Parallel programming on a high‐performance application‐runtime

High‐performance application development remains challenging, particularly for scientists making the transition to a heterogeneous grid environment. In general areas of computing, virtual environments such as Java and .Net have proved to be successful in fostering application development, allowing users to target and compile to a single environment, rather than a range of platforms, instruction sets and libraries. However, existing runtime environments are focused on business and desktop computing and they do not support the necessary high‐performance computing (HPC) abstractions required by e‐Scientists. Our work is focused on developing an application‐runtime that can support these services natively. The result is a new approach to the development of an application‐runtime for HPC: the Motor system has been developed by integrating a high‐performance communication library directly within a virtual machine. The Motor message passing library is integrated alongside and in cooperation with other runtime libraries and services while retaining a strong message passing performance. As a result, the application developer is provided with a common environment for HPC application development. This environment supports both procedural languages, such as C, and modern object‐oriented languages, such as C#. This paper describes the unique Motor architecture, presents its implementation and demonstrates its performance and use. Copyright © 2008 John Wiley & Sons, Ltd.     

Debugging mixed‐environment programs with Blink

Programmers build large‐scale systems with multiple languages to leverage legacy code and languages best suited to their problems. For instance, the same program may use Java for ease of programming and C to interface with the operating system. These programs pose significant debugging challenges, because programmers need to understand and control code across languages, which often execute in different environments. Unfortunately, traditional multilingual debuggers require a single execution environment. This paper presents a novel composition approach to building portable mixed‐environment debuggers, in which an intermediate agent interposes on language transitions, controlling and reusing single‐environment debuggers. We implement debugger composition in Blink, a debugger for Java, C, and the Jeannie programming language. We show that Blink is (i) simple: it requires modest amounts of new code; (ii) portable: it supports multiple Java virtual machines, C compilers, operating systems, and component debuggers; and (iii) powerful: composition eases debugging, while supporting new mixed‐language expression evaluation and Java native interface bug diagnostics. To demonstrate the generality of interposition, we build prototypes and demonstrate debugger language transitions with C for five of six other languages (Caml, Common Lisp, C#, Perl 5, Python, and Ruby) without modifications to their debuggers. Using real‐world case studies, we show that diagnosing language interface errors require prior single‐environment debuggers to restart execution multiple times, whereas Blink directly diagnoses them with one execution. Copyright © 2014 John Wiley & Sons, Ltd.     

Klava: a Java package for distributed and mobile applications

Highly distributed networks have now become a common infrastructure for wide‐area distributed applications whose key design principle is network awareness, namely the ability to deal with dynamic changes of the network environment. Network‐aware computing has called for new programming languages that exploit the mobility paradigm as a basic interaction mechanism. In this paper we present the architecture of KLAVA , an experimental Java package for distributed applications and code mobility. We describe how KLAVA permits code mobility by relying on Java and present a few distributed applications that exploit mobile code programmed in KLAVA . Copyright © 2002 John Wiley & Sons, Ltd.     

Design and implementation of an efficient hybrid dynamic and static typing language

Dynamic languages are suitable for developing specific applications where runtime adaptability is an important issue. On the contrary, statically typed languages commonly provide better compile‐time type error detection and more opportunities for compiler optimizations. Because both approaches offer different benefits, there exist programming languages that support hybrid dynamic and static typing. However, the existing hybrid typing languages commonly do not gather type information of dynamic references at compile time, missing opportunities for improving compile‐time error detection and runtime performance. Therefore, we propose some design principles to implement hybrid typing languages that continue gathering type information of dynamically typed references. This type information is used to perform compile‐time type checking of the dynamically typed code and improve its runtime performance. As an example, we have implemented a hybrid typing language following the proposed design principles. We have evaluated the runtime performance and memory consumption of the generated code. The average performance of the dynamic and hybrid typing code is at least 2.53× and 4.51× better than the related approaches for the same platform, consuming less memory resources. Copyright © 2014 John Wiley & Sons, Ltd.     

