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Opera is building a new JavaScript engine. And one day, the Norwegian browser mavens say, it will be the fastest the web has ever seen.

Under development for several months now, the new engine is known as Carakan, and according to private Norwegian tests, it's already two and a half times faster than the JavaScript engine woven into the recently released Opera 10 alpha.

The world calls it JavaScript. But the Browserati know better.

Bolstad tells The Reg he aims to release a Carakan public build "in the next few months - before the summer, basically." It will not be rolled into Opera 10, due for an official release around the middle of the year.

Opera's core-technology team has overhauled their JavaScript - er, ECMAScript - engine in three distinct ways. For one, they've switched from a stack-based bytecode instruction set to a register-based set. Rather than using a single stack of values, Carakan stores values in fixed registers accessible by any instruction.

Since there's no need to copy values to and from the top of a stack, fewer instructions are executed and less data is copied, Bolstad explains.

Two, Carakan will compile portions of ECMAScript programs into native code. This will reduce some of the overhead required to execute certain ECMAScript code in a bytecode interpreter. The native code will look a lot like assembly code, Bolstad says, so that most of it will stay in those registers.

And three, the new engine will improve the way ECMAScript objects are represented. Each object is assigned a class that collects certain data about the object. "This representation allows compact storage of individual objects, since most of the complicated structures representing the object's properties are stored in the class, where they are shared with all other objects with the same class," Bolstad writes.

"In real-world programs with many objects of the same classes, this can save significant amounts of memory. It can be expected that most programs that do create many objects still only have a few different classes of objects."

Bolstad tells us Carakan is now "feature complete." But he and his team are still tweaking the native-code-compilation bit. Running the SunSpider benchmark, Carakan is currently two and a half times faster on ECMAScript than the Opera 10 alpha, aka Presto 2.2. With native-code generation, Bolstad expects significantly greater speed improvements. Some preliminary tests indicate that the native-code Carakan will be 5 to 50 times faster than Opera 10.

Like Opera predecessors - including Futhark, Linear A, and Linear B - the new engine shares its name with a much older breed of script. Carakan is both modern-day JavaScript engine and pre-colonial Javanese script. ®

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