Q185990: HOWTO: Improve Performance of Object De-allocation

Article: Q185990
Product(s): Microsoft Visual Basic for Windows
Version(s): 
Operating System(s): 
Keyword(s): kbGrpDSVB
Last Modified: 11-JAN-2001

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The information in this article applies to:

- Microsoft Visual Basic Learning Edition for Windows, version 6.0 
- Microsoft Visual Basic Professional Edition for Windows, version 6.0 
- Microsoft Visual Basic Enterprise Edition for Windows, version 6.0 
- Microsoft Visual Basic Control Creation Edition for Windows, version 5.0 
- Microsoft Visual Basic Learning Edition for Windows, version 5.0 
- Microsoft Visual Basic Professional Edition for Windows, version 5.0 
- Microsoft Visual Basic Enterprise Edition for Windows, version 5.0 
- Microsoft Visual Basic Standard Edition for Windows, version 4.0 
- Microsoft Visual Basic Professional Edition for Windows, version 4.0 
- Microsoft Visual Basic Enterprise Edition for Windows, version 4.0 
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SUMMARY
=======

By default, object de-allocation in arrays and collections can be inefficient
when there is a large number of objects. This article describes a technique for
improving de-allocation performance.

MORE INFORMATION
================

When de-allocating a large number of objects in a collection or an array,
performance of the de-allocation process can be improved if objects are
de-allocated in the reverse order of their creation--this results in linear
performance. For arrays of objects this is simple; however, for collections it
can be difficult to determine the allocation order. In this case, the following
code provides you with good to reasonable performance:

     Public Sub DeallocCollection(colSource as Collection)
        Dim lIndex  as Long
        Dim lMax    as Long

        lMax = colSource.Count
        ReDim aryLocal(lMax) as object
        For lIndex = 1 to lMax
           if isObject(colSource.index(1)) then _
              Set aryLocal(lIndex) = colSource.index(1)
           colSource.Remove(1)
        Next
        set colSource = nothing

        For lIndex = lMax to 1 step -1
           set aryLocal(lIndex) = Nothing
        Next
     End Sub

The performance improvement depends upon the level of fragmentation in the
collection.

Additional query words: kbDSupport kbdss VBKBObj kbVBp400 kbVBp500 kbVBp600 kbVBp

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Keywords          : kbGrpDSVB 
Technology        : kbVBSearch kbAudDeveloper kbZNotKeyword6 kbZNotKeyword2 kbVB500Search kbVB600Search kbVBA500Search kbVBA500 kbVBA600 kbVB500 kbVB600 kbVB400Search kbVB400 kbZNotKeyword3
Issue type        : kbhowto

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