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Allow split point master to sleep (take 2)

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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.

This time let it be enabled by an UCI option, so
people is free to test it on their Hyper Thread box.

Option is disabled by default.

No functional change.

Signed-off-by: Marco Costalba <mcostalba@gmail.com>
This commit is contained in:
Marco Costalba
2010-11-07 23:45:13 +01:00
parent da6e2b5fd1
commit c28b9ef182
3 changed files with 28 additions and 15 deletions
Download Patch File Download Diff File Expand all files Collapse all files

41
src/search.cpp
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@@ -259,6 +259,7 @@ namespace {
// Multi-threads related variables
Depth MinimumSplitDepth;
int MaxThreadsPerSplitPoint;
bool UseSleepingMaster;
ThreadsManager ThreadsMgr;
// Node counters, used only by thread[0] but try to keep in different cache
@@ -451,6 +452,7 @@ bool think(Position& pos, bool infinite, bool ponder, int time[], int increment[
MaxThreadsPerSplitPoint = Options["Maximum Number of Threads per Split Point"].value<int>();
MultiPV = Options["MultiPV"].value<int>();
UseLogFile = Options["Use Search Log"].value<bool>();
UseSleepingMaster = Options["Use Sleeping Master"].value<bool>();
if (UseLogFile)
LogFile.open(Options["Search Log Filename"].value<std::string>().c_str(), std::ios::out | std::ios::app);
@@ -2178,6 +2180,9 @@ 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,
@@ -2193,23 +2198,23 @@ 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 && (!sp || UseSleepingMaster)))
{
assert(!sp);
assert(threadID != 0);
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)))
// 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
|| (threads[threadID].state == THREAD_AVAILABLE && (!sp || UseSleepingMaster))))
{
lock_release(&MPLock);
continue;
break;
}
// Put thread to sleep
@@ -2239,14 +2244,19 @@ 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 (UseSleepingMaster && 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.
@@ -2454,6 +2464,7 @@ 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;