136 research outputs found

    Structure driven multiprocessor compilation of numeric problems

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    Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1991.Title as it appears in the Feb. 1991 M.I.T. Graduate List: Structure driven compilation of numeric problems.Includes bibliographical references (leaves 134-136).by G.N. Srinivasa Prasanna.Ph.D

    Hierarchical N-Body problem on graphics processor unit

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    Galactic simulation is an important cosmological computation, and represents a classical N-body problem suitable for implementation on vector processors. Barnes-Hut algorithm is a hierarchical N-Body method used to simulate such galactic evolution systems. Stream processing architectures expose data locality and concurrency available in multimedia applications. On the other hand, there are numerous compute-intensive scientific or engineering applications that can potentially benefit from such computational and communication models. These applications are traditionally implemented on vector processors. Stream architecture based graphics processor units (GPUs) present a novel computational alternative for efficiently implementing such high-performance applications. Rendering on a stream architecture sustains high performance, while user-programmable modules allow implementing complex algorithms efficiently. GPUs have evolved over the years, from being fixed-function pipelines to user programmable processors. In this thesis, we focus on the implementation of Barnes-Hut algorithm on typical current-generation programmable GPUs. We exploit computation and communication requirements present in Barnes-Hut algorithm to expose their suitability for user-programmable GPUs. Our implementation of the Barnes-Hut algorithm is formulated as a fragment shader targeting the selected GPU. We discuss implementation details, design issues, results, and challenges encountered in programming the fragment shader

    High accuracy binary black hole simulations with an extended wave zone

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    We present results from a new code for binary black hole evolutions using the moving-puncture approach, implementing finite differences in generalised coordinates, and allowing the spacetime to be covered with multiple communicating non-singular coordinate patches. Here we consider a regular Cartesian near zone, with adapted spherical grids covering the wave zone. The efficiencies resulting from the use of adapted coordinates allow us to maintain sufficient grid resolution to an artificial outer boundary location which is causally disconnected from the measurement. For the well-studied test-case of the inspiral of an equal-mass non-spinning binary (evolved for more than 8 orbits before merger), we determine the phase and amplitude to numerical accuracies better than 0.010% and 0.090% during inspiral, respectively, and 0.003% and 0.153% during merger. The waveforms, including the resolved higher harmonics, are convergent and can be consistently extrapolated to r→∞r\to\infty throughout the simulation, including the merger and ringdown. Ringdown frequencies for these modes (to (ℓ,m)=(6,6)(\ell,m)=(6,6)) match perturbative calculations to within 0.01%, providing a strong confirmation that the remnant settles to a Kerr black hole with irreducible mass Mirr=0.884355±20×10−6M_{\rm irr} = 0.884355\pm20\times10^{-6} and spin $S_f/M_f^2 = 0.686923 \pm 10\times10^{-6}

    Visualizing the memory performance of parallel programs with Chiron

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    Bibliography: leaves 78-81.This thesis describes Chiron, visualization system which helps programmers detect memory system bottlenecks in their shared-memory parallel applications. Chiron is different from most other performance debugging tools in that it uses three-dimensional graphics techniques to display vast amounts of memory-performance data. Both code-and data-oriented information can be presented in several views. These views have been designed to help the user detect problems which cause coherence interference or replacement interference. Chiron’s interactive user-interface enables the user to manipulate the views and home in on features which indicate memory system bottlenecks. The visualized data can be augmented with more detailed numerical and correlations between the separate views can be displayed. The effectiveness of Chiron is illustrated in this thesis by means of three case studies

    Computational Methods in Science and Engineering : Proceedings of the Workshop SimLabs@KIT, November 29 - 30, 2010, Karlsruhe, Germany

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    In this proceedings volume we provide a compilation of article contributions equally covering applications from different research fields and ranging from capacity up to capability computing. Besides classical computing aspects such as parallelization, the focus of these proceedings is on multi-scale approaches and methods for tackling algorithm and data complexity. Also practical aspects regarding the usage of the HPC infrastructure and available tools and software at the SCC are presented

    Robust and affordable localization and mapping for 3D reconstruction. Application to architecture and construction

