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jducoeurWeb programmers should take a look at this article in Ars Technica, which talks about a radical enhancement that will be coming to Mozilla soon.
Summary: they're about to integrate trace optimization into the Spidermonkey Javascript engine. The underlying concept of this technique (assuming that I'm understanding it correctly) is essentially that it learns as it goes, making the program faster as it figures out how it really works in practice. This notion isn't quite as new as they make it sound, but this would be the widest deployment of it that I've heard about so far. In principle, it could eventually allow some Javascript programs to run *faster* than compiled code, because trace optimization can accomplish some speedups that compilers can't.
From the numbers they show, it looks like the new Javascript engine performs something like twice as fast in ordinary conditions, and up to 20-40 times faster in some cases. (Probably involving key loops that can be optimized well.) While that doesn't totally change the world yet, it's another key step in turning Javascript from an annoying and clunky toy into a language capable of serious work. And it means that, at least in Firefox, some complex web apps are about to get a speedup without having to do a thing. (It also means that the browser itself is likely to speed up in many places, because much of it is written in Javascript...)
Summary: they're about to integrate trace optimization into the Spidermonkey Javascript engine. The underlying concept of this technique (assuming that I'm understanding it correctly) is essentially that it learns as it goes, making the program faster as it figures out how it really works in practice. This notion isn't quite as new as they make it sound, but this would be the widest deployment of it that I've heard about so far. In principle, it could eventually allow some Javascript programs to run *faster* than compiled code, because trace optimization can accomplish some speedups that compilers can't.
From the numbers they show, it looks like the new Javascript engine performs something like twice as fast in ordinary conditions, and up to 20-40 times faster in some cases. (Probably involving key loops that can be optimized well.) While that doesn't totally change the world yet, it's another key step in turning Javascript from an annoying and clunky toy into a language capable of serious work. And it means that, at least in Firefox, some complex web apps are about to get a speedup without having to do a thing. (It also means that the browser itself is likely to speed up in many places, because much of it is written in Javascript...)
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Trace optimization in compilers
Date: 2008-08-25 08:36 pm (UTC)JITs don't necessarily do trace optimization; some do, apparently, but the basic JIT generates machine code at runtime, but does so without any knowledge of how the code is used. The only real reason for doing it at runtime is if you want to be able to distribute a machine-independent program (e.g., Java bytecode).