/*
Stockfish, a UCI chess playing engine derived from Glaurung 2.1
Copyright (C) 2004-2008 Tord Romstad (Glaurung author)
- Copyright (C) 2008-2010 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
along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
-#include <iostream>
+#include <algorithm> // For std::count
+#include <cassert>
+#include "movegen.h"
+#include "search.h"
#include "thread.h"
-#include "ucioption.h"
+#include "uci.h"
-ThreadsManager Threads; // Global object definition
+using namespace Search;
-namespace { extern "C" {
+ThreadPool Threads; // Global object
- // start_routine() is the C function which is called when a new thread
- // is launched. It simply calls idle_loop() with the supplied threadID.
- // There are two versions of this function; one for POSIX threads and
- // one for Windows threads.
+// Thread constructor makes some init and launches the thread that will go to
+// sleep in idle_loop().
-#if defined(_MSC_VER)
+Thread::Thread() {
- DWORD WINAPI start_routine(LPVOID threadID) {
-
- Threads.idle_loop(*(int*)threadID, NULL);
- return 0;
- }
-
-#else
-
- void* start_routine(void* threadID) {
-
- Threads.idle_loop(*(int*)threadID, NULL);
- return NULL;
- }
-
-#endif
+ searching = true; // Avoid a race with start_thinking()
+ exit = resetCalls = false;
+ maxPly = callsCnt = 0;
+ history.clear();
+ counterMoves.clear();
+ idx = Threads.size(); // Starts from 0
+ std::thread::operator=(std::thread(&Thread::idle_loop, this));
+}
-} }
+// Thread destructor waits for thread termination before deleting
-// wake_up() wakes up the thread, normally at the beginning of the search or,
-// if "sleeping threads" is used, when there is some work to do.
+Thread::~Thread() {
-void Thread::wake_up() {
+ mutex.lock();
+ exit = true; // Search must be already finished
+ mutex.unlock();
- lock_grab(&sleepLock);
- cond_signal(&sleepCond);
- lock_release(&sleepLock);
+ notify_one();
+ std::thread::join(); // Wait for thread termination
}
-// cutoff_occurred() checks whether a beta cutoff has occurred in
-// the thread's currently active split point, or in some ancestor of
-// the current split point.
-
-bool Thread::cutoff_occurred() const {
+// Thread::join() waits for the thread to finish searching
+void Thread::join() {
- for (SplitPoint* sp = splitPoint; sp; sp = sp->parent)
- if (sp->is_betaCutoff)
- return true;
- return false;
+ std::unique_lock<Mutex> lk(mutex);
+ sleepCondition.wait(lk, [&]{ return !searching; });
}
-// is_available_to() checks whether the thread is available to help the thread with
-// threadID "master" at a split point. An obvious requirement is that thread must be
-// idle. With more than two threads, this is not by itself sufficient: If the thread
-// is the master of some active split point, it is only available as a slave to the
-// threads 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::is_available_to(int master) const {
-
- if (state != AVAILABLE)
- return false;
+// Thread::notify_one() wakes up the thread when there is some work to do
- // 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 localActiveSplitPoints = activeSplitPoints;
+void Thread::notify_one() {
- // 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.
- if ( !localActiveSplitPoints
- || splitPoints[localActiveSplitPoints - 1].is_slave[master])
- return true;
-
- return false;
+ std::unique_lock<Mutex> lk(mutex);
+ sleepCondition.notify_one();
}
-// read_uci_options() updates number of active threads and other internal
-// parameters according to the UCI options values. It is called before
-// to start a new search.
+// Thread::wait() set the thread to sleep until 'condition' turns true
-void ThreadsManager::read_uci_options() {
+void Thread::wait(std::atomic_bool& condition) {
- maxThreadsPerSplitPoint = Options["Maximum Number of Threads per Split Point"].value<int>();
- minimumSplitDepth = Options["Minimum Split Depth"].value<int>() * ONE_PLY;
- useSleepingThreads = Options["Use Sleeping Threads"].value<bool>();
- activeThreads = Options["Threads"].value<int>();
+ std::unique_lock<Mutex> lk(mutex);
+ sleepCondition.wait(lk, [&]{ return bool(condition); });
}
-// init() is called during startup. Initializes locks and condition variables
-// and launches all threads sending them immediately to sleep.
