Dynamic task scheduling and binding for many-core systems through stream rewriting

This thesis proposes a novel model of computation, called stream rewriting, for the specification and implementation of highly concurrent applications. Basically, the active tasks of an application and their dependencies are encoded as a token stream, which is iteratively modified by a set of rewriting rules at runtime. In order to estimate the performance and scalability of stream rewriting, a large number of experiments have been evaluated on many-core systems and the task management has been implemented in software and hardware.In dieser Dissertation wurde Stream Rewriting als eine neue Methode entwickelt, um Anwendungen mit einer großen Anzahl von dynamischen Tasks zu beschreiben und effizient zur Laufzeit verwalten zu können. Dabei werden die aktiven Tasks in einem Datenstrom verpackt, der zur Laufzeit durch wiederholtes Suchen und Ersetzen umgeschrieben wird. Um die Performance und Skalierbarkeit zu bestimmen, wurde eine Vielzahl von Experimenten mit Many-Core-Systemen durchgeführt und die Verwaltung von Tasks über Stream Rewriting in Software und Hardware implementiert

Teaching Graphics Processing and Architecture using a Hardware Prototyping Approach

Abstract-Since its introduction over two decades ago, graphics hardware has continued to evolve to improve rendering performance and increase programmability. While most undergraduate courses in computer graphics focus on rendering algorithms and programming APIs, we have recently created an undergraduate senior elective course that focuses on graphics processing and architecture, with a strong emphasis on laboratory work targeting hardware prototyping of the 3D rendering pipeline. In this paper, we present the overall course layout and FPGA-based laboratory infrastructure, that by the end of the semester enables students to implement an OpenGL-compliant graphics processor. To our knowledge, this class is the first that takes a hardware prototyping approach to teaching computer graphics and architecture

GPGPU-Enabled Physics Based Deformed Model Simulation

Computer simulation techniques are widely adopted nowadays in many areas like manufacturing, engineering, graphics, animation, virtual reality and so on. However, the standard finite element based simulation is notorious for its expensive computation. To address this challenge, I present a GPU-based parallel implementation for simulating large elastic deformation. Classic modal analysis provides a set of orthonormal bases vectors, which span a spectral space encoding the dynamics of the elastic body. As each basis vector is orthogonal to each other, the computation is completely decoupled and can be well-fit into the modern GPGPU platform. We further explore the latest feature of NVIDIA CUDA so that the result of GPU computation can be directly used for upcoming rendering/visualization and a significant amount of overheads for transmitting data from client GPU and host CPU via the PCI-Express bus are avoided. Real-time simulation is made possible with this technique for many cases that otherwise is not possible

Hardware implementations of computer-generated holography: a review

Computer-generated holography (CGH) is a technique to generate holographic interference patterns. One of the major issues related to computer hologram generation is the massive computational power required. Hardware accelerators are used to accelerate this process. Previous publications targeting hardware platforms lack performance comparisons between different architectures and do not provide enough information for the evaluation of the suitability of recent hardware platforms for CGH algorithms. We aim to address these limitations and present a comprehensive review of CGH-related hardware implementations

GPU data structures for graphics and vision

Graphics hardware has in recent years become increasingly programmable, and its programming APIs use the stream processor model to expose massive parallelization to the programmer. Unfortunately, the inherent restrictions of the stream processor model, used by the GPU in order to maintain high performance, often pose a problem in porting CPU algorithms for both video and volume processing to graphics hardware. Serial data dependencies which accelerate CPU processing are counterproductive for the data-parallel GPU. This thesis demonstrates new ways for tackling well-known problems of large scale video/volume analysis. In some instances, we enable processing on the restricted hardware model by re-introducing algorithms from early computer graphics research. On other occasions, we use newly discovered, hierarchical data structures to circumvent the random-access read/fixed write restriction that had previously kept sophisticated analysis algorithms from running solely on graphics hardware. For 3D processing, we apply known game graphics concepts such as mip-maps, projective texturing, and dependent texture lookups to show how video/volume processing can benefit algorithmically from being implemented in a graphics API. The novel GPU data structures provide drastically increased processing speed, and lift processing heavy operations to real-time performance levels, paving the way for new and interactive vision/graphics applications.Graphikhardware wurde in den letzen Jahren immer weiter programmierbar. Ihre APIs verwenden das Streamprozessor-Modell, um die massive Parallelisierung auch für den Programmierer verfügbar zu machen. Leider folgen aus dem strikten Streamprozessor-Modell, welches die GPU für ihre hohe Rechenleistung benötigt, auch Hindernisse in der Portierung von CPU-Algorithmen zur Video- und Volumenverarbeitung auf die GPU. Serielle Datenabhängigkeiten beschleunigen zwar CPU-Verarbeitung, sind aber für die daten-parallele GPU kontraproduktiv . Diese Arbeit präsentiert neue Herangehensweisen für bekannte Probleme der Video- und Volumensverarbeitung. Teilweise wird die Verarbeitung mit Hilfe von modifizierten Algorithmen aus der frühen Computergraphik-Forschung an das beschränkte Hardwaremodell angepasst. Anderswo helfen neu entdeckte, hierarchische Datenstrukturen beim Umgang mit den Schreibzugriff-Restriktionen die lange die Portierung von komplexeren Bildanalyseverfahren verhindert hatten. In der 3D-Verarbeitung nutzen wir bekannte Konzepte aus der Computerspielegraphik wie Mipmaps, projektive Texturierung, oder verkettete Texturzugriffe, und zeigen auf welche Vorteile die Video- und Volumenverarbeitung aus hardwarebeschleunigter Graphik-API-Implementation ziehen kann. Die präsentierten GPU-Datenstrukturen bieten drastisch schnellere Verarbeitung und heben rechenintensive Operationen auf Echtzeit-Niveau. Damit werden neue, interaktive Bildverarbeitungs- und Graphik-Anwendungen möglich

