| 1. |
- Olsson, Pelle, et al.
(författare)
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Boundary Modifications of the Dissipation Operators for the Three–Dimensional Euler Equations
- 1989
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Ingår i: Journal of Scientific Computing. - 0885-7474 .- 1573-7691. ; 4:2, s. 159-195
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Tidskriftsartikel (refereegranskat)abstract
- Explicit methods for the solution of fluid flow problems are of considerable interest in supercomputing. These methods parallelize well. The treatment of the boundaries is of particular interest with respect to both the numeric behavior of the solution and the computational efficiency. We have solved the three-dimensional Euler equations for a twisted channel using second-order, centered difference operators, and a three-stage Runge-Kutta method for the integration. Three different fourth-order dissipation operators were studied for numeric stabilization: one positive definite, one positive semidefinite, and one indefinite. The operators only differ in the treatment of the boundary. For computational efficiency all dissipation operators were designed with a constant bandwidth in matrix representation, with the bandwidth determined by the operator in the interior. The positive definite dissipation operator results in a significant growth in entropy close to the channel walls. The other operators maintain constant entropy. Several different implementations of the semidefinite operator obtained through factoring of the operator were also studied. We show the difference both in convergence rate and robustness for the different dissipation operators, and the factorizations of the operator due to Eriksson. For the simulations in this study one of the factorizations of the semidefinite operator required 70%–90% of the number of iterations required by the positive definite operator. The indefinite operator was sensitive to perturbations in the inflow boundary conditions. The simulations were performed on a 8,192 processor Connection Machine system CM-2. Full processor utilization was achieved, and a performance of 135 Mflops/sec in single precision was obtained. A performance of 1.1 Gflops/sec for a fully configured system with 65,536 processors was demonstrated.
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| 2. |
- Sandholm, Thomas, et al.
(författare)
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An OGSA-Based Accounting System for Allocation Enforcement across HPC Centers
- 2004
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Ingår i: ICSOC '04. - New York, NY, USA : ACM. ; , s. 279-288, s. 279-288
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Konferensbidrag (refereegranskat)abstract
- In this paper, we present an Open Grid Services Architecture (OGSA)-based decentralized allocation enforcement system, developed with an emphasis on a consistent data model and easy integration into existing scheduling, and workload management software at six independent high-performance computing centers forming a Grid known as SweGrid. The Swedish National Allocations Committee (SNAC) allocates resource quotas at these centers to research projects requiring substantial computer time. Our system, the SweGrid Accounting System (SGAS), addresses the need for soft real-time allocation enforcement on SweGrid for cross-domain job submission. The SGAS framework is based on state-of-the-art Web and Grid services technologies. The openness and ubiquity of Web services combined with the fine-grained resource control and cross-organizational security models of Grid services proved to be a perfect match for the SweGrid needs. Extensibility and customizability of policy implementations for the three different parties the system serves (the user, the resource manager, and the allocation authority) are key design goals. Another goal is end-to-end security and single sign-on, to allow resources-selected based on client policies-to act on behalf of the user when negotiating contracts with the bank in an environment where the six centers would continue to use their existing accounting policies and tools. We conclude this paper by showing the feasibility of SGAS, which is currently being deployed at the production sites, using simulations of reservation streams. The reservation streams are shaped using soft computing and policy-based algorithms.
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| 3. |
- Abdullah, Matin, et al.
(författare)
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SimDB: A Problem Solving Environment for Molecular Dynamics Simulation and Analysis
- 2000
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Konferensbidrag (refereegranskat)abstract
- The design of a software environment, SimDB, for molecular dynamics simulation and analysis is presented as an example of virtual laboratories enabled by high-speed networks connecting substantial computing and storage resources with more modest local compuation and visualization resources available to research groups. SimDB includes large-scale, dynamic, distributed data repositories. The simulated data sets, trajectories, are usually interpreted through reduced data sets, processed data sets, calculated by analysis functions. Both trajectory data and processed data are saved, but in differnt data bases, with processed data bases having several smaller objects for each trajectory. A browser based user interface with a well defined API allows for a wide array of analysis functions. Analysis functions are executed only if the requested analysis result is not available. The ability to incorporate user defined functions is a critical feature of SimDB.
