In the design phase of software development, the designer must make many fundamental design decisions concerning the architecture of the system. Incorrect decisions are relatively easy and inexpensive to fix if caught during the design process, but the difficulty and cost rise significantly if problems are not found until after coding begins. Unfortunately, it is not always possible to find incorrect design decisions during the design phase. To reduce the cost of expensive corrections, it would be useful to have the ability to defer some design decisions as long as possible, even into the coding stage. Failing that, tool support for automating design changes would give more freedom to revisit and change these decisions when needed. This article shows how a design-pattern-based programming system based on generative design patterns can support the deferral of design decisions where possible, and automate changes where necessary. A generative design pattern is a parameterized pattern form that is capable of generating code for different versions of the underlying design pattern. We demonstrate these ideas in the context of a parallel application written with the CO 2 P 3 S pattern-based parallel programming system. We show that CO 2 P 3 S can defer the choice of execution architecture (shared-memory or distributed-memory), and can automate several changes to the application structure that would normally be daunting to tackle late in the development cycle. Although we have done this work with a pattern-based parallel programming system, it can be generalized to other domains.

Java RMI extends Java with distributed objects whose methods can be called from remote clients. This abstraction is supported using statically-generated proxy objects on the client to hide network communication. One limitation of Java RMI is that these proxies can only forward method calls from client to server. Many applications can benefit from smart proxies that shift some application responsibilities to the client. Normally, developers must manually implement such proxies. This paper describes an aspect-oriented approach to creating smart proxies. This approach allows a server to extend an existing proxy with new capabilities at runtime. This approach is demonstrated with two examples.

Abstract Babylon is a collection of tools and services that provide a 100% Java‐compatible environment for developing, running and managing parallel, distributed and mobile Java applications. It incorporates features such as object migration, asynchronous method invocation, and remote class loading, while providing an easy‐to‐use interface. Additionally, Babylon enables Java applications to seamlessly create and interact with remote objects, while protecting those objects from other applications by implementing access restrictions and separate namespaces. The implementation of Babylon centers around dynamic proxies, a feature first available in Java 1.3, that allow proxy objects to be created at runtime. Dynamic proxies play a key role in achieving the goals of Babylon. The potential cluster computing benefits of the system are demonstrated with experimental results, which show that sequential Java applications can achieve significant performance benefits from using Babylon to parallelize their work across a cluster of workstations. Copyright © 2008 John Wiley & Sons, Ltd.

Concurrent programs are difficult to debug and verify because of the nondeterministic nature of concurrent executions. A particular concurrency-related bug may only show up under certain rarely-executed thread interleavings. Therefore, commonly used debugging methodologies, such as inserting print statements, are no longer sufficient for uncovering concurrency-related bugs. However, many existing bug detection methods, such as dynamic analysis and model checking, have a very high computational cost. In this paper, we introduce a new technique for uncovering concurrency-related bugs from multithreaded Java programs. Our technique uncovers concurrency-related bugs by generating and testing read-write assignment sequences, referred to as value schedules, of a multithreaded Java program. Our value-schedule-based technique distinguishes itself in its ability to avoid exploring superfluous program state space caused by speculative permutation on transitions. Therefore, our technique can achieve a higher degree of POR (Partial Order Reduction) than existing methods. We demonstrate our technique using some programs, with an implementation built using an explicit state model checker called JPF

Babylon v2.0 is a collection of tools and services that provide a 100% Java compatible environment for developing, running and managing parallel, distributed and mobile Java applications. It incorporates features like object migration, asynchronous method invocation and remote class loading while providing an easy-to-use interface. Additionally, Babylon v2.0 enables Java applications to seamlessly create and interact with remote objects while protecting those objects from other applications by implementing access restrictions and separate name spaces. This paper describes the most important programming features of the Babylon v2.0 system, using a heat diffusion example to show how they are used in practice. The potential cluster computing benefits of the system are demonstrated with experimental results which show that sequential Java applications can achieve significant performance benefits from using Babylon v2.0 to parallelize their work across a cluster of workstations

