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Android Power User: What is the Dalvik VM? What is the Dalvik Cache?
Android Power User: What is the Dalvik VM? What is the Dalvik Cache?
Published: 2012/09/19
Channel: Pocketnow
Dalvik VM - Deep dive into what makes the Android apps run
Dalvik VM - Deep dive into what makes the Android apps run
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Xamarin vs Dalvik: start up time
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chC4 - Android Runtime - The Dalvik Virtual Machine
chC4 - Android Runtime - The Dalvik Virtual Machine
Published: 2010/12/11
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Samsung Galaxy S5 - Dalvik vs ART
Samsung Galaxy S5 - Dalvik vs ART
Published: 2014/04/22
Channel: Chris Nacca
Android Basics 101: Understanding ART, the Android Runtime
Android Basics 101: Understanding ART, the Android Runtime
Published: 2014/02/12
Channel: xdadevelopers
Running Android Apps on the iPad with Myriad
Running Android Apps on the iPad with Myriad's Alien Dalvik
Published: 2011/10/21
Channel: Mobilegeeks.de
Myriad Alien Dalvik Demo, Q&A
Myriad Alien Dalvik Demo, Q&A
Published: 2011/02/15
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Debugging Android Dalvik and native code seamlessly with JEB
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Run Android Apps on iPad 2 using Alien Dalvik 2 0
Published: 2011/10/11
Channel: zaone ro
Understanding Android Run Time, Dalvik and APK
Understanding Android Run Time, Dalvik and APK
Published: 2016/05/11
Channel: Why Android
22 How to use Dalvik Debug Monitor Server DDMS - Android App Development Tutorial For Dummies
22 How to use Dalvik Debug Monitor Server DDMS - Android App Development Tutorial For Dummies
Published: 2015/06/15
Channel: Harsha S Srinivas
Android Application Security Demo: Dalvik bytecode reverse engineering (Flappy Bird clone)
Android Application Security Demo: Dalvik bytecode reverse engineering (Flappy Bird clone)
Published: 2014/06/10
Channel: Licel
Download JavaFX-Dalvik Runtime
Download JavaFX-Dalvik Runtime
Published: 2014/09/26
Channel: Andr.oid Eric
ART vs Dalvik: Explained - Android Galaxy Greece
ART vs Dalvik: Explained - Android Galaxy Greece
Published: 2014/02/09
Channel: Andreas Stefanou
Android Programming Course - Chapter 2 - The Dalvik VM
Android Programming Course - Chapter 2 - The Dalvik VM
Published: 2013/10/22
Channel: Learn By The Byte
Que es el Dalvik Cache y como eliminarlo
Que es el Dalvik Cache y como eliminarlo
Published: 2014/03/27
Channel: ConsejosAndroid
Myriad Alien Dalvik Demo 2.0
Myriad Alien Dalvik Demo 2.0
Published: 2011/10/10
Channel: myriadgroupmarketing
First "In-The-Box" Project demo: Dalvik running on iOS!
First "In-The-Box" Project demo: Dalvik running on iOS!
Published: 2011/05/24
Channel: InTheBoxProject
How to switch from Dalvik to ART in Android
How to switch from Dalvik to ART in Android
Published: 2013/12/14
Channel: Anthony Farrior
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اندرويد دالفك ضد اي ار تي !؟ dalvik vs A.R.T
Published: 2014/10/04
Channel: Dargooz
Resolve Conversion To Dalvik Format Failed With Error
Resolve Conversion To Dalvik Format Failed With Error
Published: 2015/12/19
Channel: Indragni Soft Solutions
Android tutorial in hindi lec -2  What is DVM (How does android works.)
Android tutorial in hindi lec -2 What is DVM (How does android works.)
Published: 2016/09/14
Channel: JavaTreePoint
Diferencias técnicas entre ART y Dalvik - ¿Como funciona Android?
Diferencias técnicas entre ART y Dalvik - ¿Como funciona Android?
Published: 2015/02/17
Channel: latincoder
Switching to ART from Dalvik
Switching to ART from Dalvik
Published: 2014/03/20
Channel: Ryan Ferguson
Blackberry Playbook to get Android Dalvik engine support?
Blackberry Playbook to get Android Dalvik engine support?
Published: 2011/02/16
