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Computing Systems (computing + system)

Distribution by Scientific Domains

Engineering	20%

Selected Abstracts

Formation of virtual organizations in grids: a game-theoretic approach

CONCURRENCY AND COMPUTATION: PRACTICE & EXPERIENCE, Issue 14 2010
Thomas E. Carroll
Abstract Applications require the composition of resources to execute in a grid computing environment. The grid service providers (GSPs), the owners of the computational resources, must form virtual organizations (VOs) to be able to provide the composite resource. We consider grids as self-organizing systems composed of autonomous, self-interested GSPs that will organize themselves into VOs with every GSP having the objective of maximizing its profit. Using game theory, we formulate the resource composition among GSPs as a coalition formation problem and propose a framework to model and solve it. Using this framework, we propose a resource management system that supports the VO formation among GSPs in a grid computing system. Copyright © 2008 John Wiley & Sons, Ltd. [source]

Implementation, performance, and science results from a 30.7 TFLOPS IBM BladeCenter cluster

CONCURRENCY AND COMPUTATION: PRACTICE & EXPERIENCE, Issue 2 2010
Craig A. Stewart
Abstract This paper describes Indiana University's implementation, performance testing, and use of a large high performance computing system. IU's Big Red, a 20.48 TFLOPS IBM e1350 BladeCenter cluster, appeared in the 27th Top500 list as the 23rd fastest supercomputer in the world in June 2006. In spring 2007, this computer was upgraded to 30.72 TFLOPS. The e1350 BladeCenter architecture, including two internal networks accessible to users and user applications and two networks used exclusively for system management, has enabled the system to provide good scalability on many important applications while being well manageable. Implementing a system based on the JS21 Blade and PowerPC 970MP processor within the US TeraGrid presented certain challenges, given that Intel-compatible processors dominate the TeraGrid. However, the particular characteristics of the PowerPC have enabled it to be highly popular among certain application communities, particularly users of molecular dynamics and weather forecasting codes. A critical aspect of Big Red's implementation has been a focus on Science Gateways, which provide graphical interfaces to systems supporting end-to-end scientific workflows. Several Science Gateways have been implemented that access Big Red as a computational resource,some via the TeraGrid, some not affiliated with the TeraGrid. In summary, Big Red has been successfully integrated with the TeraGrid, and is used by many researchers locally at IU via grids and Science Gateways. It has been a success in terms of enabling scientific discoveries at IU and, via the TeraGrid, across the US. Copyright © 2009 John Wiley & Sons, Ltd. [source]

A static mapping heuristics to map parallel applications to heterogeneous computing systems

CONCURRENCY AND COMPUTATION: PRACTICE & EXPERIENCE, Issue 13 2005
Ranieri Baraglia
Abstract In order to minimize the execution time of a parallel application running on a heterogeneously distributed computing system, an appropriate mapping scheme is needed to allocate the application tasks to the processors. The general problem of mapping tasks to machines is a well-known NP-hard problem and several heuristics have been proposed to approximate its optimal solution. In this paper we propose a static graph-based mapping algorithm, called Heterogeneous Multi-phase Mapping (HMM), which permits suboptimal mapping of a parallel application onto a heterogeneous computing distributed system by using a local search technique together with a tabu search meta-heuristic. HMM allocates parallel tasks by exploiting the information embedded in the parallelism forms used to implement an application, and considering an affinity parameter, that identifies which machine in the heterogeneous computing system is most suitable to execute a task. We compare HMM with some leading techniques and with an exhaustive mapping algorithm. We also give an example of mapping of two real applications using HMM. Experimental results show that HMM performs well demonstrating the applicability of our approach. Copyright © 2005 John Wiley & Sons, Ltd. [source]

Object-oriented distributed computing based on remote class reference

CONCURRENCY AND COMPUTATION: PRACTICE & EXPERIENCE, Issue 1 2003
Yan Huang
Abstract Java RMI, Jini and CORBA provide effective mechanisms for implementing a distributed computing system. Recently many numeral libraries have been developed that take advantage of Java as an object-oriented and portable language. The widely-used client-server method limits the extent to which the benefits of the object-oriented approach can be exploited because of the difficulties arising when a remote object is the argument or return value of a remote or local method. In this paper this problem is solved by introducing a data object that stores the data structure of the remote object and related access methods. By using this data object, the client can easily instantiate a remote object, and use it as the argument or return value of either a local or remote method. Copyright © 2003 John Wiley & Sons, Ltd. [source]

A heterogeneous computing system for data mining workflows in multi-agent environments

