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Integrating nominal and structural subtyping

22nd European conference on Object-Oriented programming (ECOOP 2008)

作者： Malayeri, Donna Aldrich, Jonathan Carnegie Mellon Univ Pittsburgh PA 15213 USA

ISBN: (纸本)9783540705918

Nominal and structural subtyping each have their own strengths and weaknesses. Nominal subtyping allows programmers to explicitly express design intent, and, when types are associated with run time tags, enables run-time type tests and external method dispatch. On the other hand, structural subtyping is flexible and compositional, allowing unanticipated reuse. To date, nearly all object-oriented languages fully support one subtyping paradigm or the other. In this paper, we describe a core calculus for a language that integrates the key aspects of nominal and structural subtyping in a unified framework. We have also merged the flexibility of structural subtyping with statically typechecked external methods, a novel combination. We prove type safety for this language and illustrate its practical utility through examples that are not easily expressed in other languages. Our work provides a clean foundation for the design of future languages that enjoy the benefits of both nominal and structural subtyping.

关键词： Object oriented programming

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Xoc, an extension-oriented compiler for systems programming

Xoc, an extension-oriented compiler for systems programming

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13th International conference on Architectural Support for programming languages and Operating Systems

作者： Cox, Russ Bergan, Tom Clements, Austin T. Kaashoek, Frans Kohler, Eddie MIT CSAIL UCLA CS

ISBN: (纸本)9781595939586

Today's system programmers go to great lengths to extend the languages in which they program. For instance, system-specific compilers find errors in Linux and other systems, and add support for specialized control flow to Qt and event-based programs. These compilers are difficult to build and cannot always understand each other's language changes. However, they can greatly improve code understandability and correctness, advantages that should be accessible to all programmers. We describe an extension-oriented compiler for C called xoc. An extension-oriented compiler, unlike a conventional extensible compiler, implements new features via many small extensions that are loaded together as needed. Xoc gives extension writers full control over program syntax and semantics while hiding many compiler internals. Xoc programmers concisely define powerful compiler extensions that, by construction, can be combined;even some parts of the base compiler, such as GNU C compatibility, are structured as extensions. Xoc is based on two key interfaces. Syntax patterns allow extension writers to manipulate language fragments using concrete syntax. Lazy computation of attributes allows extension writers to use the results of analyses by other extensions or the core without needing to worry about pass scheduling. Extensions built using xoc include xsparse, a 345-line extension that mimics Sparse, Linux's C front end, and xlambda, a 170-line extension that adds function expressions to C. An evaluation of xoc using these and 13 other extensions shows that xoc extensions are typically more concise than equivalent extensions written for conventional extensible compilers and that it is possible to compose extensions.

关键词： languages design experimentation extension-oriented compilers

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Principles of a reversible programming language 08

Principles of a reversible programming language

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2008 conference on Computing Frontiers, CF'08

作者： Yokoyama, Tetsuo Axelsen, Holger Bock Glück, Robert Graduate School of Information Science Nagoya University Furo-cho Chikusa-ku Nagoya 464-8601 Japan DIKU Department of Computer Science University of Copenhagen Universitetsparken 1 DK-2100 Copenhagen Ø Denmark

ISBN: (纸本)9781605580777

The principles of reversible programming languages are explicated and ilhistrated with reference to the design of a high-level imperative language, Janus. The fundamental properties for such languages include backward as well as forward determinism and reversible updates of data. The unique design features of the language include explicit postcondition assertions, direct access to an inverse semantics and the possibility of clean (i.e., garbage-free) computation of injective functions. We suggest the clean simulation of reversible Turing machines as a criterion for computing strength of reversible languages, and demonstrate this for Janus. We show the practicality of the language by implementation of a reversible fast Fourier transform. Our results indicate that the reversible programming paradigm has fundamental properties that are relevant to many different areas of computer science. Copyright 2008 acm.

关键词： Fast Fourier transforms

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Parallelism by design: Data analysis with Sawzall 08

Parallelism by design: Data analysis with Sawzall

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6th International Symposium on Code Generation and Optimization, CGO 2008

作者： Griesemer, Robert Google Inc. Mountain View CA United States

ISBN: (纸本)9781595939784

Very large data sets - telephone call records, network logs, high-resolution satellite images, or web document repositories - are not easily analyzed using traditional database techniques. They may be simply too large, grow too fast, or may not fit well in a database schema. They tend to span multiple disks and machines. On the other hand, these large data sets often have a flat and regular structure that permits distributed filtering and aggregation. We present a system and language for such analyses*. A filtering phase, in which a query is expressed using the procedural programming language Sawzall, emits data to an aggregation phase. Both phases are distributed over hundreds or even thousands of computers. The language constructs and execution model of Sawzall have been devised to enable parallel execution without the need for complex dependency analysis. Even with our fairly traditional implementation of the Sawzall execution engine we observe nearly perfect scalability as we add more machines.

