/usr/include/boost/random
Edit: /usr/include/boost/random/weibull_distribution.hpp (5524B)
/* boost random/weibull_distribution.hpp header file
*
* Copyright Steven Watanabe 2010
* Distributed under the Boost Software License, Version 1.0. (See
* accompanying file LICENSE_1_0.txt or copy at
* http://www.boost.org/LICENSE_1_0.txt)
*
* See http://www.boost.org for most recent version including documentation.
*
* $Id$
*/
#ifndef BOOST_RANDOM_WEIBULL_DISTRIBUTION_HPP
#define BOOST_RANDOM_WEIBULL_DISTRIBUTION_HPP
#include
#include
#include
#include
#include
#include
#include
namespace boost {
namespace random {
/**
* The Weibull distribution is a real valued distribution with two
* parameters a and b, producing values >= 0.
*
* It has \f$\displaystyle p(x) = \frac{a}{b}\left(\frac{x}{b}\right)^{a-1}e^{-\left(\frac{x}{b}\right)^a}\f$.
*/
template
class weibull_distribution {
public:
typedef RealType result_type;
typedef RealType input_type;
class param_type {
public:
typedef weibull_distribution distribution_type;
/**
* Constructs a @c param_type from the "a" and "b" parameters
* of the distribution.
*
* Requires: a > 0 && b > 0
*/
explicit param_type(RealType a_arg = 1.0, RealType b_arg = 1.0)
: _a(a_arg), _b(b_arg)
{}
/** Returns the "a" parameter of the distribtuion. */
RealType a() const { return _a; }
/** Returns the "b" parameter of the distribution. */
RealType b() const { return _b; }
/** Writes a @c param_type to a @c std::ostream. */
BOOST_RANDOM_DETAIL_OSTREAM_OPERATOR(os, param_type, parm)
{ os << parm._a << ' ' << parm._b; return os; }
/** Reads a @c param_type from a @c std::istream. */
BOOST_RANDOM_DETAIL_ISTREAM_OPERATOR(is, param_type, parm)
{ is >> parm._a >> std::ws >> parm._b; return is; }
/** Returns true if the two sets of parameters are the same. */
BOOST_RANDOM_DETAIL_EQUALITY_OPERATOR(param_type, lhs, rhs)
{ return lhs._a == rhs._a && lhs._b == rhs._b; }
/** Returns true if the two sets of parameters are the different. */
BOOST_RANDOM_DETAIL_INEQUALITY_OPERATOR(param_type)
private:
RealType _a;
RealType _b;
};
/**
* Constructs a @c weibull_distribution from its "a" and "b" parameters.
*
* Requires: a > 0 && b > 0
*/
explicit weibull_distribution(RealType a_arg = 1.0, RealType b_arg = 1.0)
: _a(a_arg), _b(b_arg)
{}
/** Constructs a @c weibull_distribution from its parameters. */
explicit weibull_distribution(const param_type& parm)
: _a(parm.a()), _b(parm.b())
{}
/**
* Returns a random variate distributed according to the
* @c weibull_distribution.
*/
template
RealType operator()(URNG& urng) const
{
using std::pow;
using std::log;
return _b*pow(-log(1 - uniform_01()(urng)), 1/_a);
}
/**
* Returns a random variate distributed accordint to the Weibull
* distribution with parameters specified by @c param.
*/
template
RealType operator()(URNG& urng, const param_type& parm) const
{
return weibull_distribution(parm)(urng);
}
/** Returns the "a" parameter of the distribution. */
RealType a() const { return _a; }
/** Returns the "b" parameter of the distribution. */
RealType b() const { return _b; }
/** Returns the smallest value that the distribution can produce. */
RealType min BOOST_PREVENT_MACRO_SUBSTITUTION () const { return 0; }
/** Returns the largest value that the distribution can produce. */
RealType max BOOST_PREVENT_MACRO_SUBSTITUTION () const
{ return std::numeric_limits::infinity(); }
/** Returns the parameters of the distribution. */
param_type param() const { return param_type(_a, _b); }
/** Sets the parameters of the distribution. */
void param(const param_type& parm)
{
_a = parm.a();
_b = parm.b();
}
/**
* Effects: Subsequent uses of the distribution do not depend
* on values produced by any engine prior to invoking reset.
*/
void reset() { }
/** Writes a @c weibull_distribution to a @c std::ostream. */
BOOST_RANDOM_DETAIL_OSTREAM_OPERATOR(os, weibull_distribution, wd)
{
os << wd.param();
return os;
}
/** Reads a @c weibull_distribution from a @c std::istream. */
BOOST_RANDOM_DETAIL_ISTREAM_OPERATOR(is, weibull_distribution, wd)
{
param_type parm;
if(is >> parm) {
wd.param(parm);
}
return is;
}
/**
* Returns true if the two instances of @c weibull_distribution will
* return identical sequences of values given equal generators.
*/
BOOST_RANDOM_DETAIL_EQUALITY_OPERATOR(weibull_distribution, lhs, rhs)
{ return lhs._a == rhs._a && lhs._b == rhs._b; }
/**
* Returns true if the two instances of @c weibull_distribution will
* return different sequences of values given equal generators.
*/
BOOST_RANDOM_DETAIL_INEQUALITY_OPERATOR(weibull_distribution)
private:
RealType _a;
RealType _b;
};
} // namespace random
} // namespace boost
#endif // BOOST_RANDOM_WEIBULL_DISTRIBUTION_HPP