Chris@16: /* boost random/triangle_distribution.hpp header file
Chris@16:  *
Chris@16:  * Copyright Jens Maurer 2000-2001
Chris@16:  * Copyright Steven Watanabe 2011
Chris@16:  * Distributed under the Boost Software License, Version 1.0. (See
Chris@16:  * accompanying file LICENSE_1_0.txt or copy at
Chris@16:  * http://www.boost.org/LICENSE_1_0.txt)
Chris@16:  *
Chris@16:  * See http://www.boost.org for most recent version including documentation.
Chris@16:  *
Chris@101:  * $Id$
Chris@16:  *
Chris@16:  * Revision history
Chris@16:  *  2001-02-18  moved to individual header files
Chris@16:  */
Chris@16: 
Chris@16: #ifndef BOOST_RANDOM_TRIANGLE_DISTRIBUTION_HPP
Chris@16: #define BOOST_RANDOM_TRIANGLE_DISTRIBUTION_HPP
Chris@16: 
Chris@16: #include <boost/config/no_tr1/cmath.hpp>
Chris@16: #include <iosfwd>
Chris@16: #include <ios>
Chris@16: #include <istream>
Chris@16: #include <boost/assert.hpp>
Chris@16: #include <boost/random/detail/config.hpp>
Chris@16: #include <boost/random/detail/operators.hpp>
Chris@16: #include <boost/random/uniform_01.hpp>
Chris@16: 
Chris@16: namespace boost {
Chris@16: namespace random {
Chris@16: 
Chris@16: /**
Chris@16:  * Instantiations of @c triangle_distribution model a \random_distribution.
Chris@16:  * A @c triangle_distribution has three parameters, @c a, @c b, and @c c,
Chris@16:  * which are the smallest, the most probable and the largest values of
Chris@16:  * the distribution respectively.
Chris@16:  */
Chris@16: template<class RealType = double>
Chris@16: class triangle_distribution
Chris@16: {
Chris@16: public:
Chris@16:     typedef RealType input_type;
Chris@16:     typedef RealType result_type;
Chris@16: 
Chris@16:     class param_type
Chris@16:     {
Chris@16:     public:
Chris@16: 
Chris@16:         typedef triangle_distribution distribution_type;
Chris@16: 
Chris@16:         /** Constructs the parameters of a @c triangle_distribution. */
Chris@16:         explicit param_type(RealType a_arg = RealType(0.0),
Chris@16:                             RealType b_arg = RealType(0.5),
Chris@16:                             RealType c_arg = RealType(1.0))
Chris@16:           : _a(a_arg), _b(b_arg), _c(c_arg)
Chris@16:         {
Chris@16:             BOOST_ASSERT(_a <= _b && _b <= _c);
Chris@16:         }
Chris@16: 
Chris@16:         /** Returns the minimum value of the distribution. */
Chris@16:         RealType a() const { return _a; }
Chris@16:         /** Returns the mode of the distribution. */
Chris@16:         RealType b() const { return _b; }
Chris@16:         /** Returns the maximum value of the distribution. */
Chris@16:         RealType c() const { return _c; }
Chris@16: 
Chris@16:         /** Writes the parameters to a @c std::ostream. */
Chris@16:         BOOST_RANDOM_DETAIL_OSTREAM_OPERATOR(os, param_type, parm)
Chris@16:         {
Chris@16:             os << parm._a << " " << parm._b << " " << parm._c;
Chris@16:             return os;
Chris@16:         }
Chris@16: 
Chris@16:         /** Reads the parameters from a @c std::istream. */
Chris@16:         BOOST_RANDOM_DETAIL_ISTREAM_OPERATOR(is, param_type, parm)
Chris@16:         {
Chris@16:             double a_in, b_in, c_in;
Chris@16:             if(is >> a_in >> std::ws >> b_in >> std::ws >> c_in) {
Chris@16:                 if(a_in <= b_in && b_in <= c_in) {
Chris@16:                     parm._a = a_in;
Chris@16:                     parm._b = b_in;
Chris@16:                     parm._c = c_in;
Chris@16:                 } else {
Chris@16:                     is.setstate(std::ios_base::failbit);
Chris@16:                 }
Chris@16:             }
Chris@16:             return is;
Chris@16:         }
Chris@16: 
Chris@16:         /** Returns true if the two sets of parameters are equal. */
Chris@16:         BOOST_RANDOM_DETAIL_EQUALITY_OPERATOR(param_type, lhs, rhs)
Chris@16:         { return lhs._a == rhs._a && lhs._b == rhs._b && lhs._c == rhs._c; }
Chris@16: 
Chris@16:         /** Returns true if the two sets of parameters are different. */
Chris@16:         BOOST_RANDOM_DETAIL_INEQUALITY_OPERATOR(param_type)
Chris@16: 
Chris@16:     private:
Chris@16:         RealType _a;
Chris@16:         RealType _b;
Chris@16:         RealType _c;
Chris@16:     };
Chris@16: 
Chris@16:     /**
Chris@16:      * Constructs a @c triangle_distribution with the parameters
Chris@16:      * @c a, @c b, and @c c.
Chris@16:      *
Chris@16:      * Preconditions: a <= b <= c.