A hybrid class- and prototype-based object model to support language-neutral structural intercession

ContextDynamic languages have turned out to be suitable for developing specific applications where runtime adaptability is an important issue. Although .Net and Java platforms have gradually incorporated features to improve their support of dynamic languages, they do not provide intercession for every object or class. This limitation is mainly caused by the rigid class-based object model these platforms implement, in contrast to the flexible prototype-based model used by most dynamic languages.ObjectiveOur approach is to provide intercession for any object or class by defining a hybrid class- and prototype-based object model that efficiently incorporates structural intercession into the object model implemented by the widespread .Net and Java platforms.MethodIn a previous work, we developed and evaluated an extension of a shared-source implementation of the .Net platform. In this work, we define the formal semantics of the proposed reflective model, and modify the existing implementation to include the hybrid model. Finally, we assess its runtime performance and memory consumption, comparing it to existing approaches.ResultsOur platform shows a competitive runtime performance compared to 9 widespread systems. On average, it performs 73% and 61% better than the second fastest system for short- and long-running applications, respectively. Besides, it is the JIT-compiler approach that consumes less average memory. The proposed approach of including a hybrid object-model into the virtual machine involves a 444% performance improvement (and 65% less memory consumption) compared to the existing alternative of creating an extra software layer (the DLR). When none of the new features are used, our platform requires 12% more execution time and 13% more memory than the original .Net implementation.ConclusionOur proposed hybrid class- and prototype-based object model supports structural intercession for any object or class. It can be included in existing JIT-compiler class-based platforms to support common dynamic languages, providing competitive runtime performance and low memory consumption.     

基于JSON的异构Web平台的设计与实现

随着互联网覆盖领域的不断扩大以及编程语言的不断更新和迅速发展,Web平台需要兼顾越来越多的异构情况。JSON具有语言独立性和平台无关性的特点,与其他轻量级的数据交换格式相比有着显著优势,逐渐成为目前Web平台理想的数据交换格式。Java和Python作为Web开发中两种长期占据主要使用比例的编程语言,越来越多地被开发者在同一个系统中使用。目前如何通过独立数据格式将前后端以及不同的开发语言之间进行连接就成为了一个典型问题。针对这个问题,实现了一种基于JSON的异构平台。在基于Java和Python两种语言进行Web异构平台开发的基础上,以JSON数据格式作为异构平台的统一交换格式以实现前后端的数据通信,同时将JSON数据作为Java和Python的连接方式,得到了较好的效果,并通过一个实验室管理系统的核心功能作为应用示例进行了具体说明。     

Pipeline pattern in an object‐oriented,task‐parallel environment

Task parallelism is an approach to parallel programming that has recently gained traction because of its compatibility with the predominant object‐oriented languages and its low overhead compared to threading approaches. Parallel Task is an Open Source task‐parallel compiler and runtime system for object‐oriented languages, in particular Java. It is very flexible and expressive, demonstrated by the fact that it can be directly employed to implement most parallel computing patterns. The only notable exception has been the pipeline pattern where many data items are streamed through a number of processing stages. This is not surprising, as task parallelism is generally not compatible with the pipeline pattern. In this paper, we investigate how the pipeline pattern can be elegantly and efficiently implemented in a task‐parallel environment. To do so, we extend Parallel Task with the concept of implicit futures to allow creating pipelines in an intuitive and object‐oriented manner. Our experimental evaluation uses the extended Parallel Task to implement pipelines of different lengths and characteristics and compares with manual implementations. The evaluation demonstrates very good performance and scalability of the proposed task‐parallel pipeline approach. Copyright © 2014 John Wiley & Sons, Ltd.     

Dynamics modeling and culling

The tools described, permit including large numbers of complex dynamic models in a VRML world easily and efficiently while maintaining high frame rates. We describe three tools that together provide an environment for authoring cullable, dynamic, rigid-body objects in VRML and Java: a code transformation tool that exploits approximations to dynamical systems to enable culling; a runtime layer generator, which defines a simple standard interface between a VRML browser and dynamical systems described in Java; a rigid-body modeler, which allows users to interactively design the runtime layer and preview the dynamic behavior. The article describes these tools, including some example systems, and discusses the runtime performance improvements obtained. Our tools are applicable if the spatial range of the dynamic model can be bounded by a static volume, the model is closed to outside influence, the underlying equations are continuous, and the dimension (number of degrees of freedom) of the system is small. Note that while the article focuses on VRML and Java as the target environment, the underlying techniques apply to any rendering and language environment     

