X-Git-Url: https://git.sesse.net/?p=stockfish;a=blobdiff_plain;f=src%2Fthread.h;h=b6809f4e37221dcca2329b62980f07a7e42c5238;hp=606f96262dd72ead3f3672a45c1148f840efcb97;hb=63a5fc2366ba215365f8ab246f4a910fcf31c38e;hpb=8d16111ffde1689d48d47ec379ba91613213183c

diff --git a/src/thread.h b/src/thread.h
index 606f9626..b6809f4e 100644
--- 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>
@@ -38,6 +39,23 @@ 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); }
+};
+
+
 /// SplitPoint struct stores information shared by the threads searching in
 /// parallel below the same split point. It is populated at splitting time.
 
@@ -57,7 +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;
@@ -96,7 +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);
@@ -143,12 +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;
 };