From 9c9205860c5ab0e4f3180298e3f7082be259772c Mon Sep 17 00:00:00 2001 From: Marco Costalba Date: Tue, 3 Nov 2015 11:15:14 +0100 Subject: [PATCH] Get rid of timer thread Unfortunately std::condition_variable::wait_for() is not accurate in general case and the timer thread can wake up also after tens or even hundreds of millisecs after time has elapsded. CPU load, process priorities, number of concurrent threads, even from other processes, will have effect upon it. Even official documentation says: "This function may block for longer than timeout_duration due to scheduling or resource contention delays." So retire timer and use a polling scheme based on a local thread counter that counts search() calls and a small trick to keep polling frequency constant, independently from the number of threads. Tested for no regression at very fast TC 2+0.05 th 7: LLR: 2.96 (-2.94,2.94) [-3.00,1.00] Total: 32969 W: 6720 L: 6620 D: 19629 TC 2+0.05 th 1: LLR: 2.95 (-2.94,2.94) [-3.00,1.00] Total: 7765 W: 1917 L: 1765 D: 4083 And at STC TC, both single thread LLR: 2.96 (-2.94,2.94) [-3.00,1.00] Total: 15587 W: 3036 L: 2905 D: 9646 And with 7 threads LLR: 2.95 (-2.94,2.94) [-3.00,1.00] Total: 8149 W: 1367 L: 1227 D: 5555 bench: 8639247 --- src/search.cpp | 95 ++++++++++++++++++++++++++++---------------------- src/search.h | 2 +- src/thread.cpp | 32 +++-------------- src/thread.h | 28 +++++---------- 4 files changed, 66 insertions(+), 91 deletions(-) diff --git a/src/search.cpp b/src/search.cpp index 39a73193..eb9a0891 100644 --- a/src/search.cpp +++ b/src/search.cpp @@ -141,6 +141,7 @@ namespace { Value value_from_tt(Value v, int ply); void update_pv(Move* pv, Move move, Move* childPv); void update_stats(const Position& pos, Stack* ss, Move move, Depth depth, Move* quiets, int quietsCnt); + void check_time(); } // namespace @@ -298,14 +299,10 @@ void MainThread::think() { } } - Threads.timer->run = true; - Threads.timer->notify_one(); // Start the recurring timer - search(true); // Let's start searching! - // Stop the threads and the timer + // Stop the threads Signals.stop = true; - Threads.timer->run = false; // Wait until all threads have finished for (Thread* th : Threads) @@ -585,6 +582,20 @@ namespace { bestValue = -VALUE_INFINITE; ss->ply = (ss-1)->ply + 1; + // Check for available remaining time + if (thisThread->resetCallsCnt.load(std::memory_order_relaxed)) + { + thisThread->resetCallsCnt = false; + thisThread->callsCnt = 0; + } + if (++thisThread->callsCnt > 4096) + { + for (Thread* th : Threads) + th->resetCallsCnt = true; + + check_time(); + } + // Used to send selDepth info to GUI if (PvNode && thisThread->maxPly < ss->ply) thisThread->maxPly = ss->ply; @@ -1455,6 +1466,43 @@ moves_loop: // When in check search starts from here return best; } + + // check_time() is used to print debug info and, more importantly, to detect + // when we are out of available time and thus stop the search. + + void check_time() { + + static TimePoint lastInfoTime = now(); + + int elapsed = Time.elapsed(); + TimePoint tick = Limits.startTime + elapsed; + + if (tick - lastInfoTime >= 1000) + { + lastInfoTime = tick; + dbg_print(); + } + + // An engine may not stop pondering until told so by the GUI + if (Limits.ponder) + return; + + if (Limits.use_time_management()) + { + bool stillAtFirstMove = Signals.firstRootMove.load(std::memory_order_relaxed) + && !Signals.failedLowAtRoot.load(std::memory_order_relaxed) + && elapsed > Time.available() * 3 / 4; + + if (stillAtFirstMove || elapsed > Time.maximum() - 10) + Signals.stop = true; + } + else if (Limits.movetime && elapsed >= Limits.movetime) + Signals.stop = true; + + else if (Limits.nodes && Threads.nodes_searched() >= Limits.nodes) + Signals.stop = true; + } + } // namespace @@ -1565,40 +1613,3 @@ bool RootMove::extract_ponder_from_tt(Position& pos) return false; } - - -/// TimerThread::check_time() is called by when the timer triggers. It is used -/// to print debug info and, more importantly, to detect when we are out of -/// available time and thus stop the search. - -void TimerThread::check_time() { - - static TimePoint lastInfoTime = now(); - int elapsed = Time.elapsed(); - - if (now() - lastInfoTime >= 1000) - { - lastInfoTime = now(); - dbg_print(); - } - - // An engine may not stop pondering until told so by the GUI - if (Limits.ponder) - return; - - if (Limits.use_time_management()) - { - bool stillAtFirstMove = Signals.firstRootMove - && !Signals.failedLowAtRoot - && elapsed > Time.available() * 3 / 4; - - if ( stillAtFirstMove - || elapsed > Time.maximum() - 2 * TimerThread::Resolution) - Signals.stop = true; - } - else if (Limits.movetime && elapsed >= Limits.movetime) - Signals.stop = true; - - else if (Limits.nodes && Threads.nodes_searched() >= Limits.nodes) - Signals.stop = true; -} diff --git a/src/search.h b/src/search.h index 809a15d1..96c0a2d1 100644 --- a/src/search.h +++ b/src/search.h @@ -93,7 +93,7 @@ struct LimitsType { /// typically in an async fashion e.g. to stop the search by the GUI. struct SignalsType { - std::atomic stop, stopOnPonderhit, firstRootMove, failedLowAtRoot; + std::atomic_bool stop, stopOnPonderhit, firstRootMove, failedLowAtRoot; }; typedef std::unique_ptr> StateStackPtr; diff --git a/src/thread.cpp b/src/thread.cpp index 34424d37..c76b4b70 100644 --- a/src/thread.cpp +++ b/src/thread.cpp @@ -66,7 +66,7 @@ void ThreadBase::notify_one() { // ThreadBase::wait() set the thread to sleep until 'condition' turns true -void ThreadBase::wait(std::atomic& condition) { +void ThreadBase::wait(std::atomic_bool& condition) { std::unique_lock lk(mutex); sleepCondition.wait(lk, [&]{ return bool(condition); }); @@ -74,7 +74,7 @@ void ThreadBase::wait(std::atomic& condition) { // ThreadBase::wait_while() set the thread to sleep until 'condition' turns false -void ThreadBase::wait_while(std::atomic& condition) { +void ThreadBase::wait_while(std::atomic_bool& condition) { std::unique_lock lk(mutex); sleepCondition.wait(lk, [&]{ return !condition; }); @@ -86,34 +86,14 @@ void ThreadBase::wait_while(std::atomic& condition) { Thread::Thread() { - searching = false; - maxPly = 0; + searching = resetCallsCnt = false; + maxPly = callsCnt = 0; history.clear(); counterMoves.clear(); idx = Threads.size(); // Starts from 0 } -// 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. - -void TimerThread::idle_loop() { - - while (!exit) - { - std::unique_lock lk(mutex); - - if (!exit) - sleepCondition.wait_for(lk, std::chrono::milliseconds(run ? Resolution : INT_MAX)); - - lk.unlock(); - - if (!exit && run) - check_time(); - } -} - - // Thread::idle_loop() is where the thread is parked when it has no work to do void Thread::idle_loop() { @@ -174,7 +154,6 @@ void MainThread::join() { void ThreadPool::init() { - timer = new_thread(); push_back(new_thread()); read_uci_options(); } @@ -185,9 +164,6 @@ void ThreadPool::init() { void ThreadPool::exit() { - delete_thread(timer); // As first because check_time() accesses threads data - timer = nullptr; - for (Thread* th : *this) delete_thread(th); diff --git a/src/thread.h b/src/thread.h index fd7343a8..6cceca72 100644 --- a/src/thread.h +++ b/src/thread.h @@ -44,12 +44,12 @@ struct ThreadBase : public std::thread { virtual ~ThreadBase() = default; virtual void idle_loop() = 0; void notify_one(); - void wait(std::atomic& b); - void wait_while(std::atomic& b); + void wait(std::atomic_bool& b); + void wait_while(std::atomic_bool& b); Mutex mutex; ConditionVariable sleepCondition; - std::atomic exit; + std::atomic_bool exit; }; @@ -68,8 +68,8 @@ struct Thread : public ThreadBase { Material::Table materialTable; Endgames endgames; size_t idx, PVIdx; - int maxPly; - std::atomic searching; + int maxPly, callsCnt; + std::atomic_bool searching, resetCallsCnt; Position rootPos; Search::RootMoveVector rootMoves; @@ -80,25 +80,14 @@ struct Thread : public ThreadBase { }; -/// MainThread and TimerThread are derived classes used to characterize the two -/// special threads: the main one and the recurring timer. +/// MainThread is a derived classes used to characterize the the main one struct MainThread : public Thread { MainThread() { thinking = true; } // Avoid a race with start_thinking() virtual void idle_loop(); void join(); void think(); - std::atomic thinking; -}; - -struct TimerThread : public ThreadBase { - - static const int Resolution = 5; // Millisec between two check_time() calls - - virtual void idle_loop(); - void check_time(); - - bool run = false; + std::atomic_bool thinking; }; @@ -108,14 +97,13 @@ struct TimerThread : public ThreadBase { struct ThreadPool : public std::vector { - void init(); // No constructor and destructor, threads rely on globals that should + void init(); // No constructor and destructor, threads rely on globals that should void exit(); // be initialized and valid during the whole thread lifetime. MainThread* main() { return static_cast(at(0)); } void read_uci_options(); void start_thinking(const Position&, const Search::LimitsType&, Search::StateStackPtr&); int64_t nodes_searched(); - TimerThread* timer; }; extern ThreadPool Threads; -- 2.39.2