Channel: Charbax
Android in 60 Seconds   Dalvik
Android in 60 Seconds Dalvik
Published: 2012/04/03
Channel: Kophes
Myriad Alien Dalvik Demo
Myriad Alien Dalvik Demo
Published: 2011/04/30
Channel: thehandheldsite
Dalvik Cache clean with Titanium Backup
Dalvik Cache clean with Titanium Backup
Published: 2014/10/18
Channel: Michael Lange
Conversion to Dalvik format failed Error
Conversion to Dalvik format failed Error
Published: 2014/09/13
Channel: Coming Soon
Dalvik Apps Introduction
Dalvik Apps Introduction
Published: 2015/01/05
Channel: Dalvik Apps
"Conversion to Dalvik format failed with error 1" in eclipse
"Conversion to Dalvik format failed with error 1" in eclipse
Published: 2015/03/29
Channel: Videos Adda
Dalvik Vs Art en #androidIO
Dalvik Vs Art en #androidIO
Published: 2014/04/17
Channel: DesarrolloWeb.com
[Android] What is Dalvik virtual machine?
[Android] What is Dalvik virtual machine?
Published: 2016/12/15
Channel: Olo Technic
Experimenta sustituir Dalvik por ART para mejorar el rendimiento en Android 4.4 KitKat (Tutorial)
Experimenta sustituir Dalvik por ART para mejorar el rendimiento en Android 4.4 KitKat (Tutorial)
Published: 2013/12/06
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Dalvik VM   Deep dive into what makes the Android apps run clip4
Dalvik VM Deep dive into what makes the Android apps run clip4
Published: 2014/09/30
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Speed up Nexus 5 with Moto X Dalvik Optimizations [Android 4.4 KitKat]
Speed up Nexus 5 with Moto X Dalvik Optimizations [Android 4.4 KitKat]
Published: 2013/11/22
Channel: AppReviewBros
Dalvik VM   Deep dive into what makes the Android apps run clip3
Dalvik VM Deep dive into what makes the Android apps run clip3
Published: 2014/09/30
Channel: HUONG 01
Dalvik VM   Deep dive into what makes the Android apps run clip16
Dalvik VM Deep dive into what makes the Android apps run clip16
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Dalvik VM   Deep dive into what makes the Android apps run clip7
Dalvik VM Deep dive into what makes the Android apps run clip7
Published: 2014/09/30
Channel: HUONG 06
ART vs. Dalvik (Lollipop vs Kitkat) galaxy s5 benchmark 1080p
ART vs. Dalvik (Lollipop vs Kitkat) galaxy s5 benchmark 1080p
Published: 2015/08/27
Channel: gamer30168
LCU14-100: Dalvik is Dead, Long Live Dalvik! OR Tuning ART
LCU14-100: Dalvik is Dead, Long Live Dalvik! OR Tuning ART
Published: 2014/09/15
Channel: Linaro On Air
Myriad Dalvik Turbo speeds up Android (3D cubes benchmark)
Myriad Dalvik Turbo speeds up Android (3D cubes benchmark)
Published: 2010/02/12
Channel: myriadgroupmarketing
Dalvik VM   Deep dive into what makes the Android apps run clip5
Dalvik VM Deep dive into what makes the Android apps run clip5
Published: 2014/09/30
Channel: HUONG 07
Dalvik VM   Deep dive into what makes the Android apps run clip12
Dalvik VM Deep dive into what makes the Android apps run clip12
Published: 2014/09/30
Channel: HUONG 04
Dalvik vs Fastiva vs Art
Dalvik vs Fastiva vs Art
Published: 2014/09/18
Channel: 지대훈
Dalvik VM   Deep dive into what makes the Android apps run clip18
Dalvik VM Deep dive into what makes the Android apps run clip18
Published: 2014/09/30
Channel: HUONG 01
CCS 2016 - Computational Soundness for Dalvik Bytecode
CCS 2016 - Computational Soundness for Dalvik Bytecode
Published: 2016/11/08
Channel: CCS 2016
Dalvik VM - Deep dive into what makes the Android apps run - Preview video by Satyam
Dalvik VM - Deep dive into what makes the Android apps run - Preview video by Satyam
Published: 2013/11/25
Channel: HasGeek TV
Activar opciones desarrollador. Cambiar Dalvik por ART y mejorar la velocidad de Android
Activar opciones desarrollador. Cambiar Dalvik por ART y mejorar la velocidad de Android
Published: 2014/05/19
Channel: Juan Cascón Baños
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WIKIPEDIA ARTICLE

