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If you do a lot of floating-point division operations in VB, you may want to optimize these operations by multiplying by the reciprocal value. For example, instead of performing this calculation:
X/Y
do this:
X * (1/Y)
You can see how this works in VB by adding the following code to a form in a new project:
Private Declare Function GetTickCount Lib "kernel32" () As Long
Const NORMAL As Double = 1453
Const RECIPROCAL As Double = 1 / NORMAL
Const TOTAL_COUNT As Long = 10000000
Private Sub NormalDivide()
On Error GoTo Error_Normal
Dim dblRes As Double
Dim lngC As Long
Dim lngStart As Long
lngStart = GetTickCount
For lngC = 1 To TOTAL_COUNT
dblRes = Rnd / NORMAL
Next lngC
MsgBox "Total Time: " & GetTickCount - lngStart
Exit Sub
Error_Normal:
MsgBox Err.Number & " - " & Err.Description
End Sub
You’ll also need a DBR function that is identical to NormalDivide, except that the one line of code in the For ... Next loop is:
dblRes = Rnd * RECIPROCAL
I have seen consistent performance gains of 15% with the DBR function. However, before you start changing all the code where you do division, there’s a bit of a catch. There are some rounding issues to be concerned about (for example, 3/3 = 1, but 3 * (0.333333) = 0.999999). See http://www.cs.wisc.edu/~cs354-2/lec.notes/arith.flpt.html and http://science.nas.nasa.gov/Pubs/TechReports/RNRreports/dbailey/pi/pi.html for more detailed information.
Published: 04.19.1999 12:00:00 AM CST