Scott Thibault

Tempo: specializing systems applications and beyond

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Domain-specific languages: from design to implementation application to video device drivers generation

Domain-specific languages (DSL) have many potential advantages in terms of software engineering, ranging from increased productivity to the application of formal methods. Although they have been used in practice for decades, there has been little study of methodology or implementation tools for the DSL approach. We present our DSL approach and its application to a realistic domain: the generation of video display device drivers. The article focuses on the validation of our proposed framework for domain-specific languages, from design to implementation. The framework leads to a flexible design and structure, and provides automatic generation of efficient implementations of DSL programs. Additionally, we describe an example of a complete DSL for video display adaptors and the benefits of the DSL approach for this application. This demonstrates some of the generally claimed benefits of using DSLs: increased productivity, higher-level abstraction, and easier verification. This DSL has been fully implemented with our approach and is available. Compose project URL: http://www.irisa.fr/compose/gal.

A framework for application generator design

Application generators have been demonstrated as a successful approach to achieving software reuse and typically yields higher productivity gains than methods such as component-based reuse. Despite their advantages, industrial software developers are reluctant to adopt these methods due to the lack of tools for constructing generators. This paper presents a framework for the development of application generators. This framework provides a structured design approach and automatic tools for design. The framework consists of a two level design process: The first level is the identification of operations that expresses the fundamental computations of the application domain. The second level is the design of a domain-specific language which allows one to express variations within a family of applications. The domain-specific language is implemented in terms of the operations defined by the first level. We show that the uniform application of partial evaluation enables automatic application generation from a micro-program to its implementation. This framework has been developed in the context of real applications in areas such as Internet services and digital television, and is being developed in conjunction with industrial partners.

Static and Dynamic Program Compilation by Interpreter Specialization

Interpretation and run-time compilation techniques are increasingly important because they can support heterogeneous architectures, evolving programming languages, and dynamically-loaded code. Interpretation is simple to implement, but yields poor performance. Run-time compilation yields better performance, but is costly to implement. One way to preserve simplicity but obtain good performance is to apply program specialization to an interpreter in order to generate an efficient implementation of the program automatically. Such specialization can be carried out at both compile time and run time.Recent advances in program-specialization technology have significantly improved the performance of specialized interpreters. This paper presents and assesses experiments applying program specialization to both bytecode and structured-language interpreters. The results show that for some general-purpose bytecode languages, specialization of an interpreter can yield speedups of up to a factor of four, while specializing certain structured-language interpreters can yield performance comparable to that of an implementation in a general-purpose language, compiled using an optimizing compiler.

Adapting distributed applications using extensible networks

Active networks have been proposed to allow the dynamic extension of network behavior by downloading application-specific protocols (ASPs) into network routers. We demonstrate the feasibility of the use of ASPs in an active network for the adaptation of distributed software components. We have implemented three examples which show that ASPs can be used to easily extend distributed applications, and furthermore, that such adaptation can be safe, portable and efficient. Safety and efficiency is obtained by implementing the ASPs in PLAN-P, a domain-specific language and run-time system for active networking. The presented examples illustrate three different applications: audio broadcasting with bandwidth adaptation in routers; an extensible HTTP server with load-balancing facilities; and a multipoint MPEG server derived from a point-to-point server.

Mapping software architectures to efficient implementations via partial evaluation

Flexibility is recognized as a key feature in structuring software, and many architectures have been designed to that effect. However, they often come with performance and code size overhead, resulting in a flexibility vs. efficiency dilemma. The source of inefficiency in software architectures can be identified in the data and control integration of components, because flexibility is present not only at the design level but also in the implementation. We propose the use of program specialization in software engineering as a systematic way to improve performance and in some cases, to reduce program size. In particular, we advocate the use of partial evaluation, which is an automatic technique to produce efficient, specialized instances of generic programs. We study several representative, flexible mechanisms found in software architectures: selective broadcast, pattern matching, interpreters, layers, and generic libraries. We show how partial evaluation can systematically be applied in order to optimize those mechanisms.

Efficient Implementations of Software Architectures via Partial Evaluation

The notion of flexibility (that is, the ability to adapt to changing requirements or execution contexts) is recognized as a key concern in structuring software, and many architectures have been designed to that effect. However, the corresponding implementations often come with performance and code size overheads. The source of inefficiency can be identified to be in the loose integration of components, because flexibility is often present not only at the design level but also in the implementation. To solve this flexibility vs. efficiency dilemma, we advocate the use of partial evaluation, which is an automated technique to produce efficient, specialized instances of generic programs. As supporting case studies, we consider several flexible mechanisms commonly found in software architectures: selective broadcast, pattern matching, interpreters, software layers, and generic libraries. Using Tempo, our specializer for C, we show how partial evaluation can safely optimize implementations of those mechanisms. Because this optimization is automatic, it preserves the original genericity and extensibility of the implementation.

Partial evaluation for software engineering

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A domain-specific language approach to programmable networks

Active networks present significant safety, security, and efficiency challenges. Domain-specific languages, i.e., languages providing only constructs relevant to a particular domain, provide a solution that balances these constraints. Safety and security can be ensured using verification techniques that exploit the restricted nature of such languages. Strategies have been developed for the compilation of domain-specific languages that provide both portability and efficiency. This paper presents a synthesis of work on the PLAN-P domain-specific language for programmable routers. We present the language design, representative experiments that have been carried out using the language, and new compilation strategies. End-to-end performance is typically comparable to that of hand-coded C implementations.