Babylon v2.0 is a collection of tools and services that provide a 100% Java compatible environment for developing, running and managing parallel, distributed and mobile Java applications. It incorporates features like object migration, asynchronous method invocation and remote class loading while providing an easy-to-use interface. The implementation of Babylon v2.0 exploits dynamic proxies, a feature added to Java 1.3 that allows runtime creation of proxy objects. This paper shows how Babylon v2.0 exploits dynamic proxies to implement several key features without the need for special language or virtual machine extensions, preprocessors, or compilers. The resulting Babylon programs are portable across all Java virtual machines, and the development process is simplified by removing the extra steps needed to invoke external stub compilers and incorporate the generated code into an application. This simplification also allows remote objects to be created for any class that supports an interface to its methods, even if source code is not available

The pipeline is a simple and intuitive structure to speed up many problems. Novice parallel programmers are usually taught this structure early on. However, expert parallel programmers typically eschew using the pipeline in coarse-grained applications because it has three serious problems that make it difficult to implement efficiently. First, processors are idle when the pipeline is not full. Second, load balancing is crucial to obtaining good speedup. Third, it is difficult to incrementally incorporate more processors into an existing pipeline. Instead, experts recast the problem as a master/slave structure which does not suffer from these problems. This paper details a transformation that allows programs written in a pipeline style to execute using the master/slave structure. Parallel programmers can benefit from both the intuitive simplicity of the pipeline and the efficient execution of a master/slave structure. This is demonstrated by performance results from two applications.

A design pattern is a mechanism for encapsulating the knowledge of experienced designers into a re-usable artifact. Parallel design patterns reflect commonly occurring parallel communication and synchronization structures. Our tools, CO2P3S (Correct Object-Oriented Pattern-based Parallel Programming System) and MetaCO2P3S, use generative design patterns. A programmer selects the parallel design patterns that are appropriate for an application, and then adapts the patterns for that specific application by selecting from a small set of code-configuration options. CO2P3S then generates a custom framework for the application that includes all of the structural code necessary for the application to run in parallel. The programmer is only required to write simple code that launches the application and to fill in some application-specific sequential hook routines. We use generative design patterns to take an application specification (parallel design patterns + sequential user code) and use it to generate parallel application code that achieves good performance in shared memory and distributed memory environments. Although our implementations are for Java, the approach we describe is tool and language independent. This paper describes generalizing CO2P3S to generate distributed-memory parallel solutions.

The advantages of pattern-based programming have been well-documented in the sequential programming literature. However patterns have yet to make their way into mainstream parallel computing, even though several research tools support them. There are two critical shortcomings of pattern (or template) based systems for parallel programming: lack of extensibility and performance. This paper describes our approach for addressing these problems in the CO/sub 2/P/sub 3/S parallel programming system. CO/sub 2/P/sub 3/S supports multiple levels of abstraction, allowing the user to design an application with high-level patterns, but move to lower levels of abstraction for performance tuning. Patterns are implemented as parameterized templates, allowing the user the ability to customize the pattern to meet their needs. CO/sub 2/P/sub 3/S generates code that is specific to the pattern/parameter combination selected by the user. The MetaCO/sub 2/P/sub 3/S tool addresses extensibility by giving users the ability to design and add new pattern templates to CO/sub 2/P/sub 3/S. Since the pattern templates are stored in a system-independent format, they are suitable for storing in a repository to be shared throughout the user community.

A design pattern encapsulates the knowledge of object-oriented designers into re-usable artifacts. A design pattern is a descriptive device that fosters software design re-use. There are several reasons why design patterns are not used as generative constructs that support code re-use. The first reason is that design patterns describe a set of solutions to a family of related design problems and it is difficult to generate a single body of code that adequately solves each problem in the family. A second reason is that it is difficult to construct and edit generative design patterns. A third major impediment is the lack of a tool-independent representation. A common representation could lead to a shared repository to make more patterns available. We describe a new approach to generative design patterns that solves these three difficult problems. We illustrate this approach using tools called CO/sub 2/P/sub 2/S and Meta-CO/sub 2/P/sub 2/S but our approach is tool-independent.