From: Marco Costalba Date: Mon, 28 Nov 2011 14:54:40 +0000 (+0100) Subject: Tidy up comments in thread.cpp X-Git-Url: https://git.sesse.net/?p=stockfish;a=commitdiff_plain;h=0f7cbaca75124d88136d356cf7b082207b572b3c Tidy up comments in thread.cpp No functional change. Signed-off-by: Marco Costalba --- diff --git a/src/thread.cpp b/src/thread.cpp index 06646a7b..8af9dc41 100644 --- a/src/thread.cpp +++ b/src/thread.cpp @@ -23,14 +23,14 @@ #include "thread.h" #include "ucioption.h" -ThreadsManager Threads; // Global object definition +ThreadsManager Threads; // Global object namespace { extern "C" { // start_routine() is the C function which is called when a new thread - // is launched. It simply calls idle_loop() of the supplied thread. The - // last two threads are dedicated to read input from GUI and to mimic a - // timer, so they run in listener_loop() and timer_loop() respectively. + // is launched. It simply calls idle_loop() of the supplied thread. The first + // and last thread are special. First one is the main search thread while the + // last one mimics a timer, they run in main_loop() and timer_loop(). #if defined(_MSC_VER) DWORD WINAPI start_routine(LPVOID thread) { @@ -38,13 +38,16 @@ namespace { extern "C" { void* start_routine(void* thread) { #endif - if (((Thread*)thread)->threadID == 0) - ((Thread*)thread)->main_loop(); + Thread* th = (Thread*)thread; + + if (th->threadID == 0) + th->main_loop(); + + else if (th->threadID == MAX_THREADS) + th->timer_loop(); - else if (((Thread*)thread)->threadID == MAX_THREADS) - ((Thread*)thread)->timer_loop(); else - ((Thread*)thread)->idle_loop(NULL); + th->idle_loop(NULL); return 0; } @@ -71,6 +74,7 @@ bool Thread::cutoff_occurred() const { for (SplitPoint* sp = splitPoint; sp; sp = sp->parent) if (sp->is_betaCutoff) return true; + return false; } @@ -101,9 +105,8 @@ bool Thread::is_available_to(int master) const { } -// 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. +// read_uci_options() updates number of active threads and other parameters +// according to the UCI options values. It is called before to start a new search. void ThreadsManager::read_uci_options() { @@ -129,9 +132,7 @@ void ThreadsManager::set_size(int cnt) { { // Dynamically allocate 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 could - // even result in a crash. + // possible threads if only few are used. threads[i].pawnTable.init(); threads[i].materialTable.init(); @@ -147,13 +148,11 @@ void ThreadsManager::set_size(int cnt) { void ThreadsManager::init() { - // Initialize sleep condition used to block waiting for end of searching + // Initialize sleep condition and lock used by thread manager cond_init(&sleepCond); - - // Initialize threads lock, used when allocating slaves during splitting lock_init(&threadsLock); - // Initialize sleep and split point locks + // Initialize thread's sleep conditions and split point locks for (int i = 0; i <= MAX_THREADS; i++) { lock_init(&threads[i].sleepLock); @@ -163,7 +162,7 @@ void ThreadsManager::init() { lock_init(&(threads[i].splitPoints[j].lock)); } - // Initialize main thread's associated data + // Allocate main thread tables to call evaluate() also when not searching threads[0].pawnTable.init(); threads[0].materialTable.init(); @@ -178,7 +177,7 @@ void ThreadsManager::init() { threads[i].handle = CreateThread(NULL, 0, start_routine, (LPVOID)&threads[i], 0, NULL); bool ok = (threads[i].handle != NULL); #else - bool ok = (pthread_create(&threads[i].handle, NULL, start_routine, (void*)&threads[i]) == 0); + bool ok = !pthread_create(&threads[i].handle, NULL, start_routine, (void*)&threads[i]); #endif if (!ok) @@ -199,7 +198,7 @@ void ThreadsManager::exit() { threads[i].do_terminate = true; threads[i].wake_up(); - // Wait for slave termination + // Wait for thread termination #if defined(_MSC_VER) WaitForSingleObject(threads[i].handle, 0); CloseHandle(threads[i].handle); @@ -207,7 +206,7 @@ void ThreadsManager::exit() { pthread_join(threads[i].handle, NULL); #endif - // Now we can safely destroy locks and wait conditions + // Now we can safely destroy associated locks and wait conditions lock_destroy(&threads[i].sleepLock); cond_destroy(&threads[i].sleepCond); @@ -221,14 +220,14 @@ void ThreadsManager::exit() { // available_slave_exists() tries to find an idle thread which is available as -// a slave for the thread with threadID "master". +// a slave for the thread with threadID 'master'. bool ThreadsManager::available_slave_exists(int master) const { assert(master >= 0 && master < activeThreads); for (int i = 0; i < activeThreads; i++) - if (i != master && threads[i].is_available_to(master)) + if (threads[i].is_available_to(master)) return true; return false; @@ -249,13 +248,13 @@ bool ThreadsManager::split_point_finished(SplitPoint* sp) const { // 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. +// 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 Value ThreadsManager::split(Position& pos, SearchStack* ss, Value alpha, Value beta, @@ -277,10 +276,10 @@ Value ThreadsManager::split(Position& pos, SearchStack* ss, Value alpha, Value b if (masterThread.activeSplitPoints >= MAX_ACTIVE_SPLIT_POINTS) return bestValue; - // Pick the next available split point object from the split point stack - SplitPoint* sp = masterThread.splitPoints + masterThread.activeSplitPoints; + // Pick the next available split point from the split point stack + SplitPoint* sp = &masterThread.splitPoints[masterThread.activeSplitPoints]; - // Initialize the split point object + // Initialize the split point sp->parent = masterThread.splitPoint; sp->master = master; sp->is_betaCutoff = false; @@ -295,6 +294,7 @@ Value ThreadsManager::split(Position& pos, SearchStack* ss, Value alpha, Value b sp->pos = &pos; sp->nodes = 0; sp->ss = ss; + for (i = 0; i < activeThreads; i++) sp->is_slave[i] = false; @@ -304,12 +304,12 @@ Value ThreadsManager::split(Position& pos, SearchStack* ss, Value alpha, Value b 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. + // is_searching flag. 