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International Conference on High Performance computing in the Asia-Pacific Region

作者： Meng-Shiou Wu R.A. Kendall S. Aluru Department of Electrical and Computer Engineering Scalable Computing Laboratory US DOE Ames IA USA Department of Electrical and Computer Engineering Department of Computer Science Ames IA

We investigate two strategies to improve the performance of collective communications on a cluster of SMPs. In the first part of the paper, we explore the advantages and disadvantages of the commonly used strategy "optimize shared memory send and receive only". In the second part of the paper, we show a model to design collective communications on SMP clusters which can be used to improve the disadvantages of the former strategy. Several collective operations are implemented through the later process, and the experimental results show better performance than vendor supplied implementations.

关键词： Switched-mode power supply Laboratories Clustering algorithms US department of Energy computer science Optimization methods Broadcasting Libraries Testing Communication standards

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On-line dynamic voltage scaling for hard real-time systems using the EDF algorithm

On-line dynamic voltage scaling for hard real-time systems u...

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real-time Systems Symposium (RTSS)

作者： Cheol-Hoon Lee K.G. Shin System Software Laboratory Department of Computer Engineering Chungnam National University Taejon South Korea Real-Time Computing Laboratory Department of EECS University of Michigan Ann Arbor MI USA

Recently, there has been a rapid and wide spread of non-traditional computing platforms, especially mobile and portable computing devices. As applications become sophisticated and computation power increases, the most serious limitation on these devices is the available battery life. Dynamic voltage scaling (DVS) has been a key technique to exploit the hardware characteristics of processors to reduce energy dissipation by lowering the supply voltage and operating frequency. This paper presents a novel on-line DVS algorithm called OLDVS that, when coupled with the underlying OS task management mechanism and real-time scheduler, can make significant energy savings, while preserving timeliness guarantees made by the underlying real-time scheduling algorithm. While most existing DVS algorithms are confined to periodic tasks only, OLDVS does not assume task periodicity, nor does it require any a priori information on the task set to be scheduled. OLDVS requires only O(1) computation on each task context switch, thus making it fairly easy to be incorporated into a real-time operating system. The OLDVS algorithm considers a general task model which is very difficult, if not impossible, for the existing DVS algorithms to handle. Our simulation results show that OLDVS achieves great energy savings and outperforms the existing DVS algorithms when the ratio of the computation requirement of aperiodic tasks to the total computation requirement is higher than 40%. The performance advantage becomes much larger as the ratio increases.

关键词： Dynamic voltage scaling real time systems Voltage control Scheduling algorithm Portable computers Processor scheduling Switches Mobile computing Batteries Hardware

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On the beamforming weight of the MIMO/SDMA system under channel uncertainty

On the beamforming weight of the MIMO/SDMA system under chan...

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IEEE Conference on Vehicular Technology (VTC)

作者： Kyungchun Lee Joohwan Chun Scientific Computing Laboratory Department of Electrical Engineering and Computer Science Korea Advanced Institute of Science and Technology Daejeon South Korea

ISBN: (纸本)0780382552

We consider beamforming methods for the downlink of space division multiple access (SDMA) systems when there are channel information errors. A single antenna at the mobile is generally assumed in SDMA systems, but we consider multi-input and multi-output (MIMO) systems which adopt multiple antennas at both transmitter and receiver. If we know the exact channel information of each user, cochannel interference among users can be perfectly removed by the zero-forcing nulling method in MIMO/SDMA systems. However, the channel estimate always contains estimation errors in real systems, which can cause significant performance degradation. To cope with channel information errors, we develop two beamforming weights based on null-space constraints. The first one is designed to minimize the transmit power while not influencing the desired receive signal. The interfering effect from channel information errors is reduced since the transmit power of cochannel interfering users is minimized. The second one is designed to minimize the power of the received interference signal. It computes the beamforming weight which has the minimum expectation of interference power with knowledge of the variance of channel estimation errors. The proposed beamforming weights are tested by computer simulations.

