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Enable sleeping of available threads

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This simple patch has devastating consequences ;-)

Now an available thread goes to sleep and is waked up after
being allocated.

This patch allows Stockfish to dramatically increase performances
on HyperThreading systems.

Signed-off-by: Marco Costalba <mcostalba@gmail.com>
This commit is contained in:
Marco Costalba 2010-10-17 11:23:59 +01:00
parent 8fdc635255
commit c59efc53c9
1 changed files with 22 additions and 13 deletions
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35
src/search.cpp
View file

@ -95,7 +95,7 @@ namespace {
int ActiveThreads;
volatile bool AllThreadsShouldExit;
Thread threads[MAX_THREADS];
Lock MPLock, WaitLock;
Lock MPLock;
WaitCondition WaitCond[MAX_THREADS];
};
@ -2224,7 +2224,9 @@ split_point_start: // At split points actual search starts from here
// If we are not thinking, wait for a condition to be signaled
// instead of wasting CPU time polling for work.
while (threadID >= ActiveThreads || threads[threadID].state == THREAD_INITIALIZING)
while ( threadID >= ActiveThreads
|| threads[threadID].state == THREAD_INITIALIZING
|| (!sp && threads[threadID].state == THREAD_AVAILABLE))
{
assert(!sp);
assert(threadID != 0);
@ -2232,14 +2234,21 @@ split_point_start: // At split points actual search starts from here
if (AllThreadsShouldExit)
break;
lock_grab(&MPLock);
// Retest condition under lock protection
if (!( threadID >= ActiveThreads
|| threads[threadID].state == THREAD_INITIALIZING
|| (!sp && threads[threadID].state == THREAD_AVAILABLE)))
{
lock_release(&MPLock);
continue;
}
// Put thread to sleep
threads[threadID].state = THREAD_AVAILABLE;
lock_grab(&WaitLock);
if (threadID >= ActiveThreads || threads[threadID].state == THREAD_INITIALIZING)
cond_wait(&WaitCond[threadID], &WaitLock);
lock_release(&WaitLock);
cond_wait(&WaitCond[threadID], &MPLock);
lock_release(&MPLock);
}
// If this thread has been assigned work, launch a search
@ -2299,7 +2308,6 @@ split_point_start: // At split points actual search starts from here
// Initialize global locks
lock_init(&MPLock);
lock_init(&WaitLock);
for (i = 0; i < MAX_THREADS; i++)
cond_init(&WaitCond[i]);
@ -2362,7 +2370,6 @@ split_point_start: // At split points actual search starts from here
for (int j = 0; j < MAX_ACTIVE_SPLIT_POINTS; j++)
lock_destroy(&(threads[i].splitPoints[j].lock));
lock_destroy(&WaitLock);
lock_destroy(&MPLock);
// Now we can safely destroy the wait conditions
@ -2528,6 +2535,8 @@ split_point_start: // At split points actual search starts from here
assert(i == master || threads[i].state == THREAD_BOOKED);
threads[i].state = THREAD_WORKISWAITING; // This makes the slave to exit from idle_loop()
if (i != master)
wake_sleeping_thread(i);
}
// Everything is set up. The master thread enters the idle loop, from
@ -2555,9 +2564,9 @@ split_point_start: // At split points actual search starts from here
void ThreadsManager::wake_sleeping_thread(int threadID) {
lock_grab(&WaitLock);
lock_grab(&MPLock);
cond_signal(&WaitCond[threadID]);
lock_release(&WaitLock);
lock_release(&MPLock);
}