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Code Issues Releases Wiki Activity

Move idle_loop() under Thread

Browse source 
This greatly removes clutter from the difficult idle_loop() function

No functional change.

Signed-off-by: Marco Costalba <mcostalba@gmail.com>
This commit is contained in:
Marco Costalba 2011-08-08 12:03:16 +01:00
parent dafd5b5864
commit ba85c59d96
3 changed files with 80 additions and 65 deletions
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93
src/search.cpp
View file

@ -2130,50 +2130,56 @@ split_point_start: // At split points actual search starts from here
} // namespace
// ThreadsManager::idle_loop() is where the threads are parked when they have no work
// to do. The parameter 'sp', if non-NULL, is a pointer to an active SplitPoint
// object for which the current thread is the master.
// Little helper used by idle_loop() to check that all the slaves of a
// master thread have finished searching.
void ThreadsManager::idle_loop(int threadID, SplitPoint* sp) {
static bool all_slaves_finished(SplitPoint* sp) {
assert(threadID >= 0 && threadID < MAX_THREADS);
assert(sp);
int i;
bool allFinished;
for (int i = 0; i < Threads.size(); i++)
if (sp->is_slave[i])
return false;
return true;
}
// Thread::idle_loop() is where the thread is parked when it has no work to do.
// The parameter 'sp', if non-NULL, is a pointer to an active SplitPoint object
// for which the thread is the master.
void Thread::idle_loop(SplitPoint* sp) {
while (true)
{
// Slave threads can exit as soon as allThreadsShouldExit flag raises,
// master should exit as last one.
if (allThreadsShouldExit)
{
assert(!sp);
threads[threadID].state = Thread::TERMINATED;
return;
}
// If we are not searching, wait for a condition to be signaled
// instead of wasting CPU time polling for work.
while ( threadID >= activeThreads
|| threads[threadID].state == Thread::INITIALIZING
|| (useSleepingThreads && threads[threadID].state == Thread::AVAILABLE))
while ( do_sleep
|| do_terminate
|| (Threads.use_sleeping_threads() && state == Thread::AVAILABLE))
{
assert(!sp || useSleepingThreads);
assert(threadID != 0 || useSleepingThreads);
assert(!sp || Threads.use_sleeping_threads());
assert(threadID != 0 || Threads.use_sleeping_threads());
if (threads[threadID].state == Thread::INITIALIZING)
threads[threadID].state = Thread::AVAILABLE;
// Slave thread should exit as soon as do_terminate flag raises
if (do_terminate)
{
assert(!sp);
state = Thread::TERMINATED;
return;
}
if (state == Thread::INITIALIZING)
state = Thread::AVAILABLE;
// Grab the lock to avoid races with Thread::wake_up()
lock_grab(&threads[threadID].sleepLock);
lock_grab(&sleepLock);
// If we are master and all slaves have finished don't go to sleep
for (i = 0; sp && i < activeThreads && !sp->is_slave[i]; i++) {}
allFinished = (i == activeThreads);
if (allFinished || allThreadsShouldExit)
if (sp && all_slaves_finished(sp))
{
lock_release(&threads[threadID].sleepLock);
lock_release(&sleepLock);
break;
}
@ -2181,22 +2187,22 @@ void ThreadsManager::idle_loop(int threadID, SplitPoint* sp) {
// particular we need to avoid a deadlock in case a master thread has,
// in the meanwhile, allocated us and sent the wake_up() call before we
// had the chance to grab the lock.
if (threadID >= activeThreads || threads[threadID].state == Thread::AVAILABLE)
cond_wait(&threads[threadID].sleepCond, &threads[threadID].sleepLock);
if (do_sleep || state == Thread::AVAILABLE)
cond_wait(&sleepCond, &sleepLock);
lock_release(&threads[threadID].sleepLock);
lock_release(&sleepLock);
}
// If this thread has been assigned work, launch a search
if (threads[threadID].state == Thread::WORKISWAITING)
if (state == Thread::WORKISWAITING)
{
assert(!allThreadsShouldExit);
assert(!do_terminate);
threads[threadID].state = Thread::SEARCHING;
state = Thread::SEARCHING;
// Copy split point position and search stack and call search()
SearchStack ss[PLY_MAX_PLUS_2];
SplitPoint* tsp = threads[threadID].splitPoint;
SplitPoint* tsp = splitPoint;
Position pos(*tsp->pos, threadID);
memcpy(ss, tsp->ss - 1, 4 * sizeof(SearchStack));
@ -2211,24 +2217,21 @@ void ThreadsManager::idle_loop(int threadID, SplitPoint* sp) {
else
assert(false);
assert(threads[threadID].state == Thread::SEARCHING);
assert(state == Thread::SEARCHING);
threads[threadID].state = Thread::AVAILABLE;
state = Thread::AVAILABLE;
// Wake up master thread so to allow it to return from the idle loop in
// case we are the last slave of the split point.
if ( useSleepingThreads
if ( Threads.use_sleeping_threads()
&& threadID != tsp->master
&& threads[tsp->master].state == Thread::AVAILABLE)
threads[tsp->master].wake_up();
&& Threads[tsp->master].state == Thread::AVAILABLE)
Threads[tsp->master].wake_up();
}
// If this thread is the master of a split point and all slaves have
// finished their work at this split point, return from the idle loop.
for (i = 0; sp && i < activeThreads && !sp->is_slave[i]; i++) {}
allFinished = (i == activeThreads);
if (allFinished)
if (sp && all_slaves_finished(sp))
{
// Because sp->is_slave[] is reset under lock protection,
// be sure sp->lock has been released before to return.

