Simple for() loop benchmark takes the same time with any loop bound

Question

I\'m willing to write a code that makes my CPU execute some operations and see how much time does he take to solve them. I wanted to make a loop going from i=0 to i<5000

Answer 1

I slightly altered your code to be the following:

#include 
#include 

using namespace std;

int main() {
    for (long long int j = 10000000; j <= 10000000000; j = j * 10) {

        int start_s = clock();

        for (long long int i = 0; i < j; i++) {
            i * 434243;
        }

        int stop_s = clock();

        cout << "time: " << (stop_s - start_s) / double(CLOCKS_PER_SEC) * 1000 << endl;
    }

    int k;
    cin >> k;
    return 0;
}

Output: (Which looks perfectly fine to me.)

time: 23
time: 224
time: 2497
time: 21697

There is one thing to be aware of. Since i is an integer, it never will be equal to 49058349083 anyways. In your case upper bound is converted to int which corresponds to anything between -2,147,483,648 and 2,147,483,647 so loop runs anything between 0 and 2,147,483,647 times which is not that big of a number for a simple multiplication operation. (1813708827 in case of 49058349083).

Try using long long int which can be between -2^63 and 2^63-1