Update WDL model for current SF

This updates the WDL model based on the LTC statistics for the last month (8M games).

for old results see:
https://github.com/official-stockfish/Stockfish/pull/3582
https://github.com/official-stockfish/Stockfish/pull/2778

the model changed a bit from the past, some images to follow in the PR

closes https://github.com/official-stockfish/Stockfish/pull/3981

No functional change.

diff --git a/src/uci.cpp b/src/uci.cpp
index 741241b327110983e3a49623887c8c85deefe5d1..7b30cc043252e84b847317b3187598898a076a35 100644 (file)
--- a/src/uci.cpp
+++ b/src/uci.cpp
@@ -207,8 +207,8 @@ 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[] = {-3.68389304,  30.07065921, -60.52878723, 149.53378557};
-     double bs[] = {-2.0181857,   15.85685038, -29.83452023,  47.59078827};
+     double as[] = {-1.17202460e-01, 5.94729104e-01, 1.12065546e+01, 1.22606222e+02};
+     double bs[] = {-1.79066759,  11.30759193, -17.43677612,  36.47147479};
      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];