2 Stockfish, a UCI chess playing engine derived from Glaurung 2.1
3 Copyright (C) 2004-2023 The Stockfish developers (see AUTHORS file)
5 Stockfish is free software: you can redistribute it and/or modify
6 it under the terms of the GNU General Public License as published by
7 the Free Software Foundation, either version 3 of the License, or
8 (at your option) any later version.
10 Stockfish is distributed in the hope that it will be useful,
11 but WITHOUT ANY WARRANTY; without even the implied warranty of
12 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
13 GNU General Public License for more details.
15 You should have received a copy of the GNU General Public License
16 along with this program. If not, see <http://www.gnu.org/licenses/>.
25 #include "benchmark.h"
34 #include "syzygy/tbprobe.h"
35 #include "nnue/evaluate_nnue.h"
43 // FEN string for the initial position in standard chess
44 const char* StartFEN = "rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR w KQkq - 0 1";
47 // position() is called when the engine receives the "position" UCI command.
48 // It sets up the position that is described in the given FEN string ("fen") or
49 // the initial position ("startpos") and then makes the moves given in the following
50 // move list ("moves").
52 void position(Position& pos, istringstream& is, StateListPtr& states) {
59 if (token == "startpos")
62 is >> token; // Consume the "moves" token, if any
64 else if (token == "fen")
65 while (is >> token && token != "moves")
70 states = StateListPtr(new std::deque<StateInfo>(1)); // Drop the old state and create a new one
71 pos.set(fen, Options["UCI_Chess960"], &states->back(), Threads.main());
73 // Parse the move list, if any
74 while (is >> token && (m = UCI::to_move(pos, token)) != MOVE_NONE)
76 states->emplace_back();
77 pos.do_move(m, states->back());
81 // trace_eval() prints the evaluation of the current position, consistent with
82 // the UCI options set so far.
84 void trace_eval(Position& pos) {
86 StateListPtr states(new std::deque<StateInfo>(1));
88 p.set(pos.fen(), Options["UCI_Chess960"], &states->back(), Threads.main());
92 sync_cout << "\n" << Eval::trace(p) << sync_endl;
96 // setoption() is called when the engine receives the "setoption" UCI command.
97 // The function updates the UCI option ("name") to the given value ("value").
99 void setoption(istringstream& is) {
101 Threads.main()->wait_for_search_finished();
103 string token, name, value;
105 is >> token; // Consume the "name" token
107 // Read the option name (can contain spaces)
108 while (is >> token && token != "value")
109 name += (name.empty() ? "" : " ") + token;
111 // Read the option value (can contain spaces)
113 value += (value.empty() ? "" : " ") + token;
115 if (Options.count(name))
116 Options[name] = value;
118 sync_cout << "No such option: " << name << sync_endl;
122 // go() is called when the engine receives the "go" UCI command. The function
123 // sets the thinking time and other parameters from the input string, then starts
126 void go(Position& pos, istringstream& is, StateListPtr& states) {
128 Search::LimitsType limits;
130 bool ponderMode = false;
132 limits.startTime = now(); // The search starts as early as possible
135 if (token == "searchmoves") // Needs to be the last command on the line
137 limits.searchmoves.push_back(UCI::to_move(pos, token));
139 else if (token == "wtime") is >> limits.time[WHITE];
140 else if (token == "btime") is >> limits.time[BLACK];
141 else if (token == "winc") is >> limits.inc[WHITE];
142 else if (token == "binc") is >> limits.inc[BLACK];
143 else if (token == "movestogo") is >> limits.movestogo;
144 else if (token == "depth") is >> limits.depth;
145 else if (token == "nodes") is >> limits.nodes;
146 else if (token == "movetime") is >> limits.movetime;
147 else if (token == "mate") is >> limits.mate;
148 else if (token == "perft") is >> limits.perft;
149 else if (token == "infinite") limits.infinite = 1;
150 else if (token == "ponder") ponderMode = true;
152 Threads.start_thinking(pos, states, limits, ponderMode);
156 // bench() is called when the engine receives the "bench" command.
157 // Firstly, a list of UCI commands is set up according to the bench
158 // parameters, then it is run one by one, printing a summary at the end.
