• 제목/요약/키워드: Shortest path algorithm

검색결과 438건 처리시간 0.032초

수송 네트워크에서 최대물동량경로 문제의 최적해법 (An Optimal Algorithm for Maximum Origin Destination Flow Path in the Transportation Network)

  • 성기석;박순달
    • 한국경영과학회지
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    • 제16권1호
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    • pp.1-12
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    • 1991
  • This paper studies an optimal algorithm for the Maximum Origin-Destination Flor Path (MODFP) in an acyclic transportation network. We define a Pseudo-Flow each are so that it can give an upper bound to the total flow of a given path. And using the K-th Shortest Path algorithm we obtain upper bound of MODF which is decreasing as the number of searched path grows. Computational Complexity of optimal algorithm is O(K + m) $n_{2}$), K being the total number of searched path. We proved that the problem complexity of finding MODFP in an acyclic network is NP-hard, showing that the-satisfiability problem can be polynomialy reduced to this problem. And we estimated the average of the number K as being (m/n)$^{1,08}$ Exp (0.00689gm) from the computational experiments.

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웹 사이트 탐색 알고리즘 비교분석 (Comparision and Analysis of Algorithm for web Sites Researching)

  • 김덕수;권영직
    • 한국산업정보학회논문지
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    • 제8권3호
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    • pp.91-98
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    • 2003
  • 무선 PDA.휴대폰을 통해 웹을 탐색하려는 이용자들은 인터페이스 상의 문제 때문에 어려움을 겪는다. 단지 그래픽을 문자로 바꾸거나 기호체계를 재구성한다고 해서 해결될 문제가 아니다. 심층 연계 구조를 통과하는 데에는 많은 시간이 걸리기 때문이다. 이러한 문제들을 해결하기 위해서 본 논문에서는 실시간의 최단경로를 제공하기 위하여 무선 웹 탐색을 자동적으로 개선시키는 Minimal Path 알고리즘을 제안한다. 본 논문의 결과 Minimal Path 알고리즘은 웹 이용자들에 대해 지름길을 제공해 주며, 링크의 숫자가 가장 짧았음을 알 수 있었다.

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무인 주행 차량의 주행 특성과 주행 시간을 고려한 경로 생성 및 주행 알고리즘 (Path Planning for the Shortest Driving Time Considering UGV Driving Characteristic and Driving Time and Its Driving Algorithm)

  • 노치범;김민호;이민철
    • 로봇학회논문지
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    • 제8권1호
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    • pp.43-50
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    • 2013
  • $A^*$ algorithm is a global path generation algorithm, and typically create a path using only the distance information. Therefore along the path, a moving vehicle is usually not be considered by driving characteristics. Deceleration at the corner is one of the driving characteristics of the vehicle. In this paper, considering this characteristic, a new evaluation function based path algorithm is proposed to decrease the number of driving path corner, in order to reduce the driving cost, such as driving time, fuel consumption and so on. Also the potential field method is applied for driving of UGV, which is robust against static and dynamic obstacle environment during following the generated path of the mobile robot under. The driving time and path following test was occurred by experiments based on a pseudo UGV, mobile robot in downscaled UGV's maximum and driving speed in corner. The experiment results were confirmed that the driving time by the proposed algorithm was decreased comparing with the results from $A^*$ algorithm.

목표지향적 강화학습 시스템 (Goal-Directed Reinforcement Learning System)

  • 이창훈
    • 한국인터넷방송통신학회논문지
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    • 제10권5호
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    • pp.265-270
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    • 2010
  • 강화학습(reinforcement learning)은 동적 환경과 시행-착오를 통해 상호 작용하면서 학습을 수행한다. 그러므로 동적 환경에서 TD-학습과 TD(${\lambda}$)-학습과 같은 강화학습 방법들은 전통적인 통계적 학습 방법보다 더 빠르게 학습을 할 수 있다. 그러나 제안된 대부분의 강화학습 알고리즘들은 학습을 수행하는 에이전트(agent)가 목표 상태에 도달하였을 때만 강화 값(reinforcement value)이 주어지기 때문에 최적 해에 매우 늦게 수렴한다. 본 논문에서는 미로 환경(maze environment)에서 최단 경로를 빠르게 찾을 수 있는 강화학습 방법(GORLS : Goal-Directed Reinforcement Learning System)을 제안하였다. GDRLS 미로 환경에서 최단 경로가 될 수 있는 후보 상태들을 선택한다. 그리고 나서 최단 경로를 탐색하기 위해 후보 상태들을 학습한다. 실험을 통해, GDRLS는 미로 환경에서 TD-학습과 TD(${\lambda}$)-학습보다 더 빠르게 최단 경로를 탐색할 수 있음을 알 수 있다.

