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;
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); }
59 /// SplitPoint struct stores information shared by the threads searching in
60 /// parallel below the same split point. It is populated at splitting time.
64 // Const data after split point has been setup
73 // Const pointers to shared data
74 MovePicker* movePicker;
75 SplitPoint* parentSplitPoint;
77 // Shared variable data
79 std::bitset<MAX_THREADS> slavesMask;
80 volatile bool allSlavesSearching;
81 volatile uint64_t nodes;
83 volatile Value bestValue;
84 volatile Move bestMove;
85 volatile int moveCount;
90 /// ThreadBase struct is the base of the hierarchy from where we derive all the
91 /// specialized thread classes.
95 virtual ~ThreadBase() = default;
96 virtual void idle_loop() = 0;
98 void wait_for(volatile const bool& b);
100 std::thread nativeThread;
102 std::condition_variable sleepCondition;
103 volatile bool exit = false;
107 /// Thread struct keeps together all the thread related stuff like locks, state
108 /// and especially split points. We also use per-thread pawn and material hash
109 /// tables so that once we get a pointer to an entry its life time is unlimited
110 /// and we don't have to care about someone changing the entry under our feet.
112 struct Thread : public ThreadBase {
115 virtual void idle_loop();
116 bool cutoff_occurred() const;
117 bool can_join(const SplitPoint* sp) const;
119 void split(Position& pos, Search::Stack* ss, Value alpha, Value beta, Value* bestValue, Move* bestMove,
120 Depth depth, int moveCount, MovePicker* movePicker, int nodeType, bool cutNode);
122 SplitPoint splitPoints[MAX_SPLITPOINTS_PER_THREAD];
123 Pawns::Table pawnsTable;
124 Material::Table materialTable;
126 Position* activePosition;
129 SplitPoint* volatile activeSplitPoint;
130 volatile size_t splitPointsSize;
131 volatile bool searching;
135 /// MainThread and TimerThread are derived classes used to characterize the two
136 /// special threads: the main one and the recurring timer.
138 struct MainThread : public Thread {
139 virtual void idle_loop();
140 volatile bool thinking = true; // Avoid a race with start_thinking()
143 struct TimerThread : public ThreadBase {
145 static const int Resolution = 5; // Millisec between two check_time() calls
147 virtual void idle_loop();
153 /// ThreadPool struct handles all the threads related stuff like init, starting,
154 /// parking and, most importantly, launching a slave thread at a split point.
155 /// All the access to shared thread data is done through this class.
157 struct ThreadPool : public std::vector<Thread*> {
159 void init(); // No c'tor and d'tor, threads rely on globals that should be
160 void exit(); // initialized and are valid during the whole thread lifetime.
162 MainThread* main() { return static_cast<MainThread*>(at(0)); }
163 void read_uci_options();
164 Thread* available_slave(const SplitPoint* sp) const;
165 void wait_for_think_finished();
166 void start_thinking(const Position&, const Search::LimitsType&, Search::StateStackPtr&);
168 Depth minimumSplitDepth;
170 std::condition_variable sleepCondition;
174 extern ThreadPool Threads;
176 #endif // #ifndef THREAD_H_INCLUDED