This research is concerned with the design and evaluation of an Electronic Laboratory Notebook (ELN) for the simulation of chemical processes. It provides quality provenance information for scientists wishing to compare simulation runs with in vitro experimental data. The research is grounded in the EUROCHAMP-2 community. The community uses a benchmark Master Chemical Mechanism (MCM) in order to undertake their model simulations. The goal is to ensure that, for each atmospheric chamber experiment, a computational model is evaluated/developed using the MCM. This paper builds on earlier research on an ELN for this community. The main contributions are: (1) a re-engineered ELN co-developed by EUROCHAMP-2 chemists and computer scientists where the focus is to enable community scientists to capture and extract useful provenance information, (2) a novel Inline Provenance Node Navigator (IPNav) is provided which enables a modeller to navigate through the trail of the runs as a simulation is created, and (3) the results of an initial user evaluation of the ELN undertaken with two practising modellers.

This paper proposes an application of the Collaborative e-Science Architecture (CeSA) to enable e-Research in combustion research community. A major problem of the community is that data required for constructing modelling might already exist but scattered and improperly evaluated. That makes the collection of data for constructing models difficult and time-consuming. The decentralised P2P collaborative environment of the CeSA is well suited to solve this distributed problem. It opens up access to scattered data and turns them to valuable resources. Other issues of the community addressed here are the needs for computational resources, storages and interoperability amongst different data formats can also be addressed by the use of Grid environment in the CeSA.

Resource brokering is an essential component in building effective Grid systems. Existing mechanisms employ a traditional approach for resource allocation, which is likely to run into performance problems. This paper presents the development of a broker that is designed within the SNAP (Service Negotiation and Acquisition Protocol) framework and focuses on applications that require resources on demand. The broker uses a three-phase commit protocol as the traditional advance reservation facilities cannot cater to such needs due to the prior time that it requires to schedule the reservation. Experiments have been carried out on a Grid testbed, supported by mathematical modelling and simulation. The experimental results show that the inclusion of the three-phase commit protocol results in a performance enhancement in terms of the time taken from submission of user requirements until a job begins execution. The broker is a viable contender for use in future Grid resource broker implementations.

Summary form only given. Resource brokering is an essential component in building effective grid systems. Existing mechanisms employ a traditional approach for resource allocation, which is likely to run into performance problems. We present the development of a broker that is designed within the SNAP (service negotiation and acquisition protocol) framework and focuses on applications that require resources on demand. The broker uses a three-phase commit protocol, as the traditional advance reservation facilities cannot cater for such needs due to the prior time that it requires to schedule the reservation. The experimental results show that the inclusion of the three-phase commit protocol results in a performance enhancement in terms of the time taken from submission of user requirements until a job begins execution. The broker is a viable contender for use in future grid resource broker implementations.

Abstract The list of applications requiring high‐performance computing resources is constantly growing. The cost of inter‐processor communication is critical in determining the performance of massively parallel computing systems for many of these applications. This paper considers the feasibility of a commodity processor‐based system which uses a free‐space optical interconnect. A novel architecture, based on this technology, is presented. Analytical and simulation results based on an implementation of BSP (Bulk Synchronous Parallelism) are presented, indicating that a significant performance enhancement, over architectures using conventional interconnect technology, is possible. Copyright © 2004 John Wiley & Sons, Ltd.

A grid system must integrate heterogeneous resources with varying quality and availability. For example, the load on any given resource may increase during execution of a time-constrained job. This places importance on the system's ability to recognize the state of these resources. This paper presents an approach used as a basis for system adaptation in which grid jobs are maintained at runtime. A reflective technique is used to simplify the adaptation in the grid application. The design of an adaptable resource broker is described and experimentally evaluated. Reflection is incorporated into the broker to separate functional and non-functional aspects of the system and facilitate the implementation of non-functional properties such as job migration. Results indicate that this approach enhances the likelihood of timely job completion in a dynamic grid system.

In this paper we present an experimental transport protocol which employs alternative methods of startup and congestion avoidance to those commonly used in implementations of TCP. Through modelling and simulation, we demonstrate how a packet-pair probe may be used to replace traditional slow-start methods and how pro-active congestion avoidance algorithms provide smoother traffic flow with lower levels of packet loss and retransmission. We also show how a token bucket may be used to allow bounded burstiness for an Internet connection in order to facilitate an application's quality of service.

This paper presents a detailed evaluation on the acceptability of a range of synchronous and asynchronous collaborative tools provided within the Virtual Science Park (VSP) for group work in a learning environment. In this study, the VSP was used to provide a web-based 'Resource Room' adopting the familiar 'folder' metaphor for structuring and linking resources, and a number of different user interfaces for interaction and sharing information. A list of criteria is established for the evaluation. By using scenario testing and structured questionnaires, qualitative feedback was collected from 43 Masters students. The findings reinforce and add to the concerns highlighted in other studies, in particular, the importance for shared awareness, privacy, conventions for interaction and the provision of an effective multimedia environment. More attention will be needed in these areas for effective use of these groupware tools.

This paper introduces mechanisms for exploiting concurrency and synchronisation in Actel: a concurrent object based language. It focuses on issues of combining parallelism with object orientation, performance, and synchronisation. Actel offers several mechanisms such as a new mode of message passing called 'semi-reference' to achieve an efficient inter-object concurrency. Parallel functions and parallel compound statements are provided to exploit concurrency inside an object at several levels without recourse to explicit synchronisation. Implicit synchronisation is obtained through future variables.

