TweetFollow Us on Twitter

AS Performance
Volume Number:12
Issue Number:5
Column Tag:Applescript

Improving AppleScript Performance

Avoiding the AppleSloth blues

By Mark Alldritt

Note: Source code files accompanying article are located on MacTech CD-ROM or source code disks.

Why Is AppleScript So Slow, Anyway?

This is the question our customers ask most frequently, and one to which there is no simple answer. The reason given by Apple is that the Apple event mechanism used by AppleScript to communicate with other applications has serious performance limitations under System 7. In my tests, there clearly are limits to the number of round-trip Apple events you can push through the system per second. However, there’s something else wrong, apparently, because even AppleScript scripts which don’t generate any Apple events do not seem to perform as well as similar scripts written in Frontier.

This article provides a number of tips for improving the performance of your scripts. Depending on the kind of scripts you are working on, these improvements in performance may turn out to be dramatic.

Improving Compile Time Performance

Regardless of what script editor you are using, you are bound to get to the point where you wish scripts would compile faster. Here are some tips for keeping compile times as short as possible:

Buy Speed Doubler if you are using a PowerPC-based Macintosh. My customers have reported a 2 to 4 times improvement in AppleScript performance with Speed Doubler installed.

Keep the number of scripting additions to a minimum. Having too many scripting additions slows AppleScript’s load time, since it must process that many more files in the Scripting Additions folder. Also, more scripting additions means more event and class names must be parsed from 'aete' resources and added to the AppleScript symbol table.

A side benefit of keeping the number of scripting additions to a minimum is that you are less likely to run into terminology conflicts. This happens when a term is defined by two different scripting additions.

Split up your scripting projects. Use the load script command to load pre-compiled portions of your script project. If you’re using Script Editor, Script Wizard, FaceSpan or Scripter, it’s probably best to store your pre-compiled scripts in a known location so that you can use simple Load Script statements:

property lib1 : load script alias "My HD:Script Libraries:Lib1"

Alternatively, you can store your libraries in the same folder as your script editor, and load them with the following command:

property lib1 : load script "Lib1"

If you’re using Script Debugger, you can use its path to me handling to store your libraries in a folder with your script:

property projectPath :¬
 «property ctnr» of item (path to me) of ¬
 application "Finder" as string
property lib1 : load script (projectPath & "Lib1")

Once you’ve loaded your library, you can access properties and call handlers stored within it like this:

propertyName of lib1

handlerName(p1, p2, p3) of lib1

Don’t overdo AppleScript formatting. The formatted text feature of AppleScript is the only really good way to understand how AppleScript has interpreted your script during compilation. Unfortunately, the more formats you use, the slower your compiles will be. The slowdown is caused when your script editor is forced to cope with growing numbers of style runs as it displays your script following a compile. The answer is to keep the number of formats you use to a minimum.

This point becomes more important as the size of your scripts grow. For short scripts, it’s not really an issue, but for scripts larger than about 100K it can represent as much as a couple of minutes of the total compile time. A PowerPC-native script editor helps here (Script Debugger, Script Wizard), but it’s always going to be an issue.

Keep background activity to a minimum. All the script editors allow some level of background activity during compiles. If you keep this to a minimum, your compiles will be faster. Avoid having the Finder perform folder size calculations, turn off personal file sharing, etc. If you’re using Scripter, turn off its “allow background compiles” preferences option. This speeds compiles dramatically.

Improving Run Time Performance

Probably the most frustrating part of using AppleScript is watching its seemingly slow progress through your script. Here are some tips and ideas for making scripts run faster.

Install Speed Doubler if you are on a PowerPC.
See above.

Keep the number of Apple events your script generates to a minimum. Under System 7, Apple event performance is poor. A System 7 application can process at most 60 events per second, with typical performance more like 20-40 events per second. Reducing the number of Apple events will significantly speed up your script.

The most common mistake is to iterate over application objects using AppleScript. Instead, use “whose” clauses to get the server application to do the iteration for you. (Note: not all scriptable applications support this - complain to the developers and let them know you want full support for the “object model”.)

