see what resolution a chrono clock has

check_clock_resolution.cpp

#include <future>
#include <atomic>
#include <iostream>
#include <vector>
#include <chrono>

template<typename Clock>
typename Clock::duration
check_clock_resolution() {
	auto s = Clock::now();
	auto e = s;
	//int calls = 0;
	while (true) {
		e = Clock::now();
		//++calls;
		if (e != s) {
			return e - s;
		}
	}
}

void check_clock_resolution_with_n_tasks(int task_count) {
	std::atomic<bool> keep_going = true;

	std::vector<std::future<void>> tasks;
	for (int i = 0; i < task_count; ++i) {
		tasks.push_back(std::async(std::launch::async, [&] {
			while (keep_going.load(std::memory_order_relaxed))
				;
		}));
	}

	std::this_thread::sleep_for(std::chrono::seconds(5));

	auto d = check_clock_resolution<std::chrono::high_resolution_clock>();

	keep_going.store(false, std::memory_order_relaxed);

	for (auto &&t : tasks) {
		t.get();
	}

	std::cout << "With " << task_count << " tasks, the resolution is " <<
		std::chrono::duration_cast<std::chrono::nanoseconds>(d).count() << "ns.\n";
}

// #include <Windows.h>
// #include <mmsystem.h>

int main() {
	// timeBeginPeriod(1);

	for (int i = 1; i < 30; ++i) {
		check_clock_resolution_with_n_tasks(i);
	}
}