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/>.
23 #include "ucioption.h"
25 ThreadsManager Threads; // Global object definition
27 namespace { extern "C" {
29 // start_routine() is the C function which is called when a new thread
30 // is launched. It simply calls idle_loop() of the supplied thread. The
31 // last thread is dedicated to I/O and so runs in listener_loop().
34 DWORD WINAPI start_routine(LPVOID thread) {
36 void* start_routine(void* thread) {
39 if (((Thread*)thread)->threadID == MAX_THREADS)
40 ((Thread*)thread)->listener_loop();
42 ((Thread*)thread)->idle_loop(NULL);
50 // wake_up() wakes up the thread, normally at the beginning of the search or,
51 // if "sleeping threads" is used, when there is some work to do.
53 void Thread::wake_up() {
55 lock_grab(&sleepLock);
56 cond_signal(&sleepCond);
57 lock_release(&sleepLock);
61 // cutoff_occurred() checks whether a beta cutoff has occurred in the current
62 // active split point, or in some ancestor of the split point.
64 bool Thread::cutoff_occurred() const {
66 for (SplitPoint* sp = splitPoint; sp; sp = sp->parent)
67 if (sp->is_betaCutoff)
73 // is_available_to() checks whether the thread is available to help the thread with
74 // threadID "master" at a split point. An obvious requirement is that thread must be
75 // idle. With more than two threads, this is not by itself sufficient: If the thread
76 // is the master of some active split point, it is only available as a slave to the
77 // threads which are busy searching the split point at the top of "slave"'s split
78 // point stack (the "helpful master concept" in YBWC terminology).
80 bool Thread::is_available_to(int master) const {
85 // Make a local copy to be sure doesn't become zero under our feet while
86 // testing next condition and so leading to an out of bound access.
87 int localActiveSplitPoints = activeSplitPoints;
89 // No active split points means that the thread is available as a slave for any
90 // other thread otherwise apply the "helpful master" concept if possible.
91 if ( !localActiveSplitPoints
92 || splitPoints[localActiveSplitPoints - 1].is_slave[master])
99 // read_uci_options() updates number of active threads and other internal
100 // parameters according to the UCI options values. It is called before
101 // to start a new search.
103 void ThreadsManager::read_uci_options() {
105 maxThreadsPerSplitPoint = Options["Maximum Number of Threads per Split Point"].value<int>();
106 minimumSplitDepth = Options["Minimum Split Depth"].value<int>() * ONE_PLY;
107 useSleepingThreads = Options["Use Sleeping Threads"].value<bool>();
109 set_size(Options["Threads"].value<int>());
113 // set_size() changes the number of active threads and raises do_sleep flag for
114 // all the unused threads that will go immediately to sleep.
116 void ThreadsManager::set_size(int cnt) {
118 assert(cnt > 0 && cnt <= MAX_THREADS);
122 for (int i = 0; i < MAX_THREADS; i++)
123 if (i < activeThreads)
125 // Dynamically allocate pawn and material hash tables according to the
126 // number of active threads. This avoids preallocating memory for all
127 // possible threads if only few are used as, for instance, on mobile
128 // devices where memory is scarce and allocating for MAX_THREADS could
129 // even result in a crash.
130 threads[i].pawnTable.init();
131 threads[i].materialTable.init();
133 threads[i].do_sleep = false;
136 threads[i].do_sleep = true;
140 // init() is called during startup. Initializes locks and condition variables
141 // and launches all threads sending them immediately to sleep.
143 void ThreadsManager::init() {
145 // Initialize sleep condition used to block waiting for GUI input
146 cond_init(&sleepCond);
148 // Initialize threads lock, used when allocating slaves during splitting
149 lock_init(&threadsLock);
151 // Initialize sleep and split point locks
152 for (int i = 0; i <= MAX_THREADS; i++)
154 lock_init(&threads[i].sleepLock);
155 cond_init(&threads[i].sleepCond);
157 for (int j = 0; j < MAX_ACTIVE_SPLIT_POINTS; j++)
158 lock_init(&(threads[i].splitPoints[j].lock));
161 // Initialize main thread's associated data
162 threads[0].is_searching = true;
163 threads[0].threadID = 0;
164 set_size(1); // This makes all the threads but the main to go to sleep
166 // Create and launch all the threads but the main that is already running,
167 // threads will go immediately to sleep.
