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

Latest Forum Discussions

See All

Soft Drummer (Music)
Soft Drummer 1.0 Device: iOS Universal Category: Music Price: $14.99, Version: 1.0 (iTunes) Description: Soft Drummer is the closest thing to a pro session subtle drummer in your pocket. Easy to use and fast, it's much more than a... | Read more »
Is GO Gear the Pokemon GO map app you...
Now that we've settled into something of a Pokemon GO status quo, the number one desire of most players can best be summed out by modifying a quote from Rod Tidwell of Jerry Maguire: "Show me the Pokemon!" [Read more] | Read more »
Rodeo Stampede update: Mountains, new an...
The Savannah and Jungle were just the beginning in Rodeo Stampede. Get ready to head for the Mountains. I think I heard that in a beer ad once. [Read more] | Read more »
COSMOS RINGS (Games)
COSMOS RINGS 1.0.0 Device: iOS iPhone Category: Games Price: $5.99, Version: 1.0.0 (iTunes) Description: This game cannot be played without the Apple Watch.Released anniversary sale until August 31,2016 PST! A tragic tale of time's... | Read more »
How to get started selling on Mercari
As far as ecommerce has come over the last decade or so, there's still a tremendous opportunity to make it easier for people to buy and sell goods. That's especially true when it comes to shopping apps, which should only continue to increase in... | Read more »
Human Anatomy Atlas 2017 Edition - Compl...
Human Anatomy Atlas 2017 Edition - Complete 3D Human Body 1.0.24 Device: iOS iPhone Category: Medical Price: $24.99, Version: 1.0.24 (iTunes) Description: | Read more »
Heroes of Normandie (Games)
Heroes of Normandie 1.5 Device: iOS Universal Category: Games Price: $14.99, Version: 1.5 (iTunes) Description: The game does not support iPhone 4s and below | Read more »
Why you should never power up Pokemon in...
There's no question that candy is dandy in Pokemon GO. You need big quantities of it to evolve your Pokemon, and when combined with stardust, it can be used to power up your favorite pocket monsters as well, making them more formidable for the gym... | Read more »
Webzen launches 3D MMORPG MU Origin on i...
Mu Origin is featured time and time again at the very top of App Stores in China, and within the top five worldwide top-grossing charts on Google Play.Its popularity in Korea and China, featuring more than 120 registered players in China and 6... | Read more »
Severed (Games)
Severed 1.0 Device: iOS Universal Category: Games Price: $5.99, Version: 1.0 (iTunes) Description: LAUNCH DISCOUNT ON NOW!! ENDS AUGUST 4! ==== Take control of a one-armed warrior named Sasha, wielding a living sword on her journey... | Read more »

Price Scanner via MacPrices.net

Second-Quarter Tablet Shipments Fell 4.8% –...
The latest report from the global market research firm TrendForce finds that worldwide tablet shipments for this second quarter totaled 33.54 million units, representing a quarterly drop of 4.8% and... Read more
Global Smartphone Sales Volumes Mark Second S...
According to preliminary results from the International Data Corporation (IDC) Worldwide Quarterly Mobile Phone Tracker, vendors shipped a total of 343.3 million smartphones worldwide in the second... Read more
Apple TVs on sale for $20-$40 off MSRP
Best Buy has 32GB and 64GB Apple TVs on sale for $20-$40 off MSRP on their online store. Choose free shipping or free local store pickup (if available). Sale prices for online orders only, in-store... Read more
Mac minis on sale for $50-$100 off MSRP
B&H Photo has Mac minis on sale for $50 off MSRP including free shipping plus NY sales tax only: - 1.4GHz Mac mini: $449 $50 off MSRP - 2.6GHz Mac mini: $649 $50 off MSRP - 2.8GHz Mac mini: $949... Read more
Clearance 2015 13-inch MacBook Airs available...
B&H Photo has clearance 2015 13″ MacBook Airs available for $300 off original MSRP. Shipping is free, and B&H charges NY sales tax only: - 13″ 1.6GHz/4GB/128GB MacBook Air (MJVE2LL/A): $799... Read more
Apple certified refurbished iPad mini 4s avai...
Apple has certified refurbished iPad mini 4s now available for up to $120 off the cost of new models. An Apple one-year warranty is included with each iPad, and shipping is free. The following models... Read more
Notebook Makers In No Rush To Adopt USB-C – R...
Digitimes’ Cage Chao and Joseph Tsai note that while the USB Type-C interface is enjoying growing popularity among smartphones and tablet makers, notebook and all-in-one (AIO) PC vendors (other than... Read more
iMacs on sale for up to $250 off MSRP
B&H Photo has 21″ and 27″ Apple iMacs on sale for up to $250 off MSRP including free shipping plus NY sales tax only: - 27″ 3.3GHz iMac 5K: $2049 $250 off MSRP - 27″ 3.2GHz/1TB Fusion iMac 5K: $... Read more
12-inch 1.1GHz Retina MacBooks on sale for up...
Amazon has 2016 12″ 1.1GHz/256GB Retina MacBooks on sale for up to $100 off MSRP including free shipping: - 12″ 1.1GHz Space Gray Retina MacBook: $1199 $100 off MSRP - 12″ 1.1GHz Silver Retina... Read more
Bare Bones Software Releases Free TextWrangle...
Bare Bones Software has announced the release and immediate availability of TextWrangler 5.5, a significant update to its powerful, free, general purpose text editor for Mac OS X. TextWrangler is a... Read more

Jobs Board

*Apple* Solutions Consultant - APPLE (United...
Job Summary As an Apple Solutions Consultant, you'll be the link between our future customers and our products. You'll showcase your entrepreneurial spirit as you Read more
Lead *Apple* Solutions Consultant - APPLE (...
Job Summary The Lead ASC is an Apple employee who serves as the Apple business manager and influencer across a number of Reseller locations. The Lead ASC's role Read more
*Apple* Retail - Multiple Positions, Charles...
Job Description:SalesSpecialist - Retail Customer Service and SalesTransform Apple Store visitors into loyal Apple customers. When customers enter the store, Read more
*Apple* Retail - Multiple Positions, Willow...
Job Description:SalesSpecialist - Retail Customer Service and SalesTransform Apple Store visitors into loyal Apple customers. When customers enter the store, Read more
*Apple* Evangelist - JAMF Software (United S...
The Apple Evangelist is responsible for building and cultivating strategic relationships with Apple 's small and mid-market business development field teams. This Read more
All contents are Copyright 1984-2011 by Xplain Corporation. All rights reserved. Theme designed by Icreon.