- // split() does the actual work of distributing the work at a node between
- // several available threads. If it does not succeed in splitting the
- // node (because no idle threads are available, or because we have no unused
- // split point objects), the function immediately returns. If splitting is
- // possible, a SplitPoint object is initialized with all the data that must be
- // copied to the helper threads and we tell our helper threads that they have
- // been assigned work. This will cause them to instantly leave their idle loops and
- // call search().When all threads have returned from search() then split() returns.
-
- template <bool Fake>
- void ThreadsManager::split(const Position& p, SearchStack* ss, int ply, Value* alpha,
- const Value beta, Value* bestValue, Depth depth, Move threatMove,
- bool mateThreat, int moveCount, MovePicker* mp, bool pvNode) {
- assert(p.is_ok());
- assert(ply > 0 && ply < PLY_MAX);
- assert(*bestValue >= -VALUE_INFINITE);
- assert(*bestValue <= *alpha);
- assert(*alpha < beta);
- assert(beta <= VALUE_INFINITE);
- assert(depth > DEPTH_ZERO);
- assert(p.thread() >= 0 && p.thread() < ActiveThreads);
- assert(ActiveThreads > 1);
-
- int i, master = p.thread();
- Thread& masterThread = threads[master];
-
- lock_grab(&MPLock);
-
- // If no other thread is available to help us, or if we have too many
- // active split points, don't split.
- if ( !available_thread_exists(master)
- || masterThread.activeSplitPoints >= MAX_ACTIVE_SPLIT_POINTS)
- {
- lock_release(&MPLock);
- return;
- }
-
- // Pick the next available split point object from the split point stack
- SplitPoint& splitPoint = masterThread.splitPoints[masterThread.activeSplitPoints++];
-
- // Initialize the split point object
- splitPoint.parent = masterThread.splitPoint;
- splitPoint.stopRequest = false;
- splitPoint.ply = ply;
- splitPoint.depth = depth;
- splitPoint.threatMove = threatMove;
- splitPoint.mateThreat = mateThreat;
- splitPoint.alpha = *alpha;
- splitPoint.beta = beta;
- splitPoint.pvNode = pvNode;
- splitPoint.bestValue = *bestValue;
- splitPoint.mp = mp;
- splitPoint.moveCount = moveCount;
- splitPoint.pos = &p;
- splitPoint.parentSstack = ss;
- for (i = 0; i < ActiveThreads; i++)
- splitPoint.slaves[i] = 0;
-
- masterThread.splitPoint = &splitPoint;
-
- // If we are here it means we are not available
- assert(masterThread.state != THREAD_AVAILABLE);
-
- int workersCnt = 1; // At least the master is included
-
- // Allocate available threads setting state to THREAD_BOOKED
- for (i = 0; !Fake && i < ActiveThreads && workersCnt < MaxThreadsPerSplitPoint; i++)
- if (thread_is_available(i, master))
- {
- threads[i].state = THREAD_BOOKED;
- threads[i].splitPoint = &splitPoint;
- splitPoint.slaves[i] = 1;
- workersCnt++;
- }