We describe an interactive toolkit used to perform comparative analysis of two or more data sets arising from numerical simulations. Several techniques have been incorporated into this toolkit, including (1) successiv...
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We describe an interactive toolkit used to perform comparative analysis of two or more data sets arising from numerical simulations. Several techniques have been incorporated into this toolkit, including (1) successive visualization of individual data sets, (2) data comparison techniques such as computation and visualization of the differences between data sets, and (3) image comparison methods such as scalar field height profiles plotted in a common coordinate system. We describe each technique in detail and show example usage in an industrial application aimed at designing an efficient, low-NOx burner for industrial furnaces. Critical insights are obtained by interactively adjusted color maps, data culling, and data manipulation. New paradigms for scaling small values in the data comparison technique are described. The display device used for this application was the CAVE virtual reality theater, and we describe the user interface to the visualization toolkit and the benefits of immersive 3D visualization for comparative analysis.
The Globus project is a multi-institutional research effort that seeks to enable the construction of computational grids providing pervasive, dependable, and consistent access to high-performance computational resourc...
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The Globus project is a multi-institutional research effort that seeks to enable the construction of computational grids providing pervasive, dependable, and consistent access to high-performance computational resources, despite geographical distribution of both resources and users. Computational grid technology is being viewed as a critical element of future high-performance computing environments that will enable entirely new classes of computation-oriented applications, much as the World Wide Web fostered the development of new classes of information-oriented applications. In this paper, we report on the status of the Globus project as of early 1998. We describe the progress that has been achieved to date in the development of the Globus toolkit, a set of core services for constructing grid tools and applications. We also discuss the Globus Ubiquitous Supercomputing Testbed Organization (GUSTO) that we have constructed to enable large-scale evaluation of Globus technologies, and we review early experiences with the development of large-scale grid applications on the GUSTO testbed.
Motivated by applications in robotics, we formulate the problem of minimizing the total angle cost of a TSP tour for a set of points in Euclidean space, where the angle cost of a tour is the sum of the direction chang...
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Motivated by applications in robotics, we formulate the problem of minimizing the total angle cost of a TSP tour for a set of points in Euclidean space, where the angle cost of a tour is the sum of the direction changes at the points. We establish the NP-hardness of both this problem and its relaxation to the cycle cover problem. We then consider the issue of designing approximation algorithms for these problems and show that both problems can be approximated to within a ratio of O(log n) in polynomial time. We also consider the problem of simultaneously approximating both the angle and the length measure for a TSP tour. In studying the resulting tradeoff, we choose to focus on the sum of the two performance ratios and provide tight bounds on the sum. Finally, we consider the external value of the angle measure and obtain essentially tight bounds for it. In this paper we restrict our attention to the planar setting, but all our results are easily extended to higher dimensions.
In this paper we prove the nonexistence of quaternary linear codes with parameters [51, 4, 37]. This result gives the exact value of nq(k, d) for q = 4, k = 4, d = 37 and 38. These were the only minimum distances for ...
In this paper we present a method for discovering approximately common motifs (also known as active motifs) in multiple RNA secondary structures. The secondary structures can be represented as ordered trees (i.e., the...
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Multithreaded execution models attempt to combine some aspects of dataflow-like execution with von Neumann model execution. Their main objective is to mask the latency of inter-processor communications and remote memo...
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Multithreaded execution models attempt to combine some aspects of dataflow-like execution with von Neumann model execution. Their main objective is to mask the latency of inter-processor communications and remote memory accesses in large scale multiprocessors. An important issue in the analysis and evaluation of multithreaded execution is the design and performance of the storage hierarchy. Because of the sequential execution of threads, the locality of access within an executing thread can be exploited using registers and cache. At the inter-thread level, however, the locality of accesses to memory and its effect on the cache is not yet well understood. A storage model which can exploit this locality is developed and evaluated. The results indicate there is a large amount of inter-thread locality that can be exploited and that we can get an efficient storage system by exploiting the characteristics of nonblocking threads.
The first part of this paper presents new proof systems and improved non-approximability results. In particular we present a proof system for NP using logarithmic randomness and two amortized free bits, so that Max cl...
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The first part of this paper presents new proof systems and improved non-approximability results. In particular we present a proof system for NP using logarithmic randomness and two amortized free bits, so that Max clique is hard within N/sup 1/3/ and chromatic number within N/sup 1/5/. We also show hardness of 38/37 for Max-3-SAT, 27/26 for vertex cover, 82/81 for Max-cut, and 94/93 for Max-2-SAT. The second part of this paper presents a "reverse" of the FGLSS connection by showing that an NP-hardness result for the approximation of Max clique to within a factor of N/sup 1/(g+1/) would imply a probabilistic verifier for NP with logarithmic randomness and amortized free-bit complexity g. We also show that "existing techniques" won't yield proof systems of less than two bits in amortized free bit complexity. Finally, we initiate a comprehensive study of PCP and FPCP parameters, proving several triviality results and providing several useful transformations.
We describe the design of a parallel global atmospheric chemical tracer model. This is part of a larger Earth Systems Model (ESM) for atmospheric dynamics and physics, and ocean physics. The ESM will be used for globa...
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We describe the design of a parallel global atmospheric chemical tracer model. This is part of a larger Earth Systems Model (ESM) for atmospheric dynamics and physics, and ocean physics. The ESM will be used for global warming and ozone depletion studies, among others. The goal is to parallelize the chemistry model to run efficiently on current and future parallel architectures, including the Sequoia archival database. We describe the preliminary design, especially the detailed timing model, and some initial validations. We have found a timing modeling very valuable for designing for a large range of architectures.< >
In this paper, we study the heterogeneous use of two programming paradigms for heterogeneous computing called Cluster-M and HAsC. Both paradigms can efficiently support heterogeneous networks by preserving a level of ...
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