From e04eb7d113a5eb10901f66b73ca81fb46e5285de Mon Sep 17 00:00:00 2001
From: Guangcong Luo <guangcongluo@gmail.com>
Date: Thu, 27 Feb 2014 19:28:11 -0600
Subject: [PATCH] Rating decay and other ladder tweaks

We now have a rating decay of -1/day at 1400, -2/day at 1450, -3/day
at 1500, etc. This roughly translates to a fall from the top of OU to
the bottom over a month of full inactivity, which is somewhat harsh
considering it's done regardless of inactivity. I might tweak this to
be less harsh later.

There's no rating decay below 1400. People can stay there as long as
they want.

The only other tweak is that K is now 40 at >1300 instead of >1400.
Very very slight tweak so that ratings in the 1300-1500 range are
very very slightly more precise.
---
 lib/ntbb-ladder.lib.php | 13 ++++++++++---
 1 file changed, 10 insertions(+), 3 deletions(-)

diff --git a/lib/ntbb-ladder.lib.php b/lib/ntbb-ladder.lib.php
index 87821f4ed..f27776c9c 100755
--- a/lib/ntbb-ladder.lib.php
+++ b/lib/ntbb-ladder.lib.php
@@ -255,6 +255,8 @@ class NTBBLadder {
 			return false;
 		}
 
+		$elo = $user['rating']['acre'];
+
 		$rating = new GlickoPlayer($user['rating']['r'], $user['rating']['rd']);
 		if ($user['rating']['rpdata']) {
 			$rpdata = explode('##',$user['rating']['rpdata']);
@@ -274,10 +276,16 @@ class NTBBLadder {
 					$rating->rating += $offset;
 					$offset = 0;
 				}
+
+				if ($elo >= 1400) {
+					$elo -= 1 + intval(($elo-1400)/50);
+				}
+
 				$user['rating']['rptime'] = $this->nextrp($user['rating']['rptime']);
 			}
 			$user['rating']['r'] = $rating->rating;
 			$user['rating']['rd'] = $rating->rd;
+			$user['rating']['lacre'] = $user['rating']['acre'] = $elo;
 		}
 
 		if ($newM) {
@@ -324,9 +332,8 @@ class NTBBLadder {
 			$user['rating']['rpdata'] .= '##'.$offset;
 		}
 
-
 		if ($newM) {
-			$elo = $user['rating']['oldacre'] = $user['rating']['acre'];
+			$user['rating']['oldacre'] = $elo;
 
 			$K = 50;
 			if ($elo < 1100) {
@@ -335,7 +342,7 @@ class NTBBLadder {
 				} else if ($newM['score'] > 0.5) {
 					$K = 80 - ($elo - 1000)*30/100;
 				}
-			} else if ($elo > 1400) {
+			} else if ($elo > 1300) {
 				$K = 40;
 			} else if ($elo > 1600) {
 				$K = 32;