In concurrent programming, semantics and synchronization primitives play a crucial role in ensuring the correct execution and coordination of multiple threads or processes. In C++, there are several ways to acquire these primitives to manage concurrent access to shared resources. In this blog post, we will explore some of the commonly used primitives in C++ for synchronization.

1. Mutex

A mutex (short for mutual exclusion) is a synchronization primitive used to protect shared resources. It ensures that only one thread can access the protected resource at a time. To acquire a mutex in C++, you can use the std::mutex class from the <mutex> header.

Here’s an example of acquiring a mutex and protecting a critical section of code:

#include <mutex>

std::mutex mtx; // Declare a mutex

void criticalSection()
{
    std::unique_lock<std::mutex> lock(mtx); // Acquire the mutex

    // Perform operations on shared resource

    // Mutex automatically released when lock goes out of scope
}

In this example, the std::unique_lock is used to acquire the mutex, ensuring that only one thread can execute the critical section of code at a time.

2. Semaphore

A semaphore is another common synchronization primitive that allows a fixed number of threads to access a shared resource concurrently. In C++, you can use the std::counting_semaphore or std::binary_semaphore classes from the <semaphore> header. However, as of writing this post, the standard semaphore classes are not yet available in the C++ standard library. You can find alternative implementations in various libraries or use platform-specific implementations.

Here’s an example of acquiring a semaphore that allows multiple threads to access the shared resource:

#include <semaphore>

std::counting_semaphore<5> sem(5);  // Declare a semaphore with a maximum count of 5

void sharedResourceAccess()
{
    sem.acquire();  // Acquire the semaphore

    // Perform operations on shared resource

    sem.release();  // Release the semaphore
}

In this example, the sem.acquire() method is used to acquire the semaphore, allowing up to 5 threads to access the shared resource concurrently.

Conclusion

Acquiring semantics and synchronization primitives in C++ is vital for managing concurrent access to shared resources. The mutex and semaphore are two commonly used primitives in this regard. By utilizing these primitives effectively, you can ensure safe and synchronized execution of concurrent programs in C++.

#cplusplus #concurrency