• Proceedings of the Korea Information Processing Society Conference
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• 2003.05a
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• pp.129-132
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• 2003

그리드와 같은 대규모 컴퓨팅 자원이 연결되어 이용되는 분산처리 환경에서 가장 중요한 기능중에 하나가 자원 탐색(lookup)기능이다. 찾기 기능은 미리 정해진 형태로 지원을 등록하고 이 정보를 중앙에서 관리하는 단일기관이나 소규모로 분산된 컴퓨팅 자원을 공유하는 환경에서는 문제되지 않는다. 그러나 임의로 가입과 탈퇴가 가능하고 대규모로 자원이 연결된 그리드 환경에서는 빠른 자원 탐색이 성능의 기본 요소가 된다. 이 논문에서 그리드 환경에서 자원탐색 방법으로 분산형 자원탐색 방법인 Chord시스템을 이용하고 자원탐색방법을 신뢰성 있게 유지하기 위해 메시지큐를 이용하여 시스템을 모델링하고 시스템을 설계한 내용을 기술하였다. 이를 위하여 Chord시스템에 Message Queue System을 통합하여 응용 프로그램에서 요청한 자원탐색을 메시지 큐에 저장하여 노드가 failure되거나 네트워크가 분할이 되더라도 메시지 큐에 저장된 내용을 바탕으로 일관성을 유지할 수 있는 방법을 제시하였다.

• Journal of Korea Spatial Information System Society
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• v.10 no.2
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• pp.35-48
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• 2008

In this paper, we propose a Dynamic Heuristic to reduce the number of node accesses and improve quality of path in the client-based navigation service. The Dynamic Heuristic is to use heuristic data from server that is calculated with traffic data. The server-based navigation service provides a path searched on server and transmits it to client, but we propose that server only provide heuristic data to client. The proposed client searches a path with heuristic transmitted data from server. We present a new algorithm for using Dynamic Heuristic in the path-finding. The algorithm bases Grid Based Path-Finding, and has minimum speed data of edges in grid. It removes several grids whose minimum speed is less than limited speed.

• Journal of KIISE
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• v.43 no.9
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• pp.1026-1033
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• 2016

Path-finding on a grid map is a problem generally addressed in the fields of robotics, intelligent agents, and computer games. As technology advances, virtual game worlds tend to be represented more accurately and more realistically, resulting in an excessive increase in the number of grid tiles and in path-search time. In this study, we propose a path-finding algorithm that allows a prompt response to real-time queries by constructing a reduced state space and by precomputing all possible paths in an offline preprocessing stage. In the preprocessing stage, we vertically decompose free space on the grid map, construct a connectivity graph where nodes are the decomposed regions, and store paths between all pairs of nodes in matrix form. In the real-time query stage, we first find the nodes containing the query points and then retrieve the corresponding stored path. The proposed method is simulated for a set of maps that has been used as a benchmark for grid-based path finding. The simulation results show that the state space and the search time decrease significantly.

• Proceedings of the Korean Information Science Society Conference
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• 2010.06b
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• pp.518-522
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• 2010

그리드 기반 대규모 신약후보물질탐색환경에서는 (1) 대규모의 도킹 작업을 그리드 상에 제출한 후 이들을 지속적으로 관리하고, (2) 실행된 각 작업들은 동시에 그리드 스토리지 및 메타데이터 카탈로그 서비스에 접근한다. 우리는 위의 두 부분에서 성능의 개선이 필요함을 발견하였다. (1)의 과정에서 제출된 작업의 상태 정보를 얻기 위해 그리드 스케쥴러를 사용하던 기존의 방식은 대규모 작업 제출에 의한 부하 문제로 정확한 정보를 신속하게 얻는 데 어려움이 있어 제출된 작업의 효율성이 떨어지는 문제가 있었다. 그리고 (2)의 과정에서는 동시에 실행된 대규모 작업들의 접근 요청이 그리드 스토리지 및 메타데이터 카탈로그 서비스에 집중되면서 이로 인해 성능 저하가 일어났다. 본 연구에서는 기존 환경에서 찾아낸 위의 두 가지 주요 부분에서 발견한 성능 이슈를 밝히고 또 이에 대한 해결 방법을 제시한다.

• Journal of Korea Spatial Information System Society
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• v.11 no.4
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• pp.39-46
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• 2009

Generally, Path-finding algorithms which use heuristic function may occur a problem of the increase of exploring cost in case of that there is no way determined by heuristic function or there are 2 way more which have almost same cost. In this paper, we propose an abstract graph for path-finding with dynamic information. The abstract graph is a simple graph as real road network is abstracted. The abstract graph is created by fixed-size cells and real road network. Path-finding with the abstract graph is composed of two step searching, path-finding on the abstract graph and on the real road network. We performed path-finding algorithm with the abstract graph against A* algorithm based on fixed-size cells on road network that consists of 106,254 edges. In result of evaluation of performance, cost of exploring in path-finding with the abstract graph is about 3~30% less than A* algorithm based on fixed-size cells. Quality of path in path-finding with the abstract graph is, However, about 1.5~6.6% more than A* algorithm based on fixed-size cells because edges eliminated are not candidates for path-finding.

