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"
42 // FEN string for the initial position in standard chess
43 const char* StartFEN = "rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR w KQkq - 0 1";
46 // position() is called when the engine receives the "position" UCI command.
47 // It sets up the position that is described in the given FEN string ("fen") or
48 // the initial position ("startpos") and then makes the moves given in the following
49 // move list ("moves").
51 void position(Position& pos, istringstream& is, StateListPtr& states) {
58 if (token == "startpos")
61 is >> token; // Consume the "moves" token, if any
63 else if (token == "fen")
64 while (is >> token && token != "moves")
69 states = StateListPtr(new std::deque<StateInfo>(1)); // Drop the old state and create a new one
70 pos.set(fen, Options["UCI_Chess960"], &states->back(), Threads.main());
72 // Parse the move list, if any
73 while (is >> token && (m = UCI::to_move(pos, token)) != MOVE_NONE)
75 states->emplace_back();
76 pos.do_move(m, states->back());
80 // trace_eval() prints the evaluation of the current position, consistent with
81 // the UCI options set so far.
83 void trace_eval(Position& pos) {
85 StateListPtr states(new std::deque<StateInfo>(1));
87 p.set(pos.fen(), Options["UCI_Chess960"], &states->back(), Threads.main());
91 sync_cout << "\n" << Eval::trace(p) << sync_endl;
95 // setoption() is called when the engine receives the "setoption" UCI command.
96 // The function updates the UCI option ("name") to the given value ("value").
98 void setoption(istringstream& is) {
100 string token, name, value;
102 is >> token; // Consume the "name" token
104 // Read the option name (can contain spaces)
105 while (is >> token && token != "value")
106 name += (name.empty() ? "" : " ") + token;
108 // Read the option value (can contain spaces)
110 value += (value.empty() ? "" : " ") + token;
112 if (Options.count(name))
113 Options[name] = value;
115 sync_cout << "No such option: " << name << sync_endl;
119 // go() is called when the engine receives the "go" UCI command. The function
120 // sets the thinking time and other parameters from the input string, then starts
123 void go(Position& pos, istringstream& is, StateListPtr& states) {
125 Search::LimitsType limits;
127 bool ponderMode = false;
129 limits.startTime = now(); // The search starts as early as possible
132 if (token == "searchmoves") // Needs to be the last command on the line
134 limits.searchmoves.push_back(UCI::to_move(pos, token));
136 else if (token == "wtime") is >> limits.time[WHITE];
137 else if (token == "btime") is >> limits.time[BLACK];
138 else if (token == "winc") is >> limits.inc[WHITE];
139 else if (token == "binc") is >> limits.inc[BLACK];
140 else if (token == "movestogo") is >> limits.movestogo;
141 else if (token == "depth") is >> limits.depth;
142 else if (token == "nodes") is >> limits.nodes;
143 else if (token == "movetime") is >> limits.movetime;
144 else if (token == "mate") is >> limits.mate;
145 else if (token == "perft") is >> limits.perft;
146 else if (token == "infinite") limits.infinite = 1;
147 else if (token == "ponder") ponderMode = true;
149 Threads.start_thinking(pos, states, limits, ponderMode);
153 // bench() is called when the engine receives the "bench" command.
154 // Firstly, a list of UCI commands is set up according to the bench
155 // parameters, then it is run one by one, printing a summary at the end.
