edu.uci.ics.jung.algorithms.importance
Class WeightedNIPaths<V,E>

java.lang.Object
  edu.uci.ics.jung.algorithms.util.IterativeProcess
      edu.uci.ics.jung.algorithms.importance.AbstractRanker<V,E>
          edu.uci.ics.jung.algorithms.importance.WeightedNIPaths<V,E>

All Implemented Interfaces:

IterativeContext

public class WeightedNIPaths<V,E>
extends AbstractRanker<V,E>

This algorithm measures the importance of nodes based upon both the number and length of disjoint paths that lead to a given node from each of the nodes in the root set. Specifically the formula for measuring the importance of a node is given by: I(t|R) = sum_i=1_|P(r,t)|_{alpha^|p_i|} where alpha is the path decay coefficient, p_i is path i and P(r,t) is a set of maximum-sized node-disjoint paths from r to t.

This algorithm uses heuristic breadth-first search to try and find the maximum-sized set of node-disjoint paths between two nodes. As such, it is not guaranteed to give exact answers.

A simple example of usage is:

 WeightedNIPaths ranker = new WeightedNIPaths(someGraph,2.0,6,rootSet);
 ranker.evaluate();
 ranker.printRankings();
 

Author:

Scott White

See Also:

"Algorithms for Estimating Relative Importance in Graphs by Scott White and Padhraic Smyth, 2003"

Field Summary

static String

WEIGHTED_NIPATHS_KEY

Fields inherited from class edu.uci.ics.jung.algorithms.importance.AbstractRanker

edgeRankScores, vertexRankScores

Constructor Summary

WeightedNIPaths(DirectedGraph<V,E> graph, org.apache.commons.collections15.Factory<V> vertexFactory, org.apache.commons.collections15.Factory<E> edgeFactory, double alpha, int maxDepth, Set<V> priors)
Constructs and initializes the algorithm.

Method Summary

protected void	computeWeightedPathsFromSource(V root, int depth)
String	getRankScoreKey() Given a node, returns the corresponding rank score.
protected void	incrementRankScore(V v, double rankValue)
protected void	onFinalize(Object udc)
void	step() Evaluate the result of the current iteration.

Methods inherited from class edu.uci.ics.jung.algorithms.importance.AbstractRanker

assignDefaultEdgeTransitionWeights, finalizeIterations, getEdgeRankScore, getEdgeRankScore, getEdgeRankScores, getEdgeRankScores, getEdgeWeight, getEdgeWeights, getGraph, getRankings, getRankScores, getVertexCount, getVertexRankScore, getVertexRankScore, getVertexRankScores, getVertexRankScores, getVertices, initialize, isRankingEdges, isRankingNodes, normalizeEdgeTransitionWeights, normalizeRankings, printRankings, removeEdgeRankScore, removeEdgeRankScore, removeVertexRankScore, removeVertexRankScore, reset, setEdgeRankScore, setEdgeRankScore, setEdgeWeight, setEdgeWeights, setNormalizeRankings, setRemoveRankScoresOnFinalize, setVertexRankScore, setVertexRankScore

Methods inherited from class edu.uci.ics.jung.algorithms.util.IterativeProcess

done, evaluate, getDesiredPrecision, getIterations, getMaximumIterations, getPrecision, hasConverged, initializeIterations, relativePrecision, setDesiredPrecision, setMaximumIterations, setPrecision

Methods inherited from class java.lang.Object

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

Field Detail

WEIGHTED_NIPATHS_KEY

public static final String WEIGHTED_NIPATHS_KEY

See Also:

Constant Field Values

Constructor Detail

WeightedNIPaths

public WeightedNIPaths(DirectedGraph<V,E> graph,
                       org.apache.commons.collections15.Factory<V> vertexFactory,
                       org.apache.commons.collections15.Factory<E> edgeFactory,
                       double alpha,
                       int maxDepth,
                       Set<V> priors)

Constructs and initializes the algorithm.

Parameters:

graph - the graph whose nodes are being measured for their importance

alpha - the path decay coefficient (>= 1); 2 is recommended

maxDepth - the maximal depth to search out from the root set

priors - the root set (starting vertices)

Method Detail

incrementRankScore

protected void incrementRankScore(V v,
                                  double rankValue)

computeWeightedPathsFromSource

protected void computeWeightedPathsFromSource(V root,
                                              int depth)

step

public void step()

Description copied from class: IterativeProcess

Evaluate the result of the current iteration.

Specified by:

step in interface IterativeContext

Specified by:

step in class IterativeProcess

getRankScoreKey

public String getRankScoreKey()

Given a node, returns the corresponding rank score. This implementation of getRankScore assumes the decoration representing the rank score is of type MutableDouble.

Specified by:

getRankScoreKey in class AbstractRanker<V,E>

Returns:

the rank score for this node

onFinalize

protected void onFinalize(Object udc)

Overrides:

onFinalize in class AbstractRanker<V,E>