Double-edged Sword: An in-depth analysis of browser fingerprints for web tracking and bot defenses

The use of browser fingerprints is a double-edged sword. While they can protect users' security by defending against bot and fraud attacks, they can also be used for web tracking, which violates individual users' privacy. While acknowledging that the use of browser fingerprints is a double-edged sword, my work is to achieve a balance that maximizes the benefits and minimizes the risks. In the following section, I provide a comprehensive examination of browser fingerprints and demonstrates how they can be improved to better protect users’ privacy while still providing a valuable tool in defending against bot and fraud attacks

Interactive Visualization on High-Resolution Tiled Display Walls with Network Accessible Compute- and Display-Resources

Papers number 2-7 and appendix B and C of this thesis are not available in Munin: 2. Hagen, T-M.S., Johnsen, E.S., Stødle, D., Bjorndalen, J.M. and Anshus, O.: 'Liberating the Desktop', First International Conference on Advances in Computer-Human Interaction (2008), pp 89-94. Available at http://dx.doi.org/10.1109/ACHI.2008.20 3. Tor-Magne Stien Hagen, Oleg Jakobsen, Phuong Hoai Ha, and Otto J. Anshus: 'Comparing the Performance of Multiple Single-Cores versus a Single Multi-Core' (manuscript)4. Tor-Magne Stien Hagen, Phuong Hoai Ha, and Otto J. Anshus: 'Experimental Fault-Tolerant Synchronization for Reliable Computation on Graphics Processors' (manuscript) 5. Tor-Magne Stien Hagen, Daniel Stødle and Otto J. Anshus: 'On-Demand High-Performance Visualization of Spatial Data on High-Resolution Tiled Display Walls', Proceedings of the International Conference on Imaging Theory and Applications and International Conference on Information Visualization Theory and Applications (2010), pages 112-119. Available at http://dx.doi.org/10.5220/0002849601120119 6. Bård Fjukstad, Tor-Magne Stien Hagen, Daniel Stødle, Phuong Hoai Ha, John Markus Bjørndalen and Otto Anshus: 'Interactive Weather Simulation and Visualization on a Display Wall with Many-Core Compute Nodes', Para 2010 – State of the Art in Scientific and Parallel Computing. Available at http://vefir.hi.is/para10/extab/para10-paper-60 7. Tor-Magne Stien Hagen, Daniel Stødle, John Markus Bjørndalen, and Otto Anshus: 'A Step towards Making Local and Remote Desktop Applications Interoperable with High-Resolution Tiled Display Walls', Lecture Notes in Computer Science (2011), Volume 6723/2011, 194-207. Available at http://dx.doi.org/10.1007/978-3-642-21387-8_15The vast volume of scientific data produced today requires tools that can enable scientists to explore large amounts of data to extract meaningful information. One such tool is interactive visualization. The amount of data that can be simultaneously visualized on a computer display is proportional to the display’s resolution. While computer systems in general have seen a remarkable increase in performance the last decades, display resolution has not evolved at the same rate. Increased resolution can be provided by tiling several displays in a grid. A system comprised of multiple displays tiled in such a grid is referred to as a display wall. Display walls provide orders of magnitude more resolution than typical desktop displays, and can provide insight into problems not possible to visualize on desktop displays. However, their distributed and parallel architecture creates several challenges for designing systems that can support interactive visualization. One challenge is compatibility issues with existing software designed for personal desktop computers. Another set of challenges include identifying characteristics of visualization systems that can: (i) Maintain synchronous state and display-output when executed over multiple display nodes; (ii) scale to multiple display nodes without being limited by shared interconnect bottlenecks; (iii) utilize additional computational resources such as desktop computers, clusters and supercomputers for workload distribution; and (iv) use data from local and remote compute- and data-resources with interactive performance. This dissertation presents Network Accessible Compute (NAC) resources and Network Accessible Display (NAD) resources for interactive visualization of data on displays ranging from laptops to high-resolution tiled display walls. A NAD is a display having functionality that enables usage over a network connection. A NAC is a computational resource that can produce content for network accessible displays. A system consisting of NACs and NADs is either push-based (NACs provide NADs with content) or pull-based (NADs request content from NACs). To attack the compatibility challenge, a push-based system was developed. The system enables several simultaneous users to mirror multiple regions from the desktop of their computers (NACs) onto nearby NADs (among others a 22 megapixel display wall) without requiring usage of separate DVI/VGA