A system integration framework for coupled multiphysics simulations

Multiphysics simulations are playing an increasingly important role in computational science and engineering for applications ranging from aircraft design to medical treatments. These simulations require integration of techniques and tools from multiple disciplines, and in turn demand new advanced technologies to integrate independently developed physics solvers effectively. In this paper, we describe some numerical, geometrical, and system software components required by such integration, with a concrete case study of detailed, three-dimensional, parallel rocket simulations involving system-level interactions among fluid, solid, and combustion, as well as subsystem-level interactions. We package these components into a software framework that provides common-refinement based methods for transferring data between potentially non-matching meshes, novel and robust face-offsetting methods for tracking Lagrangian surface meshes, as well as integrated support for parallel mesh optimization, remeshing, algebraic manipulations, performance monitoring, and high-level data management and I/O. From these general, reusable framework components we construct domain-specific building blocks to facilitate integration of parallel, multiphysics simulations from high-level specifications that are easy to read and can also be visualized graphically. These reusable building blocks are integrated with independently developed physics codes to perform various multiphysics simulations.     

Application execution management on the InteGrade opportunistic grid middleware

The InteGrade project is a multi-university effort to build a novel grid computing middleware based on the opportunistic use of resources belonging to user workstations. The InteGrade middleware currently enables the execution of sequential, bag-of-tasks, and parallel applications that follow the BSP or the MPI programming models.     

CROWN:A service grid middleware with trust management mechanism

Based on a proposed Web service-based grid architecture, a service grid middleware system called CROWN is designed in this paper. As the two kernel points of the middleware, the overlay-based distributed grid resource management mechanism is proposed, and the policy-based distributed access control mechanism with the capability of automatic negotiation of the access control policy and trust management and negotia- tion is also discussed in this paper. Experience of CROWN testbed deployment and ap- plication development shows that the middleware can support the typical scenarios such as computing-intensive applications, data-intensive applications and mass information processing applications.     

Grid Data Management: Open Problems and New Issues

Initially developed for the scientific community, Grid computing is now gaining much interest in important areas such as enterprise information systems. This makes data management critical since the techniques must scale up while addressing the autonomy, dynamicity and heterogeneity of the data sources. In this paper, we discuss the main open problems and new issues related to Grid data management. We first recall the main principles behind data management in distributed systems and the basic techniques. Then we make precise the requirements for Grid data management. Finally, we introduce the main techniques needed to address these requirements. This implies revisiting distributed database techniques in major ways, in particular, using P2P techniques. Work partially funded by ARA “Massive Data” of the French ministry of research (project Respire), the European Strep Grid4All project, the CAPES–COFECUB Daad project and the CNPq–INRIA Gridata project.     

A component-based approach to build a portable and flexible middleware for metacomputing

The huge amount of computing resources in the Internet makes it possible to build metacomputers for solving large-scale problems. Despite the great availability of software infrastructures for managing such systems, metacomputer programming is often based on models that do not appear to be suitable to run applications on wide-area, unreliable, highly-variable networks of computers. In this paper, we present a customisable, Java-based middleware which provides programmers with a portable and flexible framework to run applications over a hierarchical, virtual network architecture. The middleware is designed according to a component-based approach that enables the execution behaviour of each computing node to be customised in order to satisfy application needs. The paper shows some examples of programming model customisation and demonstrates that flexibility can be achieved without significantly compromising performance.     

Design and implementation of economics-based resource management system in ad hoc grid

The ad hoc grid is a spontaneous organization of cooperating heterogeneous nodes into a logical community without a fixed infrastructure and with only minimal administrative requirements. Resource management for ad hoc grids is challenging due to the participation of heterogeneous, dynamic, autonomous and ephemeral grid nodes. The paper proposes an ad hoc grid resource management system, the producers and consumers of ad hoc grid resource are modeled as the self-interested decision-makers described in microeconomic theory. All market participants in the ad hoc grid environment including grid resources and services can be represented as agents. We apply economic agents to build ad hoc grid resource management, where ad hoc grid resource consumers and providers can buy and sell ad hoc grid resource based on an underlying economic architecture. The main processes involved in ad hoc grid resource management are resource registration, discovery, and resource allocation. The experiments are conducted to compare ad hoc grid resource allocation algorithm with other ad hoc grid resource allocation algorithm. Simulation results show that our proposed algorithm is more efficient than compared allocation scheme.     