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    La localización y mapeado simultáneo a partir de una sola cámara en movimiento se conoce como Monocular SLAM. En esta tesis se aborda este problema con cámaras de bajo coste cuyo principal reto consiste en ser robustos al ruido, blurring y otros artefactos que afectan a la imagen. La aproximación al problema es discreta, utilizando solo puntos de la imagen significativos para localizar la cámara y mapear el entorno. La principal contribución es una simplificación del grafo de poses que permite mejorar la precisión en las escenas más habituales, evaluada de forma exhaustiva en 4 datasets. Los resultados del mapeado permiten obtener una reconstrucción 3D de la escena que puede ser utilizada en arquitectura y construcción para Modelar la Información del Edificio (BIM). En la segunda parte de la tesis proponemos incorporar dicha información en un sistema de visualización avanzada usando WebGL que ayude a simplificar la implantación de la metodología BIM.Departamento de Informática (Arquitectura y Tecnología de Computadores, Ciencias de la Computación e Inteligencia Artificial, Lenguajes y Sistemas Informáticos)Doctorado en Informátic

    A Detailed Characterization of 60 GHz Wi-Fi (IEEE 802.11ad)

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    The emergence of wireless local area network (WLAN) standards and the global system of mobile communication (GSM) in the early 1990s incited tremendous growth in the demand for wireless connectivity. Iterative technological enhancements to cellular and WLAN improved wireless capacity and created a breadth of new mobile applications. The continued increase in display resolutions and image quality combined with streaming displacing satellite/cable has created unprecedented demands on wireless infrastructure. Data-caps on cellular networks deter over consumption and increasingly shift the growing burden to Wi-Fi networks. The traditional 2.4/5 GHz Wi-Fi bands have become overloaded and the increasing number of wireless devices in the home, public, and workplace create difficult challenges to deliver quality service to large numbers of client stations. In dense urban areas, the wireless medium is subjected to increased interference due to overlapping networks and other devices communicating in the same frequency bands. Improvements to conventional Wi-Fi are approaching their theoretical limits and higher order enhancements require idealized conditions which are seldom attainable in practice. In an effort to supplant to scaling capacity requirements a very high frequency WLAN amendment has been proposed (IEEE 802.11ad). IEEE 802.11ad, also referred to as Wireless Gigabit (WiGig), operates in the globally unlicensed 60 GHz band and offers channel bandwidths nearly 100x as wide as 802.11n. The higher bandwidth facilitates multi-Gbps throughput even with the use of lower complexity modulation coding schemes (MCS). IEEE 802.11ad relies heavily on rate adaptation and high beamforming gain to mitigate interference and fading as signals in the 60 GHz band suffer from higher atmospheric ab- sorption and free space path loss (FSPL). Due to the unique nature of 60 GHz wireless there have been numerous research efforts. Many studies have been directed at simulation and modeling of the 60 GHz channel. However modeling the channel is difficult as real- world environments are highly dynamic with varying link quality and conditions which cannot be accurately predicted by conventional techniques. Some research is focused on medium access control (MAC) enhancements to improve overall capacity by coordinating concurrent links or reducing communication overhead for example. Lastly, there has been a limited amount of real world testing of 802.11ad due to lack of availability of commercial platforms and measurement instrumentation. Some researchers tested early generation devices in certain use cases such as in vehicles for media streaming, in data centers to augment the wired network, or in basic indoor and outdoor environments. This research contains two main components. In the first study, analytical models are applied to estimate line of sight (LOS) 802.11ad performance for realistic antenna param- eters. The second part contains a comprehensive evaluation of performance and reliability of early generation 802.11ad hardware. This characterization emphasizes environmen- tal performance (e.g. conference room, cubical farm, open office), multiple-client testing (multiclient), multiple network interference (spatial re-use), and stability in the presence of station mobility, physical obstructions, and antenna misalignment. In order to evaluate 802.11ad, early generation platforms from technology vendors were used in extensive test suites. The hardware tested included docks for wireless personal area networking (WPAN) applications, client laptop stations, and reference design access points (APs). Finally, a customized proof-of-concept (PoC) platform was engineered which allowed finer control over front end antenna configuration parameters such as: topology, placement and orienta- tion. The PoC also served as a suitable means to identify practical limitations and system design engineering challenges associated with supporting directional multi-Gbps (DMG) communication in the 60 GHz band
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