36-491: Android Runtime ( ART ) is an application runtime environment used by the Android operating system . Replacing Dalvik , the process virtual machine originally used by Android, ART performs the translation of the application's bytecode into native instructions that are later executed by the device's runtime environment. Android 2.2 "Froyo" brought trace-based just-in-time (JIT) compilation into Dalvik, optimizing
72-532: A P-code machine or virtual machine , that hide even the processor's instruction set . This is the approach followed by many interpreted languages such as AWK , and some languages like Java , which are meant to be compiled into some machine-independent intermediate representation code (such as bytecode ). This arrangement simplifies the task of language implementation and its adaptation to different machines, and improves efficiency of sophisticated language features such as reflective programming . It also allows
108-399: A runtime system or runtime environment is a sub-system that exists in the computer where a program is created, as well as in the computers where the program is intended to be run. The name comes from the compile time and runtime division from compiled languages , which similarly distinguishes the computer processes involved in the creation of a program (compilation) and its execution in
144-629: A hierarchy of runtime systems, with the CPU itself—or actually its logic at the microcode layer or below—acting as the lowest-level runtime system. Some compiled or interpreted languages provide an interface that allows application code to interact directly with the runtime system. An example is the Thread class in the Java language . The class allows code (that is animated by one thread) to do things such as start and stop other threads. Normally, core aspects of
180-438: A language's behavior such as task scheduling and resource management are not accessible in this fashion. Higher-level behaviors implemented by a runtime system may include tasks such as drawing text on the screen or making an Internet connection. It is often the case that operating systems provide these kinds of behaviors as well, and when available, the runtime system is implemented as an abstraction layer that translates
216-484: A runtime system may also perform support services such as type checking , debugging , or code generation and optimization . The runtime system is also the gateway through which a running program interacts with the runtime environment . The runtime environment includes not only accessible state values, but also active entities with which the program can interact during execution. For example, environment variables are features of many operating systems, and are part of
252-406: A runtime system that implements the execution model's behavior. Most scholarly papers on runtime systems focus on the implementation details of parallel runtime systems. A notable example of a parallel runtime system is Cilk , a popular parallel programming model. The proto-runtime toolkit was created to simplify the creation of parallel runtime systems. In addition to execution model behavior,
288-742: A similar device, which shortens download time from Google Play by up to 40%. Google Play cloud profiles allow apps to be optimized on installation, which helps avoid the initial performance issues present on Android 7.0 to 8.1. In July 2021, the concept of baseline profiles was introduced. Baseline profiles are ART profiles that define methods and classes which should undergo AOT compilation from an app's first launch, and are compatible with Android 7.0 and later. They provide similar functionality to Android 9's Google Play cloud profiles when they are not available and automatically merge with cloud profiles when they are available. Baseline profiles are included with releases of AndroidX libraries and Jetpack Compose . ART
324-471: Is "any behavior not directly attributable to the program itself". This definition includes putting parameters onto the stack before function calls, parallel execution of related behaviors, and disk I/O . By this definition, essentially every language has a runtime system, including compiled languages , interpreted languages , and embedded domain-specific languages . Even API -invoked standalone execution models, such as Pthreads ( POSIX threads ), have
360-522: Is frequently used, runs on the UI thread or affects startup time), which the AOT compiler compiles to machine code while the device is idle and charging. Less-frequently used code relies on JIT compilation. Android 9 "Pie" reduced the amount of storage used by APKs by using compressed bytecode files, and profiler data can be uploaded to Google Play servers to be bundled with apps when downloaded by users with
396-552: Is implemented by the Pthreads runtime system (this runtime system is often the OS kernel). As an extreme example, the physical CPU itself can be viewed as an implementation of the runtime system of a specific assembly language. In this view, the execution model is implemented by the physical CPU and memory systems. As an analogy, runtime systems for higher-level languages are themselves implemented using some other languages. This creates
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#1732776067926432-430: Is that additional time is required for compilation when an application is installed, and applications take up slightly more secondary storage (usually flash memory ) to store the compiled code. Android 4.4 "KitKat" introduced a technology preview of ART as an alternative runtime environment to Dalvik, which remained the default virtual machine. In the subsequent major Android release, Android 5.0 "Lollipop" , Dalvik
