performancedemo.java

来自「JAVA图论的算法包。用过觉得还不错」· Java 代码 · 共 165 行

/* ==========================================
 * 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 2003-2007, 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.
 */
/* --------------------
 * PerformanceDemo.java
 * --------------------
 * (C) Copyright 2003-2007, by Barak Naveh and Contributors.
 *
 * Original Author:  Barak Naveh
 * Contributor(s):   -
 *
 * $Id: PerformanceDemo.java 636 2008-09-28 22:11:08Z perfecthash $
 *
 * Changes
 * -------
 * 10-Aug-2003 : Initial revision (BN);
 *
 */
package org.jgrapht.demo;

import java.io.*;

import java.util.*;

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


/**
 * A simple demo to test memory and CPU consumption on a graph with 3 million
 * elements.
 *
 * <p>NOTE: To run this demo you may need to increase the JVM max mem size. In
 * Sun's JVM it is done using the "-Xmx" switch. Specify "-Xmx300M" to set it to
 * 300MB.</p>
 *
 * <p>WARNING: Don't run this demo as-is on machines with less than 512MB
 * memory. Your machine will start paging severely. You need to first modify it
 * to have fewer graph elements. This is easily done by changing the loop
 * counters below.</p>
 *
 * @author Barak Naveh
 * @since Aug 10, 2003
 */
public final class PerformanceDemo
{
    //~ Methods ----------------------------------------------------------------

    /**
     * The starting point for the demo.
     *
     * @param args ignored.
     */
    public static void main(String [] args)
    {
        long time = System.currentTimeMillis();

        reportPerformanceFor("starting at", time);

        Graph<Object, DefaultEdge> g =
            new Pseudograph<Object, DefaultEdge>(DefaultEdge.class);
        Object prev;
        Object curr;

        curr = prev = new Object();
        g.addVertex(prev);

        int numVertices = 10000;
        int numEdgesPerVertex = 200;
        int numElements = numVertices * (1 + numEdgesPerVertex);

        System.out.println(
            "\n" + "allocating graph with " + numElements
            + " elements (may take a few tens of seconds)...");

        for (int i = 0; i < numVertices; i++) {
            curr = new Object();
            g.addVertex(curr);

            for (int j = 0; j < numEdgesPerVertex; j++) {
                g.addEdge(prev, curr);
            }

            prev = curr;
        }

        reportPerformanceFor("graph allocation", time);

        time = System.currentTimeMillis();

        for (
            Iterator i = new BreadthFirstIterator<Object, DefaultEdge>(g);
            i.hasNext();)
        {
            i.next();
        }

        reportPerformanceFor("breadth traversal", time);

        time = System.currentTimeMillis();

        for (
            Iterator i = new DepthFirstIterator<Object, DefaultEdge>(g);
            i.hasNext();)
        {
            i.next();
        }

        reportPerformanceFor("depth traversal", time);

        System.out.println(
            "\n"
            + "Paused: graph is still in memory (to check mem consumption).");
        System.out.print("press enter to free memory and finish...");

        try {
            System.in.read();
        } catch (IOException e) {
            e.printStackTrace();
        }

        System.out.println("done.");
    }

    private static void reportPerformanceFor(String msg, long refTime)
    {
        double time = (System.currentTimeMillis() - refTime) / 1000.0;
        double mem = usedMemory()
            / (1024.0 * 1024.0);
        mem = Math.round(mem * 100) / 100.0;
        System.out.println(msg + " (" + time + " sec, " + mem + "MB)");
    }

    private static long usedMemory()
    {
        Runtime rt = Runtime.getRuntime();

        return rt.totalMemory() - rt.freeMemory();
    }
}

// End PerformanceDemo.java