Чем отличаются подходы std::async и std::thread при организации многопоточности в C++?

std::thread and std::async are two different ways to organize multithreading in C++:

• std::thread is a low-level mechanism for creating and managing threads. You create a thread by passing it a function, and you manage the thread's lifecycle yourself (for example, join or detach). This provides full control but requires careful resource management.

• std::async is a higher-level mechanism that runs a function asynchronously and returns a std::future object. It automatically manages thread creation or uses a thread pool, and simplifies obtaining the result of an asynchronous operation.

Example with std::thread:

#include <thread>
#include <iostream>

void task() {
    std::cout << "Executing task in thread" << std::endl;
}

int main() {
    std::thread t(task);
    t.join();
    return 0;
}

Example with std::async:

#include <future>
#include <iostream>

int compute() {
    return 42;
}

int main() {
    std::future<int> result = std::async(std::launch::async, compute);
    std::cout << "Result: " << result.get() << std::endl;
    return 0;
}

Thus, std::async is convenient for simple task launching with automatic management, while std::thread is used when more fine-grained control over threads is needed.