' podonne
' sbrforum
' 10-02-2011

Module BookLayoffSimulation

    Sub Main()
        Randomize(Timer)

        Dim never_layoff As Single = 0.0
        For x = 0 To 100000
            never_layoff += ResolveGame(1 + Rnd() * 100, 1 + Rnd() * 100, Single.MaxValue)
        Next

        Dim sometimes_layoff As Single = 0.0
        For x = 0 To 100000
            sometimes_layoff += ResolveGame(1 + Rnd() * 100, 1 + Rnd() * 100, 2.0)
        Next

        Dim always_layoff As Single = 0.0
        For x = 0 To 100000
            always_layoff += ResolveGame(1 + Rnd() * 100, 1 + Rnd() * 100, 1.0)
        Next

        Console.WriteLine("Book profit with no layoff: $" & never_layoff & ", $" & never_layoff / 100000 & "/game")
        Console.WriteLine("Book profit with layoff when larger is 2x smaller: $" & sometimes_layoff & ", $" & sometimes_layoff / 100000 & "/game")
        Console.WriteLine("Book profit with always layoff any imbalance: $" & always_layoff & ", $" & always_layoff / 100000 & "/game")
        Console.Read()
    End Sub


    Function ResolveGame(ByVal dollars_for As Integer, ByVal dollars_against As Integer, ByVal layoff_limit As Single) As Single
        Dim layoff_dollars = 0.0

        'figureout the larger and smaller amounts, wehther they were for or against doesn't matter after this point
        Dim smaller = Math.Min(dollars_for, dollars_against)
        Dim larger = Math.Max(dollars_for, dollars_against)

        'if the ratio of larger to smaller is greater than the layoff_limit, lay off some of the action
        'layoff_dollars layed off on larger will cause each outcome to be exactly the same
        If larger / smaller > layoff_limit Then layoff_dollars = (layoff_limit - larger / smaller) * smaller

        'calculate the payouts in either event (note that if layoff_dollars is 0.0 then it has no effect
        Dim smaller_payout = smaller + smaller * (10 / 11) + layoff_dollars
        Dim larger_payout = larger + larger * (10 / 11) - layoff_dollars * (10 / 11)

        'resolve the event
        If Rnd() > 0.5 Then
            Return (larger + smaller) - smaller_payout
        Else
            Return (larger + smaller) - larger_payout
        End If

    End Function




End Module