EXPERT SYSTEMS, Issue 5 2006
Ping Luo
Abstract: The computing-intensive data mining (DM) process calls for the support of a heterogeneous computing system, which consists of multiple computers with different configurations connected by a high-speed large-area network for increased computational power and resources. The DM process can be described as a multi-phase pipeline process, and in each phase there could be many optional methods. This makes the workflow for DM very complex and it can be modeled only by a directed acyclic graph (DAG). A heterogeneous computing system needs an effective and efficient scheduling framework, which orchestrates all the computing hardware to perform multiple competitive DM workflows. Motivated by the need for a practical solution of the scheduling problem for the DM workflow, this paper proposes a dynamic DAG scheduling algorithm according to the characteristics of an execution time estimation model for DM jobs. Based on an approximate estimation of job execution time, this algorithm first maps DM jobs to machines in a decentralized and diligent (defined in this paper) manner. Then the performance of this initial mapping can be improved through job migrations when necessary. The scheduling heuristic used considers the factors of both the minimal completion time criterion and the critical path in a DAG. We implement this system in an established multi-agent system environment, in which the reuse of existing DM algorithms is achieved by encapsulating them into agents. The system evaluation and its usage in oil well logging analysis are also discussed. [source]

Clinical prediction rules for bacteremia and in-hospital death based on clinical data at the time of blood withdrawal for culture: an evaluation of their development and use

JOURNAL OF EVALUATION IN CLINICAL PRACTICE, Issue 6 2006
Tsukasa Nakamura MD (Research Fellow)
Abstract Rationale, aims and objectives, To develop clinical prediction rules for true bacteremia, blood culture positive for gram-negative rods, and in-hospital death using the data at the time of blood withdrawal for culture. Methods, Data on all hospitalized adults who underwent blood cultures at a tertiary care hospital in Japan were collected from an integrated medical computing system. Logistic regression was used for developing prediction rules followed by the jackknife cross validation. Results, Among 739 patients, 144 (19.5%) developed true bacteremia, 66 (8.9) were positive for gram-negative rods, and 203 (27.5%) died during hospitalization. Prediction rule based on the data at the time of blood withdrawal for culture stratified them into five groups with probabilities of true bacteremia 6.5, 9.6, 21.9, 30.1, and 59.6%. For blood culture positive for gram-negative rods, the probabilities were 0.6, 4.7, 8.6, and 31.7%, and for in-hospital death, those were 6.7, 15.5, 26.0, 35.5, and 56.1%. The area of receiver operating characteristic for true bacteremia, blood culture positive for gram-negative rods, and in-hospital death were 0.73, 0.64, and 0.64, respectively, in original cohort and 0.72, 0.64, and 0.64 in validation respectively. Conclusions, The clinical prediction rules are helpful for improved clinical decision making for bacteremia patients. [source]

Reliability in grid computing systems,

CONCURRENCY AND COMPUTATION: PRACTICE & EXPERIENCE, Issue 8 2009
Christopher Dabrowski
Abstract In recent years, grid technology has emerged as an important tool for solving compute-intensive problems within the scientific community and in industry. To further the development and adoption of this technology, researchers and practitioners from different disciplines have collaborated to produce standard specifications for implementing large-scale, interoperable grid systems. The focus of this activity has been the Open Grid Forum, but other standards development organizations have also produced specifications that are used in grid systems. To date, these specifications have provided the basis for a growing number of operational grid systems used in scientific and industrial applications. However, if the growth of grid technology is to continue, it will be important that grid systems also provide high reliability. In particular, it will be critical to ensure that grid systems are reliable as they continue to grow in scale, exhibit greater dynamism, and become more heterogeneous in composition. Ensuring grid system reliability in turn requires that the specifications used to build these systems fully support reliable grid services. This study surveys work on grid reliability that has been done in recent years and reviews progress made toward achieving these goals. The survey identifies important issues and problems that researchers are working to overcome in order to develop reliability methods for large-scale, heterogeneous, dynamic environments. The survey also illuminates reliability issues relating to standard specifications used in grid systems, identifying existing specifications that may need to be evolved and areas where new specifications are needed to better support the reliability. Published in 2009 by John Wiley & Sons, Ltd. [source]

APEX-Map: a parameterized scalable memory access probe for high-performance computing systems,

CONCURRENCY AND COMPUTATION: PRACTICE & EXPERIENCE, Issue 17 2007
Erich Strohmaier
Abstract The memory wall between the peak performance of microprocessors and their memory performance has become the prominent performance bottleneck for many scientific application codes. New benchmarks measuring data access speeds locally and globally in a variety of different ways are needed to explore the ever increasing diversity of architectures for high-performance computing. In this paper, we introduce a novel benchmark, APEX-Map, which focuses on global data movement and measures how fast global data can be fed into computational units. APEX-Map is a parameterized, synthetic performance probe and integrates concepts for temporal and spatial locality into its design. Our first parallel implementation in MPI and various results obtained with it are discussed in detail. By measuring the APEX-Map performance with parameter sweeps for a whole range of temporal and spatial localities performance surfaces can be generated. These surfaces are ideally suited to study the characteristics of the computational platforms and are useful for performance comparison. Results on a global-memory vector platform and distributed-memory superscalar platforms clearly reflect the design differences between these different architectures. Published in 2007 by John Wiley & Sons, Ltd. [source]

