list-building performance

Subject: list-building performance

From: Nigel Redmon <email@hidden>

Date: Fri, 1 Jun 2007 17:57:46 -0700

Delivered-to: email@hidden

I expected that appending items to a list by setting (or copying to) the end of a list would be fairly efficient, but found it's not. It appears that the process grows with the size of a list, so that the time involved grows exponentially, at least with the ways I've tried so far. For instance, creating a list as follows take about 1 second for 500 loop iterations, 4 seconds for 1000, and 32 seconds for 2000:

set startTime to (time of (current date))

set theList1 to {}

set timeStamp to 0

repeat with idx from 1 to 2000

set end of theList1 to {timeStamp, noteOn, 60, 100}

set end of theList1 to {timeStamp + 1, noteOn, 60, 0}

set timeStamp to timeStamp + 1

end repeat

(time of (current date)) - startTime

If I split the job up, working in smaller chunks and concatenating them, performance goes up dramatically. For instance, I can do the same job in a second if I nest two loops, with the inner one building a smaller section and the outer loop concatenating the result into another list. Obviously, that's worth is, since the code only grows by a couple of lines and executes 32 times faster, but it seems like there should be a better way. Surely there must be an efficient way to append something to the end of a long list--am I missing something?

Thanks

_______________________________________________ Do not post admin requests to the list. They will be ignored. AppleScript-Users mailing list (email@hidden) Help/Unsubscribe/Update your Subscription: http://lists.apple.com/mailman/options/applescript-users/email@hidden Archives: http://lists.apple.com/archives/applescript-users This email sent to email@hidden

Follow-Ups:

Re: list-building performance
- From: "Mark J. Reed" <email@hidden>
Re: list-building performance
- From: KOENIG Yvan <email@hidden>