关键词： Parallel algorithms

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Understanding the propagation of hard errors to software and implications for resilient system design

Understanding the propagation of hard errors to software and...

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13th International conference on Architectural Support for programming languages and Operating Systems

作者： Li, Man-Lap Ramachandran, Pradeep Sahoo, Swarup K. Adve, Sarita V. Adve, Vikram S. Zhou, Yuanyuan Univ Illinois Dept Comp Sci Urbana IL 61801 USA

ISBN: (纸本)9781595939586

With continued CMOS scaling, future shipped hardware will be increasingly vulnerable to in-the-field faults. To be broadly deployable, the hardware reliability solution must incur low overheads, precluding use of expensive redundancy. We explore a cooperative hardware-software solution that watches for anomalous software behavior to indicate the presence of hardware faults. Fundamental to such a solution is a characterization of how hardware faults in different micro architectural structures of a modern processor propagate through the application and OS. This paper aims to provide such a characterization, resulting in identifying low-cost detection methods and providing guidelines for implementation of the recovery and diagnosis components of such a reliability solution. We focus on hard faults because they are increasingly important and have different system implications than the much studied transients. We achieve our goals through fault injection experiments with a micro architecture-level full system timing simulator. Our main results are: (1) we are able to detect 95% of the unmasked faults in 7 out of 8 studied micro architectural structures with simple detectors that incur zero to little hardware overhead;(2) over 86% of these detections are within latencies that existing hardware checkpointing schemes can handle, while others require software checkpointing;and (3) a surprisingly large fraction of the detected faults corrupt OS state, but almost all of these are detected with latencies short enough to use hardware checkpointing, thereby enabling OS recovery in virtually all such cases.

关键词： reliability experimentation design error detection architecture permanent fault fault injection

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The VISITOR Pattern as a Reusable, Generic, Type-Safe Component 08

The VISITOR Pattern as a Reusable, Generic, Type-Safe Compon...

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23rd Annual acm conference on Object-Oriented programming, Systems, languages and Applications

作者： Oliveira, Bruno C. d. S. Wang, Meng Gibbons, Jeremy Univ Oxford Comp Lab Oxford OX1 3QD England

ISBN: (纸本)9781605582153

The VISITOR design pattern shows how to separate the structure of an object hierarchy from the behaviour of traversals over that hierarchy. The pattern is very flexible;this very flexibility makes it difficult to capture the pattern as anything more formal than prose, pictures and prototypes. We show how to capture the essence of the VISITOR pattern as a reusable software library, by using advanced type system features appearing in modern object-oriented languages such as Scala. We preserve type-safety statically and modularly: no reflection or similar mechanisms are used and modules can be independently compiled. The library is generic, in two senses: not only is it parametrised by both the return type and the shape of the object hierarchy, but also it allows a number of implementation choices (internal versus external control, imperative versus functional behaviour, orthogonal aspects such as tracing and memoisation) to be specified by parameters rather than fixed in early design decisions. Finally, we propose a generalised datatype-like notation, on top of our visitor library: this provides a convenient functional decomposition style in object-oriented languages.

关键词： design Patterns Visitor Pattern Software Components Program Extensibility Algebraic Datatypes Traversal

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Re-engineering the algorithmA project for long-term maintenance

Re-engineering the algorithmA project for long-term maintena...

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23rd acm sigplan conference on Object Oriented programming Systems languages and Applications,OOPSLA 2008

作者： James, Willie Lucas, Phil O'Connor, John Concepcion, Arturo I 793-2853 United States 750-9482 United States 813-0120 United States 537-5330 United States

The AlgorithmA project has been in existence since 1991 and is used as an on-going project in the software engineering class taught at CSUSB. In 1998, the project was first implemented on the Internet using Java. In 2007, the maintenance of the project was a big challenge because of the size of the project and the complexity of the architectural design. This paper talks about the decision process of the software engineering class that led to the re-engineering of the entire AlgorithmA project, which is a situation that actually happens in a real software company. The observations and experiences of the project manager, the team leader of the maintenance team, and the team leader of the Java team that implemented the re-design of the project, are discussed in this paper. In 2008, the project was continued by forward engineering the original functions of AlgorithmA. The re-design followed the Model/View/Controller (MVC) model and using the Observer and Factory patterns, made the AlgorithmA project maintainable and extensible for many more years to come.

