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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
Download Patch File Download Diff File Expand all files Collapse all files

8
src/thread.cpp
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@@ -274,8 +274,8 @@ Value ThreadsManager::split(Position& pos, Stack* ss, Value alpha, Value beta,
// Try to allocate available threads and ask them to start searching setting
// is_searching flag. This must be done under lock protection to avoid concurrent
// allocation of the same slave by another master.
lock_grab(sp->lock);
lock_grab(splitLock);
lock_grab(sp->lock); // To protect sp->slaves_mask
for (int i = 0; i < activeThreads && !Fake; i++)
if (threads[i].is_available_to(master))
@@ -294,8 +294,8 @@ Value ThreadsManager::split(Position& pos, Stack* ss, Value alpha, Value beta,
masterThread.splitPoint = sp;
masterThread.activeSplitPoints++;
lock_release(sp->lock);
lock_release(splitLock);
lock_release(sp->lock);
// Everything is set up. The master thread enters the idle loop, from which
// it will instantly launch a search, because its is_searching flag is set.
@@ -308,16 +308,16 @@ Value ThreadsManager::split(Position& pos, Stack* ss, Value alpha, Value beta,
// We have returned from the idle loop, which means that all threads are
// finished. Note that setting is_searching and decreasing activeSplitPoints is
// done under lock protection to avoid a race with Thread::is_available_to().
lock_grab(splitLock);
lock_grab(sp->lock); // To protect sp->nodes
lock_grab(splitLock);
masterThread.is_searching = true;
masterThread.activeSplitPoints--;
masterThread.splitPoint = sp->parent;
pos.set_nodes_searched(pos.nodes_searched() + sp->nodes);
lock_release(sp->lock);
lock_release(splitLock);
lock_release(sp->lock);
return sp->bestValue;
}