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Java example source code file (LowDiscrepancyGeneratorComparison.java)

This example Java source code file (LowDiscrepancyGeneratorComparison.java) is included in the alvinalexander.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" TM.

Learn more about this Java project at its project page.

Java - Java tags/keywords

arraylist, awt, display, geometry, graphics2d, gridbagconstraints, gui, jlabel, list, mersennetwister, override, pad, pair, plot, randomgenerator, randomvectorgenerator, swing, util, vector2d

The LowDiscrepancyGeneratorComparison.java Java example source code

/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.apache.commons.math3.userguide;

import java.awt.Color;
import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.GridBagConstraints;
import java.awt.GridBagLayout;
import java.awt.Insets;
import java.awt.RenderingHints;
import java.awt.geom.Rectangle2D;
import java.util.ArrayList;
import java.util.List;

import javax.swing.JComponent;
import javax.swing.JLabel;
import javax.swing.JTextArea;

import org.apache.commons.math3.geometry.euclidean.twod.Vector2D;
import org.apache.commons.math3.random.HaltonSequenceGenerator;
import org.apache.commons.math3.random.JDKRandomGenerator;
import org.apache.commons.math3.random.MersenneTwister;
import org.apache.commons.math3.random.RandomGenerator;
import org.apache.commons.math3.random.RandomVectorGenerator;
import org.apache.commons.math3.random.SobolSequenceGenerator;
import org.apache.commons.math3.random.UncorrelatedRandomVectorGenerator;
import org.apache.commons.math3.random.UniformRandomGenerator;
import org.apache.commons.math3.userguide.ExampleUtils.ExampleFrame;
import org.apache.commons.math3.util.FastMath;
import org.apache.commons.math3.util.Pair;

/**
 * Plots 2D samples drawn from various pseudo / quasi-random generators.
 */
public class LowDiscrepancyGeneratorComparison {

    public static List<Vector2D> makeCircle(int samples, final RandomVectorGenerator generator) {
        List<Vector2D> points = new ArrayList();
        for (double i = 0; i < samples; i++) {
            double[] vector = generator.nextVector();
            Vector2D point = new Vector2D(vector);
            points.add(point);
        }

        // normalize points first
        points = normalize(points);
        
        // now test if the sample is within the unit circle
        List<Vector2D> circlePoints = new ArrayList();
        for (Vector2D p : points) {
            double criteria = FastMath.pow(p.getX(), 2) + FastMath.pow(p.getY(), 2);
            if (criteria < 1.0) {
                circlePoints.add(p);
            }
        }

        return circlePoints;
    }

    public static List<Vector2D> makeRandom(int samples, RandomVectorGenerator generator) {
        List<Vector2D> points = new ArrayList();
        for (double i = 0; i < samples; i++) {
            double[] vector = generator.nextVector();
            Vector2D point = new Vector2D(vector);
            points.add(point);
        }
        
        return normalize(points);
    }

    public static List<Vector2D> normalize(final List input) {
        // find the mininum and maximum x value in the dataset
        double minX = Double.MAX_VALUE;
        double maxX = Double.MIN_VALUE;
        for (Vector2D p : input) {
            minX = FastMath.min(minX, p.getX());
            maxX = FastMath.max(maxX, p.getX());
        }
        
        double minY, maxY;
        
        // use the minimum to detect if we either have input values in the range [0, 1] or [-sqrt(3), sqrt(3)]
        if (FastMath.abs(minX) < 0.1) {
            minX = minY = 0.0;
            maxX = maxY = 1.0;
        } else {
            minX = minY = -FastMath.sqrt(3);
            maxX = maxY = FastMath.sqrt(3);            
        }

        double rangeX = maxX - minX;
        double rangeY = maxY - minY;
        List<Vector2D> points = new ArrayList();
        for (Vector2D p : input) {
            double[] arr = p.toArray();
            // normalize to the range [-1, 1]
            arr[0] = (arr[0] - minX) / rangeX * 2 - 1;
            arr[1] = (arr[1] - minY) / rangeY * 2 - 1;
            points.add(new Vector2D(arr));
        }
        return points;
    }
    
