What are condition variables?

Condition variables are synchronization primitives that allow threads to wait until a certain condition is met. They are typically used in scenarios where one or more threads need to be notified by another thread when a certain condition becomes true.

Using condition variables with std::jthread

To use condition variables with std::jthread, we first need to include the <condition_variable> header:

#include <condition_variable>

Next, we can declare a condition variable object and a mutex to protect access to it:

std::condition_variable cv;
std::mutex mutex;

In a real-world scenario, we might have a producer thread that produces data and a consumer thread that consumes the data. The producer thread should signal the consumer thread when new data is available. We can achieve this using a condition variable:

std::jthread producer([&]{
    // Produce data
    while (true) {
        std::unique_lock<std::mutex> lock(mutex);
        // Produce data
        cv.notify_one(); // Notify consumer
    }
});

std::jthread consumer([&]{
    // Consume data
    while (true) {
        std::unique_lock<std::mutex> lock(mutex);
        cv.wait(lock); // Wait for notification from producer
        // Consume data
    }
});

In the producer thread, we use std::unique_lock to lock the mutex and notify the consumer thread using cv.notify_one(). This will wake up a single consumer thread that is waiting on the condition variable.

In the consumer thread, we also use std::unique_lock to lock the mutex, but this time we use cv.wait(lock) to wait for the notification from the producer thread. This will release the lock and put the consumer thread to sleep until the notification is received.

Conclusion

Using condition variables with std::jthread provides a simple and efficient way to synchronize the execution of multiple threads. By using condition variables, we can ensure that threads wait until a certain condition becomes true before proceeding. This can greatly simplify concurrent programming and improve the performance of multi-threaded applications.

By incorporating condition variables into your std::jthread code, you can effectively manage thread synchronization and coordination, resulting in more efficient and reliable concurrent programs.

#C++ #Multithreading