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REFERENCE LINKING PLATFORM OF KOREA S&T JOURNALS
> Journal Vol & Issue
Journal of Computing Science and Engineering
Journal Basic Information
Journal DOI :
Korean Institute of Information Scientists and Engineers
Editor in Chief :
In-Sup Lee / Il-Yeol Song / Jong C. Park / Tae-Whan Kim
Volume & Issues
Volume 7, Issue 4 - Dec 2013
Volume 7, Issue 3 - Sep 2013
Volume 7, Issue 2 - Jun 2013
Volume 7, Issue 1 - Mar 2013
Selecting the target year
Minimizing the MOLAP/ROLAP Divide: You Can Have Your Performance and Scale It Too
Eavis, Todd ; Taleb, Ahmad ;
Journal of Computing Science and Engineering, volume 7, issue 1, 2013, Pages 1~20
DOI : 10.5626/JCSE.2013.7.1.1
Over the past generation, data warehousing and online analytical processing (OLAP) applications have become the cornerstone of contemporary decision support environments. Typically, OLAP servers are implemented on top of either proprietary array-based storage engines (MOLAP) or as extensions to conventional relational DBMSs (ROLAP). While MOLAP systems do indeed provide impressive performance on common analytics queries, they tend to have limited scalability. Conversely, ROLAP's table oriented model scales quite nicely, but offers mediocre performance at best relative to the MOLAP systems. In this paper, we describe a storage and indexing framework that aims to provide both MOLAP like performance and ROLAP like scalability by essentially combining some of the best features from both. Based upon a combination of R-trees and bitmap indexes, the storage engine has been integrated with a robust OLAP query engine prototype that is able to fully exploit the efficiency of the proposed storage model. Specifically, it utilizes an OLAP algebra coupled with a domain specific query optimizer, to map user queries directly to the storage and indexing framework. Experimental results demonstrate that not only does the design improve upon more naive approaches, but that it does indeed offer the potential to optimize both query performance and scalability.
Using Experts Among Users for Novel Movie Recommendations
Lee, Kibeom ; Lee, Kyogu ;
Journal of Computing Science and Engineering, volume 7, issue 1, 2013, Pages 21~29
DOI : 10.5626/JCSE.2013.7.1.21
The introduction of recommender systems to existing online services is now practically inevitable, with the increasing number of items and users on online services. Popular recommender systems have successfully implemented satisfactory systems, which are usually based on collaborative filtering. However, collaborative filtering-based recommenders suffer from well-known problems, such as popularity bias, and the cold-start problem. In this paper, we propose an innovative collaborative-filtering based recommender system, which uses the concepts of Experts and Novices to create fine-grained recommendations that focus on being novel, while being kept relevant. Experts and Novices are defined using pre-made clusters of similar items, and the distribution of users' ratings among these clusters. Thus, in order to generate recommendations, the experts are found dynamically depending on the seed items of the novice. The proposed recommender system was built using the MovieLens 1 M dataset, and evaluated with novelty metrics. Results show that the proposed system outperforms matrix factorization methods according to discovery-based novelty metrics, and can be a solution to popularity bias and the cold-start problem, while still retaining collaborative filtering.
Energy Aware Scheduling of Aperiodic Real-Time Tasks on Multiprocessor Systems
Anne, Naveen ; Muthukumar, Venkatesan ;
Journal of Computing Science and Engineering, volume 7, issue 1, 2013, Pages 30~43
DOI : 10.5626/JCSE.2013.7.1.30
Multicore and multiprocessor systems with dynamic voltage scaling architectures are being used as one of the solutions to satisfy the growing needs of high performance applications with low power constraints. An important aspect that has propelled this solution is effective task/application scheduling and mapping algorithms for multiprocessor systems. This work proposes an energy aware, offline, probability-based unified scheduling and mapping algorithm for multiprocessor systems, to minimize the number of processors used, maximize the utilization of the processors, and optimize the energy consumption of the multiprocessor system. The proposed algorithm is implemented, simulated and evaluated with synthetic task graphs, and compared with classical scheduling algorithms for the number of processors required, utilization of processors, and energy consumed by the processors for execution of the application task graphs.
An Efficient Scheduling Method for Grid Systems Based on a Hierarchical Stochastic Petri Net
Shojafar, Mohammad ; Pooranian, Zahra ; Abawajy, Jemal H. ; Meybodi, Mohammad Reza ;
Journal of Computing Science and Engineering, volume 7, issue 1, 2013, Pages 44~52
DOI : 10.5626/JCSE.2013.7.1.44
This paper addresses the problem of resource scheduling in a grid computing environment. One of the main goals of grid computing is to share system resources among geographically dispersed users, and schedule resource requests in an efficient manner. Grid computing resources are distributed, heterogeneous, dynamic, and autonomous, which makes resource scheduling a complex problem. This paper proposes a new approach to resource scheduling in grid computing environments, the hierarchical stochastic Petri net (HSPN). The HSPN optimizes grid resource sharing, by categorizing resource requests in three layers, where each layer has special functions for receiving subtasks from, and delivering data to, the layer above or below. We compare the HSPN performance with the Min-min and Max-min resource scheduling algorithms. Our results show that the HSPN performs better than Max-min, but slightly underperforms Min-min.
Bounding Worst-Case DRAM Performance on Multicore Processors
Ding, Yiqiang ; Wu, Lan ; Zhang, Wei ;
Journal of Computing Science and Engineering, volume 7, issue 1, 2013, Pages 53~66
DOI : 10.5626/JCSE.2013.7.1.53
Bounding the worst-case DRAM performance for a real-time application is a challenging problem that is critical for computing worst-case execution time (WCET), especially for multicore processors, where the DRAM memory is usually shared by all of the cores. Typically, DRAM commands from consecutive DRAM accesses can be pipelined on DRAM devices according to the spatial locality of the data fetched by them. By considering the effect of DRAM command pipelining, we propose a basic approach to bounding the worst-case DRAM performance. An enhanced approach is proposed to reduce the overestimation from the invalid DRAM access sequences by checking the timing order of the co-running applications on a dual-core processor. Compared with the conservative approach, which assumes that no DRAM command pipelining exists, our experimental results show that the basic approach can bound the WCET more tightly, by 15.73% on average. The experimental results also indicate that the enhanced approach can further improve the tightness of WCET by 4.23% on average as compared to the basic approach.
Multicore Real-Time Scheduling to Reduce Inter-Thread Cache Interferences
Ding, Yiqiang ; Zhang, Wei ;
Journal of Computing Science and Engineering, volume 7, issue 1, 2013, Pages 67~80
DOI : 10.5626/JCSE.2013.7.1.67
The worst-case execution time (WCET) of each real-time task in multicore processors with shared caches can be significantly affected by inter-thread cache interferences. The worst-case inter-thread cache interferences are dependent on how tasks are scheduled to run on different cores. Therefore, there is a circular dependence between real-time task scheduling, the worst-case inter-thread cache interferences, and WCET in multicore processors, which is not the case for single-core processors. To address this challenging problem, we present an offline real-time scheduling approach for multicore processors by considering the worst-case inter-thread interferences on shared L2 caches. Our scheduling approach uses a greedy heuristic to generate safe schedules while minimizing the worst-case inter-thread shared L2 cache interferences and WCET. The experimental results demonstrate that the proposed approach can reduce the utilization of the resulting schedule by about 12% on average compared to the cyclic multicore scheduling approaches in our theoretical model. Our evaluation indicates that the enhanced scheduling approach is more likely to generate feasible and safe schedules with stricter timing constraints in multicore real-time systems.