randomize 1 to 80 numbers better than the Randomize function vb6

[isnoend07]

I have created a keno game that selects 20 numbers out of 80 using the Randomize function.
The program also tracks which numbers have been selected the most.
after running the app hundreds of thousands of times on different computers i have determined that the Randomize function is not truly random.
for instance Runs: 219,098 Numbers 1 to 80
these numbers are always at the the top of the list, but not always in the same exact order
on different computers
53 58054
40 57993
52 57957
49 57948
54 57909
39 57883
55 57864
37 57860
35 57847
36 57823
33 57735
The numbers 70 to 80 are always at the bottom of the list
eg
77 51991
78 51950
80 51940
70 51842
71 51785
79 51381
72 51087
73 50876
74 50604
76 50504
75 50389
how can i correct this ?
using vb6

[SamOscarBrown]

What's your seed? Most randomizers are not true random number generators, but pseudo ones. If you seed your function with your computer clock, which measures time in milliseconds, you probably won't see the same numbers repeating in the small amount of times you run the program (relatively).

[Code Doc]

Shuffle all the integers from 1 to 80 using the Knuth shuffle and then select the first 20.

[isnoend07]

Don't know what seed is. Hired a coder to write the code. it looks like this:
Const DRAWN_NUMBERS As Integer = 20
For i = 1 To DRAWN_NUMBERS
Randomize
thisIndex = Int(((80 - i) * Rnd) + 1)
DrawnNumber(i) = CandidateNumber(thisIndex)

[jmcilhinney]

The issue may well the fact that Randomize is being used inside the loop. Why is it that so many people don't seem to know how to do such a simple thing properly? Randomize is supposed to be used once and once only. It initialises the random number generator. You then call Rnd repeatedly and it will return the next number in the pseudo-random sequence. That sequence is plenty random enough for the vast majority of cases, if used properly.

[Code Doc]

Try building a form with a command button and a list box. Then apply this code:

Dim Nums() As Integer, Temp As Integer
Dim RangeLimit As Integer, SwapValue As Integer
Const PoolSize = 80, Draws = 20

Private Sub Command1_Click()
RangeLimit = PoolSize
Do While RangeLimit > 1
    Do
        SwapCount = SwapCount + 1
        Temp = Int(Rnd * RangeLimit) + 1
        If Temp <> RangeLimit Then Exit Do
    Loop
    SwapValue = Nums(Temp)
    Nums(Temp) = Nums(RangeLimit)
    Nums(RangeLimit) = SwapValue
    RangeLimit = RangeLimit - 1
Loop
List1.Clear
For I = 1 To Draws
    List1.AddItem Str$(Nums(I))
Next
End Sub

Private Sub Form_Load()
Randomize
ReDim Nums(PoolSize)
For I = 1 To PoolSize
    Nums(I) = I
Next
End Sub

[isnoend07]

i noticed you put the randomize in the form load. my program can be ran thousands of times and each time it produces 20 random numbers.
Would it not need to be called before each run ?

[si_the_geek]

No, it should only be called once in total - unless you have specific requirements (such as generating lists of numbers that you can repeat later).

[isnoend07]

No, it should only be called once in total - unless you have specific requirements (such as generating lists of numbers that you can repeat later).

Don't understand
app gets loaded
Pressing the start button selects 20 random numbers
Pressing start again the 20 numbers are erased and another 20 are randomly selected
Repeat, repeat etc
i noticed the randomize was inside a loop so i changed it to randomize before each start

[si_the_geek]

Rather than randomize before each start, just call it once in total (in Form_Load etc). The results are "more random" that way.

[Doogle]

I'm no statistician but I think, simply put, it goes something like this:

The VB Random Number Generator is actually a Pseudo Random Number Generator which is a Random distribution of 16,777,215 numbers. Initial seeding (Randomize) effectively 'points' the Generator at one of the numbers in the distribution from where it will start. The initial seed is derived from the system time (to 1mS). Calls to Rnd() select the next random number, the previous random number being the seed for the next. etc. Clearly, the more random the seed the more random the result.

If you change the seed for the next number, by calling Randomize again, then the seed is less random; the time may not have moved on, given the speed of CPUs these days you could be in the same milli-second as you were before, so you would just start at the same point. Even if it has moved on you will be re-seeding 'sequentially increasing' rather than randomly, since, by definition, time goes forwards rather than backwards, instead of re-seeding with any of the 16,777,215 possible values, you will always be re-seeding with a number that was larger than, or equal to, the one before (going over midnight excepted). As your experience has demonstrated, this will affect the 'randomness' of the numbers returned.

Setting the initial seed once for each execution of the Program (i.e. using Randomize once) ensures that the seed for each number is genuinely random throughout that execution.

If you need more than 16,777,215 Random Numbers, in one execution, then you'll have to use a different algorithm (there's loads lying around the Internet) or hardware.

(I suppose for 'random' you should read 'pseudo random')

[Code Doc]

Rather than randomize before each start, just call it once in total (in Form_Load etc). The results are "more random" that way.

That's what I did with the code that I offered. To my knowledge, my code works and produces unbiased random selections.

[niente0]

Hi, in order to get a REAL random seed (based on milliseconds), just use this little trick:

<script runat="server" language="javascript">
    function getSeed() {var tmp=new Date().getTime()+'';return tmp.substr(tmp.length-9)}
</script>

<% randomize getSeed() %>

This is because ASP Classic cannot read milliseconds, so if two users request a random number in the same second they would receive the same number (because of the same seed, based on time expressed in seconds). With Javascript run at server, the problem is elegantly solved.

[baka]

I think isnoend07 is done with this problem. not sure he cares 9 years later.
also this is VB6 and we dont need to call java for this particular problem.
we can use API calls or other means instead of VBA.Rnd