2 Stockfish, a UCI chess playing engine derived from Glaurung 2.1
3 Copyright (C) 2004-2008 Tord Romstad (Glaurung author)
4 Copyright (C) 2008-2015 Marco Costalba, Joona Kiiski, Tord Romstad
5 Copyright (C) 2015-2016 Marco Costalba, Joona Kiiski, Gary Linscott, Tord Romstad
7 Stockfish is free software: you can redistribute it and/or modify
8 it under the terms of the GNU General Public License as published by
9 the Free Software Foundation, either version 3 of the License, or
10 (at your option) any later version.
12 Stockfish is distributed in the hope that it will be useful,
13 but WITHOUT ANY WARRANTY; without even the implied warranty of
14 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
15 GNU General Public License for more details.
17 You should have received a copy of the GNU General Public License
18 along with this program. If not, see <http://www.gnu.org/licenses/>.
21 #include <algorithm> // For std::count
29 ThreadPool Threads; // Global object
31 /// Thread constructor launches the thread and then waits until it goes to sleep
36 resetCalls = exit = false;
37 maxPly = callsCnt = 0;
40 idx = Threads.size(); // Start from 0
42 std::unique_lock<Mutex> lk(mutex);
44 nativeThread = std::thread(&Thread::idle_loop, this);
45 sleepCondition.wait(lk, [&]{ return !searching; });
49 /// Thread destructor waits for thread termination before returning
55 sleepCondition.notify_one();
61 /// Thread::wait_for_search_finished() waits on sleep condition
62 /// until not searching
64 void Thread::wait_for_search_finished() {
66 std::unique_lock<Mutex> lk(mutex);
67 sleepCondition.wait(lk, [&]{ return !searching; });
71 /// Thread::wait() waits on sleep condition until condition is true
73 void Thread::wait(std::atomic_bool& condition) {
75 std::unique_lock<Mutex> lk(mutex);
76 sleepCondition.wait(lk, [&]{ return bool(condition); });
80 /// Thread::start_searching() wakes up the thread that will start the search
82 void Thread::start_searching(bool resume) {
84 std::unique_lock<Mutex> lk(mutex);
89 sleepCondition.notify_one();
93 /// Thread::idle_loop() is where the thread is parked when it has no work to do
95 void Thread::idle_loop() {
99 std::unique_lock<Mutex> lk(mutex);
103 while (!searching && !exit)
105 sleepCondition.notify_one(); // Wake up any waiting thread
106 sleepCondition.wait(lk);
117 /// ThreadPool::init() creates and launches requested threads that will go
118 /// immediately to sleep. We cannot use a constructor because Threads is a
119 /// static object and we need a fully initialized engine at this point due to
120 /// allocation of Endgames in the Thread constructor.
122 void ThreadPool::init() {
124 push_back(new MainThread);
129 /// ThreadPool::exit() terminates threads before the program exits. Cannot be
130 /// done in destructor because threads must be terminated before deleting any
131 /// static objects while still in main().
133 void ThreadPool::exit() {
136 delete back(), pop_back();
140 /// ThreadPool::read_uci_options() updates internal threads parameters from the
141 /// corresponding UCI options and creates/destroys threads to match requested
142 /// number. Thread objects are dynamically allocated.
144 void ThreadPool::read_uci_options() {
146 size_t requested = Options["Threads"];
148 assert(requested > 0);
150 while (size() < requested)
151 push_back(new Thread);
153 while (size() > requested)
154 delete back(), pop_back();
158 /// ThreadPool::nodes_searched() returns the number of nodes searched
160 int64_t ThreadPool::nodes_searched() {
163 for (Thread* th : *this)
164 nodes += th->rootPos.nodes_searched();
169 /// ThreadPool::start_thinking() wakes up the main thread sleeping in idle_loop()
170 /// and starts a new search, then returns immediately.
172 void ThreadPool::start_thinking(const Position& pos, StateListPtr& states,
173 const Search::LimitsType& limits) {
175 main()->wait_for_search_finished();
177 Search::Signals.stopOnPonderhit = Search::Signals.stop = false;
178 Search::Limits = limits;
179 Search::RootMoves rootMoves;
181 for (const auto& m : MoveList<LEGAL>(pos))
182 if ( limits.searchmoves.empty()
183 || std::count(limits.searchmoves.begin(), limits.searchmoves.end(), m))
184 rootMoves.push_back(Search::RootMove(m));
186 // After ownership transfer 'states' becomes empty, so if we stop the search
187 // and call 'go' again without setting a new position states.get() == NULL.
188 assert(states.get() || setupStates.get());
191 setupStates = std::move(states); // Ownership transfer, states is now empty
193 StateInfo tmp = setupStates->back();
195 for (Thread* th : Threads)
198 th->rootDepth = DEPTH_ZERO;
199 th->rootMoves = rootMoves;
200 th->rootPos.set(pos.fen(), pos.is_chess960(), &setupStates->back(), th);
203 setupStates->back() = tmp; // Restore st->previous, cleared by Position::set()
205 main()->start_searching();