Package jmt.engine.random

Source Code of jmt.engine.random.ParetoPar

/**   
  * Copyright (C) 2006, Laboratorio di Valutazione delle Prestazioni - Politecnico di Milano

  * 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.

  * This program 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 General Public License for more details.

  * You should have received a copy of the GNU General Public License
  * along with this program; if not, write to the Free Software
  * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
  */

package jmt.engine.random;

import jmt.common.exception.IncorrectDistributionParameterException;

/**
*
* This is the parameter that should be passed to the Pareto
* distribution.
*
* <br><br>Copyright (c) 2003
* <br>Politecnico di Milano - dipartimento di Elettronica e Informazione
* @author Fabrizio Frontera - ffrontera@yahoo.it
* @author Bertoli Marco 10-oct-2005
*
*/

public class ParetoPar extends AbstractParameter implements Parameter {

  private double alpha;
  private double k;

  /**
   * It creates a new pareto parameter according with the data provided by the user.
   * The user provides the value of the parameter k and alpha of the new pareto
   * distribution. These value are verified by the constructor.
   *
   * @param alpha double containing the alpha parameter of the distribution (must be greater than zero).
   * @param k double containing the k parameter of the distribution (must be greater than zero).
   *
   * @throws IncorrectDistributionParameterException if k or alpha are not both greater than zero.
   *
   */
  public ParetoPar(double alpha, double k) throws IncorrectDistributionParameterException {
    this.alpha = alpha;
    this.k = k;
    if (!check()) {
      if (k <= 0) {
        throw new IncorrectDistributionParameterException("k must be gtz");
      }
      if (alpha <= 0) {
        throw new IncorrectDistributionParameterException("alpha must be gtz");
      }
    }
  }

  public ParetoPar(Double walpha, Double wk) throws IncorrectDistributionParameterException {
    this(walpha.doubleValue(), wk.doubleValue());
  }

  /**
   * It controls if the parameter is correct. For the pareto distribution, the
   * parameter is right if both alpha and k are greater than zero.
   *
   * @return boolean, indicating wether the parameter is correct or not.
   *
   */

  @Override
  public boolean check() {
    if ((alpha <= 0) || (k <= 0)) {
      return false;
    } else {
      return true;
    }
  }

  /**
   * It returns the value of the parameter alpha of the pareto distribution.
   *
   * @return double with the alpha parameter of the pareto distribution.
   *
   */

  public double getAlpha() {
    return alpha;
  }

  /**
   * It returns the value of the parameter k of the pareto distribution.
   *
   * @return double with the k parameter of the pareto distribution.
   *
   */

  public double getK() {
    return k;
  }

  /**
   * it change the alpha of the distribution.
   * It allow the user to change the value of the parameter alpha of the pareto
   * distribution. It verify that the provided value is correct (alpha must be
   * greater than zero).
   *
   * @param alpha double indicating the new value of the parameter alpha
   * @throws IncorrectDistributionParameterException if alpha is not greater than zero.
   *
   */

  public void setAlpha(double alpha) throws IncorrectDistributionParameterException {
    if (alpha <= 0) {
      throw new IncorrectDistributionParameterException("alpha must be gtz");
    } else {
      this.alpha = alpha;
    }
  }

  /**
   * it change the k of the distribution.
   * It allow the user to change the value of the parameter k of the pareto
   * distribution. It verify that the provided value is correct (k must be
   * greater than zero).
   *
   * @param k double indicating the new value of the parameter k
   * @throws IncorrectDistributionParameterException
   *
   */

  public void setK(double k) throws IncorrectDistributionParameterException {
    if (k <= 0) {
      throw new IncorrectDistributionParameterException("k must be gtz");
    } else {
      this.k = k;
    }
  }

  /**
   * Sets mean for a given distribution parameter. This method is required to adjust distributions
   * mean values into Load Dependent Service Time Strategy
   * @param meanValue new mean value for this distribution
   * Author: Bertoli Marco
   * @throws IncorrectDistributionParameterException if mean value is invalid for this distribution
   */
  @Override
  public void setMean(double meanValue) throws IncorrectDistributionParameterException {
    if (meanValue <= 0 || Double.isInfinite(meanValue)) {
      throw new IncorrectDistributionParameterException("Mean value must be finite and greater than zero");
    }
    k = meanValue * (alpha - 1) / alpha;
  }

} // end ParetoPar
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