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) 2015-2017 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
27 #include "syzygy/tbprobe.h"
29 ThreadPool Threads; // Global object
32 /// Thread constructor launches the thread and waits until it goes to sleep
33 /// in idle_loop(). Note that 'searching' and 'exit' should be alredy set.
35 Thread::Thread(size_t n) : idx(n), stdThread(&Thread::idle_loop, this) {
37 wait_for_search_finished();
41 /// Thread destructor wakes up the thread in idle_loop() and waits
42 /// for its termination. Thread should be already waiting.
54 /// Thread::start_searching() wakes up the thread that will start the search
56 void Thread::start_searching() {
58 std::lock_guard<Mutex> lk(mutex);
60 cv.notify_one(); // Wake up the thread in idle_loop()
64 /// Thread::wait_for_search_finished() blocks on the condition variable
65 /// until the thread has finished searching.
67 void Thread::wait_for_search_finished() {
69 std::unique_lock<Mutex> lk(mutex);
70 cv.wait(lk, [&]{ return !searching; });
74 /// Thread::idle_loop() is where the thread is parked, blocked on the
75 /// condition variable, when it has no work to do.
77 void Thread::idle_loop() {
79 WinProcGroup::bindThisThread(idx);
83 std::unique_lock<Mutex> lk(mutex);
85 cv.notify_one(); // Wake up anyone waiting for search finished
86 cv.wait(lk, [&]{ return searching; });
98 /// ThreadPool::init() creates and launches the threads that will go
99 /// immediately to sleep in idle_loop. We cannot use the c'tor because
100 /// Threads is a static object and we need a fully initialized engine at
101 /// this point due to allocation of Endgames in the Thread constructor.
103 void ThreadPool::init(size_t requested) {
105 push_back(new MainThread(0));
110 /// ThreadPool::exit() terminates threads before the program exits. Cannot be
111 /// done in the destructor because threads must be terminated before deleting
112 /// any static object, so before main() returns.
114 void ThreadPool::exit() {
116 main()->wait_for_search_finished();
121 /// ThreadPool::set() creates/destroys threads to match the requested number
123 void ThreadPool::set(size_t requested) {
125 while (size() < requested)
126 push_back(new Thread(size()));
128 while (size() > requested)
129 delete back(), pop_back();
133 /// ThreadPool::start_thinking() wakes up main thread waiting in idle_loop() and
134 /// returns immediately. Main thread will wake up other threads and start the search.
136 void ThreadPool::start_thinking(Position& pos, StateListPtr& states,
137 const Search::LimitsType& limits, bool ponderMode) {
139 main()->wait_for_search_finished();
141 stopOnPonderhit = stop = false;
143 Search::Limits = limits;
144 Search::RootMoves rootMoves;
146 for (const auto& m : MoveList<LEGAL>(pos))
147 if ( limits.searchmoves.empty()
148 || std::count(limits.searchmoves.begin(), limits.searchmoves.end(), m))
149 rootMoves.emplace_back(m);
151 if (!rootMoves.empty())
152 Tablebases::filter_root_moves(pos, rootMoves);
154 // After ownership transfer 'states' becomes empty, so if we stop the search
155 // and call 'go' again without setting a new position states.get() == NULL.
156 assert(states.get() || setupStates.get());
159 setupStates = std::move(states); // Ownership transfer, states is now empty
161 // We use Position::set() to set root position across threads. So we
162 // need to save and later to restore st->previous, cleared by set().
163 // Note that setupStates is shared by threads but is accessed in read-only mode.
164 StateInfo* previous = setupStates->back().previous;
166 for (Thread* th : Threads)
168 th->nodes = th->tbHits = 0;
169 th->rootDepth = th->completedDepth = DEPTH_ZERO;
170 th->rootMoves = rootMoves;
171 th->rootPos.set(pos.fen(), pos.is_chess960(), &setupStates->back(), th);
174 setupStates->back().previous = previous;
176 main()->start_searching();