namespace {
- // FEN string of the initial position, normal chess
+ // FEN string for the initial position in standard chess
const char* StartFEN = "rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR w KQkq - 0 1";
- // position() is called when engine receives the "position" UCI command.
- // The function sets up the position described in the given FEN string ("fen")
- // or the starting position ("startpos") and then makes the moves given in the
- // following move list ("moves").
+ // position() is called when the engine receives the "position" UCI command.
+ // It sets up the position that is described in the given FEN string ("fen") or
+ // the initial position ("startpos") and then makes the moves given in the following
+ // move list ("moves").
void position(Position& pos, istringstream& is, StateListPtr& states) {
if (token == "startpos")
{
fen = StartFEN;
- is >> token; // Consume "moves" token if any
+ is >> token; // Consume the "moves" token, if any
}
else if (token == "fen")
while (is >> token && token != "moves")
else
return;
- states = StateListPtr(new std::deque<StateInfo>(1)); // Drop old and create a new one
+ states = StateListPtr(new std::deque<StateInfo>(1)); // Drop the old state and create a new one
pos.set(fen, Options["UCI_Chess960"], &states->back(), Threads.main());
- // Parse move list (if any)
+ // Parse the move list, if any
while (is >> token && (m = UCI::to_move(pos, token)) != MOVE_NONE)
{
states->emplace_back();
}
}
- // trace_eval() prints the evaluation for the current position, consistent with the UCI
- // options set so far.
+ // trace_eval() prints the evaluation of the current position, consistent with
+ // the UCI options set so far.
void trace_eval(Position& pos) {
}
- // setoption() is called when engine receives the "setoption" UCI command. The
- // function updates the UCI option ("name") to the given value ("value").
+ // setoption() is called when the engine receives the "setoption" UCI command.
+ // The function updates the UCI option ("name") to the given value ("value").
void setoption(istringstream& is) {
string token, name, value;
- is >> token; // Consume "name" token
+ is >> token; // Consume the "name" token
- // Read option name (can contain spaces)
+ // Read the option name (can contain spaces)
while (is >> token && token != "value")
name += (name.empty() ? "" : " ") + token;
- // Read option value (can contain spaces)
+ // Read the option value (can contain spaces)
while (is >> token)
value += (value.empty() ? "" : " ") + token;
}
- // go() is called when engine receives the "go" UCI command. The function sets
- // the thinking time and other parameters from the input string, then starts
- // the search.
+ // go() is called when the engine receives the "go" UCI command. The function
+ // sets the thinking time and other parameters from the input string, then starts
+ // with a search.
void go(Position& pos, istringstream& is, StateListPtr& states) {
string token;
bool ponderMode = false;
- limits.startTime = now(); // As early as possible!
+ limits.startTime = now(); // The search starts as early as possible
while (is >> token)
if (token == "searchmoves") // Needs to be the last command on the line
}
- // bench() is called when engine receives the "bench" command. Firstly
- // a list of UCI commands is setup according to bench parameters, then
- // it is run one by one printing a summary at the end.
+ // bench() is called when the engine receives the "bench" command.
+ // Firstly, a list of UCI commands is set up according to the bench
+ // parameters, then it is run one by one, printing a summary at the end.
void bench(Position& pos, istream& args, StateListPtr& states) {
}
else if (token == "setoption") setoption(is);
else if (token == "position") position(pos, is, states);
- else if (token == "ucinewgame") { Search::clear(); elapsed = now(); } // Search::clear() may take some while
+ else if (token == "ucinewgame") { Search::clear(); elapsed = now(); } // Search::clear() may take a while
}
elapsed = now() - elapsed + 1; // Ensure positivity to avoid a 'divide by zero'
- dbg_print(); // Just before exiting
+ dbg_print();
cerr << "\n==========================="
<< "\nTotal time (ms) : " << elapsed
<< "\nNodes/second : " << 1000 * nodes / elapsed << endl;
}
- // The win rate model returns the probability (per mille) of winning given an eval
- // and a game-ply. The model fits rather accurately the LTC fishtest statistics.