ATLAS grid workload on NDGF resources: Analysis,modeling, and workload generation

Evaluating new ideas for job scheduling or data transfer algorithms in large-scale grid systems is known to be notoriously challenging. Existing grid simulators expect to receive a realistic workload as an input. Such input is difficult to obtain in the absence of an in-depth study of representative grid workloads.In this work, we analyze the workload of the ATLAS experiment at CERN at the LHC, processed on the resources of Nordic Data Grid Facility. ATLAS is one of the biggest grid technology users, with extreme demands for CPU power, data volume and bandwidth. The analysis is based on the data sample with ∼1.6 million jobs, 3029 TB of data transfer, and 873 years of processor time. Our additional contributions are (a) scalable workload models that can be used to generate a synthetic workload for a given number of jobs, (b) an open-source workload generator software integrated with existing grid simulators, and (c) suggestions for grid system designers based on the insights of our analysis.     

The Climate-G Portal: The context, key features and a multi-dimensional analysis

Grid portals are web gateways aiming at concealing the underlying infrastructure through a pervasive, transparent, user-friendly, ubiquitous and seamless access to heterogeneous and geographically spread resources (i.e. storage, computational facilities, services, sensors, network and databases). The Climate-G Portal is the web gateway of the Climate-G testbed (an interdisciplinary research effort involving scientists both in Europe and US) and it is devoted to climate change research studies. The main goal of this paper is to present the Climate-G Portal providing a complete understanding of the international context, discussing its main requirements, challenges, architecture and key functionalities, and finally carrying out and presenting a multi-dimensional analysis of the Climate-G Portal, starting from a general schema proposed and discussed in this work.     

An optimization-based adaptive resource management framework for economic Grids: A switching mechanism

The application of Grid computing has been broadening day by day. An increasing number of users has led to the requirement of a job scheduling process, which can benefit them through optimizing their utility functions. On the other hand, resource providers are exploring strategies suitable for economically efficient resource allocation so that they can maximize their profit through satisfying more users. In such a scenario, economic-based resource management strategies (economic models) have been found to be compelling to satisfy both communities. However, existing research has identified that different economic models are suitable for different scenarios in Grid computing. The Grid application and resource models are typically very dynamic, making it challenging for a particular model for delivering stable performance all the time. In this work, our focus is to develop an adaptive resource management architecture capable of dealing with multiple models based on the models’ domains of strengths (DOS). Our preliminary results show promising outcomes if we consider multiple models rather than relying on a single model throughout the life cycle of a Grid.     

MIMD implementations of linear solvers for oil reservoir simulation

This paper describes the parallel solution of a class of large sparse systems of linear equations produced by an oil reservoir simulator. Specifically, we focus on the implementation of a conjugate gradient algorithm for a transputer-based machine. After discussing communication, harnesses, we present strategies for decomposing the algorithm on a transputer array, and report the results of measurements of speed-ups for some practical reservoir problems. We then address the problemsof preconditioning by first implementing distributed forms of three standard iterative algorithms, namely Jacobi, Gauss-Seidel and Successive Over-relaxation, and determining their convergence and speed-up properties. On the basis of these measurements, we suggest that a Jacobi preconditioned conjugate gradient (JPCG) algorithm appears likely to be the most cost-effective for the class of problems under considerations. Finally we implement the JPCG algorithm and present measurements in support of our claim.     

GIS模型网格计算原理及算法

GIS模型计算逐步向数据处理海量化及过程复杂化方向发展。网格计算为解决GIS应用这一难题提供了契机。GIS模型计算从运算模式上可分解为并行、串行和并行串行模式,该文在这些模式的基础上提出了实现GIS模型网格计算的原理性方法：分块加工、分步加工和立体加工方法,并以GIS和RS中的常用模型(直方图和矢量地图插值)作为算法实例,论述其并行算法实现,同时给出矢量地图数据的分块规则。该并行算法实现可作为实现其它同类算法的基础和扩展。     

网格实例与关键技术分析

Grid computing technology is developing in an impressing speed these years. This paper is going to do some detailed analysis on two of the major Grid projects, Globus and Legion, in order to find out the key technologies of Grid computing. In this paper, three key technologies will be discussed: Grid Architecture, Grid Data and Resource Services, and Grid Security Services. Different implementation of these technologies will be discussed and compared with each other, some new ideas about these technologies will be proposed as well.     

网格资源管理系统模型的研究

针对已有模型不能实现更多范围内获取所需要的资源,提出了一个改进的通用抽象体系结构模型,通过接口向网格资源管理系统发布、获取自己所需要的资源,实现用户在更大范围内获取所需要的资源.创建了该模型的原型系结构模型,通过接口向网格资源管理系统发布、获取自己所需要的资源,实现用户在更大范围内获取所需要的资源.创建了该模型的原型系统的网格,并在该网格上进行了一些算法研究.实验结果证实了该实践中的可行性和优越性.     

