com.graphhopper.routing.subnetwork

Class EdgeBasedTarjanSCC

java.lang.Object

com.graphhopper.routing.subnetwork.EdgeBasedTarjanSCC

public class EdgeBasedTarjanSCC
extends Object

Edge-based version of Tarjan's algorithm to find strongly connected components on a directed graph. Compared to the more traditional node-based version that traverses the nodes of the graph this version works directly with the edges. This way its possible to take into account possible turn restrictions.

The algorithm is of course very similar to the node-based version and it might be possible to reuse some code between the two, but especially the version with an explicit stack needs different 'state' information and loops require some special treatment as well.

Author:

easbar

See Also:

TarjanSCC

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static class	EdgeBasedTarjanSCC.ConnectedComponents

Constructor Summary

Constructors

Constructor and Description
EdgeBasedTarjanSCC(Graph graph, BooleanEncodedValue accessEnc, TurnCostProvider turnCostProvider, boolean excludeSingleEdgeComponents)

Method Summary

Modifier and Type	Method and Description
static int	createEdgeKey(EdgeIteratorState edgeState, boolean reverse)
EdgeBasedTarjanSCC.ConnectedComponents	findComponents() Runs Tarjan's algorithm using an explicit stack.
EdgeBasedTarjanSCC.ConnectedComponents	findComponentsRecursive() Runs Tarjan's algorithm in a recursive way.
static int	getEdgeFromKey(int edgeKey)

Methods inherited from class java.lang.Object

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

Constructor Detail

EdgeBasedTarjanSCC

public EdgeBasedTarjanSCC(Graph graph,
                          BooleanEncodedValue accessEnc,
                          TurnCostProvider turnCostProvider,
                          boolean excludeSingleEdgeComponents)

Parameters:

excludeSingleEdgeComponents - if set to false components that only contain a single edge will not be returned when calling findComponents() or findComponentsRecursive(), which can be useful to save some memory.

turnCostProvider - used to check the turn costs between edges. if a turn has infinite costs the corresponding path will be ignored (edges that are only connected by a path with such a turn will not be considered to belong to the same component)

Method Detail

findComponentsRecursive

public EdgeBasedTarjanSCC.ConnectedComponents findComponentsRecursive()

Runs Tarjan's algorithm in a recursive way. Doing it like this requires a large stack size for large graphs, which can be set like `-Xss1024M`. Usually the version using an explicit stack (findComponents()) should be preferred. However, this recursive implementation is easier to understand.

findComponents

public EdgeBasedTarjanSCC.ConnectedComponents findComponents()

Runs Tarjan's algorithm using an explicit stack.

createEdgeKey

public static int createEdgeKey(EdgeIteratorState edgeState,
                                boolean reverse)

getEdgeFromKey

public static int getEdgeFromKey(int edgeKey)