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29th International Supercomputing Conference, ISC 2014

作者： Scogland, Thomas R. W. Feng, Wu-Chun Rountree, Barry De Supinski, Bronis R. Department of Computer Science Virginia Tech Blacksburg VA 24060 United States Center for Applied Scientific Computing Lawrence Livermore National Laboratory Livermore CA 94551 United States

ISBN: (纸本)9783319075174

The popularity of heterogeneous computing continues to increase rapidly due to the high peak performance, favorable energy efficiency, and comparatively low cost of accelerators. However, heterogeneous programming models still lack the flexibility of their CPU-only counterparts. Accelerated OpenMP models, including OpenMP 4.0 and OpenACC, ease the migration of code from CPUs to GPUs but lack much of OpenMP's flexibility: OpenMP applications can run on any number of CPUs without extra user effort, but GPU implementations do not offer similar adaptive worksharing across GPUs in a node, nor do they employ a mix of CPUs and GPUs. To address these shortcomings, we present CoreTSAR, our library for scheduling cores via a task-size adapting runtime system by supporting worksharing of loop nests across arbitrary heterogeneous resources. Beyond scheduling the computational load across devices, CoreTSAR includes a memory-management system that operates based on task association, enabling the runtime to dynamically manage memory movement and task granularity. Our evaluation shows that CoreTSAR can provide nearly linear scaling to four GPUs and all cores in a node without modifying the code within the parallel region. Furthermore, CoreTSAR provides portable performance across a variety of system configurations. © Springer International Publishing Switzerland 2014.

关键词： Program processors

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Automatically adapting programs for mixed-precision floating-point computation 13

Automatically adapting programs for mixed-precision floating...

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27th ACM International Conference on Supercomputing, ICS 2013

作者： Lam, Michael O. Hollingsworth, Jeffrey K. De Supinski, Bronis R. Legendre, Matthew P. Dept. of Computer Science University of Maryland College Park MD United States Center for Applied Scientific Computing Lawrence Livermore National Laboratory Livermore CA United States

ISBN: (纸本)9781450321303

As scientific computation continues to scale, efficient use of floating-point arithmetic processors is critical. Lower precision allows streaming architectures to perform more operations per second and can reduce memory bandwidth pressure on all architectures. However, using a precision that is too low for a given algorithm and data set leads to inaccurate results. In this paper, we present a framework that uses binary instrumentation and modification to build mixed-precision configurations of existing binaries that were originally developed to use only double-precision. This framework allows developers to explore mixed-precision configurations without modifying their source code, and it permits autotuning of floating-point precision. We include a simple search algorithm to automate identification of code regions that can use lower precision. Our results for several benchmarks show that our framework is effective and incurs low overhead (less than 10X in most cases). In addition, we demonstrate that our tool can replicate manual conversions and suggest further optimization;in one case, we achieve a speedup of 2X. © 2013 ACM.

关键词： Digital arithmetic

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Lossless entropy based compression for medical images

Lossless entropy based compression for medical images

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International Symposia on Imaging and Signal Processing in Health Care and Technology, ISPHT 2012

作者： Clemons, Tyler Yin, Jian Department of Computer Science and Engineering Ohio State University Columbus OH United States Data Intensive Scientific Computing Pacific Northwest National Laboratory Richland WA United States

ISBN: (纸本)9780889869202

High Resolution Medical Images provide a useful visual and analytic tool to medical professionals. These images often require substantial disk space and thus may provide bottlenecks in I/O access and network transmission, and create a challenge for disk storage capacity. These problems can be mitigated by using compression algorithms that not only reduce the storage requirements of the data files, but can do so quickly as to meet real time workloads. We present a lossless entropy based compression scheme that achieves both of these goals for medical image data. We demonstrate the effectiveness of our lossless algorithm using a medical image dataset and compare its performance with other lossless compression techniques. Our method provides competitive compression ratios without sacrificing real-time performance.

关键词： Medical image processing

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Managing performance analysis with dynamic statistical projection pursuit

Managing performance analysis with dynamic statistical proje...

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1999 ACM/IEEE Conference on Supercomputing, SC 1999

作者： Vetter, Jeffrey S. Reed, Daniel A. Center for Applied Scientific Computing Lawrence Livermore National Laboratory LivermoreCA94550 United States Department of Computer Science University of Illinois UrbanaIL61801 United States

ISBN: (纸本)1581130910

computer systems and applications are growing more complex. Consequently, performance analysis has become more difficult due to the complex, transient interrelationships among runtime components. To diagnose these types of performance issues, developers must use detailed instrumentation to capture a large number of performance metrics. Unfortunately, this instrumentation may actually influence the performance analysis, leading the developer to an ambiguous conclusion. In this paper, we introduce a technique for focussing a performance analysis on interesting performance metrics. This technique, called dynamic statistical projection pursuit, identifies interesting performance metrics that the monitoring system should capture across some number of processors. By reducing the number of performance metrics, projection pursuit can limit the impact of instrumentation on the performance of the target system and can reduce the volume of performance data. © 1999 IEEE.

