id	summary	reporter	owner	description	type	status	milestone	component	version	severity	resolution	keywords	cc
11331	boost::this_thread::sleep_for does not sleep for requested time	Scott Minor <scott.minor@…>	Niall Douglas	"boost::this_thread::sleep_for does not accurately sleep for the requested amount of time (+/- 30ms) on a Windows 7 x64 environment when the requested time is on the order of half a minute. std::this_thread::sleep_for is able to accurately sleep for the requested amount of time. Here is a sample program illustrating the issue:


{{{
#include <boost/thread.hpp>
#include <boost/chrono.hpp>

#include <chrono>
#include <iostream>
#include <thread>

void boostThreadFunction ()
{
   std::cout << ""Starting Boost thread"" << std::endl;
   for (int i = 0; i < 10; ++i)
   {
      auto sleep_time = boost::chrono::milliseconds {29000 + 100 * i};
      auto mark = std::chrono::steady_clock::now ();
      boost::this_thread::sleep_for (sleep_time);
      auto duration = std::chrono::duration_cast<std::chrono::milliseconds>(
         std::chrono::steady_clock::now () - mark);
      std::cout << ""Boost thread:"" << std::endl;
      std::cout << ""\tSupposed to sleep for:\t"" << sleep_time.count () << "" ms"" << std::endl;
      std::cout << ""\tActually slept for:\t"" << duration.count () << "" ms"" << std::endl << std::endl;
   }
}

void stdThreadFunction ()
{
   std::cout << ""Starting Std thread"" << std::endl;
   for (int i = 0; i < 10; ++i)
   {
      auto sleep_time = std::chrono::milliseconds {29000 + 100 * i};
      auto mark = std::chrono::steady_clock::now ();
      std::this_thread::sleep_for (sleep_time);
      auto duration = std::chrono::duration_cast<std::chrono::milliseconds>(
         std::chrono::steady_clock::now () - mark);
      std::cout << ""Std thread:"" << std::endl;
      std::cout << ""\tSupposed to sleep for:\t"" << sleep_time.count () << "" ms"" << std::endl;
      std::cout << ""\tActually slept for:\t"" << duration.count () << "" ms"" << std::endl << std::endl;
   }
}

int main ()
{
   boost::thread boost_thread (&boostThreadFunction);
   std::this_thread::sleep_for (std::chrono::seconds (10));
   std::thread std_thread (&stdThreadFunction);
   boost_thread.join ();
   std_thread.join ();
   system (""pause"");
   return 0;
}
}}}

Here is the output produced in my environment:


{{{
Starting Boost thread
Starting Std thread
Boost thread:
        Supposed to sleep for:  29000 ms
        Actually slept for:     29690 ms

Std thread:
        Supposed to sleep for:  29000 ms
        Actually slept for:     29009 ms

Boost thread:
        Supposed to sleep for:  29100 ms
        Actually slept for:     29999 ms

Std thread:
        Supposed to sleep for:  29100 ms
        Actually slept for:     29111 ms

Boost thread:
        Supposed to sleep for:  29200 ms
        Actually slept for:     29990 ms

Std thread:
        Supposed to sleep for:  29200 ms
        Actually slept for:     29172 ms

Boost thread:
        Supposed to sleep for:  29300 ms
        Actually slept for:     30005 ms

Std thread:
        Supposed to sleep for:  29300 ms
        Actually slept for:     29339 ms

Boost thread:
        Supposed to sleep for:  29400 ms
        Actually slept for:     30003 ms

Std thread:
        Supposed to sleep for:  29400 ms
        Actually slept for:     29405 ms

Boost thread:
        Supposed to sleep for:  29500 ms
        Actually slept for:     29999 ms

Std thread:
        Supposed to sleep for:  29500 ms
        Actually slept for:     29472 ms

Boost thread:
        Supposed to sleep for:  29600 ms
        Actually slept for:     29999 ms

Std thread:
        Supposed to sleep for:  29600 ms
        Actually slept for:     29645 ms

Boost thread:
        Supposed to sleep for:  29700 ms
        Actually slept for:     29998 ms

Std thread:
        Supposed to sleep for:  29700 ms
        Actually slept for:     29706 ms

Boost thread:
        Supposed to sleep for:  29800 ms
        Actually slept for:     29998 ms

Std thread:
        Supposed to sleep for:  29800 ms
        Actually slept for:     29807 ms

Boost thread:
        Supposed to sleep for:  29900 ms
        Actually slept for:     30014 ms

Std thread:
        Supposed to sleep for:  29900 ms
        Actually slept for:     29915 ms

}}}

Looking at libs/thread/src/win32/thread.cpp, this inaccuracy may be by design; a +/-5% tolerance appears to be added to the wait time to take advantage of coalescing timers. See related StackOverflow question: http://stackoverflow.com/questions/30381866/boost-thread-wakes-up-too-late-in-1-58

However, we are dependent on sleep_for() being as accurate as possible; for us, this is a breaking change."	Bugs	closed	To Be Determined	thread	Boost 1.58.0	Problem	wontfix	sleep_for