/*
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) 2015-2016 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"
ThreadPool Threads; // Global object
/// Thread constructor launches the thread and then waits until it goes to sleep
/// in idle_loop().
Thread::Thread() {
resetCalls = exit = false;
maxPly = callsCnt = 0;
tbHits = 0;
history.clear();
counterMoves.clear();
idx = Threads.size(); // Start from 0
std::unique_lock<Mutex> lk(mutex);
searching = true;
nativeThread = std::thread(&Thread::idle_loop, this);
sleepCondition.wait(lk, [&]{ return !searching; });
}
/// Thread destructor waits for thread termination before returning
Thread::~Thread() {
mutex.lock();
exit = true;
sleepCondition.notify_one();
mutex.unlock();
nativeThread.join();
}
/// Thread::wait_for_search_finished() waits on sleep condition
/// until not searching
void Thread::wait_for_search_finished() {
std::unique_lock<Mutex> lk(mutex);
sleepCondition.wait(lk, [&]{ return !searching; });
}
/// Thread::wait() waits on sleep condition until condition is true
void Thread::wait(std::atomic_bool& condition) {
std::unique_lock<Mutex> lk(mutex);
sleepCondition.wait(lk, [&]{ return bool(condition); });
}
/// Thread::start_searching() wakes up the thread that will start the search
void Thread::start_searching(bool resume) {
std::unique_lock<Mutex> lk(mutex);
if (!resume)
searching = true;
sleepCondition.notify_one();
}
/// Thread::idle_loop() is where the thread is parked when it has no work to do
void Thread::idle_loop() {
while (!exit)
{
std::unique_lock<Mutex> lk(mutex);
searching = false;
while (!searching && !exit)
{
sleepCondition.notify_one(); // Wake up any waiting thread
sleepCondition.wait(lk);
}
lk.unlock();
if (!exit)
search();
}
}
/// ThreadPool::init() creates and launches requested threads that will go
/// immediately to sleep. We cannot use a constructor because Threads is a
/// static object and we need a fully initialized engine at this point due to
/// allocation of Endgames in the Thread constructor.
void ThreadPool::init() {
push_back(new MainThread);
read_uci_options();
}
/// ThreadPool::exit() terminates threads before the program exits. Cannot be
/// done in destructor because threads must be terminated before deleting any
/// static objects while still in main().
void ThreadPool::exit() {
while (size())
delete back(), pop_back();
}
/// ThreadPool::read_uci_options() updates internal threads parameters from the
/// corresponding UCI options and creates/destroys threads to match requested
/// number. Thread objects are dynamically allocated.
void ThreadPool::read_uci_options() {
size_t requested = Options["Threads"];
assert(requested > 0);
while (size() < requested)
push_back(new Thread);
while (size() > requested)
delete back(), pop_back();
}
/// ThreadPool::nodes_searched() returns the number of nodes searched
uint64_t ThreadPool::nodes_searched() const {
uint64_t nodes = 0;
for (Thread* th : *this)
nodes += th->rootPos.nodes_searched();
return nodes;
}
/// ThreadPool::tb_hits() returns the number of TB hits
uint64_t ThreadPool::tb_hits() const {
uint64_t hits = 0;
for (Thread* th : *this)
hits += th->tbHits;
return hits;
}
/// ThreadPool::start_thinking() wakes up the main thread sleeping in idle_loop()
/// and starts a new search, then returns immediately.
void ThreadPool::start_thinking(Position& pos, StateListPtr& states,
const Search::LimitsType& limits) {
main()->wait_for_search_finished();
Search::Signals.stopOnPonderhit = Search::Signals.stop = false;
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.push_back(Search::RootMove(m));
if (!rootMoves.empty())
Tablebases::filter_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
StateInfo tmp = setupStates->back();
for (Thread* th : Threads)
{
th->maxPly = 0;
th->tbHits = 0;
th->rootDepth = DEPTH_ZERO;
th->rootMoves = rootMoves;
th->rootPos.set(pos.fen(), pos.is_chess960(), &setupStates->back(), th);
}
setupStates->back() = tmp; // Restore st->previous, cleared by Position::set()
main()->start_searching();
}