#include "thread.h"
#include "ucioption.h"
-ThreadsManager ThreadsMgr; // Global object definition
+ThreadsManager Threads; // Global object definition
-namespace {
+namespace { extern "C" {
- // init_thread() is the function which is called when a new thread is
- // launched. It simply calls the idle_loop() function with the supplied
- // threadID. There are two versions of this function; one for POSIX
- // threads and one for Windows threads.
+ // start_routine() is the C function which is called when a new thread
+ // is launched. It simply calls idle_loop() with the supplied threadID.
+ // There are two versions of this function; one for POSIX threads and
+ // one for Windows threads.
-#if !defined(_MSC_VER)
+#if defined(_MSC_VER)
- void* init_thread(void* threadID) {
+ DWORD WINAPI start_routine(LPVOID threadID) {
- ThreadsMgr.idle_loop(*(int*)threadID, NULL);
- return NULL;
+ Threads[*(int*)threadID].idle_loop(NULL);
+ return 0;
}
#else
- DWORD WINAPI init_thread(LPVOID threadID) {
+ void* start_routine(void* threadID) {
- ThreadsMgr.idle_loop(*(int*)threadID, NULL);
- return 0;
+ Threads[*(int*)threadID].idle_loop(NULL);
+ return NULL;
}
#endif
+} }
+
+
+// wake_up() wakes up the thread, normally at the beginning of the search or,
+// if "sleeping threads" is used, when there is some work to do.
+
+void Thread::wake_up() {
+
+ lock_grab(&sleepLock);
+ cond_signal(&sleepCond);
+ lock_release(&sleepLock);
+}
+
+
+// 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.
+
+bool Thread::cutoff_occurred() const {
+
+ for (SplitPoint* sp = splitPoint; sp; sp = sp->parent)
+ if (sp->is_betaCutoff)
+ return true;
+ return false;
+}
+
+
+// is_available_to() checks whether the thread is available to help the thread with
+// threadID "master" at a split point. An obvious requirement is that thread must be
+// idle. With more than two threads, this is not by itself sufficient: If the thread
+// is the master of some active split point, it is only available as a slave to the
+// threads 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::is_available_to(int master) const {
+
+ if (state != AVAILABLE)
+ return false;
+
+ // Make a local copy to be sure doesn't become zero under our feet while
+ // testing next condition and so leading to an out of bound access.
+ int localActiveSplitPoints = activeSplitPoints;
+
+ // 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 ( !localActiveSplitPoints
+ || splitPoints[localActiveSplitPoints - 1].is_slave[master])
+ return true;
+
+ return false;
}
maxThreadsPerSplitPoint = Options["Maximum Number of Threads per Split Point"].value<int>();
minimumSplitDepth = Options["Minimum Split Depth"].value<int>() * ONE_PLY;
useSleepingThreads = Options["Use Sleeping Threads"].value<bool>();
- activeThreads = Options["Threads"].value<int>();
+
+ set_size(Options["Threads"].value<int>());
}
-// init_threads() is called during startup. Initializes locks and condition
-// variables and launches all threads sending them immediately to sleep.
+// set_size() changes the number of active threads and raises do_sleep flag for
+// all the unused threads that will go immediately to sleep.
-void ThreadsManager::init_threads() {
+void ThreadsManager::set_size(int cnt) {
- int arg[MAX_THREADS];
+ assert(cnt > 0 && cnt <= MAX_THREADS);
- // This flag is needed to properly end the threads when program exits
- allThreadsShouldExit = false;
+ activeThreads = cnt;
+
+ for (int i = 0; i < MAX_THREADS; i++)
+ threads[i].do_sleep = !(i < activeThreads);
+}
+
+
+// init() is called during startup. Initializes locks and condition variables
+// and launches all threads sending them immediately to sleep.
+
+void ThreadsManager::init() {
// Threads will sent to sleep as soon as created, only main thread is kept alive
- activeThreads = 1;
- threads[0].state = THREAD_SEARCHING;
+ set_size(1);
+ threads[0].state = Thread::SEARCHING;
+ threads[0].threadID = 0;
// Allocate pawn and material hash tables for main thread
init_hash_tables();
- lock_init(&mpLock);
+ // Initialize threads lock, used when allocating slaves during splitting
+ lock_init(&threadsLock);
- // Initialize thread and split point locks
+ // Initialize sleep and split point locks
for (int i = 0; i < MAX_THREADS; i++)
{
lock_init(&threads[i].sleepLock);
// Create and startup all the threads but the main that is already running
for (int i = 1; i < MAX_THREADS; i++)
{
- threads[i].state = THREAD_INITIALIZING;
- arg[i] = i;
+ threads[i].state = Thread::INITIALIZING;
+ threads[i].threadID = i;
-#if !defined(_MSC_VER)
- pthread_t pthread[1];
- bool ok = (pthread_create(pthread, NULL, init_thread, (void*)(&arg[i])) == 0);
- pthread_detach(pthread[0]);
+#if defined(_MSC_VER)
+ bool ok = (CreateThread(NULL, 0, start_routine, (LPVOID)&threads[i].threadID , 0, NULL) != NULL);
#else
- bool ok = (CreateThread(NULL, 0, init_thread, (LPVOID)(&arg[i]), 0, NULL) != NULL);
+ pthread_t pthreadID;
+ bool ok = (pthread_create(&pthreadID, NULL, start_routine, (void*)&threads[i].threadID) == 0);
+ pthread_detach(pthreadID);
#endif
if (!ok)
{
std::cout << "Failed to create thread number " << i << std::endl;
- exit(EXIT_FAILURE);
+ ::exit(EXIT_FAILURE);
}
// Wait until the thread has finished launching and is gone to sleep
- while (threads[i].state == THREAD_INITIALIZING) {}
+ while (threads[i].state == Thread::INITIALIZING) {}
}
}
-// exit_threads() is called when the program exits. It makes all the
-// helper threads exit cleanly.