关键词： Array signal processing MIMO Multiaccess communication Uncertainty Mobile antennas Receiving antennas Transmitting antennas Signal design Interference Downlink

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Carrier frequency recovery in MIMO and OFDM systems using orthogonal training sequences

Carrier frequency recovery in MIMO and OFDM systems using or...

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IEEE Conference on Vehicular Technology (VTC)

作者： Kyunchun Lee Joohwan Chun Scientific Computing Laboratory Department of Electrical Engineering and Computer Science Korea Advanced Institute of Science and Technology Daejeon South Korea

ISBN: (纸本)0780385217

We propose a training-sequence-based frequency offset estimator for a multiple transmit-and-receive antenna system in frequency-flat fading channels. The estimator is based on a maximum likelihood (ML) criterion and does not require channel information. To reduce the computational load, we propose to use special training sequences - the periodic orthogonal codes. Using these codes, we get a closed form estimator which requires much lower computational load (some additions and multiplications). For a high signal-to-noise ratio (SNR) and small frequency offset, the proposed estimator achieves the performance of the optimal ML estimator, which locates the peak of the likelihood function. We also apply the proposed estimator to an orthogonal frequency division multiplexing (OFDM) system. With simulations, we test the performance of the proposed estimator.

关键词： MIMO OFDM Frequency estimation Transmitting antennas Maximum likelihood estimation Receiving antennas Fading Oscillators AWGN Scientific computing

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Algorithmic-Parameter optimization of a parallelized split-step fourier transform using a modified BSP cost model 04

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Proceedings of the Second international conference on Parallel and Distributed Processing and Applications

作者： Elankovan Sundararajan Malin Premaratne Shanika Karunasekera Aaron Harwood Department of Computer Science and Software Engineering The University of Melbourne Carlton Victoria Australia Advanced Computing and Simulation Laboratory Department for Electrical and Computer System Engineering Monash University Clayton Victoria Australia

ISBN: (纸本)9783540241287

Adaptive algorithms are increasingly acknowledged in leading parallel and distributed research. In the past, algorithms were manually tuned to be executed efficiently on a particular architecture. However, interest has shifted towards algorithms that can adapt themselves to the computational resources. A cost model representing the behavior of the system (i.e. system parameters) and the algorithm (i.e algorithm parameters) plays an important role in adaptive parallel algorithms. In this paper, we contribute a computational model based on Bulk Synchronous Parallel processing that predicts performance of a parallelized split-step Fourier transform. We extracted the system parameters of a cluster (upon which our algorithm was executed) and showed the use of an algorithmic parameter in the model that exhibits optimal behavior. Our model can thus be used for the purpose of self-adaption.

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Sequential and Parallel Meta-Heuristics for Solving the Single Row Routing Problem

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Cluster computing 2004年第2期7卷 123-139页

作者： Zomaya, Albert Y. Patterson, Daniel Olariu, Stephan School of Information Technologies The University of Sydney Sydney Australia Parallel Computing Research Laboratory Department of Electrical and Electronic Engineering The University of Western Australia Australia Department of Computer Science Old Dominion University Norfolk USA

The design of multi-layer printed circuit boards is vital in the construction of complex electronic systems. Wire routing is a crucial step in the overall design process, which can be decomposed into a number of single row routing (SRR) problems. This paper proposes an approach to solve the SRR problem based on parallel meta-heuristics. The development of this technique involves the design of an encoding strategy that allows all possible routings to be uniquely represented and the derivation of cost functions that maximizes the quality of the developed solutions. Further, parallelization of the proposed approach is attempted to improve the computational efficiency. The different stages of the development are backed by experiments to show the pros and cons of the sequential and parallel implementations.

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Algorithmic-parameter optimization of a parallelized split-step Fourier transform using a modified BSP cost model

Lecture Notes in Computer Science (including subseries Lectu...

