Improve comments in SMP code

[stockfish] / src / thread.h

diff --git a/src/thread.h b/src/thread.h
index c9152b229243620bb00b451f85f91e4c7e9b85e6..606f96262dd72ead3f3672a45c1148f840efcb97 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) 2008-2014 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
@@ -20,6 +20,10 @@
 #ifndef THREAD_H_INCLUDED
 #define THREAD_H_INCLUDED
 
+#include <bitset>
+#include <condition_variable>
+#include <mutex>
+#include <thread>
 #include <vector>
 
 #include "material.h"
@@ -28,42 +32,21 @@
 #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); }
-
-private:
-  friend struct ConditionVariable;
-
-  Lock l;
-};
-
-struct ConditionVariable {
-  ConditionVariable() { cond_init(c); }
- ~ConditionVariable() { cond_destroy(c); }
+struct Thread;
 
-  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); }
+const size_t MAX_THREADS = 128;
+const size_t MAX_SPLITPOINTS_PER_THREAD = 8;
+const size_t MAX_SLAVES_PER_SPLITPOINT = 4;
 
-private:
-  WaitCondition c;
-};
-
-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;
@@ -73,9 +56,10 @@ struct SplitPoint {
   MovePicker* movePicker;
   SplitPoint* parentSplitPoint;
 
-  // Shared data
-  Mutex mutex;
-  volatile uint64_t slavesMask;
+  // Shared variable data
+  std::mutex mutex;
+  std::bitset<MAX_THREADS> slavesMask;
+  volatile bool allSlavesSearching;
   volatile uint64_t nodes;
   volatile Value alpha;
   volatile Value bestValue;
@@ -90,16 +74,15 @@ struct SplitPoint {
 
 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;
 };
 
 
@@ -115,19 +98,18 @@ struct Thread : public ThreadBase {
   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,
+  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;
 };
 
@@ -136,16 +118,17 @@ 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()
   virtual void idle_loop();
-  volatile bool thinking;
+  volatile bool thinking = true; // Avoid a race with start_thinking()
 };
 
 struct TimerThread : public ThreadBase {
-  TimerThread() : run(false) {}
+
+  static const int Resolution = 5; // Millisec between two check_time() calls
+
   virtual void idle_loop();
-  bool run;
-  static const int Resolution = 5; // msec between two check_time() calls
+
+  bool run = false;
 };
 
 
@@ -155,20 +138,18 @@ struct TimerThread : public ThreadBase {
 
 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.
+  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&, Search::StateStackPtr&);
 
-  bool sleepWhileIdle;
   Depth minimumSplitDepth;
-  size_t maxThreadsPerSplitPoint;
-  Mutex mutex;
-  ConditionVariable sleepCondition;
+  std::mutex mutex;
+  std::condition_variable sleepCondition;
   TimerThread* timer;
 };