What is a condition variable in C++?

What is a condition variable in C++?

A condition variable in C++ is a synchronization primitive that allows threads to wait until a particular condition occurs.

How do I use condition variables in my code?

You can use condition variables with mutexes. First, lock a mutex, then call wait() on the condition variable, and finally signal it when the condition is met.

Can you give me a code example?

Sure! Here's a simple example:

#include <iostream>
#include <thread>
#include <condition_variable>
#include <mutex>

std::condition_variable cv;
std::mutex m;
bool ready = false;

void worker() {
    std::unique_lock<std::mutex> lock(m);
    while (!ready) cv.wait(lock);
    std::cout << "Worker thread is running!" << std::endl;
}

int main() {
    std::thread t(worker);
    { 
        std::lock_guard<std::mutex> lock(m);
        ready = true;
    }
    cv.notify_one();
    t.join();
    return 0;
}

What are the advantages of using condition variables?

Condition variables help avoid busy waiting, allowing threads to sleep until they are notified, which improves efficiency.