160 void bench(Position& pos, istream& args, StateListPtr& states) {
163 uint64_t num, nodes = 0, cnt = 1;
165 vector<string> list = setup_bench(pos, args);
166 num = count_if(list.begin(), list.end(), [](const string& s) { return s.find("go ") == 0 || s.find("eval") == 0; });
168 TimePoint elapsed = now();
170 for (const auto& cmd : list)
172 istringstream is(cmd);
173 is >> skipws >> token;
175 if (token == "go" || token == "eval")
177 cerr << "\nPosition: " << cnt++ << '/' << num << " (" << pos.fen() << ")" << endl;
181 Threads.main()->wait_for_search_finished();
182 nodes += Threads.nodes_searched();
187 else if (token == "setoption") setoption(is);
188 else if (token == "position") position(pos, is, states);
189 else if (token == "ucinewgame") { Search::clear(); elapsed = now(); } // Search::clear() may take a while
192 elapsed = now() - elapsed + 1; // Ensure positivity to avoid a 'divide by zero'
196 cerr << "\n==========================="
197 << "\nTotal time (ms) : " << elapsed
198 << "\nNodes searched : " << nodes
199 << "\nNodes/second : " << 1000 * nodes / elapsed << endl;
202 // The win rate model returns the probability of winning (in per mille units) given an
203 // eval and a game ply. It fits the LTC fishtest statistics rather accurately.
204 int win_rate_model(Value v, int ply) {
206 // The model only captures up to 240 plies, so limit the input and then rescale
207 double m = std::min(240, ply) / 64.0;
209 // The coefficients of a third-order polynomial fit is based on the fishtest data
210 // for two parameters that need to transform eval to the argument of a logistic
212 constexpr double as[] = { 0.38036525, -2.82015070, 23.17882135, 307.36768407};
213 constexpr double bs[] = { -2.29434733, 13.27689788, -14.26828904, 63.45318330 };
215 // Enforce that NormalizeToPawnValue corresponds to a 50% win rate at ply 64
216 static_assert(UCI::NormalizeToPawnValue == int(as[0] + as[1] + as[2] + as[3]));
218 double a = (((as[0] * m + as[1]) * m + as[2]) * m) + as[3];
219 double b = (((bs[0] * m + bs[1]) * m + bs[2]) * m) + bs[3];
221 // Transform the eval to centipawns with limited range
222 double x = std::clamp(double(v), -4000.0, 4000.0);
224 // Return the win rate in per mille units rounded to the nearest value
225 return int(0.5 + 1000 / (1 + std::exp((a - x) / b)));
231 /// UCI::loop() waits for a command from the stdin, parses it and then calls the appropriate
232 /// function. It also intercepts an end-of-file (EOF) indication from the stdin to ensure a
233 /// graceful exit if the GUI dies unexpectedly. When called with some command-line arguments,
234 /// like running 'bench', the function returns immediately after the command is executed.
235 /// In addition to the UCI ones, some additional debug commands are also supported.
237 void UCI::loop(int argc, char* argv[]) {
241 StateListPtr states(new std::deque<StateInfo>(1));
243 pos.set(StartFEN, false, &states->back(), Threads.main());
245 for (int i = 1; i < argc; ++i)
246 cmd += std::string(argv[i]) + " ";
249 if (argc == 1 && !getline(cin, cmd)) // Wait for an input or an end-of-file (EOF) indication
252 istringstream is(cmd);
254 token.clear(); // Avoid a stale if getline() returns nothing or a blank line
255 is >> skipws >> token;
261 // The GUI sends 'ponderhit' to tell that the user has played the expected move.
262 // So, 'ponderhit' is sent if pondering was done on the same move that the user
263 // has played. The search should continue, but should also switch from pondering
264 // to the normal search.
265 else if (token == "ponderhit")
266 Threads.main()->ponder = false; // Switch to the normal search
268 else if (token == "uci")
269 sync_cout << "id name " << engine_info(true)
271 << "\nuciok" << sync_endl;
273 else if (token == "setoption") setoption(is);
274 else if (token == "go") go(pos, is, states);
275 else if (token == "position") position(pos, is, states);
276 else if (token == "ucinewgame") Search::clear();
277 else if (token == "isready") sync_cout << "readyok" << sync_endl;
279 // Add custom non-UCI commands, mainly for debugging purposes.
280 // These commands must not be used during a search!
