iterative.cpp

int main() 
{
    std::chrono::time_point< std::chrono::system_clock > startTime;
    std::chrono::duration< double, std::milli > elapsedTime;

    for (int i = 0; i < MAX_VALUE; i += 10000000) {
        startTime = std::chrono::system_clock::now();
        for (int j = 0; j < REPEAT; ++j) {
            //call the function
            int result = fib(i);
        }
        elapsedTime = std::chrono::system_clock::now() - startTime;
        double avg = elapsedTime.count() / REPEAT;
        std::cout << avg << '\n';
    }
}

recursive.cpp

int main() 
{
    std::chrono::time_point< std::chrono::system_clock > startTime;
    std::chrono::duration< double, std::milli > elapsedTime;

    for (int i = 0; i < MAX_VALUE; ++i) {
        startTime = std::chrono::system_clock::now();
        //call the function
        int result = fib(i);
        elapsedTime = std::chrono::system_clock::now() - startTime;
        std::cout << elapsedTime.count() << '\n';
    }
}