Update the WDL model

robertnurnberg · Disservin · commit 4a869f41c611 · 2025-03-29T11:54:32.000+01:00
This PR updates the internal WDL model, using data from 2.6M games played by the revisions since f3bfce3. Note that the normalizing constant increases only moderately from 372 to 377. ``` > ./updateWDL.sh --firstrev f3bfce3 Running: ./updateWDL.sh --firstrev f3bfce3 --lasttrev HEAD --materialMin 17 --EloDiffMax 5 started at: Sat 22 Mar 11:02:14 CET 2025 Look recursively in directory pgns for games with max nElo difference 5 using books matching "UHO_Lichess_4852_v..epd" for SF revisions between f3bfce3 (from 2025-02-28 09:50:59 +0100) and HEAD (from 2025-03-21 11:22:59 +0100). Based on 138253430 positions from 2579360 games, NormalizeToPawnValue should change from 372 to 377. ended at: Sat 22 Mar 11:04:00 CET 2025 ``` ``` > cat scoreWDL.log Converting evals with NormalizeData = {'momType': 'material', 'momMin': 17, 'momMax': 78, 'momTarget': 58, 'as': [-37.45051876, 121.19101539, -132.78783573, 420.70576692]}. Reading eval stats from updateWDL.json. Retained (W,D,L) = (33794348, 69943262, 34515820) positions. Saved distribution plot to updateWDLdistro.png. Fit WDL model based on material. Initial objective function: 0.3648260131692729 Final objective function: 0.36482338611818094 Optimization terminated successfully. const int NormalizeToPawnValue = 377; Corresponding spread = 71; Corresponding normalized spread = 0.1879431202530567; Draw rate at 0.0 eval at material 58 = 0.9902694872976331; Parameters in internal value units: p_a = ((-13.500 * x / 58 + 40.928) * x / 58 + -36.828) * x / 58 + 386.830 p_b = ((96.534 * x / 58 + -165.791) * x / 58 + 90.897) * x / 58 + 49.296 constexpr double as[] = {-13.50030198, 40.92780883, -36.82753545, 386.83004070}; constexpr double bs[] = {96.53354896, -165.79058388, 90.89679019, 49.29561889}; Preparing plots. Saved graphics to updateWDL.png. Total elapsed time = 46.92s. ``` Only affects displayed `cp` and `wdl` values. closes #5939 No functional change
diff --git a/src/uci.cpp b/src/uci.cpp
@@ -513,8 +513,8 @@ WinRateParams win_rate_params(const Position& pos) {
     double m = std::clamp(material, 17, 78) / 58.0;
 
     // Return a = p_a(material) and b = p_b(material), see github.com/official-stockfish/WDL_model
-    constexpr double as[] = {-37.45051876, 121.19101539, -132.78783573, 420.70576692};
-    constexpr double bs[] = {90.26261072, -137.26549898, 71.10130540, 51.35259597};
+    constexpr double as[] = {-13.50030198, 40.92780883, -36.82753545, 386.83004070};
+    constexpr double bs[] = {96.53354896, -165.79058388, 90.89679019, 49.29561889};
 
     double a = (((as[0] * m + as[1]) * m + as[2]) * m) + as[3];
     double b = (((bs[0] * m + bs[1]) * m + bs[2]) * m) + bs[3];
