From aed28496bc425870315032b89dd1e20e87fb5b17 Mon Sep 17 00:00:00 2001
From: Kalle <38327916+Sendouc@users.noreply.github.com>
Date: Sat, 26 Mar 2022 10:31:49 +0200
Subject: [PATCH] Add tau

---
 app/core/mmr/utils.ts | 7 ++++++-
 openskill.d.ts        | 5 ++++-
 2 files changed, 10 insertions(+), 2 deletions(-)

diff --git a/app/core/mmr/utils.ts b/app/core/mmr/utils.ts
index 6b0d4ec17..ab441b70e 100644
--- a/app/core/mmr/utils.ts
+++ b/app/core/mmr/utils.ts
@@ -3,6 +3,8 @@ import { rating, ordinal, rate } from "openskill";
 import { LFG_GROUP_FULL_SIZE, MMR_TOPX_VISIBILITY_CUTOFF } from "~/constants";
 import { PlayFrontPageLoader } from "~/routes/play/index";
 
+const TAU = 0.3;
+
 /** Get first skill object of the array (should be ordered so that most recent skill is first) and convert it into MMR. */
 export function skillArrayToMMR(
   skills: {
@@ -91,7 +93,10 @@ export function adjustSkills({
   const winningTeam = playerIds.winning.map(mapToRatings);
   const losingTeam = playerIds.losing.map(mapToRatings);
 
-  const [ratedWinners, ratedLosers] = rate([winningTeam, losingTeam]);
+  const [ratedWinners, ratedLosers] = rate([winningTeam, losingTeam], {
+    tau: TAU,
+    preventSigmaIncrease: true,
+  });
   const ratedToReturnable =
     (side: "winning" | "losing") =>
     (rating: Rating, i: number): AdjustSkill => ({
diff --git a/openskill.d.ts b/openskill.d.ts
index 2276acd48..7d7be487c 100644
--- a/openskill.d.ts
+++ b/openskill.d.ts
@@ -6,5 +6,8 @@ type Rating = {
 declare module "openskill" {
   export function rating(rating?: Rating): Rating;
   export function ordinal(rating: Rating): number;
-  export function rate(ratings: [Rating[], Rating[]]): [Rating[], Rating[]];
+  export function rate(
+    ratings: [Rating[], Rating[]],
+    options: { tau: number; preventSigmaIncrease: boolean }
+  ): [Rating[], Rating[]];
 }