Don't reparent if a cutoff is pending

[stockfish] / src / search.cpp

diff --git a/src/search.cpp b/src/search.cpp
index 1d06dbd05748d75073647c544a603171e1b5a89b..dd3030a0dd4f1390b0ef8b1043ff70bfa73afb19 100644 (file)
--- a/src/search.cpp
+++ b/src/search.cpp
@@ -1859,6 +1859,45 @@ void Thread::idle_loop(SplitPoint* sp_master) {
           // our feet by the sp master. Also accessing other Thread objects is
           // unsafe because if we are exiting there is a chance are already freed.
           lock_release(sp->lock);
+
+          // Try to reparent to another split point. Only for slave threads
+          // that are not master of any active split point.
+          if (!splitPointsCnt)
+              for (int i = 0; i < Threads.size(); i++)
+              {
+                  Thread* th = &Threads[i];
+                  SplitPoint* oldest = &th->splitPoints[0];
+
+                  // Find the first split point with still all slaves running
+                  // where we are available as a possible slave.
+                  if (   !is_searching
+                      &&  th->splitPointsCnt
+                      && !oldest->cutoff
+                      &&  oldest->slavesMask == oldest->allSlavesMask
+                      && !single_bit(oldest->allSlavesMask))
+                  {
+                      lock_grab(oldest->lock);
+                      lock_grab(Threads.splitLock);
+
+                      // Retest all under lock protection, we are in the middle
+                      // of a race storm here !
+                      if (   !is_searching
+                          &&  th->splitPointsCnt
+                          && !oldest->cutoff
+                          &&  oldest->slavesMask == oldest->allSlavesMask
+                          && !single_bit(oldest->allSlavesMask))
+                      {
+                          oldest->slavesMask |= 1ULL << idx; // allSlavesMask is not updated
+                          curSplitPoint = oldest;
+                          is_searching = true;
+                      }
+
+                      lock_release(Threads.splitLock);
+                      lock_release(oldest->lock);
+
+                      break; // Exit anyhow, only one try (enough in 99% of cases)
+                  }
+              }
       }
   }
 }