From: Steinar H. Gunderson <sesse@debian.org>
Date: Wed, 26 Dec 2007 18:05:51 +0000 (+0100)
Subject: Adjusted initial parameters for maximum prediction power; in particular,
X-Git-Url: https://git.sesse.net/?a=commitdiff_plain;h=HEAD;p=foosball

Adjusted initial parameters for maximum prediction power; in particular,
fixed a long-standing off-by-86400 bug.
---

diff --git a/foosball.pm b/foosball.pm
index b5750b2..3872242 100644
--- a/foosball.pm
+++ b/foosball.pm
@@ -6,7 +6,8 @@ use POSIX;
 package foosball;
 
 our $initial_rating = 1500.0;
-our $initial_rd = 350.0;
+our $initial_rd = 400.0;
+our $c = 22.5;
 
 sub db_connect {
 	my $dbh = DBI->connect("dbi:Pg:dbname=foosball;host=127.0.0.1", "foosball", "cleanrun", {AutoCommit => 0});
@@ -64,12 +65,10 @@ sub create_user_if_not_exists {
 	return $dbh;
 }
 
-# c=8 => RD=50 moves to RD=350 over approx. five years
-our $c = 8;
-
+# $age is in days
 sub apply_aging {
 	my ($rd, $age) = @_;
-	$rd = sqrt($rd*$rd + $c * $c * ($age / 86400.0));
+	$rd = sqrt($rd*$rd + $c * $c * $age);
 	$rd = $initial_rd if ($rd > $initial_rd);
 	return $rd;
 }