• Journal of the Korea Computer Industry Society
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• v.6 no.3
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• pp.559-566
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• 2005

ALTIBASE is the relational main memory DBMS that enables us to develop the high performance and fault tolerant applications. It guarantees the short and predictable execution time as well as the basic functionality of conventional disk-based DBMS. We present the overview of system architecture and the performance analysis with respect to the various design choices. The assorted experiments are performed under the various environments. The results of TPC-H and Wisconsin benchmark tests are described. We illustrate the various performance comparisons under the various index mechanisms, the replication models, the transaction durabilities, and the application structures. A performance study shows the ALTIBASE system can be applied to the wide area of industrial DBMS fields.

• Journal of Korea Spatial Information System Society
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• v.6 no.1 s.11
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• pp.19-29
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• 2004

Recently, studies have been performed to improve the cache performance of the R-Tree in main memory. A general mothed to improve the cache performance of the R-Tree is to reduce size of an entry so that a node can store more entries and fanout of it can increase. However, this method generally requites additional process to reduce information of entries and do not support incremental updates. In addition, the cache miss always occurs on moving between a parent node and a child node. To solve these problems efficiently, this paper proposes and evaluates the PR-Tree that is an extended R-Tree indexing method using prefetching in main memory. The PR-Tree can produce a wider node to optimize prefetching without additional modifications on the R-Tree. Moreover, the PR-Tree reduces cache miss rates that occur in moving between a parent node and a child node. In our simulation, the search performance, the update performance, and the node split performance of the PR-Tree improve up to 38%. 30%, and 67% respectively, compared with the original R-Tree.

• Journal of KIISE
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• v.43 no.5
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• pp.590-595
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• 2016

In this study, we propose an efficient method for monitoring continuous top-k queries. In contrast to the conventional top-k queries, the presented top-k query considers both spatial and non-spatial attributes. We proposed a novel main-memory based grid access method, called Bit-Vector Grid Index (BVGI). The proposed method quickly identifies whether the moving objects are included in some of the grid cell by encoding a non-spatial attribute value of the moving object to bit-vector. Experimental simulations demonstrate that the proposed method is several times faster than the previous method and uses considerably less memory.

• Journal of KIISE:Databases
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• v.30 no.6
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• pp.651-665
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• 2003

To reduce cache misses emerges as the most important issue in today's situation of main memory databases, in which CPU speeds have been increasing at 60% per year, and memory speeds at 10% per year. Recent researches have demonstrated that cache-conscious index structure such as the CR-tree outperforms the R-tree variants. Its search performance can be poor than the original R-tree, however, since it uses a lossy compression scheme. In this paper, we propose alternatively a cache-conscious version of the R-tree, which we call MR-tree. The MR-tree propagates node splits upward only if one of the internal nodes on the insertion path has empty room. Thus, the internal nodes of the MR-tree are almost 100% full. In case there is no empty room on the insertion path, a newly-created leaf simply becomes a child of the split leaf. The height of the MR-tree increases according to the sequence of inserting objects. Thus, the HeightBalance algorithm is executed when unbalanced heights of child nodes are detected. Additionally, we also propose the CCMR-tree in order to build a more cache-conscious MR-tree. Our experimental and analytical study shows that the two-dimensional MR-tree performs search up to 2.4times faster than the ordinary R-tree while maintaining slightly better update performance and using similar memory space.

• International Journal of Contents
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• v.11 no.1
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• pp.69-72
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• 2015

Generally, existing parallel main-memory spatial index structures to avoid the trade-off between query freshness and CPU cost uses light-weight locking techniques. However, still, the lock based methods have some limits such as thrashing which is a well-known problem in lock based methods. In this paper, we propose a distributed index structure for moving objects exploiting the parallelism in multiple machines. The proposed index is a lock free multi-version concurrency technique based on the D-Stream model of Spark Stream. The proposed method exploits the multiversion nature of D-Stream of Spark Streaming.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.8 no.5
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• pp.1035-1041
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• 2004

Currently users are tend to use multimedia data types in their applications. Main features of multimedia data types are large amount of data compared to conventional data types. In this reason, it's hard to load data into main memory and to search. That is the cause of occur disk input and output frequently, and decrease the system performance. In this paper, we describe to have fast and efficient access to multimedia data using index technique. Index method presented by paper consists of two parts : one is index file part for keywords and the other is posting file part for the list of file names. Of course, we use keyword. But user is not charge of memory for the keywords. Users just use natural language to insert, delete and search data what he or she wants. Internally, System makes keywords from natural language to get access to multimedia data. It provides convenience to users. Using this study to develop one's application for multimedia, one may have a chance for advanced performance of a system and getting a result speedily.