468-442: Is the case of using an application programming interface (API) to interact with a runtime system. The calls to that API look the same as calls to a regular software library , however at some point during the call the execution model changes. The runtime system implements an execution model different from that of the language the library is written in terms of. A person reading the code of a normal library would be able to understand
504-464: The C language is a particular set of instructions inserted by the compiler into the executable image. Among other things, these instructions manage the process stack, create space for local variables, and copy function call parameters onto the top of the stack. There are often no clear criteria for determining which language behaviors are part of the runtime system itself and which can be determined by any particular source program. For example, in C,
540-521: The Kotlin programming language, and provides a reactive programming model similar to other UI frameworks such as Vue.js and React Native . Compose is designed to integrate seamlessly with existing Android apps and libraries, allowing developers to gradually migrate their apps to Compose. In Compose, a user interface is defined using functions that have been annotated with the @Composable annotation, which are known as composable functions and define
576-556: The Play Store using Compose – in fact, the Play Store app itself uses Compose." As of October 2022, 160 of the top 1000 apps on the Play Store included Compose. The apps included those from companies such as Airbnb , Lyft and Square . Google rewrote parts of Android's Settings app using Compose in Android 14 . Meta Platforms developed its Threads social media app in five months using Compose. Compose Multiplatform
612-459: The application(s) running within that runtime environment. Any other code that tries to run, or any failures in the application(s), will break the runtime environment. Breaking the runtime environment in turn breaks the OS, stopping all processing and requiring a reboot. If the boot is from read-only memory, an extremely secure, simple, single-mission system is created. Examples of such directly bundled runtime systems include: The runtime system of
648-482: The execution model implemented by the runtime system. For example, the trap instruction is one method of switching execution models. This difference is what distinguishes an API-invoked execution model, such as Pthreads, from a usual software library. Both Pthreads calls and software library calls are invoked via an API, but Pthreads behavior cannot be understood in terms of the language of the call. Rather, Pthreads calls bring into play an outside execution model, which
684-410: 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 an application's bytecode, native execution of those short bytecode segments, called "traces", provides significant performance improvements. Unlike Dalvik, ART introduces
720-758: The framework was made ready for production in July 2021. The first preview of Jetpack Compose was announced at the Google I/O conference in May 2019. The developer preview was released in October 2019, and the alpha release took place in August 2020. Compose entered its beta phase in February 2021, with its first production release taking place that July. Jetpack Compose supports Android 5.0 and later. It uses
756-427: The invocation of the runtime system into an invocation of the operating system. This hides the complexity or variations in the services offered by different operating systems. This also implies that the OS kernel can itself be viewed as a runtime system, and that the set of OS calls that invoke OS behaviors may be viewed as interactions with a runtime system. In the limit, the runtime system may provide services such as
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#1732776067926792-458: The library's behavior by just knowing the language the library was written in. However, a person reading the code of the API that invokes a runtime system would not be able to understand the behavior of the API call just by knowing the language the call was written in. At some point, via some mechanism, the execution model stops being that of the language the call is written in and switches over to being
828-497: The proto-runtime approach. Notable early examples of runtime systems are the interpreters for BASIC and Lisp . These environments also included a garbage collector . Forth is an early example of a language designed to be compiled into intermediate representation code; its runtime system was a virtual machine that interpreted that code. Another popular, if theoretical, example is Donald Knuth 's MIX computer. In C and later languages that supported dynamic memory allocation,
864-426: The runtime environment. The object file, on one hand, may be missing information from the runtime environment that will be resolved by linking . On the other hand, the code in the object file still depends on assumptions in the runtime system; for example, a function may read parameters from a particular register or stack location, depending on the calling convention used by the runtime environment. Another example
