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Gaston Hillar

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Parallel Worker 0.2.0

June 06, 2011

The newest releases of modern Mobile Internet Devices (MIDs) established dual-core CPUs as the baseline hardware we can expect. HTML 5 brought Web Workers and the possibility of running multithreaded code with JavaScript. Parallel Worker 0.2.0 makes use of jQuery 1.5 deferred objects to represent workers that run in different threads.

If you want a Rich Internet Application (RIA) to be compatible with most modern MIDs, you usually have to work with JavaScript or jQuery and HTML. Because the default browsers provided by most MIDs are already compatible with HTML 5, you can use HTML 5 Web Workers to run code in multiple threads and to take advantage of the available cores.

jQuery 1.5 introduced the deferred object. jQuery.Deferred() is a chainable utility object that can register multiple callbacks into callback queues, invoke callback queues, and relay the success or failure state of any synchronous or asynchronous function. If you have experience with JavaScript or jQuery, you already know how to work with asynchronous code. jQuery.Deferred() makes it easy to chain asynchronous functions.

However, jQuery.Deferred() is not enough when you want to run multithreaded JavaScript. Parallel Worker 0.2.0 is a jQuery plugin that gives you the ability to run code in a new thread (it requires jQuery 1.5 because it uses deferred objects to represent HTML 5 Web Workers). Parallel Worker makes it easy to run code in different threads, handle errors, and join when multiple workers have finished their work in different threads.

If you want to provide a responsive UI and you have a lot of time-consuming JavaScript code in your RIA, you can easily split your JavaScript code in more than one thread by using Parallel Worker. However, it is very important to consider that creating a worker introduces an overhead and you should carefully weigh whether the benefits of running code in another thread really introduce a performance advantage. In addition, if you have many AJAX calls, remember that it's also possible to run the back-end code in parallel to provide a better response time. Don't forget that multicore hardware is available both in the computer or mobile device that executes the Web browser and in the Web or Cloud servers. Thus, whenever you move to improve UI response times, you have to analyze the different alternatives.

I have no doubts that Parallel Worker will make it easy to start parallelizing existing JavaScript code. Jonathan Cardy wrote a very interesting post with recommendations about Parallel Worker usage scenarios and included a few examples of its basic application. You can read Jonathan's post here and you can download the latest version of this jQuery plugin here. jQuery goes parallel, too. [For more information on jQuery, see Dino Esposito's series on the topic.]

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