| 1. |
- Asplund, Mikael, et al.
(författare)
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Middleware extensions that trade consistency for availability
- 2009
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Ingår i: CONCURRENCY AND COMPUTATION-PRACTICE and EXPERIENCE. - : John Wiley & Sons. - 1532-0626 .- 1532-0634. ; 21:9, s. 1181-1203
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Tidskriftsartikel (refereegranskat)abstract
- Replicated distributed object systems are deployed to provide timely and reliable services to actors at distributed locations. This paper treats applications in which data updates are dependent on satisfaction of integrity constraints over multiple objects. Network partitions, caused by occasional link failures, overload or attacks create problems in keeping both consistency and availability in such networks. We propose a means of achieving higher availability by providing partition-awareness in middleware. The general approach has been illustrated by implementing a number of CORBA extensions that trade consistency for availability during network partitions. This paper contains a thorough experimental evaluation that presents the gains and costs of our approach. The experiments clearly illustrate the benefit of our protocols in terms of significantly higher availability and the number of performed operations.
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| 2. |
- Brandic, Ivona, et al.
(författare)
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Specification, Planning, and Execution of QoS-awareGrid Workflows within the Amadeus Environment
- 2008
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Ingår i: Concurrency and Computation. - : John Wiley & Sons. - 1532-0626 .- 1532-0634. ; 20:4, s. 331-345
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Tidskriftsartikel (refereegranskat)abstract
- Commonly, at a high level of abstraction Grid applications are specified based on the workflow paradigm. However, majority of Grid workflow systems either do not support Quality of Service (QoS), or provide only partial QoS support for certain phases of the workflow lifecycle. In this paper we present Amadeus, which is a holistic service-oriented environment for QoS-aware Grid workflows. Amadeus considers user requirements, in terms of QoS constraints, during workflow specification, planning, and execution. Within the Amadeus environment workflows and the associated QoS constraints are specified at a high level using an intuitive graphical notation. A distinguishing feature of our system is the support of a comprehensive set of QoS requirements, which considers in addition to performance and economical aspects also legal and security aspects. A set of QoS-aware service-oriented components is provided for workflow planning to support automatic constraint-based service negotiation and workflow optimization. For improving the efficiency of workflow planning we introduce a QoS-aware workflow reduction technique. Furthermore, we present our static and dynamic planning strategies for workflow execution in accordance with user-specified requirements. For each phase of the workflow lifecycle we experimentally evaluate the corresponding Amadeus components.
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| 3. |
- Elmroth, Erik, 1964-, et al.
(författare)
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A standards-based Grid resource brokering service supporting advance reservations, coallocation and cross-Grid interoperability
- 2009
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Ingår i: Concurrency and Computation. - : Wiley. - 1532-0626 .- 1532-0634. ; 21:18, s. 2298-2335
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Tidskriftsartikel (refereegranskat)abstract
- The problem of Grid-middleware interoperability is addressed by the design and analysis of a feature-rich, standards-based framework for all-to-all cross-middleware job submission.The architecture is designed with focus on generality and flexibility and builds on extensive use, internally and externally, of (proposed) Web and Grid services standards such asWSRF, JSDL, GLUE, and WS-Agreement. The external use providesthe foundation for easy integration into specific middlewares,which is performed by the design of a small set of plugins for each middleware. Currently, plugins are provided for integrationinto Globus Toolkit 4 and NorduGrid/ARC. The internal use of standard formats facilitates customizationof the job submission service by replacement of custom components for performing specific well-defined tasks.Most importantly, this enables the easy replacement of resource selection algorithms by algorithms that addresses the specific needs of a particular Grid environment and job submission scenario.By default, the service implements a decentralized brokering policy, strivingto optimize the performance for the individual user by minimizing the response time for each job submitted. The algorithms in our implementation perform resource selectionbased on performance predictions, and provide support for advance reservations as well as coallocation of multiple resources for coordinated use.The performance of the system is analyzed with focuson overall service throughput (up to over 250 jobs per minute)and individual job submission response time (down to under one second).
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| 4. |
- Fahringer, Thomas, et al.
(författare)
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ASKALON : a tool set for clusterand Grid computing
- 2005
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Ingår i: Concurrency and Computation. - : Wiley. - 1532-0626 .- 1532-0634. ; 17:2-4, s. 143-169
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Tidskriftsartikel (refereegranskat)abstract
- Performance engineering of parallel and distributed applications is a complex task that iterates through various phases, ranging from modeling and prediction, to performance measurement, experiment management, data collection, and bottleneck analysis. There is no evidence so far that all of these phases should/can be integrated into a single monolithic tool. Moreover, the emergence of computational Grids as a common single wide-area platform for high-performance computing raises the idea to provide tools as interacting Grid services that share resources, support interoperability among different users and tools, and, most importantly, provide omnipresent services over the Grid. We have developed the ASKALON tool set to support performance-oriented development of parallel and distributed (Grid) applications. ASKALON comprises four tools, coherently integrated into a service-oriented architecture. SCALEA is a performance instrumentation, measurement, and analysis tool of parallel and distributed applications. ZENTURIO is a general purpose experiment management tool with advanced support for multi-experiment performance analysis and parameter studies. AKSUM provides semi-automatic high-level performance bottleneck detection through a special-purpose performance property specification language. The PerformanceProphet enables the user to model and predict the performance of parallel applications at the early stages of development. In this paper we describe the overall architecture of the ASKALON tool set and outline the basic functionality of the four constituent tools. The structure of each tool is based on the composition and sharing of remote Grid services, thus enabling tool interoperability. In addition, a data repository allows the tools to share the common application performance and output data that have been derived by the individual tools. A service repository is used to store common portable Grid service implementations. A general-purpose Factory service is employed to create service instances on arbitrary remote Grid sites. Discovering and dynamically binding to existing remote services is achieved through registry services. The ASKALON visualization diagrams support both online and post-mortem visualization of performance and output data. We demonstrate the usefulness and effectiveness of ASKALON by applying the tools to real-world applications.
