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purpose for wait_for function in condition variable - C++11


By : user2176045
Date : October 14 2020, 02:22 PM
Hope that helps The use case for this is if you want to wait for an event to occur, but not indefinitely.
Maybe after the timeout expired, you want to notify the user that obtaining the result takes longer than expected. Maybe you want to trigger cancellation of the task providing the result.
code :


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C++ condition variable wait_for not behaving as expected


By : stefan
Date : March 29 2020, 07:55 AM
will be helpful for those in need This sounds like a bug in your vendor's implementation. I don't see how this test can fail.
Fwiw, your REQUIRE statement can be greatly simplified:
code :
REQUIRE(end - start >= rel_time);
static_assert(std::chrono::steady_clock::duration{1} <= std::chrono::milliseconds{1},
    "This steady_clock implementation has an outrageously coarse duration");

condition.wait_for intellisense error


By : ravikiran shenoy
Date : March 29 2020, 07:55 AM
will help you As Bo says, there are 2 versions of the function. I'm going to assume there was a typo in the example and it meant to use the version of the function with three parameters, here's some working code, I don't know if it works in the same way as the example intended.
if (condition.wait_for(std::unique_lock(mut), std::chrono::seconds(3), [] {return true; }))

Is a condition variable's .wait_for() an efficient way to perform a background task at a specific interval?


By : ksihlanick
Date : March 29 2020, 07:55 AM
will help you I need to run an activity every so often while my program is running. In production code this is configurable with a default of 30 minutes, but in the example below I've used 5 seconds. Previously I had a std::thread that would loop once per second checking to see if it was time to run the activity OR if the program was closed. This allowed me to close the program at any time without having the .join() on the activity's thread block my application's exit waiting for its next iteration. At any moment it was less than a second away from checking to see if it should close or perform the activity. , Your code has a few issues with it.
code :
void RunThread()
{
  asking_thread_to_quit = false;
  std::cout << "Started RunThread." << std::endl;
  while(true)
  {
    std::unique_lock<std::mutex> lock(cv_mutex);
    std::chrono::seconds delay(5);
    if(cv.wait_for(lock, delay, [] { std::cout << "WAKEUP" << std::endl; return asking_thread_to_quit; })) // timed out
    {
      std::cout << "Breaking RunThread Loop." << std::endl;
      break;
    }
    else
    {
      std::cout << "TIMER CODE!" << std::endl;
    }
  }
}
asking_thread_to_quit = true;
cv.notify_all();
std::unique_lock<std::mutex> lock_cv() {
  return std::unique_lock<std::mutex>(cv_mutex);
}
void RunThread()
{
  {
    auto lock = lock_cv();
    asking_thread_to_quit = false;
  }

  std::cout << "Started RunThread." << std::endl;
  while(true)
  {
    {
      auto lock = lock_cv();
      using namespace std::literals::chrono_literals;
      if(cv.wait_for(lock, 5s, [] { std::cout << "WAKEUP" << std::endl; return asking_thread_to_quit; })) // timed out
      {
        std::cout << "Breaking RunThread Loop." << std::endl;
        break;
      }
    }         
    std::cout << "TIMER CODE!" << std::endl;
  }
}
{
  auto lock = lock_cv();
  asking_thread_to_quit = true;
}
cv.notify_all();

Purpose of asyncio.wait_for()


By : Doyoung Park
Date : March 29 2020, 07:55 AM
may help you . The wait_for adds timeout. For example the time for retrieval data from network is too long (let's mock it with async sleep) even worse you could end up only with an error.

gcc bug in condition variable::wait_for


By : Sarbac Ilan
Date : March 29 2020, 07:55 AM
Any of those help It looks like the standard agrees with you that the clock used should be std::chrono::steady_clock.
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