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The impact of spatial data redundancy on SOLAP query performance

Journal of the Brazilian computer Society 2009年第2期15卷 19-34页

作者： Siqueira, Thiago Luís Lopes Ciferri, Cristina Dutra de Aguiar Times, Valéria Cesário de Oliveira, Anjolina Grisi Ciferri, Ricardo Rodrigues Computer Science Department Federal University of São Carlos - UFSCar 13565-905 São Carlos SP Brazil São Paulo Federal Institute of Education Science and Technology IFSP Salto Campus 13320-271 Salto SP Brazil Computer Science Department ICMC University of São Paulo - USP 13560-970 São Carlos SP Brazil Informatics Center Federal University of Pernambuco - UFPE 50670-901 Recife PE Brazil

Geographic Data Warehouses (GDW) are one of the main technologies used in decision-making processes and spatial analysis, and the literature proposes several conceptual and logical data models for GDW. However, little effort has been focused on studying how spatial data redundancy affects SOLAP (Spatial On-Line Analytical Processing) query performance over GDW. In this paper, we investigate this issue. Firstly, we compare redundant and non-redundant GDW schemas and conclude that redundancy is related to high performance losses. We also analyze the issue of indexing, aiming at improving SOLAP query performance on a redundant GDW. Comparisons of the SB-index approach, the star-join aided by R-tree and the star-join aided by GiST indicate that the SB-index significantly improves the elapsed time in query processing from 25% up to 99% with regard to SOLAP queries defined over the spatial predicates of intersection, enclosure and containment and applied to roll-up and drill-down operations. We also investigate the impact of the increase in data volume on the performance. The increase did not impair the performance of the SB-index, which highly improved the elapsed time in query processing. Performance tests also show that the SB-index is far more compact than the star-join, requiring only a small fraction of at most0.20% of the volume. Moreover, we propose a specific enhancement of the SB-index to deal with spatial data redundancy. This enhancement improved performance from 80 to 91% for redundant GDW schemas.

关键词： Query processing

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Skin lesion detection using fuzzy region growing and ABCD feature extraction for melanoma skin cancer diagnosis

Skin lesion detection using fuzzy region growing and ABCD fe...

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作者： Fatichah, Chastine Amaliah, Bilqis Widyanto, M. Rahmat Informatics Department Faculty of Information Technology Institute of Technology Sepuluh Nopember Surabaya Jawa Timur 60111 Indonesia Faculty of Computer Science University of Indonesia Kampus UI Depok Jawa Barat 16424 Indonesia

To improve accuracy of localize suspicious lesion region in dermatoscopic images using Region Growing, the initial step based on fuzzy sets to enhance the lesion region of interest (ROI) is developed. The result of skin lesion detection is used to extract Asymmetry, Border Irregularity, Color Variation, Diameter (ABCD) features for melanoma skin cancer diagnosis. ABCD feature is the rule that is used dermatologist for obtain the important information of image dermatoscopic lesion. This feature is used to diagnose melanoma skin cancer based on Total Dermatoscopic Value (TDV). There are three diagnosis that is used on this research i.e. melanoma, suspicious, and benign skin lesion. The experiment uses 30 samples of image dermatoscopic lesion that is suspicious melanoma skin cancer. Based on the experiment, the accuracy using fuzzy region growing is 86.6% that there are 4 false diagnoses of 30 samples. But the accuracy using region growing is 76.6% that there are 7 false of 30 samples.

关键词： Feature extraction

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Load Balancing in a Cluster-Based P2P System

Load Balancing in a Cluster-Based P2P System

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Balkan Conference in informatics (BCI)

作者： John Garofalakis Theofanis-Aristofanis Michail Department of Computer Engineering & Informatics University of Patras Patras Greece Research Academic Computer Technology Institute Rio-Patras Greece

In this paper we study load balancing in a cluster based p2p system. The cluster based architecture is chosen after the study of various real systems. We then define the notion of load for that system and describe coefficients that measure the different parameters of load. We use these coefficients to define load factors that can be used to measure each node's load. These factors are also used in two algorithms that balance the load fairly among all peers in a cluster. We improve the algorithms' balancing performance using replication of popular objects. A set of metrics is used to evaluate the cost of each algorithm and the effect on system's performance. Our simulation results show that it is possible to improve the fairness on load distribution without replication but with a small reduce on system's throughput. And under the cost of replicating a small amount of objects we improve fairness without reducing system's throughput.

关键词： Load management Peer to peer computing Costs System performance Clustering algorithms Throughput Quality of service informatics computer architecture Measurement

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Performance evaluation for multistage interconnection networks servicing unicast and multicast traffic (by partial operation)

Performance evaluation for multistage interconnection networ...

