There are a lot of studies about shortest path algorithms. They are usually applied to graphs. However, there is little study of maze images by image processing techniques. In this paper, the shortest path algorithms,...
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There are a lot of studies about shortest path algorithms. They are usually applied to graphs. However, there is little study of maze images by image processing techniques. In this paper, the shortest path algorithms, Dijkstra's and A* search algorithms, have been examined in maze images in terms of a search time. Furthermore, we have proposed a method to apply a thinning technique to maze images in order to solve a maze more quickly.
In this paper, we address the problem of finding the K best paths connecting a given pair of nodes in a directed graph with arbitrary lengths. We introduce an algorithm to determine the K best paths in order of length...
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In this paper, we address the problem of finding the K best paths connecting a given pair of nodes in a directed graph with arbitrary lengths. We introduce an algorithm to determine the K best paths in order of length when repeat nodes in the paths are allowed. We obtain an O(m+n log n+K(n+logK)) time and O(K+m) space algorithm to implicitly determine the K shortestpaths in a directed graph with n nodes and m arcs. Empirical results where the algorithm was used to compute one hundred million paths in USA road networks are reported. A non-trivial modification of the previous algorithm is performed obtaining an O(k(1) (nm + log k(1))) time method to compute paths without repeat nodes and to answer the next question: how many paths k(1) in practice are needed to identify K simple paths using the previous algorithm? We find that the response is usually O(K) based on an experiment computing one million paths in USA road networks. The determination of a theoretical tight bound on k1 remains as an open problem.
The impact of an increasing share of electric vehicles (EVs) is not fully known. Issues related to engine and battery point out that drivers of EVs may consider different route choices in order to take advantage of en...
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ISBN:
(纸本)9781509018901
The impact of an increasing share of electric vehicles (EVs) is not fully known. Issues related to engine and battery point out that drivers of EVs may consider different route choices in order to take advantage of energy recovery by regenerative braking, for instance. Because not only travel time but also energy consumption may matter, this work proposes a bi-objective traffic assignment method that computes equilibrium flows in scenarios with a mixed population of vehicles, considering physical aspects and energy recovery. We present two methods of route choice for EVs and propose a bi-objective shortestpath algorithm for them. Experiments show a small increase in travel time in congested scenarios, compensated by an expressive decrease in energy consumption in real-world networks. In uncongested scenarios, the travel time remains while the energy consumption decreases.
We propose an identity-aware multi-object tracker based on the solution path algorithm. Our tracker not only produces identity-coherent trajectories based on cues such as face recognition, but also has the ability to ...
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ISBN:
(纸本)9781467388528
We propose an identity-aware multi-object tracker based on the solution path algorithm. Our tracker not only produces identity-coherent trajectories based on cues such as face recognition, but also has the ability to pinpoint potential tracking errors. The tracker is formulated as a quadratic optimization problem with l_0 norm constraints, which we propose to solve with the solution path algorithm. The algorithm successively solves the same optimization problem but under different l_p norm constraints, where p gradually decreases from 1 to 0. Inspired by the success of the solution path algorithm in various machine learning tasks, this strategy is expected to converge to a better local minimum than directly minimizing the hardly solvable l_0 norm or the roughly approximated l_1 norm constraints. Furthermore, the acquired solution path complies with the "decision making process" of the tracker, which provides more insight to locating potential tracking errors. Experiments show that not only is our proposed tracker effective, but also the solution path enables automatic pinpointing of potential tracking failures, which can be readily utilized in an active learning framework to improve identity-aware multi-object tracking.
The problem of corridor location can be found in a number of fields including power transmission, highways, and pipelines. It involves the placement of a corridor or rights-of-way that traverses a landscape starting a...
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The problem of corridor location can be found in a number of fields including power transmission, highways, and pipelines. It involves the placement of a corridor or rights-of-way that traverses a landscape starting at an origin and ending at a destination. Since most systems are subject to environmental review, it is important to generate competitive, but different alternatives. This paper addresses the problem of generating efficient, spatially different alternatives to the corridor location problem. We discuss the weaknesses in current models and propose a new approach which is designed to overcome many of these problems. We present an application of this model to a real landscape and compare the results to past work. Overall, the new model called the multi-gateway shortestpath problem can generate a wide variety of efficient alignments, which eclipse what could be generated by past work.
We propose to classify the power of algorithms by the complexity of the problems that they can be used to solve. Instead of restricting to the problem a particular algorithm was designed to solve explicitly, however, ...
