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Get rid of timer thread

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Unfortunately std::condition_variable::wait_for()
is not accurate in general case and the timer thread
can wake up also after tens or even hundreds of
millisecs after time has elapsded. CPU load, process
priorities, number of concurrent threads, even from
other processes, will have effect upon it.

Even official documentation says: "This function may
block for longer than timeout_duration due to scheduling
or resource contention delays."

So retire timer and use a polling scheme based on a
local thread counter that counts search() calls and
a small trick to keep polling frequency constant,
independently from the number of threads.

Tested for no regression at very fast TC 2+0.05 th 7:
LLR: 2.96 (-2.94,2.94) [-3.00,1.00]
Total: 32969 W: 6720 L: 6620 D: 19629

TC 2+0.05 th 1:
LLR: 2.95 (-2.94,2.94) [-3.00,1.00]
Total: 7765 W: 1917 L: 1765 D: 4083

And at STC TC, both single thread
LLR: 2.96 (-2.94,2.94) [-3.00,1.00]
Total: 15587 W: 3036 L: 2905 D: 9646

And with 7 threads
LLR: 2.95 (-2.94,2.94) [-3.00,1.00]
Total: 8149 W: 1367 L: 1227 D: 5555

bench: 8639247
This commit is contained in:
Marco Costalba
2015-11-03 11:15:14 +01:00
parent 27c5cb5912
commit 9c9205860c
4 changed files with 66 additions and 91 deletions
Download Patch File Download Diff File Expand all files Collapse all files

32
src/thread.cpp
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@@ -66,7 +66,7 @@ void ThreadBase::notify_one() {
// ThreadBase::wait() set the thread to sleep until 'condition' turns true
void ThreadBase::wait(std::atomic<bool>& condition) {
void ThreadBase::wait(std::atomic_bool& condition) {
std::unique_lock<Mutex> lk(mutex);
sleepCondition.wait(lk, [&]{ return bool(condition); });
@@ -74,7 +74,7 @@ void ThreadBase::wait(std::atomic<bool>& condition) {
// ThreadBase::wait_while() set the thread to sleep until 'condition' turns false
void ThreadBase::wait_while(std::atomic<bool>& condition) {
void ThreadBase::wait_while(std::atomic_bool& condition) {
std::unique_lock<Mutex> lk(mutex);
sleepCondition.wait(lk, [&]{ return !condition; });
@@ -86,34 +86,14 @@ void ThreadBase::wait_while(std::atomic<bool>& condition) {
Thread::Thread() {
searching = false;
maxPly = 0;
searching = resetCallsCnt = false;
maxPly = callsCnt = 0;
history.clear();
counterMoves.clear();
idx = Threads.size(); // Starts from 0
}
// TimerThread::idle_loop() is where the timer thread waits Resolution milliseconds
// and then calls check_time(). When not searching, thread sleeps until it's woken up.
void TimerThread::idle_loop() {
while (!exit)
{
std::unique_lock<Mutex> lk(mutex);
if (!exit)
sleepCondition.wait_for(lk, std::chrono::milliseconds(run ? Resolution : INT_MAX));
lk.unlock();
if (!exit && run)
check_time();
}
}
// Thread::idle_loop() is where the thread is parked when it has no work to do
void Thread::idle_loop() {
@@ -174,7 +154,6 @@ void MainThread::join() {
void ThreadPool::init() {
timer = new_thread<TimerThread>();
push_back(new_thread<MainThread>());
read_uci_options();
}
@@ -185,9 +164,6 @@ void ThreadPool::init() {
void ThreadPool::exit() {
delete_thread(timer); // As first because check_time() accesses threads data
timer = nullptr;
for (Thread* th : *this)
delete_thread(th);