/*
Stockfish, a UCI chess playing engine derived from Glaurung 2.1
- Copyright (C) 2004-2023 The Stockfish developers (see AUTHORS file)
+ Copyright (C) 2004-2024 The Stockfish developers (see AUTHORS file)
Stockfish is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
#include "uci.h"
#include <algorithm>
-#include <cassert>
#include <cctype>
#include <cmath>
#include <cstdint>
-#include <cstdlib>
-#include <deque>
-#include <iostream>
-#include <memory>
#include <optional>
#include <sstream>
-#include <string>
+#include <string_view>
+#include <utility>
#include <vector>
#include "benchmark.h"
-#include "evaluate.h"
-#include "misc.h"
+#include "engine.h"
#include "movegen.h"
-#include "nnue/evaluate_nnue.h"
#include "position.h"
+#include "score.h"
#include "search.h"
-#include "thread.h"
+#include "types.h"
+#include "ucioption.h"
namespace Stockfish {
-namespace {
-
-// FEN string for the initial position in standard chess
-const char* StartFEN = "rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR w KQkq - 0 1";
-
-
-// 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, std::istringstream& is, StateListPtr& states) {
-
- Move m;
- std::string token, fen;
+constexpr auto StartFEN = "rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR w KQkq - 0 1";
+template<typename... Ts>
+struct overload: Ts... {
+ using Ts::operator()...;
+};
- is >> token;
+template<typename... Ts>
+overload(Ts...) -> overload<Ts...>;
- if (token == "startpos")
+void UCIEngine::print_info_string(const std::string& str) {
+ sync_cout_start();
+ for (auto& line : split(str, "\n"))
{
- fen = StartFEN;
- is >> token; // Consume the "moves" token, if any
+ if (!is_whitespace(line))
+ {
+ std::cout << "info string " << line << '\n';
+ }
}
- else if (token == "fen")
- while (is >> token && token != "moves")
- fen += token + " ";
- else
- return;
+ sync_cout_end();
+}
- 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());
+UCIEngine::UCIEngine(int argc, char** argv) :
+ engine(argv[0]),
+ cli(argc, argv) {
- // Parse the move list, if any
- while (is >> token && (m = UCI::to_move(pos, token)) != MOVE_NONE)
- {
- states->emplace_back();
- pos.do_move(m, states->back());
- }
-}
+ engine.get_options().add_info_listener([](const std::optional<std::string>& str) {
+ if (str.has_value())
+ print_info_string(*str);
+ });
-// Prints the evaluation of the current position, consistent with
-// the UCI options set so far.
-void trace_eval(Position& pos) {
+ engine.set_on_iter([](const auto& i) { on_iter(i); });
+ engine.set_on_update_no_moves([](const auto& i) { on_update_no_moves(i); });
+ engine.set_on_update_full(
+ [this](const auto& i) { on_update_full(i, engine.get_options()["UCI_ShowWDL"]); });
+ engine.set_on_bestmove([](const auto& bm, const auto& p) { on_bestmove(bm, p); });
+}
- StateListPtr states(new std::deque<StateInfo>(1));
- Position p;
- p.set(pos.fen(), Options["UCI_Chess960"], &states->back(), Threads.main());
+void UCIEngine::loop() {
+ std::string token, cmd;
- Eval::NNUE::verify();
+ for (int i = 1; i < cli.argc; ++i)
+ cmd += std::string(cli.argv[i]) + " ";
- sync_cout << "\n" << Eval::trace(p) << sync_endl;
-}
+ do
+ {
+ if (cli.argc == 1
+ && !getline(std::cin, cmd)) // Wait for an input or an end-of-file (EOF) indication
+ cmd = "quit";
+ std::istringstream is(cmd);
-// Called when the engine receives the "setoption" UCI command.
-// The function updates the UCI option ("name") to the given value ("value").