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| 5. |
- Gardfjäll, Peter, 1979-, et al.
(författare)
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Scalable Grid-wide capacity allocation with the SweGrid Accounting System (SGAS)
- 2008
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Ingår i: Concurrency and Computation. - : Wiley. - 1532-0626 .- 1532-0634. ; 20:18, s. 2089-2122
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Tidskriftsartikel (refereegranskat)abstract
- The SweGrid Accounting System (SGAS) allocates capacity in collaborative Grid environments by coordinating enforcement of Grid-wide usage limits as a means to offer usage guarantees and prevent overuse. SGAS employs a credit-based allocation model where Grid capacity is granted to projects via Grid-wide quota allowances that can be spent across the Grid resources. The resources Collectively enforce these allowances in a soft, real-time manner. SGAS is built on service-oriented principles with a strong focus on interoperability, and Web services standards. This article covers the SGAS design and implementation, which, besides addressing inherent Grid challenges (scale, security, heterogeneity, decentralization), emphasizes generality and flexibility to produce a customizable system with lightweight integration into different middleware and scheduling system combinations. We focus the discussion around the system design, a flexible allocation model, middleware integration experiences and scalability improvements via a distributed virtual banking system, and finally, an extensive set of testhed experiments. The experiments evaluate the performance of SGAS in terms of response times, request throughput, overall system scalability, and its performance impact on the Globus Toolkit 4 job submission software. We conclude that, for all practical purposes, the quota enforcement overhead incurred by SGAS on job submissions is not a limiting factor for the job-handling capacity of the job submission software.
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| 6. |
- Granat, Robert, et al.
(författare)
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Parallel Eigenvalue Reordering in Real Schur Forms
- 2009
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Ingår i: Concurrency and Computation. - : Wiley. - 1532-0626 .- 1532-0634. ; 21:9, s. 1225-1250
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Tidskriftsartikel (refereegranskat)abstract
- A parallel algorithm for reordering the eigenvalues in the real Schur form of a matrix is presented and discussed. Our novel approach adopts computational windows and delays multiple outside-window updates until each window has been completely reordered locally. By using multiple concurrent windows the parallel algorithm has a high level of concurrency, and most work is level 3 BLAS operations. The presented algorithm is also extended to the generalized real Schur form. Experimental results for ScaLAPACK-style Fortran 77 implementations on a Linux cluster confirm the efficiency and scalability of our algorithms in terms of more than 16 times of parallel speedup using 64 processors for large-scale problems. Even on a single processor our implementation is demonstrated to perform significantly better compared with the state-of-the-art serial implementation.
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| 7. |
- Hughes, Danny, et al.
(författare)
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An experiment with reflective middleware to support grid-based flood monitoring
- 2008
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Ingår i: Concurrency and Computation. - : Wiley. - 1532-0626 .- 1532-0634. ; 20:11, s. 1303-1316
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Flooding is a growing problem, which affects more than 10% of the U.K. population. The cost of damage caused by flooding correlates closely with the warning time given before a flood event, making flood monitoring and prediction critical to minimizing the cost of flood damage. This paper describes a wireless sensor network (WSN) for flood warning, which is capable of not only integrating with remote fixed-network grids for computationally intensive flood modelling purposes but also performing on-site grid computation. This functionality is supported by the reflective and component-based GridKit middleware, which provides support for both WSN and grid application domains. Copyright (c) 2007 John Wiley & Sons, Ltd.
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| 8. |
- Kessler, Christoph, 1966-, et al.