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| 4. |
- Ali, Ayaz, et al.
(författare)
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Adaptive Computation of Self Sorting In-place FFTs on Hierarchical Memory Architectures
- 2007
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Ingår i: HIGH PERFORMANCE COMPUTING AND COMMUNICATIONS, PROCEEDINGS. - 9783540754435 ; , s. 372-383
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Konferensbidrag (refereegranskat)abstract
- Computing ”in-place and in-order”FFT poses a very difficult problem on hierarchical memory architectures where data movement can seriously degrade the performance. In this paper we present recursive formulation of a self sorting in-place FFT algorithm that adapts to the target architecture. For transform sizes where an in-place, in-order execution is not possible, we show how schedules can be constructed that use minimum work-space to perform the computation efficiently. In order to express and construct FFT schedules, we present a context free grammar that generates the FFT Schedule Specification Language. We conclude by comparing the performance of our in-place in-order FFT implementation with that of other well known FFT libraries. We also present a performance comparison between the out-of-place and in-place execution of various FFT sizes.
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| 5. |
- Ali, Ayaz, et al.
(författare)
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Empirical Auto-tuning Code Generator for FFT and Trigonometric Transforms
- 2007
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Konferensbidrag (refereegranskat)abstract
- We present an automatic, empirically tuned code genenrator for Real/Complex FFT and Trigonometric Transforms. The code generator is part of an adaptive and portable FFT computation framework - UHFFT. Performance portability over varying architectures is achieved by generating highly optimized set of straight line C codelets (micro-kernel) that adapt to the microprocessor architecture. The tuning is performed by generating several variants of same size codelet with different combinations of optimization parameters. The variants are iteratively compiled and evaluated to find the best implementation on a given platform. Apart from minimizing the operation count, the code generator optimizes for access pattern, register blocking, instruction schedule and structure of arrays. We present details of the optimizations conducted at several stages and the performance gain at each of those levels. We conclude the paper with discussion of the overall performance improvements due to this aggressive approach to generating optimized FFT kernels.
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| 6. |
- Ali, Ayaz, et al.
(författare)
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Scheduling FFT Computation on SMP and Multi-core Systems
- 2007
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Ingår i: Proceedings of the 21st annual international conference on Supercomputing. - New York, NY, USA : ACM. ; , s. 293-301
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Konferensbidrag (refereegranskat)abstract
- Increased complexity of memory systems to ameliorate the gap between the speed of processors and memory has made it increasingly harder for compilers to optimize an arbitrary code within a palatable amount of time. With the emergence of multicore (CMP), multiprocessor (SMP) and hybrid shared memory multiprocessor architectures, achieving high e ciency is becoming even more challenging. To address the challenge to achieve high e ciency in performance critical applications, domain speci c frameworks have been developed that aid the compilers in scheduling the computations. We have developed a portable framework for the Fast Fourier Transform (FFT) that achieves high e ciency by automatically adapting to various architectural features. Adapting to parallel architectures by searching through all the combinations of schedules (plans) is an expensive task, even when the search is conducted in parallel. In this paper, we develop heuristics to simplify the generation of better schedules for parallel FFT computations on CMP/SMP systems. We evaluate the performance of OpenMP and PThreads implementations of FFT on a number of latest architectures. The performance of parallel FFT schedules is compared with that of the best plan generated for sequential FFT and the speedup for di erent number of processors is reported. In the end, we also present a performance comparison between the UHFFT and FFTW implementations.
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| 7. |
- Austin, S, et al.