281 else if (token == "flip") pos.flip();
282 else if (token == "bench") bench(pos, is, states);
283 else if (token == "d") sync_cout << pos << sync_endl;
284 else if (token == "eval") trace_eval(pos);
285 else if (token == "compiler") sync_cout << compiler_info() << sync_endl;
286 else if (token == "export_net")
288 std::optional<std::string> filename;
290 if (is >> skipws >> f)
292 Eval::NNUE::save_eval(filename);
294 else if (token == "--help" || token == "help" || token == "--license" || token == "license")
295 sync_cout << "\nStockfish is a powerful chess engine for playing and analyzing."
296 "\nIt is released as free software licensed under the GNU GPLv3 License."
297 "\nStockfish is normally used with a graphical user interface (GUI) and implements"
298 "\nthe Universal Chess Interface (UCI) protocol to communicate with a GUI, an API, etc."
299 "\nFor any further information, visit https://github.com/official-stockfish/Stockfish#readme"
300 "\nor read the corresponding README.md and Copying.txt files distributed along with this program.\n" << sync_endl;
301 else if (!token.empty() && token[0] != '#')
302 sync_cout << "Unknown command: '" << cmd << "'. Type help for more information." << sync_endl;
304 } while (token != "quit" && argc == 1); // The command-line arguments are one-shot
308 /// Turns a Value to an integer centipawn number,
309 /// without treatment of mate and similar special scores.
310 int UCI::to_cp(Value v) {
312 return 100 * v / UCI::NormalizeToPawnValue;
315 /// UCI::value() converts a Value to a string by adhering to the UCI protocol specification:
317 /// cp <x> The score from the engine's point of view in centipawns.
318 /// mate <y> Mate in 'y' moves (not plies). If the engine is getting mated,
319 /// uses negative values for 'y'.
321 string UCI::value(Value v) {
323 assert(-VALUE_INFINITE < v && v < VALUE_INFINITE);
327 if (abs(v) < VALUE_TB_WIN_IN_MAX_PLY)
328 ss << "cp " << UCI::to_cp(v);
329 else if (abs(v) < VALUE_MATE_IN_MAX_PLY)
331 const int ply = VALUE_MATE_IN_MAX_PLY - 1 - std::abs(v); // recompute ss->ply
332 ss << "cp " << (v > 0 ? 20000 - ply : -20000 + ply);
335 ss << "mate " << (v > 0 ? VALUE_MATE - v + 1 : -VALUE_MATE - v) / 2;
341 /// UCI::wdl() reports the win-draw-loss (WDL) statistics given an evaluation
342 /// and a game ply based on the data gathered for fishtest LTC games.
344 string UCI::wdl(Value v, int ply) {
348 int wdl_w = win_rate_model( v, ply);
349 int wdl_l = win_rate_model(-v, ply);
350 int wdl_d = 1000 - wdl_w - wdl_l;
351 ss << " wdl " << wdl_w << " " << wdl_d << " " << wdl_l;
357 /// UCI::square() converts a Square to a string in algebraic notation (g1, a7, etc.)
359 std::string UCI::square(Square s) {
360 return std::string{ char('a' + file_of(s)), char('1' + rank_of(s)) };
364 /// UCI::move() converts a Move to a string in coordinate notation (g1f3, a7a8q).
365 /// The only special case is castling where the e1g1 notation is printed in
366 /// standard chess mode and in e1h1 notation it is printed in Chess960 mode.
367 /// Internally, all castling moves are always encoded as 'king captures rook'.
369 string UCI::move(Move m, bool chess960) {
377 Square from = from_sq(m);
378 Square to = to_sq(m);
380 if (type_of(m) == CASTLING && !chess960)
381 to = make_square(to > from ? FILE_G : FILE_C, rank_of(from));
383 string move = UCI::square(from) + UCI::square(to);
385 if (type_of(m) == PROMOTION)
386 move += " pnbrqk"[promotion_type(m)];
392 /// UCI::to_move() converts a string representing a move in coordinate notation
393 /// (g1f3, a7a8q) to the corresponding legal Move, if any.
395 Move UCI::to_move(const Position& pos, string& str) {
397 if (str.length() == 5)
398 str[4] = char(tolower(str[4])); // The promotion piece character must be lowercased
400 for (const auto& m : MoveList<LEGAL>(pos))
401 if (str == UCI::move(m, pos.is_chess960()))
407 } // namespace Stockfish