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Reduce lock contention in idle_loop

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Release split point lock before to wake up
master thread. This seems to increase speed
in case "sleeping threads" are used:

After 7792 games with 4 threads at very fast TC (2"+0.05)
Mod vs Orig 1722 - 1627 - 4443 ELO +4 (+- 5.1)

No functional change.

Signed-off-by: Marco Costalba <mcostalba@gmail.com>
This commit is contained in:
Marco Costalba
2012-02-03 13:18:51 +01:00
parent 57e942145c
commit c94cfebb7e
3 changed files with 12 additions and 12 deletions
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src/search.cpp
+8 -7
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@@ -1873,6 +1873,7 @@ void Thread::idle_loop(SplitPoint* sp_master) {
Stack ss[MAX_PLY_PLUS_2];
Position pos(*sp->pos, threadID);
int master = sp->master;
memcpy(ss, sp->ss - 1, 4 * sizeof(Stack));
(ss+1)->sp = sp;
@@ -1894,17 +1895,17 @@ void Thread::idle_loop(SplitPoint* sp_master) {
sp->slavesMask &= ~(1ULL << threadID);
sp->nodes += pos.nodes_searched();
// 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 ( Threads.use_sleeping_threads()
&& threadID != sp->master
&& !Threads[sp->master].is_searching)
Threads[sp->master].wake_up();
// After releasing the lock we cannot access anymore any SplitPoint
// related data in a reliably way becuase it could have been released
// under our feet by the sp master.
lock_release(sp->lock);
// 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 ( Threads.use_sleeping_threads()
&& threadID != master
&& !Threads[master].is_searching)
Threads[master].wake_up();
}
}
// In helpful master concept a master can help only a sub-tree of its split