The next major version of Android, which will probably be unveiled at Google I/O next week, will remove the Dalvik runtime and replace it with ART — the new Android Runtime. The main purpose of ART is to improve performance and smoothness of the core Android platform and stock apps, and third-party Android apps. Battery life and other core metrics should also be significantly improved. Brian Carlstrom, a member of Google’s Dalvik engineering team, announced the Dalvik-ART switch-over with this rather amusing patch note: “Dalvik is dead, long live Dalvik! DO NOT MERGE.”
Google first debuted ART back in November 2013 with the release of Android 4.4 KitKat. At the time it was an experimental feature that you could enable if you were feeling adventurous (Settings > Developer Options > Select Runtime). With lots of extra feedback from the community, and hundreds of patches since then, Google now seems confident that ART is ready to replace Dalvik entirely.
Dalvik and ART are fundamentally different beasts, compiling and executing code in very different ways. Dalvik primarily uses a just-in-time (JIT) compiler that compiles code when you run an app; ART uses an ahead-of-time (AOT) compiler that compiles to machine code when you install the app. In theory this can speed up execution time significantly, and thus also increase battery life and some other important metrics. ART also introduces better garbage collection, which should improve performance and responsiveness. For more technical details, the Android ART developer pages are pretty good. Developers may have to make a few changes to their apps/processes, but ART is mostly a drop-in replacement.
From an end-user perspective, the introduction of ART as the default Android runtime probably won’t blow you away. Early benchmarks show performance improvements (~10%) in some applications, but slowdowns in other areas. By the time ART is officially introduced, those slowdowns (due to bugs and incompleteness) should be gone. As with any big change, ART’s benefits won’t really shine until Google and third-party app developers optimize their apps. Presumably the next major version of Android (4.5 or 5.0) will be optimized for ART, and will thus the interface and stock apps will be very fast and efficient. The next major version could be unveiled at Google I/O next week (though I reckon the 4.4 branch still has a ways to run).
The ultimate goal of ART is to make Android a slicker, more responsive platform — an area where iOS has historically dominated. There’s also the possibility that ART is a reaction to the ongoing court case between Oracle and Google over Dalvik — Oracle claims that Dalvik infringes on its Java IP, and so far it looks like Oracle will win the suit. By moving away from Dalvik, Google might save itself (and its developers) a lot of expensive, litigious hurt.
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