using System;
using System.Linq;
using System.Collections.Generic;
public static class Utils {
public static double GetStandardDeviation(this IEnumerable<int> 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<X, Y, Z> {
public Tuple3(X x, Y y, Z z) {
this.Item1 = x;
this.Item2 = y;
this.Item3 = z;
}
public static Tuple3<X, Y, Z> Create(X x, Y y, Z z) {
return new Tuple3<X, Y, Z>(x, y, z);
}
public X Item1;
public Y Item2;
public Z Item3;
}
public static Tuple<Double, Double, Double> FastStandardDeviation(this IEnumerable<int> values) {
var res = values.Aggregate(Tuple3<Double, Double, Double>.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<Double, Double, Double> FastStandardDeviationWithTupleCreate(this IEnumerable<int> 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<T> {
public static Tuple<long, T> Time(Func<T> 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<Double>.Time(nums.GetStandardDeviation);
Console.WriteLine("Slow Method, Result = {0}, Time = {1}", slow.Item2, slow.Item1);
var fast = UtilsT<Tuple<Double, Double, Double>>.Time(nums.FastStandardDeviation);
Console.WriteLine("Fast Method, Result = {0}, Time = {1}", fast.Item2.Item3, fast.Item1);
}
}
