Use atomics instead of volatile

[stockfish] / src / thread.h

diff --git a/src/thread.h b/src/thread.h
index f530913cf22017f21fa49a2ca812dc6861b5439c..abb7a22333800f4aa2d648290640f71261e749ab 100644 (file)
--- a/src/thread.h
+++ b/src/thread.h
@@ -20,7 +20,11 @@
 #ifndef THREAD_H_INCLUDED
 #define THREAD_H_INCLUDED
 
+#include <atomic>
 #include <bitset>
+#include <condition_variable>
+#include <mutex>
+#include <thread>
 #include <vector>
 
 #include "material.h"
@@ -28,88 +32,28 @@
 #include "pawns.h"
 #include "position.h"
 #include "search.h"
+#include "thread_win32.h"
 
 struct Thread;
 
 const size_t MAX_THREADS = 128;
-const size_t MAX_SPLITPOINTS_PER_THREAD = 8;
-const size_t MAX_SLAVES_PER_SPLITPOINT = 4;
-
-/// Mutex and ConditionVariable struct are wrappers of the low level locking
-/// machinery and are modeled after the corresponding C++11 classes.
-
-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;
-};
-
-
-/// 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;
-  Search::Stack* ss;
-  Thread* master;
-  Depth depth;
-  Value beta;
-  int nodeType;
-  bool cutNode;
-
-  // Const pointers to shared data
-  MovePicker* movePicker;
-  SplitPoint* parentSplitPoint;
-
-  // Shared variable 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 {
+struct ThreadBase : public std::thread {
 
-  ThreadBase() : handle(NativeHandle()), exit(false) {}
-  virtual ~ThreadBase() {}
+  ThreadBase() { exit = false; }
+  virtual ~ThreadBase() = default;
   virtual void idle_loop() = 0;
   void notify_one();
-  void wait_for(volatile const bool& b);
+  void wait(std::atomic<bool>& b);
+  void wait_while(std::atomic<bool>& b);
 
   Mutex mutex;
   ConditionVariable sleepCondition;
-  NativeHandle handle;
-  volatile bool exit;
+  std::atomic<bool> exit;
 };
 
 
@@ -122,22 +66,21 @@ struct Thread : public ThreadBase {
 
   Thread();
   virtual void idle_loop();
-  bool cutoff_occurred() const;
-  bool available_to(const Thread* master) const;
-
-  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);
+  void search(bool isMainThread = false);
 
-  SplitPoint splitPoints[MAX_SPLITPOINTS_PER_THREAD];
   Pawns::Table pawnsTable;
   Material::Table materialTable;
   Endgames endgames;
-  Position* activePosition;
-  size_t idx;
+  size_t idx, PVIdx;
   int maxPly;
-  SplitPoint* volatile activeSplitPoint;
-  volatile size_t splitPointsSize;
-  volatile bool searching;
+  std::atomic<bool> searching;
+
+  Position rootPos;
+  Search::RootMoveVector rootMoves;
+  Depth rootDepth;
+  Search::Stack stack[MAX_PLY+4];
+  HistoryStats history;
+  MovesStats counterMoves;
 };
 
 
@@ -145,19 +88,20 @@ struct Thread : public ThreadBase {
 /// special threads: the main one and the recurring timer.
 
 struct MainThread : public Thread {
-  MainThread() : thinking(true) {} // Avoid a race with start_thinking()
+  MainThread() { thinking = true; } // Avoid a race with start_thinking()
   virtual void idle_loop();
-  volatile bool thinking;
+  void join();
+  void think();
+  std::atomic<bool> thinking;
 };
 
 struct TimerThread : public ThreadBase {
 
   static const int Resolution = 5; // Millisec between two check_time() calls
 
-  TimerThread() : run(false) {}
   virtual void idle_loop();
 
-  bool run;
+  bool run = false;
 };
 
 
@@ -172,13 +116,8 @@ struct ThreadPool : public std::vector<Thread*> {
 
   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&, Search::StateStackPtr&);
-
-  Depth minimumSplitDepth;
-  Mutex mutex;
-  ConditionVariable sleepCondition;
+  int64_t nodes_searched();
   TimerThread* timer;
 };