org.jgrapht.alg

Class EdmondsKarpMaximumFlow<V,E>

java.lang.Object

org.jgrapht.alg.EdmondsKarpMaximumFlow<V,E>

public final class EdmondsKarpMaximumFlow<V,E>
extends Object

A flow network is a directed graph where each edge has a capacity and each edge receives a flow. The amount of flow on an edge can not exceed the capacity of the edge (note, that all capacities must be non-negative). A flow must satisfy the restriction that the amount of flow into a vertex equals the amount of flow out of it, except when it is a source, which "produces" flow, or sink, which "consumes" flow.

This class computes maximum flow in a network using Edmonds-Karp algorithm. Be careful: for large networks this algorithm may consume significant amount of time (its upper-bound complexity is O(VE^2), where V - amount of vertices, E - amount of edges in the network).

For more details see Andrew V. Goldberg's Combinatorial Optimization (Lecture Notes).

Field Summary

Fields

Modifier and Type	Field and Description
static double	DEFAULT_EPSILON Default tolerance.

Constructor Summary

Constructors

Constructor and Description
EdmondsKarpMaximumFlow(DirectedGraph<V,E> network) Constructs MaximumFlow instance to work with a copy of network.
EdmondsKarpMaximumFlow(DirectedGraph<V,E> network, double epsilon) Constructs MaximumFlow instance to work with a copy of network.

Method Summary

Methods

Modifier and Type	Method and Description
void	calculateMaximumFlow(V source, V sink) Sets current source to source, current sink to sink, then calculates maximum flow from source to sink.
V	getCurrentSink() Returns current sink vertex, or null if there was no calculateMaximumFlow calls.
V	getCurrentSource() Returns current source vertex, or null if there was no calculateMaximumFlow calls.
Map<E,Double>	getMaximumFlow() Returns maximum flow, that was calculated during last calculateMaximumFlow call, or null, if there was no calculateMaximumFlow calls.
Double	getMaximumFlowValue() Returns maximum flow value, that was calculated during last calculateMaximumFlow call, or null, if there was no calculateMaximumFlow calls.

Methods inherited from class java.lang.Object

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

Field Detail

DEFAULT_EPSILON

public static final double DEFAULT_EPSILON

Default tolerance.

See Also:

Constant Field Values

Constructor Detail

EdmondsKarpMaximumFlow

public EdmondsKarpMaximumFlow(DirectedGraph<V,E> network)

Constructs MaximumFlow instance to work with a copy of network. Current source and sink are set to null. If network is weighted, then capacities are weights, otherwise all capacities are equal to one. Doubles are compared using DEFAULT_EPSILON tolerance.

Parameters:

network - network, where maximum flow will be calculated

EdmondsKarpMaximumFlow

public EdmondsKarpMaximumFlow(DirectedGraph<V,E> network,
                      double epsilon)

Constructs MaximumFlow instance to work with a copy of network. Current source and sink are set to null. If network is weighted, then capacities are weights, otherwise all capacities are equal to one.

Parameters:

network - network, where maximum flow will be calculated

epsilon - tolerance for comparing doubles

Method Detail

calculateMaximumFlow

public void calculateMaximumFlow(V source,
                        V sink)

Sets current source to source, current sink to sink, then calculates maximum flow from source to sink. Note, that source and sink must be vertices of the network passed to the constructor, and they must be different.

Parameters:

source - source vertex

sink - sink vertex

getMaximumFlowValue

public Double getMaximumFlowValue()

Returns maximum flow value, that was calculated during last calculateMaximumFlow call, or null, if there was no calculateMaximumFlow calls.

Returns:

maximum flow value

getMaximumFlow

public Map<E,Double> getMaximumFlow()

Returns maximum flow, that was calculated during last calculateMaximumFlow call, or null, if there was no calculateMaximumFlow calls.

Returns:

read-only mapping from edges to doubles - flow values

getCurrentSource

public V getCurrentSource()

Returns current source vertex, or null if there was no calculateMaximumFlow calls.

Returns:

current source

getCurrentSink

public V getCurrentSink()

Returns current sink vertex, or null if there was no calculateMaximumFlow calls.

Returns:

current sink