    @SuppressWarnings("serial")
    public static class Display extends ExampleFrame {
        
        public Display() {
            setTitle("Commons-Math: Pseudo/Quasi-random examples");
            setSize(800, 800);
            
            setLayout(new GridBagLayout());
            
            int[] datasets = new int[] { 256, 1000, 2500, 1000 };
            List<Pair generators = new ArrayList>();

            generators.add(new Pair<String, RandomVectorGenerator>("Uncorrelated\nUniform(JDK)",
                    new UncorrelatedRandomVectorGenerator(2, new UniformRandomGenerator(new JDKRandomGenerator()))));
            generators.add(new Pair<String, RandomVectorGenerator>("Independent\nRandom(MT)", new RandomVectorGenerator() {

                RandomGenerator[] rngs = new RandomGenerator[] {
                    new MersenneTwister(0),
                    new MersenneTwister(1)
                };
                
                public double[] nextVector() {
                    final double[] vector = new double[2];
                    vector[0] = rngs[0].nextDouble();
                    vector[1] = rngs[1].nextDouble();
                    return vector;
                }
                
            }));            
            generators.add(new Pair<String, RandomVectorGenerator>("HaltonSequence", new HaltonSequenceGenerator(2)));            
            generators.add(new Pair<String, RandomVectorGenerator>("SobolSequence", new SobolSequenceGenerator(2)));            
            
            GridBagConstraints c = new GridBagConstraints();
            c.fill = GridBagConstraints.VERTICAL;
            c.gridx = 1;
            c.gridy = 0;
            c.insets = new Insets(2, 2, 2, 2);

            for (Pair<String, RandomVectorGenerator> pair : generators) {
                JTextArea text = new JTextArea(pair.getFirst());
                text.setEditable(false);
                text.setOpaque(false);
                add(text, c);
                c.gridx++;
            }
            int saveY = ++c.gridy;
            
            c.gridx = 0;
            for (int type = 0; type < 4; type++) {
                JLabel text = new JLabel("n=" + String.valueOf(datasets[type]));
                text.setOpaque(false);
                add(text, c);
                c.gridy++;
            }

            c.gridy = saveY;
            for (int type = 0; type < 4; type++) {
                c.gridx = 1;

                for (Pair<String, RandomVectorGenerator> pair : generators) {
                    List<Vector2D> points = null;
                    int samples = datasets[type];
                    switch (type) {
                        case 0:
                            points = makeRandom(samples, pair.getValue());
                            break;
                        case 1:
                            points = makeRandom(samples, pair.getValue());
                            break;
                        case 2:
                            points = makeRandom(samples, pair.getValue());
                            break;
                        case 3:
                            points = makeCircle(samples, pair.getValue());
                            break;
                    }
                    add(new Plot(points), c);
                    c.gridx++;
                }

                c.gridy++;
            }            
        }
    }

    @SuppressWarnings("serial")
    public static class Plot extends JComponent {

        private static double PAD = 10;

        private List<Vector2D> points;

        public Plot(final List<Vector2D> points) {
            this.points = points;
        }
        
        @Override
        protected void paintComponent(Graphics g) {
            super.paintComponent(g);
            Graphics2D g2 = (Graphics2D)g;
            g2.setRenderingHint(RenderingHints.KEY_ANTIALIASING,
                                RenderingHints.VALUE_ANTIALIAS_ON);

            int w = getWidth();
            int h = getHeight();

            g2.clearRect(0, 0, w, h);
            
            g2.setPaint(Color.black);
            g2.drawRect(0, 0, w - 1, h - 1);
            
            for (Vector2D point : points) {
                Vector2D p = transform(point, w, h);
                double[] arr = p.toArray();
                g2.draw(new Rectangle2D.Double(arr[0] - 1, arr[1] - 1, 2, 2));
            }
        }        
        
        @Override
        public Dimension getPreferredSize() {
            return new Dimension(140, 140);
        }

        private Vector2D transform(Vector2D point, int width, int height) {
            double[] arr = point.toArray();
            return new Vector2D(new double[] { PAD + (arr[0] + 1) / 2.0 * (width - 2 * PAD),
                                                  height - PAD - (arr[1] + 1) / 2.0 * (height - 2 * PAD) });
        }
    }

    public static void main(String[] args) {
        ExampleUtils.showExampleFrame(new Display());
    }
}

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