setting the execution rate of while loop in a C++ code for real time synchronization

Simple and accurate solution with std::this_thread::sleep_until:

#include "date.h"
#include <chrono>
#include <iostream>
#include <thread>

int
main()
{
    using namespace std::chrono;
    using namespace date;
    auto next = steady_clock::now();
    auto prev = next - 200ms;
    while (true)
    {
        // do stuff
        auto now = steady_clock::now();
        std::cout << round<milliseconds>(now - prev) << '\n';
        prev = now;

        // delay until time to iterate again
        next += 200ms;
        std::this_thread::sleep_until(next);
    }
}

"date.h" isn't needed for the delay part. It is there to provide the round<duration> function (which is now in C++17), and to make it easier to print out durations. This is all under "do stuff", and doesn't matter for the loop delay.

Just get a chrono::time_point, add your delay to it, and sleep until that time_point. Your loop will on average stay true to your delay, as long as your "stuff" takes less time than your delay. No other thread needed. No timer needed. Just <chrono> and sleep_until.

This example just output for me:

200ms
205ms
200ms
195ms
205ms
198ms
202ms
199ms
196ms
203ms
...