상황인식 기반 지능형 최적 경로계획 (Intelligent Optimal Route Planning Based on Context Awareness)

  • 이현정;장용식
    • Asia pacific journal of information systems
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    • 제19권2호
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    • pp.117-137
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    • 2009
  • Recently, intelligent traffic information systems have enabled people to forecast traffic conditions before hitting the road. These convenient systems operate on the basis of data reflecting current road and traffic conditions as well as distance-based data between locations. Thanks to the rapid development of ubiquitous computing, tremendous context data have become readily available making vehicle route planning easier than ever. Previous research in relation to optimization of vehicle route planning merely focused on finding the optimal distance between locations. Contexts reflecting the road and traffic conditions were then not seriously treated as a way to resolve the optimal routing problems based on distance-based route planning, because this kind of information does not have much significant impact on traffic routing until a a complex traffic situation arises. Further, it was also not easy to take into full account the traffic contexts for resolving optimal routing problems because predicting the dynamic traffic situations was regarded a daunting task. However, with rapid increase in traffic complexity the importance of developing contexts reflecting data related to moving costs has emerged. Hence, this research proposes a framework designed to resolve an optimal route planning problem by taking full account of additional moving cost such as road traffic cost and weather cost, among others. Recent technological development particularly in the ubiquitous computing environment has facilitated the collection of such data. This framework is based on the contexts of time, traffic, and environment, which addresses the following issues. First, we clarify and classify the diverse contexts that affect a vehicle's velocity and estimates the optimization of moving cost based on dynamic programming that accounts for the context cost according to the variance of contexts. Second, the velocity reduction rate is applied to find the optimal route (shortest path) using the context data on the current traffic condition. The velocity reduction rate infers to the degree of possible velocity including moving vehicles' considerable road and traffic contexts, indicating the statistical or experimental data. Knowledge generated in this papercan be referenced by several organizations which deal with road and traffic data. Third, in experimentation, we evaluate the effectiveness of the proposed context-based optimal route (shortest path) between locations by comparing it to the previously used distance-based shortest path. A vehicles' optimal route might change due to its diverse velocity caused by unexpected but potential dynamic situations depending on the road condition. This study includes such context variables as 'road congestion', 'work', 'accident', and 'weather' which can alter the traffic condition. The contexts can affect moving vehicle's velocity on the road. Since these context variables except for 'weather' are related to road conditions, relevant data were provided by the Korea Expressway Corporation. The 'weather'-related data were attained from the Korea Meteorological Administration. The aware contexts are classified contexts causing reduction of vehicles' velocity which determines the velocity reduction rate. To find the optimal route (shortest path), we introduced the velocity reduction rate in the context for calculating a vehicle's velocity reflecting composite contexts when one event synchronizes with another. We then proposed a context-based optimal route (shortest path) algorithm based on the dynamic programming. The algorithm is composed of three steps. In the first initialization step, departure and destination locations are given, and the path step is initialized as 0. In the second step, moving costs including composite contexts into account between locations on path are estimated using the velocity reduction rate by context as increasing path steps. In the third step, the optimal route (shortest path) is retrieved through back-tracking. In the provided research model, we designed a framework to account for context awareness, moving cost estimation (taking both composite and single contexts into account), and optimal route (shortest path) algorithm (based on dynamic programming). Through illustrative experimentation using the Wilcoxon signed rank test, we proved that context-based route planning is much more effective than distance-based route planning., In addition, we found that the optimal solution (shortest paths) through the distance-based route planning might not be optimized in real situation because road condition is very dynamic and unpredictable while affecting most vehicles' moving costs. For further study, while more information is needed for a more accurate estimation of moving vehicles' costs, this study still stands viable in the applications to reduce moving costs by effective route planning. For instance, it could be applied to deliverers' decision making to enhance their decision satisfaction when they meet unpredictable dynamic situations in moving vehicles on the road. Overall, we conclude that taking into account the contexts as a part of costs is a meaningful and sensible approach to in resolving the optimal route problem.

Complete Time Algorithm for Stadium Construction Scheduling Problem

  • Lee, Sang-Un
    • 한국컴퓨터정보학회논문지
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    • 제20권9호
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    • pp.81-86
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    • 2015
  • This paper suggests heuristic algorithm with linear time complexity to decide the normal and optimal point at minimum loss/maximum profit maximum shortest scheduling problem with additional loss cost and bonus profit cost. This algorithm computes only the earliest ending time for each node. Therefore, this algorithm can be get the critical path and project duration within O(n) time complexity and reduces the five steps of critical path method to one step. The proposed algorithm can be show the result more visually than linear programming and critical path method. For real experimental data, the proposed algorithm obtains the same solution as linear programming more quickly.