The slow way:

tell application "Finder"
 repeat with aItem in (items of first window)
 if name of aItem ends with ".temp" then
 delete aItem
 end
 end
end

The fast way:

tell application "Finder"
 delete (items whose name ends with ".temp") ¬
 of first window
end

The next error people commonly make is to repeatedly ask for the value of properties. For example, you might do the following:

tell application "Finder"
 repeat with aItem in items of window 1
 if name of aItem ends with ".c" or ¬
 name of aItem ends with ".h" then
 -- do something with .c and .h files
 end
 end
end

This script fragment gets the value of the application’s name property twice. A faster method is to get the name property once:

tell application "Finder"
 repeat with aItem in items of window 1
 set theFileName to name of aItem
 if theFileName ends with ".c" or ¬
 theFileName ends with ".h" then
 -- do something with .c and .h files
 end
 end
end

Avoid using AppleScript’s object-oriented features. AppleScript supports object-oriented programming to a great extent. I’ve found that handler calls within object instances tend to be slow (the first handler call is the worst). Use these features only if they are justified.

Use properties to store pre-compiled values. If there are values which are calculated once at the beginning of your script, consider putting these calculations into property definitions. By doing this, you cause the calculations to be performed at compile time rather than run time.

This technique can be particularly dramatic if you are using scripting additions to help with the calculations, since the Apple events used to invoke the scripting additions are generated at compile time.

Use scripting additions. Use scripting additions for complex list and text manipulation. The ACME Script Widgets and other collections of scripting additions offer tools for text parsing, tokenization, list manipulation and other functions. It’s almost always going to be faster to use a scripting addition rather than an AppleScript loop to work with these data structures.

Execute scripting addition commands within your applet’s process. As stated above, Apple events sent to other processes for handling are slow (20-60 events/sec); but events processed within the script applet are handled much faster, since they are dispatched without involving interprocess communications and process context switches.

So, in the following example, the current date command (which is a scripting addition command) is executed within the Scriptable Text Editor’s process rather than the applet:

tell application "Scriptable Text Editor"
 make new line at end of first window ¬
 with data (current date as string)
end

An improvement in speed would result if you did it this way:

set theData to current date as string
tell application "Scriptable Text Editor"
 make new line at end of first window ¬
 with data theData
end

If you are deep within a tell block, you could deal with the problem this way:

tell application "Scriptable Text Editor"
 ...
 make new paragraph at end of first window with ¬
 data ((current date) of me as string)
 ...
end

Use the right tool for the job. Sometimes you can get dramatic speed improvements by switching tools. For example, if you’re doing text manipulation, consider using MacPerl, or BBEdit, or a special-purpose scripting addition. If you have several tools available, try using each of them to perform time-consuming parts of your script. See which one is best suited and performs best.

Use the right object accessing method. The Object Model is a powerful thing, and offers great flexibility for the script writer. The problem is that it allows you to easily create object specifications that can be very difficult for the server application to resolve.

You can sometimes improve performance greatly by changing the way you access objects. For example, text editors generally maintain internal data structures to help them identify the beginning of lines. As a result, line-based object specifications are resolved much faster than word- or paragraph-based specifiers, because the application can use the data it already has to speed things up.

Try using different ways of forming your object specifiers and see which ones are fastest.

Code time-consuming logic in OSAXen. As a last resort, you can code time-consuming portions of your script as a scripting addition. MacTech Magazine 10.1 featured an article on just this subject, and you can look at it online at http://web.xplain.com/mactech.com/Articles/Vol.10/10.01/
Extend-Applescript.bhtml. Documentation on writing scripting additions can also be found in Apple’s AppleScript Scripting Additions Guide.

The Final Frontier

The applets (standalone AppleScript applications) produced by Script Editor, Script Debugger, Script Wizard and Scripter all rely on the standard applet glue code provided by Apple. This glue code provides a framework in which your script executes. The standard glue code attempts to be a really good MacOS citizen. To this end, it yields the CPU to other processes very frequently. One way to improve the performance of your scripts is to write your own glue code, and yield the CPU less frequently, or possibly not at all. This change, depending on the frequency of yields, can cause speed improvements of up to 25%.

The Future

The future of AppleScript is quite bright. Following a period of almost non-existent support from Apple, there is to be a new version (1.2) released sometime this year. This new version will be PowerPC-native, and is expected to offer performance comparable to that of Frontier. Beyond the 1.2 release, there’s Copland. There is reason to expect that under Copland, the AppleEvent Manager will offer dramatic performance improvements; supposedly, Apple events will be dispatched directly to your handlers, not to your app’s event loop, thereby removing a serious speed bottleneck. And, there are rumours of a completely re-architected post-Copland AppleScript 2.0. In the meantime, AppleScript continues to prove its worth, and the techniques in this article should help you see some script speed improvements now.

