Ongoing Optimisation with CppMem

I start with a small program and improve it successively. I verify each step of my process with CppMem. CppMem is an interactive tool for exploring the behaviour of small code snippets using the C++ memory model.

First, here is the small program.

The reference program for the ongoing optimisation

 1 // ongoingOptimisation.cpp
 2 
 3 #include <iostream>
 4 #include <thread>
 5 
 6 int x = 0;
 7 int y = 0;
 8 
 9 void writing(){
10   x = 2000;
11   y = 11;
12 }
13 
14 void reading(){ 
15   std::cout << "y: " << y << " ";
16   std::cout << "x: " << x << std::endl;
17 }
18 
19 int main(){
20   std::thread thread1(writing);
21   std::thread thread2(reading);
22   thread1.join();
23   thread2.join();
24 }

The program is quite simple. It consists of the two threads thread1 and thread2. thread1 writes the values x and y. thread2 reads the values x and y in the opposite sequence...