2 Stockfish, a UCI chess playing engine derived from Glaurung 2.1
3 Copyright (C) 2004-2008 Tord Romstad (Glaurung author)
4 Copyright (C) 2008-2010 Marco Costalba, Joona Kiiski, Tord Romstad
6 Stockfish is free software: you can redistribute it and/or modify
7 it under the terms of the GNU General Public License as published by
8 the Free Software Foundation, either version 3 of the License, or
9 (at your option) any later version.
11 Stockfish is distributed in the hope that it will be useful,
12 but WITHOUT ANY WARRANTY; without even the implied warranty of
13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
14 GNU General Public License for more details.
16 You should have received a copy of the GNU General Public License
17 along with this program. If not, see <http://www.gnu.org/licenses/>.
24 #include "ucioption.h"
26 ThreadsManager Threads; // Global object definition
28 namespace { extern "C" {
30 // start_routine() is the C function which is called when a new thread
31 // is launched. It simply calls idle_loop() of the supplied thread. The
32 // last two threads are dedicated to read input from GUI and to mimic a
33 // timer, so they run in listener_loop() and timer_loop() respectively.
36 DWORD WINAPI start_routine(LPVOID thread) {
38 void* start_routine(void* thread) {
41 if (((Thread*)thread)->threadID == MAX_THREADS)
42 ((Thread*)thread)->listener_loop();
44 else if (((Thread*)thread)->threadID == MAX_THREADS + 1)
45 ((Thread*)thread)->timer_loop();
47 ((Thread*)thread)->idle_loop(NULL);
55 // wake_up() wakes up the thread, normally at the beginning of the search or,
56 // if "sleeping threads" is used, when there is some work to do.
58 void Thread::wake_up() {
60 lock_grab(&sleepLock);
61 cond_signal(&sleepCond);
62 lock_release(&sleepLock);
66 // cutoff_occurred() checks whether a beta cutoff has occurred in the current
67 // active split point, or in some ancestor of the split point.
69 bool Thread::cutoff_occurred() const {
71 for (SplitPoint* sp = splitPoint; sp; sp = sp->parent)
72 if (sp->is_betaCutoff)
78 // is_available_to() checks whether the thread is available to help the thread with
79 // threadID "master" at a split point. An obvious requirement is that thread must be
80 // idle. With more than two threads, this is not by itself sufficient: If the thread
81 // is the master of some active split point, it is only available as a slave to the
82 // threads which are busy searching the split point at the top of "slave"'s split
83 // point stack (the "helpful master concept" in YBWC terminology).
85 bool Thread::is_available_to(int master) const {
90 // Make a local copy to be sure doesn't become zero under our feet while
91 // testing next condition and so leading to an out of bound access.
92 int localActiveSplitPoints = activeSplitPoints;
94 // No active split points means that the thread is available as a slave for any
95 // other thread otherwise apply the "helpful master" concept if possible.
96 if ( !localActiveSplitPoints
97 || splitPoints[localActiveSplitPoints - 1].is_slave[master])
104 // read_uci_options() updates number of active threads and other internal
105 // parameters according to the UCI options values. It is called before
106 // to start a new search.
108 void ThreadsManager::read_uci_options() {
110 maxThreadsPerSplitPoint = Options["Maximum Number of Threads per Split Point"].value<int>();
111 minimumSplitDepth = Options["Minimum Split Depth"].value<int>() * ONE_PLY;
112 useSleepingThreads = Options["Use Sleeping Threads"].value<bool>();
114 set_size(Options["Threads"].value<int>());
118 // set_size() changes the number of active threads and raises do_sleep flag for
119 // all the unused threads that will go immediately to sleep.
121 void ThreadsManager::set_size(int cnt) {
123 assert(cnt > 0 && cnt <= MAX_THREADS);
127 for (int i = 0; i < MAX_THREADS; i++)
128 if (i < activeThreads)
130 // Dynamically allocate pawn and material hash tables according to the
131 // number of active threads. This avoids preallocating memory for all
132 // possible threads if only few are used as, for instance, on mobile
133 // devices where memory is scarce and allocating for MAX_THREADS could
134 // even result in a crash.
135 threads[i].pawnTable.init();
136 threads[i].materialTable.init();
138 threads[i].do_sleep = false;
141 threads[i].do_sleep = true;
145 // init() is called during startup. Initializes locks and condition variables
146 // and launches all threads sending them immediately to sleep.
148 void ThreadsManager::init() {
150 // Initialize sleep condition used to block waiting for GUI input
151 cond_init(&sleepCond);
153 // Initialize threads lock, used when allocating slaves during splitting
154 lock_init(&threadsLock);
156 // Initialize sleep and split point locks
157 for (int i = 0; i < MAX_THREADS + 2; i++)
159 lock_init(&threads[i].sleepLock);
160 cond_init(&threads[i].sleepCond);
162 for (int j = 0; j < MAX_ACTIVE_SPLIT_POINTS; j++)
163 lock_init(&(threads[i].splitPoints[j].lock));
166 // Initialize main thread's associated data
167 threads[0].is_searching = true;
168 threads[0].threadID = 0;
169 set_size(1); // This makes all the threads but the main to go to sleep
171 // Create and launch all the threads but the main that is already running,
172 // threads will go immediately to sleep.
