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Workshop on Mathematical Foundations of scientific Visualization, computer Graphics, and Massive Data Exploration, 2004

作者： Bremer, Peer-Timo Pascucci, Valerio Hamann, Bernd Department of Computer Science University of Illinois Urbana-Champaign United States Center for Applied Scientific Computing Lawrence Livermore National Laboratory United States Institute for Data Analysis and Visualization Department of Computer Science University of California Davis United States

ISBN: (纸本)9783642543005

We present a highly adaptive hierarchical representation of the topology of functions defined over two-manifold domains. Guided by the theory of Morse–Smale complexes, we encode dependencies between cancellations of critical points using two independent structures: a traditional mesh hierarchy to store connectivity information and a new structure called cancellation trees to encode the configuration of critical points. Cancellation trees provide a powerful method to increase adaptivity while using a simple, easy-to-implement data structure. The resulting hierarchy is significantly more flexible than the one previously reported (IEEE Trans. Vis. Comput. Graph. 10(4):385–396, 2004). In particular, the resulting hierarchy is guaranteed to be of logarithmic height. © 2009 Springer-Verlag Berlin Heidelberg.

关键词： Trees (mathematics)

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Testing GPU Numerics: Finding Numerical Differences Between NVIDIA and AMD GPUs

Testing GPU Numerics: Finding Numerical Differences Between ...

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2024 Workshops of the International Conference for High Performance computing, Networking, Storage and Analysis, SC Workshops 2024

作者： Zahid, Anwar Hossain Laguna, Ignacio Le, Wei Iowa State University Department of Computer Science AmesIA United States Lawrence Livermore National Laboratory Center for Applied Scientific Computing LivermoreCA United States

ISBN: (纸本)9798350355543

As scientific codes are ported between GPU platforms, continuous testing is required to ensure numerical robustness and identify potential numerical differences between platforms. Compiler-induced numerical differences can occur when a program is compiled and run on different GPUs and compilers, and the numerical outcomes are different for the same input. We present a study of compiler-induced numerical differences between NVIDIA and AMD GPUs, two widely used GPUs in HPC clusters. Our approach uses a random program generator (Varity) to generate thousands of short numerical tests in CUDA and HIP, and their inputs;then, we use differential testing to check if the program produced a numerical inconsistency when run on NVIDIA and AMD GPUs, using the same compiler optimization level. We also use the AMD's HIPIFY tool to convert CUDA tests into HIP tests and test if there are numerical inconsistencies induced by HIPIFY. In our study, we generated more than 600,000 tests and found subtle numerical differences occurring between the two classes of GPUs. We found that some of the differences come from (1) math library calls, (2) differences in floating-point precision (FP64 versus FP32), and (3) converting code to HIP with HIPIFY. © 2024 IEEE.

关键词： CUDA Differential testing floating-point HIP random program generation

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Query-driven Multiscale Data Postprocessing in Computational Fluid Dynamics

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Procedia computer science 2011年 4卷 332-341页

作者： Atanas Atanasov Tobias Weinzierl Scientific Computing in Computer Science Institut für Informatik Technische Universität München

Massively parallel computational uid dynamics codes that have to stream solution data to a visualisation or postprocessing component in each time step often are IO-bounded. This is especially cumbersome if the succeeding components require the simulation data only in a coarse resolution or only in specific subregions. We suggest to replace the streaming data approach found in many applications with a query-driven communication paradigm where the postprocessing components explicitly inform the uid solver which data they need in which resolution in which subregions. Two case studies reveal that such a data exchange paradigm reduces the memory footprint of the exchanged data as well as the latency of the data delivery, and that the approach scales. In particular geometric multigrid solvers based upon a non-overlapping domain decomposition can answer such queries efficiently.

关键词： Computational steering Computational uid mechanics Multiscale methods Domain decomposition, Problem solving environments

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A Three-Choice Minority Game Model with Homogeneous Agent Preferences for Resource Allocation

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Procedia computer science 2018年 140卷 56-63页

作者： Catalina A. Montes Adrian Roy L. Valdez Scientific Computing Laboratory Department of Computer Science University of the Philippines-Diliman Quezon City 1101 Philippines

Microgrids have a promising potential to provide off-grid energy access for rural communities. With the growing interest on microgrids and energy access, there has been a renewed focus on developing demand management schemes appropriate for simple microgrids. One basic demand management concern is the problem of shaping consumer demand profiles such that peaks and troughs can be minimized. This problem can be viewed as a simplified resource allocation problem where each resource choice can only be chosen by a fixed number of agents. This study models the described allocation problem as a three-choice minority game where the resources available to the agents map to energy time-of-use windows. Agents were defined to have a homogeneous preference over these available choices of time windows. Different cost functions were likewise simulated in the game. The specific cost functions used in the simulations were chosen to determine whether agents can be influenced to self-organize such that the total number of agents per time window falls within a defined capacity. Results show that some cost functions successfully maintain agent numbers within the defined capacity. Nevertheless, results also indicate that agent gains may suffer when the capacity per choice is met.

