Unusual Speed Difference between Python and C++

Question

I recently wrote a short algorithm to calculate happy numbers in python. The program allows you to pick an upper bound and it will determine all the happy numbers below it.

Answer 1

Other optimizations: by using arrays and direct access using the loop index rather than searching in a vector, and by caching prior sums, the following code (inspired by Dr Asik's answer but probably not optimized at all) runs 2445 times faster than the original C++ code, about 400 times faster than the Python code.

#include 
#include 
#include 

void calcMain(int upperBound, std::vector& known)
{
    int tempDigitCounter = upperBound;
    int numDigits = 0;
    while (tempDigitCounter > 0)
    {
        numDigits++;
        tempDigitCounter /= 10;
    }
    int maxSlots = numDigits * 9 * 9;
    int* history = new int[maxSlots + 1];

    int* cache = new int[upperBound+1];
    for (int jj = 0; jj <= upperBound; jj++)
    {
        cache[jj] = 0;
    }

    int current, sum, temp;
    for(int i = 0; i <= upperBound; i++)
    {
        current = i;
        while(true)
        {
            sum = 0;
            temp = current;

            bool inRange = temp <= upperBound;
            if (inRange)
            {
                int cached = cache[temp];
                if (cached)
                {
                    sum = cached;
                }
            }

            if (sum == 0)
            {
                while (temp > 0)
                {
                    int tempMod = temp % 10;
                    sum += tempMod * tempMod;
                    temp /= 10;
                }
                if (inRange)
                {
                    cache[current] = sum;
                }
            }
            current = sum;
            if(history[current] == i)
            {
                if(current == 1)
                {
                    known.push_back(i);
                }
                break;
            }
            history[current] = i;
        }
    }
}

int main()
{
    while(true)
    {
        int upperBound;
        std::vector known;
        std::cout << "Pick an upper bound: ";
        std::cin >> upperBound;
        long start, end;
        start = GetTickCount();
        calcMain(upperBound, known);
        end = GetTickCount();
        for (size_t i = 0; i < known.size(); ++i) {
            std::cout << known[i] << ", ";
        }               
        double seconds = (double)(end-start) / 1000.0;
        std::cout << std::endl << seconds << " seconds." << std::endl << std::endl;
    }
    return 0;
}