Summary Testing is a key activity to assure the quality of concurrent applications. In recent years, a variety of different mechanisms have been proposed to test concurrent software. However, a persistent problem is the high testing cost because of the large number of different synchronization sequences that must be tested. When structural testing criteria are adopted, a large number of infeasible synchronization sequences is generated, increasing the testing cost. Although the use of reachability testing reduces the number of infeasible combination (because only feasible synchronization sequences are generated), many synchronization combinations are also generated, and this again results in a testing cost with exponential behavior. This paper presents a new composite approach that uses reachability testing to guide the selection of the synchronization sequences tests according to a specific structural testing criterion. This new composite approach is empirically evaluated in the context of message‐passing concurrent programs developed with MPI. The experimental study evaluates both the cost and effectiveness of proposed composite approach in comparison with traditional reachability testing and structural testing. The results confirm that the use of the new composite approach has advantages for testing of concurrent applications. Copyright © 2015 John Wiley & Sons, Ltd.

SUMMARY Developing high‐quality, error‐free message‐passing concurrent programs is not trivial. Although a number of different primitives with associated semantics are available to assist such development, they often increase the complexity of the testing process. In this paper, we extend our previous test model for message‐passing programs and present new structural testing criteria, taking into account additional features used in this paradigm, such as collective communication, non‐blocking sends, distinct semantics for non‐blocking receives, and persistent operations. Our new model also recognizes that sender primitives cannot always be matched with every receive primitive. This improvement allows us to remove statically a significant number of infeasible synchronization edges that would otherwise have to be analyzed later by the tester. In this paper, the test model is presented using the Message‐Passing Interface standard; however, our new model has been designed to be flexible, and it can be configured to support a range of different message‐passing environments or languages. We have carried out case studies showing the applicability of the new test model to represent message‐passing programs and also to reveal errors, mainly those errors related to inter‐process communication. In addition to increasing the number of features supported by the test model, we have also reduced the overall cost of testing significantly. Our case studies suggest that the number of synchronization edges can be reduced by up to 93%, mainly by eliminating infeasible edges between unmatchable communication primitives. The main contribution of the paper is to present a more flexible test model that provides improved coverage for message‐passing programs and at the same time reduces the cost of testing significantly. Copyright © 2012 John Wiley & Sons, Ltd.

The myExperiment social website for sharing scientific workflows, designed according to Web 2.0 principles, has grown to be the largest public repository of its kind. It is distinctive for its focus on sharing methods, its researcher-centric design and its facility to aggregate content into sharable `research objects'. This evolution of myExperiment has occurred hand in hand with its users. myExperiment now supports Linked Data as a step toward our vision of the future research environment, which we categorise here as 3rd generation e-Research.

Abstract In this work we address the management of very large data sets, which need to be stored and processed across many computing sites. The motivation for our work is the ATLAS experiment for the Large Hadron Collider (LHC), where the authors have been involved in the development of the data management middleware. This middleware, called DQ2, has been used for the last several years by the ATLAS experiment for shipping petabytes of data to research centres and universities worldwide. We describe our experience in developing and deploying DQ2 on the Worldwide LHC computing Grid, a production Grid infrastructure formed of hundreds of computing sites. From this operational experience, we have identified an important degree of uncertainty that underlies the behaviour of large Grid infrastructures. This uncertainty is subjected to a detailed analysis, leading us to present novel modelling and simulation techniques for Data Grids. In addition, we discuss what we perceive as practical limits to the development of data distribution algorithms for Data Grids given the underlying infrastructure uncertainty, and propose future research directions. Copyright © 2009 John Wiley & Sons, Ltd.

The Comb e Chem e-Science project has demonstrated the advantages of using Semantic Web technology , in particular RDF and the associated triplestores, to describe and link diverse and complex chemical information, covering the whole process of the generation of chemical knowledge from inception in the synthetic chemistry laboratory, through analysis of the materials made which generates physical measurements, computations based on this data to develop interpretations, and the subsequent dissemination of the knowledge gained. The RDF descriptions employed allow for a uniform description of chemical data in a wide variety of forms including multimedia, and of the chemical processes both in the laboratory and in model building. The project successfully adopted a strategy of capturing semantic annotations ‘at source’ and establishing schema and ontologies based closely on current operational practice in order to facilitate implementation and adoption. We illustrate this in the contexts of the synthetic organic chemistry laboratory with chemists at the bench, computational chemistry for modelling data , and the linking of chemical publications to the underlying results and data to provide the appropriate provenance. The resulting ‘Semantic Data Grid’ comprises tens of millions of RDF triples across multiple stores representing complex chains of derived data with associated provenance.

