/*
* 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);
}
}
}
}