What is a mutex and how do I implement it in my code?

What is a mutex and how do I implement it in my code?

A mutex, or mutual exclusion, is a synchronization primitive used to prevent concurrent access to a shared resource. To implement it, you typically use a mutex library available in your programming language. For example, in C++, you can use the <mutex> header.

Can you show me a simple example in C++?

Sure! Here's a basic example:

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

std::mutex mtx;

void printNumbers(int id) {
    mtx.lock(); // Lock the mutex
    for (int i = 0; i < 5; ++i) {
        std::cout << "Thread " << id << ": " << i << std::endl;
    }
    mtx.unlock(); // Unlock the mutex
}

int main() {
    std::thread t1(printNumbers, 1);
    std::thread t2(printNumbers, 2);
    t1.join();
    t2.join();
    return 0;
}

This code creates two threads that print numbers while ensuring that only one thread accesses the output at a time.

What happens if I forget to unlock the mutex?

If you forget to unlock the mutex, it can lead to a deadlock situation where other threads are unable to acquire the mutex and get stuck waiting indefinitely. This can cause your program to hang.

Are there any alternatives to using mutexes?

Yes, alternatives include using read-write locks, semaphores, or lock-free data structures, depending on your specific use case and performance requirements.