157 void bench(Position& pos, istream& args, StateListPtr& states) {
160 uint64_t num, nodes = 0, cnt = 1;
162 vector<string> list = setup_bench(pos, args);
163 num = count_if(list.begin(), list.end(), [](const string& s) { return s.find("go ") == 0 || s.find("eval") == 0; });
165 TimePoint elapsed = now();
167 for (const auto& cmd : list)
169 istringstream is(cmd);
170 is >> skipws >> token;
172 if (token == "go" || token == "eval")
174 cerr << "\nPosition: " << cnt++ << '/' << num << " (" << pos.fen() << ")" << endl;
178 Threads.main()->wait_for_search_finished();
179 nodes += Threads.nodes_searched();
184 else if (token == "setoption") setoption(is);
185 else if (token == "position") position(pos, is, states);
186 else if (token == "ucinewgame") { Search::clear(); elapsed = now(); } // Search::clear() may take a while
189 elapsed = now() - elapsed + 1; // Ensure positivity to avoid a 'divide by zero'
193 cerr << "\n==========================="
194 << "\nTotal time (ms) : " << elapsed
195 << "\nNodes searched : " << nodes
196 << "\nNodes/second : " << 1000 * nodes / elapsed << endl;
199 // The win rate model returns the probability of winning (in per mille units) given an
200 // eval and a game ply. It fits the LTC fishtest statistics rather accurately.
201 int win_rate_model(Value v, int ply) {
203 // The model only captures up to 240 plies, so limit the input and then rescale
204 double m = std::min(240, ply) / 64.0;
206 // The coefficients of a third-order polynomial fit is based on the fishtest data
207 // for two parameters that need to transform eval to the argument of a logistic
209 constexpr double as[] = { 0.33677609, -4.30175627, 33.08810557, 365.60223431};
210 constexpr double bs[] = { -2.50471102, 14.23235405, -14.33066859, 71.42705250 };
212 // Enforce that NormalizeToPawnValue corresponds to a 50% win rate at ply 64
213 static_assert(UCI::NormalizeToPawnValue == int(as[0] + as[1] + as[2] + as[3]));
215 double a = (((as[0] * m + as[1]) * m + as[2]) * m) + as[3];
216 double b = (((bs[0] * m + bs[1]) * m + bs[2]) * m) + bs[3];
218 // Transform the eval to centipawns with limited range
219 double x = std::clamp(double(v), -4000.0, 4000.0);
221 // Return the win rate in per mille units rounded to the nearest value
222 return int(0.5 + 1000 / (1 + std::exp((a - x) / b)));
228 /// UCI::loop() waits for a command from the stdin, parses it and then calls the appropriate
229 /// function. It also intercepts an end-of-file (EOF) indication from the stdin to ensure a
230 /// graceful exit if the GUI dies unexpectedly. When called with some command-line arguments,
231 /// like running 'bench', the function returns immediately after the command is executed.
232 /// In addition to the UCI ones, some additional debug commands are also supported.
234 void UCI::loop(int argc, char* argv[]) {
238 StateListPtr states(new std::deque<StateInfo>(1));
240 pos.set(StartFEN, false, &states->back(), Threads.main());
242 for (int i = 1; i < argc; ++i)
243 cmd += std::string(argv[i]) + " ";
246 if (argc == 1 && !getline(cin, cmd)) // Wait for an input or an end-of-file (EOF) indication
249 istringstream is(cmd);
251 token.clear(); // Avoid a stale if getline() returns nothing or a blank line
252 is >> skipws >> token;
258 // The GUI sends 'ponderhit' to tell that the user has played the expected move.
259 // So, 'ponderhit' is sent if pondering was done on the same move that the user
260 // has played. The search should continue, but should also switch from pondering
261 // to the normal search.
262 else if (token == "ponderhit")
263 Threads.main()->ponder = false; // Switch to the normal search
265 else if (token == "uci")
266 sync_cout << "id name " << engine_info(true)
268 << "\nuciok" << sync_endl;
270 else if (token == "setoption") setoption(is);
271 else if (token == "go") go(pos, is, states);
272 else if (token == "position") position(pos, is, states);
273 else if (token == "ucinewgame") Search::clear();
274 else if (token == "isready") sync_cout << "readyok" << sync_endl;
276 // Add custom non-UCI commands, mainly for debugging purposes.
277 // These commands must not be used during a search!