• Journal of the Korea Society of Computer and Information
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• v.20 no.1
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• pp.85-92
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• 2015

As computer game maps get more elaborate, path-finding by using $A^*$ algorithm in grid-based game maps becomes bottlenecks of the overall game performance. It is because the search space becomes large as the number of nodes increases with detailed representation in cells. In this paper we propose an efficient pathfinding method in which the computer game maps in a regular grid is converted into the polygon-based representation of the list of vertices and then the visibility information about vertices of polygons can be utilized. The conversion to the polygon-based map does not give any effect to the real-time query process because it is preprocessed offline. The number of visited nodes during search can be reduced dramatically by designing heuristics using visibility information of vertices that make the accuracy of the estimation enhanced. Through simulations, we show that the proposed methods reduce the search space and the search time effectively while maintaining the advantages of the grid-based method.

• The Journal of Korean Association of Computer Education
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• v.13 no.1
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• pp.53-64
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• 2010

In this paper, we tried to enable a mobile device as a resource to access to mobile grid networks. By advanced Internet techniques, the use of mobile devices has been rapidly increased. Some researches in mobile grid computing tried to combine grid computing with mobile devices. However, according to intrinsic properties of mobile environments, mobile devices have many considerations, such as mobility management, disconnected operation, device heterogeneity, service discovery, resource sharing, security, and so on. To solve these problems, there are two trends for mobile grid computing: a proxy-based mobile grid architecture and an agent-based mobile grid architecture. We focus on a proxy-based mobile grid architecture with IP-paging, which can easily manage idle mobile devices and grid resource status information. Also, we use SIP(Session Initiation Protocol)to support mobility management, mobile grid services. We manage variation of mobile device state and power by paging cache. Finally, using the candidate set and the reservation set of resources, we perform task migration. The performance evaluation by simulation, shows improvement of efficiency and stability during execution.

• Proceedings of the Korea Information Processing Society Conference
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• 2013.05a
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• pp.1077-1080
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• 2013

최근 소프트웨어는 네트워크를 이용한 서비스가 대부분이다. 그 중 그리드 딜리버리는 서버/클라이언트 모델에서 서버의 부담을 줄이기 위해 개발된 서비스다. 그리드 딜리버리는 사용자의 자원을 이용해 서비스를 원활하게 제공하는 방법으로 충분히 악용할 수 있다. 그러므로 이 논문은 악용되고 있는 그리드 딜리버리를 탐색하는 방법을 제안한다. 제안하는 방법은 모니터링 도구를 통해 모든 프로세스의 네트워크 자원을 감시한다. 그리고 네트워크가 사용되는 프로세스를 그리드 딜리버리로 추정하는 방법이다. 제안 방법은 두 단계로 나뉘어 진행된다. 처음으로 네트워크 자원을 사용하는 프로세스를 후보로 뽑아낸다. 두 번째로 이전 단계의 후보에 필터링을 적용해 그리드 딜리버리로 의심되는 프로세스를 찾아낸다. 이 논문에서는 제안하는 방법으로 실제 그리드 딜리버리 프로세스가 검출되는 것을 보임으로 제안하는 방법이 유효함을 보인다.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• v.9 no.2
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• pp.137-141
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• 2005

Optimal path search algorithm should consider traffic flows of the roads as well as the distance between a departure and destination, The existing path search algorithms, however, usually don't apply the continuously changed traffic flows. In this paper, we propose a new optimal path search algorithm. the algorithm takes the current flows into consideration in order to reduce the cost to get destination. It decomposes the road networks into Fixed Grid to get variable heuristics. We also carry out the experiments with Dijkstra and $A^*$ algorithm in terms of the execution time, the number of node accesses and the accuracy of path. The results obtained from the experimental tests show the proposed algorithm outperforms the others. The algorithm is highly expected to be useful in a advanced telematics systems.

• KIPS Transactions on Software and Data Engineering
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• v.6 no.12
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• pp.565-572
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• 2017

Traditional method for time series analysis, autoregressive integrated moving average (ARIMA) allows to mine significant patterns from the past observations using autocorrelation and to forecast future sequences. However, Korean baseball games do not have regular intervals to analyze relationship among the past attendance observations. To address this issue, we propose artificial neural network (ANN) based attendance prediction model using various measures including performance, team characteristics and social influences. We optimized ANNs using grid search to construct optimal model for regression problem. The evaluation shows that the optimal and ensemble model outperform the baseline model, linear regression model.