Dalvik (software)
Dalvik is a discontinued
.dex
(Dalvik EXecutable) and .odex
(Optimized Dalvik EXecutable) files; related terms odex and de-odex are associated with respective bytecode conversions. The compact Dalvik Executable format is designed for systems that are constrained in terms of memory and processorThe successor of Dalvik is
is the first version in which ART is the only included runtime.History
Dalvik, named after a town in Iceland by its creator Dan Bronstein,
Dalvik was open sourced under
Architecture
Unlike
A tool called dx
is used to convert Java
The Dalvik executables may be modified again when installed onto a mobile device. In order to gain further
, and empty class objects may be short-circuited, for example.Being optimized for low memory requirements, Dalvik has some specific characteristics that differentiate it from other standard VMs:[11]
- The VM was slimmed down to use less space.
- The constant pool has been modified to use only 32-bit indices to simplify the interpreter.
- Standard Java bytecode executes 8-bit stack instructions. Local variables must be copied to or from the operand stack by separate instructions. Dalvik instead uses its own 16-bit instruction set that works directly on local variables. The local variable is commonly picked by a 4-bit "virtual register" field. This lowers Dalvik's instruction count and raises its interpreter speed.
According to Google, the design of Dalvik permits a device to run multiple instances of the VM efficiently.[12]
Performance
The relative merits of stack machines versus register-based approaches are a subject of ongoing debate.[16]
Generally, stack-based machines must use
Tests performed on
Furthermore, as of March 2014[update], benchmarks performed on an Android device still show up to a factor 100 between native applications and a Dalvik application on the same Android device.[19][original research?][improper synthesis?] Upon running benchmarks using the early interpreter of 2009, both Java Native Interface (JNI) and native code showed an order of magnitude speedup.[20]
Licensing and patents
Dalvik is published under the terms of the Apache License 2.0.[21] Some [who?] say that Dalvik is a clean-room implementation rather than a development on top of a standard Java runtime, which would mean it does not inherit copyright-based license restrictions from either the standard-edition or open-source-edition Java runtimes.[22] Oracle and some reviewers dispute this.[23]
On August 12, 2010, Oracle, which acquired Sun Microsystems in April 2009 and therefore owns the rights to Java, sued Google over claimed infringement of copyrights and patents. Oracle alleged that Google, in developing Android, knowingly, directly and repeatedly infringed Oracle's Java-related intellectual property.[24][25][26] In May 2012, the jury in this case found that Google did not infringe on Oracle's patents, and the trial judge ruled that the structure of the Java APIs used by Google was not copyrightable.[27][28] The parties agreed to zero dollars in statutory damages for 9 lines of copied code.[29][30]
See also
- Android Runtime
- Android software development
- Application virtualization
- Comparison of application virtualization software
- Comparison of Java and Android API
- JEB decompiler – a Dalvik (DEX and APK) decompiler
- Dalvik Turbo virtual machine – a proprietary alternative Dalvik implementation
References
- ^ "Debugging ART Garbage Collection". Retrieved 6 October 2015.
The Dalvik runtime is no longer maintained or available [in current versions of Android] and its byte-code format is now used by ART.
- ^ Journal entry referencing the source of the name
- ^ "Google Calling: Inside Android, the gPhone SDK". onlamp.com. Archived from the original on 2017-01-10. Retrieved 2008-02-05.
- ^ Sean Buckley (2013-11-06). "'ART' experiment in Android KitKat improves battery life and speeds up apps". Engadget. Retrieved 2014-07-05.
- ^ Daniel P. (2013-11-07). "Experimental Google ART runtime in Android KitKat can bring twice faster app executions". phonearena.com. Retrieved 2014-07-05.
- ^ a b Live Q&A with Dan Bornstein, Creator of the Dalvik VM. InfoQ. 29 Sep 2015 – via YouTube.
- ^ Google I/O 2008 - Dalvik Virtual Machine Internals. Google. 4 Jun 2008 – via YouTube.
- doi:10.1145/858570.858575. Archived from the original(PDF) on 1 Feb 2024.
- ^ Beschizza, Rob (12 Nov 2007). "Android SDK Open For Code". WIRED. Archived from the original on 31 Jan 2024.
- ^ Bornstein, Dan (2008-05-29). "Presentation of Dalvik VM Internals" (PDF). p. 22. Archived from the original (PDF) on 2017-04-16. Retrieved 2010-08-16.