A Constraint-Based Robotic Soccer Team

It is a challenging task for a team of multiple fast-moving robots to cooperate with each other and to compete with another team in a dynamic, real-time environment. For a robot team to play soccer successfully, various technologies have to be incorporated including robotic architecture, multi-agent collaboration and real-time reasoning. A robot is an integrated system, with a controller embedded in its plant. A robotic system is the coupling of a robot to its environment. Robotic systems are, in general, hybrid dynamic systems, consisting of continuous, discrete and event-driven components. Constraint Nets (CN) provide a semantic model for modeling hybrid dynamic systems. Controllers are embedded constraint solvers that solve constraints in real-time. A controller for our robot soccer team, UBC Dynamo98, has been modeled in CN, and implemented in Java, using the Java Beans architecture. A coach program using an evolutionary algorithm has also been designed and implemented to adjust the weights of the constraints and other parameters in the controller. The results demonstrate that the formal CN approach is a practical tool for designing and implementing controllers for robots in multi-agent real-time environments. They also demonstrate the effectiveness of applying the evolutionary algorithm to the CN-modeled controllers.     

Efficient virtual machine support of runtime structural reflection

Increasing trends towards adaptive, distributed, generative and pervasive software have made object-oriented dynamically typed languages become increasingly popular. These languages offer dynamic software evolution by means of reflection, facilitating the development of dynamic systems. Unfortunately, this dynamism commonly imposes a runtime performance penalty. In this paper, we describe how to extend a production JIT-compiler virtual machine to support runtime object-oriented structural reflection offered by many dynamic languages. Our approach improves runtime performance of dynamic languages running on statically typed virtual machines. At the same time, existing statically typed languages are still supported by the virtual machine.We have extended the .Net platform with runtime structural reflection adding prototype-based object-oriented semantics to the statically typed class-based model of .Net, supporting both kinds of programming languages. The assessment of runtime performance and memory consumption has revealed that a direct support of structural reflection in a production JIT-based virtual machine designed for statically typed languages provides a significant performance improvement for dynamically typed languages.     

Model Checking Programs

The majority of work carried out in the formal methods community throughout the last three decades has (for good reasons) been devoted to special languages designed to make it easier to experiment with mechanized formal methods such as theorem provers, proof checkers and model checkers. In this paper we will attempt to give convincing arguments for why we believe it is time for the formal methods community to shift some of its attention towards the analysis of programs written in modern programming languages. In keeping with this philosophy we have developed a verification and testing environment for Java, called Java PathFinder (JPF), which integrates model checking, program analysis and testing. Part of this work has consisted of building a new Java Virtual Machine that interprets Java bytecode. JPF uses state compression to handle big states, and partial order and symmetry reduction, slicing, abstraction, and runtime analysis techniques to reduce the state space. JPF has been applied to a real-time avionics operating system developed at Honeywell, illustrating an intricate error, and to a model of a spacecraft controller, illustrating the combination of abstraction, runtime analysis, and slicing with model checking.     

An empirical comparison of seven programming languages

Often heated, debates regarding different programming languages' effectiveness remain inconclusive because of scarce data and a lack of direct comparisons. The author addresses that challenge, comparatively analyzing 80 implementations of the phone-code program in seven different languages (C, C++, Java, Perl, Python, Rexx and Tcl). Further, for each language, the author analyzes several separate implementations by different programmers. The comparison investigates several aspects of each language, including program length, programming effort, runtime efficiency, memory consumption, and reliability. The author uses comparisons to present insight into program language performance     

Developers Shift to Dynamic Programming Languages

Software developers are always looking for ways to boost their effectiveness and productivity and perform complex jobs more quickly and easily, particularly as projects have become increasingly large and complex. Programmers want to shed unneeded complexity and outdated methodologies and move to approaches that focus on making programming simpler and faster. With this in mind, many developers are increasingly using dynamic languages such as JavaScript, Perl, Python, and Ruby. Although software experts disagree on the exact definition, a dynamic language basically enables programs that can change their code and logical structures at runtime, adding variable types, module names, classes, and functions as they are running. These languages frequently are interpreted and generally check typing at runtime     

