2012-02-01

# Shortest paths in time-dependent fifo networks

## Publication

### Publication

*Algorithmica , Volume 62 - Issue 1-2 p. 416- 435*

In this paper, we study the time-dependent shortest paths problem for two types of time-dependent FIFO networks. First, we consider networks where the availability of links, given by a set of disjoint time intervals for each link, changes over time. Here, each interval is assigned a non-negative real value which represents the travel time on the link during the corresponding interval. The resulting shortest path problem is the time-dependent shortest path problem for availability intervals ( $\mathcal TDSP - \mathrm int $ ), which asks to compute all shortest paths to any (or all) destination node(s) d for all possible start times at a given source node s. Second, we study time-dependent networks where the cost of using a link is given by a non-decreasing piece-wise linear function of a real-valued argument. Here, each piece-wise linear function represents the travel time on the link based on the time when the link is used. The resulting shortest paths problem is the time-dependent shortest path problem for piece-wise linear functions ( $TDSP lin$ ) which asks to compute, for a given source node s and destination d, the shortest paths from s to d, for all possible starting times. We present an algorithm for the $\mathcal TDSP - mathrm $ problem that runs in time O((F d +γ)(|E|+|V|log∈|V|)) where F d is the output size (i.e., number of linear pieces needed to represent the earliest arrival time function to d) and γ is the input size (i.e., number of linear pieces needed to represent the local earliest arrival time functions for all links in the network). We then solve the $\mathcal TDSP - mathrm int $ problem in O(λ(|E|+|V|log∈|V|)) time by reducing it to an instance of the $\mathcal TDSP - \mathrm lin $ problem. Here, λ denotes the total number of availability intervals in the entire network. Both methods improve significantly on the previously known algorithms.

Additional Metadata | |
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Keywords | Algorithms, Earliest arrival time, FIFO property, Shortest paths, Time-dependent networks |

Persistent URL | dx.doi.org/10.1007/s00453-010-9461-6 |

Journal | Algorithmica |

Citation |
Dehne, F, Omran, M.T. (Masoud T.), & Sack, J.-R. (2012). Shortest paths in time-dependent fifo networks.
Algorithmica, 62(1-2), 416–435. doi:10.1007/s00453-010-9461-6 |