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IEEE/LEOS International Conference on Optical MEMS

作者： Deng Jun Sajid Hussian Soham Saha Ching Eng Png Mankei Tsang Aaron J. Danner Department of Electrical and Computer Engineering National University of Singapore Singapore Agency for Science Institute of High Performance Computing Singapore

A microring resonator was fabricated in LiNbO 3 substrate by annealed proton exchange (APE) method. Measurement results show that thermal annealing is necessary to improve the performance of the channel waveguides. The measured extinction ratio is approximately 13dB. By making use of Cr film as electrodes, a tunability of 2 pm/V is obtained by applying 150V.

关键词： Optical ring resonators Lithium niobate Annealing Optical device fabrication Electrooptical waveguides

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Optimizing and Auto-Tuning Iterative Stencil Loops for GPUs with the In-Plane Method

Optimizing and Auto-Tuning Iterative Stencil Loops for GPUs ...

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International Symposium on Parallel and Distributed Processing (IPDPS)

作者： Wai Teng Tang Wen Jun Tan Ratna Krishnamoorthy Yi Wen Wong Shyh-Hao Kuo Rick Siow Mong Goh Stephen John Turner Weng-Fai Wong School of Computer Engineering Nanyang Technological University Singapore Department of Computer Science School of Computing National University of Singapore Singapore Institute of High Performance Computing Agency for Science Technology and Research Singapore

ISBN: (纸本)9781467360661

Stencils represent an important class of computations that are used in many scientific disciplines. Increasingly, many of the stencil computations in scientific applications are being offloaded to GPUs to improve running times. Since a large part of the simulation time is spent inside the stencil kernels, optimizing the kernel is therefore important in the context of achieving greater computation efficiencies and reducing simulation time. In this work, we proposed a novel in-plane method for stencil computations on GPUs and compared its performance with the conventional method implemented in the Nvidia SDK. We also implemented an auto-tuning framework for our method to select the optimal parameters for different GPU architectures. A performance model was developed for our proposed method, and is used to speed up the auto-tuning process. Our results show that a speedup of nearly 2× can be achieved compared to Nvidia's implementation.

关键词： Kernel Instruction sets Loading Graphics processing units computer architecture Bandwidth Registers

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Cost Optimization for Scientific Workflow Execution on Cloud computing

Cost Optimization for Scientific Workflow Execution on Cloud...

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International Conference on Parallel and Distributed Systems (ICPADS)

作者： Tanyaporn Tirapat Orachun Udomkasemsub Xiaorong Li Tiranee Achalakul Computer Engineering Department King Mongkut's University of Technology Bangkok Thailand Agency for Science Technology and Research (A*STAR) Institute of High Performance Computing (IHPC) Singapore

Scientific workflow applications generally require various levels of computing power over the course of execution. The applications then often take advantage of Cloud computing due to its cost-effective, pay-as-you-go pricing model. However, the scientific workflow executions must be planned wisely in order to minimize total cost of the resource usage. In addition, lateness of completing some workflows may result in high penalty cost. In this paper, the scheduling algorithm based on GA and PSO is proposed for optimizing the workflow execution. The experiment to evaluate the scheduling efficiency is performed on the simple workflow engine developed by the authors. The result is then compared to the existing algorithms including HEFT, GA, PSO, and PSO-SA. The result shows that the proposed GAPSO algorithm has a good potential to give the minimum cost when execution time is restricted.

关键词： Sociology Statistics Genetic algorithms Algorithm design and analysis Scheduling algorithms Engines Schedules

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Analyzing the Robustness of Scheduling Algorithms Using Divisible Load Theory on Heterogeneous Systems

Analyzing the Robustness of Scheduling Algorithms Using Divi...

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International Symposium on Parallel and Distributed computing

作者： Mahadevan Balasubramaniam Ioana Banicescu Florina M. Ciorba Department of Computer Science and Engineering Mississippi State University Mississippi USA Center for Information Services and High Performance Computing (ZIH) Technische Universität Dresden Dresden Germany

ISBN: (纸本)9781479907342

Arbitrarily divisible workloads are present in a large class of scientific applications, such as N-body simulations, Monte Carlo simulations, CFD applications, and others. Divisible load theory (DLT) provides a tractable approach to the scheduling of arbitrarily divisible workloads. high performance parallel and distributed systems may operate in an unreliable environment, and a robust system is expected to deliver a certain level of performance when operating in such an environment. To the best of our knowledge, this is the first work to study and analyze the robustness of DLT algorithms. Using simulations, a study of the resiliency of DLT to variations in certain system features, such as the network latency, the network bandwidth, and the processor availability on a single level tree topology is presented. The simulation results demonstrate the robustness of the DLT algorithms under certain application and system characteristics.

关键词： Robustness Processor scheduling Equations Schedules Bandwidth Computational modeling Runtime

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Evaluating the Flexibility of Dynamic Loop Scheduling on Heterogeneous Systems in the Presence of Fluctuating Load Using SimGrid

Evaluating the Flexibility of Dynamic Loop Scheduling on Het...

