/**
* 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 Erlang
* 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 ErlangPar extends AbstractParameter implements Parameter {
private double alpha;
private double r;
/**
* creates a new erlang parameter.
* It creates a new erlang parameter with the information provided by the user.
* @param alpha double containing the "scale" parameter (must be greater than zero).
* @param r double containing the "shape" parameter (must be greater than zero).
*
* @throws IncorrectDistributionParameterException if any of the double provided is less or equal to zero.
*
*/
public ErlangPar(double alpha, double r) throws IncorrectDistributionParameterException {
this.alpha = alpha;
this.r = r;
testParameters();
}
public ErlangPar(Double walpha, Double wr) throws IncorrectDistributionParameterException {
this(walpha.doubleValue(), wr.doubleValue());
}
/**
* test the parameters.
* Tests the parametrs of an erlang distribution, if alpha or r are
* equal to zero, throw an exception. This is only a service method called by
* every method used to modify the value of the parameter.
*
* @throws IncorrectDistributionParameterException if any of the double provided is less or equal to zero.
*/
private void testParameters() throws IncorrectDistributionParameterException {
if (alpha <= 0) {
throw new IncorrectDistributionParameterException("alpha <=0");
}
if (r <= 0) {
throw new IncorrectDistributionParameterException("r <=0");
}
}
/**
* It controls if the parameter are correct or not.
* For the erlang 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) || (r <= 0)) {
return false;
} else {
return true;
}
}
/**
* it returns the value of alpha.
* It returns the parameter alpha of the erlang parameter, also called the "scale" parameter.
*
* @return double with alpha which is the "scale" parameter.
*
*/
public double getAlpha() {
return alpha;
}
/**
* it returns the value of r.
* It returns the parameter r of the erlang distribution, also called the "shape" parameter.
*
* @return double with r which is the "shape" parameter.
*
*/
public double getR() {
return r;
}
/**
* it change the value of alpha.
* It allow the user to modify the value of the alpha parameter of the erlang distribution.
* It verify that the new value is correct. Alpha must be greater than zero.
*
* @param alpha double indicating the new value of the parameter alpha.
* @throws IncorrectDistributionParameterException if the provided parameter is less or equal to zero.
*
*/
public void setAlpha(double alpha) throws IncorrectDistributionParameterException {
this.alpha = alpha;
try {
testParameters();
} catch (IncorrectDistributionParameterException ie) {
throw ie;
}
}
/**
* it change the value of r.
* It allow the user to modify the value of the r parameter of the erlang distribution.
* It verify that the new value is correct. r must be greater than zero.
*
* @param r double indicating the new value of the parameter r
* @throws IncorrectDistributionParameterException
*
*/
public void setR(double r) throws IncorrectDistributionParameterException {
this.r = r;
try {
testParameters();
} catch (IncorrectDistributionParameterException ie) {
throw ie;
}
}
/**
* 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");
}
alpha = r / meanValue;
}
} // end ErlangPar