/**
* 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 Gamma
* 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 GammaDistrPar extends AbstractParameter implements Parameter {
private double alpha;
private double lambda;
/**
* It creates a new gamma parameter according to the value provided by the user.
*
* @param alpha double containing the alpha parameter of the gamma distribution (must be greater than zero).
* @param lambda double containing the lambda parameter of the gamma distribution (must be greater than zero).
*
* @throws IncorrectDistributionParameterException if alpha or lambda are not greater than zero.
*
*/
public GammaDistrPar(double alpha, double lambda) throws IncorrectDistributionParameterException {
if ((alpha <= 0.0) || (lambda <= 0.0)) {
throw new IncorrectDistributionParameterException("alpha and lambda must be >0.");
} else {
this.alpha = alpha;
this.lambda = lambda;
}
}
public GammaDistrPar(Double walpha, Double wlambda) throws IncorrectDistributionParameterException {
this(walpha.doubleValue(), wlambda.doubleValue());
}
/**
* It controls if the parameter is correct or not.
* For the gamma distribution, the parameter are right if they are both greater
* than zero.
*
* @return boolean, indicating wether the parameter is correct or not.
*
*/
@Override
public boolean check() {
if ((alpha <= 0.0) || (lambda <= 0.0)) {
return false;
} else {
return true;
}
}
/**
* It returns the value of the parameter alpha of the gamma distribution.
*
* @return double with alpha.
*
*/
public double getAlpha() {
return alpha;
}
/**
* It returns the value of the lambda parameter of the gamma distribution.
*
* @return double with lambda.
*
*/
public double getLambda() {
return lambda;
}
/**
* it change the value of alpha.
* It allow the user to modify the value of the parameter alpha of the gamma
* distribution. It verify if the new value is correct, that is if alpha is greater than zero.
*
* @param alpha double indicating the new value of the parameter alpha
* @throws IncorrectDistributionParameterException if the value provided is not greater than zero.
*
*/
public void setAlpha(double alpha) throws IncorrectDistributionParameterException {
if (alpha <= 0.0) {
throw new IncorrectDistributionParameterException("alpha must be >0.");
} else {
this.alpha = alpha;
}
}
/**
* it change the value of lambda.
* It allow the user to modify the value of the parameter lambda of the gamma
* distribution. It verify if the new value is correct, that is if lambda is greater than zero.
*
* @param lambda double indicating the new value of the parameter lambda
* @throws IncorrectDistributionParameterException if the value provided is not greater than zero.
*
*/
public void setLambda(double lambda) throws IncorrectDistributionParameterException {
if (lambda <= 0.0) {
throw new IncorrectDistributionParameterException("lambda must be >0.");
} else {
this.lambda = lambda;
}
}
/**
* 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");
}
lambda = meanValue / alpha;
}
} // end GammaDistrPar