Chris@16:      */
Chris@16:     explicit triangle_distribution(RealType a_arg = RealType(0.0),
Chris@16:                                    RealType b_arg = RealType(0.5),
Chris@16:                                    RealType c_arg = RealType(1.0))
Chris@16:       : _a(a_arg), _b(b_arg), _c(c_arg)
Chris@16:     {
Chris@16:         BOOST_ASSERT(_a <= _b && _b <= _c);
Chris@16:         init();
Chris@16:     }
Chris@16: 
Chris@16:     /** Constructs a @c triangle_distribution from its parameters. */
Chris@16:     explicit triangle_distribution(const param_type& parm)
Chris@16:       : _a(parm.a()), _b(parm.b()), _c(parm.c())
Chris@16:     {
Chris@16:         init();
Chris@16:     }
Chris@16: 
Chris@16:     // compiler-generated copy ctor and assignment operator are fine
Chris@16: 
Chris@16:     /** Returns the @c a parameter of the distribution */
Chris@16:     result_type a() const { return _a; }
Chris@16:     /** Returns the @c b parameter of the distribution */
Chris@16:     result_type b() const { return _b; }
Chris@16:     /** Returns the @c c parameter of the distribution */
Chris@16:     result_type c() const { return _c; }
Chris@16: 
Chris@16:     /** Returns the smallest value that the distribution can produce. */
Chris@16:     RealType min BOOST_PREVENT_MACRO_SUBSTITUTION () const { return _a; }
Chris@16:     /** Returns the largest value that the distribution can produce. */
Chris@16:     RealType max BOOST_PREVENT_MACRO_SUBSTITUTION () const { return _c; }
Chris@16: 
Chris@16:     /** Returns the parameters of the distribution. */
Chris@16:     param_type param() const { return param_type(_a, _b, _c); }
Chris@16:     /** Sets the parameters of the distribution. */
Chris@16:     void param(const param_type& parm)
Chris@16:     {
Chris@16:         _a = parm.a();
Chris@16:         _b = parm.b();
Chris@16:         _c = parm.c();
Chris@16:         init();
Chris@16:     }
Chris@16: 
Chris@16:     /**
Chris@16:      * Effects: Subsequent uses of the distribution do not depend
Chris@16:      * on values produced by any engine prior to invoking reset.
Chris@16:      */
Chris@16:     void reset() { }
Chris@16: 
Chris@16:     /**
Chris@16:      * Returns a random variate distributed according to the
Chris@16:      * triangle distribution.
Chris@16:      */
Chris@16:     template<class Engine>
Chris@16:     result_type operator()(Engine& eng)
Chris@16:     {
Chris@16:         using std::sqrt;
Chris@16:         result_type u = uniform_01<>()(eng);
Chris@16:         if( u <= q1 )
Chris@16:             return _a + p1*sqrt(u);
Chris@16:         else
Chris@16:         return _c - d3*sqrt(d2*u-d1);
Chris@16:     }
Chris@16: 
Chris@16:     /**
Chris@16:      * Returns a random variate distributed according to the
Chris@16:      * triangle distribution with parameters specified by param.
Chris@16:      */
Chris@16:     template<class Engine>
Chris@16:     result_type operator()(Engine& eng, const param_type& parm)
Chris@16:     { return triangle_distribution(parm)(eng); }
Chris@16: 
Chris@16:     /** Writes the distribution to a @c std::ostream. */
Chris@16:     BOOST_RANDOM_DETAIL_OSTREAM_OPERATOR(os, triangle_distribution, td)
Chris@16:     {
Chris@16:         os << td.param();
Chris@16:         return os;
Chris@16:     }
Chris@16: 
Chris@16:     /** Reads the distribution from a @c std::istream. */
Chris@16:     BOOST_RANDOM_DETAIL_ISTREAM_OPERATOR(is, triangle_distribution, td)
Chris@16:     {
Chris@16:         param_type parm;
Chris@16:         if(is >> parm) {
Chris@16:             td.param(parm);
Chris@16:         }
Chris@16:         return is;
Chris@16:     }
Chris@16: 
Chris@16:     /**
Chris@16:      * Returns true if the two distributions will produce identical
Chris@16:      * sequences of values given equal generators.
Chris@16:      */
Chris@16:     BOOST_RANDOM_DETAIL_EQUALITY_OPERATOR(triangle_distribution, lhs, rhs)
Chris@16:     { return lhs._a == rhs._a && lhs._b == rhs._b && lhs._c == rhs._c; }
Chris@16: 
Chris@16:     /**
Chris@16:      * Returns true if the two distributions may produce different
Chris@16:      * sequences of values given equal generators.
Chris@16:      */
Chris@16:     BOOST_RANDOM_DETAIL_INEQUALITY_OPERATOR(triangle_distribution)
Chris@16: 
Chris@16: private:
Chris@16:     /// \cond show_private
Chris@16:     void init()
Chris@16:     {
Chris@16:         using std::sqrt;
Chris@16:         d1 = _b - _a;
Chris@16:         d2 = _c - _a;
Chris@16:         d3 = sqrt(_c - _b);
Chris@16:         q1 = d1 / d2;
Chris@16:         p1 = sqrt(d1 * d2);
Chris@16:     }
Chris@16:     /// \endcond
Chris@16: 
Chris@16:     RealType _a, _b, _c;
Chris@16:     RealType d1, d2, d3, q1, p1;
Chris@16: };
Chris@16: 
Chris@16: } // namespace random
Chris@16: 
Chris@16: using random::triangle_distribution;
Chris@16: 
Chris@16: } // namespace boost
Chris@16: 
Chris@16: #endif // BOOST_RANDOM_TRIANGLE_DISTRIBUTION_HPP