关键词： minority games game theory

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Approximating anatomical brain connectivity with diffusion tensor MRI using kernel-based diffusion simulations

Approximating anatomical brain connectivity with diffusion t...

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19th International Conference on Information Processing in Medical Imaging, IPMI 2005

作者： Zhang, Jun Kang, Ning Rose, Stephen E. Laboratory for High Performance Scientific Computing and Computer Simulation Department of Computer Science University of Kentucky Lexington KY 40506-0046 United States Centre for Magnetic Resonance University of Queensland Brisbane QLD 4072 Australia

We present a new technique for noninvasively tracing brain white matter fiber tracts using diffusion tensor magnetic resonance imaging (DT-MRI). This technique is based on performing diffusion simulations over a series of overlapping three dimensional diffusion kernels that cover only a small portion of the human brain volume and are geometrically centered upon selected starting voxels where a seed is placed. Synthetic and real DT-MRI data are employed to demonstrate the tracking scheme. It is shown that the synthetic tracts can be accurately replicated, while several major white matter fiber pathways in the human brain can be reproduced noninvasively as well. The primary advantages of the algorithm lie in the handling of fiber branching and crossing and its seamless adaptation to the platform established by new imaging techniques, such as high angular, q-space, or generalized diffusion tensor imaging. © Springer-Verlag Berlin Heidelberg 2005.

关键词： Brain

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WebCT – OpenSource web-based GUI for real-time X-ray simulation

Tomography of Materials and Structures

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Tomography of Materials and Structures 2025年 8卷

作者： Iwan T. Mitchell Jean Michel Létang Llion Marc Evans Franck P. Vidal School of Computer Science & Electronic Engineering Bangor University Bangor LL57 1UT UK INSA-Lyon Université Claude Bernard LYON 1 UJM-Saint Etienne CNRS Inserm CREATIS UMR 5220 U1294 Lyon F-69373 France Independent Researcher UK Scientific Computing Department Science Technology Facilities Council UK Research and Innovation UK

Scan planning for X-ray CT systems can be difficult due to the large number of elements affecting scan quality. The use of X-ray simulation can answer feasibility questions, however existing methods are focused on experts who are familiar with XCT and programming knowledge. WebCT is a user-centric application for performing virtual XCT scans with the validated X-ray simulator gVirtualXray. Focused on accessibility, the interface allows changing all scanning parameters; from tube characteristics to detector energy response, while allowing full-scale simulation and reconstruction in minutes. WebCT is available as a free, open-source application, giving full control over a virtual lab-CT or synchrotron system. Configurations can be saved, shared, or even imported from many popular XCT dataset formats. We demonstrate in this paper the use of WebCT as a scan planning tool, using a simple CAD mockup to select filtration based on transmission before scanning.

关键词： X-ray Simulation Computational modelling X-ray computed tomography (XCT) Non-destructive testing (NDT) Synchrotron tomography User Interface (UI) Experimental Planning

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Rendering artistic light patterns

Rendering artistic light patterns

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Expressive 2015 - Joint Symposium of Computational Aesthetics, CAe 2015, Non-Photorealistic Animation and Rendering, NPAR 2015 and Sketch-Based Interfaces and Modeling, SBIM 2015

作者： Ji, L. Gooch, A. Gammon, L. Wyvill, B. Department of Computer Science University of Victoria Canada Department of Visual Arts University of Victoria Canada Scientific Computing and Imaging University of Utah United States

ISBN: (纸本)9783905674897

By combining knowledge from computer graphics and visual arts, we have built a projection installation based on a novel sketch-based shape pattern rendering method. Our novel rendering method is guided by an artist’s drawing, and generates shape patterns resembling the input image, creating animation with an organic appearance. We have also applied the proposed method to render foliage shadow effects for virtual scenes. The major contribution of method is its ability to automatically render richly detailed, animated lighting patterns from an approximate lighting plan drawing. In our research team, professional artists and computer graphics researchers work together to develop our rendering method and the artistic rendering projects side by side. This interdisciplinary approach helps us to design and evolve our method for creating aesthetic work with computer graphics technologies. © The Eurographics Association 2015.

