Avoid locking/unlocking in a tight loop

[stockfish] / src / search.cpp

diff --git a/src/search.cpp b/src/search.cpp
index 76653ff99bf5fed6963d13b88a47ea202c17f4a2..9a373dec456223cfbac60cd4ce8729adbf3d7a13 100644 (file)
--- a/src/search.cpp
+++ b/src/search.cpp
@@ -44,6 +44,7 @@ namespace Search {
   Color RootColor;
   Time::point SearchTime;
   StateStackPtr SetupStates;
+  MovesVectPtr SetupMoves;
 }
 
 using std::string;
@@ -441,11 +442,17 @@ namespace {
             if (Time::now() - SearchTime > (TimeMgr.available_time() * 62) / 100)
                 stop = true;
 
+            bool recapture =   pos.is_capture(RootMoves[0].pv[0])
+                            && pos.captured_piece_type()
+                            && SetupMoves->size()
+                            && to_sq(SetupMoves->back()) == to_sq(RootMoves[0].pv[0]);
+
             // Stop search early if one move seems to be much better than others
             if (    depth >= 12
                 && !stop
                 &&  PVSize == 1
-                && (   (bestMoveNeverChanged &&  pos.captured_piece_type())
+                && (   (bestMoveNeverChanged && recapture)
+                    || RootMoves.size() == 1
                     || Time::now() - SearchTime > (TimeMgr.available_time() * 40) / 100))
             {
                 Value rBeta = bestValue - 2 * PawnValueMg;
@@ -1615,13 +1622,11 @@ void Thread::idle_loop() {
 
   // Pointer 'this_sp' is not null only if we are called from split(), and not
   // at the thread creation. So it means we are the split point's master.
-  const SplitPoint* this_sp = splitPointsSize ? activeSplitPoint : NULL;
+  SplitPoint* this_sp = splitPointsSize ? activeSplitPoint : NULL;
 
   assert(!this_sp || (this_sp->masterThread == this && searching));
 
-  // If this thread is the master of a split point and all slaves have finished
-  // their work at this split point, return from the idle loop.
-  while (!this_sp || this_sp->slavesMask)
+  while (true)
   {
       // If we are not searching, wait for a condition to be signaled instead of
       // wasting CPU time polling for work.
@@ -1714,6 +1719,17 @@ void Thread::idle_loop() {
           // unsafe because if we are exiting there is a chance are already freed.
           sp->mutex.unlock();
       }
+
+      // If this thread is the master of a split point and all slaves have finished
+      // their work at this split point, return from the idle loop.
+      if (this_sp && !this_sp->slavesMask)
+      {
+          this_sp->mutex.lock();
+          bool finished = !this_sp->slavesMask; // Retest under lock protection
+          this_sp->mutex.unlock();
+          if (finished)
+              return;
+      }
   }
 }