关键词： Java programming language

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Safer Unsafe Code for .NET 08

Safer Unsafe Code for .NET

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23rd Annual acm conference on Object-Oriented programming, Systems, languages and Applications

作者： Ferrara, Pietro Logozzo, Francesco Faehndrich, Manuel Ecole Polytech F-91128 Palaiseau France Microsoft Res Redmond WA 98052 USA

ISBN: (纸本)9781605582153

The NET intermediate language (MSIL) allows expressing both statically verifiable memory and type safe code (typically called managed), as well as unsafe code using direct pointer manipulations. Unsafe code can be expressed in C# by marking regions of code as unsafe. Writing unsafe code can be useful where the rules of managed code are too strict. The obvious drawback of unsafe code is that it opens the door to programming errors typical of C and C++, namely memory access errors such as buffer overruns. Worse, a single piece of unsafe code may corrupt memory and destabilize the entire runtime or allow attackers to compromise the security of the platform. We present a new static analysis based on abstract interpretation to check memory safety for unsafe code in the .NET framework. The core of the analysis is a new numerical abstract domain, Strp, which is used to efficiently compute memory invariants. Strp is combined with lightweight abstract domains to raise the precision, yet achieving scalability. We implemented this analysis in Clousot, a generic static analyzer for NET. In combination with contracts expressed in FoxTrot, an MSIL based annotation language for NET, our analysis provides static safety guarantees on memory accesses in unsafe code. We tested it on all the assemblies of the NET framework. We compare our results with those obtained using existing domains, showing how they are either too imprecise (e.g., Intervals or Octagons) or too expensive (Polyhedra) to be used in practice.

关键词： Abstract domains Abstract interpretation Bounds checking Pointer indexing design by Contract Static analysis .NET

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Hardware counter driven on-the-fly request signatures

Hardware counter driven on-the-fly request signatures

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13th International conference on Architectural Support for programming languages and Operating Systems

作者： Shen, Kai Zhong, Ming Dwarkadas, Sandhya Li, Chuanpeng Stewart, Christopher Zhang, Xiao Univ Rochester Dept Comp Sci Rochester NY 14627 USA

ISBN: (纸本)9781595939586

Today's processors provide a rich source of statistical information on application execution through hardware counters. In this paper, we explore the utilization of these statistics as request signatures in server applications for identifying requests and inferring high-level request properties (e.g., CPU and I/O resource needs). Our key finding is that effective request signatures may be constructed using a small amount of hardware statistics while the request is still in an early stage of its execution. Such on-the-fly request identification and property inference allow guided operating system adaptation at request granularity (e.g., resource-aware request scheduling and on-the-fly request classification). We address the challenges of selecting hardware counter metrics for signature construction and providing necessary operating system support for per-request statistics management. Our implementation in the Linux 2.6.10 kernel suggests that our approach requires low overhead suitable for runtime deployment. Our on-the-fly request resource consumption inference (averaging 7%, 3%, 20%, and 41% prediction errors for four server workloads, TPC-C, TPC-H, J2EE-based RUBiS, and a trace-driven index search, respectively) is much more accurate than the online running-average based prediction (73-82% errors). Its use for resource-aware request scheduling results in a 15-70% response time reduction for three CPU-bound applications. Its use for on-die-fly request classification and anomaly detection exhibits high accuracy for the TPC-H workload with synthetically generated anomalous requests following a typical SQL-injection attack pattern.

关键词： measurement performance design reliability experimentation operating system adaptation hardware counter server system request classification anomaly detection

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Polymorphism and page tables - Systems programming from a functional programmer's perspective

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acm sigplan NOTICES 2008年第9期43卷 265-265页

作者： Jones, Mark P. Portland State Univ Portland OR 97207 USA

With features that include lightweight syntax, expressive type systems, and deep semantic foundations, functional languages are now being used to develop an increasingly broad range of complex, real-world applications. In the area of systems software, however, where performance and interaction with low-level aspects of hardware are central concerns, many practitioners still eschew the advantages of higher-level languages for the potentially unsafe but predictable behavior of traditional imperative languages like C. It is ironic that critical applications such as operating systems kernels, device drivers, and VMMs-where a single bug could compromise the reliability or security of a whole system-are among the least likely to benefit from the abstractions and safety guarantees of modern language designs. Over the last few years, our group has been investigating the potential for using Haskell to develop realistic operating systems that can boot and run on bare metal. The House system, developed primarily by Thomas Hallgren and Andrew Tolmach, demonstrates that it is indeed possible to construct systems software in a functional language. But House still relies on a layer of runtime support primitives-some written using unsafe Haskell primitives and others written in C-to provide services ranging from garbage collection to control of the page table structures used by the hardware memory management unit. We would like to replace as much of this layer as possible with code written in a functional language without compromising on type or memory safety. Our experiences with House have led us to believe that a new functional language is required to reflect the needs of the systems domain more directly. Interestingly, however, we have concluded that this does not require fundamental new language design. In this invited talk, I will give an update on the current status of our project and I will describe how we are leveraging familiar components of the Haskell type system-includ

关键词： design languages reliability functional programming systems programming type systems data representation memory manipulation

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