덩굴망 통행패턴을 고려한 One-To-One 다경로알고리즘 (An One-To-One K-Shortest Path Algorithm Considering Vine Travel Pattern)

  • 이미영;유기윤;김정현;신성일
    • 대한교통학회지
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    • 제21권6호
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    • pp.89-99
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    • 2003
  • 회전제약(Turn Penalty and Prohibition)을 포함하는 방향성 그래프(Directed Graph)에서 두 지점(One-To-One)간 덩굴망(Vine)을 포함한 다수의 경로를 순차적으로 탐색하는 알고리즘(K-Shortest Path Algorithm)을 제안한다. 이를 위해 Yen이 제안한 다경로탐색알고리즘을 기반으로 교차로의 방향별 통행에서 발생되는 회전지체와 금지의 표현이 가능한 링크표지(Link-Labeled)탐색방식을 적용하는 기법을 개발한다. 사례연구를 통해 제안된 알고리즘은 교차로의 회전특성뿐만 아니라 U-Turn, P-Turn과 같은 덩굴망(Vine) 통행특성의 고려가 가능하며, 운전자의 인지비용(Perceived Cost)을 반영한 합리적인 대안경로(Reasonable Alternative Route)의 정보 제공 가능성을 입증했다.

유전자 알고리즘을 이용한 부재 절단 경로 최적화 (A Study on Cutting Path Optimization Using Genetic Algorithm)

  • 박주용;서정진
    • 한국해양공학회지
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    • 제23권6호
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    • pp.67-70
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    • 2009
  • Nesting and cutting path optimization have a great effect on the improvement of productivity in many industries such as shipbuilding, automotive, clothing, and so on. However, few researches have been carried out for the optimization of a cutting path algorithm. This study proposed a new method for cutting optimization using gravity center of cutting pieces and a genetic algorithm. The proposed method was tested for a sample plate including many different shapes of cutting pieces and compared to 2 other conventional methods. The test results showed that the new method had the shortest cutting path and the best effectiveness among the 3 methods.

A Possible Path per Link CBR Algorithm for Interference Avoidance in MPLS Networks

  • Sa-Ngiamsak, Wisitsak;Varakulsiripunth, Ruttikorn
    • 제어로봇시스템학회:학술대회논문집
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    • 제어로봇시스템학회 2004년도 ICCAS
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    • pp.772-776
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    • 2004
  • This paper proposes an interference avoidance approach for Constraint-Based Routing (CBR) algorithm in the Multi-Protocol Label Switching (MPLS) network. The MPLS network itself has a capability of integrating among any layer-3 protocols and any layer-2 protocols of the OSI model. It is based on the label switching technology, which is fast and flexible switching technique using pre-defined Label Switching Paths (LSPs). The MPLS network is a solution for the Traffic Engineering(TE), Quality of Service (QoS), Virtual Private Network (VPN), and Constraint-Based Routing (CBR) issues. According to the MPLS CBR, routing performance requirements are capability for on-line routing, high network throughput, high network utilization, high network scalability, fast rerouting performance, low percentage of call-setup request blocking, and low calculation complexity. There are many previously proposed algorithms such as minimum hop (MH) algorithm, widest shortest path (WSP) algorithm, and minimum interference routing algorithm (MIRA). The MIRA algorithm is currently seemed to be the best solution for the MPLS routing problem in case of selecting a path with minimum interference level. It achieves lower call-setup request blocking, lower interference level, higher network utilization and higher network throughput. However, it suffers from routing calculation complexity which makes it difficult to real task implementation. In this paper, there are three objectives for routing algorithm design, which are minimizing interference levels with other source-destination node pairs, minimizing resource usage by selecting a minimum hop path first, and reducing calculation complexity. The proposed CBR algorithm is based on power factor calculation of total amount of possible path per link and the residual bandwidth in the network. A path with high power factor should be considered as minimum interference path and should be selected for path setup. With the proposed algorithm, all of the three objectives are attained and the approach of selection of a high power factor path could minimize interference level among all source-destination node pairs. The approach of selection of a shortest path from many equal power factor paths approach could minimize the usage of network resource. Then the network has higher resource reservation for future call-setup request. Moreover, the calculation of possible path per link (or interference level indicator) is run only whenever the network topology has been changed. Hence, this approach could reduce routing calculation complexity. The simulation results show that the proposed algorithm has good performance over high network utilization, low call-setup blocking percentage and low routing computation complexity.

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On Finding an Optimal Departure Time in Time-Dependent Networks

  • Park, Chan-Kyoo;Lee, Sangwook;Park, Soondal
    • Management Science and Financial Engineering
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    • 제10권1호
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    • pp.53-75
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    • 2004
  • Most existing studies on time-dependent networks have been focused on finding a minimum delay path given a departure time at the origin. There, however, frequently happens a situation where users can select any departure time in a certain time interval and want to spend as little time as possible on traveling the networks. In that case. the delay spent on traveling networks depends on not only paths but also the actual departure time at the origin. In this paper, we propose a new problem in time-dependent networks whose objective is to find an optimal departure time given possible departure time interval at the origin. From the optimal departure time, we can obtain a path with minimum delay among all paths for possible departure times at the origin. In addition, we present an algorithm for finding an optimal departure time by enumerating trees which remain shortest path tree for a certain time interval.