alternative to std::this_thread::sleep_for()

Question

I have a loop and I want to ensure that it runs for an (approximately) fixed amount of time for each loop.

I am using sleep_for to achieve this behavior but I also want the program to be able to compile on environments that do not include full support of the standard thread library. Right now I have something like this:

using namespace std;
using namespace std::chrono;

//
while( !quit )
{
    steady_clock::time_point then = steady_clock::now();

    //...do loop stuff

    steady_clock::time_point now = steady_clock::now();
#ifdef NOTHREADS
    // version for systems without thread support
    while( duration_cast< microseconds >( now - then ).count() < 10000 )
    {
        now = steady_clock::now();
    }

#else
    this_thread::sleep_for( microseconds{ 10000 - duration_cast<microseconds>( now - then ).count() } );
#endif

}

While this allows the program to compile in environments that do not support standard threads, it is also very CPU-intensive as the program checks continually for the time condition rather than waiting until it is true.

My question is: Is there a less resource-intensive way to enable this "wait" behavior using only standard C++ (i.e. not boost) in an environment that does not fully support threads?

This is going to be tough. If you could use boost there are plenty of timed callback functions that would allow you to do this easily. see here — Fantastic Mr Fox

Alexis Wilke Alexis Wilke · Accepted Answer · 2013-06-27T03:18:22

There are many time based functions, it very much depends on the Operating system you're using.

Microsoft API offers Sleep() (capital S) which gives you a millisecond sleep.

Under Unix (POSIX) you have nanosleep().

I think that these two functions should get you running on most computers.

The implementation would be to use the same loop, but sleep a little inside the while() loop. That will still be a pool like thing, but ~~faster~~ much less CPU intensive.

Also, as n.m. mentioned, select() has that capability. Just a bit more convoluted to implement, but it is expected to return once the time elapsed.

alternative to std::this_thread::sleep_for()

1 Answers