/*
Stockfish, a UCI chess playing engine derived from Glaurung 2.1
Copyright (C) 2004-2008 Tord Romstad (Glaurung author)
Copyright (C) 2008-2015 Marco Costalba, Joona Kiiski, Tord Romstad
Copyright (C) 2015-2019 Marco Costalba, Joona Kiiski, Gary Linscott, Tord Romstad
Stockfish is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.
Stockfish is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
#include <algorithm> // For std::count
#include <cassert>
#include "movegen.h"
#include "search.h"
#include "thread.h"
#include "uci.h"
#include "syzygy/tbprobe.h"
#include "tt.h"
ThreadPool Threads; // Global object
/// Thread constructor launches the thread and waits until it goes to sleep
/// in idle_loop(). Note that 'searching' and 'exit' should be alredy set.
Thread::Thread(size_t n) : idx(n), stdThread(&Thread::idle_loop, this) {
wait_for_search_finished();
}
/// Thread destructor wakes up the thread in idle_loop() and waits
/// for its termination. Thread should be already waiting.
Thread::~Thread() {
assert(!searching);
exit = true;
start_searching();
stdThread.join();
}
/// Thread::clear() reset histories, usually before a new game
void Thread::clear() {
counterMoves.fill(MOVE_NONE);
mainHistory.fill(0);
captureHistory.fill(0);
for (auto& to : continuationHistory)
for (auto& h : to)
h->fill(0);
continuationHistory[NO_PIECE][0]->fill(Search::CounterMovePruneThreshold - 1);
}
/// Thread::start_searching() wakes up the thread that will start the search
void Thread::start_searching() {
std::lock_guard<Mutex> lk(mutex);
searching = true;
cv.notify_one(); // Wake up the thread in idle_loop()
}
/// Thread::wait_for_search_finished() blocks on the condition variable
/// until the thread has finished searching.
void Thread::wait_for_search_finished() {
std::unique_lock<Mutex> lk(mutex);
cv.wait(lk, [&]{ return !searching; });
}
/// Thread::idle_loop() is where the thread is parked, blocked on the
/// condition variable, when it has no work to do.
void Thread::idle_loop() {
// If OS already scheduled us on a different group than 0 then don't overwrite
// the choice, eventually we are one of many one-threaded processes running on
// some Windows NUMA hardware, for instance in fishtest. To make it simple,
// just check if running threads are below a threshold, in this case all this
// NUMA machinery is not needed.
if (Options["Threads"] > 8)
WinProcGroup::bindThisThread(idx);
while (true)
{
std::unique_lock<Mutex> lk(mutex);
searching = false;
cv.notify_one(); // Wake up anyone waiting for search finished
cv.wait(lk, [&]{ return searching; });
if (exit)
return;
lk.unlock();
search();
}
}
/// ThreadPool::set() creates/destroys threads to match the requested number.
/// Created and launched threads will go immediately to sleep in idle_loop.
/// Upon resizing, threads are recreated to allow for binding if necessary.
void ThreadPool::set(size_t requested) {
if (size() > 0) { // destroy any existing thread(s)
main()->wait_for_search_finished();
while (size() > 0)
delete back(), pop_back();
}
if (requested > 0) { // create new thread(s)
push_back(new MainThread(0));
while (size() < requested)
push_back(new Thread(size()));
clear();
}
// Reallocate the hash with the new threadpool size
TT.resize(Options["Hash"]);
}
/// ThreadPool::clear() sets threadPool data to initial values.
void ThreadPool::clear() {
for (Thread* th : *this)
th->clear();
main()->callsCnt = 0;
main()->previousScore = VALUE_INFINITE;
main()->previousTimeReduction = 1.0;
}
/// ThreadPool::start_thinking() wakes up main thread waiting in idle_loop() and
/// returns immediately. Main thread will wake up other threads and start the search.
void ThreadPool::start_thinking(Position& pos, StateListPtr& states,
const Search::LimitsType& limits, bool ponderMode) {
main()->wait_for_search_finished();
stopOnPonderhit = stop = false;
ponder = ponderMode;
Search::Limits = limits;
Search::RootMoves rootMoves;
for (const auto& m : MoveList<LEGAL>(pos))
if ( limits.searchmoves.empty()
|| std::count(limits.searchmoves.begin(), limits.searchmoves.end(), m))
rootMoves.emplace_back(m);
if (!rootMoves.empty())
Tablebases::rank_root_moves(pos, rootMoves);
// After ownership transfer 'states' becomes empty, so if we stop the search
// and call 'go' again without setting a new position states.get() == NULL.
assert(states.get() || setupStates.get());
if (states.get())
setupStates = std::move(states); // Ownership transfer, states is now empty
// We use Position::set() to set root position across threads. But there are
// some StateInfo fields (previous, pliesFromNull, capturedPiece) that cannot
// be deduced from a fen string, so set() clears them and to not lose the info
// we need to backup and later restore setupStates->back(). Note that setupStates
// is shared by threads but is accessed in read-only mode.
StateInfo tmp = setupStates->back();
for (Thread* th : *this)
{
th->nodes = th->tbHits = th->nmpMinPly = 0;
th->rootDepth = th->completedDepth = DEPTH_ZERO;
th->rootMoves = rootMoves;
th->rootPos.set(pos.fen(), pos.is_chess960(), &setupStates->back(), th);
}
setupStates->back() = tmp;
main()->start_searching();
}