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Difference between revisions of "cpp/thread/yield"

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< cpp‎ | thread
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{{cpp/title|n=this_thread::|yield}}
 
{{cpp/title|n=this_thread::|yield}}
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{{cpp/thread/sidebar}}
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{{cpp/thread/navbar}}
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{{ddcl | header=thread | notes={{mark c++11 feature}} | 1=
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{{ddcl|header=thread|since=c++11|1=
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void yield;
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void yield() noexcept;
 
}}
 
}}
  
−
Hints the implementation to reschedule the execution of threads. Another thread may continue execution after the call to this function.  
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Provides a hint to the implementation to reschedule the execution of threads, allowing other threads to run.  
  
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<!-- ======== -->
 
 
===Parameters===
 
===Parameters===
−
{{param none}}
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(none)
  
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<!-- ======== -->
 
 
===Return value===
 
===Return value===
−
{{return none}}
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(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 ({{tt|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, {{tt|yield}} has no effect.
  
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<!-- ======== -->
 
 
===Example===
 
===Example===
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{{example cpp |
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{{example
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| code=
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|code=
−
| output=
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#include <chrono>
 +
#include <iostream>
 +
#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";
 +
}
 +
|p=true
 +
|output=
 +
waited for 128 microseconds
 
}}
 
}}
 +
 +
===See also===
 +
{{dsc begin}}
 +
{{dsc see c|c/thread/thrd_yield}}
 +
{{dsc end}}
 +
 +
{{langlinks|de|es|fr|it|ja|pt|ru|zh}}

Latest revision as of 02:35, 7 October 2024

 
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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.

Contents

[edit] Parameters

(none)

[edit] Return value

(none)

[edit] 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.

[edit] Example

Run this code
#include <chrono>
#include <iostream>
#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

[edit] See also

C documentation for thrd_yield
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