white_gaussian.hh

// Copyright (C) 2010 EPITA Research and Development Laboratory (LRDE)
//
// This file is part of Olena.
//
// Olena 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, version 2 of the License.
//
// Olena 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 Olena.  If not, see <http://www.gnu.org/licenses/>.
//
// As a special exception, you may use this file as part of a free
// software project without restriction.  Specifically, if other files
// instantiate templates or use macros or inline functions from this
// file, or you compile this file and link it with other files to produce
// an executable, this file does not by itself cause the resulting
// executable to be covered by the GNU General Public License.  This
// exception does not however invalidate any other reasons why the
// executable file might be covered by the GNU General Public License.

#ifndef MLN_FUN_N2V_WHITE_GAUSSIAN_HH
# define MLN_FUN_N2V_WHITE_GAUSSIAN_HH


# include <cstdlib>
# include <ctime>

# include <mln/core/concept/function.hh>
# include <mln/math/sqrt.hh>


namespace mln
{

  namespace fun
  {

    namespace n2v
    {

      template <typename V>
      struct white_gaussian : Function_n2v< white_gaussian<V> >
      {
        typedef V result;

        white_gaussian(double sigma_);
        V operator()() const;

        double sigma;
      };


# ifndef MLN_INCLUDE_ONLY


      template <typename V>
      white_gaussian<V>::white_gaussian(double sigma_)
        : sigma(sigma_)
      {
        srand(time(0));
      }


      template <typename V>
      V white_gaussian<V>::operator()() const
      {
        double X = 0;
        for (int i = 1; i < 50; ++i)
        {
          double U = rand() / (float)RAND_MAX;
          X = X + U;
        }

        X = X - 25.f;                /* set mean to 0 */
        X = X * math::sqrt(12 / 50.f);     /* adjust variance to 1 */

        return sigma * X;
      };


# endif // ! MLN_INCLUDE_ONLY

    } // end of namespace mln::fun::n2v

  } // end of namespace mln::fun

} // end of namespace mln


#endif // ! MLN_FUN_N2V_WHITE_GAUSSIAN_HH