From Wikipedia, the free encyclopedia
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Dalvik
Original author(s) Dan Bornstein
Operating system Linux kernel
Platform Android
Type Virtual machine
License Apache License 2.0
Website source.android.com/devices/tech/dalvik/index.html
Dalvik Executable
Filename extension .dex

Dalvik is a discontinued[1] process virtual machine (VM) in Google's Android operating system that executes applications written for Android. Dalvik is an integral part of the Android software stack in Android versions 4.4 "KitKat" and earlier, which is typically used on mobile devices such as mobile phones and tablet computers, and more recently on devices such as smart TVs and wearables. Dalvik is open-source software, originally written by Dan Bornstein, who named it after the fishing village of Dalvík in Eyjafjörður, Iceland.[2][3]

Programs for Android are commonly written in Java and compiled to bytecode for the Java virtual machine, which is then translated to Dalvik bytecode and stored in .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 processor speed.

The successor of Dalvik is Android Runtime (ART), which uses the same bytecode and .dex files (but not .odex files), with the succession aiming at performance improvements transparent to the end users. The new runtime environment was included for the first time in Android 4.4 "KitKat" as a technology preview,[4][5] and replaced Dalvik entirely in later versions; Android 5.0 "Lollipop" is the first version in which ART is the only included runtime.[6]

Architecture[edit]

A comparison of Dalvik and ART architectures

Unlike Java VMs, which are stack machines, the Dalvik VM uses a register-based architecture that requires fewer, typically more complex, virtual machine instructions. Dalvik programs are written in Java using the Android application programming interface (API), compiled to Java bytecode, and converted to Dalvik instructions as necessary.

A tool called dx is used to convert Java .class files into the .dex format. Multiple classes are included in a single .dex file. Duplicate strings and other constants used in multiple class files are included only once in the .dex output to conserve space. Java bytecode is also converted into an alternative instruction set used by the Dalvik VM. An uncompressed .dex file is typically a few percent smaller in size than a compressed Java archive (JAR) derived from the same .class files.[7]

The Dalvik executables may be modified again when installed onto a mobile device. In order to gain further optimizations, byte order may be swapped in certain data, simple data structures and function libraries may be linked inline, 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:[8]

  • 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.[9]

Android 2.2 "Froyo" brought trace-based just-in-time (JIT) compilation into Dalvik, optimizing the execution of applications by continually profiling applications each time they run and dynamically compiling frequently executed short segments of their bytecode into native machine code. While Dalvik interprets the rest of application's bytecode, native execution of those short bytecode segments, called "traces", provides significant performance improvements.[10][11][12]

Performance[edit]

A Dalvik-powered phone

The relative merits of stack machines versus register-based approaches are a subject of ongoing debate.[13]

Generally, stack-based machines must use instructions to load data on the stack and manipulate that data, and, thus, require more instructions than register machines to implement the same high-level code, but the instructions in a register machine must encode the source and destination registers and, therefore, tend to be larger. This difference is of importance to VM interpreters, for which opcode dispatch tends to be expensive, along with other factors similarly relevant to just-in-time compilation.

Tests performed on ARMv7 devices in 2010 by Oracle (owner of the Java technology) with standard non-graphical Java benchmarks showed the HotSpot VM of Java SE embedded to be 2–3 times faster than the JIT-based Dalvik VM of Android 2.2 (the initial Android release that included a JIT compiler).[14] In 2012, academic benchmarks confirmed the factor of 3 between HotSpot and Dalvik on the same Android board, also noting that Dalvik code was not smaller than Hotspot.[15]

Furthermore, as of March 2014, 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.[16][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.[17]

Licensing and patents[edit]

Dalvik is published under the terms of the Apache License 2.0.[18] Some say [citation needed] 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. Oracle and some reviewers dispute this.[19]

