September Morn Update

Task/Arithmetic-geometric-mean/Visual-Basic-.NET/arithmetic-geometric-mean.visual

@@ -0,0 +1,39 @@
+Imports System
+Imports System.Numerics
+
+Module Module1
+        Function BIP(ByVal leadDig As Char, ByVal numDigs As Integer) As BigInteger
+            Return BigInteger.Parse(leadDig & New String("0", numDigs))
+        End Function
+
+        Function IntSqRoot(ByVal v As BigInteger) As BigInteger
+            Dim digs As Integer = Math.Max(0, v.ToString().Length / 2)
+            Dim term As BigInteger : IntSqRoot = BIP("3", digs)
+            While True
+                term = v / IntSqRoot
+                If Math.Abs(CDbl((term - IntSqRoot))) < 2 Then Exit While
+                IntSqRoot = (IntSqRoot + term) / 2
+            End While
+        End Function
+
+        Function CalcByAGM(ByVal digits As Integer) As BigInteger
+            Dim digs As Integer = digits + CInt((Math.Log(digits) / 2)), c As BigInteger,
+                d2 As Integer = digs * 2,
+                a As BigInteger = BIP("1", digs) ' initial value = 1
+            CalcByAGM = IntSqRoot(BIP("5", d2 - 1)) ' initial value = square root of 0.5
+            While True
+                c = a : a = ((a + CalcByAGM) / 2) : CalcByAGM = IntSqRoot(c * CalcByAGM)
+                If Math.Abs(CDbl((a - CalcByAGM))) <= 1 Then Exit While
+            End While
+        End Function
+
+        Sub Main(ByVal args As String())
+            Dim digits As Integer = 25000
+            If args.Length > 0 Then
+                Integer.TryParse(args(0), digits)
+                If digits < 1 OrElse digits > 999999 Then digits = 25000
+            End If
+            Console.WriteLine("0.{0}", CalcByAGM(digits).ToString())
+            If System.Diagnostics.Debugger.IsAttached Then Console.ReadKey()
+        End Sub
+End Module