Allow a slave to 'late join' another splitpoint

[stockfish] / src / thread.cpp

diff --git a/src/thread.cpp b/src/thread.cpp
index cdc94ee07688f7dd829446bb519f640c81b8e5cd..f5aab2b13366e3a3850dfb2979080d489c33b648 100644 (file)
--- a/src/thread.cpp
+++ b/src/thread.cpp
@@ -112,9 +112,9 @@ bool Thread::cutoff_occurred() const {
 // which are busy searching the split point at the top of slave's split point
 // stack (the "helpful master concept" in YBWC terminology).
 
-bool Thread::available_to(const Thread* master) const {
+bool Thread::available_to(const Thread* master, bool latejoin) const {
 
-  if (searching)
+  if (searching && !latejoin)
       return false;
 
   // Make a local copy to be sure it doesn't become zero under our feet while
@@ -123,7 +123,7 @@ bool Thread::available_to(const Thread* master) const {
 
   // No split points means that the thread is available as a slave for any
   // other thread otherwise apply the "helpful master" concept if possible.
-  return !size || (splitPoints[size - 1].slavesMask & (1ULL << master->idx));
+  return !size || splitPoints[size - 1].slavesMask.test(master->idx);
 }
 
 
@@ -239,7 +239,7 @@ void ThreadPool::read_uci_options() {
 Thread* ThreadPool::available_slave(const Thread* master) const {
 
   for (const_iterator it = begin(); it != end(); ++it)
-      if ((*it)->available_to(master))
+      if ((*it)->available_to(master, false))
           return *it;
 
   return NULL;
@@ -271,7 +271,7 @@ void Thread::split(Position& pos, const Stack* ss, Value alpha, Value beta, Valu
 
   sp.masterThread = this;
   sp.parentSplitPoint = activeSplitPoint;
-  sp.slavesMask = 1ULL << idx;
+  sp.slavesMask = 0, sp.slavesMask.set(idx);
   sp.depth = depth;
   sp.bestValue = *bestValue;
   sp.bestMove = *bestMove;
@@ -292,6 +292,7 @@ void Thread::split(Position& pos, const Stack* ss, Value alpha, Value beta, Valu
   Threads.mutex.lock();
   sp.mutex.lock();
 
+  sp.allowLatejoin = true; // Only set this under lock protection
   ++splitPointsSize;
   activeSplitPoint = &sp;
   activePosition = NULL;
@@ -299,7 +300,7 @@ void Thread::split(Position& pos, const Stack* ss, Value alpha, Value beta, Valu
   if (!Fake)
       for (Thread* slave; (slave = Threads.available_slave(this)) != NULL; )
       {
-          sp.slavesMask |= 1ULL << slave->idx;
+          sp.slavesMask.set(slave->idx);
           slave->activeSplitPoint = &sp;
           slave->searching = true; // Slave leaves idle_loop()
           slave->notify_one(); // Could be sleeping