Task scheduling is a crucial aspect of any modern application. It allows for efficient utilization of resources and ensures that tasks are executed in a timely manner. In this blog post, we will explore how to implement task scheduling using C++ coroutines.

What are C++ Coroutines?

C++ coroutines are a powerful feature introduced in C++20. They allow for the creation of lightweight threads that can be suspended and resumed at specific points. Coroutines provide a convenient way to write asynchronous code in a sequential manner, improving code readability and maintainability.

Task Scheduling with C++ Coroutines

To implement task scheduling using coroutines, we can leverage the co_await keyword available in C++20. co_await allows us to suspend the execution of a coroutine until a specified condition is met. This is perfect for waiting on tasks to complete before moving on to the next one.

Let’s take a look at an example:

#include <iostream>
#include <experimental/coroutine>

struct task {
    struct promise_type {
        task get_return_object() { return {}; }
        std::experimental::suspend_never initial_suspend() { return {}; }
        std::experimental::suspend_never final_suspend() noexcept { return {}; }
        void return_void() {}
    };
};

task performTask1() {
    // Task 1 implementation
    std::cout << "Performing Task 1..." << std::endl;
    co_await std::experimental::suspend_always{};
    std::cout << "Task 1 completed!" << std::endl;
}

task performTask2() {
    // Task 2 implementation
    std::cout << "Performing Task 2..." << std::endl;
    co_await std::experimental::suspend_always{};
    std::cout << "Task 2 completed!" << std::endl;
}

int main() {
    task t1 = performTask1();
    task t2 = performTask2();
    return 0;
}

In the above code, we define performTask1 and performTask2 as coroutines by returning task from their respective functions. We use co_await std::experimental::suspend_always{}; to suspend the execution of each task until a specific condition is met.

Note that in this simplified example, we’re using suspend_always to indefinitely suspend each task. In a real-world scenario, you would have more meaningful conditions to wait for, such as the completion of an asynchronous operation.

By running the above code, you will see that both tasks are initiated, but their execution is suspended until the main coroutine exits. This is a simple example, but it demonstrates the basic technique of task scheduling using coroutines.

Conclusion

Task scheduling is an essential aspect of modern applications, and C++ coroutines provide an elegant solution for implementing it. By leveraging the co_await keyword and suspending coroutines until specific conditions are met, we can efficiently schedule and manage tasks in a sequential and readable manner.

#cplusplus #coroutines