278 else if (token == "flip") pos.flip();
279 else if (token == "bench") bench(pos, is, states);
280 else if (token == "d") sync_cout << pos << sync_endl;
281 else if (token == "eval") trace_eval(pos);
282 else if (token == "compiler") sync_cout << compiler_info() << sync_endl;
283 else if (token == "export_net")
285 std::optional<std::string> filename;
287 if (is >> skipws >> f)
289 Eval::NNUE::save_eval(filename);
291 else if (token == "--help" || token == "help" || token == "--license" || token == "license")
292 sync_cout << "\nStockfish is a powerful chess engine for playing and analyzing."
293 "\nIt is released as free software licensed under the GNU GPLv3 License."
294 "\nStockfish is normally used with a graphical user interface (GUI) and implements"
295 "\nthe Universal Chess Interface (UCI) protocol to communicate with a GUI, an API, etc."
296 "\nFor any further information, visit https://github.com/official-stockfish/Stockfish#readme"
297 "\nor read the corresponding README.md and Copying.txt files distributed along with this program.\n" << sync_endl;
298 else if (!token.empty() && token[0] != '#')
299 sync_cout << "Unknown command: '" << cmd << "'. Type help for more information." << sync_endl;
301 } while (token != "quit" && argc == 1); // The command-line arguments are one-shot
305 /// UCI::value() converts a Value to a string by adhering to the UCI protocol specification:
307 /// cp <x> The score from the engine's point of view in centipawns.
308 /// mate <y> Mate in 'y' moves (not plies). If the engine is getting mated,
309 /// uses negative values for 'y'.
311 string UCI::value(Value v) {
313 assert(-VALUE_INFINITE < v && v < VALUE_INFINITE);
317 if (abs(v) < VALUE_TB_WIN_IN_MAX_PLY)
318 ss << "cp " << v * 100 / NormalizeToPawnValue;
319 else if (abs(v) < VALUE_MATE_IN_MAX_PLY)
321 const int ply = VALUE_MATE_IN_MAX_PLY - 1 - std::abs(v); // recompute ss->ply
322 ss << "cp " << (v > 0 ? 20000 - ply : -20000 + ply);
325 ss << "mate " << (v > 0 ? VALUE_MATE - v + 1 : -VALUE_MATE - v) / 2;
331 /// UCI::wdl() reports the win-draw-loss (WDL) statistics given an evaluation
332 /// and a game ply based on the data gathered for fishtest LTC games.
334 string UCI::wdl(Value v, int ply) {
338 int wdl_w = win_rate_model( v, ply);
339 int wdl_l = win_rate_model(-v, ply);
340 int wdl_d = 1000 - wdl_w - wdl_l;
341 ss << " wdl " << wdl_w << " " << wdl_d << " " << wdl_l;
347 /// UCI::square() converts a Square to a string in algebraic notation (g1, a7, etc.)
349 std::string UCI::square(Square s) {
350 return std::string{ char('a' + file_of(s)), char('1' + rank_of(s)) };
354 /// UCI::move() converts a Move to a string in coordinate notation (g1f3, a7a8q).
355 /// The only special case is castling where the e1g1 notation is printed in
356 /// standard chess mode and in e1h1 notation it is printed in Chess960 mode.
357 /// Internally, all castling moves are always encoded as 'king captures rook'.
359 string UCI::move(Move m, bool chess960) {
361 Square from = from_sq(m);
362 Square to = to_sq(m);
370 if (type_of(m) == CASTLING && !chess960)
371 to = make_square(to > from ? FILE_G : FILE_C, rank_of(from));
373 string move = UCI::square(from) + UCI::square(to);
375 if (type_of(m) == PROMOTION)
376 move += " pnbrqk"[promotion_type(m)];
382 /// UCI::to_move() converts a string representing a move in coordinate notation
383 /// (g1f3, a7a8q) to the corresponding legal Move, if any.
385 Move UCI::to_move(const Position& pos, string& str) {
387 if (str.length() == 5)
388 str[4] = char(tolower(str[4])); // The promotion piece character must be lowercased
390 for (const auto& m : MoveList<LEGAL>(pos))
391 if (str == UCI::move(m, pos.is_chess960()))
397 } // namespace Stockfish