Why does this output 4 times for each ‘for’ iteration - c++

Question

I’m trying to make a basic timer, this code seems to print out the number of milliseconds correctly based on the value in duration
But can someone tell me why it prints the output 4 times for each ‘tick’regardless of what the value of duration is, and how to correct it so that it only outputs once on every ‘tick’ set in duration? I’m sure it must be something simple I’m overlooking but I’m still learning the basics of C++ and I can’t see the error.
I’m running it on the iOS “Mobile C” app, but I don’t imagine that that would be what’s causing the problem.
#include <chrono>
#include <iostream>
int main()
{
using namespace std::chrono;
auto start = high_resolution_clock::now();
int duration = 100;
int i = 0;
while (i <= 100)
{
auto now = high_resolution_clock::now();
auto millis = duration_cast<milliseconds>(now - start).count();
if (millis % duration == 0)
{
std::cout << "millis: " << millis << std::endl;
i++;
}
}
}

Answer 1

Since I'm still new here I can't post a comment but the reason you are getting that output 4 times is because that if statement is true 4 times for that one millisecond on your machine like Jesper Juhl was saying. Consider using a bool to make sure it only runs once. Something like
bool hasRun = false;
if (millis % duration == 0)
{
if (!hasRun)
{
std::cout << "millis: " << millis << std::endl;
hasRun = true;
}
}
else
hasRun = false;
Then you would be able to keep you infinite Arduino simulation loop like you mentioned in the comments but only have the statement ring true once per duration.