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
#include "search.h"
#include "thread.h"
#include "uci.h"
-
-using namespace Search;
+#include "syzygy/tbprobe.h"
ThreadPool Threads; // Global object
-extern void check_time();
-
-namespace {
-
- // Helpers to launch a thread after creation and joining before delete. Must be
- // outside Thread c'tor and d'tor because the object must be fully initialized
- // when start_routine (and hence virtual idle_loop) is called and when joining.
-
- template<typename T> T* new_thread() {
- T* th = new T();
- th->nativeThread = std::thread(&ThreadBase::idle_loop, th); // Will go to sleep
- return th;
- }
+/// Thread constructor launches the thread and then waits until it goes to sleep
+/// in idle_loop().
- void delete_thread(ThreadBase* th) {
+Thread::Thread() {
- th->mutex.lock();
- th->exit = true; // Search must be already finished
- th->mutex.unlock();
-
- th->notify_one();
- th->nativeThread.join(); // Wait for thread termination
- delete th;
- }
+ resetCalls = exit = false;
+ maxPly = callsCnt = 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; });
}
-// ThreadBase::notify_one() wakes up the thread when there is some work to do
+/// Thread destructor waits for thread termination before returning
-void ThreadBase::notify_one() {
+Thread::~Thread() {
- std::unique_lock<std::mutex>(this->mutex);
+ mutex.lock();
+ exit = true;
sleepCondition.notify_one();
+ mutex.unlock();
+ nativeThread.join();
}
-// ThreadBase::wait_for() set the thread to sleep until 'condition' turns true
-
-void ThreadBase::wait_for(volatile const bool& condition) {
-
- std::unique_lock<std::mutex> lk(mutex);
- sleepCondition.wait(lk, [&]{ return condition; });
-}
-
-
-// Thread c'tor makes some init but does not launch any execution thread that
-// will be started only when c'tor returns.
-
-Thread::Thread() /* : splitPoints() */ { // Initialization of non POD broken in MSVC
-
- searching = false;
- maxPly = 0;
- splitPointsSize = 0;
- activeSplitPoint = nullptr;
- activePosition = nullptr;
- idx = Threads.size(); // Starts from 0
-}
-
-
-// Thread::cutoff_occurred() checks whether a beta cutoff has occurred in the
-// current active split point, or in some ancestor of the split point.
-
-bool Thread::cutoff_occurred() const {
-
- for (SplitPoint* sp = activeSplitPoint; sp; sp = sp->parentSplitPoint)
- if (sp->cutoff)
- return true;
-
- return false;
-}
-
-
-// Thread::available_to() checks whether the thread is available to help the
-// thread 'master' at a split point. An obvious requirement is that thread must
-// be idle. With more than two threads, this is not sufficient: If the thread is
-// the master of some split point, it is only available as a slave to the slaves
-// which are busy searching the split point at the top of slave's split point
-// stack (the "helpful master concept" in YBWC terminology).
-
-bool Thread::available_to(const Thread* master) const {
+/// Thread::wait_for_search_finished() waits on sleep condition
+/// until not searching
- if (searching)
- return false;
+void Thread::wait_for_search_finished() {
- // Make a local copy to be sure it doesn't become zero under our feet while
- // testing next condition and so leading to an out of bounds access.
- const size_t size = splitPointsSize;
-
- // No split points means that the thread is available as a slave for any
- // other thread otherwise apply the "helpful master" concept if possible.
- return !size || splitPoints[size - 1].slavesMask.test(master->idx);
+ std::unique_lock<Mutex> lk(mutex);
+ sleepCondition.wait(lk, [&]{ return !searching; });
}
-// Thread::split() does the actual work of distributing the work at a node between
-// several available threads. If it does not succeed in splitting the node
-// (because no idle threads are available), the function immediately returns.
-// If splitting is possible, a SplitPoint object is initialized with all the
-// data that must be copied to the helper threads and then helper threads are
-// informed that they have been assigned work. This will cause them to instantly
-// leave their idle loops and call search(). When all threads have returned from
-// search() then split() returns.
