BellmanFordShortestPathTest.java

/* ==========================================
 * 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 2003-2008, by Barak Naveh and Contributors.
 *
 * This program and the accompanying materials are dual-licensed under
 * either
 *
 * (a) the terms of the GNU Lesser General Public License version 2.1
 * as published by the Free Software Foundation, or (at your option) any
 * later version.
 *
 * or (per the licensee's choosing)
 *
 * (b) the terms of the Eclipse Public License v1.0 as published by
 * the Eclipse Foundation.
 */
/* ------------------------------
 * BellmanFordShortestPathTest.java
 * ------------------------------
 * (C) Copyright 2006-2008, by John V. Sichi and Contributors.
 *
 * Original Author:  John V. Sichi
 * Contributor(s):   -
 *
 * $Id$
 *
 * Changes
 * -------
 * 14-Jan-2006 : Initial revision (JVS);
 *
 */
package org.jgrapht.alg;

import java.util.*;

import org.jgrapht.*;
import org.jgrapht.graph.*;


/**
 * .
 *
 * @author John V. Sichi
 */
public class BellmanFordShortestPathTest
    extends ShortestPathTestCase
{
    //~ Methods ----------------------------------------------------------------

    /**
     * .
     */
    public void testConstructor()
    {
        BellmanFordShortestPath<String, DefaultWeightedEdge> path;
        Graph<String, DefaultWeightedEdge> g = create();

        path = new BellmanFordShortestPath<String, DefaultWeightedEdge>(g, V3);

        // find best path with no constraint on number of hops
        assertEquals(
            Arrays.asList(
                new DefaultEdge[] {
                    e13,
                    e12,
                    e24,
                    e45
                }),
            path.getPathEdgeList(V5));
        assertEquals(15.0, path.getCost(V5), 0);

        // find best path within 2 hops (less than optimal)
        path =
            new BellmanFordShortestPath<String, DefaultWeightedEdge>(
                g,
                V3,
                2);
        assertEquals(
            Arrays.asList(
                new DefaultEdge[] {
                    e34,
                    e45
                }),
            path.getPathEdgeList(V5));
        assertEquals(25.0, path.getCost(V5), 0);

        // find best path within 1 hop (doesn't exist!)
        path =
            new BellmanFordShortestPath<String, DefaultWeightedEdge>(
                g,
                V3,
                1);
        assertNull(path.getPathEdgeList(V5));
        assertEquals(Double.POSITIVE_INFINITY, path.getCost(V5));
    }

    protected List findPathBetween(
        Graph<String, DefaultWeightedEdge> g,
        String src,
        String dest)
    {
        return BellmanFordShortestPath.findPathBetween(g, src, dest);
    }

    public void testWithNegativeEdges()
    {
        Graph<String, DefaultWeightedEdge> g = createWithBias(true);

        List path;

        path = findPathBetween(g, V1, V4);
        assertEquals(Arrays.asList(
                new DefaultEdge[] {
                    e13,
                    e34
                }), path);

        path = findPathBetween(g, V1, V5);
        assertEquals(Arrays.asList(new DefaultEdge[] { e15 }), path);
    }
}

// End BellmanFordShortestPathTest.java