Performance impact of calling lots of functions in vbscript - vbscript

Question

I have lots of sub routines and functions like these:
Sub LogInfo(Txt)
'Write an entry to the log file
If LogEnableInfo Then Log "Info: " & Txt
End Sub
Or this:
Function GetSettingValue(Key)
'Get the value of a setting or an empty string if the setting is not set
Dim Res
If Settings.Exists(UCase(Key)) Then Res = Settings(UCase(Key)) Else Res = ""
GetSettingValue = Res
End Function
Or this:
Sub DoExp(Exp, ErrTag)
'Execute an HS.Exp with Error handling and Debugging
Err.Clear
On Error Resume Next
HS.Exp Exp
If Err.Number <> 0 Then
LogError "HS.Exp """ & Exp & """ , Tag: " & ErrTag
Err.Clear
ElseIf LogEnablePut Then
Log "Put: HS.Exp """ & Exp & """ , Tag: " & ErrTag
End If
On Error GoTo 0
End Sub
They're really one liners that don't do much, but I use lots of times, so I don't want to type it out every time. I also use recursive functions a lot.
Since speed and memory use is critical to my application, what I would like to know is if the act of calling a function or sub in vbscript has a considerable performance impact? I know that in PHP, this has been cited as a performance issue. Can I just go ahead and create zillions of little nested functions to do everything or should I use them a little more sparingly?

Answer 1

In my experience using functions repeatedly is a bad thing in VBS, in a small test script I wrote I found that using functions were about 5 times slower.
startTime = Timer
x = 0
For i = 0 To 1000000000
x = x + 1
Next
endTime = Timer
WScript.Echo x
WScript.Echo CStr(endTime - startTime)
startTime = Timer
y = 0
For i = 0 To 1000000000
y = fooBooGoo(y)
Next
endTime = Timer
WScript.Echo y
WScript.Echo CStr(endTime - startTime)
Function fooBooGoo(p)
g = p + 1
fooBooGoo = g
End Function
The output I got was:
1000000001
306.6289
1000000001
1554.875

Answer 2

The rule "violate good practice (don't repeat yourself, clean program structure, ...) for speed gains!" is bad.
I doubt that there is even one real life VBScript program that becomes fast enough as soon as you inline functions/subs/methods - if you show me two, I'm willing to discuss using/writing a preprocessor for VBScript that expands macros and adds line numbering to scripts.
If speed is important, you should benchmark early/continously and optimize for speed by choosing better algorithms or better tools (COM, Net, Shell).
If (3) does not help, switch to a better language.
Samples to illustrate what I mean by "better tools" (#3):
using one ADO connection (created once (with late binding in VBScript)) to execute many SQL statements on a folder of .CSVs instead of using a FSO, .Readline loops, Splits, and complex IFs
using one .Net component (ArrayList, StringBuilder, ...) for many operations instead of using ReDim Preserve on native arrays or string concatenation in a loop
shelling out to dir /s /b c:\where\ever\*.vbs instead of a (faulty/inefficient) homegrown/stolen recursive directory walker that looks at all files to filter the .vbs

Answer 3

Functions are used to carry on a specific task or to perform specific operation. Same as in other languages, but in OOP they are usually called "methods", at least when they are attached to a class. It means to be able to work. Function is the process where a machine can work and make things efficient. here's an ex. that is used in a sentence. the machine won't work right. Or what you could say is the function is the ability to work so the mathematical definition would be the ability to solve an equation/problem. Function means working.
So, with regard to using function re-cursive's would be better but overall in object based languages like vbscript, objects should be created and set=nothing later for actually making system consume memory efficiently.
Thanks