RE: processing time & stack overflow!!!
RE: processing time & stack overflow!!!
- Subject: RE: processing time & stack overflow!!!
- From: monk <email@hidden>
- Date: Sun, 02 Sep 2001 03:28:35 -0400
-- 8/31/01 8:03 AM: email@hidden said:
>
On Fri, 31 Aug 2001 04:24:15 -0400, monk wrote,
>
>
> can you explain/share to/with us what you did to
>
> make the script go from an average of 12 minutes to (on my machine) 12
>
> seconds
>
>
I basically did what Arthur was telling us to do:
>
>
1. use his handler ;)
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2. use a reference to the reallyBigList
well then, i guess arthur us some kind of scripthead deity in my book!
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>
1. A script usually consists of two types of commands: those handled
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internally by AppleScript (basic math, strings, lists...) and those that are
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handled externally by an application or scripting addition. With the latter,
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AppleScript has to send a message to the receiving application or osax to
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process the command, and then get a message back containing the results.
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>
In the case of "random number", that command belongs to the Standard Additions
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osax (osax is another term for scripting addition). Because of this, when a
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script invokes the command, it incurs an overhead of two messages; one to say
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"hey, Standard Additions, give me a random number" and the other to say
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"thanks, that random number is just what I needed." Normally, this overhead is
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barely noticed because it takes a small fraction of a second to perform, but
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when repeated thousands of times...
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So, using Arthur's handler reduced that overhead from thousands of repetitions
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to just one (he's a smart guy).
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2. When manipulating very large lists in AppleScript, there's a method that
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can be used to reduce processing overhead: a reference to someReallyBigList.
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>
Now, this is something that I use but don't really fully understand, so I'm
>
the wrong guy to answer. But it seems that when manipulating lists, the
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"reference to" construct will save considerable amounts of processing.
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>
I would guess that it has something to do with reassigning memory. That when
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directly manipulating a list, e.g. setting the contents of item 1 to the
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contents of item 2, AppleScript has to: assign memory to hold a copy of the
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contents of item 2, assign the new memory address to item 1, and then release
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the old address.
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Whereas with "reference to", it just tells item 1 "you see where item 2 's
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contents are in memory? Ok, that's what your contents are supposed to be as
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well."
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>
But I'm just guessing. Fortunately, you can use "reference to" without needing
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to understand how it's _implemented_. All you need to do is understand how it
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_behaves_ (we'll leave the ugly stuff of impementation to the AppleScript
>
team).
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>
In any case, all thanks for the improved performance of the "cross cutting"
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script should go to Arthur (hey, he really is a smart guy! ;)
>
i agree and thanks for that succinct description!
>
Victor
>
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h 'monk' elmer
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