function takes 3 arguments describing the result of a person with
rating $elo_a
competing with the person with rating $elo_b
.
The result argument is from the perspective of person A. Thus
if A won $result is 1. If A lost, $result is 0. If A drew, $result is 0.5.
None by default, elo
upon request.
One part of this discussion deserves repetition:
# 113 players have a rating of 2600 or above. # 16 players have a rating of 2700 or above. # 1 player (Garry Kasparov) has a rating of 2800 or above.
Terrence Brannon, tbone@cpan.org
Copyright 2003 by Terrence Brannon
This library is free software; you can redistribute it and/or modify it under the same terms as Perl itself.