-
-void ThreadsManager::init() {
-
- int threadID[MAX_THREADS];
-
- // This flag is needed to properly end the threads when program exits
- allThreadsShouldExit = false;
-
- // Threads will sent to sleep as soon as created, only main thread is kept alive
- activeThreads = 1;
- threads[0].state = Thread::SEARCHING;
+// Thread::idle_loop() is where the thread is parked when it has no work to do
- // Allocate pawn and material hash tables for main thread
- init_hash_tables();
+void Thread::idle_loop() {
- lock_init(&threadsLock);
-
- // Initialize thread and split point locks
- for (int i = 0; i < MAX_THREADS; i++)
+ while (!exit)
{
- lock_init(&threads[i].sleepLock);
- cond_init(&threads[i].sleepCond);
+ std::unique_lock<Mutex> lk(mutex);
- for (int j = 0; j < MAX_ACTIVE_SPLIT_POINTS; j++)
- lock_init(&(threads[i].splitPoints[j].lock));
- }
+ searching = false;
- // Create and startup all the threads but the main that is already running
- for (int i = 1; i < MAX_THREADS; i++)
- {
- threads[i].state = Thread::INITIALIZING;
- threadID[i] = i;
-
-#if defined(_MSC_VER)
- bool ok = (CreateThread(NULL, 0, start_routine, (LPVOID)&threadID[i], 0, NULL) != NULL);
-#else
- pthread_t pthreadID;
- bool ok = (pthread_create(&pthreadID, NULL, start_routine, (void*)&threadID[i]) == 0);
- pthread_detach(pthreadID);
-#endif
- if (!ok)
+ while (!searching && !exit)
{
- std::cout << "Failed to create thread number " << i << std::endl;
- ::exit(EXIT_FAILURE);
+ sleepCondition.notify_one(); // Wake up main thread if needed
+ sleepCondition.wait(lk);
}
- // Wait until the thread has finished launching and is gone to sleep
- while (threads[i].state == Thread::INITIALIZING) {}
+ lk.unlock();
+
+ if (!exit && searching)
+ search();
}
}
-// exit() is called to cleanly exit the threads when the program finishes
-
-void ThreadsManager::exit() {
+// ThreadPool::init() is called at startup to 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.
- // Force the woken up threads to exit idle_loop() and hence terminate
- allThreadsShouldExit = true;
+void ThreadPool::init() {
- for (int i = 0; i < MAX_THREADS; i++)
- {
- // Wake up all the threads and waits for termination
- if (i != 0)
- {
- threads[i].wake_up();
- while (threads[i].state != Thread::TERMINATED) {}
- }
-
- // Now we can safely destroy the locks and wait conditions
- lock_destroy(&threads[i].sleepLock);
- cond_destroy(&threads[i].sleepCond);
-
- for (int j = 0; j < MAX_ACTIVE_SPLIT_POINTS; j++)
- lock_destroy(&(threads[i].splitPoints[j].lock));
- }
-
- lock_destroy(&threadsLock);
+ push_back(new MainThread);
+ read_uci_options();
}
-// init_hash_tables() dynamically allocates pawn and material hash tables
-// according to the number of active threads. This avoids preallocating
-// memory for all possible threads if only few are used as, for instance,
-// on mobile devices where memory is scarce and allocating for MAX_THREADS
-// threads could even result in a crash.
+// ThreadPool::exit() terminates the threads before the program exits. Cannot be
+// done in destructor because threads must be terminated before freeing us.
-void ThreadsManager::init_hash_tables() {
+void ThreadPool::exit() {
- for (int i = 0; i < activeThreads; i++)
- {
- threads[i].pawnTable.init();
- threads[i].materialTable.init();
- }
+ for (Thread* th : *this)
+ delete th;
+
+ clear(); // Get rid of stale pointers
}
-// available_slave_exists() tries to find an idle thread which is available as
-// a slave for the thread with threadID "master".
+// 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.
