ChiSquareNoncentralPoisGen.java

/*
 * Class:        ChiSquareNoncentralPoisGen
 * Description:  noncentral chi square random variate generators using Poisson
                 and central chi square generators
 * Environment:  Java
 * Software:     SSJ
 * Copyright (C) 2001  Pierre L'Ecuyer and Universite de Montreal
 * Organization: DIRO, Universite de Montreal
 * @author       Richard Simard
 * @since
 *
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 *
 */
package umontreal.ssj.randvar;
 
import umontreal.ssj.rng.*;

public class ChiSquareNoncentralPoisGen extends ChiSquareNoncentralGen {

   public ChiSquareNoncentralPoisGen(RandomStream stream, double nu, double lambda) {
      super(stream, null);
      setParams(nu, lambda);
      if (lambda > 4290000000.0)
         throw new UnsupportedOperationException("   lambda too large");
   }
 
   public double nextDouble() {
      return poisGenere(stream, nu, lambda);
   }

   public static double nextDouble(RandomStream stream, double nu, double lambda) {
      return poisGenere(stream, nu, lambda);
   }
 
//>>>>>>>>>>>>>>>>>>>>  P R I V A T E S    M E T H O D S   <<<<<<<<<<<<<<<<<<<<
 
   private static double poisGenere(RandomStream s, double nu, double lambda) {
      int j = PoissonTIACGen.nextInt(s, 0.5 * lambda);
      return GammaAcceptanceRejectionGen.nextDouble(s, 0.5 * nu + j, 0.5);
   }
 
}