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 /// Spinlock class wraps low level atomic operations to provide spin lock functionality
46 std::atomic_flag lock;
49 Spinlock() { std::atomic_flag_clear(&lock); }
50 void acquire() { while (lock.test_and_set(std::memory_order_acquire)) {} }
51 void release() { lock.clear(std::memory_order_release); }
55 /// SplitPoint struct stores information shared by the threads searching in
56 /// parallel below the same split point. It is populated at splitting time.
60 // Const data after split point has been setup
69 // Const pointers to shared data
70 MovePicker* movePicker;
71 SplitPoint* parentSplitPoint;
73 // Shared variable data
75 std::bitset<MAX_THREADS> slavesMask;
76 volatile bool allSlavesSearching;
77 volatile uint64_t nodes;
79 volatile Value bestValue;
80 volatile Move bestMove;
81 volatile int moveCount;
86 /// ThreadBase struct is the base of the hierarchy from where we derive all the
87 /// specialized thread classes.
91 virtual ~ThreadBase() = default;
92 virtual void idle_loop() = 0;
94 void wait_for(volatile const bool& b);
96 std::thread nativeThread;
98 std::condition_variable sleepCondition;
99 volatile bool exit = false;
103 /// Thread struct keeps together all the thread related stuff like locks, state
104 /// and especially split points. We also use per-thread pawn and material hash
105 /// tables so that once we get a pointer to an entry its life time is unlimited
106 /// and we don't have to care about someone changing the entry under our feet.
108 struct Thread : public ThreadBase {
111 virtual void idle_loop();
112 bool cutoff_occurred() const;
113 bool available_to(const Thread* master) const;
115 void split(Position& pos, Search::Stack* ss, Value alpha, Value beta, Value* bestValue, Move* bestMove,
116 Depth depth, int moveCount, MovePicker* movePicker, int nodeType, bool cutNode);
118 SplitPoint splitPoints[MAX_SPLITPOINTS_PER_THREAD];
119 Pawns::Table pawnsTable;
120 Material::Table materialTable;
122 Position* activePosition;
125 SplitPoint* volatile activeSplitPoint;
126 volatile size_t splitPointsSize;
127 volatile bool searching;
131 /// MainThread and TimerThread are derived classes used to characterize the two
132 /// special threads: the main one and the recurring timer.
134 struct MainThread : public Thread {
135 virtual void idle_loop();
136 volatile bool thinking = true; // Avoid a race with start_thinking()
139 struct TimerThread : public ThreadBase {
141 static const int Resolution = 5; // Millisec between two check_time() calls
143 virtual void idle_loop();
149 /// ThreadPool struct handles all the threads related stuff like init, starting,
150 /// parking and, most importantly, launching a slave thread at a split point.
151 /// All the access to shared thread data is done through this class.
153 struct ThreadPool : public std::vector<Thread*> {
155 void init(); // No c'tor and d'tor, threads rely on globals that should be
156 void exit(); // initialized and are valid during the whole thread lifetime.
158 MainThread* main() { return static_cast<MainThread*>(at(0)); }
159 void read_uci_options();
160 Thread* available_slave(const Thread* master) const;
161 void wait_for_think_finished();
162 void start_thinking(const Position&, const Search::LimitsType&, Search::StateStackPtr&);
164 Depth minimumSplitDepth;
166 std::condition_variable sleepCondition;
170 extern ThreadPool Threads;
172 #endif // #ifndef THREAD_H_INCLUDED