168 for (int i = 1; i <= MAX_THREADS; i++)
170 threads[i].is_searching = false;
171 threads[i].threadID = i;
173 #if defined(_MSC_VER)
174 threads[i].handle = CreateThread(NULL, 0, start_routine, (LPVOID)&threads[i], 0, NULL);
175 bool ok = (threads[i].handle != NULL);
177 bool ok = (pthread_create(&threads[i].handle, NULL, start_routine, (void*)&threads[i]) == 0);
182 std::cerr << "Failed to create thread number " << i << std::endl;
183 ::exit(EXIT_FAILURE);
189 // exit() is called to cleanly terminate the threads when the program finishes
191 void ThreadsManager::exit() {
193 for (int i = 0; i <= MAX_THREADS; i++)
197 threads[i].do_terminate = true;
198 threads[i].wake_up();
200 // Wait for slave termination
201 #if defined(_MSC_VER)
202 WaitForSingleObject(threads[i].handle, 0);
203 CloseHandle(threads[i].handle);
205 pthread_join(threads[i].handle, NULL);
209 // Now we can safely destroy locks and wait conditions
210 lock_destroy(&threads[i].sleepLock);
211 cond_destroy(&threads[i].sleepCond);
213 for (int j = 0; j < MAX_ACTIVE_SPLIT_POINTS; j++)
214 lock_destroy(&(threads[i].splitPoints[j].lock));
217 lock_destroy(&threadsLock);
218 cond_destroy(&sleepCond);
222 // available_slave_exists() tries to find an idle thread which is available as
223 // a slave for the thread with threadID "master".
225 bool ThreadsManager::available_slave_exists(int master) const {
227 assert(master >= 0 && master < activeThreads);
229 for (int i = 0; i < activeThreads; i++)
230 if (i != master && threads[i].is_available_to(master))
237 // split() does the actual work of distributing the work at a node between
238 // several available threads. If it does not succeed in splitting the
239 // node (because no idle threads are available, or because we have no unused
240 // split point objects), the function immediately returns. If splitting is
241 // possible, a SplitPoint object is initialized with all the data that must be
242 // copied to the helper threads and we tell our helper threads that they have
243 // been assigned work. This will cause them to instantly leave their idle loops and
244 // call search().When all threads have returned from search() then split() returns.
247 Value ThreadsManager::split(Position& pos, SearchStack* ss, Value alpha, Value beta,
248 Value bestValue, Depth depth, Move threatMove,
249 int moveCount, MovePicker* mp, int nodeType) {
250 assert(pos.pos_is_ok());
251 assert(bestValue >= -VALUE_INFINITE);
252 assert(bestValue <= alpha);
253 assert(alpha < beta);
254 assert(beta <= VALUE_INFINITE);
255 assert(depth > DEPTH_ZERO);
256 assert(pos.thread() >= 0 && pos.thread() < activeThreads);
257 assert(activeThreads > 1);
259 int i, master = pos.thread();
260 Thread& masterThread = threads[master];
262 // If we already have too many active split points, don't split
263 if (masterThread.activeSplitPoints >= MAX_ACTIVE_SPLIT_POINTS)
266 // Pick the next available split point object from the split point stack
267 SplitPoint* sp = masterThread.splitPoints + masterThread.activeSplitPoints;
269 // Initialize the split point object
270 sp->parent = masterThread.splitPoint;
272 sp->is_betaCutoff = false;
274 sp->threatMove = threatMove;
277 sp->nodeType = nodeType;
278 sp->bestValue = bestValue;
280 sp->moveCount = moveCount;
284 for (i = 0; i < activeThreads; i++)
285 sp->is_slave[i] = false;
287 // If we are here it means we are not available
288 assert(masterThread.is_searching);
290 int workersCnt = 1; // At least the master is included
292 // Try to allocate available threads and ask them to start searching setting
293 // the state to Thread::WORKISWAITING, this must be done under lock protection
294 // to avoid concurrent allocation of the same slave by another master.
295 lock_grab(&threadsLock);
297 for (i = 0; !Fake && i < activeThreads && workersCnt < maxThreadsPerSplitPoint; i++)
298 if (i != master && threads[i].is_available_to(master))
301 sp->is_slave[i] = true;
302 threads[i].splitPoint = sp;
304 // This makes the slave to exit from idle_loop()
305 threads[i].is_searching = true;
307 if (useSleepingThreads)
308 threads[i].wake_up();
311 lock_release(&threadsLock);
313 // We failed to allocate even one slave, return
314 if (!Fake && workersCnt == 1)
317 masterThread.splitPoint = sp;
318 masterThread.activeSplitPoints++;
320 // Everything is set up. The master thread enters the idle loop, from which
321 // it will instantly launch a search, because its is_searching flag is set.
