33 Concurrency support library [thread]
namespace std::this_thread {
  thread::id get_id() noexcept;
  void yield() noexcept;
  template<class Clock, class Duration>
    void sleep_until(const chrono::time_point<Clock, Duration>& abs_time);
  template<class Rep, class Period>
    void sleep_for(const chrono::duration<Rep, Period>& rel_time);
}
thread::id this_thread::get_id() noexcept;
Returns: An object of type 
thread::id
that uniquely identifies the current thread of execution
.  Every invocation from this thread of execution returns the same value
.The object returned does not compare equal to
a default-constructed 
thread::id.void this_thread::yield() noexcept;
Effects: Offers the implementation the opportunity to reschedule
. template<class Clock, class Duration>
  void sleep_until(const chrono::time_point<Clock, Duration>& abs_time);
Effects: Blocks the calling thread for the absolute timeout (
[thread.req.timing]) specified
by 
abs_time. template<class Rep, class Period>
  void sleep_for(const chrono::duration<Rep, Period>& rel_time);
Effects: Blocks the calling thread for the relative timeout (
[thread.req.timing]) specified
by 
rel_time.