com.graphhopper.routing.subnetwork

Class PrepareRoutingSubnetworks

java.lang.Object

com.graphhopper.routing.subnetwork.PrepareRoutingSubnetworks

public class PrepareRoutingSubnetworks
extends Object

Detects and marks 'subnetworks' with a dedicated subnetwork encoded value. Subnetworks are parts of the road network that are not connected to the rest of the network and that are below a certain size. These can be isolated nodes with no edges at all, but also small subnetworks which could be bugs in OSM data or 'islands' that are separated from the rest of the network because of some missing link, barrier or some closed road for example.

Sometimes there are also subnetworks that can be reached from the main network but not the other way around (or the opposite). For example this can be parking lots that can only be accessed by a single one-way road (a mapping error). These are called 'one-way subnetworks' and are marked using the same subnetwork encoded value, see #86. To find such one-way subnetworks it is important to search for strongly connected components on the directed graph and not do a simple connectivity check for one direction.

Note that it depends on the weighting whether or not edges belong to a subnetwork or not. For example if a weighting 'closes' a bridge to an island the island might become a subnetwork, but if the bridge was open it would belong to the main network. There can even be subnetworks that are due to turn restrictions.

We always run an edge-based connected component search, because this way we retrieve the edges (not the nodes) that belong to each component and can include turn restrictions as well. Node-based component search is faster, but since the subnetwork search goes relatively fast anyway using it has no real benefit.

Author:

Peter Karich, easbar

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static class	PrepareRoutingSubnetworks.PrepareJob

Constructor Summary

Constructors

Constructor and Description
PrepareRoutingSubnetworks(GraphHopperStorage ghStorage, List<PrepareRoutingSubnetworks.PrepareJob> prepareJobs)

Method Summary

Modifier and Type	Method and Description
int	doWork() Finds and marks all subnetworks according to setMinNetworkSize(int)
PrepareRoutingSubnetworks	setMinNetworkSize(int minNetworkSize) All components of the graph with less than 2*minNetworkSize directed edges (edge keys) will be marked as subnetworks.

Methods inherited from class java.lang.Object

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

Constructor Detail

PrepareRoutingSubnetworks

public PrepareRoutingSubnetworks(GraphHopperStorage ghStorage,
                                 List<PrepareRoutingSubnetworks.PrepareJob> prepareJobs)

Method Detail

setMinNetworkSize

public PrepareRoutingSubnetworks setMinNetworkSize(int minNetworkSize)

All components of the graph with less than 2*minNetworkSize directed edges (edge keys) will be marked as subnetworks. The biggest component will never be marked as subnetwork, even when it is below this size.

doWork

public int doWork()

Finds and marks all subnetworks according to setMinNetworkSize(int)

Returns:

the total number of marked edges