// 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.
- double as[] = {-1.17202460e-01, 5.94729104e-01, 1.12065546e+01, 1.22606222e+02};
- double bs[] = {-1.79066759, 11.30759193, -17.43677612, 36.47147479};
+ constexpr double as[] = { -0.58270499, 2.68512549, 15.24638015, 344.49745382};
+ constexpr double bs[] = { -2.65734562, 15.96509799, -20.69040836, 73.61029937 };
+
+ // Enforce that NormalizeToPawnValue corresponds to a 50% win rate at ply 64
+ static_assert(UCI::NormalizeToPawnValue == int(as[0] + as[1] + as[2] + as[3]));
+
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 the eval to centipawns with limited range
- double x = std::clamp(double(100 * v) / PawnValueEg, -2000.0, 2000.0);
+ double x = std::clamp(double(v), -4000.0, 4000.0);
// Return the win rate in per mille units rounded to the nearest value
return int(0.5 + 1000 / (1 + std::exp((a - x) / b)));
/// UCI::loop() waits for a command from the stdin, parses it and then calls the appropriate
/// function. It also intercepts an end-of-file (EOF) indication from the stdin to ensure a
-/// graceful exit if the GUI dies unexpectedly. When called with some command-line arguments,
+/// graceful exit if the GUI dies unexpectedly. When called with some command-line arguments,
/// like running 'bench', the function returns immediately after the command is executed.
/// In addition to the UCI ones, some additional debug commands are also supported.
cmd += std::string(argv[i]) + " ";
do {
- if (argc == 1 && !getline(cin, cmd)) // Wait for an input or an end-of-file (EOF) indication
+ if (argc == 1 && !getline(cin, cmd)) // Wait for an input or an end-of-file (EOF) indication
cmd = "quit";
istringstream is(cmd);
stringstream ss;
if (abs(v) < VALUE_MATE_IN_MAX_PLY)
- ss << "cp " << v * 100 / PawnValueEg;
+ ss << "cp " << v * 100 / NormalizeToPawnValue;
else
ss << "mate " << (v > 0 ? VALUE_MATE - v + 1 : -VALUE_MATE - v) / 2;