using System;

using System.Diagnostics;

public class Program

{

    public static int ITER  = 5000;

    public static int N = 100000;

    public static double[] TestArr = new double[N];

    public static double MAX = 100.0d;

    public static double MIN = -100.0d;

    public static void Main()

    {

        // initialize test array

        var randNum = new Random();

        for (int i = 0; i < TestArr.Length; i++)

        {

            TestArr[i] = randNum.NextDouble() * (MAX - MIN) + MIN;

        }

        // start benchmark

        Benchmark("SumNotUnroll", SumNotUnroll, ITER);

        Benchmark("SumUnroll", SumUnroll, ITER);

        Benchmark("SumUnroll2", SumUnroll2, ITER);

    }

    public static void Benchmark(string testName, Action act, int iterations)

    {

        GC.Collect();

        act.Invoke(); // run once outside of loop to avoid initialization costs

        var sw = Stopwatch.StartNew();

        for (int i = 0; i < iterations; i++)

        {

            act.Invoke();

        }

        sw.Stop();

        Console.WriteLine("{0}: {1}", testName, new TimeSpan(sw.ElapsedTicks / iterations));

    }

    public static void SumNotUnroll()

    {

        double sum = 0;

        for (int i = 0; i < N; ++i)

        {

            sum += TestArr[i];

        }

    }

    public static void SumUnroll()

    {

        double sum = 0;

        for (int i = 0; i < N; i+=2)

        {

            sum += TestArr[i];

            sum += TestArr[i+1];

        }

    }

    public static void SumUnroll2()

    {

        double sum = 0;

        for (int i = 0; i < N; i+=2)

        {

            var s = TestArr[i] + TestArr[i+1];

            sum += s;

        }

    }

}