cables, permanent installation of third party software or opening firewall ports. The system has lower performance than that of a DVI/VGA cable approach, but increases flexibility such as the possibility to share network accessible displays from multiple computers. At a resolution of 800 by 600 pixels, the system can mirror dynamic content between a NAC and a NAD at 38.6 frames per second (FPS). At 1600x1200 pixels, the refresh rate is 12.85 FPS. The bottleneck of the system is frame buffer capturing and encoding/decoding of pixels. These two functional parts are executed in sequence, limiting the usage of additional CPU cores. By pipelining and executing these parts on separate CPU cores, higher frame rates can be expected and by a factor of two in the best case. To attack all presented challenges, a pull-based system, WallScope, was developed. WallScope enables interactive visualization of local and remote data sets on high-resolution tiled display walls. The WallScope architecture comprises a compute-side and a display-side. The compute-side comprises a set of static and dynamic NACs. Static NACs are considered permanent to the system once added. This type of NAC typically has strict underlying security and access policies. Examples of such NACs are clusters, grids and supercomputers. Dynamic NACs are compute resources that can register on-the-fly to become compute nodes in the system. Examples of this type of NAC are laptops and desktop computers. The display-side comprises of a set of NADs and a data set containing data customized for the particular application domain of the NADs. NADs are based on a sort-first rendering approach where a visualization client is executed on each display-node. The state of these visualization clients is provided by a separate state server, enabling central control of load and refresh-rate. Based on the state received from the state server, the visualization clients request content from the data set. The data set is live in that it translates these requests into compute messages and forwards them to available NACs. Results of the computations are returned to the NADs for the final rendering. The live data set is close to the NADs, both in terms of bandwidth and latency, to enable interactive visualization. WallScope can visualize the Earth, gigapixel images, and other data available through the live data set. When visualizing the Earth on a 28-node display wall by combining the Blue Marble data set with the Landsat data set using a set of static NACs, the bottleneck of WallScope is the computation involved in combining the data sets. However, the time used to combine data sets on the NACs decreases by a factor of 23 when going from 1 to 26 compute nodes. The display-side can decode 414.2 megapixels of images per second (19 frames per second) when visualizing the Earth. The decoding process is multi-threaded and higher frame rates are expected using multi-core CPUs. WallScope can rasterize a 350-page PDF document into 550 megapixels of image-tiles and display these image-tiles on a 28-node display wall in 74.66 seconds (PNG) and 20.66 seconds (JPG) using a single quad-core desktop computer as a dynamic NAC. This time is reduced to 4.20 seconds (PNG) and 2.40 seconds (JPG) using 28 quad-core NACs. This shows that the application output from personal desktop computers can be decoupled from the resolution of the local desktop and display for usage on high-resolution tiled display walls. It also shows that the performance can be increased by adding computational resources giving a resulting speedup of 17.77 (PNG) and 8.59 (JPG) using 28 compute nodes. Three principles are formulated based on the concepts and systems researched and developed: (i) Establishing the end-to-end principle through customization, is a principle stating that the setup and interaction between a display-side and a compute-side in a visualization context can be performed by customizing one or both sides; (ii) Personal Computer (PC) – Personal Compute Resource (PCR) duality states that a user’s computer is both a PC and a PCR, implying that desktop applications can be utilized locally using attached interaction devices and display(s), or remotely by other visualization systems for domain specific production of data based on a user’s personal desktop install; and (iii) domain specific best-effort synchronization stating that for distributed visualization systems running on tiled display walls, state handling can be performed using a best-effort synchronization approach, where visualization clients eventually will get the correct state after a given period of time. Compared to state-of-the-art systems presented in the literature, the contributions of this dissertation enable utilization of a broader range of compute resources from a display wall, while at the same time providing better control over where to provide functionality and where to distribute workload between compute-nodes and display-nodes in a visualization context

