1/*
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
6
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.
11
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.
16
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/>.
19*/
20
21#include <cassert>
22
23#include <algorithm> // For std::count
24#include "movegen.h"
25#include "search.h"
26#include "thread.h"
27#include "uci.h"
28#include "syzygy/tbprobe.h"
29#include "tt.h"
30
31ThreadPool Threads; // Global object
32
33
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.
36
37Thread::Thread(size_t n) : idx(n), stdThread(&Thread::idle_loop, this) {
38
39 wait_for_search_finished();
40}
41
42
43/// Thread destructor wakes up the thread in idle_loop() and waits
44/// for its termination. Thread should be already waiting.
45
46Thread::~Thread() {
47
48 assert(!searching);
49
50 exit = true;
51 start_searching();
52 stdThread.join();
53}
54
55
56/// Thread::clear() reset histories, usually before a new game
57
58void Thread::clear() {
59
60 counterMoves.fill(MOVE_NONE);
61 mainHistory.fill(0);
62 captureHistory.fill(0);
63
64 for (auto& to : continuationHistory)
65 for (auto& h : to)
66 h->fill(0);
67
68 continuationHistory[NO_PIECE][0]->fill(Search::CounterMovePruneThreshold - 1);
69}
70
71/// Thread::start_searching() wakes up the thread that will start the search
72
73void Thread::start_searching() {
74
75 std::lock_guard<Mutex> lk(mutex);
76 searching = true;
77 cv.notify_one(); // Wake up the thread in idle_loop()
78}
79
80
81/// Thread::wait_for_search_finished() blocks on the condition variable
82/// until the thread has finished searching.
83
84void Thread::wait_for_search_finished() {
85
86 std::unique_lock<Mutex> lk(mutex);
87 cv.wait(lk, [&]{ return !searching; });
88}
89
90
91/// Thread::idle_loop() is where the thread is parked, blocked on the
92/// condition variable, when it has no work to do.
93
94void Thread::idle_loop() {
95
96 // If OS already scheduled us on a different group than 0 then don't overwrite
97 // the choice, eventually we are one of many one-threaded processes running on
98 // some Windows NUMA hardware, for instance in fishtest. To make it simple,
99 // just check if running threads are below a threshold, in this case all this
100 // NUMA machinery is not needed.
101 if (Options["Threads"] > 8)
102 WinProcGroup::bindThisThread(idx);
103
104 while (true)
105 {
106 std::unique_lock<Mutex> lk(mutex);
107 searching = false;
108 cv.notify_one(); // Wake up anyone waiting for search finished
109 cv.wait(lk, [&]{ return searching; });
110
111 if (exit)
112 return;
113
114 lk.unlock();
115
116 search();
117 }
118}
119
120/// ThreadPool::set() creates/destroys threads to match the requested number.
121/// Created and launched threads will immediately go to sleep in idle_loop.
122/// Upon resizing, threads are recreated to allow for binding if necessary.
123
124void ThreadPool::set(size_t requested) {
125
126 if (size() > 0) { // destroy any existing thread(s)
127 main()->wait_for_search_finished();
128
129 while (size() > 0)
130 delete back(), pop_back();
131 }
132
133 if (requested > 0) { // create new thread(s)
134 push_back(new MainThread(0));
135
136 while (size() < requested)
137 push_back(new Thread(size()));
138 clear();
139
140 // Reallocate the hash with the new threadpool size
141 TT.resize(Options["Hash"]);
142 }
143}
144
145/// ThreadPool::clear() sets threadPool data to initial values.
146
147void ThreadPool::clear() {
148
149 for (Thread* th : *this)
150 th->clear();
151
152 main()->callsCnt = 0;
153 main()->previousScore = VALUE_INFINITE;
154 main()->previousTimeReduction = 1.0;
155}
156
157/// ThreadPool::start_thinking() wakes up main thread waiting in idle_loop() and
158/// returns immediately. Main thread will wake up other threads and start the search.
159
160void ThreadPool::start_thinking(Position& pos, StateListPtr& states,
161 const Search::LimitsType& limits, bool ponderMode) {
162
163 main()->wait_for_search_finished();
164
165 main()->stopOnPonderhit = stop = false;
166 main()->ponder = ponderMode;
167 Search::Limits = limits;
168 Search::RootMoves rootMoves;
169
170 for (const auto& m : MoveList<LEGAL>(pos))
171 if ( limits.searchmoves.empty()
172 || std::count(limits.searchmoves.begin(), limits.searchmoves.end(), m))
173 rootMoves.emplace_back(m);
174
175 if (!rootMoves.empty())
176 Tablebases::rank_root_moves(pos, rootMoves);
177
178 // After ownership transfer 'states' becomes empty, so if we stop the search
179 // and call 'go' again without setting a new position states.get() == NULL.
180 assert(states.get() || setupStates.get());
181
182 if (states.get())
183 setupStates = std::move(states); // Ownership transfer, states is now empty
184
185 // We use Position::set() to set root position across threads. But there are
186 // some StateInfo fields (previous, pliesFromNull, capturedPiece) that cannot
187 // be deduced from a fen string, so set() clears them and to not lose the info
188 // we need to backup and later restore setupStates->back(). Note that setupStates
189 // is shared by threads but is accessed in read-only mode.
190 StateInfo tmp = setupStates->back();
191
192 for (Thread* th : *this)
193 {
194 th->shuffleExts = th->nodes = th->tbHits = th->nmpMinPly = 0;
195 th->rootDepth = th->completedDepth = DEPTH_ZERO;
196 th->rootMoves = rootMoves;
197 th->rootPos.set(pos.fen(), pos.is_chess960(), &setupStates->back(), th);
198 }
199
200 setupStates->back() = tmp;
201
202 main()->start_searching();
203}
204