A near-optimal database allocation for reducing the average waiting time in the grid computing environment

In a grid computing environment, a great many users may access the same database simultaneously. To reduce the average waiting time for all users, a grid designer usually replicates the frequently accessed database among nodes based on the load balance heuristic. On the other hand, users may raise identical queries regarding an issue of interest, e.g., stock information, on a database and each of the queries will be directed to any node having a replica of that database. That is, the same answer will be determined by multiple nodes. Consequently, there exist two shortcomings of poor data sharing and duplicate calculations if the database is not replicated and allocated adequately. In this paper, we aim to minimize average waiting time and try to overcome the two shortcomings by performing database allocation over multiple nodes without any replication. The main idea behind the proposed method is to map the original problem to the Euclidean space Rⁿ and to solve the mapped problem in Rⁿ by a gradient-based optimization technique. The theoretical analyses ensure that the proposed method can converge linearly and achieve near-optimal results.     

数据并行计算：概念,模型与系统

一、引言并行计算,或者并行处理,指的是这样一种努力和相关的研究:利用多个具有计算能力的部件来共同完成一个计算工作,以获得比用一个部件来完成要快的效果。这显然是一个很自然的想法。历史地看,几乎是自从有了计算机,就有了并行处理的想法和实践。在80年代后期到90年代初期,以寻求对人类面临的若干重     

Analysis and Provision of QoS for Distributed Grid Applications

Grid computing provides the infrastructure necessary to access and use distributed resources as part of virtual organizations. When used in this way, Grid computing makes it possible for users to participate in collaborative and distributed applications such as tele-immersion, visualization, and computational simulation. Some of these applications operate in a collaborative mode, requiring data to be stored and delivered in a timely manner. This class of applications must adhere to stringent real-time constraints and Quality-of-Service (QoS) requirements. A QoS management approach is therefore required to orchestrate and guarantee the timely interaction between such applications and services. We discuss the design and a prototype implementation of a QoS system, and demonstrate how we enable Grid applications to become QoS compliant. We validate this approach through a case study of an image processing task derived from a nanoscale structures application.     

云计算环境下服务中间件动态管理框架的设计与实现

面向服务的软件开发过程会涉及不同种类以及层次的服务中间件,这一多层次、多种类、多依赖关系的服务中间件环境,在配置、管理与维护上均会给服务开发人员带来额外的开销与负担,直接影响开发效率。设计并实现了一个云计算环境下的服务软件设备动态管理框架,该框架可以根据开发人员需求,透明地完成服务中间件环境的配置与提供,并对服务中间件环境进行动态的健康管理与维护,保障服务中间件环境的稳定性与可靠性。     

An Information Service for Grid Virtual Organization: Architecture, Implementation and Evaluation

Information Service is the heart of the entire Grid software infrastructure. It maintains various information in a Grid environment, and provides this information to users on request. We present an Information Service architecture for information capturing, aggregation, and provisioning in a Grid Virtual Organization (VO). This Information Service is a hierarchical structure which consists of VO layer, site layer and resource layer. The architecture defines downloadable and pluggable information sensors for portability and flexibility of information capturing. The meta-data mechanism is incorporated into our Information Service for information organization and management. Experiments were conducted to evaluate the performance of the Information Service, and the results show that the Information Service presents satisfactory scalability with number of users and number of information amount. Our Information Service has been implemented based on the Globus Toolkit as a Grid service compliant to the Open Grid Services Architecture (OGSA) specifications.     

A computational economy for grid computing and its implementation in the Nimrod-G resource broker

Computational grids that couple geographically distributed resources such as PCs, workstations, clusters, and scientific instruments, have emerged as a next generation computing platform for solving large-scale problems in science, engineering, and commerce. However, application development, resource management, and scheduling in these environments continue to be a complex undertaking. In this article, we discuss our efforts in developing a resource management system for scheduling computations on resources distributed across the world with varying quality of service (QoS). Our service-oriented grid computing system called Nimrod-G manages all operations associated with remote execution including resource discovery, trading, scheduling based on economic principles and a user-defined QoS requirement. The Nimrod-G resource broker is implemented by leveraging existing technologies such as Globus, and provides new services that are essential for constructing industrial-strength grids. We present the results of experiments using the Nimrod-G resource broker for scheduling parametric computations on the World Wide Grid (WWG) resources that span five continents.