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Scrap Your Boilerplate with Object Algebras

acm sigplan NOTICES 2015年第10期50卷 127-146页

作者： Zhang, Haoyuan Chu, Zewei Oliveira, Bruno C. D. S. van der Storm, Tijs Univ Hong Kong Hong Kong Hong Kong Peoples R China CWI Amsterdam Netherlands

Traversing complex Abstract Syntax Trees (ASTs) typically requires large amounts of tedious boilerplate code. For many operations most of the code simply walks the structure, and only a small portion of the code implements the functionality that motivated the traversal in the first place. This paper presents a type-safe Java framework called Shy that removes much of this boilerplate code. In Shy Object Algebras are used to describe complex and extensible AST structures. Using Java annotations Shy generates generic boilerplate code for various types of traversals. For a concrete traversal, users of Shy can then inherit from the generated code and override only the interesting cases. Consequently, the amount of code that users need to write is significantly smaller. Moreover, traversals using the Shy framework are also much more structure shy, becoming more adaptive to future changes or extensions to the AST structure. To prove the effectiveness of the approach, we applied Shy in the implementation of a domain-specific questionnaire language. Our results show that for a large number of traversals there was a significant reduction in the amount of user-defined code.

关键词： languages Object algebras boilerplate code Java adaptive object-oriented programming

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Tracing vs. Partial Evaluation Comparing Meta-Compilation Approaches for Self-Optimizing Interpreters

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acm sigplan NOTICES 2015年第10期50卷 821-839页

作者： Marr, Stefan Ducasse, Stephane INRIA Lille France

Tracing and partial evaluation have been proposed as meta-compilation techniques for interpreters to make just-in-time compilation language-independent. They promise that programs executing on simple interpreters can reach performance of the same order of magnitude as if they would be executed on state-of-the-art virtual machines with highly optimizing just-in-time compilers built for a specific language. Tracing and partial evaluation approach this metacompilation from two ends of a spectrum, resulting in different sets of tradeoffs. This study investigates both approaches in the context of self-optimizing interpreters, a technique for building fast abstract-syntax-tree interpreters. Based on RPython for tracing and Truffle for partial evaluation, we assess the two approaches by comparing the impact of various optimizations on the performance of an interpreter for SOM, an object-oriented dynamically-typed language. The goal is to determine whether either approach yields clear performance or engineering benefits. We find that tracing and partial evaluation both reach roughly the same level of performance. SOM based on meta-tracing is on average 3 x slower than Java, while SOM based on partial evaluation is on average 2 : 3 x slower than Java. With respect to the engineering, tracing has however significant benefits, because it requires language implementers to apply fewer optimizations to reach the same level of performance.

关键词： languages Performance language implementation just-in-time compilation meta-tracing partial evaluation comparison case study self-optimizing interpreters

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Automatic Locality-Friendly Interface Extension of Numerical Functions 2014

Automatic Locality-Friendly Interface Extension of Numerical...

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13th conference on Generative programming - Concepts and Experiences (GPCE)

作者： Hess, Benjamin Gross, Thomas R. Pueschel, Markus Swiss Fed Inst Technol Dept Comp Sci Zurich Switzerland

ISBN: (纸本)9781450331616

Raising the level of abstraction is a key concern of software engineering, and libraries (either used directly or as a target of a program generation system) are a successful technique to raise programmer productivity and to improve software quality. Unfortunately successful libraries may contain functions that may not be general enough. For example, many numeric performance libraries contain functions that work on one-or higher-dimensional arrays. A problem arises if a program wants to invoke such a function on a non-contiguous subarray (e.g., in C the column of a matrix or a subarray of an image). If the library developer did not foresee this scenario, the client program must include explicit copy steps before and after the library function call, incurring a possibly high performance penalty. A better solution would be an enhanced library function that allows for the desired access pattern. Exposing the access pattern allows the compiler to optimize for the intended usage scenario(s). As we do not want the library developer to generate all interesting versions manually, we present a tool that takes a library function written in C and generates such a customized function for typical accesses. We describe the approach, discuss limitations, and report on the performance. As example access patterns we consider those most common in numerical applications: striding and block striding, general permutations, as well as scaling. We evaluate the tool on various library functions including filters, scans, reductions, sorting, FFTs, and linear algebra operations. The automatically generated custom version is in most cases significantly faster than using individual steps, offering speed-ups that are typically in the range of 1.2-1.8x.

