2 Stockfish, a UCI chess playing engine derived from Glaurung 2.1
3 Copyright (C) 2004-2008 Tord Romstad (Glaurung author)
4 Copyright (C) 2008-2015 Marco Costalba, Joona Kiiski, Tord Romstad
5 Copyright (C) 2015-2019 Marco Costalba, Joona Kiiski, Gary Linscott, Tord Romstad
7 Stockfish is free software: you can redistribute it and/or modify
8 it under the terms of the GNU General Public License as published by
9 the Free Software Foundation, either version 3 of the License, or
10 (at your option) any later version.
12 Stockfish is distributed in the hope that it will be useful,
13 but WITHOUT ANY WARRANTY; without even the implied warranty of
14 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
15 GNU General Public License for more details.
17 You should have received a copy of the GNU General Public License
18 along with this program. If not, see <http://www.gnu.org/licenses/>.
23 #include <algorithm> // For std::count
28 #include "syzygy/tbprobe.h"
31 ThreadPool Threads; // Global object
34 /// Thread constructor launches the thread and waits until it goes to sleep
35 /// in idle_loop(). Note that 'searching' and 'exit' should be already set.
37 Thread::Thread(size_t n) : idx(n), stdThread(&Thread::idle_loop, this) {
39 wait_for_search_finished();
43 /// Thread destructor wakes up the thread in idle_loop() and waits
44 /// for its termination. Thread should be already waiting.
55 /// Thread::bestMoveCount(Move move) return best move counter for the given root move
57 int Thread::best_move_count(Move move) {
59 auto rm = std::find(rootMoves.begin() + pvIdx,
60 rootMoves.begin() + pvLast, move);
62 return rm != rootMoves.begin() + pvLast ? rm->bestMoveCount : 0;
65 /// Thread::clear() reset histories, usually before a new game
67 void Thread::clear() {
69 counterMoves.fill(MOVE_NONE);
71 captureHistory.fill(0);
73 for (StatsType c : { NoCaptures, Captures })
74 for (auto& to : continuationHistory[c])
78 for (StatsType c : { NoCaptures, Captures })
79 continuationHistory[c][NO_PIECE][0]->fill(Search::CounterMovePruneThreshold - 1);
82 /// Thread::start_searching() wakes up the thread that will start the search
84 void Thread::start_searching() {
86 std::lock_guard<std::mutex> lk(mutex);
88 cv.notify_one(); // Wake up the thread in idle_loop()
92 /// Thread::wait_for_search_finished() blocks on the condition variable
93 /// until the thread has finished searching.
95 void Thread::wait_for_search_finished() {
97 std::unique_lock<std::mutex> lk(mutex);
98 cv.wait(lk, [&]{ return !searching; });
102 /// Thread::idle_loop() is where the thread is parked, blocked on the
103 /// condition variable, when it has no work to do.
105 void Thread::idle_loop() {
107 // If OS already scheduled us on a different group than 0 then don't overwrite
108 // the choice, eventually we are one of many one-threaded processes running on
109 // some Windows NUMA hardware, for instance in fishtest. To make it simple,
110 // just check if running threads are below a threshold, in this case all this
111 // NUMA machinery is not needed.
112 if (Options["Threads"] > 8)
113 WinProcGroup::bindThisThread(idx);
117 std::unique_lock<std::mutex> lk(mutex);
119 cv.notify_one(); // Wake up anyone waiting for search finished
120 cv.wait(lk, [&]{ return searching; });
131 /// ThreadPool::set() creates/destroys threads to match the requested number.
132 /// Created and launched threads will immediately go to sleep in idle_loop.
133 /// Upon resizing, threads are recreated to allow for binding if necessary.
135 void ThreadPool::set(size_t requested) {
137 if (size() > 0) { // destroy any existing thread(s)
138 main()->wait_for_search_finished();
141 delete back(), pop_back();
144 if (requested > 0) { // create new thread(s)
145 push_back(new MainThread(0));
147 while (size() < requested)
148 push_back(new Thread(size()));
151 // Reallocate the hash with the new threadpool size
152 TT.resize(Options["Hash"]);
154 // Init thread number dependent search params.
159 /// ThreadPool::clear() sets threadPool data to initial values.
161 void ThreadPool::clear() {
163 for (Thread* th : *this)
166 main()->callsCnt = 0;
167 main()->previousScore = VALUE_INFINITE;
168 main()->previousTimeReduction = 1.0;
171 /// ThreadPool::start_thinking() wakes up main thread waiting in idle_loop() and
172 /// returns immediately. Main thread will wake up other threads and start the search.
174 void ThreadPool::start_thinking(Position& pos, StateListPtr& states,
175 const Search::LimitsType& limits, bool ponderMode) {
177 main()->wait_for_search_finished();
179 main()->stopOnPonderhit = stop = false;
180 main()->ponder = ponderMode;
181 Search::Limits = limits;
182 Search::RootMoves rootMoves;
184 for (const auto& m : MoveList<LEGAL>(pos))
185 if ( limits.searchmoves.empty()
186 || std::count(limits.searchmoves.begin(), limits.searchmoves.end(), m))
187 rootMoves.emplace_back(m);
189 if (!rootMoves.empty())
190 Tablebases::rank_root_moves(pos, rootMoves);
192 // After ownership transfer 'states' becomes empty, so if we stop the search
193 // and call 'go' again without setting a new position states.get() == NULL.
194 assert(states.get() || setupStates.get());
197 setupStates = std::move(states); // Ownership transfer, states is now empty
199 // We use Position::set() to set root position across threads. But there are
200 // some StateInfo fields (previous, pliesFromNull, capturedPiece) that cannot
201 // be deduced from a fen string, so set() clears them and to not lose the info
202 // we need to backup and later restore setupStates->back(). Note that setupStates
203 // is shared by threads but is accessed in read-only mode.
204 StateInfo tmp = setupStates->back();
206 for (Thread* th : *this)
208 th->shuffleExts = th->nodes = th->tbHits = th->nmpMinPly = 0;
209 th->rootDepth = th->completedDepth = 0;
210 th->rootMoves = rootMoves;
211 th->rootPos.set(pos.fen(), pos.is_chess960(), &setupStates->back(), th);
214 setupStates->back() = tmp;
216 main()->start_searching();