Recent work by the `CombeChem' project together with the UK National Crystallography Service (NCS) has integrated the NCS into an e-Science environment. The existing high-throughput crystallography facility is enhanced by on-line feedback with the ability to monitor and steer diffraction experiments remotely. Security mechanisms are used to determine authorisation attributes and hence to allow user interaction at appropriate stages, together with access of a database recording the status of the submitted samples. The user can monitor the position of their samples, be alerted to all stages from submission to experiment and then analysis, visualise raw data as it is generated, be involved in the key decision-making during the parameterisation and initialization of the experiment and then track the data collection to ensure its successful completion. Results data are staged to a secure area and made available for download (either the raw diffraction data or a refined structure generated by NCS staff)

The GRIA project set out to make the grid usable by industry. The GRIA middleware is based on Web services, and designed to meet the needs of industry for security and business-to-business (B2B) service procurement and operation. It provides well-defined B2B models for accounting and QoS agreement, and proxy-free delegation to support account management and service federation. The GRIA v3 software is now being used by industry. By taking a business-oriented approach independent of the evolving Open Grid Services Architecture proposals from the Global Grid Forum, GRIA has demonstrated the need for a wider understanding of virtual organizations (VOs). Traditional academic VOs are persistent, resourceful and have logically centralized, membership-oriented management structures. In contrast, the GRIA experience has been that business VOs are likely to be project-focused and have distributed process-oriented management structures

Generalized cylinders provide a compact representation for modeling many components of natural objects as well as a great variety of human-made industrial parts. This paper presents a new approach to modeling generalized cylinders based on cross-sectional curves defined using Fourier descriptors. This modeling is based on contour interpolation and is implemented using a subdivision technique. The definition of generalized cylinders uses a three-dimensional trajectory which provides an adequate control for the smoothness of bend with a small number of parameters and includes the orientation of each cross-section (i.e, the local coordinate system) in the interpolation framework. Fourier representations of cross-sectional curves are obtained from contours in digital images, and corresponding points are identified by considering angular and arc-length parametrizations. Changes in cross-section shape through the trajectory are performed using Fourier morphing. The technique proposed provides a comprehensive definition that allows the modeling of a wide variety of shapes, while maintaining a compact characterization to facilitate the description of shapes and displays.

Performance is a critical issue in current massively parallel processors. However, delivery of adequate performance is not automatic and performance evaluation tools are required in order to help the programmer to understand the behaviour of a parallel program. In recent years, a wide variety of tools have been developed for this purpose, including tools for monitoring and evaluating performance and viaualization tools. However, these tools do not provide an abstract representation of performance. Massively parallel processors can generate a huge amount of performance data, and sophisticated methods for representing and displaying these data (e.g. visual and aural) are required. Performance views are not scalable in general and do not represent an abstraction of the performance data. The do-loop-surface display is proposed as an abstract representation of the performance of a particular do-loop in a program. It has been used to improve the performance of a matrix multiply parallel algorithm as well as to understand the behaviour of the following applications: matrix transposition (TRANS1) and fast fourier transform (FFT1) from the Genesis benchmarks, and the kernel of a fluid dynamics package (FIRE). These experiments were performed on a CM-5, a Meiko CS-1 and a PARSYS Supernode. The examples demonstrate that the do-loop-surface display is a useful way to represent performance. It is implemented using AVS (application visualization system), a standard data visualization package.

A novel method that provides extremely fast Input/Output (I/O) data transfer to a RISC-like graphics engine is presented. This method employs a combined two-port / two-access and a three-port / three-access register file used for concurrent processing and I/O data transfer. The three-port cell employed is only 25 % larger than the two-port cell, offering considerable advantages over alternative approaches, such as FIFOs or register banks.

Abstract This paper discusses novel dynamic‐load‐balancing and user‐allocation mechanisms for an advanced session‐based file‐store architecture to improve overall system performance. Such an architecture comprises several LAN‐based file servers working together, implementing a global and distributed file‐store for a loosely coupled distributed computing system. The load‐balancing and user‐allocation algorithms are responsibilities of a high‐level co‐ordinator server, which may be either centralized or distributed. The mechanism discussed considers three basic parameters in order to optimize the global performance: the individual file‐server performance, the cost of connection between user workstations and file servers and the cost of accessing different file servers. The paper presents the algorithms developed, together with a brief description of the file‐store architecture and associated environment. Results obtained from a simulation study and practical aspects are also presented and discussed.

A novel algorithm is described to perform in-fill of wire-frame polygons, typically for application in visual systems for flight simulation. Post-processing is performed on an image formed in a conventional raster-scan framestore using edge-detection in scan-line order. A prototype real-time implementation of this algorithm is operational and is also presented.