(författare)
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Classification and generation of schedules for VLIW processors
- 2007
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Ingår i: Concurrency. - : Wiley. - 1040-3108 .- 1096-9128. ; 19, s. 2369-2389
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Tidskriftsartikel (refereegranskat)abstract
- We identify and analyze different classes of schedules for instruction-level parallel processor architectures. The classes are induced by various common techniques for generating or enumerating them, such as integer linear programming or list scheduling with backtracking. In particular, we study the relationship between VLIW schedules and their equivalent linearized forms (which may be used, e.g., with superscalar processors), and we identify classes of VLIW schedules that can be created from a linearized form using an in-order VLIW compaction heuristic, which is just the static equivalent of the dynamic instruction dispatch algorithm of in-order issue superscalar processors. We formulate and give a proof of the dominance of greedy schedules for instruction-level parallel architectures where all instructions have multiblock reservation tables, and we show how scheduling anomalies can occur in the presence of instructions with non-multiblock reservation tables. We also show that, in certain situations, certain schedules generally cannot be constructed by incremental scheduling algorithms that are based on topological sorting of the data dependence graph. We also discuss properties of strongly linearizable schedules, out-of-order schedules and non-dawdling schedules, and show their relationships to greedy schedules and to general schedules. We summarize our findings as a hierarchy of classes of VLIW schedules. Finally we provide an experimental evaluation showing the sizes of schedule classes in the above hierarchy, for different benchmarks and example VLIW architectures, including a single-cluster version of the TI C62x DSP processor and variants of that. Our results can sharpen the interpretation of the term optimality used with various methods for optimal VLIW scheduling, and help to identify sets of schedules that can be safely ignored when searching for a time-optimal schedule.
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| 9. |
- Kessler, Christoph, et al.
(författare)
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Optimal integrated code generation for VLIW architectures
- 2006
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Ingår i: Concurrency and Computation. - : Wiley. - 1532-0626 .- 1532-0634. ; 18:11, s. 1353-1390
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Tidskriftsartikel (refereegranskat)abstract
- We present a dynamic programming method for optimal integrated code generation for basic blocks that minimizes execution time. It can be applied to single-issue pipelined processors, in-order-issue superscalar processors, VLIW architectures with a single homogeneous register set, and clustered VLIW architectures with multiple register sets. For the case of a single register set, our method simultaneously copes with instruction selection, instruction scheduling, and register allocation. For clustered VLIW architectures, we also integrate the optimal partitioning of instructions, allocation of registers for temporary variables, and scheduling of data transfer operations between clusters. Our method is implemented in the prototype of a retargetable code generation framework for digital signal processors (DSPs), called OPTIMIST. We present results for the processors ARM9E, TI C62x, and a single-cluster variant of C62x. Our results show that the method can produce optimal solutions for small and (in the case of a single register set) medium-sized problem instances with a reasonable amount of time and space. For larger problem instances, our method can be seamlessly changed into a heuristic. Copyright (c) 2006 John Wiley & Sons, Ltd.
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| 10. |
- Laure, Erwin, et al.
(författare)
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Performance Engineering in Data Grids
- 2005
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Ingår i: Concurrency and Computation. - : Wiley. - 1532-0626 .- 1532-0634. ; 17:2-4, s. 171-191
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Tidskriftsartikel (refereegranskat)abstract
- The vision of Grid computing is to facilitate worldwide resource sharing among distributed collaborations. With the help of numerous national and international Grid projects, this vision is becoming reality and Grid systems are attracting an ever increasing user base. However, Grids are still quite complex software systems whose efficient use is a difficult and error-prone task. In this paper we present performance engineering techniques that aim to facilitate an efficient use of Grid systems, in particular systems that deal with the management of large-scale data sets in the tera- and petabyte range (also referred to as data Grids). These techniques are applicable at different layers of a Grid architecture and we discuss the tools required at each of these layers to implement them. Having discussed important performance engineering techniques, we investigate how major Grid projects deal with performance issues particularly related to data Grids and how they implement the techniques presented.
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| 11. |
- Riedel, M., et al.
(författare)
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Interoperation of World-Wide Production e-Science Infrastructures
- 2009
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Ingår i: Concurrency and Computation. - : Wiley. - 1532-0626 .- 1532-0634. ; 21:8, s. 961-990
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Tidskriftsartikel (refereegranskat)abstract
- Many production Grid and e-Science infrastructures have begun to offer services to end-users during the past several years with an increasing number of scientific applications that require access to a wide variety of resources and services in multiple Grids. Therefore, the Grid Interoperation Now-Community Group of the Open Grid Forum-organizes and manages interoperation efforts among those production Grid infrastructures to reach the goal of a world-wide Grid vision on a technical level in the near future. This contribution highlights fundamental approaches of the group and discusses open standards in the context of production e-Science infrastructures.
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| 12. |
- Waliullah, Mridha Mohammad, 1979, et al.
(författare)
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Schemes for avoiding starvation in transactional memory systems
- 2009
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Ingår i: Concurrency Computation Practice and Experience. - : Wiley. - 1532-0634 .- 1532-0626. ; 21:7, s. 859-873
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Tidskriftsartikel (refereegranskat)abstract
- Transactional memory systems trade ease of programming with run-time performance losses in handling transactions. This paper focuses on starvation effects that show up in systems where unordered transactions are committed on a demand-driven basis. Such simple commit arbitration policies are prone to starvation. The design issues for commit arbitration policies are analyzed and novel policies that reduce the amount of wasted computation due to roll-back and, most important, that avoid starvation are proposed. We analyze in detail how to incorporate them in the transactional coherence and consistency protocol as well as a scalable version of it. The proposed schemes are shown to have no impact on the common-case performance and add quite modest complexity to the baseline protocol. Copyright (C) 2008 John Wiley & Sons, Ltd.
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