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IEEE International Symposium on Parallel and Distributed Processing Workshops and Phd Forum (IPDPSW)

作者： Nitin Sukhija Ioana Banicescu Srishti Srivastava Florina M. Ciorba Department of Computer Science and Engineering Mississippi State University Mississippi State MS USA Technische Universität Dresden Center for Information Services and High Performance Computing Dresden Germany

ISBN: (纸本)9781479913725

Scientific applications running on heterogeneous computing systems, which often have unpredictable behavior, enhance their performance by employing loop scheduling techniques as methods to avoid load imbalance through an optimized assignment of their parallel loops. With current computing platforms facilitating petascale performance and promising exascale performance towards the end of the present decade, efficient and robust algorithms are required to guarantee optimal performance of parallel applications in the presence of unpredictable perturbations. A number of dynamic loop scheduling (DLS) methods based on probabilistic analyses have been developed to achieve the desired robust performance. In earlier work, two metrics (flexibility and resilience) have been formulated to quantify the robustness of various DLS methods in heterogeneous computing systems with uncertainties. In this work, to ensure robust performance of the scientific applications on current (petascale) and future(exascale) high performance computing systems, a simulation model was designed and integrated into the SimGrid simulation toolkit, thus enabling a comprehensive study of the robustness of the DLS methods which uses results of experimental cases with various combinations of number of processors, problem sizes, and scheduling methods. The DLS methods have been implemented into the simulation model and analyzed for the purpose of exploring their flexibility (robustness against unpredictable variations in the system load), when involved in a range of case scenarios comprised of various distributions characterizing loop iteration execution times and system availability. The simulation results reported are used to compare the robustness of the DLS methods under the various environments considered, using the flexibility metric.

关键词： Robustness Program processors Computational modeling Availability Processor scheduling Load modeling Measurement

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Leveraging performance Counters and Execution Logs to Diagnose Memory-Related performance Issues

Leveraging Performance Counters and Execution Logs to Diagno...

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International Conference on Software Maintenance (ICSM)

作者： Mark D. Syer Zhen Ming Jiang Meiyappan Nagappan Ahmed E. Hassan Mohamed Nasser Parminder Flora Software Analysis and Intelligence Lab Queen's University Canada Department of Electrical Engineering & Computer Science York University Canada Performance Engineering School of Computing BlackBerry Canada

Load tests ensure that software systems are able to perform under the expected workloads. The current state of load test analysis requires significant manual review of performance counters and execution logs, and a high degree of system-specific expertise. In particular, memory-related issues (e.g., memory leaks or spikes), which may degrade performance and cause crashes, are difficult to diagnose. performance analysts must correlate hundreds of megabytes or gigabytes of performance counters (to understand resource usage) with execution logs (to understand system behaviour). However, little work has been done to combine these two types of information to assist performance analysts in their diagnosis. We propose an automated approach that combines performance counters and execution logs to diagnose memory-related issues in load tests. We perform three case studies on two systems: one open-source system and one large-scale enterprise system. Our approach flags ≤ 0.1% of the execution logs with a precision ≥ 80%.

关键词： Radiation detectors Standards Transient analysis Lifting equipment Memory management Couplings Visualization

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SymSig: A low latency interconnection topology for HPC clusters

SymSig: A low latency interconnection topology for HPC clust...

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International Conference on high performance computing

作者： Dhananjay Brahme Onkar Bhardwaj Vipin Chaudhary High Performance Computing Center of Excellence Tata Consultancy Services Pune India Department of Electrical Rensselaer Polytechnic Institute Troy NY Department of Computer Science and Engineering SUNY Buffalo New York

This paper presents the underlying theory and the performance of a cluster using a new 2-hop network topology. This topology is constructed using a symmetric equation and Singer Difference Sets and is called SymSig. The degree of connections at each node with SymSig is about half compared to previous methods using Singer Difference Sets. A comparison with a cluster of Clos topology shows significant advantages. The worst case congestion in SymSig topology for unicast permutation is 2, where as in Clos it is proportional to the radix of the building block switches used. The number of switches required is smaller by about 25%, the size of the cluster is larger by about 15% and the worst bandwidth is better by about 50% for SymSig. These advantages are retained for peta and exascale systems. Its performance on a set of collectives like exchange-all, shift-all, broadcast-all and all-to-all send/receive shows improvements ranging from 39% to 83%. Its performance on a molecular dynamics application GROMMACS shows improvement of upto 33%. This network is particularly suitable for applications that require global all to all communications. The low latency of this network makes it scaleable and an attractive alternative for building peta and exascale systems.

关键词： Routing Image color analysis Topology Network topology Ports (computers) Equations Bandwidth

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DisClose: Discovering colossal closed itemsets via a memory efficient compact row-tree

DisClose: Discovering colossal closed itemsets via a memory ...

