Rename available_to()

[stockfish] / src / thread.h

diff --git a/src/thread.h b/src/thread.h
index ba9197ce4aabe43ab316b02f802f8efcdfc1a89a..b6809f4e37221dcca2329b62980f07a7e42c5238 100644 (file)
--- a/src/thread.h
+++ b/src/thread.h
@@ -20,6 +20,7 @@
 #ifndef THREAD_H_INCLUDED
 #define THREAD_H_INCLUDED
 
+#include <atomic>
 #include <bitset>
 #include <condition_variable>
 #include <mutex>
@@ -34,10 +35,26 @@
 
 struct Thread;
 
-const int MAX_THREADS = 128;
-const int MAX_SPLITPOINTS_PER_THREAD = 8;
+const size_t MAX_THREADS = 128;
+const size_t MAX_SPLITPOINTS_PER_THREAD = 8;
+const size_t MAX_SLAVES_PER_SPLITPOINT = 4;
+
+
+/// Spinlock class wraps low level atomic operations to provide a spin lock
+
+class Spinlock {
+
+  std::atomic_int lock;
+
+public:
+  Spinlock() { lock = 1; } // Init here to workaround a bug with MSVC 2013
+  void acquire() {
+    while (lock.fetch_sub(1, std::memory_order_acquire) != 1)
+        while (lock.load(std::memory_order_relaxed) <= 0) {}
+  }
+  void release() { lock.store(1, 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.
@@ -47,7 +64,7 @@ struct SplitPoint {
   // Const data after split point has been setup
   const Position* pos;
   Search::Stack* ss;
-  Thread* masterThread;
+  Thread* master;
   Depth depth;
   Value beta;
   int nodeType;
@@ -58,7 +75,7 @@ struct SplitPoint {
   SplitPoint* parentSplitPoint;
 
   // Shared variable data
-  std::mutex mutex;
+  Spinlock spinlock;
   std::bitset<MAX_THREADS> slavesMask;
   volatile bool allSlavesSearching;
   volatile uint64_t nodes;
@@ -75,8 +92,7 @@ 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);
@@ -84,7 +100,7 @@ struct ThreadBase {
   std::thread nativeThread;
   std::mutex mutex;
   std::condition_variable sleepCondition;
-  volatile bool exit;
+  volatile bool exit = false;
 };
 
 
@@ -98,7 +114,7 @@ struct Thread : public ThreadBase {
   Thread();
   virtual void idle_loop();
   bool cutoff_occurred() const;
-  bool available_to(const Thread* master) const;
+  bool can_join(const SplitPoint* sp) 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);
@@ -111,7 +127,7 @@ struct Thread : public ThreadBase {
   size_t idx;
   int maxPly;
   SplitPoint* volatile activeSplitPoint;
-  volatile int splitPointsSize;
+  volatile size_t splitPointsSize;
   volatile bool searching;
 };
 
@@ -120,19 +136,17 @@ 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 {
 
   static const int Resolution = 5; // Millisec between two check_time() calls
 
-  TimerThread() : run(false) {}
   virtual void idle_loop();
 
-  bool run;
+  bool run = false;
 };
 
 
@@ -147,12 +161,12 @@ 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;
+  Thread* available_slave(const SplitPoint* sp) const;
   void wait_for_think_finished();
   void start_thinking(const Position&, const Search::LimitsType&, Search::StateStackPtr&);
 
   Depth minimumSplitDepth;
-  std::mutex mutex;
+  Spinlock spinlock;
   std::condition_variable sleepCondition;
   TimerThread* timer;
 };