Random numbers generator

random numbers.linq

<Query Kind="VBProgram">
  <Namespace>System.Security.Cryptography</Namespace>
</Query>

Sub Main

	Dim numRange As Integer = Integer.Parse(Util.ReadLine("Enter how many random numbers you want", "1000000"))
	Dim min As Integer = Integer.Parse(Util.ReadLine("Enter smallest number you want", "0"))
	Dim max As Integer = Integer.Parse(Util.ReadLine("Enter largest number you want", "900"))
	Dim msg As String = $"creating {numRange:n0} random numbers"
	msg.Dump


	Dim sw As New Stopwatch
	sw.Start
	Dim bytes = GetRandomBytes(numRange)
	sw.Stop

	Dim timing = $"Bytes filled in: {sw.Elapsed}"
	timing.Dump

	sw.Restart
	Dim output = ToInt(bytes)
	sw.Stop
	timing = $"Array generated in: {sw.Elapsed}"
	timing.Dump

	sw.Restart
	output = ForceRange(output, min, max)
	sw.Stop
	timing = $"Array forced to range in: {sw.Elapsed}"
	timing.Dump

	Dim byNumber = output.GroupBy(Function(n) n).Select(Function(g) New With {Key .Number = g.Key, Key .Count = g.Count}).OrderByDescending(Function(n) n.Count).ToArray
	byNumber.Dump
	Dim multiples = byNumber.Where(Function(g) g.Count > 1).OrderByDescending(Function(g) g.Count).ThenBy(Function(n) n.Number).ToArray

	msg = $"There are {byNumber.Except(multiples).Count:n0} non repeated numbers that were generated.  {byNumber.Except(multiples).Count / byNumber.Count:P} and {multiples.Count:n0} numbers were repeated.  The numbers ranged between {output.Min} and {output.max}."
	msg &= If(multiples.Count > 0, $"  The smallest number that was reapeated the most is {multiples.First.Number:n0} and was repeated {multiples.First.Count:n0} times.", "")

	msg.Dump


	byNumber.Take(10).Chart(Function(num) num.count, Function(num) num.number, Util.SeriesType.BevelledPie).DumpInline("Top 10 numbers")

End Sub

' Define other methods and classes here

Function ForceRange(numbers As Integer(), Min As Integer, max As Integer) As Integer()

	Return numbers.Select(Function(n) ((n - min) Mod (max + 1 - min) + max + 1 - min) Mod (max + 1 - min) + min).ToArray

End Function

Function ToInt(bytes As Byte()) As Integer()
	Const requiredLen = 4 ' 4 bytes in an int32(vb integer)
	If bytes.Count Mod requiredLen <> 0 Then Throw New ArgumentException($"Must be a Byte() with a length divisible by {requiredLen}")
	Return Enumerable.Range(0, bytes.Count \ 4).
	Select(Function(n) {bytes(n * 4), bytes(n * 4 + 1), bytes(n * 4 + 2), bytes(n * 4 + 3)}).' create batches of (4 byte) arrays
	Select(Function(b) BitConverter.ToInt32(b, 0)).' for each batch convert the bytes into an integer
	ToArray
End Function

Function GetRandomBytes(Size As Integer) As Byte()
	Using rng As RNGCryptoServiceProvider = RNGCryptoServiceProvider.Create
		Dim data = Enumerable.Range(0, size * 4).Select(Function(n) CByte(0)).ToArray ' Array of bytes of the correct size
		rng.GetNonZeroBytes(data) 'bytes filled 
		Return data
	End Using
End Function