+ token.clear(); // Avoid a stale if getline() returns nothing or a blank line
+ is >> std::skipws >> token;
-void setoption(std::istringstream& is) {
+ if (token == "quit" || token == "stop")
+ engine.stop();
- Threads.main()->wait_for_search_finished();
+ // 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")
+ engine.set_ponderhit(false);
- std::string token, name, value;
+ else if (token == "uci")
+ {
+ sync_cout << "id name " << engine_info(true) << "\n"
+ << engine.get_options() << sync_endl;
- is >> token; // Consume the "name" token
+ sync_cout << "uciok" << sync_endl;
+ }
- // Read the option name (can contain spaces)
- while (is >> token && token != "value")
- name += (name.empty() ? "" : " ") + token;
+ else if (token == "setoption")
+ setoption(is);
+ else if (token == "go")
+ {
+ // send info strings after the go command is sent for old GUIs and python-chess
+ print_info_string(engine.numa_config_information_as_string());
+ print_info_string(engine.thread_binding_information_as_string());
+ go(is);
+ }
+ else if (token == "position")
+ position(is);
+ else if (token == "ucinewgame")
+ engine.search_clear();
+ else if (token == "isready")
+ sync_cout << "readyok" << sync_endl;
- // Read the option value (can contain spaces)
- while (is >> token)
- value += (value.empty() ? "" : " ") + token;
+ // Add custom non-UCI commands, mainly for debugging purposes.
+ // These commands must not be used during a search!
+ else if (token == "flip")
+ engine.flip();
+ else if (token == "bench")
+ bench(is);
+ else if (token == "d")
+ sync_cout << engine.visualize() << sync_endl;
+ else if (token == "eval")
+ engine.trace_eval();
+ else if (token == "compiler")
+ sync_cout << compiler_info() << sync_endl;
+ else if (token == "export_net")
+ {
+ std::pair<std::optional<std::string>, std::string> files[2];
- if (Options.count(name))
- Options[name] = value;
- else
- sync_cout << "No such option: " << name << sync_endl;
-}
+ if (is >> std::skipws >> files[0].second)
+ files[0].first = files[0].second;
+ if (is >> std::skipws >> files[1].second)
+ files[1].first = files[1].second;
-// 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.
+ engine.save_network(files);
+ }
+ 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;
-void go(Position& pos, std::istringstream& is, StateListPtr& states) {
+ } while (token != "quit" && cli.argc == 1); // The command-line arguments are one-shot
+}
+Search::LimitsType UCIEngine::parse_limits(std::istream& is) {
Search::LimitsType limits;
std::string token;
- bool ponderMode = false;
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
while (is >> token)
- limits.searchmoves.push_back(UCI::to_move(pos, token));
+ limits.searchmoves.push_back(to_lower(token));
else if (token == "wtime")
is >> limits.time[WHITE];
else if (token == "infinite")
limits.infinite = 1;
else if (token == "ponder")
- ponderMode = true;
+ limits.ponderMode = true;
- Threads.start_thinking(pos, states, limits, ponderMode);
+ return limits;
}
+void UCIEngine::go(std::istringstream& is) {
-// Called when the engine receives the "bench" command.
-// First, 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.