-bool ThreadsManager::available_slave_exists(int master) const {
+void ThreadPool::read_uci_options() {
- assert(master >= 0 && master < activeThreads);
+ size_t requested = Options["Threads"];
- for (int i = 0; i < activeThreads; i++)
- if (i != master && threads[i].is_available_to(master))
- return true;
+ assert(requested > 0);
- return false;
-}
+ while (size() < requested)
+ push_back(new Thread);
+ while (size() > requested)
+ {
+ delete back();
+ pop_back();
+ }
+}
-// 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 we tell our helper threads 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 ThreadsManager::split(Position& pos, SearchStack* ss, Value alpha, Value beta,
- Value bestValue, Depth depth, Move threatMove,
- int moveCount, MovePicker* mp, int nodeType) {
- assert(pos.is_ok());
- assert(bestValue >= -VALUE_INFINITE);
- assert(bestValue <= alpha);
- assert(alpha < beta);
- assert(beta <= VALUE_INFINITE);
- assert(depth > DEPTH_ZERO);
- assert(pos.thread() >= 0 && pos.thread() < activeThreads);
- assert(activeThreads > 1);
-
- int i, master = pos.thread();
- Thread& masterThread = threads[master];
-
- // If we already have too many active split points, don't split
- if (masterThread.activeSplitPoints >= MAX_ACTIVE_SPLIT_POINTS)
- return bestValue;
-
- // Pick the next available split point object from the split point stack
- SplitPoint& splitPoint = masterThread.splitPoints[masterThread.activeSplitPoints];
-
- // Initialize the split point object
- splitPoint.parent = masterThread.splitPoint;
- splitPoint.master = master;
- splitPoint.is_betaCutoff = false;
- splitPoint.depth = depth;
- splitPoint.threatMove = threatMove;
- splitPoint.alpha = alpha;
- splitPoint.beta = beta;
- splitPoint.nodeType = nodeType;
- splitPoint.bestValue = bestValue;
- splitPoint.mp = mp;
- splitPoint.moveCount = moveCount;
- splitPoint.pos = &pos;
- splitPoint.nodes = 0;
- splitPoint.ss = ss;
- for (i = 0; i < activeThreads; i++)
- splitPoint.is_slave[i] = false;
-
- // If we are here it means we are not available
- assert(masterThread.state == Thread::SEARCHING);
-
- int workersCnt = 1; // At least the master is included
-
- // Try to allocate available threads and ask them to start searching setting
- // the state to Thread::WORKISWAITING, this must be done under lock protection
- // to avoid concurrent allocation of the same slave by another master.
- lock_grab(&threadsLock);
-
- for (i = 0; !Fake && i < activeThreads && workersCnt < maxThreadsPerSplitPoint; i++)
- if (i != master && threads[i].is_available_to(master))
- {
- workersCnt++;
- splitPoint.is_slave[i] = true;
- threads[i].splitPoint = &splitPoint;
- // This makes the slave to exit from idle_loop()
- threads[i].state = Thread::WORKISWAITING;
+// ThreadPool::nodes_searched() returns the number of nodes searched
- if (useSleepingThreads)
- threads[i].wake_up();
- }
+int64_t ThreadPool::nodes_searched() {
- lock_release(&threadsLock);
+ int64_t nodes = 0;
+ for (Thread *th : *this)
+ nodes += th->rootPos.nodes_searched();
+ return nodes;
+}
- // We failed to allocate even one slave, return
- if (!Fake && workersCnt == 1)
- return bestValue;
- masterThread.splitPoint = &splitPoint;
- masterThread.activeSplitPoints++;
- masterThread.state = Thread::WORKISWAITING;
+// ThreadPool::start_thinking() wakes up the main thread sleeping in
+// MainThread::idle_loop() and starts a new search, then returns immediately.
- // Everything is set up. The master thread enters the idle loop, from
- // which it will instantly launch a search, because its state is
- // Thread::WORKISWAITING. We send the split point as a second parameter to
- // the idle loop, which means that the main thread will return from the idle
- // loop when all threads have finished their work at this split point.
- idle_loop(master, &splitPoint);
+void ThreadPool::start_thinking(const Position& pos, const LimitsType& limits,
+ StateStackPtr& states) {
+ for (Thread* th : Threads)
+ th->join();
- // We have returned from the idle loop, which means that all threads are
- // finished. Note that changing state and decreasing activeSplitPoints is done
- // under lock protection to avoid a race with Thread::is_available_to().
- lock_grab(&threadsLock);
+ Signals.stopOnPonderhit = Signals.firstRootMove = false;
+ Signals.stop = Signals.failedLowAtRoot = false;
- masterThread.state = Thread::SEARCHING;
- masterThread.activeSplitPoints--;
- masterThread.splitPoint = splitPoint.parent;
+ main()->rootMoves.clear();
+ main()->rootPos = pos;
+ Limits = limits;
+ if (states.get()) // If we don't set a new position, preserve current state
+ {
+ SetupStates = std::move(states); // Ownership transfer here
+ assert(!states.get());
+ }
- lock_release(&threadsLock);
+ 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));
- pos.set_nodes_searched(pos.nodes_searched() + splitPoint.nodes);
- return splitPoint.bestValue;
+ main()->searching = true;
+ main()->notify_one(); // Wake up main thread: 'searching' must be already set
}
-
-// Explicit template instantiations
-template Value ThreadsManager::split<false>(Position&, SearchStack*, Value, Value, Value, Depth, Move, int, MovePicker*, int);
-template Value ThreadsManager::split<true>(Position&, SearchStack*, Value, Value, Value, Depth, Move, int, MovePicker*, int);