173 for (int i = 1; i < MAX_THREADS + 2; i++)
175 threads[i].is_searching = false;
176 threads[i].threadID = i;
178 #if defined(_MSC_VER)
179 threads[i].handle = CreateThread(NULL, 0, start_routine, (LPVOID)&threads[i], 0, NULL);
180 bool ok = (threads[i].handle != NULL);
182 bool ok = (pthread_create(&threads[i].handle, NULL, start_routine, (void*)&threads[i]) == 0);
187 std::cerr << "Failed to create thread number " << i << std::endl;
188 ::exit(EXIT_FAILURE);
194 // exit() is called to cleanly terminate the threads when the program finishes
196 void ThreadsManager::exit() {
198 for (int i = 0; i < MAX_THREADS + 2; i++)
202 threads[i].do_terminate = true;
203 threads[i].wake_up();
205 // Wait for slave termination
206 #if defined(_MSC_VER)
207 WaitForSingleObject(threads[i].handle, 0);
208 CloseHandle(threads[i].handle);
210 pthread_join(threads[i].handle, NULL);
214 // Now we can safely destroy locks and wait conditions
215 lock_destroy(&threads[i].sleepLock);
216 cond_destroy(&threads[i].sleepCond);
218 for (int j = 0; j < MAX_ACTIVE_SPLIT_POINTS; j++)
219 lock_destroy(&(threads[i].splitPoints[j].lock));
222 lock_destroy(&threadsLock);
223 cond_destroy(&sleepCond);
227 // available_slave_exists() tries to find an idle thread which is available as
228 // a slave for the thread with threadID "master".
230 bool ThreadsManager::available_slave_exists(int master) const {
232 assert(master >= 0 && master < activeThreads);
234 for (int i = 0; i < activeThreads; i++)
235 if (i != master && threads[i].is_available_to(master))
242 // split_point_finished() checks if all the slave threads of a given split
243 // point have finished searching.
245 bool ThreadsManager::split_point_finished(SplitPoint* sp) const {
247 for (int i = 0; i < activeThreads; i++)
255 // split() does the actual work of distributing the work at a node between
256 // several available threads. If it does not succeed in splitting the
257 // node (because no idle threads are available, or because we have no unused
258 // split point objects), the function immediately returns. If splitting is
259 // possible, a SplitPoint object is initialized with all the data that must be
260 // copied to the helper threads and we tell our helper threads that they have
261 // been assigned work. This will cause them to instantly leave their idle loops and
262 // call search().When all threads have returned from search() then split() returns.
265 Value ThreadsManager::split(Position& pos, SearchStack* ss, Value alpha, Value beta,
266 Value bestValue, Depth depth, Move threatMove,
267 int moveCount, MovePicker* mp, int nodeType) {
268 assert(pos.pos_is_ok());
269 assert(bestValue >= -VALUE_INFINITE);
270 assert(bestValue <= alpha);
271 assert(alpha < beta);
272 assert(beta <= VALUE_INFINITE);
273 assert(depth > DEPTH_ZERO);
274 assert(pos.thread() >= 0 && pos.thread() < activeThreads);
275 assert(activeThreads > 1);
277 int i, master = pos.thread();
278 Thread& masterThread = threads[master];
280 // If we already have too many active split points, don't split
281 if (masterThread.activeSplitPoints >= MAX_ACTIVE_SPLIT_POINTS)
284 // Pick the next available split point object from the split point stack
285 SplitPoint* sp = masterThread.splitPoints + masterThread.activeSplitPoints;
287 // Initialize the split point object
288 sp->parent = masterThread.splitPoint;
290 sp->is_betaCutoff = false;
292 sp->threatMove = threatMove;
295 sp->nodeType = nodeType;
296 sp->bestValue = bestValue;
298 sp->moveCount = moveCount;
302 for (i = 0; i < activeThreads; i++)
303 sp->is_slave[i] = false;
305 // If we are here it means we are not available
306 assert(masterThread.is_searching);
308 int workersCnt = 1; // At least the master is included
310 // Try to allocate available threads and ask them to start searching setting
311 // the state to Thread::WORKISWAITING, this must be done under lock protection
312 // to avoid concurrent allocation of the same slave by another master.
313 lock_grab(&threadsLock);
315 for (i = 0; !Fake && i < activeThreads && workersCnt < maxThreadsPerSplitPoint; i++)
316 if (i != master && threads[i].is_available_to(master))
319 sp->is_slave[i] = true;
320 threads[i].splitPoint = sp;
322 // This makes the slave to exit from idle_loop()
323 threads[i].is_searching = true;
325 if (useSleepingThreads)
326 threads[i].wake_up();
329 lock_release(&threadsLock);
331 // We failed to allocate even one slave, return
332 if (!Fake && workersCnt == 1)
335 masterThread.splitPoint = sp;
336 masterThread.activeSplitPoints++;
338 // Everything is set up. The master thread enters the idle loop, from which
339 // it will instantly launch a search, because its is_searching flag is set.
