Getting random, unique numbers

[TTCEric]

This will be original. I promise.

I cannot get the random number generator to work.

I tried seeding with Date.Now.Milliseconds, it still results in the same values.

What I have are arrays of values.

I get a random index value for each array so I can pull the data from them.

Except the data is similar on every run.

I know its a timing issue because when I step through code, it gives me randoms.

However, is there anything faster than milliseconds that I can seed at?

Here's my code. Please let me know if you need me to explain anything. Basically, i'm creating a random math expression:

#Region "Random Number Generator does not work"
    Private Function RandomExpressionCreateOperand() As String
        'Array of constants 
        Dim szConstants() As String = {"pi", "e"}
        'Array of functions 
        Dim szFunctions() As String = {"Acos", "Asin", "Atan", "Ceiling", "Cos", "Cosh", "Floor", "Log", "Sin", "Sqrt", "Tan"}
        'Array of parameters (proprietary)
        Dim szParameters() As String = {"Parameter1", "Param.eu"}
        'Array of tokens (corresponding to Constant, Fucntion, Parameter or raw value, respectively)
        Dim iTokens() As Integer = {1, 2, 3, 4}
        'Seed random number generator
        Dim rc As New Random(Date.Now.Millisecond)
        'Random number related to token (Constant, Function, Parameter or Value)
        Dim iToken As Integer = rc.Next(1, UBound(iTokens))
        'Return string 
        Dim szRet As String = ""
        'Index of value in the array
        Dim iIndex As Integer = 0
        'Raw value but also parameter of a function token
        Dim iParam As Integer = 0
        'Max value of parameter or raw value: 
        Dim ParamMax As Integer = 999999
        Select Case iToken
            Case 1 'constants
                iIndex = rc.Next(1, UBound(szConstants))
                Debug.Print(iIndex)
                szRet = "{" & szConstants(iIndex) & "}"
            Case 2 'functions 
                iIndex = rc.Next(1, UBound(szFunctions))
                Debug.Print(iIndex)
                szRet = szFunctions(iIndex) & "("
                iParam = rc.Next(1, ParamMax)
                Debug.Print(iParam)
                szRet = szRet & iParam & ")"
            Case 3 'parameters
                iIndex = rc.Next(1, UBound(szParameters))
                Debug.Print(iIndex)
                szRet = "[" & szParameters(iIndex) & "]"
            Case 4 'values
                szRet = rc.Next(1, ParamMax)
                Debug.Print(szRet)
        End Select
        Return szRet
    End Function
    Private Sub RandomExpressionCreate(ByVal DoNotIncludeBadData As Boolean)
        'Random object
        Dim rc As New Random(Date.Now.Millisecond)
 
        'array of operators
        Dim szOperators() As String = {"*", "+", "/", "-", "^"}
 
        'random number for up to 5 operations
        Dim iOperatorCount As Integer = rc.Next(1, 5)
 
        'String parts of random math expression
        Dim szOp1 As String
        Dim szOp2 As String
        Dim szOP As String
        Dim sbExp As New StringBuilder
        Dim iOp As Integer
 
        For x As Integer = 1 To iOperatorCount
            'Operand 1: 
            szOp1 = RandomExpressionCreateOperand()
 
            'Operator:  
            iOp = rc.Next(1, UBound(szOperators))
            szOP = szOperators(iOp)
 
            'Operand 2: 
            szOp2 = RandomExpressionCreateOperand()
 
            'Write expression 
            sbExp.Append(szOp1 & " " & szOP & " " & szOp2)
 
            'Add another operator as long as were not at the end
            If x <> iOperatorCount Then
                iOp = rc.Next(1, UBound(szOperators))
                sbExp.Append(" " & szOperators(iOp) & " ")
            End If
        Next x
 
        'Me.txtExpression.Text = sbExp.ToString
        Debug.Print(sbExp.ToString)
    End Sub
#End Region
 

[TTCEric]

I posted this before but did not get a reply so i'm gonna try it again without diluting with detail.

Real simply put: random numbers are not random even though I seed with time in milliseconds.

Is there some other method to seed or some other concrete randomizer logic that works?

[r035198x]

Yep, programs usually only generate pseudo random numbers. If you want real randomness then you'd have to observe some naturally random activities (like movement of atoms). In practice though pseudo random numbers suffice.

[Curtis Rutland]

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[Plater]

How fast you request "random" numbers also plays a part.
I noticed that if I requested them too fast I would get duplicates.
And I believe if you do NOT provide a seed, it defaults to using the time anyway.

[TTCEric]

How fast you request "random" numbers also plays a part.
I noticed that if I requested them too fast I would get duplicates.
And I believe if you do NOT provide a seed, it defaults to using the time anyway.

Yes. I observed this as well. Stepping through the code, random worked. It was being seeded in milliseconds.

What can I use instead of milliseconds? Evidently, my routines are happening too quickly- before the next millisecond.

My temporary solution will be to store used random numbers but only in such a way as not to duplicate more than a few times. I hope this will delay the operation a bit.

If theres a truer way to handle randoms, please let me know.
I dont know what the other poster mean by using Atomic things. Sorry but thanks for the responses, community.

[Plater]

Use a Thread.Sleep() with a one milisecond wait time?

[r035198x]

If theres a truer way to handle randoms, please let me know.
I dont know what the other poster mean by using Atomic things. Sorry but thanks for the responses, community.

<That was just the .NET village idiot being himself>
It was just an example of how one could get true randomness. The intent was to show that true randomness is very difficult to get in programs and so pseudo random numbers are an acceptable substitute.
</That was just the .NET village idiot being himself>

[TTCEric]

Use a Thread.Sleep() with a one milisecond wait time?

Good suggestion. I'll give it a try. Appreciate it

[IanWright]

Yes. I observed this as well. Stepping through the code, random worked. It was being seeded in milliseconds.

What can I use instead of milliseconds? Evidently, my routines are happening too quickly- before the next millisecond.

My temporary solution will be to store used random numbers but only in such a way as not to duplicate more than a few times. I hope this will delay the operation a bit.

If theres a truer way to handle randoms, please let me know.
I dont know what the other poster mean by using Atomic things. Sorry but thanks for the responses, community.

Can you not try the DateTime.Ticks property instead? This has a greater resolution that miliseconds...

[TTCEric]

Can you not try the DateTime.Ticks property instead? This has a greater resolution that miliseconds...

I like that Ticks uses Nanoseconds (just read about it). I'll see if this works. Thanks for the suggestion.

[Plater]

I like that Ticks uses Nanoseconds (just read about it). I'll see if this works. Thanks for the suggestion.

the Ticks count is the default seed if none is specified I believe