The Da Vinci Machine, also called the Multi Language Virtual Machine, was a

Sun Microsystems Sun Microsystems, Inc., often known as Sun for short, was an American technology company that existed from 1982 to 2010 which developed and sold computers, computer components, software, and information technology services. Sun contributed sig ...

project aiming to prototype the extension of the

Java Virtual Machine A Java virtual machine (JVM) is a virtual machine that enables a computer to run Java programs as well as programs written in other languages that are also compiled to Java bytecode. The JVM is detailed by a specification that formally descr ...

(JVM) to add support for dynamic languages. It was already possible to run dynamic languages on top of the JVM, but the goal is to ease new dynamic language implementations and increase their performance. This project was the

reference implementation In the software development process, a reference implementation (or, less frequently, sample implementation or model implementation) is a program that implements all requirements from a corresponding specification. The reference implementation ...

of JSR 292 (''Supporting Dynamically Typed Languages on the Java Platform'').see JSR 292
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History

Prior to Java 7, the

had no built-in support for dynamically typed languages: * The existing JVM instruction set is

statically typed In computer programming, a type system is a logical system comprising a set of rules that assigns a property called a ''type'' (for example, integer, floating point, string) to every '' term'' (a word, phrase, or other set of symbols). Usu ...

. * JVM has limited support for dynamically modifying existing classes and methods. It currently works only in a debugging environment. JSR 292 (''Supporting Dynamically Typed Languages on the Java Platform'') proposes to: * add a new invokedynamic instruction at the JVM level, to allow method invocation relying on dynamic

type checking In computer programming, a type system is a logical system comprising a set of rules that assigns a property called a ''type'' (for example, integer, floating point, string) to every '' term'' (a word, phrase, or other set of symbols). Usu ...

, * to be able to change classes and methods at runtime dynamically in a production environment. Following the success of the

JRuby JRuby is an implementation of the Ruby programming language atop the Java Virtual Machine, written largely in Java. It is free software released under a three-way EPL/ GPL/LGPL license. JRuby is tightly integrated with Java to allow the embeddi ...

Java Java is one of the Greater Sunda Islands in Indonesia. It is bordered by the Indian Ocean to the south and the Java Sea (a part of Pacific Ocean) to the north. With a population of 156.9 million people (including Madura) in mid 2024, proje ...

implementation, the Da Vinci project was started at the end of January 2008. The capabilities experimented by Da Vinci were planned to be added to Java 7. It aims to prototype this JSR, but also other lower-priority extensions. The first working prototype, developed as a patch on

OpenJDK OpenJDK (Open Java Development Kit) is a free and open-source implementation of the Java Platform, Standard Edition (Java SE). It is the result of an effort Sun Microsystems began in 2006, four years before the company was acquired by Oracle Corp ...

, was announced and made available on end of August 2008. Since then, the

team has successfully wired dynamic invocation in their codebase. Dynamic invocation shipped with the 1.1.5 release, and will be disabled on

JVM A Java virtual machine (JVM) is a virtual machine that enables a computer to run Java programs as well as programs written in other languages that are also compiled to Java bytecode. The JVM is detailed by a specification that formally descri ...

s without invokedynamic capabilities. Since then, the project has been integrated in the JDK 7 codebase and then integrated in the Java 7 release.

Architecture

Dynamic invocation is built on the fact that, even if Java is a strongly static language at the language level, the type information is much less prevalent at the

bytecode Bytecode (also called portable code or p-code) is a form of instruction set designed for efficient execution by a software interpreter. Unlike human-readable source code, bytecodes are compact numeric codes, constants, and references (normal ...

level. However, dynamic languages implementations need to be able to use

just-in-time compilation In computing, just-in-time (JIT) compilation (also dynamic translation or run-time compilations) is compilation (of computer code) during execution of a program (at run time) rather than before execution. This may consist of source code transl ...

(rather than

reflection Reflection or reflexion may refer to: Science and technology * Reflection (physics), a common wave phenomenon ** Specular reflection, mirror-like reflection of waves from a surface *** Mirror image, a reflection in a mirror or in water ** Diffuse r ...

) to achieve good performance, and so to compile scripts to bytecode at runtime. To be allowed to be run by the

, these bytecodes must be verified prior to the execution, and the verifier check that the types are static throughout the code. It leads to these implementations having to create many different bytecodes for the different contexts of a method call, each time the

signature A signature (; from , "to sign") is a depiction of someone's name, nickname, or even a simple "X" or other mark that a person writes on documents as a proof of identity and intent. Signatures are often, but not always, Handwriting, handwritt ...

of the

arguments An argument is a series of sentences, statements, or propositions some of which are called premises and one is the conclusion. The purpose of an argument is to give reasons for one's conclusion via justification, explanation, and/or persua ...

change. This not only uses a lot of memory, but also fills a memory area called Metaspace (Permanent Generation prior to Java 8), a part of the heap used by the JVM to store information about classes. Memory used in this area is almost never garbage collected because it stores immutable data in the context of Java programs; and because of that, dynamic languages implementations can only compile a small part of the scripts. JSR 292 proposes to: * provide a mechanism whereby an existing class can be loaded and modified, producing a new class with those modifications but sharing the rest of its structure and data, thus not filling the Permanent Generation space, * provide the new invokedynamic bytecode which allows the JVM to optimize calls of this kind.

References

External links

Da Vinci Machine project pageSun presentation at Lang.NET SymposiumJohn Rose (project leader) blogJSR 292 ACM 2010 presentation paper
{Dead link, date=November 2019 , bot=InternetArchiveBot , fix-attempted=yes Java virtual machine Java platform software Beta software Java specification requests Sun Microsystems software

History

Architecture

See also

References

External links