The emergence of low latency, high throughput routers means that network locality issues no longer dominate the performance of parallel algorithms. One of the key performance issues is now the even distribution of work across the machine, as the problem size and number of processors increase. This paper describes the implementation of a highly scalable shared queue, supporting the concurrent insertion and deletion of elements. The main characteristics of the queue are that there is no fixed limit on the number of outstanding requests and the performance scales linearly with the number of processors (subject to increasing network latencies). The queue is implemented using a general-purpose computational model, called the WPRAM. The model includes a shared address space which uses weak coherency semantics. The implementation makes extensive use of pairwise synchronization and concurrent atomic operations to achieve scalable performance. The WPRAM is targeted at the class of distributed memory machines which use a scalable interconnection network.

Article Free Access Share on An optimal randomized planar convex hull algorithm with good empirical performance Authors: Martin Dyer University of Leeds, Leeds LS2 9JT, UK University of Leeds, Leeds LS2 9JT, UKView Profile , Jonathan Nash University of Leeds, Leeds LS2 9JT, UK University of Leeds, Leeds LS2 9JT, UKView Profile , Peter Dew University of Leeds, Leeds LS2 9JT, UK University of Leeds, Leeds LS2 9JT, UKView Profile Authors Info & Claims SPAA '95: Proceedings of the seventh annual ACM symposium on Parallel algorithms and architecturesJuly 1995 Pages 21–26https://doi.org/10.1145/215399.215407Published:20 July 1995Publication History 3citation191DownloadsMetricsTotal Citations3Total Downloads191Last 12 Months11Last 6 weeks7 Get Citation AlertsNew Citation Alert added!This alert has been successfully added and will be sent to:You will be notified whenever a record that you have chosen has been cited.To manage your alert preferences, click on the button below.Manage my AlertsNew Citation Alert!Please log in to your account Save to BinderSave to BinderCreate a New BinderNameCancelCreateExport CitationPublisher SiteeReaderPDF

Abstract Solid modelling using constructive solid geometry (CSG) includes many examples of stylised divide-and-conquer algorithms. We identify the sources of these recurrent patterns and describe a Geometric Evaluation Library (GEL) which captures them as higher-order functions. This library then becomes the basis of developing CSG applications quickly and concisely. GEL is currently implemented as a set of separately compiled modules in the pure functional language Hope+. We evaluate our work in terms of performance and general applicability. We also assess the benefits of the functional paradigm in this domain and the merits of programming with a set of higher-order functions.

The paper presents a new load balancing algorithm called Periodic Symmetrically-Initiated (PSI). It is symmetrically initiated and uses periodic polling of a single random node to acquire information about the system state. Its performance on a distributed system is compared to the following algorithms: Random, Sender, Receiver, and Symmetric. These algorithms have been evaluated by M. Livny (1984), where the terms Sender and Receiver are referred to as Forward and Reverse respectively. The algorithms' performance under different variants to the system model is also studied to assess the sensitivity of the PSI algorithm to changes in the system attributes. This includes the communication bandwidth, the system size, the file system structure, and the workload model. The results of the study show that the PSI algorithm outperforms the existing algorithms and is robust over a range of system attributes.>

Abstract This paper presents a novel constraint‐based 3D manipulation approach to interactive constraint‐based solid modelling. This approach employs a constraint recognition process to automatically recognise assembly relationships and geometric constraints between entities from 3D manipulation. A technique referred to as allowable motion is used to achieve accurate 3D positioning of a solid model by automatically constraining its 3D manipulation without menu interaction. A set of virtual design tools, which can be used to construct constraint‐based solid models within a virtual environment, are also supported. These tools have been implemented as functional 3D objects associated with several pre‐defined modelling functions to simulate physical tools such as a drilling tool and T‐square. They can be directly manipulated by the user, and precisely positioned relative to other solid models through the constraint‐based 3D manipulation approach. Their modelling functions can be automatically triggered, depending upon their associated constraints and the user's manipulation manner. A prototype system has been implemented to demonstrate the feasibility of these techniques for model construction and assembly operations.

Abstract Apply is a machine‐independent, low‐level image processing language for expressing local window operations. It has two main advantages: (1) it significantly reduces the programming effort, and (2) it can be mapped onto a wide range of parallel computers. In this paper we report our recent experience on implementing Apply on a Meiko Computing Surface (transputer array machine) using a farmer/gather model. The performance of the Meiko implementation on a number of edge detection algorithms including the popular Canny operator is analysed. Results suggest that the performance of Apply generated code represents peak performance and it is likely to be as efficient as hand‐written code.

PDECHEB is a FORTRAN 77 software package that semidiscretizes a wide range of time-dependent partial differential equations in one space variable. The software implements a family of spacial discretization formulas, based on piecewise Chebyshev polynomial expansions with C 0 continuity. The package has been designed to be used in conjunction with a general integrator for initial value problems to provide a powerful software tool for the solution of parabolic-elliptic PDEs with coupled differential algebraic equations. Examples are provided to illustrate the use of the package with the DASSL d.a.e integrator of Petzold [18].

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