-
-void Thread::split(Position& pos, Stack* ss, Value alpha, Value beta, Value* bestValue,
- Move* bestMove, Depth depth, int moveCount,
- MovePicker* movePicker, int nodeType, bool cutNode) {
-
- assert(searching);
- assert(-VALUE_INFINITE < *bestValue && *bestValue <= alpha && alpha < beta && beta <= VALUE_INFINITE);
- assert(depth >= Threads.minimumSplitDepth);
- assert(splitPointsSize < MAX_SPLITPOINTS_PER_THREAD);
-
- // Pick and init the next available split point
- SplitPoint& sp = splitPoints[splitPointsSize];
-
- sp.master = this;
- sp.parentSplitPoint = activeSplitPoint;
- sp.slavesMask = 0, sp.slavesMask.set(idx);
- sp.depth = depth;
- sp.bestValue = *bestValue;
- sp.bestMove = *bestMove;
- sp.alpha = alpha;
- sp.beta = beta;
- sp.nodeType = nodeType;
- sp.cutNode = cutNode;
- sp.movePicker = movePicker;
- sp.moveCount = moveCount;
- sp.pos = &pos;
- sp.nodes = 0;
- sp.cutoff = false;
- sp.ss = ss;
-
- // Try to allocate available threads and ask them to start searching setting
- // 'searching' flag. This must be done under lock protection to avoid concurrent
- // allocation of the same slave by another master.
- Threads.spinlock.acquire();
- sp.spinlock.acquire();
-
- sp.allSlavesSearching = true; // Must be set under lock protection
- ++splitPointsSize;
- activeSplitPoint = &sp;
- activePosition = nullptr;
-
- Thread* slave;
-
- while ( sp.slavesMask.count() < MAX_SLAVES_PER_SPLITPOINT
- && (slave = Threads.available_slave(this)) != nullptr)
- {
- sp.slavesMask.set(slave->idx);
- slave->activeSplitPoint = &sp;
- slave->searching = true; // Slave leaves idle_loop()
- slave->notify_one(); // Could be sleeping
- }
-
- // Everything is set up. The master thread enters the idle loop, from which
- // it will instantly launch a search, because its 'searching' flag is set.
- // The thread will return from the idle loop when all slaves have finished
- // their work at this split point.
- sp.spinlock.release();
- Threads.spinlock.release();
-
- Thread::idle_loop(); // Force a call to base class idle_loop()
+/// Thread::wait() waits on sleep condition until condition is true
- // In the helpful master concept, a master can help only a sub-tree of its
- // split point and because everything is finished here, it's not possible
- // for the master to be booked.
- assert(!searching);
- assert(!activePosition);
+void Thread::wait(std::atomic_bool& condition) {
- // We have returned from the idle loop, which means that all threads are
- // finished. Note that setting 'searching' and decreasing splitPointsSize must
- // be done under lock protection to avoid a race with Thread::available_to().
- Threads.spinlock.acquire();
- sp.spinlock.acquire();
-
- searching = true;
- --splitPointsSize;
- activeSplitPoint = sp.parentSplitPoint;
- activePosition = &pos;
- pos.set_nodes_searched(pos.nodes_searched() + sp.nodes);
- *bestMove = sp.bestMove;
- *bestValue = sp.bestValue;
-
- sp.spinlock.release();
- Threads.spinlock.release();
+ std::unique_lock<Mutex> lk(mutex);
+ sleepCondition.wait(lk, [&]{ return bool(condition); });
}
-// TimerThread::idle_loop() is where the timer thread waits Resolution milliseconds
-// and then calls check_time(). When not searching, thread sleeps until it's woken up.
+/// Thread::start_searching() wakes up the thread that will start the search
-void TimerThread::idle_loop() {
+void Thread::start_searching(bool resume) {
- while (!exit)
- {
- std::unique_lock<std::mutex> lk(mutex);
+ std::unique_lock<Mutex> lk(mutex);
- if (!exit)
- sleepCondition.wait_for(lk, std::chrono::milliseconds(run ? Resolution : INT_MAX));
-
- lk.unlock();
+ if (!resume)
+ searching = true;
- if (run)
- check_time();
- }
+ sleepCondition.notify_one();
}
-// MainThread::idle_loop() is where the main thread is parked waiting to be started
-// when there is a new search. The main thread will launch all the slave threads.
+/// Thread::idle_loop() is where the thread is parked when it has no work to do
-void MainThread::idle_loop() {
+void Thread::idle_loop() {
while (!exit)
{
- std::unique_lock<std::mutex> lk(mutex);
+ std::unique_lock<Mutex> lk(mutex);
- thinking = false;
+ searching = false;
- while (!thinking && !exit)
+ while (!searching && !exit)
{
- Threads.sleepCondition.notify_one(); // Wake up the UI thread if needed
+ sleepCondition.notify_one(); // Wake up any waiting thread
sleepCondition.wait(lk);
}
lk.unlock();
if (!exit)
- {
- searching = true;
-
- Search::think();
-
- assert(searching);
-
- searching = false;
- }
+ search();
}
}
-// ThreadPool::init() is called at startup to create and launch requested threads,
-// that will go immediately to sleep. We cannot use a c'tor because Threads is a
-// static object and we need a fully initialized engine at this point due to
-// allocation of Endgames in Thread c'tor.
