Benchmark: Scripting Dictionary vs XData

For the community knowledgebank...

I was looking to streamline a routine that is called intensively in my program so as to cut down the overall processing time. The method I devised would entail keeping some information about each polyline in the drawing and accessing it later in the program (multiple times).

The obvious avenue was XData but I wondered if a Scripting Dictionary might be faster. As I was trying to squeeze as much performance as possible out of the routine I decided to write both methods and compare them. I used the CCRP High Performance Timer Objects as they are specifically optimized for benchmarking and don't require a form to live on.

Before I share the results, let me point out one "gotcha". As part of the benchmarking I kept a count of how many times the read and write routines were invoked. I noticed that the Dictionary routines were invoked more times than the XData routines. This didn't make sense to me as they were supposed to be performing the same function (and the end results did appear to be the same) so I endeavoured to isolate the difference. I spent *hours* on this before finally working it out - one part of my main code involved using the Copy method to copy one polyline to another. With the XData method the information was transferred to the copy, but of course with the Dictionary method it was not. Subsequent logic that tested for the presence of the information caused the two paths to diverge. You should decide on a case-by-case basis whether you want copied entities to inherit the "information" from the original.
[pre]
Invocations XData Dictionary
Write 182 41ms 15ms
Read 680 6304ms 769ms
[/pre]
As well as being faster, the Dictionary approach was significantly easier to code. For XData the code had to determine the data type of the data to be stored and set up the XDataType structure accordingly. This was more complex when storing array information. For the Dictionary I simply used the Entity Handle concatenated with the "Property Name" (something made up by the programmer) as the dictionary key and stored the required value against it.

Hope this is useful.

Regards

Wayne Ivory
IT Analyst Programmer
Wespine Industries Pty Ltd

 

Hi Wayne,

I am trying to store a string with some objects. My concern is that when ever the object is copied and created a new instance from the old one, the string stored with the previous instance should not be copied in new object. For this I tried to store the string in XData, but when ever I am copying the entity which has XData, the value of XDAta too is get copied. By seeing your post I think that my task can be achieved by implementing with the dictionary. So can you provide me a small pice of code how to store the string in the dictionary of an object.

Thanks in advance

manoj

 

Uuuu, dumb question but, what is a "scripting dictionary" as opposed to
regular dictionary routines I use?

 

True but speed isn't the only issue. XData can be stored directly on an
entity while external information must be manually synched. XData can
include information which updates automatically as the entity changes.
Again, information must be manually cynched with dictionaries.

I'm not casting aspersions upon your work or observations. I just wanted
to make a counterpoint to ensure that people take the time to evaluate
which tool would be best for their particular programming needs.

 

Microsoft Scripting Dictionary available when you add a reference to the
Microsoft Scripting Runtime. This has nothing to do with AutoCAD - it is a
programming object kinda like a Collection on steriods

-- Mike
___________________________
Mike Tuersley
CADalyst's CAD Clinic
Rand IMAGINiT Technologies
___________________________
the trick is to realize that there is no spoon...

 

Aahh, interesting. Are there any examples on this?

 

From: Tony Tanzillo (tony.tanzillo_at_caddzone_dot_com)
Subject: Re: Function to return collection


View this article only
Newsgroups: autodesk.autocad.customization.vba
Date: 2003-04-03 16:08:44 PST


Use a dictionary, and populate it with keys that
are names of the collections and values that are
the collections themselves.

Then, you can just reference the given collection
by a string key (which is its name).

' ---------------------------------------------------
' Requires reference to scripting runtime:

Dim collDict As Scripting.Dictionary


Public Sub InitCollDict()
Set collDict = New Scripting.Dictionary
collDict.Add "LAYERS", ThisDrawing.Layers
collDict.Add "BLOCKS", ThisDrawing.Blocks
collDict.Add "LINETYPES", ThisDrawing.Linetypes

' and so on ....

End Sub

Public Sub Test()
InitCollDict
Debug.Print "Blocks.Count = " & collDict("BLOCKS").Count
End Sub

 

Sure. Here is what I ended up with.

Code:

' Add a reference to the Microsoft Scripting Runtime
Dim CustomProperties As New Dictionary
Const SEPARATOR As String * 1 = "~"
'
Private Sub PropertyLet(Entity As AcadEntity, PropertyName As String, PropertyValue As Variant)
If CustomProperties.Exists(Entity.Handle & SEPARATOR & PropertyName) Then
CustomProperties(Entity.Handle & SEPARATOR & PropertyName) = PropertyValue
Else
CustomProperties.Add Entity.Handle & SEPARATOR & PropertyName, PropertyValue
End If
End Sub
'
Private Function PropertyGet(Entity As AcadEntity, PropertyName As String) As Variant
If CustomProperties.Exists(Entity.Handle & SEPARATOR & PropertyName) Then PropertyGet = CustomProperties(Entity.Handle & SEPARATOR & PropertyName)
End Function
'
Private Sub Example()
PropertyLet GeneralLine, "Material", "Elastic"
PropertyLet GeneralLine, "AssociatedPoint", OtherLine.StartPoint
MsgBox "This line is made of " & PropertyGet(GeneralLine, "Material")
End Sub

Regards

Wayne

 

Right you are. In my case speed *was* the issue, plus the information was static (ie not required to scale) and of a transient nature so it was not required once the macro finished.

As you say, other people with different requirements may be better suited to XData. Thanks for clarifying where I'm coming from.

Regards

Wayne

 

But I think my requirement was different than the yours one and it cannot be served vy scripting dictionary. I wanted to store some string with acad entity e.g. line. When ever a user copies the line manually using the copy command of autocad, every thing except the string stored with the line should be copied. The string stored should persist in different session of AutoCAD.

 

I use XData which I don't want to be copied with the object so what I have done is undefined the copy command and created my own in VBA that removes the paticular XData. This does not take into consideration other commands like CopyClip. Also because my new copy command is in VBA I have lost the dragging effect & ortho control which I hope to rectify with Tony Tanzillo's AcadX DynamicGraphics class.

Regards - Nathan