{
assert(!do_sleep && !do_exit);
- // Copy split point position and search stack and call search()
- Stack ss[MAX_PLY_PLUS_2];
+ lock_grab(Threads.splitLock);
+
+ assert(is_searching);
SplitPoint* sp = splitPoint;
+
+ lock_release(Threads.splitLock);
+
+ Stack ss[MAX_PLY_PLUS_2];
Position pos(*sp->pos, threadID);
memcpy(ss, sp->ss - 1, 4 * sizeof(Stack));
assert(is_searching);
- // We return from search with lock held
+ is_searching = false;
sp->slavesMask &= ~(1ULL << threadID);
sp->nodes += pos.nodes_searched();
- lock_release(sp->lock);
-
- is_searching = false;
// Wake up master thread so to allow it to return from the idle loop in
// case we are the last slave of the split point.
&& threadID != sp->master
&& !Threads[sp->master].is_searching)
Threads[sp->master].wake_up();
+
+ // After releasing the lock we cannot access anymore any SplitPoint
+ // related data in a reliably way becuase it could have been released
+ // under our feet by the sp master.
+ lock_release(sp->lock);
}
}
+ // In helpful master concept a master can help only a sub-tree of its split
+ // point, and because here is all finished is not possible master is booked.
+ assert(!is_searching);
}
// No active split points means that the thread is available as a slave for any
// other thread otherwise apply the "helpful master" concept if possible.
- if (!sp_count || (splitPoints[sp_count - 1].slavesMask & (1ULL << master)))
- return true;
-
- return false;
+ return !sp_count || (splitPoints[sp_count - 1].slavesMask & (1ULL << master));
}
void ThreadsManager::init() {
- // Initialize sleep condition and lock used by thread manager
cond_init(sleepCond);
- lock_init(threadsLock);
+ lock_init(splitLock);
- // Initialize thread's sleep conditions and split point locks
for (int i = 0; i <= MAX_THREADS; i++)
{
lock_init(threads[i].sleepLock);
thread_join(threads[i].handle); // Wait for thread termination
- // Now we can safely destroy associated locks and wait conditions
lock_destroy(threads[i].sleepLock);
cond_destroy(threads[i].sleepCond);
lock_destroy(threads[i].splitPoints[j].lock);
}
- lock_destroy(threadsLock);
+ lock_destroy(splitLock);
cond_destroy(sleepCond);
}
assert(pos.thread() >= 0 && pos.thread() < activeThreads);
assert(activeThreads > 1);
- int i, master = pos.thread();
+ int master = pos.thread();
Thread& masterThread = threads[master];
- // If we already have too many active split points, don't split
if (masterThread.activeSplitPoints >= MAX_ACTIVE_SPLIT_POINTS)
return bestValue;
// Pick the next available split point from the split point stack
SplitPoint* sp = &masterThread.splitPoints[masterThread.activeSplitPoints];
- // Initialize the split point
sp->parent = masterThread.splitPoint;
sp->master = master;
sp->is_betaCutoff = false;
- sp->slavesMask = (1ULL << master);
+ sp->slavesMask = 1ULL << master;
sp->depth = depth;
sp->threatMove = threatMove;
sp->alpha = alpha;
sp->nodes = 0;
sp->ss = ss;
- // If we are here it means we are not available
assert(masterThread.is_searching);
- int workersCnt = 1; // At least the master is included
+ int slavesCnt = 0;
// Try to allocate available threads and ask them to start searching setting
// is_searching flag. This must be done under lock protection to avoid concurrent
// allocation of the same slave by another master.
- lock_grab(threadsLock);
+ lock_grab(splitLock);
lock_grab(sp->lock); // To protect sp->slaves_mask
- for (i = 0; !Fake && i < activeThreads; i++)
+ for (int i = 0; i < activeThreads && !Fake; i++)
if (threads[i].is_available_to(master))
{
- sp->slavesMask |= (1ULL << i);
+ sp->slavesMask |= 1ULL << i;
threads[i].splitPoint = sp;
-
- // Allocate the slave and make it exit from idle_loop()
- threads[i].is_searching = true;
+ threads[i].is_searching = true; // Slave leaves idle_loop()
if (useSleepingThreads)
threads[i].wake_up();
- if (++workersCnt >= maxThreadsPerSplitPoint)
+ if (++slavesCnt + 1 >= maxThreadsPerSplitPoint) // Master is always included
break;
}
- lock_release(sp->lock);
- lock_release(threadsLock);
-
- // We failed to allocate even one slave, return
- if (!Fake && workersCnt == 1)
- return bestValue;
-
masterThread.splitPoint = sp;
masterThread.activeSplitPoints++;
+ lock_release(sp->lock);
+ lock_release(splitLock);
+
// Everything is set up. The master thread enters the idle loop, from which
// it will instantly launch a search, because its is_searching flag is set.
// We pass the split point as a parameter to the idle loop, which means that
// the thread will return from the idle loop when all slaves have finished
// their work at this split point.
- masterThread.idle_loop(sp);
-
- // In helpful master concept a master can help only a sub-tree of its split
- // point, and because here is all finished is not possible master is booked.
- assert(!masterThread.is_searching);
+ if (slavesCnt || Fake)
+ masterThread.idle_loop(sp);
// We have returned from the idle loop, which means that all threads are
- // finished. Note that changing state and decreasing activeSplitPoints is done
- // under lock protection to avoid a race with Thread::is_available_to().
- lock_grab(threadsLock);
+ // finished. Note that setting is_searching and decreasing activeSplitPoints is
+ // done under lock protection to avoid a race with Thread::is_available_to().
+ lock_grab(splitLock);
lock_grab(sp->lock); // To protect sp->nodes
-
masterThread.is_searching = true;
masterThread.activeSplitPoints--;
masterThread.splitPoint = sp->parent;
pos.set_nodes_searched(pos.nodes_searched() + sp->nodes);
lock_release(sp->lock);
- lock_release(threadsLock);
+ lock_release(splitLock);
return sp->bestValue;
}