BinomialConvolutionGen.java

/*
 * Class:        BinomialConvolutionGen
 * Description:  binomial random variate generators using the convolution method
 * Environment:  Java
 * Software:     SSJ 
 * Copyright (C) 2001  Pierre L'Ecuyer and Universite de Montreal
 * Organization: DIRO, Universite de Montreal
 * @author       
 * @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.probdist.*;
import umontreal.ssj.rng.*;

public class BinomialConvolutionGen extends BinomialGen {

   public BinomialConvolutionGen(RandomStream s, int n, double p) {
      super(s, null);
      setParams(n, p);
   }

   public BinomialConvolutionGen(RandomStream s, BinomialDist dist) {
      super(s, dist);
   }
 
   public int nextInt() {
      int x = 0;
      for (int i = 0; i < n; i++) {
         double unif = stream.nextDouble();
         if (unif <= p)
            x++;
      }
      return x;
   }

   public static int nextInt(RandomStream s, int n, double p) {
      if (n <= 0)
         throw new IllegalArgumentException("n <= 0");
      if (p < 0 || p > 1)
         throw new IllegalArgumentException("p must be in [0,1]");
      return convolution(s, n, p);
   }
 
   private static int convolution(RandomStream stream, int n, double p) {
      int x = 0;
      for (int i = 0; i < n; i++) {
         double unif = stream.nextDouble();
         if (unif <= p)
            x++;
      }
      return x;
   }
}