Difference between revisions of "CoopetitionELO"
From #openttdcoop wiki
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Revision as of 13:50, 22 August 2006
To get a fair ranking we are using the ELO-Rating which is very popular, well-known and used in sports like Chess and Go.
The Calculation-Routine
function '''new_ELO_rating'''($team1_score, $team1_rating, $team2_rating)
{
$k_factor = 32;
$rating_expected = 1 /(1+10^(($team2_rating-$team1_rating)/400));
$new_rating = $team1_rating + ($k_factor * ($team1_score - $rating_expected));
return $new_rating;
}
$team1_score: 1 (win), 0,5 (draw), 0 (lost) $team1_rating: the old rating of team1 $team2_rating: the old rating of team2
How much points a team gain or loose depends on the expected rating: I.e. Garri Kasparow (Elo: 2806) looses against Zsuzsa Polgar (Elo: 2577), its expected that Garri Kasparow wins with 0,789 (=78,9%) In the next step he will loose more points, because it was more expacted he wins! How many points he will loose depends on the $k_factor, the $k_factor changes with the stats (games played, rating) of a player/team. The FIDE made some proposals for this $factor some time ago, which DON'T fit to our ladder, instead we will use our own $k_factor's
Here are our owns:
| Ratings | $k_factor |
|---|---|
| <1200 | 32 |
| >= 1200 | 24 |
| >= 1400 | 16 |
| >= 1600 | 8 |
