| /* boost random/triangle_distribution.hpp header file |
| * |
| * Copyright Jens Maurer 2000-2001 |
| * Copyright Steven Watanabe 2011 |
| * 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. |
| * |
| * $Id$ |
| * |
| * Revision history |
| * 2001-02-18 moved to individual header files |
| */ |
| |
| #ifndef BOOST_RANDOM_TRIANGLE_DISTRIBUTION_HPP |
| #define BOOST_RANDOM_TRIANGLE_DISTRIBUTION_HPP |
| |
| #include <boost/config/no_tr1/cmath.hpp> |
| #include <iosfwd> |
| #include <ios> |
| #include <istream> |
| #include <boost/assert.hpp> |
| #include <boost/random/detail/config.hpp> |
| #include <boost/random/detail/operators.hpp> |
| #include <boost/random/uniform_01.hpp> |
| |
| namespace boost { |
| namespace random { |
| |
| /** |
| * Instantiations of @c triangle_distribution model a \random_distribution. |
| * A @c triangle_distribution has three parameters, @c a, @c b, and @c c, |
| * which are the smallest, the most probable and the largest values of |
| * the distribution respectively. |
| */ |
| template<class RealType = double> |
| class triangle_distribution |
| { |
| public: |
| typedef RealType input_type; |
| typedef RealType result_type; |
| |
| class param_type |
| { |
| public: |
| |
| typedef triangle_distribution distribution_type; |
| |
| /** Constructs the parameters of a @c triangle_distribution. */ |
| explicit param_type(RealType a_arg = RealType(0.0), |
| RealType b_arg = RealType(0.5), |
| RealType c_arg = RealType(1.0)) |
| : _a(a_arg), _b(b_arg), _c(c_arg) |
| { |
| BOOST_ASSERT(_a <= _b && _b <= _c); |
| } |
| |
| /** Returns the minimum value of the distribution. */ |
| RealType a() const { return _a; } |
| /** Returns the mode of the distribution. */ |
| RealType b() const { return _b; } |
| /** Returns the maximum value of the distribution. */ |
| RealType c() const { return _c; } |
| |
| /** Writes the parameters to a @c std::ostream. */ |
| BOOST_RANDOM_DETAIL_OSTREAM_OPERATOR(os, param_type, parm) |
| { |
| os << parm._a << " " << parm._b << " " << parm._c; |
| return os; |
| } |
| |
| /** Reads the parameters from a @c std::istream. */ |
| BOOST_RANDOM_DETAIL_ISTREAM_OPERATOR(is, param_type, parm) |
| { |
| double a_in, b_in, c_in; |
| if(is >> a_in >> std::ws >> b_in >> std::ws >> c_in) { |
| if(a_in <= b_in && b_in <= c_in) { |
| parm._a = a_in; |
| parm._b = b_in; |
| parm._c = c_in; |
| } else { |
| is.setstate(std::ios_base::failbit); |
| } |
| } |
| return is; |
| } |
| |
| /** Returns true if the two sets of parameters are equal. */ |
| BOOST_RANDOM_DETAIL_EQUALITY_OPERATOR(param_type, lhs, rhs) |
| { return lhs._a == rhs._a && lhs._b == rhs._b && lhs._c == rhs._c; } |
| |
| /** Returns true if the two sets of parameters are different. */ |
| BOOST_RANDOM_DETAIL_INEQUALITY_OPERATOR(param_type) |
| |
| private: |
| RealType _a; |
| RealType _b; |
| RealType _c; |
| }; |
| |
| /** |
| * Constructs a @c triangle_distribution with the parameters |
| * @c a, @c b, and @c c. |
| * |
| * Preconditions: a <= b <= c. |
| */ |
| explicit triangle_distribution(RealType a_arg = RealType(0.0), |
| RealType b_arg = RealType(0.5), |
| RealType c_arg = RealType(1.0)) |
| : _a(a_arg), _b(b_arg), _c(c_arg) |
| { |
| BOOST_ASSERT(_a <= _b && _b <= _c); |
| init(); |
| } |
| |
