/*
Stockfish, a UCI chess playing engine derived from Glaurung 2.1
Copyright (C) 2004-2008 Tord Romstad (Glaurung author)
- Copyright (C) 2008-2012 Marco Costalba, Joona Kiiski, Tord Romstad
+ Copyright (C) 2008-2016 Marco Costalba, Joona Kiiski, 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
along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
+#include <algorithm> // For std::count
#include <cassert>
-#include <iostream>
#include "movegen.h"
#include "search.h"
#include "thread.h"
-#include "ucioption.h"
+#include "uci.h"
using namespace Search;
ThreadPool Threads; // Global object
-namespace { extern "C" {
+/// Thread constructor launch the thread and then wait until it goes to sleep
+/// in idle_loop().
- // start_routine() is the C function which is called when a new thread
- // is launched. It is a wrapper to the virtual function idle_loop().
+Thread::Thread() {
- long start_routine(Thread* th) { th->idle_loop(); return 0; }
+ resetCalls = exit = false;
+ maxPly = callsCnt = 0;
+ history.clear();
+ counterMoves.clear();
+ idx = Threads.size(); // Start from 0
-} }
-
-
-// Thread c'tor starts a newly-created thread of execution that will call
-// the the virtual function idle_loop(), going immediately to sleep.
-
-Thread::Thread() : splitPoints() {
-
- searching = exit = false;
- maxPly = splitPointsCnt = 0;
- curSplitPoint = NULL;
- idx = Threads.size();
-
- if (!thread_create(handle, start_routine, this))
- {
- std::cerr << "Failed to create thread number " << idx << std::endl;
- ::exit(EXIT_FAILURE);
- }
+ std::unique_lock<Mutex> lk(mutex);
+ searching = true;
+ nativeThread = std::thread(&Thread::idle_loop, this);
+ sleepCondition.wait(lk, [&]{ return !searching; });
}
-// Thread d'tor waits for thread termination before to return
+/// Thread destructor wait for thread termination before returning
Thread::~Thread() {
- exit = true; // Search must be already finished
- notify_one();
- thread_join(handle); // Wait for thread termination
+ mutex.lock();
+ exit = true;
+ sleepCondition.notify_one();
+ mutex.unlock();
+ nativeThread.join();
}
-// TimerThread::idle_loop() is where the timer thread waits msec milliseconds
-// and then calls check_time(). If msec is 0 thread sleeps until is woken up.
-extern void check_time();
+/// Thread::wait_for_search_finished() wait on sleep condition until not searching
-void TimerThread::idle_loop() {
+void Thread::wait_for_search_finished() {
- while (!exit)
- {
- mutex.lock();
-
- if (!exit)
- sleepCondition.wait_for(mutex, msec ? msec : INT_MAX);
-
- mutex.unlock();
-
- if (msec)
- check_time();
- }
+ std::unique_lock<Mutex> lk(mutex);
+ sleepCondition.wait(lk, [&]{ return !searching; });
}
-// MainThread::idle_loop() is where the main thread is parked waiting to be started
-// when there is a new search. Main thread will launch all the slave threads.
+/// Thread::wait() wait on sleep condition until condition is true
-void MainThread::idle_loop() {
+void Thread::wait(std::atomic_bool& condition) {
- while (true)
- {
- mutex.lock();
+ std::unique_lock<Mutex> lk(mutex);
+ sleepCondition.wait(lk, [&]{ return bool(condition); });
+}
- thinking = false;
- while (!thinking && !exit)
- {
- Threads.sleepCondition.notify_one(); // Wake up UI thread if needed
- sleepCondition.wait(mutex);
- }
+/// Thread::start_searching() wake up the thread that will start the search
- mutex.unlock();
+void Thread::start_searching(bool resume) {
- if (exit)
- return;
+ std::unique_lock<Mutex> lk(mutex);
+ if (!resume)
searching = true;
- Search::think();
-
- assert(searching);
-
- searching = false;
- }
-}
-
-
-// Thread::notify_one() wakes up the thread when there is some search to do
-
-void Thread::notify_one() {
-
- mutex.lock();
sleepCondition.notify_one();
- mutex.unlock();
}
-// Thread::wait_for() set the thread to sleep until condition 'b' turns true
+/// Thread::idle_loop() is where the thread is parked when it has no work to do
-void Thread::wait_for(volatile const bool& b) {
-
- mutex.lock();
- while (!b) sleepCondition.wait(mutex);
- mutex.unlock();
-}
-
-
-// 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 = curSplitPoint; sp; sp = sp->parent)
- if (sp->cutoff)
- return true;
-
- return false;
-}
+void Thread::idle_loop() {
+ while (!exit)
+ {
+ std::unique_lock<Mutex> lk(mutex);
-// Thread::is_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 active split point, it is only available as a slave to the
-// slaves which are busy searching the split point at the top of slaves split
-// point stack (the "helpful master concept" in YBWC terminology).
