/*
* Copyright (c) 2003, the JUNG Project and the Regents of the University
* of California
* All rights reserved.
*
* This software is open-source under the BSD license; see either
* "license.txt" or
* http://jung.sourceforge.net/license.txt for a description.
*/
/*
* Created on Apr 21, 2004
*/
package edu.uci.ics.jung.algorithms.transformation;
import java.util.ArrayList;
import java.util.Collection;
import org.apache.commons.collections15.Factory;
import org.apache.commons.collections15.Predicate;
import edu.uci.ics.jung.graph.Graph;
import edu.uci.ics.jung.graph.Hypergraph;
import edu.uci.ics.jung.graph.KPartiteGraph;
/**
* Methods for creating a "folded" graph based on a k-partite graph or a
* hypergraph.
*
* <p>
* A "folded" graph is derived from a k-partite graph by identifying a partition
* of vertices which will become the vertices of the new graph, copying these
* vertices into the new graph, and then connecting those vertices whose
* original analogues were connected indirectly through elements of other
* partitions.
* </p>
*
* <p>
* A "folded" graph is derived from a hypergraph by creating vertices based on
* either the vertices or the hyperedges of the original graph, and connecting
* vertices in the new graph if their corresponding vertices/hyperedges share a
* connection with a common hyperedge/vertex.
* </p>
*
* @author Danyel Fisher
* @author Joshua O'Madadhain
*/
public class FoldingTransformer<V, E> {
/**
* Converts <code>g</code> into a unipartite graph whose vertex set is the
* vertices of <code>g</code>'s partition <code>p</code>. For vertices
* <code>a</code> and <code>b</code> in this partition, the resultant graph
* will include the edge <code>(a,b)</code> if the original graph contains
* edges <code>(a,c)</code> and <code>(c,b)</code> for at least one vertex
* <code>c</code>.
*
* <p>
* The vertices of the new graph are the same as the vertices of the
* appropriate partition in the old graph; the edges in the new graph are
* created by the input edge <code>Factory</code>.
* </p>
*
* <p>
* If there is more than 1 such vertex <code>c</code> for a given pair
* <code>(a,b)</code>, the type of the output graph will determine whether
* it will contain parallel edges or not.
* </p>
*
* <p>
* This function will not create self-loops.
* </p>
*
* @param <V>
* vertex type
* @param <E>
* input edge type
* @param g
* input k-partite graph
* @param p
* predicate specifying vertex partition
* @param graph_factory
* factory used to create the output graph
* @param edge_factory
* factory used to create the edges in the new graph
* @return a copy of the input graph folded with respect to the input
* partition
*/
public static <V, E> Graph<V, E> foldKPartiteGraph(KPartiteGraph<V, E> g,
Predicate<V> p, Factory<Graph<V, E>> graph_factory,
Factory<E> edge_factory) {
Graph<V, E> newGraph = graph_factory.create();
// get vertices for the specified partition
Collection<V> vertices = g.getVertices(p);
for (V v : vertices) {
newGraph.addVertex(v);
for (V s : g.getSuccessors(v)) {
for (V t : g.getSuccessors(s)) {
if (!vertices.contains(t) || t.equals(v)) {
continue;
}
newGraph.addVertex(t);
newGraph.addEdge(edge_factory.create(), v, t);
}
}
}
return newGraph;
}
/**
* Converts <code>g</code> into a unipartite graph whose vertices are the
* vertices of <code>g</code>'s partition <code>p</code>, and whose edges
* consist of collections of the intermediate vertices from other
* partitions. For vertices <code>a</code> and <code>b</code> in this
* partition, the resultant graph will include the edge <code>(a,b)</code>
* if the original graph contains edges <code>(a,c)</code> and
* <code>(c,b)</code> for at least one vertex <code>c</code>.
*
* <p>
* The vertices of the new graph are the same as the vertices of the
* appropriate partition in the old graph; the edges in the new graph are
* collections of the intermediate vertices <code>c</code>.
