std::this_thread::yield() vs std::this_thread::sleep_for()

Question

What is the difference between C++11 std::this_thread::yield() and std::this_thread::sleep_for()? How to decide when to use which one?

possible duplicate of Giving up the time slice for current thread in C++ — ypnos
@dirkgently sleep_for also doesn't throw if the chrono::duration types do not throw, which is true for the standard ones, see 30.3.2.9 — Stephan Dollberg
NOTE: Use of Yields is a bad sign in programs. Basically it means that you don't have enough synchronization (i.e. you're not really tracking who's waiting on a resource and who is responsible for waking up the waiters). — Neeraj Singh

Stephan Dollberg Stephan Dollberg · Accepted Answer · 2012-06-15T10:47:02

std::this_thread::yield tells the implementation to reschedule the execution of threads, that should be used in a case where you are in a busy waiting state, like in a thread pool:

...
while(true) {
  if(pool.try_get_work()) {
    // do work
  }
  else {
    std::this_thread::yield(); // other threads can push work to the queue now
  }
}

std::this_thread::sleep_for can be used if you really want to wait for a specific amount of time. This can be used for task, where timing really matters, e.g.: if you really only want to wait for 2 seconds. (Note that the implementation might wait longer than the given time duration)

std::this_thread::yield() vs std::this_thread::sleep_for()

2 Answers