-
-bool Thread::is_available_to(Thread* master) const {
+ searching = false;
- if (searching)
- return false;
+ while (!searching && !exit)
+ {
+ sleepCondition.notify_one(); // Wake up any waiting thread
+ sleepCondition.wait(lk);
+ }
- // Make a local copy to be sure doesn't become zero under our feet while
- // testing next condition and so leading to an out of bound access.
- int spCnt = splitPointsCnt;
+ lk.unlock();
- // No active split points means that the thread is available as a slave for any
- // other thread otherwise apply the "helpful master" concept if possible.
- return !spCnt || (splitPoints[spCnt - 1].slavesMask & (1ULL << master->idx));
+ if (!exit)
+ search();
+ }
}
-// init() is called at startup. Initializes lock and condition variable and
-// launches requested threads sending them immediately to sleep. We cannot use
-// a c'tor becuase 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() create and launch 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() {
- sleepWhileIdle = true;
- timer = new TimerThread();
- threads.push_back(new MainThread());
+ push_back(new MainThread);
read_uci_options();
}
-// exit() cleanly terminates the threads before the program exits.
+/// ThreadPool::exit() terminate threads before the program exits. Cannot be
+/// done in destructor because threads must be terminated before deleting any
+/// static objects, so while still in main().
void ThreadPool::exit() {
- delete timer; // As first becuase check_time() accesses threads data
-
- for (size_t i = 0; i < threads.size(); i++)
- delete threads[i];
+ while (size())
+ delete back(), pop_back();
}
-// 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 in advance all possible
-// threads, with included pawns and material tables, if only few are 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() {
- maxThreadsPerSplitPoint = Options["Max Threads per Split Point"];
- minimumSplitDepth = Options["Min Split Depth"] * ONE_PLY;
- size_t requested = Options["Threads"];
+ size_t requested = Options["Threads"];
assert(requested > 0);
- while (threads.size() < requested)
- threads.push_back(new Thread());
+ while (size() < requested)
+ push_back(new Thread);
- while (threads.size() > requested)
- {
- delete threads.back();
- threads.pop_back();
- }
+ while (size() > requested)
+ delete back(), pop_back();
}
-// available_slave_exists() tries to find an idle thread which is available as
-// a slave for the thread 'master'.
+/// ThreadPool::nodes_searched() return the number of nodes searched
-bool ThreadPool::available_slave_exists(Thread* master) const {
+int64_t ThreadPool::nodes_searched() {
- for (size_t i = 0; i < threads.size(); i++)
- if (threads[i]->is_available_to(master))
- return true;
-
- return false;
+ int64_t nodes = 0;
+ for (Thread* th : *this)
+ nodes += th->rootPos.nodes_searched();
+ return nodes;
}
-// 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, or because we have no unused split
-// point objects), 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 told 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.
-
-template <bool Fake>
-Value ThreadPool::split(Position& pos, Stack* ss, Value alpha, Value beta,
- Value bestValue, Move* bestMove, Depth depth, Move threatMove,
- int moveCount, MovePicker& mp, int nodeType) {
-
- assert(pos.pos_is_ok());
- assert(bestValue > -VALUE_INFINITE);
- assert(bestValue <= alpha);
- assert(alpha < beta);
- assert(beta <= VALUE_INFINITE);
- assert(depth > DEPTH_ZERO);
-
- Thread* master = pos.this_thread();
-
- if (master->splitPointsCnt >= MAX_SPLITPOINTS_PER_THREAD)
- return bestValue;
-
- // Pick the next available split point from the split point stack
- SplitPoint& sp = master->splitPoints[master->splitPointsCnt];
-
- sp.parent = master->curSplitPoint;
- sp.master = master;
- sp.cutoff = false;
- sp.slavesMask = 1ULL << master->idx;
- sp.depth = depth;
- sp.bestMove = *bestMove;
- sp.threatMove = threatMove;
- sp.alpha = alpha;
- sp.beta = beta;
- sp.nodeType = nodeType;
- sp.bestValue = bestValue;
- sp.mp = ∓
- sp.moveCount = moveCount;
- sp.pos = &pos;
- sp.nodes = 0;
- sp.ss = ss;
-
- assert(master->searching);
-
- master->curSplitPoint = &sp;
- int slavesCnt = 0;
-
- // Try to allocate available threads and ask them to start searching setting
- // is_searching flag. This must be done under lock protection to avoid concurrent
- // allocation of the same slave by another master.
