1.1 --- /dev/null	Thu Jan 01 00:00:00 1970 +0000
     1.2 +++ b/os/ossrv/ossrv_pub/boost_apis/boost/random/poisson_distribution.hpp	Fri Jun 15 03:10:57 2012 +0200
     1.3 @@ -0,0 +1,99 @@
     1.4 +/* boost random/poisson_distribution.hpp header file
     1.5 + *
     1.6 + * Copyright Jens Maurer 2002
     1.7 + * Distributed under the Boost Software License, Version 1.0. (See
     1.8 + * accompanying file LICENSE_1_0.txt or copy at
     1.9 + * http://www.boost.org/LICENSE_1_0.txt)
    1.10 + *
    1.11 + * See http://www.boost.org for most recent version including documentation.
    1.12 + *
    1.13 + * $Id: poisson_distribution.hpp,v 1.15 2005/05/21 15:57:00 dgregor Exp $
    1.14 + *
    1.15 + */
    1.16 +
    1.17 +#ifndef BOOST_RANDOM_POISSON_DISTRIBUTION_HPP
    1.18 +#define BOOST_RANDOM_POISSON_DISTRIBUTION_HPP
    1.19 +
    1.20 +#include <cmath>
    1.21 +#include <cassert>
    1.22 +#include <iostream>
    1.23 +#include <boost/limits.hpp>
    1.24 +#include <boost/static_assert.hpp>
    1.25 +
    1.26 +namespace boost {
    1.27 +
    1.28 +// Knuth
    1.29 +template<class IntType = int, class RealType = double>
    1.30 +class poisson_distribution
    1.31 +{
    1.32 +public:
    1.33 +  typedef RealType input_type;
    1.34 +  typedef IntType result_type;
    1.35 +
    1.36 +  explicit poisson_distribution(const RealType& mean = RealType(1))
    1.37 +    : _mean(mean)
    1.38 +  {
    1.39 +#ifndef BOOST_NO_LIMITS_COMPILE_TIME_CONSTANTS
    1.40 +    // MSVC fails BOOST_STATIC_ASSERT with std::numeric_limits at class scope
    1.41 +    BOOST_STATIC_ASSERT(std::numeric_limits<IntType>::is_integer);
    1.42 +    BOOST_STATIC_ASSERT(!std::numeric_limits<RealType>::is_integer);
    1.43 +#endif
    1.44 +
    1.45 +    assert(mean > RealType(0));
    1.46 +    init();
    1.47 +  }
    1.48 +
    1.49 +  // compiler-generated copy ctor and assignment operator are fine
    1.50 +
    1.51 +  RealType mean() const { return _mean; }
    1.52 +  void reset() { }
    1.53 +
    1.54 +  template<class Engine>
    1.55 +  result_type operator()(Engine& eng)
    1.56 +  {
    1.57 +    // TODO: This is O(_mean), but it should be O(log(_mean)) for large _mean
    1.58 +    RealType product = RealType(1);
    1.59 +    for(result_type m = 0; ; ++m) {
    1.60 +      product *= eng();
    1.61 +      if(product <= _exp_mean)
    1.62 +        return m;
    1.63 +    }
    1.64 +  }
    1.65 +
    1.66 +#if !defined(BOOST_NO_OPERATORS_IN_NAMESPACE) && !defined(BOOST_NO_MEMBER_TEMPLATE_FRIENDS)
    1.67 +  template<class CharT, class Traits>
    1.68 +  friend std::basic_ostream<CharT,Traits>&
    1.69 +  operator<<(std::basic_ostream<CharT,Traits>& os, const poisson_distribution& pd)
    1.70 +  {
    1.71 +    os << pd._mean;
    1.72 +    return os;
    1.73 +  }
    1.74 +
    1.75 +  template<class CharT, class Traits>
    1.76 +  friend std::basic_istream<CharT,Traits>&
    1.77 +  operator>>(std::basic_istream<CharT,Traits>& is, poisson_distribution& pd)
    1.78 +  {
    1.79 +    is >> std::ws >> pd._mean;
    1.80 +    pd.init();
    1.81 +    return is;
    1.82 +  }
    1.83 +#endif
    1.84 +
    1.85 +private:
    1.86 +  void init()
    1.87 +  {
    1.88 +#ifndef BOOST_NO_STDC_NAMESPACE
    1.89 +    // allow for Koenig lookup
    1.90 +    using std::exp;
    1.91 +#endif
    1.92 +    _exp_mean = exp(-_mean);
    1.93 +  }
    1.94 +
    1.95 +  RealType _mean;
    1.96 +  // some precomputed data from the parameters
    1.97 +  RealType _exp_mean;
    1.98 +};
    1.99 +
   1.100 +} // namespace boost
   1.101 +
   1.102 +#endif // BOOST_RANDOM_POISSON_DISTRIBUTION_HPP