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>
35 #include "thread_win32.h"
39 const size_t MAX_THREADS = 128;
40 const size_t MAX_SPLITPOINTS_PER_THREAD = 8;
41 const size_t MAX_SLAVES_PER_SPLITPOINT = 4;
44 std::atomic_int _lock;
47 Spinlock() { _lock = 1; } // Init here to workaround a bug with MSVC 2013
49 while (_lock.fetch_sub(1, std::memory_order_acquire) != 1)
50 for (int cnt = 0; _lock.load(std::memory_order_relaxed) <= 0; ++cnt)
51 if (cnt >= 10000) std::this_thread::yield(); // Be nice to hyperthreading
53 void unlock() { _lock.store(1, std::memory_order_release); }
57 /// SplitPoint struct stores information shared by the threads searching in
58 /// parallel below the same split point. It is populated at splitting time.
62 // Const data after split point has been setup
71 // Const pointers to shared data
72 MovePicker* movePicker;
73 SplitPoint* parentSplitPoint;
75 // Shared variable data
77 std::bitset<MAX_THREADS> slavesMask;
78 volatile bool allSlavesSearching;
79 volatile uint64_t nodes;
81 volatile Value bestValue;
82 volatile Move bestMove;
83 volatile int moveCount;
88 /// ThreadBase struct is the base of the hierarchy from where we derive all the
89 /// specialized thread classes.
93 virtual ~ThreadBase() = default;
94 virtual void idle_loop() = 0;
96 void wait_for(volatile const bool& b);
98 std::thread nativeThread;
100 ConditionVariable sleepCondition;
101 volatile bool exit = false;
105 /// Thread struct keeps together all the thread related stuff like locks, state
106 /// and especially split points. We also use per-thread pawn and material hash
107 /// tables so that once we get a pointer to an entry its life time is unlimited
108 /// and we don't have to care about someone changing the entry under our feet.
110 struct Thread : public ThreadBase {
113 virtual void idle_loop();
114 bool cutoff_occurred() const;
115 bool can_join(const SplitPoint* sp) const;
117 void split(Position& pos, Search::Stack* ss, Value alpha, Value beta, Value* bestValue, Move* bestMove,
118 Depth depth, int moveCount, MovePicker* movePicker, int nodeType, bool cutNode);
120 SplitPoint splitPoints[MAX_SPLITPOINTS_PER_THREAD];
121 Pawns::Table pawnsTable;
122 Material::Table materialTable;
124 Position* activePosition;
127 SplitPoint* volatile activeSplitPoint;
128 volatile size_t splitPointsSize;
129 volatile bool searching;
134 /// MainThread and TimerThread are derived classes used to characterize the two
135 /// special threads: the main one and the recurring timer.
137 struct MainThread : public Thread {
138 virtual void idle_loop();
139 volatile bool thinking = true; // Avoid a race with start_thinking()
142 struct TimerThread : public ThreadBase {
144 static const int Resolution = 5; // Millisec between two check_time() calls
146 virtual void idle_loop();
152 /// ThreadPool struct handles all the threads related stuff like init, starting,
153 /// parking and, most importantly, launching a slave thread at a split point.
154 /// All the access to shared thread data is done through this class.
156 struct ThreadPool : public std::vector<Thread*> {
158 void init(); // No c'tor and d'tor, threads rely on globals that should be
159 void exit(); // initialized and are valid during the whole thread lifetime.
161 MainThread* main() { return static_cast<MainThread*>(at(0)); }
162 void read_uci_options();
163 Thread* available_slave(const SplitPoint* sp) const;
164 void wait_for_think_finished();
165 void start_thinking(const Position&, const Search::LimitsType&, Search::StateStackPtr&);
167 Depth minimumSplitDepth;
168 ConditionVariable sleepCondition;
172 extern ThreadPool Threads;
174 #endif // #ifndef THREAD_H_INCLUDED