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
6 Stockfish is free software: you can redistribute it and/or modify
7 it under the terms of the GNU General Public License as published by
8 the Free Software Foundation, either version 3 of the License, or
9 (at your option) any later version.
11 Stockfish is distributed in the hope that it will be useful,
12 but WITHOUT ANY WARRANTY; without even the implied warranty of
13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
14 GNU General Public License for more details.
16 You should have received a copy of the GNU General Public License
17 along with this program. If not, see <http://www.gnu.org/licenses/>.
20 #ifndef THREAD_H_INCLUDED
21 #define THREAD_H_INCLUDED
25 #include <condition_variable>
38 const size_t MAX_THREADS = 128;
39 const size_t MAX_SPLITPOINTS_PER_THREAD = 8;
40 const size_t MAX_SLAVES_PER_SPLITPOINT = 4;
42 #if !defined(NO_SPINLOCK)
43 /// Spinlock class wraps low level atomic operations to provide a spin lock
50 Spinlock() { lock = 1; } // Init here to workaround a bug with MSVC 2013
52 while (lock.fetch_sub(1, std::memory_order_acquire) != 1)
53 while (lock.load(std::memory_order_relaxed) <= 0) {}
55 void release() { lock.store(1, std::memory_order_release); }
65 void acquire() { mutex.lock(); }
66 void release() { mutex.unlock(); }
71 /// SplitPoint struct stores information shared by the threads searching in
72 /// parallel below the same split point. It is populated at splitting time.
76 // Const data after split point has been setup
85 // Const pointers to shared data
86 MovePicker* movePicker;
87 SplitPoint* parentSplitPoint;
89 // Shared variable data
91 std::bitset<MAX_THREADS> slavesMask;
92 volatile bool allSlavesSearching;
93 volatile uint64_t nodes;
95 volatile Value bestValue;
96 volatile Move bestMove;
97 volatile int moveCount;
102 /// ThreadBase struct is the base of the hierarchy from where we derive all the
103 /// specialized thread classes.
107 virtual ~ThreadBase() = default;
108 virtual void idle_loop() = 0;
110 void wait_for(volatile const bool& b);
112 std::thread nativeThread;
114 std::condition_variable sleepCondition;
115 volatile bool exit = false;
119 /// Thread struct keeps together all the thread related stuff like locks, state
120 /// and especially split points. We also use per-thread pawn and material hash
121 /// tables so that once we get a pointer to an entry its life time is unlimited
122 /// and we don't have to care about someone changing the entry under our feet.
124 struct Thread : public ThreadBase {
127 virtual void idle_loop();
128 bool cutoff_occurred() const;
129 bool can_join(const SplitPoint* sp) const;
131 void split(Position& pos, Search::Stack* ss, Value alpha, Value beta, Value* bestValue, Move* bestMove,
132 Depth depth, int moveCount, MovePicker* movePicker, int nodeType, bool cutNode);
134 SplitPoint splitPoints[MAX_SPLITPOINTS_PER_THREAD];
135 Pawns::Table pawnsTable;
136 Material::Table materialTable;
138 Position* activePosition;
141 SplitPoint* volatile activeSplitPoint;
142 volatile size_t splitPointsSize;
143 volatile bool searching;
147 /// MainThread and TimerThread are derived classes used to characterize the two
148 /// special threads: the main one and the recurring timer.
150 struct MainThread : public Thread {
151 virtual void idle_loop();
152 volatile bool thinking = true; // Avoid a race with start_thinking()
155 struct TimerThread : public ThreadBase {
157 static const int Resolution = 5; // Millisec between two check_time() calls
159 virtual void idle_loop();
165 /// ThreadPool struct handles all the threads related stuff like init, starting,
166 /// parking and, most importantly, launching a slave thread at a split point.
167 /// All the access to shared thread data is done through this class.
169 struct ThreadPool : public std::vector<Thread*> {
171 void init(); // No c'tor and d'tor, threads rely on globals that should be
172 void exit(); // initialized and are valid during the whole thread lifetime.
174 MainThread* main() { return static_cast<MainThread*>(at(0)); }
175 void read_uci_options();
176 Thread* available_slave(const SplitPoint* sp) const;
177 void wait_for_think_finished();
178 void start_thinking(const Position&, const Search::LimitsType&, Search::StateStackPtr&);
180 Depth minimumSplitDepth;
182 std::condition_variable sleepCondition;
186 extern ThreadPool Threads;
188 #endif // #ifndef THREAD_H_INCLUDED