std::this_thread::yield

C++

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Named requirements

Language support library

Concepts library (C++20)

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Numerics library

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Regular expressions library (C++11)

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Technical Specifications

Thread support library

Threads
thread (C++11)
hardware_destructive_interference_sizehardware_constructive_interference_size (C++17)(C++17)
this_thread namespace
get_id (C++11) yield (C++11)	sleep_for (C++11) sleep_until (C++11)
Mutual exclusion
mutex (C++11) recursive_mutex (C++11) shared_mutex (C++17)	timed_mutex (C++11) recursive_timed_mutex (C++11) shared_timed_mutex (C++14)
Generic lock management
lock_guard (C++11) scoped_lock (C++17) unique_lock (C++11) shared_lock (C++14) defer_lock_ttry_to_lock_tadopt_lock_t (C++11)(C++11)(C++11)	lock (C++11) try_lock (C++11) defer_locktry_to_lockadopt_lock (C++11)(C++11)(C++11) once_flag (C++11) call_once (C++11)
Condition variables
condition_variable (C++11)
condition_variable_any (C++11)
notify_all_at_thread_exit (C++11)
cv_status (C++11)
Futures
promise (C++11) future (C++11) shared_future (C++11) packaged_task (C++11) async (C++11)	launch (C++11) future_status (C++11) future_error (C++11) future_category (C++11) future_errc (C++11)

Defined in header <thread>
void yield() noexcept;		(since C++11)

Provides a hint to the implementation to reschedule the execution of threads, allowing other threads to run.

Parameters

(none)

Return value

(none)

Notes

The exact behavior of this function depends on the implementation, in particular on the mechanics of the OS scheduler in use and the state of the system. For example, a first-in-first-out realtime scheduler (SCHED_FIFO in Linux) would suspend the current thread and put it on the back of the queue of the same-priority threads that are ready to run (and if there are no other threads at the same priority, yield has no effect).

Example

Run this code

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

// "busy sleep" while suggesting that other threads run 
// for a small amount of time
void little_sleep(std::chrono::microseconds us)
{
    auto start = std::chrono::high_resolution_clock::now();
    auto end = start + us;
    do {
        std::this_thread::yield();
    } while (std::chrono::high_resolution_clock::now() < end);
}

int main()
{
    auto start = std::chrono::high_resolution_clock::now();

    little_sleep(std::chrono::microseconds(100));

    auto elapsed = std::chrono::high_resolution_clock::now() - start;
    std::cout << "waited for "
              << std::chrono::duration_cast<std::chrono::microseconds>(elapsed).count()
              << " microseconds\n";
}

Possible output:

waited for 128 microseconds