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
28 #include "syzygy/tbprobe.h"
30 ThreadPool Threads; // Global object
32 /// Thread constructor launches the thread and then waits until it goes to sleep
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::start_searching() wakes up the thread that will start the search
73 void Thread::start_searching() {
75 std::unique_lock<Mutex> lk(mutex);
77 sleepCondition.notify_one();
81 /// Thread::idle_loop() is where the thread is parked when it has no work to do
83 void Thread::idle_loop() {
85 WinProcGroup::bindThisThread(idx);
89 std::unique_lock<Mutex> lk(mutex);
93 while (!searching && !exit)
95 sleepCondition.notify_one(); // Wake up any waiting thread
96 sleepCondition.wait(lk);
107 /// ThreadPool::init() creates and launches requested threads that will go
108 /// immediately to sleep. We cannot use a constructor because Threads is a
109 /// static object and we need a fully initialized engine at this point due to
110 /// allocation of Endgames in the Thread constructor.
112 void ThreadPool::init() {
114 push_back(new MainThread());
119 /// ThreadPool::exit() terminates threads before the program exits. Cannot be
120 /// done in destructor because threads must be terminated before deleting any
121 /// static objects while still in main().
123 void ThreadPool::exit() {
126 delete back(), pop_back();
130 /// ThreadPool::read_uci_options() updates internal threads parameters from the
131 /// corresponding UCI options and creates/destroys threads to match requested
132 /// number. Thread objects are dynamically allocated.
134 void ThreadPool::read_uci_options() {
136 size_t requested = Options["Threads"];
138 assert(requested > 0);
140 while (size() < requested)
141 push_back(new Thread());
143 while (size() > requested)
144 delete back(), pop_back();
148 /// ThreadPool::nodes_searched() returns the number of nodes searched
150 uint64_t ThreadPool::nodes_searched() const {
153 for (Thread* th : *this)
154 nodes += th->nodes.load(std::memory_order_relaxed);
159 /// ThreadPool::tb_hits() returns the number of TB hits
161 uint64_t ThreadPool::tb_hits() const {
164 for (Thread* th : *this)
165 hits += th->tbHits.load(std::memory_order_relaxed);
170 /// ThreadPool::start_thinking() wakes up the main thread sleeping in idle_loop()
171 /// and starts a new search, then returns immediately.
173 void ThreadPool::start_thinking(Position& pos, StateListPtr& states,
174 const Search::LimitsType& limits, bool ponderMode) {
176 main()->wait_for_search_finished();
178 stopOnPonderhit = stop = false;
180 Search::Limits = limits;
181 Search::RootMoves rootMoves;
183 for (const auto& m : MoveList<LEGAL>(pos))
184 if ( limits.searchmoves.empty()
185 || std::count(limits.searchmoves.begin(), limits.searchmoves.end(), m))
186 rootMoves.push_back(Search::RootMove(m));
188 if (!rootMoves.empty())
189 Tablebases::filter_root_moves(pos, rootMoves);
191 // After ownership transfer 'states' becomes empty, so if we stop the search
192 // and call 'go' again without setting a new position states.get() == NULL.
193 assert(states.get() || setupStates.get());
196 setupStates = std::move(states); // Ownership transfer, states is now empty
198 StateInfo tmp = setupStates->back();
200 for (Thread* th : Threads)
204 th->rootDepth = DEPTH_ZERO;
205 th->rootMoves = rootMoves;
206 th->rootPos.set(pos.fen(), pos.is_chess960(), &setupStates->back(), th);
209 setupStates->back() = tmp; // Restore st->previous, cleared by Position::set()
211 main()->start_searching();