[jawsscripts] Re: Resizing arrays
- From: "Octavian Rasnita" <orasnita@xxxxxxxxx>
- To: <jawsscripts@xxxxxxxxxxxxx>
- Date: Fri, 6 Jan 2012 14:10:21 +0200
This philosophy was applied in other programming languages even before Python
appeared, so better said... what Donald Knuth said... "Premature optimization
is the root of all evil". :-)
--Octavian
----- Original Message -----
From: "Jamal Mazrui" <empower@xxxxxxxxx>
To: <jawsscripts@xxxxxxxxxxxxx>
Cc: "Andrew Hart" <ahart@xxxxxxxxxxxxx>
Sent: Friday, January 06, 2012 1:47 PM
Subject: [jawsscripts] Re: Resizing arrays
>I agree that many consecutive COM calls, e.g., in a loop, can have a
> noticeable effect on performance. In my opinion, however, such
> performance degradation is usually not noticeable in screen reader
> scripting scenarios. I am not saying that there are not occasions where
> this is a concern, but for the most part, the delays of user interface
> events and speech make COM delays negligible by comparison.
>
> In addition, the benefits of powerful COM techniques should also be
> weighed. The .NET ArrayList, for example, provides all the flexibility
> and dynamism that the original message on this topic was seeking.
> Elements of any data type may be added or removed from an ArrayList with
> ease via dedicated, well-tested methods. The list may be easily sorted,
> reversed, or searched by other methods.
>
> One could take the time to write a lot of custom JAWS functions that try
> to achieve this functionality, and it would be time consuming,
> error-prone, and still short of the same functionality. One of the
> strengths of Windows compared to other platforms is the many, built-in
> object models that COM clients in any language can exploit. I agree
> with the philosophy from the Python programming world: code to solve a
> problem first, and then only optimize later if demonstrably needed for
> performance.
>
> Jamal
>
> On 1/5/2012 2:59 PM, Andrew Hart wrote:
>> COM object calls are generally more expensive than calls to routines
>> internal to an application. There's all the overhead involved in
>> marshalling cross-process references and the like to deal with.
>> consequently, if you have to make lots and lots of COM calls, the COM
>> overhead will become apparent. I expect this is what you were
>> observing. the same is true of out-of-proc servers. Inproc servers
>> should suffer less, since they are loaded directly into the address
>> space of the calling process and hence calls are straight forward, but
>> unfortunately, JAWS Script doesn't know how to talk to dll's directly,
>> only COM automation objects.
>>
>> Cheers,
>> Andrew.
>>
>> On 5/01/2012 6:12 PM, Doug Lee wrote:
>>> I got quite a shock a couple months or so ago on the subject of using
>>> COM objects versus collections, and I assume my results would apply
>>> reasonably equally to JAWS arrays when compared to COM objects.
>>>
>>> Unfortunately I remember niether specific results nor the location of
>>> any written copy of them, but I do remember finding that tests
>>> involving over 500 references to a collection versus a COM object,
>>> Scripting.Dictionary in my case, produced such wildly different
>>> performance results to indicate clearly in favor of collections over
>>> COM objects. People have been saying this for years, but honestly, I
>>> didn't think it was a big enough deal until I did those tests. It
>>> would be handy for me if someone out there could prove me wrong,
>>> because I have a lot of code that uses Scripting.Dictionary, predating
>>> collections of course. But I currently operate with the assumption
>>> that Scripting.Dictionary objects are costly enough to avoid for loops
>>> that run, say, more than 50 times.
>>>
>>> On Thu, Jan 05, 2012 at 04:05:27PM -0500, Jamal Mazrui wrote:
>>> Another approach is to use the ArrayList class of the .NET Framework,
>>> which a JAWS script can access via COM. Almost any Windows computer these
>>> days has at least .NET 2.0, which includes this class. The progID to pass
>>> to the CreateObject function is "System.Collections.ArrayList." The
>>> methods and properties of the object thus instantiated are documented at
>>>
>>> http://msdn.microsoft.com/en-us/library/system.collections.arraylist.aspx
>>>
>>> This approach has the advantage of working with any JAWS version.
>>>
>>> Similarly, for dictionary as opposed to list collections, it may be worth
>>> considering use of the Scripting.Dictionary class of the Windows Script
>>> Host, available on any Windows computer. The progID is
>>> "Scripting.Dictionary." Such an object is documented at
>>>
>>> http://msdn.microsoft.com/en-us/library/x4k5wbx4(VS.85).aspx
>>>
>>> A couple more useful web pages on this topic are as follows:
>>>
>>> http://www.robvanderwoude.com/vbstech_data_arraylist.php
>>>
>>> http://halfloaded.com/blog/net-classes-within-vbscript-doing-randomness-and-arrays-the-easy-way/
>>>
>>> Jamal
>>>
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