关键词： Animation

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Solving the Exterior Bernoulli Problem Using the Shape Derivative Approach 1

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International Conference on Mathematics and computing, ICMC 2013

作者： Bacani, Jerico B. Peichl, Gunther Department of Mathematics and Computer Science College of Science University of the Philippines Baguio Governor Pack Road 2600 Baguio Philippines Institute for Mathematics and Scientific Computing University of Graz Heinrichstrasse 36 8010 Graz Austria

ISBN: (数字)9788132219521

ISBN: (纸本)9788132219514

In this paper, we are interested in solving the exterior Bernoulli free boundary problem by minimizing a particular cost functional J over a class of admissible domains subject to two well-posed PDE constraints: a Dirichlet boundary value problem and a Neumann boundary value problem. The main result for this paper is the thorough computation of the first-order shape derivative of J using the shape derivatives of the state variables. At first, the material derivatives of the states are rigorously justified. Then the equation and the boundary conditions satisfied by the corresponding shape derivatives are derived directly from the definition of the shape derivative and the variational equation for thematerial derivative. It becomes apparent that the analysis of the shape derivatives of the states requires more regular domains. Finally, it is noted that the shape gradient agrees with the structure predicted by the Hadamard structure theorem. © Springer India 2014.

关键词： Boundary value problems

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Invariant snakes and initialization of deformable models

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International Journal of Image and Graphics 2004年第3期4卷 363-384页

作者： Giraldi, Gilson A. Oliveira, Antonio A. F. Department of Computer Science National Laboratory for Scientific Computing Av. Getúlio Vargas Petrópolis Rio de JaneiroZIP 25651-075 Brazil Computer Graphics Laboratory Federal University of Rio de Janeiro Ilha do Fundão Rio de JaneiroZIP 21945-970 Brazil

Parametric snake models are deformable models very useful for boundary extraction and tracking. Despite their abilities, the non-invariance of the internal energy under affine transformations and the non-convexity of the model energy are known limitations for most of these methods. The former has been addressed in the context of active shape models. The latter can be addressed through Dual contour approaches as well as an automatic procedure to initialize the model closer to the desired boundary. In this paper we first analyze the effects of reparameterization for invariant snake models through the Lie Group Theory. In the second part of this work, we present our Dual-T-Snakes model and a methodology based on the T-Snakes framework to initialize deformable models. In the experimental results we explore and combine these techniques for segmentation of medical images. © 2004 World scientific Publishing Company.

关键词： Lie groups

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Grab and Go: Leveraging computer Vision for Intelligent Shopping 11

Grab and Go: Leveraging Computer Vision for Intelligent Shop...

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11th IEEE International Conference on Intelligent computing and Information Systems, ICICIS 2023

作者： Awad, George Fawzy, Joseph Yacoub, Sandra Abdelgalil, Mahmoud Khaled, Nada Bernaba, Jan Mohamed, Omar Hindy, Hanan Ain Shams University Faculty of Computer and Information Sciences Artificial Intelligence Cairo Egypt Ain Shams University Faculty of Computer and Information Sciences Scientific Computing Cairo Egypt Ain Shams University Faculty of Computer and Information Science Computer Sciences Cairo Egypt

ISBN: (纸本)9798350322101

In an effort to address the challenges posed by long queues and slow payment processes in shopping, new technologies like Amazon's "Just Walk Out"have emerged to enable checkout-free purchases. computer vision methods, specifically the application of On-Shelf Availability (OSA) monitoring, have been highlighted as crucial for efficient inventory management in grocery stores, using semi-supervised learning and YOLO deep learning architecture. However, the high cost associated with implementing such comprehensive smart market solutions, including the need for RFID sensors on every item, may hinder adoption in developing countries. This paper aims to provide a more affordable alternative by leveraging computer vision techniques, replacing sensors with cameras, and utilizing deep learning models. The proposed approach involved training YOLO V5 and various versions of YOLO V8 models, incorporating annotations, data augmentations, and exploring different techniques. The achieved results demonstrated a mean Average Precision (mAP) of 78.3%, precision of 64.2%, and recall of 61.4% using YOLO V8 with augmentations such as Mosaic, Horizontal Flip, Blur, etc. While the results were considered acceptable even with limited access to natural images, the performance is expected to improve further with increased access to a wider range of training images, especially natural ones. © 2023 IEEE.

关键词： computer vision

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