/**
* Copyright (C) 2010-2017 Gordon Fraser, Andrea Arcuri and EvoSuite
* contributors
*
* This file is part of EvoSuite.
*
* EvoSuite is free software: you can redistribute it and/or modify it
* under the terms of the GNU Lesser General Public License as published
* by the Free Software Foundation, either version 3.0 of the License, or
* (at your option) any later version.
*
* EvoSuite is distributed in the hope that it will be useful, but
* WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with EvoSuite. If not, see <http://www.gnu.org/licenses/>.
*/
package org.evosuite.graphs;
/* ==========================================
* JGraphT : a free Java graph-theory library
* ==========================================
*
* Project Info: http://jgrapht.sourceforge.net/
* Project Creator: Barak Naveh (http://sourceforge.net/users/barak_naveh)
*
* (C) Copyright 2003-2009, by Barak Naveh and Contributors.
*
* This library is free software; you can redistribute it and/or modify it
* under the terms of the GNU Lesser General Public License as published by
* the Free Software Foundation; either version 2.1 of the License, or
* (at your option) any later version.
*
* This library is distributed in the hope that it will be useful, but
* WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
* or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public
* License for more details.
*
* You should have received a copy of the GNU Lesser General Public License
* along with this library; if not, write to the Free Software Foundation,
* Inc.,
* 59 Temple Place, Suite 330, Boston, MA 02111-1307, USA.
*/
/* -------------------------
* FloydWarshallShortestPaths.java
* -------------------------
* (C) Copyright 2009-2009, by Tom Larkworthy and Contributors
*
* Original Author: Tom Larkworthy
*
* $Id: FloydWarshallShortestPaths.java 684 2009-06-30 04:42:22Z perfecthash $
*
* Changes
* -------
* 29-Jun-2009 : Initial revision (TL);
*
*/
import java.util.*;
import org.jgrapht.*;
/**
* The <a href="http://en.wikipedia.org/wiki/Floyd-Warshall_algorithm">
* Floyd-Warshall algorithm</a> finds all shortest paths (all n^2 of them) in
* O(n^3) time. This also works out the graph diameter during the process.
*
* @author Tom Larkworthy
*/
public class FloydWarshall<V, E>
{
//~ Instance fields --------------------------------------------------------
int nextIndex = 0;
HashMap<V, Integer> indices;
double [][] d;
double diameter;
//~ Constructors -----------------------------------------------------------
/**
* Constructs the shortest path array for the given graph.
*
* @param g input graph
* @param <V> a V object.
* @param <E> a E object.
*/
public FloydWarshall(Graph<V, E> g)
{
int sz = g.vertexSet().size();
d = new double[sz][sz];
indices = new HashMap<V, Integer>();
//Initialise distance to infinity, or the neighbours weight, or 0 if
//same
for (V v1 : g.vertexSet()) {
for (V v2 : g.vertexSet()) {
if (v1 == v2) {
d[index(v1)][index(v2)] = 0;
} else {
E e = g.getEdge(v1, v2);
if (e == null) {
d[index(v1)][index(v2)] = Double.POSITIVE_INFINITY;
} else {
d[index(v1)][index(v2)] = g.getEdgeWeight(e);
}
}
}
}
//now iterate k times
for (int k = 0; k < sz; k++) {
for (V v1 : g.vertexSet()) {
for (V v2 : g.vertexSet()) {
d[index(v1)][index(v2)] =
Math.min(
d[index(v1)][index(v2)],
d[index(v1)][k] + d[k][index(v2)]);
if(Double.POSITIVE_INFINITY != d[index(v1)][index(v2)])
diameter = Math.max(diameter, d[index(v1)][index(v2)]);
}
}
}
}
//~ Methods ----------------------------------------------------------------
/**
* Retrieves the shortest distance between two vertices.
*
* @param v1 first vertex
* @param v2 second vertex
* @return distance, or positive infinity if no path
*/
public double shortestDistance(V v1, V v2)
{
return d[index(v1)][index(v2)];
}
/**
* <p>Getter for the field <code>diameter</code>.</p>
*
* @return diameter computed for the graph
*/
public double getDiameter()
{
return diameter;
}
private int index(V vertex)
{
Integer index = indices.get(vertex);
if (index == null) {
indices.put(vertex, nextIndex);
index = nextIndex++;
}
return index;
}
}
// End FloydWarshallShortestPaths.java