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Split also if no slaves are found

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Because we test for available slaves before
entering split(), we almost always allocate a
slave, only in the rare case of a race (less
then 2% of cases) this is not true, but to
special case this occurrence is not worth
the added complexity.

bench: 7451319
This commit is contained in:
Marco Costalba 2014-03-15 23:43:35 +01:00
parent a1a7bc84da
commit a091ae4cc8
1 changed files with 21 additions and 27 deletions
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48
src/thread.cpp
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@ -296,41 +296,35 @@ void Thread::split(Position& pos, const Stack* ss, Value alpha, Value beta, Valu
activeSplitPoint = &sp;
activePosition = NULL;
int slavesCnt = 1; // This thread is always included
Thread* slave;
while (!Fake && (slave = Threads.available_slave(this)) != NULL)
{
++slavesCnt;
sp.slavesMask |= 1ULL << slave->idx;
slave->activeSplitPoint = &sp;
slave->searching = true; // Slave leaves idle_loop()
slave->notify_one(); // Could be sleeping
}
if (!Fake)
for (Thread* slave; (slave = Threads.available_slave(this)) != NULL; )
{
sp.slavesMask |= 1ULL << slave->idx;
slave->activeSplitPoint = &sp;
slave->searching = true; // Slave leaves idle_loop()
slave->notify_one(); // Could be sleeping
}
// Everything is set up. The master thread enters the idle loop, from which
// it will instantly launch a search, because its 'searching' flag is set.
// The thread will return from the idle loop when all slaves have finished
// their work at this split point.
if (slavesCnt > 1 || Fake)
{
sp.mutex.unlock();
Threads.mutex.unlock();
sp.mutex.unlock();
Threads.mutex.unlock();
Thread::idle_loop(); // Force a call to base class idle_loop()
Thread::idle_loop(); // Force a call to base class idle_loop()
// In the helpful master concept, a master can help only a sub-tree of its
// split point and because everything is finished here, it's not possible
// for the master to be booked.
assert(!searching);
assert(!activePosition);
// In the helpful master concept, a master can help only a sub-tree of its
// split point and because everything is finished here, it's not possible
// for the master to be booked.
assert(!searching);
assert(!activePosition);
// We have returned from the idle loop, which means that all threads are
// finished. Note that setting 'searching' and decreasing splitPointsSize is
// done under lock protection to avoid a race with Thread::available_to().
Threads.mutex.lock();
sp.mutex.lock();
}
// We have returned from the idle loop, which means that all threads are
// finished. Note that setting 'searching' and decreasing splitPointsSize is
// done under lock protection to avoid a race with Thread::available_to().
Threads.mutex.lock();
sp.mutex.lock();
searching = true;
--splitPointsSize;