DOCUMENT:Q185990  21-MAY-1998  [vbwin]
TITLE   :Improving Performance of Object Deallocation
PRODUCT :Microsoft Visual Basic for Windows
PROD/VER:WINDOWS:4.0,5.0
OPER/SYS:WINDOWS
KEYWORDS:VBKBObj

======================================================================
---------------------------------------------------------------------
The information in this article applies to:

 - Microsoft Visual Basic Control Creation, Learning, Professional, and
   Enterprise Editions for Windows, version 5.0
 - Microsoft Visual Basic Standard, Professional, and Enterprise Editions
   for Windows, version 4.0
---------------------------------------------------------------------

SUMMARY
=======

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

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

When deallocating a large number of objects in a collection or an array,
performance of the deallocation process can be improved if objects are
deallocated 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 vb6rel VBKBObj
======================================================================
Keywords          : VBKBObj
Version           : WINDOWS:4.0,5.0
Platform          : WINDOWS
Issue type        : kbinfo

=============================================================================

THE INFORMATION PROVIDED IN THE MICROSOFT KNOWLEDGE BASE IS
PROVIDED "AS IS" WITHOUT WARRANTY OF ANY KIND.  MICROSOFT DISCLAIMS
ALL WARRANTIES, EITHER EXPRESS OR IMPLIED, INCLUDING THE WARRANTIES
OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.  IN NO
EVENT SHALL MICROSOFT CORPORATION OR ITS SUPPLIERS BE LIABLE FOR
ANY DAMAGES WHATSOEVER INCLUDING DIRECT, INDIRECT, INCIDENTAL,
CONSEQUENTIAL, LOSS OF BUSINESS PROFITS OR SPECIAL DAMAGES, EVEN IF
MICROSOFT CORPORATION OR ITS SUPPLIERS HAVE BEEN ADVISED OF THE
POSSIBILITY OF SUCH DAMAGES.  SOME STATES DO NOT ALLOW THE EXCLUSION
OR LIMITATION OF LIABILITY FOR CONSEQUENTIAL OR INCIDENTAL DAMAGES
SO THE FOREGOING LIMITATION MAY NOT APPLY.

Copyright Microsoft Corporation 1998.