340 // We pass the split point as a parameter to the idle loop, which means that
341 // the thread will return from the idle loop when all slaves have finished
342 // their work at this split point.
343 masterThread.idle_loop(sp);
345 // In helpful master concept a master can help only a sub-tree, and
346 // because here is all finished is not possible master is booked.
347 assert(!masterThread.is_searching);
349 // We have returned from the idle loop, which means that all threads are
350 // finished. Note that changing state and decreasing activeSplitPoints is done
351 // under lock protection to avoid a race with Thread::is_available_to().
352 lock_grab(&threadsLock);
354 masterThread.is_searching = true;
355 masterThread.activeSplitPoints--;
357 lock_release(&threadsLock);
359 masterThread.splitPoint = sp->parent;
360 pos.set_nodes_searched(pos.nodes_searched() + sp->nodes);
362 return sp->bestValue;
365 // Explicit template instantiations
366 template Value ThreadsManager::split<false>(Position&, SearchStack*, Value, Value, Value, Depth, Move, int, MovePicker*, int);
367 template Value ThreadsManager::split<true>(Position&, SearchStack*, Value, Value, Value, Depth, Move, int, MovePicker*, int);
370 // Thread::timer_loop() is where the timer thread waits maxPly milliseconds
371 // and then calls do_timer_event().
373 void Thread::timer_loop() {
375 while (!do_terminate)
377 lock_grab(&sleepLock);
378 timed_wait(&sleepCond, &sleepLock, maxPly ? maxPly : INT_MAX);
379 lock_release(&sleepLock);
385 // ThreadsManager::set_timer() is used to set the timer to trigger after msec
386 // milliseconds. If msec is 0 then timer is stopped.
388 void ThreadsManager::set_timer(int msec) {
390 Thread& timer = threads[MAX_THREADS + 1];
392 lock_grab(&timer.sleepLock);
394 cond_signal(&timer.sleepCond); // Wake up and restart the timer
395 lock_release(&timer.sleepLock);
399 // Thread::listener_loop() is where the listener thread, used for I/O, waits for
400 // input. When is_searching is false then input is read in sync with main thread
401 // (that blocks), otherwise the listener thread reads any input asynchronously
402 // and processes the input line calling do_uci_async_cmd().
404 void Thread::listener_loop() {
410 lock_grab(&sleepLock);
412 Threads.inputLine = cmd;
413 do_sleep = !is_searching;
415 // Here the thread is parked in sync mode after a line has been read
416 while (do_sleep && !do_terminate) // Catches spurious wake ups
418 cond_signal(&Threads.sleepCond); // Wake up main thread
419 cond_wait(&sleepCond, &sleepLock); // Sleep here
422 lock_release(&sleepLock);
427 if (!std::getline(std::cin, cmd)) // Block waiting for input
430 lock_grab(&sleepLock);
432 // If we are in async mode then process the command now
435 // Command "quit" is the last one received by the GUI, so park the
436 // thread waiting for exiting. Also, after a "stop", for instance on a
437 // ponder miss, GUI can immediately send the new position to search,
438 // so return to in-sync mode to avoid discarding good data.
439 if (cmd == "quit" || cmd == "stop")
440 is_searching = false;
442 do_uci_async_cmd(cmd);
443 cmd = ""; // Input has been consumed
446 lock_release(&sleepLock);
451 // ThreadsManager::getline() is used by main thread to block and wait for input,
452 // the behaviour mimics std::getline().
454 void ThreadsManager::getline(std::string& cmd) {
456 Thread& listener = threads[MAX_THREADS];
458 lock_grab(&listener.sleepLock);
460 listener.is_searching = false; // Set sync mode
462 // If there is already some input to grab then skip without to wake up the
463 // listener. This can happen if after we send the "bestmove", the GUI sends
464 // a command that the listener buffers in inputLine before going to sleep.
465 if (inputLine.empty())
467 listener.do_sleep = false;
468 cond_signal(&listener.sleepCond); // Wake up listener thread
470 while (!listener.do_sleep)
471 cond_wait(&sleepCond, &listener.sleepLock); // Wait for input
475 inputLine = ""; // Input has been consumed
477 lock_release(&listener.sleepLock);
481 // ThreadsManager::start_listener() is called at the beginning of the search to
482 // swith from sync behaviour (default) to async and so be able to read from UCI
483 // while other threads are searching. This avoids main thread polling for input.
485 void ThreadsManager::start_listener() {
487 Thread& listener = threads[MAX_THREADS];
489 lock_grab(&listener.sleepLock);
490 listener.is_searching = true;
491 listener.do_sleep = false;
492 cond_signal(&listener.sleepCond); // Wake up listener thread
493 lock_release(&listener.sleepLock);
497 // ThreadsManager::stop_listener() is called before to send "bestmove" to GUI to
498 // return to in-sync behaviour. This is needed because while in async mode any
499 // command is discarded without being processed (except for a very few ones).
501 void ThreadsManager::stop_listener() {
503 Thread& listener = threads[MAX_THREADS];
505 lock_grab(&listener.sleepLock);
506 listener.is_searching = false;
507 lock_release(&listener.sleepLock);