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International Symposium on Performance Evaluation of computer & Telecommunication Systems SPECTS

作者： John Garofalakis Eleftherios Stergiou Department of Computer and Informatics Research Academics Computer Technology Institute University of Patras Patras Greece Department of Information Technology and Telecommunication ATEI of Epirus Arta Greece

In this paper a novel performance evaluation method for multistage interconnection networks (MINs) servicing unicast and multicast traffic is presented. The multicasting policy where a packet is copied and transmitted is not only applied when both next stage destination buffers are available but also when at least one destination buffer is able to accept packets. This mechanism, which is called "partial multicast", was employed by all SEs using the "Cell Replication While Routing" (CRWR) technique. The proposed analysis was applied to various network-size MINs constructed by symmetrical Switching Elements (SEs), supporting mixed traffic patterns such as unicast and multicast, under various offered loads in uniform traffic conditions. The performance of MINs with partial multicasting transmission, which is thoroughly analyzed by our analytical model, can also be useful in performance study and development of other alternative architectures of multistage networks that also support mixed traffic.

关键词： Multiprocessor interconnection networks Unicast Telecommunication traffic Traffic control Performance analysis Communication switching Analytical models Internet Switches computer networks

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Image-based automatic object localisation in iSpace environment

Image-based automatic object localisation in iSpace environm...

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10th International Symposium of Hungarian Researchers on Computational Intelligence and informatics, CINTI 2009

作者： Zanaty, Péter Korondi, Péter Sziebig, Gábor Jeni, László A. Department of Scientific Computing Narvik University College Electrical Engineering and Space technology Hungary Department of Mechatronics Budapest University of Technology and Economics Optics and Applied Informatics Hungary Computer and Automation Research Institute Japan Department of Industrial Engineering Narvik University College Norway Institute of Industrial Science University of Tokyo Japan

Localization is a fundamental task in mobile robotics and in indoor environments we can use various sensors to solve this problem. In the Intelligent Space environment we can use laser range finders or ultrasonic positioning systems to localize and track mobile robots. Nevertheless, our final goal is to substitute these sensors and accomplish this task using just cameras. In this paper, we show the feasibility of determining the robot's location based on the images received from a single camera. In our experimental room we used a surveillance camera, which can be controlled to pan/tilt in order to change the point of view. The camera had been mounted on the ceiling and six preset positions were selected to cover the whole area. The object recognition is based on colour space filtering and contour detection. Finally, the contours of the detected objects are transformed from the image space to the world coordinate system and the polygons are reduced to simpler ones. The system is able to detect not only the position of the objects, but their orientations.

关键词： Cameras

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On the Approximability of Dodgson and Young Elections 09

On the Approximability of Dodgson and Young Elections

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Annual ACM-Society for Industrial and Applied Mathmatics Symposium on Discrete Algorithms

作者： Ioannis Caragiannis Jason A. Coveyy Michal Feldmanz Christopher M. Homanx Christos Kaklamanis Nikos Karanikolask Ariel D. Procaccia Jeffrey S. Rosenscheinyy Research Academic Computer Technology Institute and Department of Computer Engineering and Informatics University of Patras Department of Computer Science Rochester Institute of Technology School of Business Administration and Center forthe Study of Rationality The Hebrew University of Jerusalem Research Academic Computer Technology Institute and Department of Computer Engineering and Informatics University of Patras Microsoft Israel R&D Center School of Computer Science and Engineering The He-brew University of Jerusalem

The voting rules proposed by Dodgson and Young are both designed to find the alternative closest to being a Condorcet winner, according to two different notions of proximity; the score of a given alternative is known to be hard to compute under either rule. In this paper, we put forward two algorithms for approximating the Dodgson score: an LP-based randomized rounding algorithm and a deterministic greedy algorithm, both of which yield an O(logm) approximation ratio, where m is the number of alternatives; we observe that this result is asymptotically optimal, and further prove that our greedy algorithm is optimal up to a factor of 2, unless problems in NP have quasi-polynomial time algorithms. Although the greedy algorithm is computationally superior, we argue that the randomized rounding algorithm has an advantage from a social choice point of view. Further, we demonstrate that computing any reasonable approximation of the ranking produced by Dodgson's rule is NP-hard. This result provides a complexity-theoretic explanation of sharp discrepancies that have been observed in the Social Choice Theory literature when comparing Dodgson elections with simpler voting rules. Finally, we show that the problem of calculating the Young score is NP-hard to approximate by any factor. This leads to an inapproximability result for the Young ranking.

