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78
Engineering the label-constrained shortest-path algorithm
, 2007
"... Abstract. We consider a generalization of the shortest-path problem: given an alphabet Σ, a graph G whose edges are weighted and Σ-labeled, and a regular language L ⊆ Σ∗, the L-constrained shortest-path problem consists of finding a shortest path p in G such that the concatenated labels along p form ..."
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Cited by 14 (2 self)
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Abstract. We consider a generalization of the shortest-path problem: given an alphabet Σ, a graph G whose edges are weighted and Σ-labeled, and a regular language L ⊆ Σ∗, the L-constrained shortest-path problem consists of finding a shortest path p in G such that the concatenated labels along p form a word of L. This definition allows to model, e. g., many traffic-planning problems. We present extensions of well-known speed-up techniques for the standard shortest-path problem, and con-duct an extensive experimental study of their performance with various networks and language constraints. Our results show that depending on the network type, both goal-directed and bidirectional search speed up the search considerably, while combinations of these do not. 1
Minimum Time and Minimum Cost Path Problems in Street Networks With Periodic Traffic Lights
, 2001
"... This paper investigates minimum time and minimum cost path problems in street networks regulated by periodic traffic lights. We show that the minimum time path problem is polynomially solvable. On the other hand, minimum cost path problems are generally NP-hard. Special, realistic, cases which ar ..."
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Cited by 12 (1 self)
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This paper investigates minimum time and minimum cost path problems in street networks regulated by periodic traffic lights. We show that the minimum time path problem is polynomially solvable. On the other hand, minimum cost path problems are generally NP-hard. Special, realistic, cases which are polynomially solvable are discussed.
Shortest paths in fifo time-dependent networks: theory and algorithms
, 2004
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Distributed Intelligence in Large Scale Traffic Simulations on Parallel Computers
- Collective Cognition: Mathematical Foundations of Distributed Intelligence, Santa Fe Institute
, 2002
"... Transportation systems can be seen as displaying meta-intelligence, in the sense that intelligent actors (travelers) conspire to make the system function as a whole. ..."
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Cited by 6 (2 self)
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Transportation systems can be seen as displaying meta-intelligence, in the sense that intelligent actors (travelers) conspire to make the system function as a whole.
Bidirectional A ∗ Search on Time-Dependent Road Networks
, 2010
"... The computation of point-to-point shortest paths on time-dependent road networks has a large practical interest, but very few works propose efficient algorithms for this problem. We propose a novel approach which tackles one of the main complications of route planning in time-dependent graphs, which ..."
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Cited by 6 (1 self)
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The computation of point-to-point shortest paths on time-dependent road networks has a large practical interest, but very few works propose efficient algorithms for this problem. We propose a novel approach which tackles one of the main complications of route planning in time-dependent graphs, which is the difficulty of using bidirectional search: since the exact arrival time at the destination is unknown, we start a backward search from the destination node using lower bounds on arc costs in order to restrict the set of nodes that have to be explored by the forward search. Our algorithm is based on A ∗ with landmarks (ALT); extensive computational results show that it is very effective in practice if we are willing to accept a small approximation factor, resulting in a speed-up of more than one order of magnitude with respect to Dijkstra’s algorithm while finding only slightly suboptimal solutions. The main idea presented here can also be generalized to other types of search algorithms.
On Distributed Time-Dependent Shortest Paths over Duty-Cycled Wireless Sensor Networks
"... Abstract—We revisit the shortest path problem in asynchronous duty-cycled wireless sensor networks, which exhibit time-dependent features. We model the time-varying link cost and distance from each node to the sink as periodic functions. We show that the time-cost function satisfies the FIFO propert ..."
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Cited by 5 (1 self)
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Abstract—We revisit the shortest path problem in asynchronous duty-cycled wireless sensor networks, which exhibit time-dependent features. We model the time-varying link cost and distance from each node to the sink as periodic functions. We show that the time-cost function satisfies the FIFO property, which makes the time-dependent shortest path problem solvable in polynomial-time. Using the β-synchronizer, we propose a fast distributed algorithm to build all-to-one shortest paths with polynomial message complexity and time complexity. The algorithm determines the shortest paths for all discrete times with a single execution, in contrast with multiple executions needed by previous solutions. We further propose an efficient distributed algorithm for time-dependent shortest path maintenance. The proposed algorithm is loop-free with low message complexity and low space complexity of O(maxdeg), where maxdeg is the maximum degree for all nodes. The performance of our solution is evaluated under diverse network configurations. The results suggest that our algorithm is more efficient than previous solutions in terms of message complexity and space complexity. I.
Fast paths in large-scale dynamic road networks
, 2007
"... Efficiently computing fast paths in large-scale dynamic road networks (where dynamic traffic information is known over a part of the network) is a practical problem faced by several traffic information service providers who wish to offer a realistic fast path computation to GPS terminal enabled vehi ..."
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Cited by 5 (1 self)
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Efficiently computing fast paths in large-scale dynamic road networks (where dynamic traffic information is known over a part of the network) is a practical problem faced by several traffic information service providers who wish to offer a realistic fast path computation to GPS terminal enabled vehicles. The heuristic solution method we propose is based on a highway hierarchy-based shortest path algorithm for static large-scale networks; we maintain a static highway hierarchy and perform each query on the dynamically evaluated network, using a simple algorithm to propagate available dynamic traffic information over a larger part of the road network. We provide computational results that show the efficacy of our approach.
ON FINDING PATHS AND FLOWS IN MULTICRITERIA, STOCHASTIC AND TIME-VARYING NETWORKS
"... This dissertation addresses two classes of network flow problems in networks with multiple, stochastic and time-varying attributes. The first problem class is concerned with providing routing instructions with the ability to make updated decisions as information about travel conditions is revealed f ..."
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Cited by 5 (0 self)
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This dissertation addresses two classes of network flow problems in networks with multiple, stochastic and time-varying attributes. The first problem class is concerned with providing routing instructions with the ability to make updated decisions as information about travel conditions is revealed for individual travelers in a transportation network. Three exact algorithms are presented for identifying all or a subset of the adaptive Pareto-optimal solutions with respect to the expected value of each criterion from each node to a desired destination for each departure time in the period of interest. The second problem class is concerned with problems of determining the optimal set of a priori path flows for evacuation in capacitated networks are addressed, where the time-dependent and stochastic nature of arc attributes and capacities inherent in these problems is explicitly considered. The concept of Safest Escape is formulated for developing egress instructions. An exact algorithm is proposed to determine the pattern of flow that maximizes the minimum path probability of successful arrival of supply at the sink While the Safest Escape problem considers stochastic, time-varying capacities,
