Xtreme Visual Basic Talk - View Single Post - Showing letters as well in random created "number"

Hello,

Quote:

Originally Posted by Diurnal

Also, do you think it would help performance to use a long array instead of a variant to hold the look up data?

This was a timely kick in the right direction.

Why am I mucking around with a Variant Array, here?

I'm not sure I like the prospect of stacking an array of longs, but, seeing as I am talking about working with a Byte Array, why not go Byte Array to Byte Array? Just not seeing the forest through the trees...

First, a few tests to make sure my logic is binding tightly:

Code:

Sub tstBArrStack()
Dim b() As Byte
Let b = "Test"
Debug.Print ChrW$(b(1 * 2 - 2)); ChrW$(b(2 * 2 - 2)); _
    ChrW$(b(3 * 2 - 2)); ChrW$(b(4 * 2 - 2))
End Sub

Sub tstBArrStack2()
Dim b(0 To 7) As Byte, s As String
b(0) = 84:      b(2) = 101
b(4) = 115:     b(6) = 116
Let s = b
Debug.Print s
End Sub

And the revised function:

Code:

Public Function rndStr(ByRef StrLength As Long) As String
Dim b() As Byte, keyArr() As Byte
Dim i As Long
Let keyArr = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz"
ReDim b(1 To StrLength * 2)
For i = 1 To StrLength * 2 Step 2
    Let b(i) = keyArr((Int((62 - 1 + 1) * Rnd + 1)) * 2 - 2)
Next
Let rndStr = b
End Function

This is much faster. If I run this:

Code:

Option Explicit

Public Declare Function QueryPerformanceFrequency _
    Lib "kernel32.dll" ( _
    lpFrequency As Currency) As Long

Public Declare Function QueryPerformanceCounter _
    Lib "kernel32.dll" ( _
    lpPerformanceCount As Currency) As Long

Private Sub TimerTime()
Dim Ctr1 As Currency, Ctr2 As Currency, Freq As Currency
Dim Overhead As Currency, a As String, i As Long
QueryPerformanceFrequency Freq
QueryPerformanceCounter Ctr1
QueryPerformanceCounter Ctr2
Overhead = Ctr2 - Ctr1 ' determine API overhead
QueryPerformanceCounter Ctr1 ' time loop

For i = 1 To 1000
    Let a = rndStr(16)
    'Let a = rndStr2(16)
Next i

QueryPerformanceCounter Ctr2
Debug.Print (Ctr2 - Ctr1 - Overhead) / Freq
End Sub

On an average of 30 times, it clocks in at 0.0088 Seconds, as opposed to 0.010 seconds for the mid & concatenate approach, and the performance gain should grow with Str size. This does speak to the OPs question.

Looking at your revised Mid$() approach, I would think it would be faster, but I haven't tested it yet...