| /** Constructs a @c triangle_distribution from its parameters. */ |
| explicit triangle_distribution(const param_type& parm) |
| : _a(parm.a()), _b(parm.b()), _c(parm.c()) |
| { |
| init(); |
| } |
| |
| // compiler-generated copy ctor and assignment operator are fine |
| |
| /** Returns the @c a parameter of the distribution */ |
| result_type a() const { return _a; } |
| /** Returns the @c b parameter of the distribution */ |
| result_type b() const { return _b; } |
| /** Returns the @c c parameter of the distribution */ |
| result_type c() const { return _c; } |
| |
| /** Returns the smallest value that the distribution can produce. */ |
| RealType min BOOST_PREVENT_MACRO_SUBSTITUTION () const { return _a; } |
| /** Returns the largest value that the distribution can produce. */ |
| RealType max BOOST_PREVENT_MACRO_SUBSTITUTION () const { return _c; } |
| |
| /** Returns the parameters of the distribution. */ |
| param_type param() const { return param_type(_a, _b, _c); } |
| /** Sets the parameters of the distribution. */ |
| void param(const param_type& parm) |
| { |
| _a = parm.a(); |
| _b = parm.b(); |
| _c = parm.c(); |
| init(); |
| } |
| |
| /** |
| * Effects: Subsequent uses of the distribution do not depend |
| * on values produced by any engine prior to invoking reset. |
| */ |
| void reset() { } |
| |
| /** |
| * Returns a random variate distributed according to the |
| * triangle distribution. |
| */ |
| template<class Engine> |
| result_type operator()(Engine& eng) |
| { |
| using std::sqrt; |
| result_type u = uniform_01<result_type>()(eng); |
| if( u <= q1 ) |
| return _a + p1*sqrt(u); |
| else |
| return _c - d3*sqrt(d2*u-d1); |
| } |
| |
| /** |
| * Returns a random variate distributed according to the |
| * triangle distribution with parameters specified by param. |
| */ |
| template<class Engine> |
| result_type operator()(Engine& eng, const param_type& parm) |
| { return triangle_distribution(parm)(eng); } |
| |
| /** Writes the distribution to a @c std::ostream. */ |
| BOOST_RANDOM_DETAIL_OSTREAM_OPERATOR(os, triangle_distribution, td) |
| { |
| os << td.param(); |
| return os; |
| } |
| |
| /** Reads the distribution from a @c std::istream. */ |
| BOOST_RANDOM_DETAIL_ISTREAM_OPERATOR(is, triangle_distribution, td) |
| { |
| param_type parm; |
| if(is >> parm) { |
| td.param(parm); |
| } |
| return is; |
| } |
| |
| /** |
| * Returns true if the two distributions will produce identical |
| * sequences of values given equal generators. |
| */ |
| BOOST_RANDOM_DETAIL_EQUALITY_OPERATOR(triangle_distribution, lhs, rhs) |
| { return lhs._a == rhs._a && lhs._b == rhs._b && lhs._c == rhs._c; } |
| |
| /** |
| * Returns true if the two distributions may produce different |
| * sequences of values given equal generators. |
| */ |
| BOOST_RANDOM_DETAIL_INEQUALITY_OPERATOR(triangle_distribution) |
| |
| private: |
| /// \cond show_private |
| void init() |
| { |
| using std::sqrt; |
| d1 = _b - _a; |
| d2 = _c - _a; |
| d3 = sqrt(_c - _b); |
| q1 = d1 / d2; |
| p1 = sqrt(d1 * d2); |
| } |
| /// \endcond |
| |
| RealType _a, _b, _c; |
| RealType d1, d2, d3, q1, p1; |
| }; |
| |
| } // namespace random |
| |
| using random::triangle_distribution; |
| |
| } // namespace boost |
| |
| #endif // BOOST_RANDOM_TRIANGLE_DISTRIBUTION_HPP |