43
src/thread.cpp
View file

@ -35,7 +35,7 @@ namespace { extern "C" {
DWORD WINAPI start_routine(LPVOID threadID) {
Threads.idle_loop(*(int*)threadID, NULL);
Threads[*(int*)threadID].idle_loop(NULL);
return 0;
}
@ -43,7 +43,7 @@ namespace { extern "C" {
void* start_routine(void* threadID) {
Threads.idle_loop(*(int*)threadID, NULL);
Threads[*(int*)threadID].idle_loop(NULL);
return NULL;
}
@ -111,7 +111,22 @@ void ThreadsManager::read_uci_options() {
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>();
set_size(Options["Threads"].value<int>());
}
// set_size() changes the number of active threads and raises do_sleep flag for
// all the unused threads that will go immediately to sleep.
void ThreadsManager::set_size(int cnt) {
assert(cnt > 0 && cnt <= MAX_THREADS);
activeThreads = cnt;
for (int i = 0; i < MAX_THREADS; i++)
threads[i].do_sleep = !(i < activeThreads);
}
@ -120,14 +135,10 @@ void ThreadsManager::read_uci_options() {
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;
set_size(1);
threads[0].state = Thread::SEARCHING;
threads[0].threadID = 0;
// Allocate pawn and material hash tables for main thread
init_hash_tables();
@ -149,13 +160,13 @@ void ThreadsManager::init() {
for (int i = 1; i < MAX_THREADS; i++)
{
threads[i].state = Thread::INITIALIZING;
threadID[i] = i;
threads[i].threadID = i;
#if defined(_MSC_VER)
bool ok = (CreateThread(NULL, 0, start_routine, (LPVOID)&threadID[i], 0, NULL) != NULL);
bool ok = (CreateThread(NULL, 0, start_routine, (LPVOID)&threads[i].threadID , 0, NULL) != NULL);
#else
pthread_t pthreadID;
bool ok = (pthread_create(&pthreadID, NULL, start_routine, (void*)&threadID[i]) == 0);
bool ok = (pthread_create(&pthreadID, NULL, start_routine, (void*)&threads[i].threadID) == 0);
pthread_detach(pthreadID);
#endif
if (!ok)
@ -174,14 +185,12 @@ void ThreadsManager::init() {
void ThreadsManager::exit() {
// Force the woken up threads to exit idle_loop() and hence terminate
allThreadsShouldExit = true;
for (int i = 0; i < MAX_THREADS; i++)
{
// Wake up all the threads and wait for termination
// Wake up all the slave threads and wait for termination
if (i != 0)
{
threads[i].do_terminate = true;
threads[i].wake_up();
while (threads[i].state != Thread::TERMINATED) {}
}
@ -318,7 +327,7 @@ Value ThreadsManager::split(Position& pos, SearchStack* ss, Value alpha, Value b
// 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, sp);
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.

9
src/thread.h
View file

@ -77,16 +77,20 @@ struct Thread {
void wake_up();
bool cutoff_occurred() const;
bool is_available_to(int master) const;
void idle_loop(SplitPoint* sp);
SplitPoint splitPoints[MAX_ACTIVE_SPLIT_POINTS];
MaterialInfoTable materialTable;
PawnInfoTable pawnTable;
int threadID;
int maxPly;
Lock sleepLock;
WaitCondition sleepCond;
volatile ThreadState state;
SplitPoint* volatile splitPoint;
volatile int activeSplitPoints;
volatile bool do_sleep;
volatile bool do_terminate;
};
@ -105,13 +109,13 @@ public:
void exit();
void init_hash_tables();
bool use_sleeping_threads() const { return useSleepingThreads; }
int min_split_depth() const { return minimumSplitDepth; }
int size() const { return activeThreads; }
void set_size(int cnt) { activeThreads = cnt; }
void set_size(int cnt);
void read_uci_options();
bool available_slave_exists(int master) const;
void idle_loop(int threadID, SplitPoint* sp);
template <bool Fake>
Value split(Position& pos, SearchStack* ss, Value alpha, Value beta, Value bestValue,
@ -123,7 +127,6 @@ private:
int maxThreadsPerSplitPoint;
int activeThreads;
bool useSleepingThreads;
volatile bool allThreadsShouldExit;
};
extern ThreadsManager Threads;