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)) + if (threads[i].is_available_to(master)) { workersCnt++; sp->is_slave[i] = true; @@ -338,8 +338,8 @@ Value ThreadsManager::split(Position& pos, SearchStack* ss, Value alpha, Value b // their work at this split point. masterThread.idle_loop(sp); - // In helpful master concept a master can help only a sub-tree, and - // because here is all finished is not possible master is booked. + // 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(!masterThread.is_searching); // We have returned from the idle loop, which means that all threads are @@ -363,8 +363,8 @@ template Value ThreadsManager::split(Position&, SearchStack*, Value, Valu template Value ThreadsManager::split(Position&, SearchStack*, Value, Value, Value, Depth, Move, int, MovePicker*, int); -// Thread::timer_loop() is where the timer thread waits maxPly milliseconds -// and then calls do_timer_event(). +// Thread::timer_loop() is where the timer thread waits maxPly milliseconds and +// then calls do_timer_event(). If maxPly is 0 thread sleeps until is woken up. void Thread::timer_loop() { @@ -402,7 +402,6 @@ void Thread::main_loop() { lock_grab(&sleepLock); do_sleep = true; // Always return to sleep after a search - is_searching = false; while (do_sleep && !do_terminate) @@ -418,7 +417,7 @@ void Thread::main_loop() { if (do_terminate) return; - Search::think(); + Search::think(); // This is the search entry point } } @@ -438,16 +437,16 @@ void ThreadsManager::start_thinking(const Position& pos, const Search::LimitsTyp while (!main.do_sleep) cond_wait(&sleepCond, &main.sleepLock); - // Copy input arguments to Search global variables + // Copy input arguments to initialize the search Search::RootPosition.copy(pos, 0); Search::Limits = limits; Search::RootMoves = searchMoves; - // Reset signals before to start the search + // Reset signals before to start the new search memset((void*)&Search::Signals, 0, sizeof(Search::Signals)); main.do_sleep = false; - cond_signal(&main.sleepCond); // Wake up main thread + cond_signal(&main.sleepCond); // Wake up main thread and start searching if (!asyncMode) cond_wait(&sleepCond, &main.sleepLock); @@ -459,9 +458,9 @@ void ThreadsManager::start_thinking(const Position& pos, const Search::LimitsTyp // ThreadsManager::wait_for_stop_or_ponderhit() is called when the maximum depth // is reached while the program is pondering. The point is to work around a wrinkle // in the UCI protocol: When pondering, the engine is not allowed to give a -// "bestmove" before the GUI sends it a "stop" or "ponderhit" command. -// We simply wait here until one of these commands (that raise StopRequest) is -// sent, and return, after which the bestmove and pondermove will be printed. +// "bestmove" before the GUI sends it a "stop" or "ponderhit" command. We simply +// wait here until one of these commands (that raise StopRequest) is sent and +// then return, after which the bestmove and pondermove will be printed. void ThreadsManager::wait_for_stop_or_ponderhit() { diff --git a/src/thread.h b/src/thread.h index 0a38caae..13615c2c 100644 --- a/src/thread.h +++ b/src/thread.h @@ -59,10 +59,10 @@ struct SplitPoint { }; -/// Thread struct is used to keep together all the thread related stuff like locks, -/// state and especially split points. We also use per-thread pawn and material hash -/// tables so that once we get a pointer to an entry its life time is unlimited and -/// we don't have to care about someone changing the entry under our feet. +/// Thread struct keeps together all the thread related stuff like locks, state +/// and especially split points. We also use per-thread pawn and material hash +/// tables so that once we get a pointer to an entry its life time is unlimited +/// and we don't have to care about someone changing the entry under our feet. struct Thread { @@ -94,9 +94,9 @@ struct Thread { }; -/// ThreadsManager class is used to handle all the threads related stuff like init, -/// starting, parking and, the most important, launching a slave thread at a split -/// point. All the access to shared thread data is done through this class. +/// ThreadsManager class handles all the threads related stuff like init, starting, +/// parking and, the most important, launching a slave thread at a split point. +/// All the access to shared thread data is done through this class. class ThreadsManager { /* As long as the single ThreadsManager object is defined as a global we don't @@ -127,7 +127,7 @@ public: private: friend struct Thread; - Thread threads[MAX_THREADS + 2]; // Last 2 are the listener and the timer + Thread threads[MAX_THREADS + 1]; // Last one is used as a timer Lock threadsLock; Depth minimumSplitDepth; int maxThreadsPerSplitPoint;