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// -*- C++ -*-

// Copyright (C) 2005, 2006, 2008, 2009 Free Software Foundation, Inc.

//

// This file is part of the GNU ISO C++ Library.  This library 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 3, or (at your option) any later

// version.

// This library 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 this library; see the file COPYING3.  If not see

// <http://www.gnu.org/licenses/>.

// Copyright (C) 2004 Ami Tavory and Vladimir Dreizin, IBM-HRL.

// Permission to use, copy, modify, sell, and distribute this software

// is hereby granted without fee, provided that the above copyright

// notice appears in all copies, and that both that copyright notice

// and this permission notice appear in supporting documentation. None

// of the above authors, nor IBM Haifa Research Laboratories, make any

// representation about the suitability of this software for any

// purpose. It is provided "as is" without express or implied

// warranty.

/**

 * @file testsuite_rng.h

 */

#ifndef _GLIBCXX_TESTSUITE_RNG_H

#define _GLIBCXX_TESTSUITE_RNG_H

#include <ctime>

#include <climits>

#include <debug/debug.h>

#include <tr1/random>

namespace __gnu_pbds

{

  namespace test

  {

    class twister_rand_gen

    {

    public:

      twister_rand_gen(unsigned int seed =

                       static_cast<unsigned int>(std::time(0)))

      : m_base_generator(seed)

      {

        // Do nothing.

      }

      void

      init(unsigned int seed)

      { m_base_generator.seed(seed); }

      static unsigned int

      get_time_determined_seed()

      { return(static_cast<unsigned int>(std::time(0))); }

      unsigned long

      get_unsigned_long(unsigned long min = 0,

                        unsigned long max = UINT_MAX - 1)

      {

        _GLIBCXX_DEBUG_ASSERT(max >= min);

        const double prob = get_prob();

        const unsigned long r = (unsigned long)((max - min + 1) * prob) + min;

        _GLIBCXX_DEBUG_ASSERT(r <= max);

        return r;

      }

      double

      get_prob()

      {

        const double min = m_base_generator.min();

        const double max = m_base_generator.max();

        const double range = static_cast<const double>(max - min);

        const double res = static_cast<const double>(m_base_generator() - min);

        const double ret = res / range;

        _GLIBCXX_DEBUG_ASSERT(ret >= 0 && ret <= 1);

        return ret;

      }

    private:

      typedef std::tr1::mt19937 base_generator_t;

      base_generator_t m_base_generator;

    };

  } // namespace test

} // namespace __gnu_pbds

#endif // #ifndef _GLIBCXX_TESTSUITE_RNG_H