edu.upc.dama.dex.algorithms
Class SinglePairShortestPathDijkstra

java.lang.Object
  edu.upc.dama.dex.tasks.Task
      edu.upc.dama.dex.tasks.CompositeTask
          edu.upc.dama.dex.algorithms.ShortestPath
              edu.upc.dama.dex.algorithms.SinglePairShortestPath
                  edu.upc.dama.dex.algorithms.SinglePairShortestPathDijkstra

All Implemented Interfaces:

Algorithm

public class SinglePairShortestPathDijkstra
extends SinglePairShortestPath

This class can be used to solve the single-pair shortest path problem in a weighted graph.

Concretely, it consists in finding a path between two nodes with the condition that the sum of the weights of the edges which belong to the path is minimized. This implementation is based on the Dijkstra algorithm.

It is possible to set some restrictions after constructing a new instance of this class and before running it in order to limit the results. Those restrictions are:

• The maximum hops while traversing the graph in order to find the path, that is, the maximum depth of the graph traversal with the ShortestPath.setMaximumHops(int maxhops) method.
• The set of edge types which will be navigated through while traversing the graph in order to find the path, its navigation to know which direction has to be followed while traversing each edge and its attribute containing the edge weight. The method is SinglePairShortestPathDijkstra.addWeightedEdge(int edgetype, short navigation, long attributetype) for adding one edge type, its navigation and its attribute identifier.

Navigation

There are three kinds of edge navigation:

• Algorithm.NAVIGATION_FORWARD: Allows to forward traverse edges.
• Algorithm.NAVIGATION_BACKWARD: Allows to backward traverse edges.
• Algorithm.NAVIGATION_UNDIRECTED: Allows to traverse edges in both directions.

For each instance of this class, it is only allowed to run the algorithm once. After the execution, we can retrieve the following results:

• The cost, that is, the sum of the weights of the edges which belong to the path using the SinglePairShortestPathDijkstra.getCost() method.
• The shortest path as:
  • A list of ordered nodes using the SinglePairShortestPath.getPathAsNodes() method.
  • A list of ordered edges using the SinglePairShortestPath.getPathAsEdges() method.

Please, see edu.upc.dama.dex.algorithms for further information related to how to use this class.

NOTE: It is required to indicate the set of edge types before running this algorithm.

Author:

Sparsity Technologies

Field Summary

Fields inherited from interface edu.upc.dama.dex.algorithms.Algorithm

NAVIGATION_BACKWARD, NAVIGATION_FORWARD, NAVIGATION_UNDIRECTED

Constructor Summary

SinglePairShortestPathDijkstra(Graph graph, long source, long dest)
Creates a new instance of SinglePairShortestPathDijkstra.

Method Summary

void	addWeightedEdge(int edgetype, short navigation, long attributetype) Adds an edge type, its navigation and its attribute containing the weight in order to restrict the set of edge types allowed and their direction while traversing the graph to find the path.
void	close() Closes the instance.
java.lang.Double	getCost() Returns the cost, that is, the sum of the weights of the edges which belong to the path.
void	run() Runs the algorithm in order to solve the shortest path problem.

Methods inherited from class edu.upc.dama.dex.algorithms.SinglePairShortestPath

existsShortestPath, getPathAsEdges, getPathAsNodes

Methods inherited from class edu.upc.dama.dex.algorithms.ShortestPath

setMaximumHops

Methods inherited from class edu.upc.dama.dex.tasks.CompositeTask

cancel, execute, init

Methods inherited from class edu.upc.dama.dex.tasks.Task

main

Methods inherited from class java.lang.Object

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

Constructor Detail

SinglePairShortestPathDijkstra

public SinglePairShortestPathDijkstra(Graph graph,
                                      long source,
                                      long dest)

Creates a new instance of SinglePairShortestPathDijkstra. After creating this instance is required to indicate the set of edge types which will be navigated through while traversing the graph in order to find the path.

Parameters:

graph - Graph on which the path will be found.

source - The node identifier which identifies the source node at which the algorithm execution will start.

dest - The node identifier which identifies the destination node at which the algorithm execution will end.

Method Detail

addWeightedEdge

public void addWeightedEdge(int edgetype,
                            short navigation,
                            long attributetype)

Adds an edge type, its navigation and its attribute containing the weight in order to restrict the set of edge types allowed and their direction while traversing the graph to find the path. It is possible to add as many edge types as all the different edge types contained in the graph.

Parameters:

edgetype - The edge type to restrict the set of edges allowed while traversing the graph during the execution of this algorithm.

navigation - The direction that has to be followed while traversing each edge of the given edge type during the execution of this algorithm. It must be Algorithm.NAVIGATION_BACKWARD, Algorithm.NAVIGATION_FORWARD or Algorithm.NAVIGATION_UNDIRECTED.

attributetype - The attribute identifier of the given edge type which contains the weight value.

getCost

public java.lang.Double getCost()

Returns the cost, that is, the sum of the weights of the edges which belong to the path. If there isn't any shortest path found, it returns -1 .

Returns:

The sum of the weights of the edges which belong to the path.

close

public void close()

Description copied from class: ShortestPath

Closes the instance.

Once executed, the instance becomes invalid.

Specified by:

close in class ShortestPath

run

public void run()
         throws java.lang.Throwable

Description copied from class: ShortestPath

Runs the algorithm in order to solve the shortest path problem.

This method can be called only once.

Specified by:

run in class ShortestPath

Throws:

java.lang.Throwable