+// exit() is called to cleanly terminate the threads when the program finishes
-void ThreadsManager::exit_threads() {
-
- // Force the woken up threads to exit idle_loop() and hence terminate
- allThreadsShouldExit = true;
+void ThreadsManager::exit() {
for (int i = 0; i < MAX_THREADS; i++)
{
- // Wake up all the threads and waits for termination
+ // Wake up all the slave threads and wait for termination
if (i != 0)
{
+ threads[i].do_terminate = true;
threads[i].wake_up();
- while (threads[i].state != THREAD_TERMINATED) {}
+ while (threads[i].state != Thread::TERMINATED) {}
}
- // Now we can safely destroy the locks and wait conditions
+ // Now we can safely destroy locks and wait conditions
lock_destroy(&threads[i].sleepLock);
cond_destroy(&threads[i].sleepCond);
lock_destroy(&(threads[i].splitPoints[j].lock));
}
- lock_destroy(&mpLock);
+ lock_destroy(&threadsLock);
}
}
-// cutoff_at_splitpoint() checks whether a beta cutoff has occurred in
-// the thread's currently active split point, or in some ancestor of
-// the current split point.
-
-bool ThreadsManager::cutoff_at_splitpoint(int threadID) const {
-
- assert(threadID >= 0 && threadID < activeThreads);
-
- SplitPoint* sp = threads[threadID].splitPoint;
-
- for ( ; sp && !sp->betaCutoff; sp = sp->parent) {}
- return sp != NULL;
-}
-
-
-// thread_is_available() checks whether the thread with threadID "slave" is
-// available to help the thread with threadID "master" at a split point. An
-// obvious requirement is that "slave" must be idle. With more than two
-// threads, this is not by itself sufficient: If "slave" is the master of
-// some active split point, it is only available as a slave to the other
-// threads which are busy searching the split point at the top of "slave"'s
-// split point stack (the "helpful master concept" in YBWC terminology).
-
-bool ThreadsManager::thread_is_available(int slave, int master) const {
-
- assert(slave >= 0 && slave < activeThreads);
- assert(master >= 0 && master < activeThreads);
- assert(activeThreads > 1);
-
- if (threads[slave].state != THREAD_AVAILABLE || slave == master)
- return false;
-
- // Make a local copy to be sure doesn't change under our feet
- int localActiveSplitPoints = threads[slave].activeSplitPoints;
-
- // No active split points means that the thread is available as
- // a slave for any other thread.
- if (localActiveSplitPoints == 0 || activeThreads == 2)
- return true;
-
- // Apply the "helpful master" concept if possible. Use localActiveSplitPoints
- // that is known to be > 0, instead of threads[slave].activeSplitPoints that
- // could have been set to 0 by another thread leading to an out of bound access.
- if (threads[slave].splitPoints[localActiveSplitPoints - 1].slaves[master])
- return true;
-
- return false;
-}
-
-
-// available_thread_exists() tries to find an idle thread which is available as
+// available_slave_exists() tries to find an idle thread which is available as
// a slave for the thread with threadID "master".
-bool ThreadsManager::available_thread_exists(int master) const {
+bool ThreadsManager::available_slave_exists(int master) const {
assert(master >= 0 && master < activeThreads);
- assert(activeThreads > 1);
for (int i = 0; i < activeThreads; i++)
- if (thread_is_available(i, master))
+ if (i != master && threads[i].is_available_to(master))
return true;
return false;
// call search().When all threads have returned from search() then split() returns.
