.. _program_listing_file__tmp_ws_src_ecl_core_ecl_time_include_ecl_time_random_number_generator.hpp:

Program Listing for File random_number_generator.hpp
====================================================

|exhale_lsh| :ref:`Return to documentation for file <file__tmp_ws_src_ecl_core_ecl_time_include_ecl_time_random_number_generator.hpp>` (``/tmp/ws/src/ecl_core/ecl_time/include/ecl/time/random_number_generator.hpp``)

.. |exhale_lsh| unicode:: U+021B0 .. UPWARDS ARROW WITH TIP LEFTWARDS

.. code-block:: cpp

   
   /*****************************************************************************
   ** Ifdefs
   *****************************************************************************/
   
   #ifndef ECL_TIME_RANDOM_NUMBER_GENERATOR_HPP_
   #define ECL_TIME_RANDOM_NUMBER_GENERATOR_HPP_
   
   /*****************************************************************************
   ** Includes
   *****************************************************************************/
   
   #include <cmath>
   #include <ctime>
   #include <cstdlib>
   #include <ecl/config.hpp>
   
   
   /*****************************************************************************
   ** Namespaces
   *****************************************************************************/
   
   namespace ecl {
   
   /*****************************************************************************
   ** Random Number Generator
   *****************************************************************************/
   template<typename T>
   class RandomNumberGenerator
   {
   public:
     RandomNumberGenerator( const unsigned int randSeed )
     {
       srand( randSeed );
     }
   
     RandomNumberGenerator()
     {
       RandomNumberGenerator::seed();
     }
   
     T uniform( const T & range)
     {
       return (uniform()-0.5)*2.0*range;
     }
   
     T uniform()
     {
       return static_cast<T>(rand())/static_cast<T>(RAND_MAX);
     }
   
     T gaussian( const T & std, const T & mu = 0 )
     {
       T x1, x2, w, y1;
       static T y2;
       static bool use_last = false;
   
       if (use_last)  /* use value from previous call */
       {
         y1 = y2;
         use_last = false;
       }
       else
       {
         do {
             x1 = 2.0 * uniform() - 1.0;
             x2 = 2.0 * uniform() - 1.0;
             w = x1 * x1 + x2 * x2;
         } while ( w >= 1.0 );
   
         w = std::sqrt( (-2.0 * std::log( w ) ) / w );
         y1 = x1 * w;
         y2 = x2 * w;
         use_last = true;
       }
   
       return mu + y1 * std;
     }
   
   private:
     static void seed()
     {
       unsigned long a = clock();
       unsigned long b = ::time(NULL);
   
   #if defined(ECL_IS_WIN32)
       unsigned long c = GetCurrentProcessId();
   #else
       unsigned long c = getpid();
   #endif
   
       a=a-b;  a=a-c;  a=a^(c >> 13);
       b=b-c;  b=b-a;  b=b^(a << 8);
       c=c-a;  c=c-b;  c=c^(b >> 13);
       a=a-b;  a=a-c;  a=a^(c >> 12);
       b=b-c;  b=b-a;  b=b^(a << 16);
       c=c-a;  c=c-b;  c=c^(b >> 5);
       a=a-b;  a=a-c;  a=a^(c >> 3);
       b=b-c;  b=b-a;  b=b^(a << 10);
       c=c-a;  c=c-b;  c=c^(b >> 15);
       srand(c);
     }
   };
   
   } // namespace ecl
   
   
   #endif /* ECL_TIME_RANDOM_NUMBER_GENERATOR_HPP_ */