source: trunk/src/random_singleton.h @ 13

// $Id: random_singleton.h 13 2003-06-19 10:00:28Z daniel $

#ifndef _THEP_RANDOMSINGLETON_
#define _THEP_RANDOMSINGLETON_ 


#include <cstdlib>
#include <cstdio>
#include <string>

// GSL INCLUDES
////////////////////////////
#include <gsl/gsl_rng.h>
#include <gsl/gsl_randist.h>


namespace thep_cpp_tools
{  
  /**
     Class defining interface for different random
     stuff.
  */
  class random_singleton
  {
  private:
    /**
       flag that keeps track of whether an object
       exists or not.
    */
    static bool instance_;

    /**
       pointer to an instance of the class.
    */
    static random_singleton *singleobj_;

    /**
       GSL stuff
    */
    gsl_rng* r_; 
    gsl_ran_discrete_t* gen_;  // general purpose distribution 

    /**
       Private constructor. Only way to 
       create object is via get_instance().
    */
    random_singleton();

  public:
    /**
       Method used to instantiate an object from this class.
       The seed is zero by default. If user wish to use time
       the user should specify a negative seed. Note that if an
       object already exists the method will return that object
       and hence no new object is created.
    */
    static random_singleton* get_instance( int seed = 0 );


    /** 
  A random integer number is returned from a uniform
  distribution between [ \a min,\a max]. The values of 
  \a min and \a max are obtained via get_uniform_int_min() 
  and get_uniform_int_max() 
    */
    inline long int get_uniform_int() const;


    /** 
  A random number (double precision) is returned 
  from a uniform distribution between [ 0, 1 [. 
    */
    inline double get_uniform_double() const;


    /** 
  A random number (double precision) is returned 
  from a gaussioan distribution between where \a sigma
  can be specified by caller. \a sigma (\f$\sigma\f$) is 
  the standard deviation in a gaussian distribution: \n\n
  \f$f(x) = \frac{1}{\sqrt{2\pi\sigma^2}}e^{-\frac{x^2}{2\sigma^2}}\f$ \n\n
  Default is \a sigma = 1.  
    */
    inline double get_gaussian( const double& sigma ) const;


    /** 
  A random number (double precision) is returned 
  from an exponential distribution. \a mu (\f$\mu\f$), the mean, 
  can be specified by caller: \f$f(x) = \frac{1}{\mu}e^{-\frac{x}{\mu}}\f$.
  Default is \a mu = 1.  
    */
    inline double get_exponential( const double& mu ) const;
    

    /** 
  See get_uniform_int()!
    */
    inline long int get_uniform_min() const;
 

    /** 
  See get_uniform_int()!
    */
    inline long int get_uniform_max() const;


    /**
       Return seed to user for documentation purposes.
    */
    inline int get_seed() const;

    /**
       Set a new seed
    */
    void set_seed( const int& seed );


    /**
       Set probabilities \a p for the general purpose 
       distribution. 
    */
    inline void set_general_distribution_prob( const size_t& k, 
                 const double* p );
    

    /**
       Get a random number (index) from the general purpose
       distribution
    */
    inline size_t get_rnd_discrete();


    /**
       GSL has different types of random genenerators. This function 
       returns the one used.
    */
    std::string get_generator_type() const;


    /**
       Destructor returning memory using GSL free functions
    */
    ~random_singleton();
  }; // random_singleton
  
#include "random_singleton.icc"

} // namespace thep_c++_tools

#endif