ASSIST (A Software development System based upon Integrated Skeleton Technology) is a programming environment oriented to the development of parallel and distributed high-performance applications according to a unified approach. The language and implementation features of ASSIST are a result of our long-term research in parallel programming models and tools. ASSIST is evolving towards programming environments for high-performance complex enabling platforms, especially Grids. In this paper, we show how ASSIST can act as a valid research vehicle to study, experiment and realize Grid-aware programming environments for high-performance applications. Special emphasis is put on the innovative methodologies, strategies and tools for dynamically adaptive applications, that represent the necessary step for the success of Grid platforms. First we discuss the conceptual framework for Grid-aware programming environments, based upon structured parallel programming and components technology, anticipating how ASSIST possesses the essential features required by

Abstract This paper presents the main ideas of the high-performance component-based Grid programming environment of the Grid.it project. High-performance components are characterized by a programming model that integrates the concepts of structured parallelism, component interaction, compositionality, and adaptivity. We show that ASSIST, the prototype of parallel programming environment currently under development at our group, is a suitable basis to capture all the desired features of the component model in a flexible and efficient manner. For the sake of interoperability, ASSIST modules or programs are automatically encapsulated in standard frameworks; currently, we are experimenting Web Services and the CORBA Component Model. Grid applications, built as compositions of ASSIST components and possibly other existing (legacy) components, are supported by an innovative Grid Abstract Machine, that includes essential abstractions of standard middleware services and a hierarchical Application Manager (AM). AM supports static allocation and dynamic reallocation of adaptive applications according to a performance contract, a reconfiguration strategy, and a performance model.

This paper presents JaSkel, a skeleton-based framework to develop parallel and grid applications. The framework provides a set of Java abstract classes as a skeleton catalogue, which implements recurring parallel interaction paradigms. This approach aims to improve code efficiency and portability. It also helps to structure scalable applications through the refinement and composition of skeletons. Evaluation results show that using the provided skeletons do contribute to improve both application development time and execution performance. 1.

Abstract. Skeletons are common patterns of parallelism like, e.g., farm, pipeline that can be abstracted and offered to the application programmer as programming primitives. We describe the use and implementation of skeletons in a distributed grid environment, with the Java-based system Lithium as our reference implementation. Our main contribution are optimization techniques based on an asynchronous, optimized RMI interaction mechanism, which we integrated into the macro data flow (MDF) implementation technology of Lithium. We report initial experimental results that demonstrate the achieved improvements through the proposed optimizations on a simple grid testbed. 1

In this work we present a schema of an operational semantics suitable for skeleton-based parallel languages that support both task and data parallelism. The semantics describes both functional and parallel behavior of the skeletal language in a uniform way by means of a labeled transition system. We use Lithium language (namely a Java skeleton framework) as the test-bed language to describe the methodology. The proposed schema can also be used to deal with skeletons with state.

In this paper, we discuss the benefits of using aspect-oriented programming to develop parallel applications. We use aspects to separate parallelisation concerns into three categories: partition, concurrency and distribution. The achieved modularisation enables us to assemble a variety of platform specific parallel applications, by composing combinations of (reusable) aspect modules into domain-specific core functionality. The approach makes it feasible to develop parallel applications of a higher complexity than that achieved with traditional concurrent object oriented languages.

We discuss the lack of expressivity in some skeleton-based parallel programming frameworks. The problem is further exacerbated when approaching irregular problems and dealing with dynamic data structures. Shared memory programming has been ar- gued to have substantial ease of programming advantages for this class of problems. We present eskimo library which represents an attempt to merge the two programming models by introducing skeletons in a shared memory framework.

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We discuss the lack of expressivity in some skeleton-based parallel programming frameworks. The problem is further exacerbated when approaching irregular problems and dealing with dynamic data structures. Shared memory programming has been argued to have substantial ease of programming advantages for this class of problems. We present the eskimo library which represents an attempt to merge the two programming models by introducing skeletons in a shared memory framework.

Abstract. Programming models based on algorithmic skeletons promise to raise the level of abstraction perceived by programmers when implementing parallel applications, while guaranteeing good performance figures. At the same time, however, they restrict the freedom of programmers to implement arbitrary parallelism exploitation patterns. In fact, efficiency is achieved by restricting the parallelism exploitation patterns provided to the programmer to the useful ones for which efficient implementations, as well as useful and efficient compositions, are known. In this work we introduce muskel, a full Java library targeting workstation clusters, networks and grids and providing the programmers with a skeleton based parallel programming environment. muskel is implemented exploiting (macro) data flow technology, rather than the more usual skeleton technology relying on the use of implementation templates. Using data flow, muskel easily and efficiently implements both classical, predefined skeletons, and user-defined parallelism exploitation patterns. This provides a means to overcome some of the problems that Cole identified in his skeleton “manifesto ” as the issues impairing skeleton success in the parallel programming arena. We discuss fully how userdefined skeletons are supported by exploiting a data flow implementation, experimental results and we also discuss extensions supporting the further characterization of skeletons with non-functional properties, such as security, through the use of Aspect Oriented Programming and annotations.