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) 2015-2020 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) const {
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 (bool inCheck : { false, true })
74 for (StatsType c : { NoCaptures, Captures })
76 for (auto& to : continuationHistory[inCheck][c])
79 continuationHistory[inCheck][c][NO_PIECE][0]->fill(Search::CounterMovePruneThreshold - 1);
83 /// Thread::start_searching() wakes up the thread that will start the search
85 void Thread::start_searching() {
87 std::lock_guard<std::mutex> lk(mutex);
89 cv.notify_one(); // Wake up the thread in idle_loop()
93 /// Thread::wait_for_search_finished() blocks on the condition variable
94 /// until the thread has finished searching.
96 void Thread::wait_for_search_finished() {
98 std::unique_lock<std::mutex> lk(mutex);
99 cv.wait(lk, [&]{ return !searching; });
103 /// Thread::idle_loop() is where the thread is parked, blocked on the
104 /// condition variable, when it has no work to do.
106 void Thread::idle_loop() {
108 // If OS already scheduled us on a different group than 0 then don't overwrite
109 // the choice, eventually we are one of many one-threaded processes running on
110 // some Windows NUMA hardware, for instance in fishtest. To make it simple,
111 // just check if running threads are below a threshold, in this case all this
112 // NUMA machinery is not needed.
113 if (Options["Threads"] > 8)
114 WinProcGroup::bindThisThread(idx);
118 std::unique_lock<std::mutex> lk(mutex);
120 cv.notify_one(); // Wake up anyone waiting for search finished
121 cv.wait(lk, [&]{ return searching; });
132 /// ThreadPool::set() creates/destroys threads to match the requested number.
133 /// Created and launched threads will immediately go to sleep in idle_loop.
134 /// Upon resizing, threads are recreated to allow for binding if necessary.
136 void ThreadPool::set(size_t requested) {
138 if (size() > 0) { // destroy any existing thread(s)
139 main()->wait_for_search_finished();
142 delete back(), pop_back();
145 if (requested > 0) { // create new thread(s)
146 push_back(new MainThread(0));
148 while (size() < requested)
149 push_back(new Thread(size()));
152 // Reallocate the hash with the new threadpool size
153 TT.resize(Options["Hash"]);
155 // Init thread number dependent search params.
160 /// ThreadPool::clear() sets threadPool data to initial values.
162 void ThreadPool::clear() {
164 for (Thread* th : *this)
167 main()->callsCnt = 0;
168 main()->previousScore = VALUE_INFINITE;
169 main()->previousTimeReduction = 1.0;
172 /// ThreadPool::start_thinking() wakes up main thread waiting in idle_loop() and
173 /// returns immediately. Main thread will wake up other threads and start the search.
175 void ThreadPool::start_thinking(Position& pos, StateListPtr& states,
176 const Search::LimitsType& limits, bool ponderMode) {
178 main()->wait_for_search_finished();
180 main()->stopOnPonderhit = stop = false;
181 increaseDepth = true;
182 main()->ponder = ponderMode;
183 Search::Limits = limits;
184 Search::RootMoves rootMoves;
186 for (const auto& m : MoveList<LEGAL>(pos))
187 if ( limits.searchmoves.empty()
188 || std::count(limits.searchmoves.begin(), limits.searchmoves.end(), m))
189 rootMoves.emplace_back(m);
191 if (!rootMoves.empty())
192 Tablebases::rank_root_moves(pos, rootMoves);
194 // After ownership transfer 'states' becomes empty, so if we stop the search
195 // and call 'go' again without setting a new position states.get() == NULL.
196 assert(states.get() || setupStates.get());
199 setupStates = std::move(states); // Ownership transfer, states is now empty
201 // We use Position::set() to set root position across threads. But there are
202 // some StateInfo fields (previous, pliesFromNull, capturedPiece) that cannot
203 // be deduced from a fen string, so set() clears them and to not lose the info
204 // we need to backup and later restore setupStates->back(). Note that setupStates
205 // is shared by threads but is accessed in read-only mode.
206 StateInfo tmp = setupStates->back();
208 for (Thread* th : *this)
210 th->nodes = th->tbHits = th->nmpMinPly = 0;
211 th->rootDepth = th->completedDepth = 0;
212 th->rootMoves = rootMoves;
213 th->rootPos.set(pos.fen(), pos.is_chess960(), &setupStates->back(), th);
216 setupStates->back() = tmp;
218 main()->start_searching();