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ISBN:
(纸本)9781510813311
We propose to classify the power of algorithms by the complexity of the problems that they can be used to solve. Instead of restricting to the problem a particular algorithm was designed to solve explicitly, however, we include problems that, with polynomial overhead, can be solved 'implicitly' during the algorithm's execution. For example, we allow to solve a decision problem by suitably transforming the input, executing the algorithm, and observing whether a specific bit in its internal configuration ever switches during the execution. We show that the Simplex Method, the Network Simplex Method (both with Dantzig's original pivot rule), and the Successive shortestpath Algorithm are NP-mighty, that is, each of these algorithms can be used to solve any problem in NP. This result casts a more favorable light on these algorithms' exponential worstcase running times. Furthermore, as a consequence of our approach, we obtain several novel hardness results. For example, for a given input to the Simplex Algorithm, deciding whether a given variable ever enters the basis during the algorithm's execution and determining the number of iterations needed are both NP-hard problems. Finally, we close a long-standing open problem in the area of network flows over time by showing that earliest arrival flows are NP-hard to obtain.
Area of specialization supervisors dynamically configure available air traffic control resources so that air traffic can operate safely and efficiently. It is proposed to assist supervisors with this process by presen...
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Area of specialization supervisors dynamically configure available air traffic control resources so that air traffic can operate safely and efficiently. It is proposed to assist supervisors with this process by presenting them with a set of near-optimal and meaningfully different configuration advisories. To find such a set of advisories, a problem is defined that is equivalent to finding optimal and other near-optimal and distinct paths in a time-expanded graph. It is shown that this problem is nondeterministic polynomial-time hard, and then four algorithms are motivated and specified. One is a benchmark that solves the problem to optimality, one is a novel heuristic based on value iteration, and a third is a novel heuristic based on the A* algorithm. The fourth algorithm solves to optimality the lowest-cost paths problem relaxation of the problem. When used to solve realistic problem instances, the lowest-cost paths algorithm rarely returned feasible solutions and the optimal algorithm required excessive computation times, but the two novel heuristics found feasible and often optimal solutions in just a few seconds. The A* -based heuristic achieved lower computation times, whereas the value iteration-based heuristic typically found more advisories and lower-cost advisories.
There is a need for reliable and trustworthy public transport planner services. Mass transits are trying to solve problems as traffic jams or increasing pollution in densely populated city agglomerations. Passengers a...
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ISBN:
(纸本)9781479950812
There is a need for reliable and trustworthy public transport planner services. Mass transits are trying to solve problems as traffic jams or increasing pollution in densely populated city agglomerations. Passengers are looking for travel information on-line and companies providing public transport solutions often struggle with providing modern trip planner platforms. We address this problem by providing simple and easy to implement solution for shortestpaths computation in public transport network of any size. In first part of the paper we present our approach to building time-expanded graph model of public transportation network. We use a structure with multiple vertices within one stop identified by triple (stop, time, line) and edges with constant travel times. Second part introduces k-shortestpaths algorithm for created graph. We provide step by step explanation along with code samples. Average algorithm response time is around 1.5s for a public transport network of the size over 2800 stops. This is accepted query time for a web application. None additional speed-up techniques has been used to keep implementation and explanations simple and leaving room for further improvements. Algorithm has been successfully tested in Upper Silesian Industrial District (GOP) in cooperation with main public transport provider in the area (KZK GOP). This real instance is the biggest one in Poland and contains 370 lines and over 2800 stops.
The ever-increasing density in cloud computing users, services, and data centres has led to significant increases in network traffic and the associated energy consumed by its huge infrastructure, e.g. extra servers, s...
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ISBN:
(纸本)9781479952649
The ever-increasing density in cloud computing users, services, and data centres has led to significant increases in network traffic and the associated energy consumed by its huge infrastructure, e.g. extra servers, switches, routers, which is required to respond quickly and effectively to users requests. Transferring data, via a high bandwidth connection between data centres and cloud users, consumes even larger amounts of energy than just processing and storing the data on a cloud data centre, and hence producing high carbon dioxide emissions. This power consumption is highly significant when transferring data into a data centre located relatively far from the user's geographical location. Thus, it became high-necessity to locate the lowest energy consumption route between the user and the designated data centre, while making sure the user's requirements, e.g. response time, are met. This paper proposes a high-end autonomic meta-director framework to find the most energy efficient route to the green data centre by utilising the linear programming approach. The framework is, first, formalised by the situation calculus, and then evaluated against shortestpath algorithm with minimum number of nodes traversed.
The visibility model for establishing inter-satellite links is presented by analyzing the conditions of the shadow of the Earth,inter-satellite antenna visibility and restriction of distance *** into account of the in...
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ISBN:
(纸本)9781479946983
The visibility model for establishing inter-satellite links is presented by analyzing the conditions of the shadow of the Earth,inter-satellite antenna visibility and restriction of distance *** into account of the inter-satellite relationship and the connectivity criterion in the constellation,the judgment model for establishing constellation inter-satellite links is *** of static link and dynamic link are designed according to the process of establishing inter-satellite links for *** on the shortestpath algorithm and K-short path algorithm,a novel optimized algorithm model is ***,the simulation results show the stability and efficiency of the optimized algorithm model.
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