+ Search::LimitsType limits = parse_limits(is);
-void bench(Position& pos, std::istream& args, StateListPtr& states) {
+ if (limits.perft)
+ perft(limits);
+ else
+ engine.go(limits);
+}
+void UCIEngine::bench(std::istream& args) {
std::string token;
uint64_t num, nodes = 0, cnt = 1;
+ uint64_t nodesSearched = 0;
+ const auto& options = engine.get_options();
+
+ engine.set_on_update_full([&](const auto& i) {
+ nodesSearched = i.nodes;
+ on_update_full(i, options["UCI_ShowWDL"]);
+ });
+
+ std::vector<std::string> list = Benchmark::setup_bench(engine.fen(), args);
- std::vector<std::string> list = setup_bench(pos, args);
- num = count_if(list.begin(), list.end(),
- [](const std::string& s) { return s.find("go ") == 0 || s.find("eval") == 0; });
+ num = count_if(list.begin(), list.end(),
+ [](const std::string& s) { return s.find("go ") == 0 || s.find("eval") == 0; });
TimePoint elapsed = now();
if (token == "go" || token == "eval")
{
- std::cerr << "\nPosition: " << cnt++ << '/' << num << " (" << pos.fen() << ")"
+ std::cerr << "\nPosition: " << cnt++ << '/' << num << " (" << engine.fen() << ")"
<< std::endl;
if (token == "go")
{
- go(pos, is, states);
- Threads.main()->wait_for_search_finished();
- nodes += Threads.nodes_searched();
+ Search::LimitsType limits = parse_limits(is);
+
+ if (limits.perft)
+ nodesSearched = perft(limits);
+ else
+ {
+ engine.go(limits);
+ engine.wait_for_search_finished();
+ }
+
+ nodes += nodesSearched;
+ nodesSearched = 0;
}
else
- trace_eval(pos);
+ engine.trace_eval();
}
else if (token == "setoption")
setoption(is);
else if (token == "position")
- position(pos, is, states);
+ position(is);
else if (token == "ucinewgame")
{
- Search::clear();
+ engine.search_clear(); // search_clear may take a while
elapsed = now();
- } // Search::clear() may take a while
+ }
}
elapsed = now() - elapsed + 1; // Ensure positivity to avoid a 'divide by zero'
dbg_print();
- std::cerr << "\n==========================="
- << "\nTotal time (ms) : " << elapsed << "\nNodes searched : " << nodes
+ std::cerr << "\n===========================" //
+ << "\nTotal time (ms) : " << elapsed //
+ << "\nNodes searched : " << nodes //
<< "\nNodes/second : " << 1000 * nodes / elapsed << std::endl;
-}
-
-// 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;
+ // reset callback, to not capture a dangling reference to nodesSearched
+ engine.set_on_update_full([&](const auto& i) { on_update_full(i, options["UCI_ShowWDL"]); });
+}
- // 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[] = {0.38036525, -2.82015070, 23.17882135, 307.36768407};
- constexpr double bs[] = {-2.29434733, 13.27689788, -14.26828904, 63.45318330};
- // 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]));
+void UCIEngine::setoption(std::istringstream& is) {
+ engine.wait_for_search_finished();
+ engine.get_options().setoption(is);
+}
- 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];
+std::uint64_t UCIEngine::perft(const Search::LimitsType& limits) {
+ auto nodes = engine.perft(engine.fen(), limits.perft, engine.get_options()["UCI_Chess960"]);
+ sync_cout << "\nNodes searched: " << nodes << "\n" << sync_endl;
+ return nodes;
+}
- // Transform the eval to centipawns with limited range
- double x = std::clamp(double(v), -4000.0, 4000.0);
+void UCIEngine::position(std::istringstream& is) {
+ std::string token, fen;
- // Return the win rate in per mille units, rounded to the nearest integer
- return int(0.5 + 1000 / (1 + std::exp((a - x) / b)));
-}
+ is >> token;
-} // namespace
+ if (token == "startpos")
+ {
+ fen = StartFEN;
+ is >> token; // Consume the "moves" token, if any
+ }
+ else if (token == "fen")
+ while (is >> token && token != "moves")
+ fen += token + " ";
+ else
+ return;
+ std::vector<std::string> moves;
-// 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[]) {
+ while (is >> token)
+ {
+ moves.push_back(token);
+ }
- Position pos;
- std::string token, cmd;
- StateListPtr states(new std::deque<StateInfo>(1));
+ engine.set_position(fen, moves);
+}
- pos.set(StartFEN, false, &states->back(), Threads.main());
+namespace {
- for (int i = 1; i < argc; ++i)
- cmd += std::string(argv[i]) + " ";
+struct WinRateParams {
+ double a;
+ double b;
+};
- do
- {
- if (argc == 1
- && !getline(std::cin, cmd)) // Wait for an input or an end-of-file (EOF) indication
- cmd = "quit";
+WinRateParams win_rate_params(const Position& pos) {
- std::istringstream is(cmd);
+ int material = pos.count<PAWN>() + 3 * pos.count<KNIGHT>() + 3 * pos.count<BISHOP>()
+ + 5 * pos.count<ROOK>() + 9 * pos.count<QUEEN>();
- token.clear(); // Avoid a stale if getline() returns nothing or a blank line
- is >> std::skipws >> token;
+ // The fitted model only uses data for material counts in [17, 78], and is anchored at count 58.
