// 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)));