org.jgrapht.alg.linkprediction.HubPromotedIndexLinkPrediction Maven / Gradle / Ivy
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/*
* (C) Copyright 2020-2023, by Dimitrios Michail and Contributors.
*
* JGraphT : a free Java graph-theory library
*
* See the CONTRIBUTORS.md file distributed with this work for additional
* information regarding copyright ownership.
*
* This program and the accompanying materials are made available under the
* terms of the Eclipse Public License 2.0 which is available at
* http://www.eclipse.org/legal/epl-2.0, or the
* GNU Lesser General Public License v2.1 or later
* which is available at
* http://www.gnu.org/licenses/old-licenses/lgpl-2.1-standalone.html.
*
* SPDX-License-Identifier: EPL-2.0 OR LGPL-2.1-or-later
*/
package org.jgrapht.alg.linkprediction;
import java.util.HashSet;
import java.util.List;
import java.util.Objects;
import java.util.Set;
import org.jgrapht.Graph;
import org.jgrapht.Graphs;
import org.jgrapht.alg.interfaces.LinkPredictionAlgorithm;
import org.jgrapht.alg.util.Pair;
/**
* Predict links using the Hub Promoted Index.
*
*
* This is a local method which computes $s_{xy} =
* \frac{2|\Gamma(u)\cap\Gamma(v))|}{min(k(u),k(v))}$ where for a node $v$, $\Gamma(v)$ denotes the
* set of neighbors of $v$ and $k(v) = |\Gamma(v)|$ denotes the degree of $v$.
*
*
* See the following paper:
*
* - E. Ravasz, A.L. Somera, D.A. Mongru, Z.N. Oltvai, A.-L. Barabási, Science 297, 1553
* (2002)
*
*
* @param the graph vertex type
* @param the graph edge type
*
* @author Dimitrios Michail
*/
public class HubPromotedIndexLinkPrediction
implements LinkPredictionAlgorithm
{
private Graph graph;
/**
* Create a new prediction
*
* @param graph the input graph
*/
public HubPromotedIndexLinkPrediction(Graph graph)
{
this.graph = Objects.requireNonNull(graph);
}
@Override
public double predict(V u, V v)
{
int du = graph.outDegreeOf(u);
int dv = graph.outDegreeOf(v);
if (du == 0 || dv == 0) {
throw new LinkPredictionIndexNotWellDefinedException(
"Query vertex with zero neighbors", Pair.of(u, v));
}
List gu = Graphs.successorListOf(graph, u);
List gv = Graphs.successorListOf(graph, v);
Set intersection = new HashSet<>(gu);
intersection.retainAll(gv);
return (double) intersection.size() / Math.min(du, dv);
}
}