binomial_randomdev.h

Go to the documentation of this file.

/*
 *  binomial_randomdev.h
 *
 *  This file is part of NEST.
 *
 *  Copyright (C) 2004 The NEST Initiative
 *
 *  NEST 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.
 *
 *  NEST 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 NEST.  If not, see <http://www.gnu.org/licenses/>.
 *
 */

#include "config.h"

#ifndef BINOMIAL_RANDOMDEV_H
#define BINOMIAL_RANDOMDEV_H

#include <cmath>
#include <vector>
#include "randomgen.h"
#include "randomdev.h"
#include "poisson_randomdev.h"
#include "exp_randomdev.h"
#include "lockptr.h"
#include "dictdatum.h"



/*BeginDocumentation
Name: rdevdict::binomial - binomial random deviate generator
Description:
   Generates binomially distributed random numbers.

   p(k) = (n! / k!(n-k)!) p^k (1-p)^(n-k)  , 0<=k<=n, n>0   
    
Parameters:
   p - probability of success in a single trial (double)
   n - number of trials (positive integer)

SeeAlso: CreateRDV, RandomArray, rdevdict
Author: Hans Ekkehard Plesser, Moritz Deger
*/


namespace librandom {

/* ---------------------------------------------------------------- 
 * Draw a binomial random number using the BP algoritm
 * Sampling From the Binomial Distribution on a Computer
 * Author(s): George S. Fishman
 * Source: Journal of the American Statistical Association, Vol. 74, No. 366 (Jun., 1979), pp. 418-423
 * Published by: American Statistical Association
 * Stable URL: http://www.jstor.org/stable/2286346 .
 * ---------------------------------------------------------------- */


class BinomialRandomDev : public RandomDev
  {
  public:
    // accept only lockPTRs for initialization,
    // otherwise creation of a lock ptr would
    // occur as side effect---might be unhealthy
    BinomialRandomDev(RngPtr, double p_s = 0.5, unsigned int n_s=1);
    BinomialRandomDev(double p_s = 0.5, unsigned int n_s=1);
   
    void   set_p_n   (double, unsigned int);   
    void   set_p     (double);                 
    void   set_n     (unsigned int);           

    using RandomDev::operator();
    using RandomDev::ldev;

    long ldev(RngPtr) const;   
    bool has_ldev() const { return true; }

    double operator()(RngPtr) const;     

    void set_status(const DictionaryDatum&); 

    void get_status(DictionaryDatum&) const; 


  private:
    PoissonRandomDev poisson_dev_;     
    ExpRandomDev exp_dev_;             
    double p_;                  
    double phi_;
    long m_;
    unsigned int n_;            
    std::vector<double_t> f_;                     
    unsigned int n_tablemax_;   

    void init_();               
    void PrecomputeTable(size_t);     
   
  };

  inline
  double BinomialRandomDev::operator()(RngPtr rthrd) const
  { 
    return static_cast<double>(ldev(rthrd)); 
  }
}

#endif