Module org.jgrapht.core

Package org.jgrapht.alg.shortestpath

Class BhandariKDisjointShortestPaths<V,E>

java.lang.Object

org.jgrapht.alg.shortestpath.BhandariKDisjointShortestPaths<V,E>

Type Parameters:

V - the graph vertex type

E - the graph edge type

All Implemented Interfaces:

KShortestPathAlgorithm<V,E>

public class BhandariKDisjointShortestPaths<V,E>
extends Object

An implementation of Bhandari algorithm for finding $K$ edge-disjoint shortest paths. The algorithm determines the $k$ edge-disjoint shortest simple paths in increasing order of weight. Weights can be negative (but no negative cycle is allowed). Only directed simple graphs are allowed.

The algorithm is running $k$ sequential Bellman-Ford iterations to find the shortest path at each step. Hence, yielding a complexity of $k$*O(Bellman-Ford).

• Bhandari, Ramesh 1999. Survivable networks: algorithms for diverse routing. 477. Springer. p. 46. ISBN 0-7923-8381-8.
• Iqbal, F. and Kuipers, F. A. 2015. Disjoint Paths in Networks . Wiley Encyclopedia of Electrical and Electronics Engineering. 1–11.

Author:

Assaf Mizrachi

Field Summary

Fields

Modifier and Type	Field	Description
protected Graph<V,E>	originalGraph
protected List<List<E>>	pathList
protected Graph<V,E>	workingGraph	Graph on which shortest paths are searched.

Constructor Summary

Constructors

Constructor	Description
BhandariKDisjointShortestPaths(Graph<V,E> graph)	Creates a new instance of the algorithm.

Method Summary

Modifier and Type	Method	Description
protected GraphPath<V,E>	calculateShortestPath(V startVertex, V endVertex)	Calculates the shortest paths for the current iteration.
List<GraphPath<V,E>>	getPaths(V startVertex, V endVertex, int k)	Returns the $k$ shortest simple paths in increasing order of weight.
protected void	transformGraph(List<E> previousPath)	Prepares the working graph for next iteration.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Details

workingGraph

protected Graph<V,E> workingGraph

Graph on which shortest paths are searched.

pathList

protected List<List<E>> pathList

originalGraph

protected Graph<V,E> originalGraph

Constructor Details

BhandariKDisjointShortestPaths

public BhandariKDisjointShortestPaths(Graph<V,E> graph)

Creates a new instance of the algorithm.

Parameters:

graph - graph on which shortest paths are searched.

Throws:

IllegalArgumentException - if the graph is null.

IllegalArgumentException - if the graph is undirected.

IllegalArgumentException - if the graph is not simple.

Method Details

transformGraph

protected void transformGraph(List<E> previousPath)

Prepares the working graph for next iteration. To be called from the second iteration and on so implementation may assume a preceding calculateShortestPath(V, V) call.

Parameters:

previousPath - the path found at the previous iteration.

calculateShortestPath

protected GraphPath<V,E> calculateShortestPath(V startVertex,
 V endVertex)

Calculates the shortest paths for the current iteration. Path is not final; rather, it is intended to be used in a "post-production" phase (see resolvePaths method).

Parameters:

startVertex - the start vertex

endVertex - the end vertex

Returns:

the shortest path between start and end vertices.

getPaths

public List<GraphPath<V,E>> getPaths(V startVertex,
 V endVertex,
 int k)

Returns the $k$ shortest simple paths in increasing order of weight.

Specified by:

getPaths in interface KShortestPathAlgorithm<V,E>

Parameters:

startVertex - source vertex of the calculated paths.

endVertex - target vertex of the calculated paths.

k - the number of shortest paths to return

Returns:

list of disjoint paths between the start vertex and the end vertex

Throws:

IllegalArgumentException - if the graph does not contain the startVertex or the endVertex

IllegalArgumentException - if the startVertex and the endVertex are the same vertices

IllegalArgumentException - if the startVertex or the endVertex is null