Slow "comparison/replace" script

CoolBlue · #1 06-16-2014, 07:15 PM

Well... I think its strange to put some code in, just in case there is a bug in the scripting engine.
Methinks you worry too much?
Well... Mebelieves is probably more apropriate.

I'm always happy to learn, but I am cautious of mythology...
I didn't see any authoritative references offered above in support of this practice.
I can find plenty refuting it and even more who are confused about it...
And there are plenty of structures where it will do nothing at all because there are references to the object elsewhere.

Referring to post #7 there are two reasons given for the practice. Regarding the first, see my opening statement. Regarding the second, it is patently untrue I'm afraid: Custom Class Objects and Objects that are instantiated with a New statement do not need to be explicitly deallocated with a Set to Nothing line. They are managed in the same way as any other object again, by counting referrences. And, depending on their archiatecture, it could give the misleading impression that they have been released when they have not.

So, to be honest, I don't accept either as a valid reason.

macropod · #2 06-16-2014, 07:37 PM

Quote:

Originally Posted by CoolBlue

I didn't see any authoritative references offered above in support of this practice.
I can find plenty refuting it and even more who are confused about it...

All I can say to that is you evidently haven't looked too hard. A simple web search turns up thousands of such references. I very much doubt MS would bother with all the examples showing its use on pages such as http://msdn.microsoft.com/en-us/libr...ffice.10).aspx if it merely clutters the code. See also:
http://www.vbi.org/Items/article.asp?id=106
http://www.decisionmodels.com/memlimitsd.htm

whatsup · #3 06-16-2014, 08:55 PM

Hi

CoolBlue, as to your question:
The loop is there, though it's rather a For ... Next:

Code:

 .
 .
 .
 For lngItem = 1 To UBound(arrCompare, 1)
    If Len(CStr(arrCompare(lngItem, 1))) > 0 Then
        objdic(arrCompare(lngItem, 1)) = ""
    End If
Next lngItem
.
.
.

You don't need the .Add method to fill the object. The problem with this method is, that the object doesn't allow enter a key that already exists. Therefore the following code will throw an error towards you on the second add:

Code:

 Sub AddCausingError()
Dim objdic As Object
  
Set objdic = CreateObject("scripting.dictionary")
  
objdic.Add 1, ""
objdic.Add 1, ""
  
Set objdic = Nothing
End Sub

If nonetheless you will use add, you always have to check first if the key already exists:

Code:

Sub AvoidErrorAdd()
Dim objdic As Object
  
Set objdic = CreateObject("scripting.dictionary")
  
objdic.Add 1, ""
If Not objdic.Exists(1) Then
    objdic.Add 1, ""
Else
    MsgBox "Key already exists"
End If
  
Set objdic = Nothing
End Sub

Especially if Item isn't of any interest, you can directly put the key into the dictionary, and you get a list of unique key-values without worrying about errors:

Code:

Sub JustOverwrite()
Dim objdic As Object
  
Set objdic = CreateObject("scripting.dictionary")
  
objdic(1) = "1stEntry"
objdic(1) = "2ndEntry"
  
Debug.Print objdic.Count
Debug.Print objdic(1)
  
Set objdic = Nothing
End Sub

As the immediate window will show, there is just one key and the item is the last which was added to the key.

For the other part, well, Paul has provided you by now with some evidence, and there is more out there. I'm pretty aware of other opinions pointing out it's not necessary and I won't interfere if they got the convidence and made up their mind. There are also people believing it's not necessary to declare variables, pointing out that vba comes by default without "Option Explicit". Well, some day they will discover an error and wonder were it comes from ...

CoolBlue · #4 06-17-2014, 06:36 AM

Quote:

Originally Posted by whatsup

Hi

CoolBlue, as to your question:
The loop is there, though it's rather a For ... Next:

Code:

 .
 .
 .
 For lngItem = 1 To UBound(arrCompare, 1)
    If Len(CStr(arrCompare(lngItem, 1))) > 0 Then
        objdic(arrCompare(lngItem, 1)) = ""
    End If
Next lngItem
.
.
.

You don't need the .Add method to fill the object. The problem with this method is, that the object doesn't allow enter a key that already exists. Therefore the following code will throw an error towards you on the second add:

Code:

 Sub AddCausingError()
Dim objdic As Object
  
Set objdic = CreateObject("scripting.dictionary")
  
objdic.Add 1, ""
objdic.Add 1, ""
  
Set objdic = Nothing
End Sub

If nonetheless you will use add, you always have to check first if the key already exists:

Code:

Sub AvoidErrorAdd()
Dim objdic As Object
  
Set objdic = CreateObject("scripting.dictionary")
  
objdic.Add 1, ""
If Not objdic.Exists(1) Then
    objdic.Add 1, ""
Else
    MsgBox "Key already exists"
End If
  
Set objdic = Nothing
End Sub

Especially if Item isn't of any interest, you can directly put the key into the dictionary, and you get a list of unique key-values without worrying about errors:

Code:

Sub JustOverwrite()
Dim objdic As Object
  
Set objdic = CreateObject("scripting.dictionary")
  
objdic(1) = "1stEntry"
objdic(1) = "2ndEntry"
  
Debug.Print objdic.Count
Debug.Print objdic(1)
  
Set objdic = Nothing
End Sub

As the immediate window will show, there is just one key and the item is the last which was added to the key.

For the other part, well, Paul has provided you by now with some evidence, and there is more out there. I'm pretty aware of other opinions pointing out it's not necessary and I won't interfere if they got the convidence and made up their mind. There are also people believing it's not necessary to declare variables, pointing out that vba comes by default without "Option Explicit". Well, some day they will discover an error and wonder were it comes from ...

Wow! I still didn't get it so I coded it and now I think your method is even cooler...

I have worked with Collections in the past and haven't delved into Dictionaries so, thanks for opening my eyes. I love it... you just jam in the Keys by referencing by it and set the member to "". And there they all are. Very nice!

Using your method on my system it blasts through 100K lines in 1.6 to 2 sec, depending on the data type. The data I used had about 30% "Others".

My little Value2 tweak gives a big advantage to the block reads, but its swamped by savings from your Dictionary jggery-pokery, it depends on the data type:
Value: Number or Text 1.6 to 1.7 sec Currency 1.8 to 2 sec; Date 2 sec
Value2: Number or Text 1.5 sec; Currency 1.5 sec; Date 1.5 sec

And Yep. On the matter of the Set to Nothing, obviously its a personal, value choice between equally respectable options. My aim was to just balance the thread so that people can make their own choice based on both arguments. I actually tried removing your error handler and re-adding the first member to the Dictionary to throw an error, just to see what happened and the object was released, according to VBE anyway...

Cheers

whatsup · #5 06-17-2014, 08:23 AM

Quote:

..just to see what happened and the object was released, according to VBE anyway...

CoolBlue, how did you do that, to check whether memory is freed or not? I tried to come up with an example, but so far I can't think of a method to access memory to look up if the key is removed or not.

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