Data commit

Task/Arithmetic-geometric-mean/C-sharp/arithmetic-geometric-mean-1.cs

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+namespace RosettaCode.ArithmeticGeometricMean
+{
+    using System;
+    using System.Collections.Generic;
+    using System.Globalization;
+
+    internal static class Program
+    {
+        private static double ArithmeticGeometricMean(double number,
+                                                      double otherNumber,
+                                                      IEqualityComparer<double>
+                                                          comparer)
+        {
+            return comparer.Equals(number, otherNumber)
+                       ? number
+                       : ArithmeticGeometricMean(
+                           ArithmeticMean(number, otherNumber),
+                           GeometricMean(number, otherNumber), comparer);
+        }
+
+        private static double ArithmeticMean(double number, double otherNumber)
+        {
+            return 0.5 * (number + otherNumber);
+        }
+
+        private static double GeometricMean(double number, double otherNumber)
+        {
+            return Math.Sqrt(number * otherNumber);
+        }
+
+        private static void Main()
+        {
+            Console.WriteLine(
+                ArithmeticGeometricMean(1, 0.5 * Math.Sqrt(2),
+                                        new RelativeDifferenceComparer(1e-5)).
+                    ToString(CultureInfo.InvariantCulture));
+        }
+
+        private class RelativeDifferenceComparer : IEqualityComparer<double>
+        {
+            private readonly double _maximumRelativeDifference;
+
+            internal RelativeDifferenceComparer(double maximumRelativeDifference)
+            {
+                _maximumRelativeDifference = maximumRelativeDifference;
+            }
+
+            public bool Equals(double number, double otherNumber)
+            {
+                return RelativeDifference(number, otherNumber) <=
+                       _maximumRelativeDifference;
+            }
+
+            public int GetHashCode(double number)
+            {
+                return number.GetHashCode();
+            }
+
+            private static double RelativeDifference(double number,
+                                                     double otherNumber)
+            {
+                return AbsoluteDifference(number, otherNumber) /
+                       Norm(number, otherNumber);
+            }
+
+            private static double AbsoluteDifference(double number,
+                                                     double otherNumber)
+            {
+                return Math.Abs(number - otherNumber);
+            }
+
+            private static double Norm(double number, double otherNumber)
+            {
+                return 0.5 * (Math.Abs(number) + Math.Abs(otherNumber));
+            }
+        }
+    }
+}

Task/Arithmetic-geometric-mean/C-sharp/arithmetic-geometric-mean-2.cs

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+using System;
+ 
+class Program {
+ 
+    static Decimal DecSqRoot(Decimal v) {
+        Decimal r = (Decimal)Math.Sqrt((double)v), t = 0, d = 0, ld = 1;
+        while (ld != d) { t = v / r; r = (r + t) / 2;
+            ld = d; d = t - r; } return t; }
+ 
+    static Decimal CalcAGM(Decimal a, Decimal b) {
+        Decimal c, d = 0, ld = 1; while (ld != d) { ld = d; c = a;
+            d = (a = (a + b) / 2) - (b = DecSqRoot(c * b)); } return b; }
+ 
+    static void Main(string[] args) {
+        Console.WriteLine(CalcAGM(1M, DecSqRoot(0.5M)));
+        if (System.Diagnostics.Debugger.IsAttached) Console.ReadKey();
+    }
+}

Task/Arithmetic-geometric-mean/C-sharp/arithmetic-geometric-mean-3.cs

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+using static System.Math;
+using static System.Console;
+using BI = System.Numerics.BigInteger;
+
+class Program {
+
+    static BI BIP(char leadDig, int numDigs) { // makes big constant
+        return BI.Parse(leadDig + new string('0', numDigs)); }
+
+    static BI IntSqRoot(BI v, BI res) { // res is the initial guess
+        BI term = 0, d = 0, dl = 1; while (dl != d) { term = v / res; res = (res + term) >> 1;
+            dl = d; d = term - res; } return term; }
+
+    static BI CalcByAGM(int digs) { // note: a and b are hard-coded for this RC task
+        BI a = BIP('1', digs), // value of 1, extended to required number of digits
+            b = BI.Parse(string.Format("{0:0.00000000000000000}", Sqrt(0.5)).Substring(2) +
+                new string('0', digs - 17)), // initial guess for square root of 0.5
+            c, // temporary variable to swap a and b
+            diff = 0, ldiff = 1; // difference of a and b, last difference
+        b = IntSqRoot(BIP('5', (digs << 1) - 1), b); // value of square root of 0.5
+        while (ldiff != diff) { ldiff = diff; c = a; a = (a + b) >> 1;
+            diff = a - (b = IntSqRoot(c * b, a)); } return b; }
+
+    static void Main(string[] args) {
+        int digits = 25000; if (args.Length > 0) {
+            int.TryParse(args[0], out digits);
+            if (digits < 1 || digits > 999999) digits = 25000; }
+        WriteLine("0.{0}", CalcByAGM(digits));
+        if (System.Diagnostics.Debugger.IsAttached) ReadKey(); }
+}