 

Community Search:
MacTech Search:

Software Updates via MacUpdate

Dash 4.0.0 - Instant search and offline...
Dash is an API documentation browser and code snippet manager. Dash helps you store snippets of code, as well as instantly search and browse documentation for almost any API you might use (for a full... Read more
Bookends 12.7.9 - Reference management a...
Bookends is a full-featured bibliography/reference and information-management system for students and professionals. Bookends uses the cloud to sync reference libraries on all the Macs you use.... Read more
TrailRunner 3.8.834 - Route planning for...
TrailRunner is the perfect companion for runners, bikers, hikers, and all people wandering under the sky. Plan routes on a geographical map. Import GPS or workout recordings and journalize your... Read more
iFFmpeg 6.2.5 - Convert multimedia files...
iFFmpeg is a comprehensive media tool to convert movie, audio and media files between formats. The FFmpeg command line instructions can be very hard to master/understand, so iFFmpeg does all the hard... Read more
DaisyDisk 4.4 - $9.99
DaisyDisk allows you to visualize your disk usage and free up disk space by quickly finding and deleting big unused files. The program scans your disk and displays its content as a sector diagram... Read more
iFFmpeg 6.2.5 - Convert multimedia files...
iFFmpeg is a comprehensive media tool to convert movie, audio and media files between formats. The FFmpeg command line instructions can be very hard to master/understand, so iFFmpeg does all the hard... Read more
DaisyDisk 4.4 - $9.99
DaisyDisk allows you to visualize your disk usage and free up disk space by quickly finding and deleting big unused files. The program scans your disk and displays its content as a sector diagram... Read more
BetterTouchTool 2.07 - Customize Multi-T...
BetterTouchTool adds many new, fully customizable gestures to the Magic Mouse, Multi-Touch MacBook trackpad, and Magic Trackpad. These gestures are customizable: Magic Mouse: Pinch in / out (zoom... Read more
BetterTouchTool 2.071 - Customize Multi-...
BetterTouchTool adds many new, fully customizable gestures to the Magic Mouse, Multi-Touch MacBook trackpad, and Magic Trackpad. These gestures are customizable: Magic Mouse: Pinch in / out (zoom... Read more
BetterTouchTool 2.07 - Customize Multi-T...
BetterTouchTool adds many new, fully customizable gestures to the Magic Mouse, Multi-Touch MacBook trackpad, and Magic Trackpad. These gestures are customizable: Magic Mouse: Pinch in / out (zoom... Read more

Latest Forum Discussions

See All

Pokémon GO Generation 2 evolution guide
At long last, Niantic Labs finally unleashed the Generation 2 Pokémon into the wild. Pokémon GO trainers are scrambling to grab up this new set of 80 Pokémon. There are some special new tricks required to catch all of these new beasties, though.... | Read more »
The best new games we played this week
It feels as though the New Year got off to a creaking start as far as mobile games go, but that's changed over the past few weeks. The last few days alone have seen the debut of a number of wonderful games, so we thought we'd take the time to... | Read more »
Recruit more scallywags and discover new...
Get ready to show off your sea legs all over again in Oceans & Empires’ new grand update, which aims to make the act of rising to the role of seven seas ruler even more fresh and appealing, thanks to a richness of new content on both iOS and... | Read more »
Mage the Ascension: Refuge (Games)
Mage the Ascension: Refuge 1.0 Device: iOS Universal Category: Games Price: $4.99, Version: 1.0 (iTunes) Description: The groundbreaking roleplaying game Mage: The Ascension manifests in our turbulent present with Refuge, an... | Read more »
Vampire: Prelude (Games)
Vampire: Prelude 1.0 Device: iOS Universal Category: Games Price: $4.99, Version: 1.0 (iTunes) Description: The classic roleplaying game Vampire: The Masquerade returns to digital games with a Prelude of things to come. Experience a... | Read more »
Digby Forever Guide: How to dig to the d...
Digby Forever is a sparkling homage to arcade classics, and while you may be tiring of the number of arcade games being thrown at you, this endless digger finds many ways to stand out from the rest of the pack. The game manages to be challenging... | Read more »
The best sales on the App Store this wee...
It's been quite the week in mobile games, but if the latest releases(there were some pretty darn good ones, in case you missed out) aren't really doing the trick, perhaps some of these discounted games will. Many of these premium games had their... | Read more »
Why the new Fire Emblem Heroes update sh...
It’s exciting to see Nintendo delving into the mobile sphere, regardless of whether it’s to give fans another platform to enjoy their fans or simply a sound business venture. Two of the company's announced mobile games have finally come to... | Read more »
New Fire Emblem Heroes update adds new h...
Fire Emblem Heroes received a sizeable update first thing this morning. The update features a batch of fresh content along with a few updates to the game's systems. [Read more] | Read more »
The Deep Paths (Games)
The Deep Paths 1.0 Device: iOS iPhone Category: Games Price: $3.99, Version: 1.0 (iTunes) Description: 25% off launch sale!!! The Deep Paths: Labyrinth Of Andokost is a first-person, dungeon crawling RPG, with traditional grid-based... | Read more »

