double vs int for iteration

gistfile1.cpp

#include <iostream>
#include <chrono>
#include <array>
using namespace std;
using namespace chrono;

std::array<double, 0x1000> a;

void doubletest() {
    double sum = 0;
    for (double i = 0; i < 0x1000; ++i) {
        for (double i = 0; i < 0x1000; ++i) {
            sum += a[i];
        }
    }
    volatile double result = sum;
}

void inttest() {
    double sum = 0;
    for (int i = 0; i < 0x1000; ++i) {
        for (int i = 0; i < 0x1000; ++i) {
            sum += a[i];
        }
    }
    volatile double result = sum;
}

template <typename T>
void Test(T func) {
    milliseconds best = seconds(1000);
    for (int i = 0x40; i; --i) {
        auto a = high_resolution_clock::now();
        func();
        auto b = high_resolution_clock::now();
        auto dif = duration_cast<milliseconds>(b - a);
        if (dif < best)
            best = dif;
    }
    cout << best.count() << "ms" << endl;
}

int main() {
    a.fill(1);
    Test(doubletest);
    Test(inttest);
}