template <bool Fake>
-void ThreadsManager::split(Position& pos, SearchStack* ss, Value* alpha, const Value beta,
- Value* bestValue, Depth depth, Move threatMove,
- int moveCount, MovePicker* mp, bool pvNode) {
+Value ThreadsManager::split(Position& pos, SearchStack* ss, Value alpha, Value beta,
+ Value bestValue, Depth depth, Move threatMove,
+ int moveCount, MovePicker* mp, int nodeType) {
assert(pos.is_ok());
- assert(*bestValue >= -VALUE_INFINITE);
- assert(*bestValue <= *alpha);
- assert(*alpha < beta);
+ assert(bestValue >= -VALUE_INFINITE);
+ assert(bestValue <= alpha);
+ assert(alpha < beta);
assert(beta <= VALUE_INFINITE);
assert(depth > DEPTH_ZERO);
assert(pos.thread() >= 0 && pos.thread() < activeThreads);
int i, master = pos.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;
- }
+ // 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 object from the split point stack
- SplitPoint& splitPoint = masterThread.splitPoints[masterThread.activeSplitPoints++];
+ SplitPoint* sp = masterThread.splitPoints + masterThread.activeSplitPoints;
// Initialize the split point object
- splitPoint.parent = masterThread.splitPoint;
- splitPoint.master = master;
- splitPoint.betaCutoff = false;
- splitPoint.depth = depth;
- splitPoint.threatMove = threatMove;
- splitPoint.alpha = *alpha;
- splitPoint.beta = beta;
- splitPoint.pvNode = pvNode;
- splitPoint.bestValue = *bestValue;
- splitPoint.mp = mp;
- splitPoint.moveCount = moveCount;
- splitPoint.pos = &pos;
- splitPoint.nodes = 0;
- splitPoint.ss = ss;
+ sp->parent = masterThread.splitPoint;
+ sp->master = master;
+ sp->is_betaCutoff = false;
+ sp->depth = depth;
+ sp->threatMove = threatMove;
+ sp->alpha = alpha;
+ sp->beta = beta;
+ sp->nodeType = nodeType;
+ sp->bestValue = bestValue;
+ sp->mp = mp;
+ sp->moveCount = moveCount;
+ sp->pos = &pos;
+ sp->nodes = 0;
+ sp->ss = ss;
for (i = 0; i < activeThreads; i++)
- splitPoint.slaves[i] = 0;
-
- masterThread.splitPoint = &splitPoint;
+ sp->is_slave[i] = false;
// If we are here it means we are not available
- assert(masterThread.state != THREAD_AVAILABLE);
+ assert(masterThread.state == Thread::SEARCHING);
int workersCnt = 1; // At least the master is included
- // Allocate available threads setting state to THREAD_BOOKED
+ // Try to allocate available threads and ask them to start searching setting
+ // the state to Thread::WORKISWAITING, this must be done under lock protection
+ // to avoid concurrent allocation of the same slave by another master.
+ lock_grab(&threadsLock);
+
for (i = 0; !Fake && i < activeThreads && workersCnt < maxThreadsPerSplitPoint; i++)
- if (thread_is_available(i, master))
+ if (i != master && threads[i].is_available_to(master))
{
- threads[i].state = THREAD_BOOKED;
- threads[i].splitPoint = &splitPoint;
- splitPoint.slaves[i] = 1;
workersCnt++;
- }
+ sp->is_slave[i] = true;
+ threads[i].splitPoint = sp;
- assert(Fake || workersCnt > 1);
+ // This makes the slave to exit from idle_loop()
+ threads[i].state = Thread::WORKISWAITING;
- // We can release the lock because slave threads are already booked and master is not available
- lock_release(&mpLock);
+ if (useSleepingThreads)
+ threads[i].wake_up();
+ }
- // Tell the threads that they have work to do. This will make them leave
- // their idle loop.
- for (i = 0; i < activeThreads; i++)
- if (i == master || splitPoint.slaves[i])
- {
- assert(i == master || threads[i].state == THREAD_BOOKED);
+ lock_release(&threadsLock);
- threads[i].state = THREAD_WORKISWAITING; // This makes the slave to exit from idle_loop()
+ // We failed to allocate even one slave, return
+ if (!Fake && workersCnt == 1)
+ return bestValue;
- if (useSleepingThreads && i != master)
- 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
+ // 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.
- idle_loop(master, &splitPoint);
+ 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);
// We have returned from the idle loop, which means that all threads are
- // finished. Update alpha and bestValue, and return.
- lock_grab(&mpLock);
+ // 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);
- *alpha = splitPoint.alpha;
- *bestValue = splitPoint.bestValue;
+ masterThread.state = Thread::SEARCHING;
masterThread.activeSplitPoints--;
- masterThread.splitPoint = splitPoint.parent;
- pos.set_nodes_searched(pos.nodes_searched() + splitPoint.nodes);
- lock_release(&mpLock);
+ lock_release(&threadsLock);
+
+ masterThread.splitPoint = sp->parent;
+ pos.set_nodes_searched(pos.nodes_searched() + sp->nodes);
+
+ return sp->bestValue;
}
// Explicit template instantiations
-template void ThreadsManager::split<0>(Position&, SearchStack*, Value*, const Value, Value*, Depth, Move, int, MovePicker*, bool);
-template void ThreadsManager::split<1>(Position&, SearchStack*, Value*, const Value, Value*, Depth, Move, int, MovePicker*, bool);
+template Value ThreadsManager::split<false>(Position&, SearchStack*, Value, Value, Value, Depth, Move, int, MovePicker*, int);
+template Value ThreadsManager::split<true>(Position&, SearchStack*, Value, Value, Value, Depth, Move, int, MovePicker*, int);
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