X-Git-Url: https://git.sesse.net/?p=stockfish;a=blobdiff_plain;f=src%2Fthread.cpp;h=e1330396d0007f30815c3ba95d2142c9ad8bb1d7;hp=002819de566ce71a2c91e2566ca481bf1376445c;hb=5b35c149e833e365c2afb8039ca5c658abc53081;hpb=339e1b49f619ceffa75019e196adf4de74b32cce diff --git a/src/thread.cpp b/src/thread.cpp index 002819de..e1330396 100644 --- a/src/thread.cpp +++ b/src/thread.cpp @@ -22,33 +22,83 @@ #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.idle_loop(*(int*)threadID, NULL); + return 0; } #else - DWORD WINAPI init_thread(LPVOID threadID) { + void* start_routine(void* threadID) { - ThreadsMgr.idle_loop(*(int*)threadID, NULL); - return 0; + Threads.idle_loop(*(int*)threadID, 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; } @@ -65,24 +115,24 @@ void ThreadsManager::read_uci_options() { } -// init_threads() is called during startup. Initializes locks and condition -// variables and launches all threads sending them immediately to sleep. +// init() is called during startup. Initializes locks and condition variables +// and launches all threads sending them immediately to sleep. -void ThreadsManager::init_threads() { +void ThreadsManager::init() { - int arg[MAX_THREADS]; + int threadID[MAX_THREADS]; // This flag is needed to properly end the threads when program exits allThreadsShouldExit = false; // Threads will sent to sleep as soon as created, only main thread is kept alive activeThreads = 1; - threads[0].state = THREAD_SEARCHING; + threads[0].state = Thread::SEARCHING; // Allocate pawn and material hash tables for main thread init_hash_tables(); - lock_init(&mpLock); + lock_init(&threadsLock); // Initialize thread and split point locks for (int i = 0; i < MAX_THREADS; i++) @@ -97,32 +147,31 @@ void ThreadsManager::init_threads() { // 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; + threadID[i] = 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)&threadID[i], 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*)&threadID[i]) == 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 exit the threads when the program finishes -void ThreadsManager::exit_threads() { +void ThreadsManager::exit() { // Force the woken up threads to exit idle_loop() and hence terminate allThreadsShouldExit = true; @@ -133,7 +182,7 @@ void ThreadsManager::exit_threads() { if (i != 0) { 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 @@ -144,7 +193,7 @@ void ThreadsManager::exit_threads() { lock_destroy(&(threads[i].splitPoints[j].lock)); } - lock_destroy(&mpLock); + lock_destroy(&threadsLock); } @@ -164,66 +213,15 @@ void ThreadsManager::init_hash_tables() { } -// 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; @@ -240,13 +238,13 @@ bool ThreadsManager::available_thread_exists(int master) const { // call search().When all threads have returned from search() then split() returns. template -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); @@ -255,68 +253,68 @@ void ThreadsManager::split(Position& pos, SearchStack* ss, Value* alpha, const V 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& splitPoint = masterThread.splitPoints[masterThread.activeSplitPoints]; // Initialize the split point object splitPoint.parent = masterThread.splitPoint; splitPoint.master = master; - splitPoint.betaCutoff = false; + splitPoint.is_betaCutoff = false; splitPoint.depth = depth; splitPoint.threatMove = threatMove; - splitPoint.alpha = *alpha; + splitPoint.alpha = alpha; splitPoint.beta = beta; - splitPoint.pvNode = pvNode; - splitPoint.bestValue = *bestValue; + splitPoint.nodeType = nodeType; + splitPoint.bestValue = bestValue; splitPoint.mp = mp; splitPoint.moveCount = moveCount; splitPoint.pos = &pos; splitPoint.nodes = 0; splitPoint.ss = ss; for (i = 0; i < activeThreads; i++) - splitPoint.slaves[i] = 0; - - masterThread.splitPoint = &splitPoint; + splitPoint.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 + int booked = 0; - // Allocate available threads setting state to THREAD_BOOKED - for (i = 0; !Fake && i < activeThreads && workersCnt < maxThreadsPerSplitPoint; i++) - if (thread_is_available(i, master)) + // Try to allocate available threads setting state to Thread::BOOKED, 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 && booked < maxThreadsPerSplitPoint; i++) + if (i != master && threads[i].is_available_to(master)) { - threads[i].state = THREAD_BOOKED; + threads[i].state = Thread::BOOKED; threads[i].splitPoint = &splitPoint; - splitPoint.slaves[i] = 1; - workersCnt++; + splitPoint.is_slave[i] = true; + booked++; } - assert(Fake || workersCnt > 1); + lock_release(&threadsLock); + + // We failed to allocate even one slave, return + if (!Fake && !booked) + return bestValue; - // We can release the lock because slave threads are already booked and master is not available - lock_release(&mpLock); + masterThread.activeSplitPoints++; + masterThread.splitPoint = &splitPoint; - // Tell the threads that they have work to do. This will make them leave + // Tell the threads that they have some work to do. This will make them leave // their idle loop. for (i = 0; i < activeThreads; i++) - if (i == master || splitPoint.slaves[i]) + if (i == master || splitPoint.is_slave[i]) { - assert(i == master || threads[i].state == THREAD_BOOKED); + assert(i == master || threads[i].state == Thread::BOOKED); - threads[i].state = THREAD_WORKISWAITING; // This makes the slave to exit from idle_loop() + // This makes the slave to exit from idle_loop() + threads[i].state = Thread::WORKISWAITING; if (useSleepingThreads && i != master) threads[i].wake_up(); @@ -330,18 +328,20 @@ void ThreadsManager::split(Position& pos, SearchStack* ss, Value* alpha, const V idle_loop(master, &splitPoint); // 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); + + pos.set_nodes_searched(pos.nodes_searched() + splitPoint.nodes); + return splitPoint.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(Position&, SearchStack*, Value, Value, Value, Depth, Move, int, MovePicker*, int); +template Value ThreadsManager::split(Position&, SearchStack*, Value, Value, Value, Depth, Move, int, MovePicker*, int);