关键词： greedy algorithm Nondeterministic polynomial-time hard Youth rounding Rule Vote algorithms

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DryadLINQ for scientific analyses

DryadLINQ for scientific analyses

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5th IEEE International Conference on e-Science, e-Science 2009

作者： Ekanayake, Jaliya Gunarathne, Thilina Fox, Geoffrey Balkir, Atilla Soner Poulain, Christophe Araujo, Nelson Barga, Roger School of Informatics and Computing Indiana University Bloomington United States Pervasive Technology Institute Indiana University Bloomington United States Department of Computer Science University of Chicago United States Microsoft Research United States

ISBN: (纸本)9780769538778

Applying high level parallel runtimes to data/compute intensive applications is becoming increasingly common. The simplicity of the MapReduce programming model and the availability of open source MapReduce runtimes such as Hadoop, are attracting more users to the MapReduce programming model. Recently, Microsoft has released DryadLINQ for academic use, allowing users to experience a new programming model and a runtime that is capable of performing large scale data/compute intensive analyses. In this paper, we present our experience in applying DryadLINQ for a series of scientific data analysis applications, identify their mapping to the DryadLINQ programming model, and compare their performances with Hadoop implementations of the same applications. © 2009 IEEE.

关键词： MapReduce

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A Multicost Approach to Online Impairment-Aware RWA

A Multicost Approach to Online Impairment-Aware RWA

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IEEE International Conference on Communications (ICC)

作者： K. Christodoulopoulos K. Manousakis E. A. Varvarigos M. Angelou I. Tomkos Computer Engineering and Informatics Department and Research Academic Computer Technology Institute University of Patras Patras Greece Athens Information Technology Center Athens Greece

We design and implement a multicost impairment- aware routing and wavelength assignment algorithm for online traffic. In transparent optical networks the quality of a transmission degrades due to physical layer impairments. To serve a connection, the proposed algorithm finds a path and a free wavelength (a lightpath) that has acceptable signal quality performance by estimating a quality of transmission measure, called the Q factor. We take into account channel utilization in the network, which changes as new connections are established or released, in order to calculate the noise variances that correspond to physical impairments on the links. These, along with the time invariant eye impairment penalties of all candidate network paths, form the inputs to the algorithm. The multicost algorithm finds a set of so called non-dominated Q paths from the given source to the given destination. Various objective functions are then evaluated in order to choose the optimal lightpath to serve the connection. The proposed algorithm combines the strength of multicost optimization with low execution time, making it appropriate for serving online connections.

关键词： Algorithm design and analysis Wavelength routing Wavelength assignment Telecommunication traffic Optical fiber networks Degradation Physical layer Q measurement Wavelength measurement Q factor

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On the Use of Multi-Objective Optimization Algorithms for Solving the Impairment Aware-RWA Problem

On the Use of Multi-Objective Optimization Algorithms for So...

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IEEE International Conference on Communications (ICC)

作者： D. Monoyios K. Vlachos M. Aggelou I. Tomkos Computer Engineering and Informatics Department & Research Academic Computer Technology Institute University of Patras Rio Greece Athens Information Technology Center Athens Greece

In future transparent optical networks, it is important to consider the impact of physical impairments in the routing and wavelengths assignment process, to achieve efficient connection provisioning. In this paper, we use classical multi-objective optimization (MOO) strategies and particularly genetic algorithms to jointly solve the impairment aware RWA (IA-RWA) problem. Fiber impairments are indirectly considered through the insertion of the path length and the number of common hops in the optimization process. It is shown that blocking is greatly improved, while the obtained solutions truly converge towards the Pareto front that constitutes the set of global optimum solutions. We have evaluated our findings, using an Q estimator tool, that calculates the signal quality of each path analytically.

关键词： Genetic algorithms Optimization methods Optical fiber networks Wavelength routing Peer to peer computing Cost function Wavelength assignment Communications Society Genetic engineering informatics

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Public Infrastructure for Monte Carlo Simulation : publicMC@BATAN

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AIP Conference Proceedings 2010年第1期1244卷 190-195页

作者： A. A. Waskita N. A. Prasetyo Z. Akbar L. T. Handoko aCenter for Development of Nuclear Informatics3 National Nuclear Energy Agency Kompleks Puspiptek Serpong Tangerang 15310 Indonesia bCenter for Applied Aerospace Technology National Space and Aviation Agency4 Jl. Raya LAPAN‐Rumpin Tromol Pos 7 Serpong Tangerang 15310 Indonesia cFaculty of Computing Science5 University of Indonesia Kampus UI Depok Depok 16424 Indonesia dGroup for Theoretical and Computational Physics Research Center for Physics6 Indonesian Institute of Sciences Kompleks Puspiptek Serpong Tangerang 15310 Indonesia eGroup for Bioinformatics and Information Mining7 Department of Computer and Information Science University of Konstanz Box D188 D‐78457 Konstanz Germany fDepartment of Physics8 University of Indonesia Kampus UI Depok Depok 16424 Indonesia

The first cluster‐based public computing for Monte Carlo simulation in Indonesia is introduced. The system has been developed to enable public to perform Monte Carlo simulation on a parallel computer through an integrated and user friendly dynamic web interface. The beta version, so called publicMC@BATAN, has been released and implemented for internal users at the National Nuclear Energy Agency (BATAN). In this paper the concept and architecture of publicMC@BATAN are presented.

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