+ // 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 captures only up to 240 plies, so limit input (and rescale)
+ // The model only captures up to 240 plies, so limit the input and then rescale
double m = std::min(240, ply) / 64.0;
- // 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.
+ // 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};
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
+ // Transform the eval to centipawns with limited range
double x = std::clamp(double(100 * v) / PawnValueEg, -2000.0, 2000.0);
- // Return win rate in per mille (rounded to nearest)
+ // 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 stdin, parses it and calls the appropriate
-/// function. Also intercepts EOF from stdin to ensure gracefully exiting if the
-/// GUI dies unexpectedly. When called with some command line arguments, e.g. to
-/// run 'bench', once the command is executed the function returns immediately.
-/// In addition to the UCI ones, also some additional debug commands are supported.
+/// 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[]) {
cmd += std::string(argv[i]) + " ";
do {
- if (argc == 1 && !getline(cin, cmd)) // Block here waiting for input or EOF
+ 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 empty or blank line
+ 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 us the user has played the expected move.
- // So 'ponderhit' will be sent if we were told to ponder on the same move the
- // user has played. We should continue searching but switch from pondering to
- // normal search.
+ // 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 normal search
+ Threads.main()->ponder = false; // Switch to the normal search
else if (token == "uci")
sync_cout << "id name " << engine_info(true)
else if (token == "ucinewgame") Search::clear();
else if (token == "isready") sync_cout << "readyok" << sync_endl;
- // Additional custom non-UCI commands, mainly for debugging.
- // Do not use these commands during a search!
+ // 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;
Eval::NNUE::save_eval(filename);
}
else if (token == "--help" || token == "help" || token == "--license" || token == "license")
- sync_cout << "\nStockfish is a powerful chess engine and free software licensed under the GNU GPLv3."
- "\nStockfish is normally used with a separate graphical user interface (GUI)."
- "\nStockfish implements the universal chess interface (UCI) to exchange information."
- "\nFor further information see https://github.com/official-stockfish/Stockfish#readme"
- "\nor the corresponding README.md and Copying.txt files distributed with this program.\n" << sync_endl;
+ 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); // Command line args are one-shot
+ } while (token != "quit" && argc == 1); // The command-line arguments are one-shot
}
-/// UCI::value() converts a Value to a string suitable for use with the UCI
-/// protocol specification:
+/// UCI::value() converts a Value to a string by adhering to the UCI protocol specification:
///
/// cp <x> The score from the engine's point of view in centipawns.
-/// mate <y> Mate in y moves, not plies. If the engine is getting mated
-/// use negative values for y.
+/// mate <y> Mate in 'y' moves (not plies). If the engine is getting mated,
+/// uses negative values for 'y'.
string UCI::value(Value v) {
}
-/// UCI::wdl() report WDL statistics given an evaluation and a game ply, based on
-/// data gathered for fishtest LTC games.
+/// UCI::wdl() reports the win-draw-loss (WDL) statistics given an evaluation
+/// and a game ply based on the data gathered for fishtest LTC games.
string UCI::wdl(Value v, int ply) {
/// UCI::move() converts a Move to a string in coordinate notation (g1f3, a7a8q).
-/// The only special case is castling, where we print in the e1g1 notation in
-/// normal chess mode, and in e1h1 notation in chess960 mode. Internally all
-/// castling moves are always encoded as 'king captures rook'.
+/// The only special case is castling where the e1g1 notation is printed in
+/// standard chess mode and in e1h1 notation it is printed in Chess960 mode.
+/// Internally, all castling moves are always encoded as 'king captures rook'.
string UCI::move(Move m, bool chess960) {
Move UCI::to_move(const Position& pos, string& str) {
- if (str.length() == 5) // Junior could send promotion piece in uppercase
- str[4] = char(tolower(str[4]));
+ if (str.length() == 5)
+ str[4] = char(tolower(str[4])); // The promotion piece character must be lowercased
for (const auto& m : MoveList<LEGAL>(pos))
if (str == UCI::move(m, pos.is_chess960()))
projects / stockfish / commitdiff