/*
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) 2008-2015 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
#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" {
-
- // 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().
+extern void check_time();
- long start_routine(Thread* th) { th->idle_loop(); return 0; }
+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() {
+ std::thread* th = new T;
+ *th = std::thread(&T::idle_loop, (T*)th); // Will go to sleep
+ return (T*)th;
+ }
-// Thread c'tor starts a newly-created thread of execution that will call
-// the the virtual function idle_loop(), going immediately to sleep.
+ void delete_thread(ThreadBase* th) {
-Thread::Thread() : splitPoints() {
+ th->mutex.lock();
+ th->exit = true; // Search must be already finished
+ th->mutex.unlock();
- searching = exit = false;
- maxPly = splitPointsSize = 0;
- activeSplitPoint = NULL;
- idx = Threads.size();
+ th->notify_one();
+ th->join(); // Wait for thread termination
+ delete th;
+ }
- if (!thread_create(handle, start_routine, this))
- {
- std::cerr << "Failed to create thread number " << idx << std::endl;
- ::exit(EXIT_FAILURE);
- }
}
-// Thread d'tor waits for thread termination before to return
+// ThreadBase::notify_one() wakes up the thread when there is some work to do
-Thread::~Thread() {
+void ThreadBase::notify_one() {
- exit = true; // Search must be already finished
- notify_one();
- thread_join(handle); // Wait for thread termination
+ std::unique_lock<Mutex> lk(mutex);
+ sleepCondition.notify_one();
}
-// 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();
+// ThreadBase::wait() set the thread to sleep until 'condition' turns true
-void TimerThread::idle_loop() {
+void ThreadBase::wait(std::atomic<bool>& condition) {
- while (!exit)
- {
- mutex.lock();
+ std::unique_lock<Mutex> lk(mutex);
+ sleepCondition.wait(lk, [&]{ return bool(condition); });
+}
- if (!exit)
- sleepCondition.wait_for(mutex, msec ? msec : INT_MAX);
- mutex.unlock();
+// ThreadBase::wait_while() set the thread to sleep until 'condition' turns false
+void ThreadBase::wait_while(std::atomic<bool>& condition) {
- if (msec)
- check_time();
- }
+ std::unique_lock<Mutex> lk(mutex);
+ sleepCondition.wait(lk, [&]{ return !condition; });
}
-// 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.
-
-void MainThread::idle_loop() {
+// Thread c'tor makes some init but does not launch any execution thread that
+// will be started only when c'tor returns.
- while (true)
- {
- mutex.lock();
+Thread::Thread() {
- thinking = false;
+ searching = false;
+ maxPly = 0;
+ history.clear();
+ counterMoves.clear();
+ idx = Threads.size(); // Starts from 0
+}
- while (!thinking && !exit)
- {
- Threads.sleepCondition.notify_one(); // Wake up UI thread if needed
- sleepCondition.wait(mutex);
- }
- mutex.unlock();
+// 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.
- if (exit)
- return;
+void TimerThread::idle_loop() {
- searching = true;
+ while (!exit)
+ {
+ std::unique_lock<Mutex> lk(mutex);
- Search::think();
+ if (!exit)
+ sleepCondition.wait_for(lk, std::chrono::milliseconds(run ? Resolution : INT_MAX));
- assert(searching);
+ lk.unlock();
- searching = false;
+ if (!exit && run)
+ check_time();
}
}
-// Thread::notify_one() wakes up the thread when there is some search to do
-
-void Thread::notify_one() {
+// Thread::idle_loop() is where the thread is parked when it has no work to do
- mutex.lock();
- sleepCondition.notify_one();
- mutex.unlock();
-}
+void Thread::idle_loop() {
+ while (!exit)
+ {
+ std::unique_lock<Mutex> lk(mutex);
-// Thread::wait_for() set the thread to sleep until condition 'b' turns true
+ while (!searching && !exit)
+ sleepCondition.wait(lk);
-void Thread::wait_for(volatile const bool& b) {
+ lk.unlock();
- mutex.lock();
- while (!b) sleepCondition.wait(mutex);
- mutex.unlock();
+ if (!exit && searching)
+ search();
+ }
}
-// Thread::cutoff_occurred() checks whether a beta cutoff has occurred in the
-// current active split point, or in some ancestor of the split point.
+// 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.
+
+void MainThread::idle_loop() {
-bool Thread::cutoff_occurred() const {
+ while (!exit)
+ {
+ std::unique_lock<Mutex> lk(mutex);
- for (SplitPoint* sp = activeSplitPoint; sp; sp = sp->parentSplitPoint)
- if (sp->cutoff)
- return true;
+ thinking = false;
- return false;
-}
+ while (!thinking && !exit)
+ {
+ sleepCondition.notify_one(); // Wake up the UI thread if needed
+ sleepCondition.wait(lk);
+ }
+ lk.unlock();
-// 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 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).
