Tag Archives: random

Originally posted to SOAPitStop.com, Jun 25, 2008.

I am sure this is covered somewhere on the great big Internet, but it’s new to me.  And it sucked until I discovered what the problem was.  Basically, I had random values being generated that were anything but random.  “Oh, you forgot to set a seed value to something pseudo-random like now.millisecond.”  No.  That didn’t help.  Check out this code and see what the results are:

    Private Sub UnRandom()
        Dim r As New Random(Now.Millisecond)

        Dim winCount, winCount2 As Integer

        For i As Integer = 1 To 100
            If Rndm() > 50 Then winCount += 1
        Next

        For i As Integer = 1 To 100
            If r.Next(1, 100) > 50 Then winCount2 += 1
        Next

        MsgBox(winCount & ":" & winCount2)

    End Sub

    Private Function Rndm() As Integer
        Dim r As New Random(Now.Millisecond)

        Return r.Next(1, 100)
    End Function

Assuming a 50/50 chance of win, you would expect that a Random.Next would return a random value.  Seemingly not when it gets continually instantiated like in the Rndm function.  So this apparently is not a case where you want all of your variables to be contained in their own methods.  You’d probably want to have one single random number generator for your whole application.