• Journal of the Korea Society of Computer and Information
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• v.15 no.3
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• pp.1-10
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• 2010

As processor platforms are continuously moving toward wireless mobile systems, embedded mobile processors are expected to perform more and more powerful, and therefore the development of an efficient power management algorithm for these battery-operated mobile and handheld systems has become a critical challenge. It is well known that a memory system is a main performance limiter in the processor point of view. Although many DVFS studies have been considered for the efficient utilization of limited battery resources, recent works do not explicitly show the interaction between the processor and the memory. In this research, to properly reflect short/long-term memory access patterns of the embedded workloads in wireless mobile processors, we propose a memory buffer utilization as a new index of DVFS level prediction. The simulation results show that our solution provides 5.86% energy saving compared to the existing DVFS policy in case of memory intensive applications, and it provides 3.60% energy saving on average.

• Proceedings of the Korean Information Science Society Conference
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• 2003.04a
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• pp.794-796
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• 2003

주기억 데이타베이스 시스템은 기존의 디스크 기반 데이타베이스 시스템과 달리 빠른 처리속도와 주기억 장치의 효율적인 사용이 주된 관심 사항이다. 본 논문에서는 주기억 데이타베이스에서 공간 데이터를 위한 효율적인 인덱스구조를 제시한다. 기존에 제시된 주기억 데이타베이스를 위한 인덱스 기법으로는 T-트리, Hash 계열 기법등이 제시되었으나, 이러한 모든 인덱스 기법은 1차원 데이타를 위한 인덱스 기법으로 공간 데이타에는 적용이 불가능하다. 이러한 제약을 극복하기 위해서 본 논문에서는 T-트리에 R-트리 개념을 추가 하였다.

• Journal of Power Electronics
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• v.11 no.2
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• pp.228-236
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• 2011

The ${\Delta}\;V_{10}$ or 10-Hz flicker index, as a common method of measurement of voltage flicker severity in power systems, requires a high computational cost and a large amount of memory. In this paper, for measuring the ${\Delta}\;V_{10}$ index, a new method based on the Adaline (adaptive linear neuron) system, the FFT (fast Fourier transform), and the PSO (particle swarm optimization) algorithm is proposed. In this method, for reducing the sampling frequency, calculations are carried out on the envelope of a power system voltage that contains a flicker component. Extracting the envelope of the voltage is implemented by the Adaline system. In addition, in order to increase the accuracy in computing the flicker components, the PSO algorithm is used for reducing the spectral leakage error in the FFT calculations. Therefore, the proposed method has a lower computational cost in FFT computation due to the use of a smaller sampling window. It also requires less memory since it uses the envelope of the power system voltage. Moreover, it shows more accuracy because the PSO algorithm is used in the determination of the flicker frequency and the corresponding amplitude. The sensitivity of the proposed method with respect to the main frequency drift is very low. The proposed algorithm is evaluated by simulations. The validity of the simulations is proven by the implementation of the algorithm with an ARM microcontroller-based digital system. Finally, its function is evaluated with real-time measurements.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.28 no.4B
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• pp.323-338
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• 2003

The main memory database systems (MMDBMS) efficiently supports various database applications that require high performance since it employs main memory rather than disk as a primary storage. Recently, it has been increased needs that have the fast data processing as well as the efficient modeling of application requiring for a complicated structure, and conformity to applications that need the strict dta consistency. In MMDBMS, because all the data is located in the main memory, it can support the usable expression methods of data satisfying their needs without performance overhead. The method has the operation to manipulate the data and the constraint such as referential integrity in more detail. The data model consists of this methods is an essential component to decide the expression power of DBMS. In this paper, we discuss about various requests to provide the communication services and propose the data model that support it. The mainly discussed issues are 1) definition of the relationship between tables using the pointer, 2) navigation of the data using the relationship, 3) support of the referential integrity for pointer, 4) support of the uniform processing time for the join, 5) support of the object-oriented concepts, and 6) sharing of an index on multi-tables. We discuss the pointer-based data model that designed to include these issues to efficiently support complication environments.