Virtual Worlds and Conservational Channel Evolution and Pollutant Transport Systems (Concepts)

Many models exist that predict channel morphology. Channel morphology is defined as the change in geometric parameters of a river. Channel morphology is affected by many factors. Some of these factors are caused either by man or by nature. To combat the adverse effects that man and nature may cause to a water system, scientists and engineers develop stream rehabilitation plans. Stream rehabilitation as defined by Shields et al., states that restoration is the return from a degraded ecosystem back to a close approximation of its remaining natural potential [Shields et al., 2003]. Engineers construct plans that will restore streams back to their natural state by using techniques such as field investigation, analytical models, or numerical models. Each of these techniques is applied to projects based on specified criteria, objectives, and the expertise of the individuals devising the plan. The utilization of analytical and numerical models can be difficult, for many reasons, one of which is the intuitiveness of the modeling process. Many numerical models exist in the field of hydraulic engineering, fluvial geomorphology, landscape architecture, and stream ecology that evaluate and formulate stream rehabilitation plans. This dissertation will explore, in the field of Hydroscience , the creation of models that are not only accurate but also span the different disciplines. The goal of this dissertation is to transform a discrete numerical model (CONCEPTS) into a realistic 3D environment using open source game engines, while at the same time, conveying at least the equivalent information that was presented in the 1D numerical model

Scalable exploration of 3D massive models

Programa Oficial de Doutoramento en Tecnoloxías da Información e as Comunicacións. 5032V01[Resumo] Esta tese presenta unha serie técnicas escalables que avanzan o estado da arte da creación e exploración de grandes modelos tridimensionaies. No ámbito da xeración destes modelos, preséntanse métodos para mellorar a adquisición e procesado de escenas reais, grazas a unha implementación eficiente dun sistema out- of- core de xestión de nubes de puntos, e unha nova metodoloxía escalable de fusión de datos de xeometría e cor para adquisicións con oclusións. No ámbito da visualización de grandes conxuntos de datos, que é o núcleo principal desta tese, preséntanse dous novos métodos. O primeiro é unha técnica adaptabile out-of-core que aproveita o hardware de rasterización da GPU e as occlusion queries para crear lotes coherentes de traballo, que serán procesados por kernels de trazado de raios codificados en shaders, permitindo out-of-core ray-tracing con sombreado e iluminación global. O segundo é un método de compresión agresivo que aproveita a redundancia xeométrica que se adoita atopar en grandes modelos 3D para comprimir os datos de forma que caiban, nun formato totalmente renderizable, na memoria da GPU. O método está deseñado para representacións voxelizadas de escenas 3D, que son amplamente utilizadas para diversos cálculos como para acelerar as consultas de visibilidade na GPU. A compresión lógrase fusionando subárbores idénticas a través dunha transformación de similitude, e aproveitando a distribución non homoxénea de referencias a nodos compartidos para almacenar punteiros aos nodos fillo, e utilizando unha codificación de bits variable. A capacidade e o rendemento de todos os métodos avalíanse utilizando diversos casos de uso do mundo real de diversos ámbitos e sectores, incluídos o patrimonio cultural, a enxeñería e os videoxogos.[Resumen] En esta tesis se presentan una serie técnicas escalables que avanzan el estado del arte de la creación y exploración de grandes modelos tridimensionales. En el ámbito de la generación de estos modelos, se presentan métodos para mejorar la adquisición y procesado de escenas reales, gracias a una implementación eficiente de un sistema out-of-core de gestión de nubes de puntos, y una nueva metodología escalable de fusión de datos de geometría y color para adquisiciones con oclusiones. Para la visualización de grandes conjuntos de datos, que constituye el núcleo principal de esta tesis, se presentan dos nuevos métodos. El primero de ellos es una técnica adaptable out-of-core que aprovecha el hardware de rasterización de la GPU y las occlusion queries, para crear lotes coherentes de trabajo, que serán procesados por kernels de trazado de rayos codificados en shaders, permitiendo renders out-of-core avanzados con sombreado e iluminación global. El segundo es un método de compresión agresivo, que aprovecha la redundancia geométrica que se suele encontrar en grandes modelos 3D para comprimir los datos de forma que quepan, en un formato totalmente renderizable, en la memoria de la GPU. El método está diseñado para representaciones voxelizadas de escenas 3D, que son ampliamente utilizadas para diversos cálculos como la aceleración las consultas de visibilidad en la GPU o el trazado de sombras. La compresión se logra fusionando subárboles idénticos a través de una transformación de similitud, y aprovechando la distribución no homogénea de referencias a nodos compartidos para almacenar punteros a los nodos hijo, utilizando una codificación de bits variable. La capacidad y el rendimiento de todos los métodos se evalúan utilizando diversos casos de uso del mundo real de diversos ámbitos y sectores, incluidos el patrimonio cultural, la ingeniería y los videojuegos.[Abstract] This thesis introduces scalable techniques that advance the state-of-the-art in massive model creation and exploration. Concerning model creation, we present methods for improving reality-based scene acquisition and processing, introducing an efficient implementation of scalable out-of-core point clouds and a data-fusion approach for creating detailed colored models from cluttered scene acquisitions. The core of this thesis concerns enabling technology for the exploration of general large datasets. Two novel solutions are introduced. The first is an adaptive out-of-core technique exploiting the GPU rasterization pipeline and hardware occlusion queries in order to create coherent batches of work for localized shader-based ray tracing kernels, opening the door to out-of-core ray tracing with shadowing and global illumination. The second is an aggressive compression method that exploits redundancy in large models to compress data so that it fits, in fully renderable format, in GPU memory. The method is targeted to voxelized representations of 3D scenes, which are widely used to accelerate visibility queries on the GPU. Compression is achieved by merging subtrees that are identical through a similarity transform and by exploiting the skewed distribution of references to shared nodes to store child pointers using a variable bitrate encoding The capability and performance of all methods are evaluated on many very massive real-world scenes from several domains, including cultural heritage, engineering, and gaming