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Lecture Notes in computer science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics) 2004年 3358卷 233-244页

作者： Sundararajan, Elankovan Premaratne, Malin Karunasekera, Shanika Harwood, Aaron Department of Computer Science and Software Engineering University of Melbourne ICT Building 111 Barry Street Carlton Vic. 3053 Australia Advanced Computing and Simulation Laboratory Department for Electrical and Computer System Engineering Monash University Clayton Vic. 3800 Australia

关键词： Adaptive algorithms

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Steps towards 'undigital' intelligent image processing: real-valued image coding of photoquantimetric pictures into the JLM file format for the compression of portable lightspace maps

Steps towards 'undigital' intelligent image processing: real...

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IEEE International Symposium on Intelligent Signal Processing and Communication Systems (ISPACS)

作者： S. Mann C. Manders B.L. Belmellat L. Kansal D. Chen EyeTap Personal Imaging (ePi) Laboratory Department of Electrical and Computer Engineering University of Toronto Toronto ONT Canada Human Media Laboratory (HML) School of Computing and Information Science Queen's University Kingston ONT Canada

Recent advances in intelligent signal processing have made it possible to capture high dynamic range images which are better represented as an array of real numbers rather than the current convention of an array of integers. This paper proposes a solution to address the need for real, rather than just integer, image coding and file formats. Additionally, we propose that the real-valued data be linear in photoquantity (the quantity of light received by the camera) to avoid the image misrepresentation that occurs when a camera's non-linear dynamic range compressor and a display's dynamic range non-linear expander do not match. We present two novel image formats that achieve this: the portable lightspace map (PLM) and its compressed version the JPEG lightspace map (JLM), that builds upon the JPEG compression scheme. The results of various compression levels for real-valued data and their corresponding file sizes are reported.

关键词： Image coding Image processing Dynamic range Digital cameras Spatial resolution Optical arrays Transform coding Displays Sensor arrays Portable computers

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Integrated modeling and analysis of computer-based embedded control systems 10

Integrated modeling and analysis of computer-based embedded ...

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10th IEEE International Conference and Workshop on the engineering of computer-Based Systems, ECBS 2003

作者： Gu, Zonghua Shin, K.G. Real-Time Computing Laboratory Electrical Engineering and Computer Science Department University of Michigan Ann ArborMI48109 United States

ISBN: (纸本)0769519172

Embedded real-time systems are ubiquitous in modern society, many of which perform safety-critical functions, and therefore, it is imperative to have tools and techniques that can guarantee a high degree of system correctness. They typically perform information processing on a digital computer tightly coupled with the continuous physical environment. Even though hybrid systems is an active research area, most work has ignored the scheduling behavior of software processes due to contention for the shared CPU resource. We propose an integrated approach based on hybrid automata and model-checking for modeling and analysis of computer-based embedded control systems where real-time scheduling behavior of the controller software is explicitly represented at the model-level, together with the physical environment that it interacts with. An application example is used to demonstrate the benefits of the integrated approach in performing tradeoff analysis involving both the controller software and the controlled physical system. © 2003 IEEE.

关键词： Control system synthesis

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A model-based approach to system-level dependency and real-time analysis of embedded software

A model-based approach to system-level dependency and real-t...

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9th IEEE real-time and Embedded Technology and Applications Symposium, RTAS 2003

作者： Gu, Zonghua Kodase, S. Wang, Shige Shin, K.G. Real-Time Computing Laboratory Department of Electrical Engineering and Computer Science University of Michigan Ann Arbor MI 48109-2122 United States

We describe an end-to-end tool-chain for model-based design and analysis of component-based embedded real-time software. All aspects of an embedded real-time system are captured in domain-specific models, including software components and architecture, timing and resource constraints, processes and threads, execution platforms, etc. We focus on the AIRES tool, which performs various static analysis tasks based on the models, including system-level dependency analysis, execution rate assignment to component ports, real-time and schedulability analysis, and automated allocation of components to processors. By capturing all relevant information explicitly in the models at the design-level, and performing analysis that provide insight into nonfunctional aspects of the system, we can raise the level of abstraction for the designer, and facilitate rapid system prototyping. © 2003 IEEE.

关键词： Static analysis

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