C++ STD Asynchronous

cpp_std_async.cpp

#include <iostream>
#include <vector>
#include <future>

int main(int argc, char const *argv[])
{
	auto fn_sync = [](int v)
	{
		std::cout << v << std::endl;
		std::this_thread::sleep_for(std::chrono::seconds(1));
	};

	const auto start = std::chrono::high_resolution_clock::now();
	{
		// Sync - 1s

		fn_sync(-1);

		// Async For - 3s

		const int nasync = 3;

		std::vector<std::future<void>> futures;

		for (int i = 0; i < nasync; ++i)
		{
			auto fn_async = std::async(std::launch::async, fn_sync, i); // std::launch::deferred
			futures.push_back(std::move(fn_async));
		}

		for (auto& future : futures)
		{
			future.wait();
		}

		// Async Each - 3s

		auto v1 = std::async(std::launch::async, fn_sync, 0);
		auto v2 = std::async(std::launch::async, fn_sync, 1);
		auto v3 = std::async(std::launch::async, fn_sync, 2);

		v1.wait();
		v2.wait();
		v3.wait();
	}
	const auto finish = std::chrono::high_resolution_clock::now();

	std::chrono::duration<double> elapsed = finish - start;
	std::cout << "Total " << elapsed.count() << " seconds" << std::endl;

	return 0;
}

/**
 * -1
 * 0
 * 1
 * 2
 * 0
 * 1
 * 2
 * Total 3.00961 seconds
*/