78 lines
1.7 KiB
Java
78 lines
1.7 KiB
Java
/*
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* Title: CloudSim Toolkit
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* Description: CloudSim (Cloud Simulation) Toolkit for Modeling and Simulation of Clouds
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* Licence: GPL - http://www.gnu.org/copyleft/gpl.html
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*
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* Copyright (c) 2009-2012, The University of Melbourne, Australia
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*/
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package org.cloudbus.cloudsim.distributions;
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import java.util.Random;
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/**
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* The Class LognormalDistr.
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*
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* @author Marcos Dias de Assuncao
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* @since CloudSim Toolkit 1.0
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*/
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public class LognormalDistr implements ContinuousDistribution {
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/** The num gen. */
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private final Random numGen;
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/** The mean. */
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private final double mean;
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/** The dev. */
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private final double dev;
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/**
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* Instantiates a new lognormal distr.
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*
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* @param seed the seed
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* @param mean the mean
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* @param dev the dev
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*/
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public LognormalDistr(Random seed, double mean, double dev) {
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if (mean <= 0.0 || dev <= 0.0) {
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throw new IllegalArgumentException("Mean and deviation must be greater than 0.0");
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}
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numGen = seed;
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this.mean = mean;
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this.dev = dev;
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}
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/**
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* Instantiates a new lognormal distr.
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*
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* @param mean the mean
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* @param dev the dev
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*/
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public LognormalDistr(double mean, double dev) {
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if (mean <= 0.0 || dev <= 0.0) {
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throw new IllegalArgumentException("Mean and deviation must be greater than 0.0");
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}
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numGen = new Random(System.currentTimeMillis());
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this.mean = mean;
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this.dev = dev;
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}
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/*
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* (non-Javadoc)
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* @see cloudsim.distributions.ContinuousDistribution#sample()
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*/
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@Override
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public double sample() {
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// generate a normal variate from a uniform variate
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double n = Math.sqrt(-2 * Math.log(numGen.nextDouble()))
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* Math.sin(2 * Math.PI * numGen.nextDouble());
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// use it to generate the lognormal variate
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return Math.pow(Math.E, mean + dev * n);
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}
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}
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