JavAdaptor—Flexible runtime updates of Java applications

Software is changed frequently during its life cycle. New requirements come, and bugs must be fixed. To update an application, it usually must be stopped, patched, and restarted. This causes time periods of unavailability, which is always a problem for highly available applications. Even for the development of complex applications, restarts to test new program parts can be time consuming and annoying. Thus, we aim at dynamic software updates to update programs at runtime. There is a large body of research on dynamic software updates, but so far, existing approaches have shortcomings either in terms of flexibility or performance. In addition, some of them depend on specific runtime environments and dictate the program's architecture. We present JavAdaptor , the first runtime update approach based on Java that (a) offers flexible dynamic software updates, (b) is platform independent, (c) introduces only minimal performance overhead, and (d) does not dictate the program architecture. JavAdaptor combines schema changing class replacements by class renaming and caller updates with Java HotSwap using containers and proxies. It runs on top of all major standard Java virtual machines. We evaluate our approach's applicability and performance in non‐trivial case studies and compare it with existing dynamic software update approaches. Copyright © 2012 John Wiley & Sons, Ltd.     

Distributed computing using autonomous objects

Most existing distributed systems are structured as statically compiled processes communicating with each other via messages. The system's intelligence is embodied in the processes, while the messages contain simple, passive pieces of information. This is referred to as the communicating objects paradigm. In the autonomous objects paradigm, a message has its own identity and behavior. It decides at runtime where it wants to propagate and what tasks to perform there; the nodes become simply generic interpreters that enable messages to navigate and compute. In this scenario, an application's intelligence is embodied in and carried by messages as they propagate through the network. The autonomous objects paradigm is more flexible than the communicating objects paradigm because it allows developers to change the program's behavior after it has started to run. We based our system, MESSENGERS, on autonomous objects, and intended it for the composition and coordination of concurrent activities in a distributed environment. It combines powerful navigational capabilities found in other autonomous objects based systems with efficient dynamic linking mechanisms supported by some new programming languages, like Java     

Java supervenience

This paper reports on the development of a language construct designed to solve certain problems in composability at the level of object-oriented programming languages. Features were chosen to investigate how much compositional functionality could be added to core Java with as small a change as possible and in an additive manner. A fairly elegant and effective syntax on core Java resulted in reducing the clutter of the "mechanics" of composition. This construct features eliminating runtime cast and null exceptions within the construct, and the option of parametric covariant override. It does so while avoiding undesirable restrictions or new frameworks. Recently, new techniques intended to improve the composability of software components in the Java ecosystem have been vigorously pursued. Proposals take on the objectives of composition in largescale systems and enterprise applications but often implement on conventional object-oriented languages which face the same kinds of problems from the ground up. Benefitting from those experiences, the present work seeks to provide core Java-level solutions to problems that are analogous to those at the higher-levels. The supervenience construct described in this paper is based on a well-established formulation for composing a relationship over classes with some common behavioral elements, their behavioral intersection. The narrow concern of this construct is the sound composition of components across class families while eliminating certain barriers to runtime type-safety in core Java. The supervenience construct has been applied to certain classic problems and key case studies in composability and extensibility which represent fundamental issues that emerge at every level. The implementation requires no installed runtime frameworks and no changes to the JVM or type system of core Java. It is designed to deploy stand-alone or later integrate with the standard Java compiler and IDEs. The continuing research is now focusing on a more formal proof of its type-safety, applying the reference implementation to mid-scale and distributed applications.     

Adaptability mechanisms for autonomic system implementation with AAOP

This paper presents a new approach to implementing an adaptability loop in Autonomic Computing (AC) systems, which is based on adaptable aspects. The approach utilizes the concept of adaptable aspect‐oriented programming (AAOP) in which a set of AOP aspects is used to run an application in the manner specified by its adaptability strategy. We present a model execution environment based on this concept, enabling the execution of applications with applied adaptability strategies. In the AAOP‐based AC system, the application is instrumented with aspects selected by the system from a set of all available aspects (sensors, effectors, and goal aspects) in such a way that the system can monitor and manage the application. This model can be used to implement systems that are able to monitor an application and its execution environment, and perform actions such as changing the current set of non‐functional constraints in response to changes in the application or its environment. The model can be used for various types of non‐functional goals, in various programming languages, both in centralized and distributed environments. This paper describes its Java‐based implementation and non‐functional goals referring to resource management. As a consequence, the application uses resources in a way specified in its adaptability strategy. Resource consumption management logic is transparent for the application, meaning that no modifications in the application source code are needed. Copyright © 2010 John Wiley & Sons, Ltd.