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.[20][21][22] 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.[23][24] The parties agreed to zero dollars in statutory damages for 9 lines of copied code.[25][26]

See also[edit]

References[edit]

  1. ^ "Debugging ART Garbage Collection". Retrieved 6 October 2015. The Dalvik runtime is no longer maintained or available [in latest versions of Android] and its byte-code format is now used by ART. 
  2. ^ Journal entry referencing the source of the name
  3. ^ "Google Calling: Inside Android, the gPhone SDK". onlamp.com. Retrieved 2008-02-05. 
  4. ^ Sean Buckley (2013-11-06). "'ART' experiment in Android KitKat improves battery life and speeds up apps". Engadget. Retrieved 2014-07-05. 
  5. ^ Daniel P. (2013-11-07). "Experimental Google ART runtime in Android KitKat can bring twice faster app executions". phonearena.com. Retrieved 2014-07-05. 
  6. ^ Brad Linder (October 15, 2014). "What's new in Android 5.0 Lollipop?". liliputing.com. Retrieved October 15, 2014. 
  7. ^ Bornstein, Dan (2008-05-29). "Presentation of Dalvik VM Internals" (PDF). Google. p. 22. Retrieved 2010-08-16. 
  8. ^ Rose, John (2008-05-31). "with Android and Dalvik at Google I/O". Retrieved 2008-06-08. 
  9. ^ Google (2009-04-13). "What is Android?". Retrieved 2009-04-19. 
  10. ^ Ben Cheng; Bill Buzbee (May 2010). "A JIT Compiler for Android's Dalvik VM" (PDF). android-app-developer.co.uk. Google. pp. 5–14. Retrieved March 18, 2015. 
  11. ^ Phil Nickinson (May 26, 2010). "Google Android developer explains more about Dalvik and the JIT in Froyo". androidcentral.com. Retrieved July 8, 2014. 
  12. ^ "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. 
  13. ^ Shi, Yunhe; Gregg, David; Beatty, Andrew; Ertl, M. Anton (2005-06-11). "Virtual Machine Showdown: Stack Versus Registers" (PDF). Retrieved 2009-12-22. 
  14. ^ Vandette, Bob (2010-11-22). "Java SE Embedded Performance Versus Android 2.2". Oracle Corporation. 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. 
  15. ^ Hyeong-Seok Oh; Beom-Jun Kim; Hyung-Kyu Choi; Soo-Mook Moon (2012). "Evaluation of Android Dalvik virtual machine". Association for Computing Machinery. Retrieved 2014-03-23. 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. 
  16. ^ "Top AndEBench Scores". www.eembc.org. Retrieved 2014-03-23. 
  17. ^ "Developing and Benchmarking Native Linux Applications on Android". Lecture Notes of the Institute for Computer Sciences, Social Informatics and Telecommunications Engineering. Springer Publishing. 2009-04-29. Retrieved 2014-03-23. 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. 
  18. ^ "Downloading the Source Tree - Android Open Source". Android.git.kernel.org. Archived from the original on 2009-04-17. Retrieved 2012-06-07. 
  19. ^ Ed Bott (September 8, 2011). "The real history of Java and Android, as told by Google". 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.  
  20. ^ "Oracle Sues Google Over Java in Android Devices". digitaltrends.com. 2010-08-13. Retrieved 2011-08-08. 
  21. ^ James Niccolai (2010-08-12). "Oracle sues Google over Java use in Android". Computerworld. Retrieved 2010-08-13. 
  22. ^ Mark Hachman (2010-08-13). "Oracle Sues Google Over Android Java Use". PC Magazine. Ziff Davis. 
  23. ^ Josh Lowensohn (May 23, 2012). "Jury clears Google of infringing on Oracle's patents". ZDNet. Retrieved 2012-05-25. 
  24. ^ Joe Mullin (May 31, 2012). "Google wins crucial API ruling, Oracle’s case decimated". Ars Technica. Retrieved 2012-06-01. 
  25. ^ Niccolai, James (June 20, 2012). "Oracle agrees to 'zero' damages in Google lawsuit, eyes appeal". Retrieved 2012-06-23. 
  26. ^ Adam Outler (May 16, 2012). "Update on the Oracle Versus Google Trial". 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[edit]

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