playground.johannes.studies.coopsim.TimeSampler.java Source code

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Here is the source code for playground.johannes.studies.coopsim.TimeSampler.java

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/* *********************************************************************** *
 * project: org.matsim.*
 * TimeSampler.java
 *                                                                         *
 * *********************************************************************** *
 *                                                                         *
 * copyright       : (C) 2011 by the members listed in the COPYING,        *
 *                   LICENSE and WARRANTY file.                            *
 * email           : info at matsim dot org                                *
 *                                                                         *
 * *********************************************************************** *
 *                                                                         *
 *   This program is free software; you can redistribute it and/or modify  *
 *   it under the terms of the GNU General Public License as published by  *
 *   the Free Software Foundation; either version 2 of the License, or     *
 *   (at your option) any later version.                                   *
 *   See also COPYING, LICENSE and WARRANTY file                           *
 *                                                                         *
 * *********************************************************************** */
package playground.johannes.studies.coopsim;

import java.util.Arrays;
import java.util.Random;

import org.apache.commons.math.FunctionEvaluationException;
import org.apache.commons.math.analysis.UnivariateRealFunction;

/**
 * @author illenberger
 * 
 */
public class TimeSampler {

    private final Random random;

    private final int resolution = 60;

    private double[] y;

    public TimeSampler(UnivariateRealFunction pdf, int max, Random random) {
        this.random = random;
        max = max / resolution;
        try {
            y = new double[max];
            y[0] = 0;//pdf.value(0); FIXME
            int i = 1;
            for (int t = resolution; t < max * resolution; t += resolution) {
                y[i] = pdf.value(t) + y[i - 1];
                i++;
            }

            for (i = 0; i < max; i++) {
                y[i] = y[i] / y[max - 1];
            }
            //         System.out.println("last index = " + y[max-1]);
        } catch (FunctionEvaluationException e) {
            e.printStackTrace();
        }
    }

    public int nextSample() {
        double p = random.nextDouble();
        int idx = Arrays.binarySearch(y, p);
        if (idx < 0)
            idx = -idx - 1;
        return Math.max(resolution, idx * resolution);
        // while (true) { // for ever
        // int t = random.nextInt(max);
        //
        // try {
        // double p = pdf.value(t)/norm;
        //
        // if (random.nextDouble() < p)
        // return t;
        //
        // } catch (FunctionEvaluationException e) {
        // e.printStackTrace();
        // }

    }
}