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src/org/cloudbus/cloudsim/distributions/LognormalDistr.java

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