Use atomics instead of volatile

[stockfish] / src / thread.h

diff --git a/src/thread.h b/src/thread.h
index f54fcbbe71b62691d62de3f9480980db6aa71558..abb7a22333800f4aa2d648290640f71261e749ab 100644 (file)
--- a/src/thread.h
+++ b/src/thread.h
@@ -1,7 +1,7 @@
 /*
   Stockfish, a UCI chess playing engine derived from Glaurung 2.1
   Copyright (C) 2004-2008 Tord Romstad (Glaurung author)
-  Copyright (C) 2008-2010 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
@@ -17,64 +17,110 @@
   along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */
 
-#if !defined(THREAD_H_INCLUDED)
+#ifndef THREAD_H_INCLUDED
 #define THREAD_H_INCLUDED
 
-#include <cstring>
+#include <atomic>
+#include <bitset>
+#include <condition_variable>
+#include <mutex>
+#include <thread>
+#include <vector>
 
-#include "lock.h"
+#include "material.h"
 #include "movepick.h"
+#include "pawns.h"
 #include "position.h"
 #include "search.h"
+#include "thread_win32.h"
 
-const int MAX_THREADS = 32;
-const int MAX_ACTIVE_SPLIT_POINTS = 8;
-
-struct SplitPoint {
-
-  // Const data after splitPoint has been setup
-  SplitPoint* parent;
-  const Position* pos;
-  Depth depth;
-  bool pvNode;
-  Value beta;
-  int ply;
-  int master;
-  Move threatMove;
-
-  // Const pointers to shared data
-  MovePicker* mp;
-  SearchStack* ss;
-
-  // Shared data
-  Lock lock;
-  volatile int64_t nodes;
-  volatile Value alpha;
-  volatile Value bestValue;
-  volatile int moveCount;
-  volatile bool betaCutoff;
-  volatile int slaves[MAX_THREADS];
-};
+struct Thread;
+
+const size_t MAX_THREADS = 128;
+
+
+/// ThreadBase struct is the base of the hierarchy from where we derive all the
+/// specialized thread classes.
 
-// ThreadState type is used to represent thread's current state
-enum ThreadState
-{
-  THREAD_INITIALIZING,  // thread is initializing itself
-  THREAD_SEARCHING,     // thread is performing work
-  THREAD_AVAILABLE,     // thread is waiting for work
-  THREAD_BOOKED,        // other thread (master) has booked us as a slave
-  THREAD_WORKISWAITING, // master has ordered us to start
-  THREAD_TERMINATED     // we are quitting and thread is terminated
+struct ThreadBase : public std::thread {
+
+  ThreadBase() { exit = false; }
+  virtual ~ThreadBase() = default;
+  virtual void idle_loop() = 0;
+  void notify_one();
+  void wait(std::atomic<bool>& b);
+  void wait_while(std::atomic<bool>& b);
+
+  Mutex mutex;
+  ConditionVariable sleepCondition;
+  std::atomic<bool> exit;
 };
 
-struct Thread {
+
+/// 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();
+  void search(bool isMainThread = false);
+
+  Pawns::Table pawnsTable;
+  Material::Table materialTable;
+  Endgames endgames;
+  size_t idx, PVIdx;
   int maxPly;
-  Lock sleepLock;
-  WaitCondition sleepCond;
-  volatile ThreadState state;
-  SplitPoint* volatile splitPoint;
-  volatile int activeSplitPoints;
-  SplitPoint splitPoints[MAX_ACTIVE_SPLIT_POINTS];
+  std::atomic<bool> searching;
+
+  Position rootPos;
+  Search::RootMoveVector rootMoves;
+  Depth rootDepth;
+  Search::Stack stack[MAX_PLY+4];
+  HistoryStats history;
+  MovesStats counterMoves;
 };
 
-#endif // !defined(THREAD_H_INCLUDED)
+
+/// 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();
+  void join();
+  void think();
+  std::atomic<bool> thinking;
+};
+
+struct TimerThread : public ThreadBase {
+
+  static const int Resolution = 5; // Millisec between two check_time() calls
+
+  virtual void idle_loop();
+
+  bool run = false;
+};
+
+
+/// 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 be
+  void exit(); // initialized and are valid during the whole thread lifetime.
+
+  MainThread* main() { return static_cast<MainThread*>(at(0)); }
+  void read_uci_options();
+  void start_thinking(const Position&, const Search::LimitsType&, Search::StateStackPtr&);
+  int64_t nodes_searched();
+  TimerThread* timer;
+};
+
+extern ThreadPool Threads;
+
+#endif // #ifndef THREAD_H_INCLUDED