+ double m = std::clamp(material, 17, 78) / 58.0;
- if (token == "quit" || token == "stop")
- Threads.stop = true;
+ // Return a = p_a(material) and b = p_b(material), see github.com/official-stockfish/WDL_model
+ constexpr double as[] = {-37.45051876, 121.19101539, -132.78783573, 420.70576692};
+ constexpr double bs[] = {90.26261072, -137.26549898, 71.10130540, 51.35259597};
- // 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
+ 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];
- else if (token == "uci")
- sync_cout << "id name " << engine_info(true) << "\n"
- << Options << "\nuciok" << sync_endl;
+ return {a, b};
+}
- 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;
+// The win rate model is 1 / (1 + exp((a - eval) / b)), where a = p_a(material) and b = p_b(material).
+// It fits the LTC fishtest statistics rather accurately.
+int win_rate_model(Value v, const Position& pos) {
- // 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 >> std::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;
+ auto [a, b] = win_rate_params(pos);
- } while (token != "quit" && argc == 1); // The command-line arguments are one-shot
+ // Return the win rate in per mille units, rounded to the nearest integer.
+ return int(0.5 + 1000 / (1 + std::exp((a - double(v)) / b)));
+}
}
+std::string UCIEngine::format_score(const Score& s) {
+ constexpr int TB_CP = 20000;
+ const auto format =
+ overload{[](Score::Mate mate) -> std::string {
+ auto m = (mate.plies > 0 ? (mate.plies + 1) : mate.plies) / 2;
+ return std::string("mate ") + std::to_string(m);
+ },
+ [](Score::Tablebase tb) -> std::string {
+ return std::string("cp ")
+ + std::to_string((tb.win ? TB_CP - tb.plies : -TB_CP - tb.plies));
+ },
+ [](Score::InternalUnits units) -> std::string {
+ return std::string("cp ") + std::to_string(units.value);
+ }};
+
+ return s.visit(format);
+}
// Turns a Value to an integer centipawn number,
// without treatment of mate and similar special scores.
-int UCI::to_cp(Value v) { return 100 * v / UCI::NormalizeToPawnValue; }
+int UCIEngine::to_cp(Value v, const Position& pos) {
-// 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,
-// uses negative values for 'y'.
-std::string UCI::value(Value v) {
+ // In general, the score can be defined via the WDL as
+ // (log(1/L - 1) - log(1/W - 1)) / (log(1/L - 1) + log(1/W - 1)).
+ // Based on our win_rate_model, this simply yields v / a.
- assert(-VALUE_INFINITE < v && v < VALUE_INFINITE);
+ auto [a, b] = win_rate_params(pos);
- std::stringstream ss;
-
- if (abs(v) < VALUE_TB_WIN_IN_MAX_PLY)
- ss << "cp " << UCI::to_cp(v);
- else if (abs(v) < VALUE_MATE_IN_MAX_PLY)
- {
- const int ply = VALUE_MATE_IN_MAX_PLY - 1 - std::abs(v); // recompute ss->ply
- ss << "cp " << (v > 0 ? 20000 - ply : -20000 + ply);
- }
- else
- ss << "mate " << (v > 0 ? VALUE_MATE - v + 1 : -VALUE_MATE - v) / 2;
-
- return ss.str();
+ return std::round(100 * int(v) / a);
}
-
-// Reports the win-draw-loss (WDL) statistics given an evaluation
-// and a game ply based on the data gathered for fishtest LTC games.