+/// 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() {
- timer = new_thread<TimerThread>();
- push_back(new_thread<MainThread>());
+ push_back(new MainThread);
read_uci_options();
}
-// ThreadPool::exit() terminates the threads before the program exits. Cannot be
-// done in d'tor because threads must be terminated before freeing us.
+/// 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() {
- delete_thread(timer); // As first because check_time() accesses threads data
-
- for (Thread* th : *this)
- delete_thread(th);
+ 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 the requested
-// number. Thread objects are dynamically allocated to avoid creating all possible
-// threads in advance (which include pawns and material tables), even if only a
-// few are to be used.
+/// 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() {
- minimumSplitDepth = Options["Min Split Depth"] * ONE_PLY;
- size_t requested = Options["Threads"];
+ size_t requested = Options["Threads"];
assert(requested > 0);
- // If zero (default) then set best minimum split depth automatically
- if (!minimumSplitDepth)
- minimumSplitDepth = requested < 8 ? 4 * ONE_PLY : 7 * ONE_PLY;
-
while (size() < requested)
- push_back(new_thread<Thread>());
+ push_back(new Thread);
while (size() > requested)
- {
- delete_thread(back());
- pop_back();
- }
+ delete back(), pop_back();
}
-// ThreadPool::available_slave() tries to find an idle thread which is available
-// as a slave for the thread 'master'.
+/// ThreadPool::nodes_searched() returns the number of nodes searched
-Thread* ThreadPool::available_slave(const Thread* master) const {
+int64_t ThreadPool::nodes_searched() {
+ int64_t nodes = 0;
for (Thread* th : *this)
- if (th->available_to(master))
- return th;
-
- return nullptr;
+ nodes += th->rootPos.nodes_searched();
+ return nodes;
}
-// ThreadPool::wait_for_think_finished() waits for main thread to finish the search
+/// ThreadPool::start_thinking() wakes up the main thread sleeping in idle_loop()
+/// and starts a new search, then returns immediately.
-void ThreadPool::wait_for_think_finished() {
+void ThreadPool::start_thinking(Position& pos, StateListPtr& states,
+ const Search::LimitsType& limits) {
- std::unique_lock<std::mutex> lk(main()->mutex);
- sleepCondition.wait(lk, [&]{ return !main()->thinking; });
-}
+ main()->wait_for_search_finished();
+ Search::Signals.stopOnPonderhit = Search::Signals.stop = false;
+ Search::Limits = limits;
+ Search::RootMoves rootMoves;
-// ThreadPool::start_thinking() wakes up the main thread sleeping in
-// MainThread::idle_loop() and starts a new search, then returns immediately.
+ 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);
-void ThreadPool::start_thinking(const Position& pos, const LimitsType& limits,
- StateStackPtr& states) {
- wait_for_think_finished();
+ // 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());
- SearchTime = now(); // As early as possible
+ if (states.get())
+ setupStates = std::move(states); // Ownership transfer, states is now empty
- Signals.stopOnPonderhit = Signals.firstRootMove = false;
- Signals.stop = Signals.failedLowAtRoot = false;
+ StateInfo tmp = setupStates->back();
- RootMoves.clear();
- RootPos = pos;
- Limits = limits;
- if (states.get()) // If we don't set a new position, preserve current state
+ for (Thread* th : Threads)
{
- SetupStates = std::move(states); // Ownership transfer here
- assert(!states.get());
+ th->maxPly = 0;
+ th->rootDepth = DEPTH_ZERO;
+ th->rootMoves = rootMoves;
+ th->rootPos.set(pos.fen(), pos.is_chess960(), &setupStates->back(), th);
}
- for (const auto& m : MoveList<LEGAL>(pos))
- if ( limits.searchmoves.empty()
- || std::count(limits.searchmoves.begin(), limits.searchmoves.end(), m))
- RootMoves.push_back(RootMove(m));
+ setupStates->back() = tmp; // Restore st->previous, cleared by Position::set()
- main()->thinking = true;
- main()->notify_one(); // Starts main thread
+ main()->start_searching();
}
projects / stockfish / blobdiff