- ^ Rose, John (2008-05-31). "with Android and Dalvik at Google I/O". Archived from the original on 2008-06-04. Retrieved 2008-06-08.
- ^ Google (2009-04-13). "What is Android?". Archived from the original on 2009-06-27. Retrieved 2009-04-19.
- ^ Ben Cheng; Bill Buzbee (May 2010). "A JIT Compiler for Android's Dalvik VM" (PDF). android-app-developer.co.uk. pp. 5–14. Archived from the original (PDF) on 2015-11-06. Retrieved March 18, 2015.
- ^ Phil Nickinson (May 26, 2010). "Google Android developer explains more about Dalvik and the JIT in Froyo". androidcentral.com. Archived from the original on 2014-07-14. Retrieved July 8, 2014.
- ^ "Nexus One Is Running Android 2.2 Froyo. How Fast Is It Compared To 2.1? Oh, Only About 450% Faster". 2010-05-13. Retrieved 2010-05-21.
- ^ Shi, Yunhe; Gregg, David; Beatty, Andrew; Ertl, M. Anton (2005-06-11). "Virtual Machine Showdown: Stack Versus Registers" (PDF). Retrieved 2009-12-22.
- ^ Vandette, Bob (2010-11-22). "Java SE Embedded Performance Versus Android 2.2". Oracle Corporation. Archived from the original on 2011-06-28. Retrieved 2011-09-04.
The results show that although Androids new JIT is an improvement over its interpreter only implementation, Android is still lagging behind the performance of our Hotspot enabled Java SE Embedded. As you can see from the above results, Java SE Embedded can execute Java bytecodes from 2 to 3 times faster than Android 2.2.
- S2CID 36316611.
In the JITC mode, however, Dakvik is slower than HotSpot by more than 2.9 times and its generated code size is not smaller than HotSpot's due to its worse code quality and trace-chaining code.
- ^ "Top AndEBench Scores". www.eembc.org. Retrieved 2014-03-23.
- S2CID 12131309.
The results show that native C applications can be up to 30 times as fast as an identical algorithm running in Dalvik VM. Java applications can become a speed-up of up to 10 times if utilizing JNI.
- ^ "Downloading the Source Tree - Android Open Source". Android.git.kernel.org. Archived from the original on 2009-04-17. Retrieved 2012-06-07.
- ^ Garling, Caleb. "Google and Oracle 'Experts' Clash over Android's Java Mimic". Wired.
- ZDNet. Retrieved 2011-11-27.
The definition of a "clean room" implementation is that the engineers writing the code have no direct exposure to the original, copyrighted material, including code, specifications, and other documentation. That's a problem for Google, as I noted in yesterday's post, because there is substantial evidence that the engineers working on the project had direct access to the copyrighted material.
- ^ "Oracle Sues Google Over Java in Android Devices". digitaltrends.com. 2010-08-13. Retrieved 2011-08-08.
- ^ James Niccolai (2010-08-12). "Oracle sues Google over Java use in Android". Computerworld. Retrieved 2010-08-13.
- PC Magazine. Ziff Davis.
- ^ Josh Lowensohn (May 23, 2012). "Jury clears Google of infringing on Oracle's patents". ZDNet. Retrieved 2012-05-25.
- ^ Joe Mullin (May 31, 2012). "Google wins crucial API ruling, Oracle's case decimated". Ars Technica. Retrieved 2012-06-01.
- ^ Niccolai, James (June 20, 2012). "Oracle agrees to 'zero' damages in Google lawsuit, eyes appeal". Archived from the original on 2023-04-01. Retrieved 2012-06-23.
- ^
Adam Outler (May 16, 2012). "Update on the Oracle Versus Google Trial". Archived from the original on 2013-05-16. Retrieved 2013-01-18.
A major portion of the Oracle's claims are based on 9 lines of code contained within Java.Util.Arrays.rangeCheck(). Here is the code in question:...
External links
- Dalvik bytecode – official Android documentation of the instruction set
- Dex Executable format – official Android documentation
- A JIT Compiler for Android's Dalvik VM on YouTube, Google I/O 2010, by Ben Cheng and Bill Buzbee
- Dalvik VM Internals Archived 2010-03-01 at the Wayback Machine, Google I/O 2008, by Dan Bornstein
- The $800 Million Dollar Question: What’s the Difference Between Trademark and Copyright?