Reparent to latest

[stockfish] / src / search.cpp

diff --git a/src/search.cpp b/src/search.cpp
index 1d06dbd05748d75073647c544a603171e1b5a89b..b38b7bab92ef84df92eb625b3316b496280a8dcf 100644 (file)
--- a/src/search.cpp
+++ b/src/search.cpp
@@ -1859,6 +1859,44 @@ 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
+          for (int i = 0; i < Threads.size(); i++)
+          {
+              Thread* th = &Threads[i];
+              int spCnt = th->splitPointsCnt;
+              SplitPoint* latest = &th->splitPoints[spCnt ? spCnt - 1 : 0];
+
+              // Find the first split point with still all slaves running
+              // where we are available as a possible slave.
+              if (    this->is_available_to(th)
+                  &&  spCnt > 0
+                  && !latest->cutoff
+                  &&  latest->slavesMask == latest->allSlavesMask
+                  && !single_bit(latest->allSlavesMask))
+              {
+                  lock_grab(latest->lock);
+                  lock_grab(Threads.splitLock);
+
+                  // Retest all under lock protection, we are in the middle
+                  // of a race storm here !
+                  if (    this->is_available_to(th)
+                      &&  spCnt == th->splitPointsCnt
+                      && !latest->cutoff
+                      &&  latest->slavesMask == latest->allSlavesMask
+                      && !single_bit(latest->allSlavesMask))
+                  {
+                      latest->slavesMask |= 1ULL << idx; // allSlavesMask is not updated
+                      curSplitPoint = latest;
+                      is_searching = true;
+                  }
+
+                  lock_release(Threads.splitLock);
+                  lock_release(latest->lock);
+
+                  break; // Exit anyhow, only one try (enough in 99% of cases)
+              }
+          }
       }
   }
 }