Remove useless condition in late join

[stockfish] / src / search.cpp

diff --git a/src/search.cpp b/src/search.cpp
index ffe361268e6b0a113468e15b4ac18b758e32c977..1062c9203a7bbc0c31c0b134e1d1f882d95f4a76 100644 (file)
--- a/src/search.cpp
+++ b/src/search.cpp
@@ -1042,7 +1042,9 @@ moves_loop: // When in check and at SpNode search starts from here
           &&  Threads.size() >= 2
           &&  depth >= Threads.minimumSplitDepth
           &&  (   !thisThread->activeSplitPoint
-               || !thisThread->activeSplitPoint->allSlavesSearching)
+               || !thisThread->activeSplitPoint->allSlavesSearching
+               || (   int(Threads.size()) > MAX_SLAVES_PER_SPLITPOINT
+                   && thisThread->activeSplitPoint->slavesCount == MAX_SLAVES_PER_SPLITPOINT))
           &&  thisThread->splitPointsSize < MAX_SPLITPOINTS_PER_THREAD)
       {
           assert(bestValue > -VALUE_INFINITE && bestValue < beta);
@@ -1586,34 +1588,57 @@ void Thread::idle_loop() {
 
           // Try to late join to another split point if none of its slaves has
           // already finished.
-          if (Threads.size() > 2)
-              for (size_t i = 0; i < Threads.size(); ++i)
+          SplitPoint* bestSp = NULL;
+          int bestThread = 0;
+          int bestScore = INT_MAX;
+
+          for (size_t i = 0; i < Threads.size(); ++i)
+          {
+              const int size = Threads[i]->splitPointsSize; // Local copy
+              sp = size ? &Threads[i]->splitPoints[size - 1] : NULL;
+
+              if (   sp
+                  && sp->allSlavesSearching
+                  && sp->slavesCount < MAX_SLAVES_PER_SPLITPOINT
+                  && available_to(Threads[i]))
               {
-                  const int size = Threads[i]->splitPointsSize; // Local copy
-                  sp = size ? &Threads[i]->splitPoints[size - 1] : NULL;
+                  // Compute the recursive split points chain size
+                  int level = -1;
+                  for (SplitPoint* spp = Threads[i]->activeSplitPoint; spp; spp = spp->parentSplitPoint)
+                      level++;
+
+                  int score = level * 256 * 256 + sp->slavesCount * 256 - sp->depth * 1;
 
-                  if (   sp
-                      && sp->allSlavesSearching
-                      && available_to(Threads[i]))
+                  if (score < bestScore)
                   {
-                      // Recheck the conditions under lock protection
-                      Threads.mutex.lock();
-                      sp->mutex.lock();
-
-                      if (   sp->allSlavesSearching
-                          && available_to(Threads[i]))
-                      {
-                           sp->slavesMask.set(idx);
-                           activeSplitPoint = sp;
-                           searching = true;
-                      }
-
-                      sp->mutex.unlock();
-                      Threads.mutex.unlock();
-
-                      break; // Just a single attempt
+                      bestSp = sp;
+                      bestThread = i;
+                      bestScore = score;
                   }
               }
+          }
+
+          if (bestSp)
+          {
+              sp = bestSp;
+
+              // Recheck the conditions under lock protection
+              Threads.mutex.lock();
+              sp->mutex.lock();
+
+              if (   sp->allSlavesSearching
+                  && sp->slavesCount < MAX_SLAVES_PER_SPLITPOINT
+                  && available_to(Threads[bestThread]))
+              {
+                  sp->slavesMask.set(idx);
+                  sp->slavesCount++;
+                  activeSplitPoint = sp;
+                  searching = true;
+              }
+
+              sp->mutex.unlock();
+              Threads.mutex.unlock();
+          }
       }
 
       // Grab the lock to avoid races with Thread::notify_one()