+ if (!exit)
+ think();
+ }
+}
-bool Thread::is_available_to(Thread* master) const {
- if (searching)
- return false;
+// MainThread::join() waits for main thread to finish thinking
- // 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 size = splitPointsSize;
+void MainThread::join() {
- // 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 & (1ULL << master->idx));
+ std::unique_lock<Mutex> lk(mutex);
+ sleepCondition.wait(lk, [&]{ return !thinking; });
}
-// init() is called at startup to create and launch requested threads, that will
-// go immediately to sleep due to 'sleepWhileIdle' set to true. 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() 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.
void ThreadPool::init() {
- sleepWhileIdle = true;
- timer = new TimerThread();
- push_back(new MainThread());
+ timer = new_thread<TimerThread>();
+ push_back(new_thread<MainThread>());
read_uci_options();
}
-// exit() cleanly terminates the threads before the program exits
+// ThreadPool::exit() terminates the threads before the program exits. Cannot be
+// done in d'tor because threads must be terminated before freeing us.
void ThreadPool::exit() {
- delete timer; // As first because check_time() accesses threads data
+ delete_thread(timer); // As first because check_time() accesses threads data
+ timer = nullptr;
+
+ for (Thread* th : *this)
+ delete_thread(th);
- for (iterator it = begin(); it != end(); ++it)
- delete *it;
+ clear(); // Get rid of stale pointers
}
-// 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 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.
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 (size() < requested)
- push_back(new Thread());
+ push_back(new_thread<Thread>());
while (size() > requested)
{
- delete back();
+ delete_thread(back());
pop_back();
}
}
-// slave_available() tries to find an idle thread which is available as a slave
-// for the thread 'master'.
-
-Thread* ThreadPool::available_slave(Thread* master) const {
-
- for (const_iterator it = begin(); it != end(); ++it)
- if ((*it)->is_available_to(master))
- return *it;
-
- return NULL;
-}
-
-
-// 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
-// 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>
-void Thread::split(Position& pos, Stack* ss, Value alpha, Value beta, Value* bestValue,
- Move* bestMove, Depth depth, Move threatMove, int moveCount,
- MovePicker* movePicker, int nodeType) {
-
- assert(pos.pos_is_ok());
- assert(*bestValue <= alpha && alpha < beta && beta <= VALUE_INFINITE);
- assert(*bestValue > -VALUE_INFINITE);
- assert(depth >= Threads.minimumSplitDepth);
- assert(searching);
- assert(splitPointsSize < MAX_SPLITPOINTS_PER_THREAD);
-
- // Pick the next available split point from the split point stack
- SplitPoint& sp = splitPoints[splitPointsSize];
-
- sp.masterThread = this;
- sp.parentSplitPoint = activeSplitPoint;
- sp.slavesMask = 1ULL << idx;
- sp.depth = depth;
- sp.bestValue = *bestValue;
- sp.bestMove = *bestMove;
- sp.threatMove = threatMove;
- sp.alpha = alpha;
- sp.beta = beta;
- sp.nodeType = nodeType;
- 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.mutex.lock();
- sp.mutex.lock();
-
- splitPointsSize++;
- activeSplitPoint = &sp;
-
- size_t slavesCnt = 1; // This thread is always included
- Thread* slave;
-
- while ( (slave = Threads.available_slave(this)) != NULL
- && ++slavesCnt <= Threads.maxThreadsPerSplitPoint && !Fake)
- {
- sp.slavesMask |= 1ULL << slave->idx;
- slave->activeSplitPoint = &sp;
- slave->searching = true; // Slave leaves idle_loop()
- slave->notify_one(); // Could be sleeping
- }
-
- sp.mutex.unlock();
- Threads.mutex.unlock();
-
- // 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.
- if (slavesCnt > 1 || Fake)
- {
- 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(!searching);
- }
-
- // We have returned from the idle loop, which means that all threads are
- // finished. Note that setting 'searching' and decreasing splitPointsSize is
- // done under lock protection to avoid a race with Thread::is_available_to().
- Threads.mutex.lock();
- sp.mutex.lock();
-
- searching = true;
- splitPointsSize--;
- activeSplitPoint = sp.parentSplitPoint;
- pos.set_nodes_searched(pos.nodes_searched() + sp.nodes);
- *bestMove = sp.bestMove;
- *bestValue = sp.bestValue;
-
- sp.mutex.unlock();
- Threads.mutex.unlock();
-}
-
-// Explicit template instantiations
-template void Thread::split<false>(Position&, Stack*, Value, Value, Value*, Move*, Depth, Move, int, MovePicker*, int);
-template void Thread::split< true>(Position&, Stack*, Value, Value, Value*, Move*, Depth, Move, int, MovePicker*, int);
-
+// ThreadPool::nodes_searched() returns the number of nodes searched
-// wait_for_think_finished() waits for main thread to go to sleep then returns
+int64_t ThreadPool::nodes_searched() {
-void ThreadPool::wait_for_think_finished() {
-
- MainThread* t = main_thread();
- t->mutex.lock();
- while (t->thinking) sleepCondition.wait(t->mutex);
- t->mutex.unlock();
+ int64_t nodes = 0;
+ for (Thread *th : *this)
+ nodes += th->rootPos.nodes_searched();
+ return nodes;
}
-// start_thinking() wakes up the main thread sleeping in MainThread::idle_loop()
-// so to start a new search, then returns immediately.
+// ThreadPool::start_thinking() wakes up the main thread sleeping in
+// MainThread::idle_loop() and starts a new search, then returns immediately.
void ThreadPool::start_thinking(const Position& pos, const LimitsType& limits,
- const std::vector<Move>& searchMoves, StateStackPtr& states) {
- wait_for_think_finished();
-
- SearchTime = Time::now(); // As early as possible
+ StateStackPtr& states) {
+ main()->join();
Signals.stopOnPonderhit = Signals.firstRootMove = false;
Signals.stop = Signals.failedLowAtRoot = 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()
- || std::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()->thinking = true;
+ main()->notify_one(); // Wake up main thread: 'thinking' must be already set
}
projects / stockfish / blobdiff