using System; using System.Linq; using System.Collections.Generic; public static class Utils { public static double GetStandardDeviation(this IEnumerable values) { double standardDeviation = 0; int[] enumerable = values as int[] ?? values.ToArray(); int count = enumerable.Count(); if (count > 1) { double avg = enumerable.Average(); double sum = enumerable.Sum(d => (d - avg) * (d - avg)); standardDeviation = Math.Sqrt(sum / count); } return standardDeviation; } class Tuple3 { public Tuple3(X x, Y y, Z z) { this.Item1 = x; this.Item2 = y; this.Item3 = z; } public static Tuple3 Create(X x, Y y, Z z) { return new Tuple3(x, y, z); } public X Item1; public Y Item2; public Z Item3; } public static Tuple FastStandardDeviation(this IEnumerable values) { var res = values.Aggregate(Tuple3.Create(0d, 0d, 0d), (tup, a) => { var n = tup.Item1 + 1; var delta = a - tup.Item2; var mean = tup.Item2 + delta / n; var delta2 = a - mean; var m2 = tup.Item3 + delta * delta2; tup.Item1 = n; tup.Item2 = mean; tup.Item3 = m2; return tup; }); return Tuple.Create(res.Item1, res.Item2, Math.Sqrt(res.Item3 / res.Item1)); } public static Tuple FastStandardDeviationWithTupleCreate(this IEnumerable values) { var res = values.Aggregate(Tuple.Create(0d, 0d, 0d), (tup, a) => { var n = tup.Item1 + 1; var delta = a - tup.Item2; var mean = tup.Item2 + delta / n; var delta2 = a - mean; var m2 = tup.Item3 + delta * delta2; return Tuple.Create(n, mean, m2); }); return Tuple.Create(res.Item1, res.Item2, Math.Sqrt(res.Item3 / res.Item1)); } } public static class UtilsT { public static Tuple Time(Func act) { var watch = System.Diagnostics.Stopwatch.StartNew(); var t = act(); watch.Stop(); return Tuple.Create(watch.ElapsedMilliseconds, t); } } class MainClass { static void Main() { var rand = new Random(); var nums = Enumerable.Range(1, 10000000).Select(_ => rand.Next(1000)); var slow = UtilsT.Time(nums.GetStandardDeviation); Console.WriteLine("Slow Method, Result = {0}, Time = {1}", slow.Item2, slow.Item1); var fast = UtilsT>.Time(nums.FastStandardDeviation); Console.WriteLine("Fast Method, Result = {0}, Time = {1}", fast.Item2.Item3, fast.Item1); } }

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