Package 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 required some special treatment as well (this was written when base graph could still have loops!).

Author:

easbar

See Also:

• TarjanSCC

Nested Class Summary

Nested Classes

Modifier and Type	Class	Description
static class	EdgeBasedTarjanSCC.ConnectedComponents
static interface	EdgeBasedTarjanSCC.EdgeTransitionFilter

Method Summary

Modifier and Type	Method	Description
static int	createEdgeKey(EdgeIteratorState edgeState, boolean reverse)
static EdgeBasedTarjanSCC.ConnectedComponents	findComponents(Graph graph, EdgeBasedTarjanSCC.EdgeTransitionFilter edgeTransitionFilter, boolean excludeSingleEdgeComponents)	Runs Tarjan's algorithm using an explicit stack.
static EdgeBasedTarjanSCC.ConnectedComponents	findComponentsForStartEdges(Graph graph, EdgeBasedTarjanSCC.EdgeTransitionFilter edgeTransitionFilter, com.carrotsearch.hppc.IntContainer edges)	Like findComponents(Graph, EdgeTransitionFilter, boolean), but the search only starts at the given edges.
static EdgeBasedTarjanSCC.ConnectedComponents	findComponentsRecursive(Graph graph, EdgeBasedTarjanSCC.EdgeTransitionFilter edgeTransitionFilter, boolean excludeSingleEdgeComponents)	Runs Tarjan's algorithm in a recursive way.

Methods inherited from class java.lang.Object

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

Method Details

findComponents

public static EdgeBasedTarjanSCC.ConnectedComponents findComponents(Graph graph,
 EdgeBasedTarjanSCC.EdgeTransitionFilter edgeTransitionFilter,
 boolean excludeSingleEdgeComponents)

Runs Tarjan's algorithm using an explicit stack.

Parameters:

edgeTransitionFilter - Only edge transitions accepted by this filter will be considered when we explore the graph. If a turn is not accepted 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)

excludeSingleEdgeComponents - if set to true components that only contain a single edge will not be returned when calling findComponents(com.graphhopper.storage.Graph, com.graphhopper.routing.subnetwork.EdgeBasedTarjanSCC.EdgeTransitionFilter, boolean) or findComponentsRecursive(), which can be useful to save some memory.

findComponentsForStartEdges

public static EdgeBasedTarjanSCC.ConnectedComponents findComponentsForStartEdges(Graph graph,
 EdgeBasedTarjanSCC.EdgeTransitionFilter edgeTransitionFilter,
 com.carrotsearch.hppc.IntContainer edges)

Like findComponents(Graph, EdgeTransitionFilter, boolean), but the search only starts at the given edges. This does not mean the search cannot expand to other edges, but this can be controlled by the edgeTransitionFilter. This method does not return single edge components (the excludeSingleEdgeComponents option is set to true).

findComponentsRecursive

public static EdgeBasedTarjanSCC.ConnectedComponents findComponentsRecursive(Graph graph,
 EdgeBasedTarjanSCC.EdgeTransitionFilter edgeTransitionFilter,
 boolean excludeSingleEdgeComponents)

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.

See Also:

• findComponents(Graph, EdgeTransitionFilter, boolean)

createEdgeKey

public static int createEdgeKey(EdgeIteratorState edgeState,
 boolean reverse)