Distributed loop-scheduling schemes for heterogeneous computer systems

CONCURRENCY AND COMPUTATION: PRACTICE & EXPERIENCE, Issue 7 2006
Anthony T. Chronopoulos
Abstract Distributed computing systems are a viable and less expensive alternative to parallel computers. However, a serious difficulty in concurrent programming of a distributed system is how to deal with scheduling and load balancing of such a system which may consist of heterogeneous computers. Some distributed scheduling schemes suitable for parallel loops with independent iterations on heterogeneous computer clusters have been designed in the past. In this work we study self-scheduling schemes for parallel loops with independent iterations which have been applied to multiprocessor systems in the past. We extend one important scheme of this type to a distributed version suitable for heterogeneous distributed systems. We implement our new scheme on a network of computers and make performance comparisons with other existing schemes. Copyright © 2005 John Wiley & Sons, Ltd. [source]

A static mapping heuristics to map parallel applications to heterogeneous computing systems

A performance study of job management systems

CONCURRENCY AND COMPUTATION: PRACTICE & EXPERIENCE, Issue 13 2004
Tarek El-Ghazawi
Abstract Job Management Systems (JMSs) efficiently schedule and monitor jobs in parallel and distributed computing environments. Therefore, they are critical for improving the utilization of expensive resources in high-performance computing systems and centers, and an important component of Grid software infrastructure. With many JMSs available commercially and in the public domain, it is difficult to choose an optimum JMS for a given computing environment. In this paper, we present the results of the first empirical study of JMSs reported in the literature. Four commonly used systems, LSF, PBS Pro, Sun Grid Engine/CODINE, and Condor were considered. The study has revealed important strengths and weaknesses of these JMSs under different operational conditions. For example, LSF was shown to exhibit excellent throughput for a wide range of job types and submission rates. Alternatively, CODINE appeared to outperform other systems in terms of the average turn-around time for small jobs, and PBS appeared to excel in terms of turn-around time for relatively larger jobs. Copyright © 2004 John Wiley & Sons, Ltd. [source]

Supporting Bulk Synchronous Parallelism with a high-bandwidth optical interconnect

CONCURRENCY AND COMPUTATION: PRACTICE & EXPERIENCE, Issue 13 2004
I. Gourlay
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. [source]

Telerobotic systems design based on real-time CORBA

JOURNAL OF FIELD ROBOTICS (FORMERLY JOURNAL OF ROBOTIC SYSTEMS), Issue 4 2005
Michele Amoretti
A new class of telerobotic applications is making its way into research laboratories, fine arts or science museums, and industrial installations. Virtual laboratories and remote equipment maintenance are examples of these applications, which are built exploiting distributed computing systems and Internet technologies. Distributed computing technologies provide several advantages to telerobotic applications, such as dynamic and multiuser access to remote resources and arbitrary user locations. Nonetheless, building these applications remains a substantial endeavor, especially when performance requirements must be met. The aim of this paper is to investigate how mainstream and advanced features of the CORBA object-oriented middleware can be put to work to meet the requirements of novel telerobotic applications. We show that Real-Time CORBA extensions and asynchronous method invocation of CORBA services can be relied upon to meet performance and functional requirements, thereby enabling teleoperation on local area networks. Furthermore, CORBA services for concurrency control and large-scale data distribution enable geographic-scale access for robot teleprogramming. Limitations in the currently available implementations of the CORBA standard are also discussed, along with their implications. The effectiveness and suitability for telerobotic applications of several CORBA mechanisms are tested first individually and then by means of a software framework exploiting CORBA services and ensuring component-based development, software reuse, low development cost, fully portable real-time and communication support. A comprehensive telerobotic application built based on the framework is described in the paper and evaluated on both local and wide area networks. The application includes a robot manipulator and several sensory subsystems under concurrent access by multiple competing or collaborating operators, one of which is equipped with a multimodal user interface acting as the master device. © 2005 Wiley Periodicals, Inc. [source]

Parallel Newton two-stage methods based on ILU factorizations for nonlinear systems

NUMERICAL LINEAR ALGEBRA WITH APPLICATIONS, Issue 7 2006
J. Arnal
Abstract Parallel iterative algorithms based on the Newton method and on two of its variants, the Shamanskii method and the Chord method, for solving nonlinear systems are proposed. These algorithms are based on two-stage multisplitting methods where incomplete LU factorizations are considered as a mean of constructing the inner splittings. Convergence properties of these parallel methods are studied for H -matrices. Computational results of these methods on two parallel computing systems are discussed. The reported experiments show the effectiveness of these methods. Copyright © 2006 John Wiley & Sons, Ltd. [source]