directedacyclicgraphtest.java

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/* ==========================================
 * 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 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.
 */
/* -------------------
 * DirectedAcyclicGraphTest.java
 * -------------------
 * (C) Copyright 2008-2008, by Peter Giles and Contributors.
 *
 * Original Author:  Peter Giles
 * Contributor(s):   -
 *
 * $Id: DirectedAcyclicGraphTest.java 637 2008-09-28 22:23:11Z perfecthash $
 *
 * Changes
 * -------
 * 17-Mar-2008 : Initial revision (PG);
 *
 */
package org.jgrapht.experimental.dag;

import java.util.*;

import junit.framework.*;

import org.jgrapht.*;
import org.jgrapht.alg.*;
import org.jgrapht.generate.*;
import org.jgrapht.graph.*;
import org.jgrapht.traverse.*;


/**
 * Unit tests for the DirectedAcyclicGraph, a dynamic DAG implementation.
 *
 * @author [e-mail]
 */
public class DirectedAcyclicGraphTest
    extends TestCase
{
    //~ Instance fields --------------------------------------------------------

    private RandomGraphGenerator<Long, DefaultEdge> randomGraphGenerator = null;
    private Graph<Long, DefaultEdge> sourceGraph = null;

    //~ Methods ----------------------------------------------------------------

    @Override protected void setUp()
        throws Exception
    {
        super.setUp();

        setUpWithSeed(100, 5000, 2);
    }

    private void setUpWithSeed(int vertices, int edges, long seed)
    {
        randomGraphGenerator =
            new RepeatableRandomGraphGenerator<Long, DefaultEdge>(
                vertices,
                edges,
                seed);
        sourceGraph =
            new SimpleDirectedGraph<Long, DefaultEdge>(DefaultEdge.class);
        randomGraphGenerator.generateGraph(
            sourceGraph,
            new LongVertexFactory(),
            null);
    }

    /**
     * Tests the cycle detection capabilities of DirectedAcyclicGraph by
     * building a parallel SimpleDirectedGraph and using a CycleDetector to
     * check for cycles, and comparing the results.
     */
    public void testCycleDetectionInRandomGraphBuild()
    {
        for (int i = 0; i < 50; i++) { // test with 50 random graph
                                       // configurations
            setUpWithSeed(20, 200, i);

            DirectedAcyclicGraph<Long, DefaultEdge> dag =
                new DirectedAcyclicGraph<Long, DefaultEdge>(DefaultEdge.class);
            SimpleDirectedGraph<Long, DefaultEdge> compareGraph =
                new SimpleDirectedGraph<Long, DefaultEdge>(DefaultEdge.class);

            for (Long vertex : sourceGraph.vertexSet()) {
                dag.addVertex(vertex);
                compareGraph.addVertex(vertex);
            }

            for (DefaultEdge edge : sourceGraph.edgeSet()) {
                Long edgeSource = sourceGraph.getEdgeSource(edge);
                Long edgeTarget = sourceGraph.getEdgeTarget(edge);

                boolean dagRejectedEdge = false;
                try {
                    dag.addDagEdge(edgeSource, edgeTarget);
                } catch (DirectedAcyclicGraph.CycleFoundException e) {
                    // okay, it did't add that edge
                    dagRejectedEdge = true;
                }

                DefaultEdge compareEdge =
                    compareGraph.addEdge(edgeSource, edgeTarget);
                CycleDetector<Long, DefaultEdge> cycleDetector =
                    new CycleDetector<Long, DefaultEdge>(compareGraph);

                boolean cycleDetected = cycleDetector.detectCycles();

                assertTrue(dagRejectedEdge == cycleDetected);

                if (cycleDetected) {
                    // remove the edge from the compareGraph so the graphs
                    // remain in sync
                    compareGraph.removeEdge(compareEdge);
                }
            }

            // after all this, our graphs must be equal
            assertEquals(compareGraph.vertexSet(), dag.vertexSet());

            // for some reason comparing vertex sets doesn't work, so doing it
            // the hard way:
            for (Long sourceVertex : compareGraph.vertexSet()) {
                for (
                    DefaultEdge outgoingEdge
                    : compareGraph.outgoingEdgesOf(sourceVertex))
                {
                    Long targetVertex =
                        compareGraph.getEdgeTarget(outgoingEdge);
                    assertTrue(dag.containsEdge(sourceVertex, targetVertex));
                }
            }
        }
    }