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PAKDD 2012 International Workshops: 3rd Data Mining for Healthcare Management, DMHM 2012, Multi-View Data, high-Dimensionality, External Knowledge: Striving for a Unified Approach to Clustering, 3Clust 2012, GeoDoc 2012 and 2nd DSDM 2012

作者： Zulkurnain, Nurul F. Haglin, David J. Keane, John A. Department of Electrical and Computer Engineering Kuliyyah of Engineering International Islamic University Malaysia P.O. Box 10 Kuala Lumpur 50728 Malaysia High Performance Computing Pacific Northwest National Laboratory MSIN J4-30 P.O. Box 999 Richland WA 99352 United States School of Computer Science University of Manchester Oxford Road Manchester M13 9PL United Kingdom

ISBN: (纸本)9783642367779

A recent focus in itemset mining has been the discovery of frequent itemsets from high-dimensional datasets. With exponentially increasing running time as average row length increases, mining such datasets renders most conventional algorithms impractical. Unfortunately, large cardinality itemsets are likely to be more informative than small cardinality itemsets in this type of dataset. This paper proposes an approach, termed DisClose, to extract large cardinality (colossal) closed itemsets from high-dimensional datasets. The approach relies on a Compact Row-Tree data structure to represent itemsets during the search process. Large cardinality itemsets are enumerated first followed by smaller ones. In addition, we utilize a minimum cardinality threshold to further reduce the search space. Experimental results show that DisClose can achieve extraction of colossal closed itemsets in the discovered datasets, even for low support thresholds. The algorithm immediately discovers closed itemsets without needing to check if each new closed itemset has previously been found. © 2013 Springer-Verlag.

关键词： Trees (mathematics)

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high performance Solvers for Implicit Particle in Cell Simulation

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Procedia computer science 2013年 18卷 2251-2258页

作者： Pawan Kumar Stefano Markidis Giovanni Lapenta Karl Meerbergen Dirk Roose Department of Computer Science Celestijnenlaan 200A 3001 Heverlee Belgium Flanders Exascience Lab (Intel Labs Europe) Heverlee Belgium High Performance Computing and Visualization (HPCViz) Department KTH Royal Institute of Technology Stockholm Sweden Center for Plasma Astrophysics Department of Mathematics Celestijnenlaan 200B Heverlee Belgium

A three-dimensional implicit particle-in-cell (iPIC3D) method implemented by S. Markidis et. al. in [“Multiscale simulations of plasma with iPIC3D”, Mathematics and computers in Simulation, 80(2010), 1509-1519] allows time steps at magnetohy- drodynamics time scale. The code requires the solution of two linear systems: a Poisson system related to divergence cleaning, and a system related to a second order formulation of Maxwell equation. In iPIC3D, the former is the most costly. To reduce the cost of solving the Poisson system, a parallel matrix assembly and partitioning method are implemented, and conjugate gradient and algebraic multigrid (AMG) solvers from the Hypre library are called. The scalability of AMG as a solver is studied for 1D and 3D partitionings and compared to that of CG.

关键词： Implicit PIC Algebraic multigrid Krylov solvers Distributed memory

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An implementation of a multi-site virtual cluster cloud

An implementation of a multi-site virtual cluster cloud

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International Joint Conference on computer science and Software engineering (JCSSE)

作者： Pongsakorn U-chupala Putchong Uthayopas Kohei Ichikawa Susumu Date Hirotake Abe High Performance Computing and Networking Center Department of Computer Engineering Faculty of Engineering Kasetsart University Bangkok Thailand Software Design & Analysis Laboratory Graduate School of Information Science NAIST Nara Japan Cybermedia Center Osaka University Osaka Japan Division of Information Science Graduate School of Systems and Information Engineering University of Tsukuba Ibaragi Japan

ISBN: (纸本)9781479908059

The use of virtual cluster for high performance computing (HPC) work has a great benefit of hiding the complexity of physical infrastructure while providing a familiar HPC environment for users. Nevertheless, setting up one is still a challenging task for most users. In addition, the ability to span a virtual cluster across a multi-site cloud can even create a great potential for users to harness a much higher processing power from the cloud. In this paper, the development of a multi-site virtual cluster cloud is presented. This is done by providing the cloud infrastructures tailored specifically for virtual cluster deployment along with related utilities such as web-interface monitor and command line tools. To realize this infrastructure, an overlay network is created using Virtual Private Network (VPN) technology to merge every site into a single broadcast domain. Moreover, a Multi-tier VPN network topology is proposed to enhance the communication performance among the multi-site cloud. A smart virtual machine scheduling mechanism is introduced to reduce performance degradation caused by network delays. The experimental results show that the virtual cluster works well with highly parallel task with low communication among task. Thus, this technology can be used to support many classes of important HPC applications.

关键词： Virtual private networks Overlay networks Virtual machining Servers Rocks Cloud computing Bandwidth

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