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Next-Gen JavaScript Interpreter Speeds Up WebKit
JavaScript is everywhere these days. Now WebKit, the framework behind (among others) Safari and Safari Mobile, as well as the yet-unreleased Android, is getting a new JavaScript engine called Squirrelfish, which the developers claim provides massive speedups over the previous one. The current iteration of the engine is "just the beginning," they claim; in the near future, six planned optimizations should bring even greater speed. With JavaScript surviving as a Web-page mainstay despite many early gripes, and now integral to some low-powered mobile devices, this may mean many fewer wasted seconds in the world.
According to this link, the SquirrelFish in the latest nightly build (without the extra optimizations) can already compile *and* run the source code between 1.08x and 1.94x as fast as Tamarin when Tamarin is just running pre-compiled code. It's fast.
E pluribus unum
Javascript is doing more than just surviving. Early implementations of Javascript were quite buggy and standards were pretty lax. Things have improved significantly since "Javascript" became ECMAScript. The name may still have "script" in it, but it's a huge misnomer. Javascript is a full-fledged language - a very powerful one with many unique properties, and very useful if you know how to apply design patterns.
I encourage anyone involved in building websites, widgets, or enterprise applications to check out the Javascript lecture series by Douglas Crockford of Yahoo! located at http://video.yahoo.com/video/play?vid=111585 to get a real feel for the power of modern Javascript.
And have a look at the modern AJAX frameworks like YUI and JQuery, which are being used to develop some pretty complex applications.
-- thinkyhead software and media
It's an engine that complies (or at least tries to) with standards.
upon the advice of my lawyer, i have no sig at this time
Oh yes I can tell you: konqueror is coming with khtml by default. There's a webkitkpart ()which is not quite ready) and there's a GSoC student working on it though so it might work better at end of this summer. IF you want an open source browser in linux using Webkit, you can use Arora: http://code.google.com/p/arora/ or the epiphany branch that uses webkit.
I agree, Safari for Windows is actually a bit tempting, especially if "hacking" it a bit (actually, it can probably not even be called "hacking" in geek circles at least) to use the latest WebKit builds. The only downside of that one is its (sorry..) piss poor memory performance. It's worse than pretty much anything I've tried. A few hours browsing and I had it use 300-400 MB RAM. That's like the bad old Firefox 2 days at worst, from my experiences. It's worse than IE 7 too.
Beware: In C++, your friends can see your privates!
He's not commenting on stateless applications, but the stateless quality of http. Every time the browser communicates with the server, it has the exact same overhead, whether it's an ajax request or a full web page. The amount that's sent back may differ, but it's still sending all the information associated with instantiating a new connection, sending information about the browser, all the cookies, etc. When you build stateful applications on top of http, you incur a lot of overhead in those headers and cookies being sent back and forth. For applications trying to stay synced to the server, some people have found overhead of over 75%. This inefficiency's being made up for in packing more information into each request, stretching requests out to take up more time, and just plain fast processors and connections.
The GP is saying that if we had a stateful protocol, we could eliminate most of the overhead and make applications move a lot faster.
The fastest dynamic language implementation at the moment is Objective-C. This isn't as fast as it could be in the GCC implementation (I'm working on it in LLVM, and hope to have some nice speedups soon), but it's not far off. This compiles dynamic lookups to fast native code and compiles everything else to static code.
Next up in terms of speed are the various Smalltalks. Something like GNU Smalltalk does well in terms of speed. It JIT compiles things in a way quite similar to Objective-C, but with a very naive compiler with very little optimisation. This is slightly faster than something like Squeak, which compiles to bytecode and interprets this. Bytecode is generally quite fast. Basically, the interpreter is a loop which contains a switch statement. Each instruction is a fixed size with (typically) the first byte being an opcode, and so this is compiled to a static jump table and the 'decode' cost for each instruction is a load and a jump. This is slightly slower than naive compilation, but not much. In some cases it can be faster, because your interpreter is likely to be compiled with a compiler that does quite aggressive optimisation and so you may get fewer register spills than something like GNU Smalltalk (which lacks a peephole optimiser, for example). The new JavaScript interpreter is of this nature - it compiles to bytecode and then interprets this.
Even slower are interpreters which try to run the AST directly. These turn each statement (or part of a statement) into a generic operation and step through these. This is what the old WebKit implementation did.
Part of the problem with this kind of thing is that you are always trading compile time for run time. The benchmarks they published take around 10 seconds to do a complete run. This includes both your compile and run time. If you take more than a second to compile, people will notice. If you take one second to parse, and then execute the AST slowly, you may take 10 seconds in total. If you take one second to parse and four seconds to compile and optimise then you need to get a 500% speedup just to break even - your perceived speed will be the same. This is why things the StrongTalk and Self VMs did dynamic profiling - they began by interpreting everything, but if you spent a lot of time executing a part of the code, it will aggressively optimise it. The newer Java VMs do the same thing.
For most JavaScript, this is a complete waste of time. It is very rare for JavaScript to run for more than a fraction of a second at a time and so latency caused by interrupting execution much worse than just running it slightly more slowly. The ActionScript VM in Flash is very different, since it is designed to run scripts that stay running for minutes at a time and are fairly CPU intensive. If people start using JavaScript and canvas tags or SVG in the same way as they use Flash, then a JS runtime with a JIT compiler and optimiser is likely to be a win.
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On a mac, it's simple to install and remove the WebKit nightly. It's literally just dragging and dropping a specially built application.
Now, you'll only be using the webkit libraries when browsing with that gold WebKit icon. To prove this to yourself, you can visit the Acid3 test page using both Safari and Webkit without quitting either and see very different results. Safari still has major incompatibilities while WebKit seems almost perfect.
Finally, when you are ready to uninstall WebKit, quit the app and drag the gold colored icon from the applications folder to the trash. Or, drag a new version that you download the next day on top to replace the old nightly.