hr0nix

#include <vector>
#include <iostream>
#include <windows.h>

using namespace std;

template<class IteratorType> double CalculateMean(IteratorType begin, IteratorType end)
{
        double sum = 0;
        int count = 0;

        for(IteratorType it = begin; it != end; ++it)
        {
                sum += (*it);
                count += 1;
        }

        return sum / count;
}

template<class IteratorType> double CalculateVariance(IteratorType begin, IteratorType end)
{
        double mean = CalculateMean(begin, end);
        double sum = 0;
        int count = 0;

        for(IteratorType it = begin; it != end; ++it)
        {
                double value = *it;
                sum += (value - mean) * (value - mean);
                count += 1;
        }

        return sum / count;
}

double GenerateUniformDouble()
{
        return rand() / static_cast<double>(RAND_MAX);
}

int _tmain(int argc, _TCHAR* argv[])
{
        const int SampleCount = 50000000;
        std::vector<double> collection(SampleCount);
        for (std::vector<double>::iterator it = collection.begin(); it != collection.end(); ++it)
                (*it) = GenerateUniformDouble();

        DWORD startTime = GetTickCount();
        double mean = CalculateMean(collection.begin(), collection.end());
        double variance = CalculateVariance(collection.begin(), collection.end());
        DWORD elapsedTime = GetTickCount() - startTime;

        double timeInSec = elapsedTime / 1000.0;
        std::cout << "C++ mean: " << mean << " var: " << variance << " time: " << timeInSec << std::endl;

        return 0;
}