/*
Stockfish, a UCI chess playing engine derived from Glaurung 2.1
Copyright (C) 2004-2008 Tord Romstad (Glaurung author)
- Copyright (C) 2008-2013 Marco Costalba, Joona Kiiski, Tord Romstad
+ Copyright (C) 2008-2015 Marco Costalba, Joona Kiiski, Tord Romstad
Stockfish is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
#ifndef THREAD_H_INCLUDED
#define THREAD_H_INCLUDED
+#include <atomic>
+#include <bitset>
+#include <condition_variable>
+#include <mutex>
+#include <thread>
#include <vector>
#include "material.h"
#include "position.h"
#include "search.h"
-const int MAX_THREADS = 64; // Because SplitPoint::slavesMask is a uint64_t
-const int MAX_SPLITPOINTS_PER_THREAD = 8;
-
-struct Mutex {
- Mutex() { lock_init(l); }
- ~Mutex() { lock_destroy(l); }
-
- void lock() { lock_grab(l); }
- void unlock() { lock_release(l); }
+struct Thread;
-private:
- friend struct ConditionVariable;
+const size_t MAX_THREADS = 128;
+const size_t MAX_SPLITPOINTS_PER_THREAD = 8;
+const size_t MAX_SLAVES_PER_SPLITPOINT = 4;
- Lock l;
-};
+/// Spinlock class wraps low level atomic operations to provide spin lock functionality
-struct ConditionVariable {
- ConditionVariable() { cond_init(c); }
- ~ConditionVariable() { cond_destroy(c); }
+class Spinlock {
- void wait(Mutex& m) { cond_wait(c, m.l); }
- void wait_for(Mutex& m, int ms) { timed_wait(c, m.l, ms); }
- void notify_one() { cond_signal(c); }
+ std::atomic_flag lock;
-private:
- WaitCondition c;
+public:
+ Spinlock() { std::atomic_flag_clear(&lock); }
+ void acquire() { while (lock.test_and_set(std::memory_order_acquire)) {} }
+ void release() { lock.clear(std::memory_order_release); }
};
-struct Thread;
+
+/// SplitPoint struct stores information shared by the threads searching in
+/// parallel below the same split point. It is populated at splitting time.
struct SplitPoint {
// Const data after split point has been setup
const Position* pos;
- const Search::Stack* ss;
- Thread* masterThread;
+ Search::Stack* ss;
+ Thread* master;
Depth depth;
Value beta;
int nodeType;
- Move threatMove;
bool cutNode;
// Const pointers to shared data
MovePicker* movePicker;
SplitPoint* parentSplitPoint;
- // Shared data
- Mutex mutex;
- volatile uint64_t slavesMask;
- volatile int64_t nodes;
+ // Shared variable data
+ Spinlock spinlock;
+ std::bitset<MAX_THREADS> slavesMask;
+ volatile bool allSlavesSearching;
+ volatile uint64_t nodes;
volatile Value alpha;
volatile Value bestValue;
volatile Move bestMove;
struct ThreadBase {
- ThreadBase() : exit(false) {}
- virtual ~ThreadBase() {}
+ virtual ~ThreadBase() = default;
virtual void idle_loop() = 0;
void notify_one();
void wait_for(volatile const bool& b);
- Mutex mutex;
- ConditionVariable sleepCondition;
- NativeHandle handle;
- volatile bool exit;
+ std::thread nativeThread;
+ std::mutex mutex;
+ std::condition_variable sleepCondition;
+ volatile bool exit = false;
};
bool cutoff_occurred() const;
bool available_to(const Thread* master) const;
- template <bool Fake>
- void split(Position& pos, const Search::Stack* ss, Value alpha, Value beta, Value* bestValue, Move* bestMove,
- Depth depth, Move threatMove, int moveCount, MovePicker* movePicker, int nodeType, bool cutNode);
+ void split(Position& pos, Search::Stack* ss, Value alpha, Value beta, Value* bestValue, Move* bestMove,
+ Depth depth, int moveCount, MovePicker* movePicker, int nodeType, bool cutNode);
SplitPoint splitPoints[MAX_SPLITPOINTS_PER_THREAD];
+ Pawns::Table pawnsTable;
Material::Table materialTable;
Endgames endgames;
- Pawns::Table pawnsTable;
Position* activePosition;
size_t idx;
int maxPly;
SplitPoint* volatile activeSplitPoint;
- volatile int splitPointsSize;
+ volatile size_t splitPointsSize;
volatile bool searching;
};
/// special threads: the main one and the recurring timer.
struct MainThread : public Thread {
- MainThread() : thinking(true) {} // Avoid a race with start_thinking()
virtual void idle_loop();
- volatile bool thinking;
+ volatile bool thinking = true; // Avoid a race with start_thinking()
};
struct TimerThread : public ThreadBase {
- TimerThread() : msec(0) {}
+
+ static const int Resolution = 5; // Millisec between two check_time() calls
+
virtual void idle_loop();
- int msec;
+
+ bool run = false;
};
/// ThreadPool struct handles all the threads related stuff like init, starting,
-/// parking and, the most important, launching a slave thread at a split point.
+/// parking and, most importantly, launching a slave thread at a split point.
/// All the access to shared thread data is done through this class.
struct ThreadPool : public std::vector<Thread*> {
- void init(); // No c'tor and d'tor, threads rely on globals that should
- void exit(); // be initialized and valid during the whole thread lifetime.
+ void init(); // No c'tor and d'tor, threads rely on globals that should be
+ void exit(); // initialized and are valid during the whole thread lifetime.
- MainThread* main() { return static_cast<MainThread*>((*this)[0]); }
+ MainThread* main() { return static_cast<MainThread*>(at(0)); }
void read_uci_options();
Thread* available_slave(const Thread* master) const;
void wait_for_think_finished();
- void start_thinking(const Position&, const Search::LimitsType&,
- const std::vector<Move>&, Search::StateStackPtr&);
+ void start_thinking(const Position&, const Search::LimitsType&, Search::StateStackPtr&);
- bool sleepWhileIdle;
Depth minimumSplitDepth;
- size_t maxThreadsPerSplitPoint;
- Mutex mutex;
- ConditionVariable sleepCondition;
+ Spinlock spinlock;
+ std::condition_variable sleepCondition;
TimerThread* timer;
};
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