-std::string UCI::wdl(Value v, int ply) {
-
+std::string UCIEngine::wdl(Value v, const Position& pos) {
std::stringstream ss;
- int wdl_w = win_rate_model(v, ply);
- int wdl_l = win_rate_model(-v, ply);
+ int wdl_w = win_rate_model(v, pos);
+ int wdl_l = win_rate_model(-v, pos);
int wdl_d = 1000 - wdl_w - wdl_l;
- ss << " wdl " << wdl_w << " " << wdl_d << " " << wdl_l;
+ ss << wdl_w << " " << wdl_d << " " << wdl_l;
return ss.str();
}
-
-// Converts a Square to a string in algebraic notation (g1, a7, etc.)
-std::string UCI::square(Square s) {
+std::string UCIEngine::square(Square s) {
return std::string{char('a' + file_of(s)), char('1' + rank_of(s))};
}
-
-// Converts a Move to a string in coordinate notation (g1f3, a7a8q).
-// 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'.
-std::string UCI::move(Move m, bool chess960) {
-
- if (m == MOVE_NONE)
+std::string UCIEngine::move(Move m, bool chess960) {
+ if (m == Move::none())
return "(none)";
- if (m == MOVE_NULL)
+ if (m == Move::null())
return "0000";
- Square from = from_sq(m);
- Square to = to_sq(m);
+ Square from = m.from_sq();
+ Square to = m.to_sq();
- if (type_of(m) == CASTLING && !chess960)
+ if (m.type_of() == CASTLING && !chess960)
to = make_square(to > from ? FILE_G : FILE_C, rank_of(from));
- std::string move = UCI::square(from) + UCI::square(to);
+ std::string move = square(from) + square(to);
- if (type_of(m) == PROMOTION)
- move += " pnbrqk"[promotion_type(m)];
+ if (m.type_of() == PROMOTION)
+ move += " pnbrqk"[m.promotion_type()];
return move;
}
-// Converts a string representing a move in coordinate notation
-// (g1f3, a7a8q) to the corresponding legal Move, if any.
-Move UCI::to_move(const Position& pos, std::string& str) {
+std::string UCIEngine::to_lower(std::string str) {
+ std::transform(str.begin(), str.end(), str.begin(), [](auto c) { return std::tolower(c); });
+
+ return str;
+}
- if (str.length() == 5)
- str[4] = char(tolower(str[4])); // The promotion piece character must be lowercased
+Move UCIEngine::to_move(const Position& pos, std::string str) {
+ str = to_lower(str);
for (const auto& m : MoveList<LEGAL>(pos))
- if (str == UCI::move(m, pos.is_chess960()))
+ if (str == move(m, pos.is_chess960()))
return m;
- return MOVE_NONE;
+ return Move::none();
+}
+
+void UCIEngine::on_update_no_moves(const Engine::InfoShort& info) {
+ sync_cout << "info depth " << info.depth << " score " << format_score(info.score) << sync_endl;
+}
+
+void UCIEngine::on_update_full(const Engine::InfoFull& info, bool showWDL) {
+ std::stringstream ss;
+
+ ss << "info";
+ ss << " depth " << info.depth //
+ << " seldepth " << info.selDepth //
+ << " multipv " << info.multiPV //
+ << " score " << format_score(info.score); //
+
+ if (showWDL)
+ ss << " wdl " << info.wdl;
+
+ if (!info.bound.empty())
+ ss << " " << info.bound;
+
+ ss << " nodes " << info.nodes //
+ << " nps " << info.nps //
+ << " hashfull " << info.hashfull //
+ << " tbhits " << info.tbHits //
+ << " time " << info.timeMs //
+ << " pv " << info.pv; //
+
+ sync_cout << ss.str() << sync_endl;
+}
+
+void UCIEngine::on_iter(const Engine::InfoIter& info) {
+ std::stringstream ss;
+
+ ss << "info";
+ ss << " depth " << info.depth //
+ << " currmove " << info.currmove //
+ << " currmovenumber " << info.currmovenumber; //
+
+ sync_cout << ss.str() << sync_endl;
+}
+
+void UCIEngine::on_bestmove(std::string_view bestmove, std::string_view ponder) {
+ sync_cout << "bestmove " << bestmove;
+ if (!ponder.empty())
+ std::cout << " ponder " << ponder;
+ std::cout << sync_endl;
}
} // namespace Stockfish