    /**
     * trivial test of topological order using a linear graph
     */
    public void testTopoIterationOrderLinearGraph()
    {
        DirectedAcyclicGraph<Long, DefaultEdge> dag =
            new DirectedAcyclicGraph<Long, DefaultEdge>(DefaultEdge.class);
        LinearGraphGenerator<Long, DefaultEdge> graphGen =
            new LinearGraphGenerator<Long, DefaultEdge>(100);
        graphGen.generateGraph(dag, new LongVertexFactory(), null);

        Iterator<Long> internalTopoIter = dag.iterator();
        TopologicalOrderIterator<Long, DefaultEdge> comparTopoIter =
            new TopologicalOrderIterator<Long, DefaultEdge>(dag);

        while (comparTopoIter.hasNext()) {
            Long compareNext = comparTopoIter.next();
            Long myNext = null;

            if (internalTopoIter.hasNext()) {
                myNext = internalTopoIter.next();
            }

            assertSame(compareNext, myNext);
            assertEquals(comparTopoIter.hasNext(), internalTopoIter.hasNext());
        }
    }

    /**
     * more rigorous test of topological iteration order, by assuring that each
     * visited vertex adheres to the definition of topological order, that is
     * that it doesn't have a path leading to any of its predecessors.
     */
    public void testTopoIterationOrderComplexGraph()
    {
        for (int seed = 0; seed < 20; seed++) {
            DirectedAcyclicGraph<Long, DefaultEdge> dag =
                new DirectedAcyclicGraph<Long, DefaultEdge>(DefaultEdge.class);
            RepeatableRandomGraphGenerator<Long, DefaultEdge> graphGen =
                new RepeatableRandomGraphGenerator<Long, DefaultEdge>(
                    100,
                    500,
                    seed);
            graphGen.generateGraph(dag, new LongVertexFactory(), null);

            ConnectivityInspector<Long, DefaultEdge> connectivityInspector =
                new ConnectivityInspector<Long, DefaultEdge>(dag);

            Iterator<Long> internalTopoIter = dag.iterator();

            List<Long> previousVertices = new ArrayList<Long>();

            while (internalTopoIter.hasNext()) {
                Long vertex = internalTopoIter.next();

                for (Long previousVertex : previousVertices) {
                    connectivityInspector.pathExists(vertex, previousVertex);
                }

                previousVertices.add(vertex);
            }
        }
    }

    public void testIterationBehaviors()
    {
        int vertexCount = 100;

        DirectedAcyclicGraph<Long, DefaultEdge> dag =
            new DirectedAcyclicGraph<Long, DefaultEdge>(DefaultEdge.class);
        RepeatableRandomGraphGenerator<Long, DefaultEdge> graphGen =
            new RepeatableRandomGraphGenerator<Long, DefaultEdge>(
                vertexCount,
                500,
                2);
        graphGen.generateGraph(dag, new LongVertexFactory(), null);

        Iterator<Long> dagIter = dag.iterator();

        // Scroll through all the elements, then make sure things happen as
        // should when an iterator is all used up

        for (int i = 0; i < vertexCount; i++) {
            assertTrue(dagIter.hasNext());
            dagIter.next();
        }
        assertFalse(dagIter.hasNext());

        try {
            dagIter.next();
            fail();
        } catch (NoSuchElementException e) {
            // good, we already looked at all of the elements
        }

        assertFalse(dagIter.hasNext());

        dagIter = dag.iterator(); // replace dagIter;

        assertNotNull(dagIter.next()); // make sure it works on first element
                                       // even if hasNext() wasn't called

        // Test that ConcurrentModificationExceptionS happen as they should when
        // the topology is modified during iteration

        // remove a random vertex
        dag.removeVertex(dag.vertexSet().iterator().next());

        // now we expect exceptions since the topological order has been
        // modified (albeit trivially)
        try {
            dagIter.next();
            fail(); // fail, no exception was thrown
        } catch (ConcurrentModificationException e) {
            // good, this is expected
        }

        try {
            dagIter.hasNext();
            fail(); // fail, no exception was thrown
        } catch (ConcurrentModificationException e) {
            // good, this is expected
        }

        try {
            dagIter.remove();
            fail(); // fail, no exception was thrown
        } catch (ConcurrentModificationException e) {
            // good, this is expected
        }

        // TODO: further iterator tests
    }

    // Performance tests have underscores in the names so that they
    // they are only run explicitly (not automatically as part of
    // default JUnit runs).

    /**
     * A somewhat frivolous test of the performance difference between doing a
     * full cycle detection (non-dynamic algorithm) for each edge added versus
     * the dynamic algorithm used by DirectedAcyclicGraph.
     */
    public void _testPerformanceVersusStaticChecking()
    {