text: /*
    Stockfish, a UCI chess playing engine derived from Glaurung 2.1
    Copyright (C) 2004-2008 Tord Romstad (Glaurung author)
    Copyright (C) 2008-2014 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
    the Free Software Foundation, either version 3 of the License, or
    (at your option) any later version.
  
    Stockfish is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    GNU General Public License for more details.
  
    You should have received a copy of the GNU General Public License
    along with this program.  If not, see <http://www.gnu.org/licenses/>.
  */
  
  #ifndef THREAD_H_INCLUDED
  #define THREAD_H_INCLUDED
  
  #include <bitset>
  #include <vector>
  
  #include "material.h"
  #include "movepick.h"
  #include "pawns.h"
  #include "position.h"
  #include "search.h"
  
  const int MAX_THREADS = 128;
  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); }
  
  private:
    friend struct ConditionVariable;
  
    Lock l;
  };
  
  struct ConditionVariable {
    ConditionVariable() { cond_init(c); }
   ~ConditionVariable() { cond_destroy(c); }
  
    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); }
  
  private:
    WaitCondition c;
  };
  
  struct Thread;
  
  struct SplitPoint {
  
    // Const data after split point has been setup
    const Position* pos;
    const Search::Stack* ss;
    Thread* masterThread;
    Depth depth;
    Value beta;
    int nodeType;
    bool cutNode;
  
    // Const pointers to shared data
    MovePicker* movePicker;
    SplitPoint* parentSplitPoint;
  
    // Shared data
    Mutex mutex;
    std::bitset<MAX_THREADS> slavesMask;
    volatile bool allSlavesSearching;
    volatile uint64_t nodes;
    volatile Value alpha;
    volatile Value bestValue;
    volatile Move bestMove;
    volatile int moveCount;
    volatile bool cutoff;
  };
  
  
  /// ThreadBase struct is the base of the hierarchy from where we derive all the
  /// specialized thread classes.
  
  struct ThreadBase {
  
    ThreadBase() : handle(NativeHandle()), exit(false) {}
    virtual ~ThreadBase() {}
    virtual void idle_loop() = 0;
    void notify_one();
    void wait_for(volatile const bool& b);
  
    Mutex mutex;
    ConditionVariable sleepCondition;
    NativeHandle handle;
    volatile bool exit;
  };
  
  
  /// Thread struct keeps together all the thread related stuff like locks, state
  /// and especially split points. We also use per-thread pawn and material hash
  /// tables so that once we get a pointer to an entry its life time is unlimited
  /// and we don't have to care about someone changing the entry under our feet.
  
  struct Thread : public ThreadBase {
  
    Thread();
    virtual void idle_loop();
    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, int moveCount, MovePicker* movePicker, int nodeType, bool cutNode);
  
    SplitPoint splitPoints[MAX_SPLITPOINTS_PER_THREAD];
    Material::Table materialTable;
    Endgames endgames;
    Pawns::Table pawnsTable;
    Position* activePosition;
    size_t idx;
    int maxPly;
    SplitPoint* volatile activeSplitPoint;
    volatile int splitPointsSize;
    volatile bool searching;
  };
  
  
  /// MainThread and TimerThread are derived classes used to characterize the two
  /// 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;
  };
  
  struct TimerThread : public ThreadBase {
    TimerThread() : run(false) {}
    virtual void idle_loop();
    bool run;
    static const int Resolution = 5; // msec between two check_time() calls
  };
  
  
  /// ThreadPool struct handles all the threads related stuff like init, starting,
  /// 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 are valid during the whole thread lifetime.
  
    MainThread* main() { return static_cast<MainThread*>((*this)[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&, Search::StateStackPtr&);
  
    Depth minimumSplitDepth;
    Mutex mutex;
    ConditionVariable sleepCondition;
    TimerThread* timer;
  };
  
  extern ThreadPool Threads;
  
  #endif // #ifndef THREAD_H_INCLUDED
  