random.hh

// -*- coding: utf-8 -*-
// Copyright (C) by the Spot authors, see the AUTHORS file for details.
//
// This file is part of Spot, a model checking library.
//
// Spot 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 of the License, or
// (at your option) any later version.
//
// Spot 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 program.  If not, see <http://www.gnu.org/licenses/>.
 
#pragma once
 
#include <spot/misc/common.hh>
#include <cassert>
#include <cmath>
#include <vector>
 
namespace spot
{
 
 
  SPOT_API void srand(unsigned int seed);
 
  SPOT_API int rrand(int min, int max);
 
  SPOT_API int mrand(int max);
 
  SPOT_API double drand();
 
  SPOT_API double nrand();
 
  template<double (*gen)()>
  class barand
  {
  public:
    barand(int n, double p)
      : n_(n), m_(n * p), s_(sqrt(n * p * (1 - p)))
    {
    }
 
    int
    rand() const
    {
      for (;;)
        {
          int x = round(gen() * s_ + m_);
          if (x < 0)
            continue;
          if (x <= n_)
            return x;
        }
      SPOT_UNREACHABLE();
      return 0;
    }
  protected:
    const int n_;     
    const double m_;  
    const double s_;  
  };
 
  template<class iterator_type>
  SPOT_API void mrandom_shuffle(iterator_type&& first, iterator_type&& last)
  {
    auto d = std::distance(first, last);
    if (d > 1)
      {
        for (--last; first < last; ++first, --d)
          {
            auto i = mrand(d);
            std::swap(*first, *(first + i));
          }
      }
  }
}