Manipulação interativa de cenas fotorealistas usando path tracing

Rendering pleasing photorealistic images requires both a high-quality renderer and wellcrafted scenes. While rendering algorithms and systems have made some impressive progress over the last two decades, creating nice scenes still remains highly dependent of the artistic skills of the modeler. As a result, researchers tend to rely on a small number of existing good-looking scenes to test their algorithms. While creating new scenes from scratch is difficult for non-artists, editing existing scenes to achieve new and desired results is a task at the reach of the average graphics user. We present a system that allows users with no special artistic skills to create new scenes by modifying existing ones through a simple user interface. Enabled by modern hardware and software advancements, we render the scenes photorealistically using path tracing and provide instant feedback on the user modifications. The quality of the images generated by our system is comparable to established offline renderers, such as PBRT, while still maintaining interactive performance. Our system should stimulate the creation of new scene datasets, and allow anyone to customize existing scenes with shapes and materials according to his/her specific needs or desires. The easy customization of scenes and the high-quality renderings produced by our system may also stimulate other professionals, such as designers, scenographers, architects, decorators, etc. to make more intense use of computer generated imaging in their daily tasks.Renderizar imagens fotorealistas agradáveis requer tanto um renderizador de alta qualidade quanto cenas bem feitas. Enquanto sistemas e algoritmos de rendering tiveram progressos impressionantes nas últimas duas décadas, a criação de cenas interessantes ainda é altamente dependente nas habilidades artísticas do modelador. Como resultado, pesquisadores tendem a usar uma porção pequena de boas cenas já existentes para testar seus algoritmos. Embora a criação de cenas do zero seja difícil para não-artistas, editar cenas existentes para conseguir novos resultados é uma tarefa ao alcance do usuário médio de computação gráfica. Nós apresentamos um sistema que permite usuários sem habilidades artísticas especiais a criar novas cenas modificando cenas existentes através de uma interface simples. Baseado em avanços recentes em hardware e software nós renderizamos as cenas fotorealisticamente usando path tracing, provendo feedback instantâneo nas modificações do usuário. A qualidade das imagens geradas pelo nosso sistema é comparável a renderizadores offline estabelecidos, como o PBRT, enquanto ainda mantendo performance interativa. Nosso sistema deve estimular a criação de novos datasets de cenas, e permitir a qualquer um a customizar cenas existentes com formas e materiais de acordo com sua necessidade ou desejo. A fácil customização de cenas e as imagens de alta qualidade produzidas pelo nosso sistema também podem estimular outros profissionais, como designers, cenógrafos, arquitetus, decoradores, etc. a fazer uso mais intenso de imagens geradas por computador em suas tarefas diárias