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();
38 clear(); // Zero-init histories (based on std::array)
42 /// Thread destructor wakes up the thread in idle_loop() and waits
43 /// for its termination. Thread should be already waiting.
55 /// Thread::clear() reset histories, usually before a new game
57 void Thread::clear() {
59 counterMoves.fill(MOVE_NONE);
62 for (auto& to : contHistory)
66 contHistory[NO_PIECE][0].fill(Search::CounterMovePruneThreshold - 1);
69 /// Thread::start_searching() wakes up the thread that will start the search
71 void Thread::start_searching() {
73 std::lock_guard<Mutex> lk(mutex);
75 cv.notify_one(); // Wake up the thread in idle_loop()
79 /// Thread::wait_for_search_finished() blocks on the condition variable
80 /// until the thread has finished searching.
82 void Thread::wait_for_search_finished() {
84 std::unique_lock<Mutex> lk(mutex);
85 cv.wait(lk, [&]{ return !searching; });
89 /// Thread::idle_loop() is where the thread is parked, blocked on the
90 /// condition variable, when it has no work to do.
92 void Thread::idle_loop() {
94 WinProcGroup::bindThisThread(idx);
98 std::unique_lock<Mutex> lk(mutex);
100 cv.notify_one(); // Wake up anyone waiting for search finished
101 cv.wait(lk, [&]{ return searching; });
113 /// ThreadPool::init() creates and launches the threads that will go
114 /// immediately to sleep in idle_loop. We cannot use the constructor because
115 /// Threads is a static object and we need a fully initialized engine at
116 /// this point due to allocation of Endgames in the Thread constructor.
118 void ThreadPool::init(size_t requested) {
120 push_back(new MainThread(0));
125 /// ThreadPool::exit() terminates threads before the program exits. Cannot be
126 /// done in the destructor because threads must be terminated before deleting
127 /// any static object, so before main() returns.
129 void ThreadPool::exit() {
131 main()->wait_for_search_finished();
136 /// ThreadPool::set() creates/destroys threads to match the requested number
138 void ThreadPool::set(size_t requested) {
140 while (size() < requested)
141 push_back(new Thread(size()));
143 while (size() > requested)
144 delete back(), pop_back();
148 /// ThreadPool::start_thinking() wakes up main thread waiting in idle_loop() and
149 /// returns immediately. Main thread will wake up other threads and start the search.
151 void ThreadPool::start_thinking(Position& pos, StateListPtr& states,
152 const Search::LimitsType& limits, bool ponderMode) {
154 main()->wait_for_search_finished();
156 stopOnPonderhit = stop = false;
158 Search::Limits = limits;
159 Search::RootMoves rootMoves;
161 for (const auto& m : MoveList<LEGAL>(pos))
162 if ( limits.searchmoves.empty()
163 || std::count(limits.searchmoves.begin(), limits.searchmoves.end(), m))
164 rootMoves.emplace_back(m);
166 if (!rootMoves.empty())
167 Tablebases::filter_root_moves(pos, rootMoves);
169 // After ownership transfer 'states' becomes empty, so if we stop the search
170 // and call 'go' again without setting a new position states.get() == NULL.
171 assert(states.get() || setupStates.get());
174 setupStates = std::move(states); // Ownership transfer, states is now empty
176 // We use Position::set() to set root position across threads. But there are
177 // some StateInfo fields (previous, pliesFromNull, capturedPiece) that cannot
178 // be deduced from a fen string, so set() clears them and to not lose the info
179 // we need to backup and later restore setupStates->back(). Note that setupStates
180 // is shared by threads but is accessed in read-only mode.
181 StateInfo tmp = setupStates->back();
183 for (Thread* th : Threads)
185 th->nodes = th->tbHits = 0;
186 th->rootDepth = th->completedDepth = DEPTH_ZERO;
187 th->rootMoves = rootMoves;
188 th->rootPos.set(pos.fen(), pos.is_chess960(), &setupStates->back(), th);
191 setupStates->back() = tmp;
193 main()->start_searching();