namespace { extern "C" {
// start_routine() is the C function which is called when a new thread
- // is launched. It simply calls idle_loop() of the supplied threadID.
+ // is launched. It simply calls idle_loop() of the supplied thread.
// There are two versions of this function; one for POSIX threads and
// one for Windows threads.
#if defined(_MSC_VER)
- DWORD WINAPI start_routine(LPVOID threadID) {
+ DWORD WINAPI start_routine(LPVOID thread) {
- Threads[*(int*)threadID].idle_loop(NULL);
+ ((Thread*)thread)->idle_loop(NULL);
return 0;
}
#else
- void* start_routine(void* threadID) {
+ void* start_routine(void* thread) {
- Threads[*(int*)threadID].idle_loop(NULL);
+ ((Thread*)thread)->idle_loop(NULL);
return NULL;
}
}
-// cutoff_occurred() checks whether a beta cutoff has occurred in
-// the thread's currently active split point, or in some ancestor of
-// the current split point.
+// cutoff_occurred() checks whether a beta cutoff has occurred in the current
+// active split point, or in some ancestor of the split point.
bool Thread::cutoff_occurred() const {
bool Thread::is_available_to(int master) const {
- if (state != AVAILABLE)
+ if (is_searching)
return false;
// Make a local copy to be sure doesn't become zero under our feet while
void ThreadsManager::init() {
- // Threads will go to sleep as soon as created, only main thread is kept alive
- set_size(1);
- threads[0].state = Thread::SEARCHING;
- threads[0].threadID = 0;
-
// Initialize threads lock, used when allocating slaves during splitting
lock_init(&threadsLock);
lock_init(&(threads[i].splitPoints[j].lock));
}
- // Create and startup all the threads but the main that is already running
+ // Initialize main thread's associated data
+ threads[0].is_searching = true;
+ threads[0].threadID = 0;
+ set_size(1); // This makes all the threads but the main to go to sleep
+
+ // Create and launch all the threads but the main that is already running,
+ // threads will go immediately to sleep.
for (int i = 1; i < MAX_THREADS; i++)
{
- threads[i].state = Thread::AVAILABLE;
+ threads[i].is_searching = false;
threads[i].threadID = i;
#if defined(_MSC_VER)
- threads[i].handle = CreateThread(NULL, 0, start_routine, (LPVOID)&threads[i].threadID, 0, NULL);
+ threads[i].handle = CreateThread(NULL, 0, start_routine, (LPVOID)&threads[i], 0, NULL);
bool ok = (threads[i].handle != NULL);
#else
- bool ok = (pthread_create(&threads[i].handle, NULL, start_routine, (void*)&threads[i].threadID) == 0);
+ bool ok = (pthread_create(&threads[i].handle, NULL, start_routine, (void*)&threads[i]) == 0);
#endif
if (!ok)
{
- std::cout << "Failed to create thread number " << i << std::endl;
+ std::cerr << "Failed to create thread number " << i << std::endl;
::exit(EXIT_FAILURE);
}
}
void ThreadsManager::exit() {
+ // Wake up all the slave threads at once. This is faster than "wake and wait"
+ // for each thread and avoids a rare crash once every 10K games under Linux.
+ for (int i = 1; i < MAX_THREADS; i++)
+ {
+ threads[i].do_terminate = true;
+ threads[i].wake_up();
+ }
+
for (int i = 0; i < MAX_THREADS; i++)
{
- // Wake up all the slave threads and wait for termination
if (i != 0)
{
- threads[i].do_terminate = true;
- threads[i].wake_up();
-
+ // Wait for slave termination
#if defined(_MSC_VER)
WaitForSingleObject(threads[i].handle, 0);
CloseHandle(threads[i].handle);
#else
pthread_join(threads[i].handle, NULL);
- pthread_detach(threads[i].handle);
#endif
}
sp->is_slave[i] = false;
// If we are here it means we are not available
- assert(masterThread.state == Thread::SEARCHING);
+ assert(masterThread.is_searching);
int workersCnt = 1; // At least the master is included
threads[i].splitPoint = sp;
// This makes the slave to exit from idle_loop()
- threads[i].state = Thread::WORKISWAITING;
+ threads[i].is_searching = true;
if (useSleepingThreads)
threads[i].wake_up();
masterThread.splitPoint = sp;
masterThread.activeSplitPoints++;
- masterThread.state = Thread::WORKISWAITING;
- // Everything is set up. The master thread enters the idle loop, from
- // which it will instantly launch a search, because its state is
- // Thread::WORKISWAITING. We send the split point as a second parameter to
- // the idle loop, which means that the main thread will return from the idle
- // loop when all threads have finished their work at this split point.
+ // 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, and
// because here is all finished is not possible master is booked.
- assert(masterThread.state == Thread::AVAILABLE);
+ assert(!masterThread.is_searching);
// 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);
- masterThread.state = Thread::SEARCHING;
+ masterThread.is_searching = true;
masterThread.activeSplitPoints--;
lock_release(&threadsLock);