std::atomic usage

// ref:- https://hiroyukichishiro.com/atomic-in-c-language/
// Example code of demonstrating threads with std::atomics
//
#include <iostream>
#include <atomic>
#include <thread>
int data = 0;
volatile std::atomic<bool> ready(false);

// The function will print when it is sure the main thread set the trigger value to true
//
void f()
{
  while (!ready.load(std::memory_order_relaxed)) {
  }
  std::atomic_thread_fence(std::memory_order_acquire);
  std::cout << data << std::endl;
}

// this function will set the value and feedback to the master to print it once done
//
void y()
{
  while (!ready.load(std::memory_order_relaxed)) {
  }
  std::atomic_thread_fence(std::memory_order_acquire);
  std::cout << "\033[32m inside thread == " << data << "\033[0m" << std::endl;
  data = 99;
  std::atomic_thread_fence(std::memory_order_release);
  ready.store(false, std::memory_order_relaxed);
}

int main()
{
  //
  // In this one we wait for the for loop to be complete
  //
  std::thread t(f);
  data = 3;
  std::atomic_thread_fence(std::memory_order_release);

  for (int ii=0; ii<=1000000; ++ii) {
    data = ii;
  }
  ready.store(true, std::memory_order_relaxed);
  t.join();

  //
  // In this one we dont wait for the for loop to be complete
  //
  std::thread x(f);
  data = 3;
  std::atomic_thread_fence(std::memory_order_release);
  ready.store(true, std::memory_order_relaxed);
  for (int ii=0; ii<=1000000; ++ii) {
    data = ii;
  }
  x.join();

  //
  // here we are waiting for the thread to set the atomic to a value and release it
  //
  std::thread z(y);
  std::atomic_thread_fence(std::memory_order_release);
  data = 3;
  ready.store(true, std::memory_order_relaxed);
  while (ready.load(std::memory_order_relaxed)) {
  }
  std::atomic_thread_fence(std::memory_order_acquire);
  std::cout << data << std::endl;
  z.join();

  //
  // here we dont care about the thread before we print the atomic value
  //
  std::thread zz(y);
  std::atomic_thread_fence(std::memory_order_release);
  ready.store(true, std::memory_order_relaxed);
  data = 3;
  std::cout << data << std::endl;
  data = 6;
  zz.join();

}