Can you provide examples of std::async in C++?

Can you provide examples of std::async in C++?

Sure! std::async is used to run tasks asynchronously. Here's a simple example:

#include <iostream>
#include <future>
#include <chrono>

int asyncTask() {
    std::this_thread::sleep_for(std::chrono::seconds(2));
    return 42;
}

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

This code runs asyncTask asynchronously and retrieves the result after waiting.

What happens if I don't use std::launch::async?

If you omit std::launch::async, the implementation may choose to run the task synchronously or asynchronously, depending on the system's current state. It's safer to specify it explicitly if you want to ensure asynchronous execution.

Can I pass parameters to the async function?

Yes, you can pass parameters to the function called by std::async. For example:

int asyncTask(int x) {
    return x * 2;
}

std::future<int> result = std::async(std::launch::async, asyncTask, 21);

This will pass 21 to asyncTask.

Are there any limitations to using std::async?

Yes, some limitations include potential overhead from thread management and the fact that it may not always run in a separate thread if the system decides to run it synchronously. Also, be cautious with shared resources to avoid data races.