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Allow split point master to sleep

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Let to sleep even split point master, it will be waken up
by its slaves when they return from the search.

With this patch we get maximum HT speedup

Signed-off-by: Marco Costalba <mcostalba@gmail.com>
This commit is contained in:
Marco Costalba 2010-10-21 07:46:38 +01:00
parent c81bf3743f
commit 96e589646d
2 changed files with 25 additions and 15 deletions
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37
src/search.cpp
View file

@ -2212,6 +2212,9 @@ split_point_start: // At split points actual search starts from here
assert(threadID >= 0 && threadID < MAX_THREADS);
int i;
bool allFinished = false;
while (true)
{
// Slave threads can exit as soon as AllThreadsShouldExit raises,
@ -2227,23 +2230,23 @@ split_point_start: // At split points actual search starts from here
// instead of wasting CPU time polling for work.
while ( threadID >= ActiveThreads
|| threads[threadID].state == THREAD_INITIALIZING
|| (!sp && threads[threadID].state == THREAD_AVAILABLE))
|| threads[threadID].state == THREAD_AVAILABLE)
{
assert(!sp);
assert(threadID != 0);
if (AllThreadsShouldExit)
break;
lock_grab(&MPLock);
// Retest condition under lock protection
if (!( threadID >= ActiveThreads
// Test with lock held to avoid races with wake_sleeping_thread()
for (i = 0; sp && i < ActiveThreads && !sp->slaves[i]; i++) {}
allFinished = (i == ActiveThreads);
// Retest sleep conditions under lock protection
if ( AllThreadsShouldExit
|| allFinished
|| !( threadID >= ActiveThreads
|| threads[threadID].state == THREAD_INITIALIZING
|| (!sp && threads[threadID].state == THREAD_AVAILABLE)))
|| threads[threadID].state == THREAD_AVAILABLE))
{
lock_release(&MPLock);
continue;
break;
}
// Put thread to sleep
@ -2273,14 +2276,19 @@ split_point_start: // At split points actual search starts from here
assert(threads[threadID].state == THREAD_SEARCHING);
threads[threadID].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 (threadID != tsp->master && threads[tsp->master].state == THREAD_AVAILABLE)
wake_sleeping_thread(tsp->master);
}
// 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.
int i = 0;
for ( ; sp && i < ActiveThreads && !sp->slaves[i]; i++) {}
for (i = 0; sp && i < ActiveThreads && !sp->slaves[i]; i++) {}
allFinished = (i == ActiveThreads);
if (i == ActiveThreads)
if (allFinished)
{
// Because sp->slaves[] is reset under lock protection,
// be sure sp->lock has been released before to return.
@ -2487,6 +2495,7 @@ split_point_start: // At split points actual search starts from here
// Initialize the split point object
splitPoint.parent = masterThread.splitPoint;
splitPoint.master = master;
splitPoint.stopRequest = false;
splitPoint.ply = ply;
splitPoint.depth = depth;

1
src/thread.h
View file

@ -55,6 +55,7 @@ struct SplitPoint {
bool pvNode, mateThreat;
Value beta;
int ply;
int master;
Move threatMove;
SearchStack sstack[MAX_THREADS][PLY_MAX_PLUS_2];