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Application-level checkpointing for shared memory programs

Application-level checkpointing for shared memory programs

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作者： Bronevetsky, Greg Marques, Daniel Pingali, Keshav Szwed, Peter Schulz, Martin Department of Computer Science Cornell University Ithaca NY 14853 School of Electrical and Computer Engineering Cornell University Ithaca NY 14853 Center for Applied Scientific Computing Lawrence Livermore National Laboratory Livermore CA 94551

Trends in high-performance computing are making it necessary for long-running applications to tolerate hardware faults. The most commonly used approach is checkpoint and restart (CPR) - the state of the computation is saved periodically on disk, and when a failure occurs, the computation is restarted from the last saved state. At present, it is the responsibility of the programmer to instrument applications for CPR. Our group is investigating the use of compiler technology to instrument codes to make them self-checkpointing and self-restarting, thereby providing an automatic solution to the problem of making long-running scientific applications resilient to hardware faults. Our previous work focused on message-passing programs. In this paper, we describe such a system for shared-memory programs running on symmetric multiprocessors. This system has two components: (i) a pre-compiler for source-to-source modification of applications, and (ii) a runtime system that implements a protocol for coordinating CPR among the threads of the parallel application. For the sake of concreteness, we focus on a non-trivial subset of OpenMP that includes barriers and locks. One of the advantages of this approach is that the ability to tolerate faults becomes embedded within the application itself, so applications become self-checkpointing and self-restarting on any platform. We demonstrate this by showing that our transformed benchmarks can checkpoint and restart on three different platforms (Windows/x86, Linux/x86, and Tru64/Alpha). Our experiments show that the overhead introduced by this approach is usually quite small;they also suggest ways in which the current implementation can be tuned to reduced overheads further. Copyright 2004 ACM.

关键词： computer systems programming

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Feature Identification and Extraction in Function Fields

Feature Identification and Extraction in Function Fields

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9th Joint Eurographics/IEEE VGTC Symposium on Visualization, EuroVis 2007

作者： Anderson, John C. Gosink, Luke J. Duchaineau, Mark A. Joy, Kenneth I. Institute for Data Analysis and Visualization Department of Computer Science University of California Davis United States Center for Applied Scientific Computing Lawrence Livermore National Laboratory

ISBN: (纸本)9783905673456

We present interactive techniques for identifying and extracting features in function fields. Function fields map points in n-dimensional Euclidean space to 1-dimensional scalar functions. Visual feature identification is accomplished by interactively rendering scalar distance fields, constructed by applying a function-space distance metric over the function field. Combining visual exploration with feature extraction queries, formulated as a set of function-space constraints, facilitates quantitative analysis and annotation. Numerous application domains give rise to function fields. We present results for two-dimensional hyperspectral images, and a simulated time-varying, three-dimensional air quality dataset. © The Eurographics Association 2007.

关键词： Air quality

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Testing model transformation programs using metamorphic testing 26

Testing model transformation programs using metamorphic test...

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26th International Conference on Software Engineering and Knowledge Engineering, SEKE 2014

作者： Jiang, Mingyue Chen, Tsong Yueh Kuo, Fei-Ching Zhou, Zhi Quan Ding, Zuohua Department of Computer Science and Software Engineering Swinburne University of Technology HawthornVIC Australia School of Computer Science and Software Engineering University of Wollongong WollongongNSW Australia Laboratory of Scientific Computing and Software Engineering Zhejiang Sci-Tech University Hangzhou Zhejiang China

Model transformations are crucial for the success of Model Driven Engineering. Testing is a prevailing technique of verifying the correctness of model transformation programs. A major challenge in model transformation testing is the oracle problem, which refers to the difficulty or high cost in determining the correctness of the output models. Metamorphic Testing alleviates the oracle problem by making use of the relationships among the inputs and outputs of multiple executions of the target function. This paper investigates the effectiveness and feasibility of metamorphic testing in testing model transformation programs. Empirical results show that metamorphic testing is an effective testing method for model transformation programs. Copyright © 2014 by Knowledge Systems Institute Graduate School.

关键词： Metamorphic testing Model transformation Software quality Software testing Test oracle

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VIPACT: A visualization interface for analyzing calling context trees 3

VIPACT: A visualization interface for analyzing calling cont...

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3rd Workshop on Visual Performance Analysis, VPA 2016

作者： Nguyen, Huu Tan Wei, Lai Bhatele, Abhinav Gamblin, Todd Boehme, David Schulz, Martin Ma, Kwan-Liu Bremer, Peer-Timo Department of Computer Science University of California DavisCA95616 United States Department of Computer Science Rice University HoustonTX77251 United States Center for Applied Scientific Computing Lawrence Livermore National Laboratory LivermoreCA94551 United States

ISBN: (纸本)9781509052264

Profiling tools are indispensable for performance optimization of parallel codes. They allow users to understand where a code spends its time, and to focus optimization efforts on the most time consuming regions. However, two sources of complexity make them difficult to use on large-scale parallel applications. First, the code complexity of parallel applications is increasingly, and identifying the problematic regions in the code is difficult. Traditional profilers show either a flat view or a calling context tree view. Second, most tools average performance data across processes, losing per-process behavior. Diagnosing problems like load imbalance requires profiles from many processes, and manually analyzing profiles from hundreds or thousands of processes is infeasible. We introduce VIPACT, a visualization tool to identify different behaviors in multiple processes. VIPACT introduces "halo nodes" that concisely encode the distributions of runtimes from all processes, and a hybrid tree view that combines the advantages of calling context trees with those of flat profiles. We combine these with approaches such as ring charts, as well as the filtering and subselection of nodes, and we apply these techniques to a production multi-physics code. © 2016 IEEE.

