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  #1 (permalink)  
Old September 17th, 2003, 11:50 AM
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Default performance question..

hi all..

i want to know if somebody did a performance test around this issue..

im looking for string that have a constant substring inside them..

i have to ways to do it:
strcomp
and
string like "*mystr"

do anybody know what's best practice for it??

thanks in advance...


Gonzalo Bianchi
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  #2 (permalink)  
Old September 17th, 2003, 12:32 PM
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Have you considered instr or instrrev? I think that is the most efficient.
  #3 (permalink)  
Old September 17th, 2003, 02:03 PM
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sorry.. strcomp was really instr.. do you have any test about them???

thanks..

Gonzalo Bianchi
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Old September 17th, 2003, 02:19 PM
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I haven't done any formal bechmarking, but if I remember correctly instr is more efficient than regular string comparison.
  #5 (permalink)  
Old September 17th, 2003, 08:23 PM
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Hi Gonzalo,

I did do some benchmarks some time ago and I found out
that, at least in my cases, the like operator was a 10%
slower than instr, but I did not spend that much time.
I though that because like is more powerful, there is
a penalty using it. But I can be wrong... Use GetTickCount
and iterate some thousand times both instr and like
using some of your data and check the difference.
GetTickCount is not that precise, do more than one run until
you get a stable number, and iterate enough time to get
a difference in time of at least one second.
I will be interested to know the results.

Marco

Quote:
quote:Originally posted by gbianchi
 hi all..

i want to know if somebody did a performance test around this issue..

im looking for string that have a constant substring inside them..

i have to ways to do it:
strcomp
and
string like "*mystr"

do anybody know what's best practice for it??

thanks in advance...


Gonzalo Bianchi
  #6 (permalink)  
Old October 8th, 2003, 10:53 AM
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Default

hi there..

i made some test between instr and like..
but i get no diference between then :(

well.. i try this..

Code:
Option Explicit
Dim fso As FileSystemObject
Dim fDir As Folder
Dim fArch As File
Dim sTime As Date
Dim nTotal As Long
Dim nHits As Long
Dim i As Long
Private Sub CmdCheck1_Click()
    nTotal = 0
    nHits = 0
    sTime = Now
    For i = 1 To 50
        For Each fArch In fDir.Files
            nTotal = nTotal + 1
            If InStr(1, LCase(fArch.Name), "dll", vbTextCompare) > 0 Then
                nHits = nHits + 1
            End If
        Next fArch
    Next i
    TxtTiempo.Text = DateDiff("s", sTime, Now)
    TxtTotal = CStr(nHits) & " / " & CStr(nTotal)
End Sub

Private Sub Command1_Click()
    nTotal = 0
    nHits = 0
    sTime = Now
    For i = 1 To 50
        For Each fArch In fDir.Files
            nTotal = nTotal + 1
            If LCase(fArch.Name) Like "*dll*" Then
                nHits = nHits + 1
            End If
        Next fArch
    Next i
    TxtTiempo1.Text = DateDiff("s", sTime, Now)
    TxtTotal1.Text = CStr(nHits) & " / " & CStr(nTotal)
End Sub

Private Sub Form_Load()
    Set fso = New FileSystemObject
    Set fDir = fso.GetFolder("C:\WINNT\system32")
End Sub
i use two buttons and 4 textboxes for displaying reasons...

and instr return 190 and like 191... no real dif...

could somebody else try it to see what results it have??


Gonzalo Bianchi
  #7 (permalink)  
Old October 8th, 2003, 11:21 AM
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The code I tried was thus:

Code:
Private Declare Function GetTickCount& Lib "kernel32" ()

Private Sub Form_Load()

Dim lngCount                        As Long
Dim lngNoFiles                      As Long
Dim lngNoDlls                       As Long
Dim strTemp                         As String
Dim lngTickCount                    As Long

    lngTickCount = GetTickCount
    lngNoDlls = 0
    lngNoFiles = 0
    For lngCount = 1 To 50
        strTemp = Dir("C:\WINDOWS\System32\*.*")
        Do Until strTemp = ""
            lngNoFiles = lngNoFiles + 1
            If InStr(1, LCase(strTemp), "dll", vbTextCompare) > 0 Then
                lngNoDlls = lngNoDlls + 1
            End If
            strTemp = Dir()
        Loop
    Next
    Debug.Print "Files: " & lngNoFiles & _
        " DLL's: " & lngNoDlls & _
        " Time: " & GetTickCount - lngTickCount & _
        "ms Average: " & (GetTickCount - lngTickCount) / lngNoFiles & "ms"

    lngTickCount = GetTickCount
    lngNoDlls = 0
    lngNoFiles = 0
    For lngCount = 1 To 50
        strTemp = Dir("C:\WINDOWS\System32\*.*")
        Do Until strTemp = ""
            lngNoFiles = lngNoFiles + 1
            If LCase(strTemp) Like "*dll*" Then
                lngNoDlls = lngNoDlls + 1
            End If
            strTemp = Dir()
        Loop
    Next
    Debug.Print "Files: " & lngNoFiles & _
        " DLL's: " & lngNoDlls & _
        " Time: " & GetTickCount - lngTickCount & _
        "ms Average: " & (GetTickCount - lngTickCount) / lngNoFiles & "ms"
    Unload Me
    End

End Sub
On my PC this gave me the following results:

Code:
Files: 119400 DLL's: 66050 Time: 1842ms Average: 0.015427135678392ms
Files: 119400 DLL's: 66050 Time: 1612ms Average: 0.013500837520938ms
Meaning that using Like is approximately 14% faster than InStr (or did I do that sum the wrong way round?)

Regards
Owain Williams


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