From 5c2b3859579e20cb1abc8d53ae7ee229fbc1e335 Mon Sep 17 00:00:00 2001
From: "Robert Nurnberg @ elitebook" <robert.nurnberg@gmx.de>
Date: Sat, 24 Feb 2024 17:55:08 +0100
Subject: [PATCH] Update the WDL model

Based on 130M positions from 2.1M games.

```
Look recursively in directory pgns for games from SPRT tests using books
matching "UHO_4060_v..epd|UHO_Lichess_4852_v1.epd" for SF revisions
between 8e75548f2a10969c1c9211056999efbcebe63f9a (from 2024-02-17
17:11:46 +0100) and HEAD (from 2024-02-17 17:13:07 +0100). Based on
127920843 positions from 2109240 games, NormalizeToPawnValue should
change from 345 to 356.
```

The patch only affects the UCI-reported cp and wdl values.

closes https://github.com/official-stockfish/Stockfish/pull/5070

No functional change
---
 src/uci.cpp | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/src/uci.cpp b/src/uci.cpp
index 35f725b5e89..4d4ea689715 100644
--- a/src/uci.cpp
+++ b/src/uci.cpp
@@ -45,7 +45,7 @@
 namespace Stockfish {
 
 constexpr auto StartFEN             = "rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR w KQkq - 0 1";
-constexpr int  NormalizeToPawnValue = 345;
+constexpr int  NormalizeToPawnValue = 356;
 constexpr int  MaxHashMB            = Is64Bit ? 33554432 : 2048;
 
 UCI::UCI(int argc, char** argv) :
@@ -380,8 +380,8 @@ int win_rate_model(Value v, int ply) {
     // The coefficients of a third-order polynomial fit is based on the fishtest data
     // for two parameters that need to transform eval to the argument of a logistic
     // function.
-    constexpr double as[] = {-2.00568292, 10.45906746, 1.67438883, 334.45864705};
-    constexpr double bs[] = {-4.97134419, 36.15096345, -82.25513499, 117.35186805};
+    constexpr double as[] = {-1.06249702, 7.42016937, 0.89425629, 348.60356174};
+    constexpr double bs[] = {-5.33122190, 39.57831533, -90.84473771, 123.40620748};
 
     // Enforce that NormalizeToPawnValue corresponds to a 50% win rate at move 32.
     static_assert(NormalizeToPawnValue == int(0.5 + as[0] + as[1] + as[2] + as[3]));