关键词： Performance design Libraries components performance interface extension preprocessors programming language features interaction software product lines

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Vectorization of Apply to Reduce Interpretation Overhead of R

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acm sigplan NOTICES 2015年第10期50卷 400-415页

作者： Wang, Haichuan Padua, David Wu, Peng Univ Illinois Urbana IL 61801 USA Huawei R&D USA Santa Clara CA USA

R is a popular dynamic language designed for statistical computing. Despite R's huge user base, the inefficiency in R's language implementation becomes a major pain-point in everyday use as well as an obstacle to apply R to solve large scale analytics problems. The two most common approaches to improve the performance of dynamic languages are: implementing more efficient interpretation strategies and extending the interpreter with Just-In-Time (JIT) compiler. However, both approaches require significant changes to the interpreter, and complicate the adoption by development teams as a result. This paper presents a new approach to improve execution efficiency of R programs by vectorizing the widely used Apply class of operations. Apply accepts two parameters: a function and a collection of input data elements. The standard implementation of Apply iteratively invokes the input function with each element in the data collection. Our approach combines data transformation and function vectorization to convert the looping-over-data execution of the standard Apply into a single invocation of a vectorized function that contains a sequence of vector operations over the input data. This conversion can significantly speed-up the execution of Apply operations in R by reducing the number of interpretation steps. We implemented the vectorization transformation as an R package. To enable the optimization, all that is needed is to invoke the package, and the user can use a normal R interpreter without any changes. The evaluation shows that the proposed method delivers significant performance improvements for a collection of data analysis algorithm benchmarks. This is achieved without any native code generation and using only a single-thread of execution.

关键词： language Transformation Performance Dynamic language R Vectorization

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Cross-Layer Memory Management for Managed language Applications

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acm sigplan NOTICES 2015年第10期50卷 488-504页

作者： Jantz, Michael R. Robinson, Forrest J. Kulkarni, Prasad A. Doshi, Kshitij A. Univ Tennessee Knoxville TN 37996 USA Univ Kansas Lawrence KS 66045 USA Intel Corp Santa Clara CA 95051 USA

Performance and energy efficiency in memory have become critically important for a wide range of computing domains. However, it is difficult to control and optimize memory power and performance because these effects depend upon activity across multiple layers of the vertical execution stack. To address this challenge, we construct a novel and collaborative framework that employs object placement, cross-layer communication, and page-level management to effectively distribute application objects in the DRAM hardware to achieve desired power/performance goals. In this work, we describe the design and implementation of our framework, which is the first to integrate automatic object profiling and analysis at the application layer with fine-grained management of memory hardware resources in the operating system. We demonstrate the utility of our framework by employing it to more effectively control memory power consumption. We design a custom memory-intensive workload to show the potential of our approach. Next, we develop sampling and profiling-based analyses and modify the code generator in the HotSpot VM to understand object usage patterns and automatically determine and control the placement of hot and cold objects in a partitioned VM heap. This information is communicated to the operating system, which uses it to map the logical application pages to the appropriate DRAM ranks according to user-defined provisioning goals. We evaluate our framework and find that it achieves our test goal of significant DRAM energy savings across a variety of workloads, without any source code modifications or recompilations.

关键词： design Experimentation Performance Cross-layer Power Efficiency DRAM HotSpot

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Use at Your Own Risk: The Java Unsafe API in the Wild

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acm sigplan NOTICES 2015年第10期50卷 695-710页

作者： Mastrangelo, Luis Ponzanelli, Luca Mocci, Andrea Lanza, Michele Hauswirth, Matthias Nystrom, Nathaniel USI Fac Informat Lugano Switzerland

Java is a safe language. Its runtime environment provides strong safety guarantees that any Java application can rely on. Or so we think. We show that the runtime actually does not provide these guarantees-for a large fraction of today's Java code. Unbeknownst to many application developers, the Java runtime includes a "backdoor" that allows expert library and framework developers to circumvent Java's safety guarantees. This backdoor is there by design, and is well known to experts, as it enables them to write high-performance "systems-level" code in Java. For much the same reasons that safe languages are preferred over unsafe languages, these powerful-but unsafe-capabilities in Java should be restricted. They should be made safe by changing the language, the runtime system, or the libraries. At the very least, their use should be restricted. This paper is a step in that direction. We analyzed 74 GB of compiled Java code, spread over 86, 479 Java archives, to determine how Java's unsafe capabilities are used in real-world libraries and applications. We found that 25% of Java bytecode archives depend on unsafe third-party Java code, and thus Java's safety guarantees cannot be trusted. We identify 14 different usage patterns of Java's unsafe capabilities, and we provide supporting evidence for why real-world code needs these capabilities. Our long-term goal is to provide a foundation for the design of new language features to regain safety in Java.

关键词： design languages Measurement unsafe patterns mining Java Maven Central Stack Overflow

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A Partial Read Barrier for Efficient Support of Live Object-Oriented programming

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acm sigplan NOTICES 2015年第11期50卷 93-104页

作者： Miranda, Eliot Bera, Clement Cadence Design Syst New York NY USA RMOD INRIA Lille Nord Europe Lyon France

Live programming, originally introduced by Smalltalk and Lisp, and now gaining popularity in contemporary systems such as Swift, requires on-the-fly support for object schema migration, such that the layout of objects may be changed while the program is at one and the same time being run and developed. In Smalltalk schema migration is supported by two primitives, one that answers a collection of all instances of a class, and one that exchanges the identities of pairs of objects, called the become primitive. Existing instances are collected, copies using the new schema created, state copied from old to new, and the two exchanged with become, effecting the schema migration. Historically the implementation of become has either required an extra level of indirection between an object's address and its body, slowing down slot access, or has required a sweep of all objects, a very slow operation on large heaps. Spur, a new object representation and memory manager for Smalltalk-like languages, has neither of these deficiencies. It uses direct pointers but still provides a fast become operation in large heaps, thanks to forwarding objects that when read conceptually answer another object and a partial read barrier that avoids the cost of explicitly checking for forwarding objects on the vast majority of object accesses.