* </p>
*
* <p>
* This function will not create self-loops.
* </p>
*
* @param <V>
* vertex type
* @param <E>
* input edge type
* @param g
* input k-partite graph
* @param p
* predicate specifying vertex partition
* @param graph_factory
* factory used to create the output graph
* @return the result of folding g into unipartite graph whose vertices are
* those of the <code>p</code> partition of g
*/
public static <V, E> Graph<V, Collection<V>> foldKPartiteGraph(
KPartiteGraph<V, E> g, Predicate<V> p,
Factory<Graph<V, Collection<V>>> graph_factory) {
Graph<V, Collection<V>> newGraph = graph_factory.create();
// get vertices for the specified partition, copy into new graph
Collection<V> vertices = g.getVertices(p);
for (V v : vertices) {
newGraph.addVertex(v);
for (V s : g.getSuccessors(v)) {
for (V t : g.getSuccessors(s)) {
if (!vertices.contains(t) || t.equals(v)) {
continue;
}
newGraph.addVertex(t);
Collection<V> v_coll = newGraph.findEdge(v, t);
if (v_coll == null) {
v_coll = new ArrayList<V>();
newGraph.addEdge(v_coll, v, t);
}
v_coll.add(s);
}
}
}
return newGraph;
}
/**
* Creates a <code>Graph</code> which is an edge-folded version of
* <code>h</code>, where hyperedges are replaced by k-cliques in the output
* graph.
*
* <p>
* The vertices of the new graph are the same objects as the vertices of
* <code>h</code>, and <code>a</code> is connected to <code>b</code> in the
* new graph if the corresponding vertices in <code>h</code> are connected
* by a hyperedge. Thus, each hyperedge with <i>k</i> vertices in
* <code>h</code> induces a <i>k</i>-clique in the new graph.
* </p>
*
* <p>
* The edges of the new graph consist of collections of each hyperedge that
* connected the corresponding vertex pair in the original graph.
* </p>
*
* @param <V>
* vertex type
* @param <E>
* input edge type
* @param h
* hypergraph to be folded
* @param graph_factory
* factory used to generate the output graph
* @return a copy of the input graph where hyperedges are replaced by
* cliques
*/
public static <V, E> Graph<V, Collection<E>> foldHypergraphEdges(
Hypergraph<V, E> h,
Factory<Graph<V, Collection<E>>> graph_factory) {
Graph<V, Collection<E>> target = graph_factory.create();
for (V v : h.getVertices()) {
target.addVertex(v);
}
for (E e : h.getEdges()) {
ArrayList<V> incident = new ArrayList<V>(h.getIncidentVertices(e));
populateTarget(target, e, incident);
}
return target;
}
/**
* Creates a <code>Graph</code> which is an edge-folded version of
* <code>h</code>, where hyperedges are replaced by k-cliques in the output
* graph.
*
* <p>
* The vertices of the new graph are the same objects as the vertices of
* <code>h</code>, and <code>a</code> is connected to <code>b</code> in the
* new graph if the corresponding vertices in <code>h</code> are connected
* by a hyperedge. Thus, each hyperedge with <i>k</i> vertices in
* <code>h</code> induces a <i>k</i>-clique in the new graph.
* </p>
*
* <p>
* The edges of the new graph are generated by the specified edge factory.
* </p>
*
* @param <V>
* vertex type
* @param <E>
* input edge type
* @param h
* hypergraph to be folded
* @param graph_factory
* factory used to generate the output graph
* @param edge_factory
* factory used to create the new edges
* @return a copy of the input graph where hyperedges are replaced by
* cliques
*/
public static <V, E> Graph<V, E> foldHypergraphEdges(Hypergraph<V, E> h,
Factory<Graph<V, E>> graph_factory, Factory<E> edge_factory) {
Graph<V, E> target = graph_factory.create();
for (V v : h.getVertices()) {
target.addVertex(v);
}
for (E e : h.getEdges()) {
ArrayList<V> incident = new ArrayList<V>(h.getIncidentVertices(e));
for (int i = 0; i < incident.size(); i++) {
for (int j = i + 1; j < incident.size(); j++) {
target.addEdge(edge_factory.create(), incident.get(i),
incident.get(j));
}
}
}
return target;
}
/**
* Creates a <code>Graph</code> which is a vertex-folded version of
* <code>h</code>, whose vertices are the input's hyperedges and whose edges
* are induced by adjacent hyperedges in the input.
