+
+ // The win rate model returns the probability of winning (in per mille units) given an
+ // eval and a game ply. It fits the LTC fishtest statistics rather accurately.
+ int win_rate_model(Value v, int ply) {
+
+ // The model only captures up to 240 plies, so limit the input and then rescale
+ double m = std::min(240, ply) / 64.0;
+
+ // 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.
+ 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(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)));
+ }
+
+} // namespace
+
+
+/// 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,
+/// 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.
+
+void UCI::loop(int argc, char* argv[]) {
+
+ Position pos;
+ string token, cmd;
+ StateListPtr states(new std::deque<StateInfo>(1));
+
+ pos.set(StartFEN, false, &states->back(), Threads.main());
+
+ for (int i = 1; i < argc; ++i)
+ cmd += std::string(argv[i]) + " ";
+
+ do {
+ if (argc == 1 && !getline(cin, cmd)) // Wait for an input or an end-of-file (EOF) indication
+ cmd = "quit";
+
+ istringstream is(cmd);
+
+ token.clear(); // Avoid a stale if getline() returns nothing or a blank line
+ is >> skipws >> token;
+
+ if ( token == "quit"
+ || token == "stop")
+ Threads.stop = true;
+
+ // The GUI sends 'ponderhit' to tell that the user has played the expected move.
+ // So, 'ponderhit' is sent if pondering was done on the same move that the user
+ // has played. The search should continue, but should also switch from pondering
+ // to the normal search.
+ else if (token == "ponderhit")
+ Threads.main()->ponder = false; // Switch to the normal search
+
+ else if (token == "uci")
+ sync_cout << "id name " << engine_info(true)
+ << "\n" << Options
+ << "\nuciok" << sync_endl;
+
+ else if (token == "setoption") setoption(is);
+ else if (token == "go") go(pos, is, states);
+ else if (token == "position") position(pos, is, states);
+ else if (token == "ucinewgame") Search::clear();
+ else if (token == "isready") sync_cout << "readyok" << sync_endl;
+
+ // Add custom non-UCI commands, mainly for debugging purposes.
+ // These commands must not be used during a search!
+ else if (token == "flip") pos.flip();
+ else if (token == "bench") bench(pos, is, states);
+ else if (token == "d") sync_cout << pos << sync_endl;
+ else if (token == "eval") trace_eval(pos);
+ else if (token == "compiler") sync_cout << compiler_info() << sync_endl;
+ else if (token == "export_net")
+ {
+ std::optional<std::string> filename;
+ std::string f;
+ if (is >> skipws >> f)
+ filename = f;
+ Eval::NNUE::save_eval(filename);
+ }
+ else if (token == "--help" || token == "help" || token == "--license" || token == "license")
+ sync_cout << "\nStockfish is a powerful chess engine for playing and analyzing."
+ "\nIt is released as free software licensed under the GNU GPLv3 License."
+ "\nStockfish is normally used with a graphical user interface (GUI) and implements"
+ "\nthe Universal Chess Interface (UCI) protocol to communicate with a GUI, an API, etc."
+ "\nFor any further information, visit https://github.com/official-stockfish/Stockfish#readme"
+ "\nor read the corresponding README.md and Copying.txt files distributed along with this program.\n" << sync_endl;
+ else if (!token.empty() && token[0] != '#')
+ sync_cout << "Unknown command: '" << cmd << "'. Type help for more information." << sync_endl;
+
+ } while (token != "quit" && argc == 1); // The command-line arguments are one-shot