关键词： Visualization

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Efficient Tree-based Parallel Algorithms for N-Body Simulations Using C++ Standard Parallelism

Efficient Tree-based Parallel Algorithms for N-Body Simulati...

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

作者： Cassell, Thomas Lane Deakin, Tom Alpay, Aksel Heuveline, Vincent Gadeschi, Gonzalo Brito University of Bristol School of Computer Science BristolBS8 1UB United Kingdom Heidelberg University Engineering Mathematics and Computing Lab Interdisciplinary Center for Scientific Computing Heidelberg Germany NVIDIA GPU Architecture Munich Germany

ISBN: (纸本)9798350355543

The Barnes-Hut approximation for N-body simulations reduces the time complexity of the naive all-pairs approach from O(N2) to O(N log N) by hierarchically aggregating nearby particles into single entities using a tree data structure. This inherently irregular algorithm poses substantial challenges for performance portable implementations on multi-core CPUs and GPUs. We introduce two portable fully-parallel Barnes-Hut implementation strategies that trade-off different levels of GPU support for performance: an unbalanced concurrent octree, and a balanced bounding volume hierarchy sorted by a Hilbert spacefilling curve. We implement these algorithms in portable ISO C++ using parallel algorithms and concurrency primitives like atomics. The results demonstrate competitive performance on a range of CPUs and GPUs. Additionally, they highlight the effectiveness of the par execution policy for highly concurrent irregular algorithms, outperforming par_unseq on CPUs and GPUs with Independent Thread Scheduling. © 2024 IEEE.

关键词： n/a

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Impacts of oxytactic microorganisms and viscous dissipation in Carreau nanoliquid featuring ferromagnetic nanoparticles

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Partial Differential Equations in Applied Mathematics 2025年 13卷

作者： Tabrez, Muhammad Hussain, I. Khan, W.A. Khan, S.U. Waqas, M. Rashid, Rzgar Farooq Anwar, M.I. Ammar, Mohamed Ben Zamri, Nurnadiah Abiyev, Ruzimurod Garalleh, Hakim AL Department of Mathematics Mohi-ud-Din Islamic University Nerian Sharif Azad Jammu and Kashmir 12010 Pakistan Department of Mathematics Namal University Mianwali 42250 Pakistan NUTECH School of Applied Sciences and Humanities National University of Technology Islamabad 44000 Pakistan Department of Computer Science and Mathematics Lebanese American University Beirut Lebanon Faculty of Informatics and Computing Universiti Sultan Zainal Abidin Besut Campus Terengganu Besut 22200 Malaysia Department of Medical Laboratory Science College of Science Knowledge University Erbil 44001 Iraq Department of Medical Laboratory Technique College of Medical Technology AL-Kitab University Kirkuk Iraq Department of Mathematics School of Sciences and Humanities Nazarbayev University Astana Kazakhstan Center for Scientific Research and Entrepreneurship Northern Border University Arar 73213 Saudi Arabia Department of Mathematics and its Teaching Methods in Primary Education Tashkent State Pedagogical University Tashkent Uzbekistan Department of Mathematical Science College of Engineering University of Business and Technology Jeddah 21361 Saudi Arabia

Owing to rapid progress in field of nanotechnology, various mathematical model has been proposed regarding the flow of nanofluids. Based on boosted thermal properties, multidisciplinary applications of such materials has been claimed in various engineering and industrial processes. In current work, a theoretical analysis is performed for bioconvective flow of Carreau fluid with applications of magnetic dipole. The significance of magnetic dipole are presented with interaction of ferrofluid. The applications of viscous dissipation have also been entertained. The flow is subject to applications of stretched surface. Similarity variables are used for making transformation to obtain set of nonlinear ODEs from set of PDEs. The numerical computation is also made by using of well-known numerical method termed as bvp4c. Influences of various non dimensional fluid parameters like Brownian motion, viscous dissipation, Curie temperature, Weissenberg number, motile difference parameter and bioconvection Paclet number are examined and expressed graphically. It is perceived that ferrofluid's concentration declines when Brownian diffusive variable is augmented while opposite characteristics are reported for Schmidt number. Current results conveying applications in the biofuels, better heat transport medium, fertilizers, catalysts, electronics, paints, semiconductors, speakers, drug delivery, fertilizers etc. © 2024 The Author(s)

关键词： Bioconvection Carreau fluid Ferromagnetic flow Magnetic dipole Viscous dissipation

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