If I sleep for 10 milliseconds. what do I need to increment by to get a second?

Question

i.e. i'm using std::this_thread::sleep_for(std::chrono::milliseconds(10)); in a program loop.

If I have a variable that gets incremented on this loop to show seconds elapsed, what do I need to increment by?

i.e. float x = 0;

for each step:

x += 0.01

I've tried 0.1, 0.01, 0.001, but they all seem either too fast or too slow.

Answer 1

I would recommend using absolute time points and wait_until(). Something like this:

// steady_clock is more reliable than high_resolution_clock
auto const start_time = std::chrono::steady_clock::now();
auto const wait_time = std::chrono::milliseconds{10};
auto next_time = start_time + wait_time; // regularly updated time point

for(;;)
{
    // wait for next absolute time point
    std::this_thread::sleep_until(next_time);
    next_time += wait_time; // increment absolute time

    // Use milliseconds to get to seconds to avoid
    // rounding to the nearest second
    auto const total_time = std::chrono::steady_clock::now() - start_time;
    auto const total_millisecs = double(std::chrono::duration_cast<std::chrono::milliseconds>(total_time).count());
    auto const total_seconds = total_millisecs / 1000.0;

    std::cout << "seconds: " << total_seconds << '\n';
}

Answer 2

how many 10 ms periods in one second.

  1 sec / 10 ms == 1000 ms / 10 ms == 100  (10 ms periods per second) 

But see also: https://stackoverflow.com/a/37445086/2785528