*
* <p>
* The vertices of the new graph are the same objects as the hyperedges of
* <code>h</code>, and <code>a</code> is connected to <code>b</code> in the
* new graph if the corresponding edges in <code>h</code> have a vertex in
* common. Thus, each vertex incident to <i>k</i> edges in <code>h</code>
* induces a <i>k</i>-clique in the new graph.
* </p>
*
* <p>
* The edges of the new graph are created by the specified factory.
* </p>
*
* @param <V>
* vertex type
* @param <E>
* input edge type
* @param <F>
* output edge type
* @param h
* hypergraph to be folded
* @param graph_factory
* factory used to generate the output graph
* @param edge_factory
* factory used to generate the output edges
* @return a transformation of the input graph whose vertices correspond to
* the input's hyperedges and edges are induced by hyperedges
* sharing vertices in the input
*/
public static <V, E, F> Graph<E, F> foldHypergraphVertices(
Hypergraph<V, E> h, Factory<Graph<E, F>> graph_factory,
Factory<F> edge_factory) {
Graph<E, F> target = graph_factory.create();
for (E e : h.getEdges()) {
target.addVertex(e);
}
for (V v : h.getVertices()) {
ArrayList<E> incident = new ArrayList<E>(h.getIncidentEdges(v));
for (int i = 0; i < incident.size(); i++) {
for (int j = i + 1; j < incident.size(); j++) {
target.addEdge(edge_factory.create(), incident.get(i),
incident.get(j));
}
}
}
return target;
}
/**
* Creates a <code>Graph</code> which is a vertex-folded version of
* <code>h</code>, whose vertices are the input's hyperedges and whose edges
* are induced by adjacent hyperedges in the input.
*
* <p>
* The vertices of the new graph are the same objects as the hyperedges of
* <code>h</code>, and <code>a</code> is connected to <code>b</code> in the
* new graph if the corresponding edges in <code>h</code> have a vertex in
* common. Thus, each vertex incident to <i>k</i> edges in <code>h</code>
* induces a <i>k</i>-clique in the new graph.
* </p>
*
* <p>
* The edges of the new graph consist of collections of each vertex incident
* to the corresponding hyperedge pair in the original graph.
* </p>
*
* @param h
* hypergraph to be folded
* @param graph_factory
* factory used to generate the output graph
* @return a transformation of the input graph whose vertices correspond to
* the input's hyperedges and edges are induced by hyperedges
* sharing vertices in the input
*/
public Graph<E, Collection<V>> foldHypergraphVertices(Hypergraph<V, E> h,
Factory<Graph<E, Collection<V>>> graph_factory) {
Graph<E, Collection<V>> target = graph_factory.create();
for (E e : h.getEdges()) {
target.addVertex(e);
}
for (V v : h.getVertices()) {
ArrayList<E> incident = new ArrayList<E>(h.getIncidentEdges(v));
populateTarget(target, v, incident);
}
return target;
}
/**
* @param target
* @param e
* @param incident
*/
private static <S, T> void populateTarget(Graph<S, Collection<T>> target,
T e, ArrayList<S> incident) {
for (int i = 0; i < incident.size(); i++) {
S v1 = incident.get(i);
for (int j = i + 1; j < incident.size(); j++) {
S v2 = incident.get(j);
Collection<T> e_coll = target.findEdge(v1, v2);
if (e_coll == null) {
e_coll = new ArrayList<T>();
target.addEdge(e_coll, v1, v2);
}
e_coll.add(e);
}
}
}
}