Compare list-summation code using different list structures.

gistfile1.cs

using System;
using System.Collections.Generic;
using System.Diagnostics;

namespace pointers
{
    class MainClass
    {
        private const int Iterations = 500000;
        private const int Length = 10000;

        private static void Initialize (IList<double> one, IList<double> two)
        {
            var rand = new Random ();

            for (var i = 0; i < one.Count; ++i) {
                one [i] = Math.Floor (rand.NextDouble () * 100);
            }

            for (var i = 0; i < two.Count; ++i) {
                two [i] = Math.Floor (rand.NextDouble () * 100);
            }
        }

        unsafe private static void SumUnsafeArrays (out TimeSpan duration)
        {
            var array1 = new double[Length];
            var array2 = new double[Length];
            
            Initialize (array1, array2);
            
            var sw = new Stopwatch ();
            
            sw.Start ();

            for (var i = 0; i < Iterations; ++i) {
                fixed (double *a1 = array1)
                fixed (double *a2 = array2) {
                    double* src = a1,
                            dst = a2,
                            end = a1 + array1.Length;

                    while (src != end) {
                        *dst = *src;
                        dst++;
                        src++;
                    }
                }
            }

            sw.Stop ();

            duration = sw.Elapsed;
        }

        private static void SumSafeArrays (out TimeSpan duration)
        {
            var array1 = new double[Length];
            var array2 = new double[Length];
            var array3 = new double[Length];

            Initialize (array1, array2);

            var sw = new Stopwatch ();

            sw.Start ();

            for (var i = 0; i < Iterations; ++i) {
                for (var j = 0; j < array1.Length; ++j) {
                    array3[j] = array1[j] + array2[j];
                }
            }

            sw.Stop ();

            duration = sw.Elapsed;
        }

        private static void SumLists (out TimeSpan duration)
        {
            var list1 = new List<double> (Length);
            var list2 = new List<double> (Length);

            Initialize (list1, list2);

            var sw = new Stopwatch ();

            sw.Start ();

            for (var i = 0; i < Iterations; ++i) {
                var list3 = new List<double> (Length);

                for (var j = 0; j < list1.Count; ++j) {
                    list3.Add (list1 [j] + list2 [j]);
                }
            }

            sw.Stop ();

            duration = sw.Elapsed;
        }

        public static void Main (string[] args)
        {
            TimeSpan lists, safeArray, unsafeArray;

            SumLists(out lists);
            SumSafeArrays(out safeArray);
            SumUnsafeArrays(out unsafeArray);

            Console.WriteLine ("Timings: {0} iterations of {1}-item lists", Iterations, Length);
            Console.WriteLine ("  Lists:           {0}", lists);
            Console.WriteLine ("  Arrays (safe):   {0}", safeArray);
            Console.WriteLine ("  Arrays (unsafe): {0}", unsafeArray);
        }
    }
}