(författare)
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Atmospheric Balloon Studies : A Collaboration Between Minority and Traditional Undergraduate and Graduate Institutions
- 2008
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Konferensbidrag (refereegranskat)abstract
- The Minority University Consortium for Earth and Space Sciences (MUCESS), a collaboration among diverse minority institutions dedicated to increasing the number of underrepresented students pursuing professional and research careers in Earth and Atmospheric Science and Space Science, were informed that they had been funded by NSF for a faculty and student research opportunity in atmospheric science. Among the institutions only Medgar Evers College, City University of New York had a prior program in ozone monitoring and a bachelor's degree in environmental science. The funding provided an opportunity to strengthen the initial team with the addition of G. Morris, Valparaiso University and B. Lefer, University of Houston as both had an ongoing ozone research program. The grant enabled MEC to continue their activities and the University of Houston-Downtown to increase the number of launches per year. South Carolina State University is able to strengthen their support system and incorporate the activities into both their academic and outreach programs. The opportunity to partner with G. Morris and B. Lefer will enable the institutions to expand their ozonesonde launches to include both tropospheric and stratospheric ozone distribution and transport. Faculty student workshops will be an integral part of the program as the activity will increase the scientific knowledge of the participants. The program provides an opportunity for minority students to pursue studies in the geosciences and develop the skills and knowledge to pursue graduate degrees in the discipline.
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| 8. |
- Baillie, Clive, et al.
(författare)
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QCD with Dynamical Fermions on the Connection Machine
- 1989
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Konferensbidrag (refereegranskat)abstract
- We have implemented Quantum Chromo-Dynamics (QCD) on the massively parallel Connection Machine in *Lisp. The code uses dynamical Wilson fermions and the Hybrid Monte Carlo Algorithm (HMCA) to update the lattice. We describe our program and give performance measurements for it. With no tuning or optimization, the code runs at approximately 500 to 1000 MFLOPS on a 64-K Connection Machine, model CM-2, depending on the VP ratio.
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| 9. |
- Berman, F., et al.
(författare)
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New grid scheduling and rescheduling methods in the GrADS Project
- 2005
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Ingår i: International journal of parallel programming. - : Springer Science and Business Media LLC. - 0885-7458 .- 1573-7640. ; 33:3-Feb, s. 209-229
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Tidskriftsartikel (refereegranskat)abstract
- The goal of the Grid Application Development Software (GrADS) Project is to provide programming tools and an execution environment to ease program development for the Grid. This paper presents recent extensions to the GrADS software framework: a new approach to scheduling workflow computations, applied to a 3-D image reconstruction application; a simple stop/migrate/restart approach to rescheduling Grid applications, applied to a QR factorization benchmark; and a process-swapping approach to rescheduling, applied to an N-body simulation. Experiments validating these methods were carried out on both the GrADS MacroGrid (a small but functional Grid) and the MicroGrid (a controlled emulation of the Grid).
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| 10. |
- Berman, F., et al.
(författare)
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The GrADS project : Software support for high-level grid application development
- 2001
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Ingår i: The international journal of high performance computing applications. - : SAGE Publications. - 1094-3420 .- 1741-2846. ; 15:4, s. 327-344
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Tidskriftsartikel (refereegranskat)abstract
- Advances in networking technologies will soon make it possible to use the global information infrastructure in a qualitatively different way-as a computational as well as an information resource. As described in the recent book The Grid: Blueprint for a New Computing Infrastructure, this Grid will connect the nation's computers, databases, instruments, and people in a seamless web of computing and distributed intelligence, which can be used in an on demand fashion as a problem-solving resource in many fields of human endeavor-and, in particular, science and engineering. The availability of grid resources will give rise to dramatically new classes of applications, in which computing resources are no longer localized but, rather, distributed, heterogeneous, and dynamic; computation is increasingly sophisticated and multidisciplinary; and computation is integrated into our daily lives and, hence, subject to stricter time constraints than at present. The impact of these new applications will be pervasive, ranging from new systems for scientific inquiry, through computing support for crisis management, to the use of ambient computing to enhance personal mobile computing environments. To realize this vision, significant scientific and technical obstacles must be overcome. Principal among these is usability. The goal of the Grid Application Development Software (GrADS) project is to simplify distributed heterogeneous computing in the same way that the World Wide Web simplified information sharing over the Internet. To that end, the project is exploring the scientific and technical problems that must be solved to make it easier for ordinary scientific users to develop, execute, and tune applications on the Grid. In this paper, the authors describe the vision and strategies underlying the GrADS project, including the base software architecture for grid execution and performance monitoring, strategies and tools for construction of applications from libraries of grid-aware components, and development of innovative new science and engineering applications that can exploit these new technologies to run effectively in grid environments.
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