Package it.unimi.dsi.webgraph.algo

Class GeometricCentralities

java.lang.Object
it.unimi.dsi.webgraph.algo.GeometricCentralities
public class GeometricCentralities
extends Object
Computes exactly a set of positive geometric centralitites (more precisely, closeness, Lin's, harmonic and exponential centrality) and the number of reachable nodes using multiple parallel breadth-first visits. Terminal nodes will have closeness centrality equal to zero and Lin's centrality equal to one. A survey about geometric centralities can be found “Axioms for centrality”, by Paolo Boldi and Sebastiano Vigna, Internet Math., 10(3-4):222−262, 2014. Explicit definitions can be found here.

Note that usually one is interested in the negative version of a centrality measure, that is, the version that depends on the incoming arcs. This class can compute only positive centralities: if you are interested (as it usually happens) in the negative version, you must pass to this class the transpose of the graph.

Every visit is independent and is carried out by a separate thread. The only contention point is the update of the array accumulating the betweenness score, which is negligible. The downside is that running on k cores requires approximately k times the memory of the sequential algorithm, as only the graph and the betweenness array will be shared.

To use this class you first create an instance, and then invoke compute(). After that, you can peek at the fields closeness, lin, harmonic, exponential and reachable.

  • Field Summary

    Fields
    Modifier and Type Field Description
    double alpha
    The α parameter for exponential centrality: you can modify this field before calling compute() (its default value is 0.5).
    double[] closeness
    Closeness centrality.
    static double DEFAULT_ALPHA
    The default value for alpha.
    double[] exponential
    Exponential centrality.
    double[] harmonic
    Harmonic centrality.
    double[] lin
    Lin's centrality.
    protected AtomicInteger nextNode
    The next node to be visited.
    long[] reachable
    Number of reachable nodes.
    protected boolean stop
    Whether to stop abruptly the visiting process.

  • Constructor Summary

    Constructors
    Constructor Description
    GeometricCentralities​(ImmutableGraph graph)
    Creates a new class for computing positive geometric centralities and the number of reachable nodes, using as many threads as the number of available processors.
    GeometricCentralities​(ImmutableGraph graph, int requestedThreads)
    Creates a new class for computing positive geometric centralities and the number of reachable nodes.
    GeometricCentralities​(ImmutableGraph graph, int requestedThreads, ProgressLogger pl)
    Creates a new class for computing positive geometric centralities and the number reachable nodes.
    GeometricCentralities​(ImmutableGraph graph, ProgressLogger pl)
    Creates a new class for computing positive geometric centralities and the number of reachable nodes, using as many threads as the number of available processors.

  • Method Summary

    Modifier and Type Method Description
    void compute()
    Computes geometric centralities and the number of reachable nodes.
    static void main​(String[] arg)  

    Methods inherited from class java.lang.Object

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

  • Field Details

    • DEFAULT_ALPHA

      public static final double DEFAULT_ALPHA
      The default value for alpha.
      See Also:
      Constant Field Values

    • harmonic

      public final double[] harmonic
      Harmonic centrality.

    • closeness

      public final double[] closeness
      Closeness centrality.

    • lin

      public final double[] lin
      Lin's centrality.

    • exponential

      public final double[] exponential
      Exponential centrality.

    • alpha

      public double alpha
      The α parameter for exponential centrality: you can modify this field before calling compute() (its default value is 0.5).

    • reachable

      public final long[] reachable
      Number of reachable nodes.

    • nextNode

      protected final AtomicInteger nextNode
      The next node to be visited.

    • stop

      protected volatile boolean stop
      Whether to stop abruptly the visiting process.

  • Constructor Details

    • GeometricCentralities

      public GeometricCentralities​(ImmutableGraph graph, int requestedThreads, ProgressLogger pl)
      Creates a new class for computing positive geometric centralities and the number reachable nodes.
      Parameters:
      graph - a graph.
      requestedThreads - the requested number of threads (0 for Runtime.availableProcessors()).
      pl - a progress logger, or null.

    • GeometricCentralities

      public GeometricCentralities​(ImmutableGraph graph, ProgressLogger pl)
      Creates a new class for computing positive geometric centralities and the number of reachable nodes, using as many threads as the number of available processors.
      Parameters:
      graph - a graph.
      pl - a progress logger, or null.

    • GeometricCentralities

      public GeometricCentralities​(ImmutableGraph graph, int requestedThreads)
      Creates a new class for computing positive geometric centralities and the number of reachable nodes.
      Parameters:
      graph - a graph.
      requestedThreads - the requested number of threads (0 for Runtime.availableProcessors()).

    • GeometricCentralities

      public GeometricCentralities​(ImmutableGraph graph)
      Creates a new class for computing positive geometric centralities and the number of reachable nodes, using as many threads as the number of available processors.
      Parameters:
      graph - a graph.

  • Method Details