&& Threads.size() >= 2
&& depth >= Threads.minimumSplitDepth
&& ( !thisThread->activeSplitPoint
- || !thisThread->activeSplitPoint->allSlavesSearching)
+ || !thisThread->activeSplitPoint->allSlavesSearching
+ || ( Threads.size() > MAX_SLAVES_PER_SPLITPOINT
+ && thisThread->activeSplitPoint->slavesMask.count() == MAX_SLAVES_PER_SPLITPOINT))
&& thisThread->splitPointsSize < MAX_SPLITPOINTS_PER_THREAD)
{
assert(bestValue > -VALUE_INFINITE && bestValue < beta);
// 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;
+ Thread* bestThread = NULL;
+ int bestScore = INT_MAX;
+
+ for (size_t i = 0; i < Threads.size(); ++i)
+ {
+ const size_t size = Threads[i]->splitPointsSize; // Local copy
+ sp = size ? &Threads[i]->splitPoints[size - 1] : nullptr;
+
+ if ( sp
+ && sp->allSlavesSearching
+ && sp->slavesMask.count() < MAX_SLAVES_PER_SPLITPOINT
+ && available_to(Threads[i]))
{
- const int size = Threads[i]->splitPointsSize; // Local copy
- sp = size ? &Threads[i]->splitPoints[size - 1] : nullptr;
+ assert(this != Threads[i]);
+ assert(!(this_sp && this_sp->slavesMask.none()));
+ assert(Threads.size() > 2);
+
+ // Prefer to join to SP with few parents to reduce the probability
+ // that a cut-off occurs above us, and hence we waste our work.
+ int level = -1;
+ for (SplitPoint* spp = Threads[i]->activeSplitPoint; spp; spp = spp->parentSplitPoint)
+ level++;
- if ( sp
- && sp->allSlavesSearching
- && available_to(Threads[i]))
+ int score = level * 256 * 256 + (int)sp->slavesMask.count() * 256 - sp->depth * 1;
+
+ 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 = Threads[i];
+ bestScore = score;
}
}
+ }
+
+ if (bestSp)
+ {
+ sp = bestSp;
+
+ // Recheck the conditions under lock protection
+ Threads.mutex.lock();
+ sp->mutex.lock();
+
+ if ( sp->allSlavesSearching
+ && sp->slavesMask.count() < MAX_SLAVES_PER_SPLITPOINT
+ && available_to(bestThread))
+ {
+ sp->slavesMask.set(idx);
+ activeSplitPoint = sp;
+ searching = true;
+ }
+
+ sp->mutex.unlock();
+ Threads.mutex.unlock();
+ }
}
// Grab the lock to avoid races with Thread::notify_one()
// Loop across all split points and sum accumulated SplitPoint nodes plus
// all the currently active positions nodes.
for (Thread* th : Threads)
- for (int i = 0; i < th->splitPointsSize; ++i)
+ for (size_t i = 0; i < th->splitPointsSize; ++i)
{
SplitPoint& sp = th->splitPoints[i];