Update WDL model for NNUE

vondele · vondele · commit dc4983327df7 · 2021-06-28T21:13:30.000+02:00
This updates the WDL model based on the LTC statistics in June this year (10M games), so from pre-NNUE to NNUE based results. (for old results see, official-stockfish#2778) As before the fit by the model to the data is quite good. closes official-stockfish#3582 No functional change
diff --git a/src/uci.cpp b/src/uci.cpp
@@ -207,13 +207,13 @@ namespace {
      // Coefficients of a 3rd order polynomial fit based on fishtest data
      // for two parameters needed to transform eval to the argument of a
      // logistic function.
-     double as[] = {-8.24404295, 64.23892342, -95.73056462, 153.86478679};
-     double bs[] = {-3.37154371, 28.44489198, -56.67657741,  72.05858751};
+     double as[] = {-3.68389304,  30.07065921, -60.52878723, 149.53378557};
+     double bs[] = {-2.0181857,   15.85685038, -29.83452023,  47.59078827};
      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];
 
      // Transform eval to centipawns with limited range
-     double x = std::clamp(double(100 * v) / PawnValueEg, -1000.0, 1000.0);
+     double x = std::clamp(double(100 * v) / PawnValueEg, -2000.0, 2000.0);
 
      // Return win rate in per mille (rounded to nearest)
      return int(0.5 + 1000 / (1 + std::exp((a - x) / b)));