关键词： Live programming schema migration object representation garbage collection language virtual machine forwarding pointer read barrier

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Vector Parallelism in JavaScript: language and compiler support for SIMD 24

Vector Parallelism in JavaScript: Language and compiler supp...

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24th International conference on Parallel Architecture and Compilation (PACT)

作者： Jibaja, Ivan Jensen, Peter Hu, Ningxin Haghighat, Mohammad R. McCutchan, John Gohman, Dan Blackburn, Stephen M. McKinley, Kathryn S. Univ Texas Austin Austin TX 78712 USA Intel Corp Santa Clara CA 95051 USA Google Inc Menlo Pk CA USA Mozilla Mountain View CA USA Australian Natl Univ Canberra ACT 0200 Australia Microsoft Res Cambridge England

ISBN: (纸本)9781467395243

JavaScript is the most widely used web programming language and is increasingly used to implement sophisticated and demanding applications in such domains as graphics, games, video, and cryptography. The performance and energy usage of these applications can benefit from hardware parallelism, including SIMD (Single Instruction, Multiple Data) vector parallel instructions. JavaScript's current support for parallelism is, however, limited and does not directly utilize SIMD capabilities. This paper presents the design and implementation of SIMD language extensions and compiler support that together add fine-grain vector parallelism to JavaScript. The specification for this language extension is in final stages of adoption by the JavaScript standardization committee and our compiler support is available in two open-source production browsers. The design principles seek portability, SIMD performance portability on various SIMD architectures, and compiler simplicity to ease adoption. The design does not require automatic vectorization compiler technology, but does not preclude it either. The SIMD extensions define immutable fixed-length SIMD data types and operations that are common to both ARM and x86 ISAs. The contributions of this work include type speculation and optimizations that generate minimal numbers of SIMD native instructions from high-level JavaScript SIMD instructions. We implement type speculation, optimizations, and code generation in two open-source JavaScript VMs and measure performance improvements between a factor of 1.7x to 8.9x with an average of 3.3x and average energy improvements of 2.9x on micro benchmarks and key graphics kernels on various hardware, browsers, and operating systems. These portable SIMD language extensions significantly improve compute-intensive interactive applications in the browser, such as games and media processing, by exploiting vector parallelism without relying on automatic vectorizing compiler technology, non-portable na

关键词： JavaScript SIMD performance power energy parallelism vector HTML5 browser hardware web

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PLDI'09 - Proceedings of the 2009 acm sigplan conference on programming language design and implementation

PLDI'09 - Proceedings of the 2009 ACM SIGPLAN Conference on ...

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2009 acm sigplan conference on programming language design and implementation, PLDI'09

ISBN: (纸本)9781605583921

The proceedings contain 41 papers. The topics discussed include: dynamic software updates: a VM-centric approach;safe and timely dynamics updates for multi-threaded programs;CEAL: a C-based language for self-adjusting computation;PetaBricks: a language and compiler for algorithmic choice;staged information flow for JavaScript;laminar: practical fine-grained decentralized information flow control;Merlin: specification inference for explicit information flow problems;TAJ: effective taint analysis of web applications;lightweight annotations for controlling sharing in concurrent data structures;a randomized dynamic program analysis technique for detecting real deadlocks;FastTrack: efficient and precise dynamic race detection;LiteRace: effective sampling for lightweight data-race detection;progress guarantee for parallel programs via bounded lock-freedom;stretching transactional memory;and parallelizing sequential applications on commodity hardware using a low-cost software transactional memory.

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Disjointness Domains for Fine-Grained Aliasing

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acm sigplan NOTICES 2015年第10期50卷 898-916页

作者： Brandauer, Stephan Clarke, Dave Wrigstad, Tobias Uppsala Univ Uppsala Sweden

Aliasing is crucial for supporting useful implementation patterns, but it makes reasoning about programs difficult. To deal with this problem, numerous type-based aliasing control mechanisms have been proposed, expressing properties such as uniqueness. Uniqueness, however, is black-and-white: either a reference is unique or it can be arbitrarily aliased;and global: excluding aliases throughout the entire system, making code brittle to changing requirements. Disjointness domains, a new approach to alias control, address this problem by enabling more graduations between uniqueness and arbitrary reference sharing. They allow expressing aliasing constraints local to a certain set of variables (either stack variables or fields) for instance that no aliasing occurs between variables within some set of variables but between such sets or the opposite, that aliasing occurs within that set but not between different sets. A hierarchy of disjointness domains controls the flow of references through a program, helping the programmer reason about disjointness and enforce local alias invariants. The resulting system supports fine-grained control of aliasing between both variables and objects, making aliasing explicit to programmers, compilers, and tooling. This paper presents a formal account of disjointness domains along with examples. Disjointness domains provide novel means of expressing may-alias kinds of constraints, which may prove useful in compiler optimisation and verification.

关键词： design Theory Aliasing mutable state type systems uniqueness linear types

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