322 // We pass the split point as a parameter to the idle loop, which means that
323 // the thread will return from the idle loop when all slaves have finished
324 // their work at this split point.
325 masterThread.idle_loop(sp);
327 // In helpful master concept a master can help only a sub-tree, and
328 // because here is all finished is not possible master is booked.
329 assert(!masterThread.is_searching);
331 // We have returned from the idle loop, which means that all threads are
332 // finished. Note that changing state and decreasing activeSplitPoints is done
333 // under lock protection to avoid a race with Thread::is_available_to().
334 lock_grab(&threadsLock);
336 masterThread.is_searching = true;
337 masterThread.activeSplitPoints--;
339 lock_release(&threadsLock);
341 masterThread.splitPoint = sp->parent;
342 pos.set_nodes_searched(pos.nodes_searched() + sp->nodes);
344 return sp->bestValue;
347 // Explicit template instantiations
348 template Value ThreadsManager::split<false>(Position&, SearchStack*, Value, Value, Value, Depth, Move, int, MovePicker*, int);
349 template Value ThreadsManager::split<true>(Position&, SearchStack*, Value, Value, Value, Depth, Move, int, MovePicker*, int);
352 // Thread::listner_loop() is where the last thread, used for IO, waits for input.
353 // Input is read in sync with main thread (that blocks) when is_searching is set
354 // to false, otherwise IO thread reads any input asynchronously and processes
355 // the input line calling do_uci_async_cmd().
357 void Thread::listener_loop() {
363 lock_grab(&sleepLock);
365 Threads.inputLine = cmd;
366 do_sleep = !is_searching;
368 // Here the thread is parked in sync mode after a line has been read
369 while (do_sleep && !do_terminate) // Catches spurious wake ups
371 cond_signal(&Threads.sleepCond); // Wake up main thread
372 cond_wait(&sleepCond, &sleepLock); // Sleep here
375 lock_release(&sleepLock);
380 if (!std::getline(std::cin, cmd)) // Block waiting for input
383 lock_grab(&sleepLock);
385 // If we are in async mode then process the command now
388 // Command "quit" is the last one received by the GUI, so park the
389 // thread waiting for exiting.
391 is_searching = false;
393 Threads.do_uci_async_cmd(cmd);
394 cmd = ""; // Input has been consumed
397 lock_release(&sleepLock);
402 // ThreadsManager::getline() is used by main thread to block and wait for input,
403 // the behaviour mimics std::getline().
405 void ThreadsManager::getline(std::string& cmd) {
407 Thread& listener = threads[MAX_THREADS];
409 lock_grab(&listener.sleepLock);
411 listener.is_searching = false; // Set sync mode
413 // If there is already some input to grab then skip without to wake up the
414 // listener. This can happen if after we send the "bestmove", the GUI sends
415 // a command that the listener buffers in inputLine before going to sleep.
416 if (inputLine.empty())
418 listener.do_sleep = false;
419 cond_signal(&listener.sleepCond); // Wake up listener thread
421 while (!listener.do_sleep)
422 cond_wait(&sleepCond, &listener.sleepLock); // Wait for input
426 inputLine = ""; // Input has been consumed
428 lock_release(&listener.sleepLock);
432 // ThreadsManager::start_listener() is called at the beginning of the search to
433 // swith from sync behaviour (default) to async and so be able to read from UCI
434 // while other threads are searching. This avoids main thread polling for input.
436 void ThreadsManager::start_listener() {
438 Thread& listener = threads[MAX_THREADS];
440 lock_grab(&listener.sleepLock);
441 listener.is_searching = true;
442 listener.do_sleep = false;
443 cond_signal(&listener.sleepCond); // Wake up listener thread
444 lock_release(&listener.sleepLock);
448 // ThreadsManager::stop_listener() is called before to send "bestmove" to GUI to
449 // return to in-sync behaviour. This is needed because while in async mode any
450 // command is discarded without being processed (except for a very few ones).
452 void ThreadsManager::stop_listener() {
454 Thread& listener = threads[MAX_THREADS];
456 lock_grab(&listener.sleepLock);
457 listener.is_searching = false;
458 lock_release(&listener.sleepLock);