900-410: The runtime environment; a running program can access them via the runtime system. Likewise, hardware devices such as disks or DVD drives are active entities that a program can interact with via a runtime system. One unique application of a runtime environment is its use within an operating system that only allows it to run. In other words, from boot until power-down, the entire OS is dedicated to only
936-430: The runtime system also included a library that managed the program's memory pool. In the object-oriented programming languages , the runtime system was often also responsible for dynamic type checking and resolving method references. Jetpack Compose Jetpack Compose is an open-source Kotlin -based declarative UI framework for Android developed by Google . The first preview was announced in May 2019, and
972-484: The same input bytecode as Dalvik, supplied through standard .dex files as part of APK files , while the .odex files are replaced with Executable and Linkable Format (ELF) executables. Once an application is compiled by using ART's on-device dex2oat utility, it is run solely from the compiled ELF executable; as a result, ART eliminates various application execution overheads associated with Dalvik's interpretation and trace-based JIT compilation. A disadvantage of ART
1008-711: The same program to be executed on any machine without an explicit recompiling step, a feature that has become very important since the proliferation of the World Wide Web . To speed up execution, some runtime systems feature just-in-time compilation to machine code. A modern aspect of runtime systems is parallel execution behaviors, such as the behaviors exhibited by mutex constructs in Pthreads and parallel section constructs in OpenMP . A runtime system with such parallel execution behaviors may be modularized according to
1044-480: The screen's state. The annotation is used by the Compose compiler to generate the UI boilerplate code . The 1.0 release introduced Compose Preview, which is built into Android Studio starting with Arctic Fox. It allows composables to be previewed using different configurations without deploying the app to a device. At the time of Jetpack Compose's 1.0 release, Google said, "There are already over 2,000 apps in
1080-416: The semantics of a particular program and the runtime environment is reflected by the different ways of compiling a program: compiling source code to an object file that contains all the functions versus compiling an entire program to an executable binary. The object file will only contain assembly code relevant to the included functions, while the executable binary will contain additional code that implements
1116-428: The setup of the stack is part of the runtime system. It is not determined by the semantics of an individual program because the behavior is globally invariant: it holds over all executions. This systematic behavior implements the execution model of the language, as opposed to implementing semantics of the particular program (in which text is directly translated into code that computes results). This separation between
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1152-478: The specific runtime system to generate correct code. Typically the runtime system will have some responsibility for setting up and managing the stack and heap , and may include features such as garbage collection , threads or other dynamic features built into the language. Every programming language specifies an execution model , and many implement at least part of that model in a runtime system. One possible definition of runtime system behavior, among others,
1188-450: The target machine (the runtime). Most programming languages have some form of runtime system that provides an environment in which programs run. This environment may address a number of issues including the management of application memory , how the program accesses variables , mechanisms for passing parameters between procedures , interfacing with the operating system (OS), among others. The compiler makes assumptions depending on
1224-620: The use of ahead-of-time (AOT) compilation by compiling entire applications into native machine code upon their installation. By eliminating Dalvik's interpretation and trace-based JIT compilation, ART improves the overall execution efficiency and reduces power consumption, which results in improved battery autonomy on mobile devices . At the same time, ART brings faster execution of applications, improved memory allocation and garbage collection (GC) mechanisms, new applications debugging features, and more accurate high-level profiling of applications. To maintain backward compatibility , ART uses
1260-429: Was entirely replaced by ART. Android 7.0 "Nougat" switched its Java Runtime Environment from the discontinued Apache Harmony to OpenJDK , introducing a JIT compiler with code profiling to ART, which lets it constantly improve the performance of Android apps as they run. The JIT compiler complements ART's AOT compiler, helping to improve runtime performance and save storage space by identifying "hot code" (code which
1296-577: Was updated with a new garbage collector (GC) utilizing the Linux userfaultfd system call in Android 13 . It reduces memory pressure, compiled code size and jank , and prevents the risk of killing apps because of low memory during garbage collection . Other changes also improve app startup, reduce jank and improve performance. Because of the Mainline project, Android 12 's ART will also be updated. Runtime environment In computer programming ,
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