- mutex.lock();
- sp.mutex.lock();
-
- for (size_t i = 0; i < threads.size() && !Fake; ++i)
- if (threads[i]->is_available_to(master))
- {
- sp.slavesMask |= 1ULL << i;
- threads[i]->curSplitPoint = &sp;
- threads[i]->searching = true; // Slave leaves idle_loop()
- threads[i]->notify_one(); // Could be sleeping
-
- if (++slavesCnt + 1 >= maxThreadsPerSplitPoint) // Master is always included
- break;
- }
-
- master->splitPointsCnt++;
-
- sp.mutex.unlock();
- mutex.unlock();
-
- // Everything is set up. The master thread enters the idle loop, from which
- // it will instantly launch a search, because its is_searching flag is set.
- // The thread will return from the idle loop when all slaves have finished
- // their work at this split point.
- if (slavesCnt || Fake)
- {
- master->Thread::idle_loop(); // Force a call to base class idle_loop()
-
- // In helpful master concept a master can help only a sub-tree of its split
- // point, and because here is all finished is not possible master is booked.
- assert(!master->searching);
- }
-
- // We have returned from the idle loop, which means that all threads are
- // finished. Note that setting is_searching and decreasing splitPointsCnt is
- // done under lock protection to avoid a race with Thread::is_available_to().
- mutex.lock();
- sp.mutex.lock();
-
- master->searching = true;
- master->splitPointsCnt--;
- master->curSplitPoint = sp.parent;
- pos.set_nodes_searched(pos.nodes_searched() + sp.nodes);
- *bestMove = sp.bestMove;
-
- sp.mutex.unlock();
- mutex.unlock();
-
- return sp.bestValue;
-}
-
-// Explicit template instantiations
-template Value ThreadPool::split<false>(Position&, Stack*, Value, Value, Value, Move*, Depth, Move, int, MovePicker&, int);
-template Value ThreadPool::split<true>(Position&, Stack*, Value, Value, Value, Move*, Depth, Move, int, MovePicker&, int);
-
-
-// wait_for_think_finished() waits for main thread to go to sleep then returns
-
-void ThreadPool::wait_for_think_finished() {
-
- MainThread* t = main_thread();
- t->mutex.lock();
- while (t->thinking) sleepCondition.wait(t->mutex);
- t->mutex.unlock();
-}
-
-
-// start_thinking() wakes up the main thread sleeping in main_loop() so to start
-// a new search, then returns immediately.
+/// ThreadPool::start_thinking() wake up the main thread sleeping in idle_loop()
+/// and start a new search, then return immediately.
void ThreadPool::start_thinking(const Position& pos, const LimitsType& limits,
- const std::vector<Move>& searchMoves, StateStackPtr& states) {
- wait_for_think_finished();
+ StateStackPtr& states) {
- SearchTime = Time::now(); // As early as possible
+ main()->wait_for_search_finished();
- Signals.stopOnPonderhit = Signals.firstRootMove = false;
- Signals.stop = Signals.failedLowAtRoot = false;
+ Signals.stopOnPonderhit = Signals.stop = false;
- RootPos = pos;
+ main()->rootMoves.clear();
+ main()->rootPos = pos;
Limits = limits;
- SetupStates = states; // Ownership transfer here
- RootMoves.clear();
+ if (states.get()) // If we don't set a new position, preserve current state
+ {
+ SetupStates = std::move(states); // Ownership transfer here
+ assert(!states.get());
+ }
- for (MoveList<LEGAL> ml(pos); !ml.end(); ++ml)
- if (searchMoves.empty() || count(searchMoves.begin(), searchMoves.end(), ml.move()))
- RootMoves.push_back(RootMove(ml.move()));
+ for (const auto& m : MoveList<LEGAL>(pos))
+ if ( limits.searchmoves.empty()
+ || std::count(limits.searchmoves.begin(), limits.searchmoves.end(), m))
+ main()->rootMoves.push_back(RootMove(m));
- main_thread()->thinking = true;
- main_thread()->notify_one(); // Starts main thread
+ main()->start_searching();
}