com.graphhopper.routing

Class AlternativeRoute

java.lang.Object

com.graphhopper.routing.AlternativeRoute

All Implemented Interfaces:

RoutingAlgorithm

public class AlternativeRoute
extends Object
implements RoutingAlgorithm

This class implements the alternative paths search using the "plateau" and partially the "penalty" method described in the following papers.

• Choice Routing Explanation - Camvit 2009: http://www.camvit.com/camvit-technical-english/Camvit-Choice-Routing-Explanation-english.pdf
• and refined in: Alternative Routes in Road Networks 2010: http://www.cs.princeton.edu/~rwerneck/papers/ADGW10-alternatives-sea.pdf
• other ideas 'Improved Alternative Route Planning', 2013: https://hal.inria.fr/hal-00871739/document
• via point 'storage' idea 'Candidate Sets for Alternative Routes in Road Networks', 2013: https://algo2.iti.kit.edu/download/s-csarrn-12.pdf
• Alternative route graph construction 2011: http://algo2.iti.kit.edu/download/altgraph_tapas_extended.pdf

Author:

Peter Karich

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static class	AlternativeRoute.AlternativeBidirSearch Helper class to find alternatives and alternatives for round trip.
static class	AlternativeRoute.AlternativeInfo
static class	AlternativeRoute.PlateauInfo

Constructor Summary

Constructors

Constructor and Description
AlternativeRoute(Graph graph, Weighting weighting, TraversalMode traversalMode)

Method Summary

Modifier and Type	Method and Description
List<AlternativeRoute.AlternativeInfo>	calcAlternatives(int from, int to) This method calculates best paths (alternatives) between 'from' and 'to', where maxPaths-1 alternatives are searched and they are only accepted if they are not too similar but close to the best path.
Path	calcPath(int from, int to) Calculates the best path between the specified nodes.
List<Path>	calcPaths(int from, int to) Calculates multiple possibilities for a path.
String	getName()
int	getVisitedNodes() Returns the visited nodes after searching.
void	setApproximation(WeightApproximator weightApproximator) This method sets the approximation used for the internal bidirectional A*.
void	setMaxExplorationFactor(double explorationFactor) This method sets the graph exploration percentage for alternative paths.
void	setMaxPaths(int maxPaths) Specifies how many paths (including the optimal) are returned.
void	setMaxShareFactor(double maxShareFactor) This parameter is used to avoid alternatives too similar to the best path.
void	setMaxVisitedNodes(int numberOfNodes) Limit the search to numberOfNodes.
void	setMaxWeightFactor(double maxWeightFactor) Increasing this factor results in returning more alternatives.
void	setMinPlateauFactor(double minPlateauFactor) This method sets the minimum plateau portion of every alternative path that is required.

Methods inherited from class java.lang.Object

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

Constructor Detail

AlternativeRoute

public AlternativeRoute(Graph graph,
                        Weighting weighting,
                        TraversalMode traversalMode)

Method Detail

setApproximation

public void setApproximation(WeightApproximator weightApproximator)

This method sets the approximation used for the internal bidirectional A*.

setMaxVisitedNodes

public void setMaxVisitedNodes(int numberOfNodes)

Description copied from interface: RoutingAlgorithm

Limit the search to numberOfNodes. See #681

Specified by:

setMaxVisitedNodes in interface RoutingAlgorithm

setMaxWeightFactor

public void setMaxWeightFactor(double maxWeightFactor)

Increasing this factor results in returning more alternatives. E.g. if the factor is 2 than all alternatives with a weight 2 times longer than the optimal weight are return. (default is 1)

setMaxShareFactor

public void setMaxShareFactor(double maxShareFactor)

This parameter is used to avoid alternatives too similar to the best path. Specify 0.5 to force a same paths of maximum 50%. The unit is the 'weight' returned in the Weighting.

setMinPlateauFactor

public void setMinPlateauFactor(double minPlateauFactor)

This method sets the minimum plateau portion of every alternative path that is required.

setMaxExplorationFactor

public void setMaxExplorationFactor(double explorationFactor)

This method sets the graph exploration percentage for alternative paths. Default for bidirectional A* is 0.8 (80%). Specify a higher value to get more alternatives (especially if maxWeightFactor is higher than 1.5) and a lower value to improve query time but reduces the possibility to find alternatives.

setMaxPaths

public void setMaxPaths(int maxPaths)

Specifies how many paths (including the optimal) are returned. (default is 2)

calcAlternatives

public List<AlternativeRoute.AlternativeInfo> calcAlternatives(int from,
                                                               int to)

This method calculates best paths (alternatives) between 'from' and 'to', where maxPaths-1 alternatives are searched and they are only accepted if they are not too similar but close to the best path.

calcPath

public Path calcPath(int from,
                     int to)

Description copied from interface: RoutingAlgorithm

Calculates the best path between the specified nodes.

Specified by:

calcPath in interface RoutingAlgorithm

Returns:

the path. Call the method found() to make sure that the path is valid.

calcPaths

public List<Path> calcPaths(int from,
                            int to)

Description copied from interface: RoutingAlgorithm

Calculates multiple possibilities for a path.

Specified by:

calcPaths in interface RoutingAlgorithm

See Also:

RoutingAlgorithm.calcPath(int, int)

getName

public String getName()

Specified by:

getName in interface RoutingAlgorithm

Returns:

name of this algorithm

getVisitedNodes

public int getVisitedNodes()

Description copied from interface: RoutingAlgorithm

Returns the visited nodes after searching. Useful for debugging.

Specified by:

getVisitedNodes in interface RoutingAlgorithm