Price Scanner via MacPrices.net

13-inch 2.0GHz Space Gray MacBook Pro on sale...
Adorama has the non-Touch Bar 13″ 2.0GHz Space Gray MacBook Pro in stock today for $100 off MSRP. Shipping is free, and Adorama charges NY & NJ sales tax only: - 13″ 2.0GHz MacBook Pro Space Gray... Read more
13-inch Touch Bar MacBook Pros on sale for $1...
B&H Photo has select 2016 Apple 13″ Touch Bar MacBook Pros in stock today and up to $100 off MSRP. Shipping is free, and B&H charges NY sales tax only: - 13″ 2.9GHz/512GB Touch Bar MacBook... Read more
KSI-1802R SX Disinfect-able Keyboard With Wav...
KSI has unveiled a new, innovative medical keyboard, the KSI-1802R SX, at HIMSS 2017, running February 19-22 in Orlando, Florida. KSI-1802R SX is the only keyboard that combines dual factor... Read more
15-inch Touch Bar MacBook Pros on sale for up...
Amazon has 15″ Touch Bar MacBook Pros in stock today and on sale for up to $150 off MSRP including free shipping: - 15″ 2.7GHz Touch Bar MacBook Pro Space Gray: $2720.38 $79 off MSRP - 15″ 2.7GHz... Read more
Apple’s Education discount saves up to $300 o...
Purchase a new Mac or iPad using Apple’s Education Store and take up to $300 off MSRP. All teachers, students, and staff of any educational institution qualify for the discount. Shipping is free: -... Read more
13-inch 1.6GHz/256GB MacBook Air on sale for...
Newegg has the 13″ 1.6GHz/256GB MacBook Air (MMGG2LL/A) on sale for $1029.99 including free shipping. Their price is $170 off MSRP, and it’s the lowest price available for this model. Choose Newegg... Read more
Save up to $600 with Apple refurbished Mac Pr...
Apple has Certified Refurbished Mac Pros available for up to $600 off the cost of new models. An Apple one-year warranty is included with each Mac Pro, and shipping is free. The following... Read more
12-inch 1.1GHz Retina MacBooks on sale for $1...
B&H has 12″ 1.1GHz Retina MacBooks on sale for $150 off MSRP. Shipping is free, and B&H charges NY sales tax only: - 12″ 1.1GHz Space Gray Retina MacBook: $1149 $150 off MSRP - 12″ 1.1GHz... Read more
InTouch Health Expands iOS And Windows Produc...
Specialty telehealth enterprise provider InTouch Health has announced an expanded range of FDA Class I listed medical devices and software solutions for ambulatory, non-acute and non-emergent... Read more
iMobie Airs World’s 1st iCloud Manager with M...
iMobie Inc., an Apple-related software company, announced their newly-updated iPhone manager AnyTrans with exclusive feature to sync and manage contents across multiple iCloud accounts. With it,... Read more

Jobs Board

*Apple* Retail - Multiple Positions - Apple,...
Job Description: Sales Specialist - Retail Customer Service and Sales Transform Apple Store visitors into loyal Apple customers. When customers enter the store, Read more
Manager *Apple* Systems Administration - Pu...
Req ID 3315BR Position Title Manager, Apple Systems Administration Job Description The Manager of Apple Systems Administration oversees the administration and Read more
*Apple* Technician - nfrastructure (United S...
Let’s Work Together Apple Technician This position is based in Portland, ME Life at nfrastructure At nfrastructure, we understand that our success results from our Read more
*Apple* Retail - Multiple Positions - Apple,...
Job Description: Sales Specialist - Retail Customer Service and Sales Transform Apple Store visitors into loyal Apple customers. When customers enter the store, Read more
Manager *Apple* Systems Administration - Pu...
Req ID 3315BR Position Title Manager, Apple Systems Administration Job Description The Manager of Apple Systems Administration oversees the administration and Read more
All contents are Copyright 1984-2011 by Xplain Corporation. All rights reserved. Theme designed by Icreon.