1 | /* boost random/triangle_distribution.hpp header file |
2 | * |
3 | * Copyright Jens Maurer 2000-2001 |
4 | * Copyright Steven Watanabe 2011 |
5 | * Distributed under the Boost Software License, Version 1.0. (See |
6 | * accompanying file LICENSE_1_0.txt or copy at |
7 | * http://www.boost.org/LICENSE_1_0.txt) |
8 | * |
9 | * See http://www.boost.org for most recent version including documentation. |
10 | * |
11 | * $Id$ |
12 | * |
13 | * Revision history |
14 | * 2001-02-18 moved to individual header files |
15 | */ |
16 | |
17 | #ifndef BOOST_RANDOM_TRIANGLE_DISTRIBUTION_HPP |
18 | #define BOOST_RANDOM_TRIANGLE_DISTRIBUTION_HPP |
19 | |
20 | #include <boost/config/no_tr1/cmath.hpp> |
21 | #include <iosfwd> |
22 | #include <ios> |
23 | #include <istream> |
24 | #include <boost/assert.hpp> |
25 | #include <boost/random/detail/config.hpp> |
26 | #include <boost/random/detail/operators.hpp> |
27 | #include <boost/random/uniform_01.hpp> |
28 | |
29 | namespace boost { |
30 | namespace random { |
31 | |
32 | /** |
33 | * Instantiations of @c triangle_distribution model a \random_distribution. |
34 | * A @c triangle_distribution has three parameters, @c a, @c b, and @c c, |
35 | * which are the smallest, the most probable and the largest values of |
36 | * the distribution respectively. |
37 | */ |
38 | template<class RealType = double> |
39 | class triangle_distribution |
40 | { |
41 | public: |
42 | typedef RealType input_type; |
43 | typedef RealType result_type; |
44 | |
45 | class param_type |
46 | { |
47 | public: |
48 | |
49 | typedef triangle_distribution distribution_type; |
50 | |
51 | /** Constructs the parameters of a @c triangle_distribution. */ |
52 | explicit param_type(RealType a_arg = RealType(0.0), |
53 | RealType b_arg = RealType(0.5), |
54 | RealType c_arg = RealType(1.0)) |
55 | : _a(a_arg), _b(b_arg), _c(c_arg) |
56 | { |
57 | BOOST_ASSERT(_a <= _b && _b <= _c); |
58 | } |
59 | |
60 | /** Returns the minimum value of the distribution. */ |
61 | RealType a() const { return _a; } |
62 | /** Returns the mode of the distribution. */ |
63 | RealType b() const { return _b; } |
64 | /** Returns the maximum value of the distribution. */ |
65 | RealType c() const { return _c; } |
66 | |
67 | /** Writes the parameters to a @c std::ostream. */ |
68 | BOOST_RANDOM_DETAIL_OSTREAM_OPERATOR(os, param_type, parm) |
69 | { |
70 | os << parm._a << " " << parm._b << " " << parm._c; |
71 | return os; |
72 | } |
73 | |
74 | /** Reads the parameters from a @c std::istream. */ |
75 | BOOST_RANDOM_DETAIL_ISTREAM_OPERATOR(is, param_type, parm) |
76 | { |
77 | double a_in, b_in, c_in; |
78 | if(is >> a_in >> std::ws >> b_in >> std::ws >> c_in) { |
79 | if(a_in <= b_in && b_in <= c_in) { |
80 | parm._a = a_in; |
81 | parm._b = b_in; |
82 | parm._c = c_in; |
83 | } else { |
84 | is.setstate(std::ios_base::failbit); |
85 | } |
86 | } |
87 | return is; |
88 | } |
89 | |
90 | /** Returns true if the two sets of parameters are equal. */ |
91 | BOOST_RANDOM_DETAIL_EQUALITY_OPERATOR(param_type, lhs, rhs) |
92 | { return lhs._a == rhs._a && lhs._b == rhs._b && lhs._c == rhs._c; } |
93 | |
94 | /** Returns true if the two sets of parameters are different. */ |
95 | BOOST_RANDOM_DETAIL_INEQUALITY_OPERATOR(param_type) |
96 | |
97 | private: |
98 | RealType _a; |
99 | RealType _b; |
100 | RealType _c; |
101 | }; |
102 | |
103 | /** |
104 | * Constructs a @c triangle_distribution with the parameters |
105 | * @c a, @c b, and @c c. |
106 | * |
107 | * Preconditions: a <= b <= c. |
108 | */ |
109 | explicit triangle_distribution(RealType a_arg = RealType(0.0), |
110 | RealType b_arg = RealType(0.5), |
111 | RealType c_arg = RealType(1.0)) |
112 | : _a(a_arg), _b(b_arg), _c(c_arg) |
113 | { |
114 | BOOST_ASSERT(_a <= _b && _b <= _c); |
115 | init(); |
116 | } |
117 | |
118 | /** Constructs a @c triangle_distribution from its parameters. */ |
119 | explicit triangle_distribution(const param_type& parm) |
120 | : _a(parm.a()), _b(parm.b()), _c(parm.c()) |
121 | { |
122 | init(); |
123 | } |
124 | |
125 | // compiler-generated copy ctor and assignment operator are fine |
126 | |
127 | /** Returns the @c a parameter of the distribution */ |
128 | result_type a() const { return _a; } |
129 | /** Returns the @c b parameter of the distribution */ |
130 | result_type b() const { return _b; } |
131 | /** Returns the @c c parameter of the distribution */ |
132 | result_type c() const { return _c; } |
133 | |
134 | /** Returns the smallest value that the distribution can produce. */ |
135 | RealType min BOOST_PREVENT_MACRO_SUBSTITUTION () const { return _a; } |
136 | /** Returns the largest value that the distribution can produce. */ |
137 | RealType max BOOST_PREVENT_MACRO_SUBSTITUTION () const { return _c; } |
138 | |
139 | /** Returns the parameters of the distribution. */ |
140 | param_type param() const { return param_type(_a, _b, _c); } |
141 | /** Sets the parameters of the distribution. */ |
142 | void param(const param_type& parm) |
143 | { |
144 | _a = parm.a(); |
145 | _b = parm.b(); |
146 | _c = parm.c(); |
147 | init(); |
148 | } |
149 | |
150 | /** |
151 | * Effects: Subsequent uses of the distribution do not depend |
152 | * on values produced by any engine prior to invoking reset. |
153 | */ |
154 | void reset() { } |
155 | |
156 | /** |
157 | * Returns a random variate distributed according to the |
158 | * triangle distribution. |
159 | */ |
160 | template<class Engine> |
161 | result_type operator()(Engine& eng) |
162 | { |
163 | using std::sqrt; |
164 | result_type u = uniform_01<result_type>()(eng); |
165 | if( u <= q1 ) |
166 | return _a + p1*sqrt(u); |
167 | else |
168 | return _c - d3*sqrt(d2*u-d1); |
169 | } |
170 | |
171 | /** |
172 | * Returns a random variate distributed according to the |
173 | * triangle distribution with parameters specified by param. |
174 | */ |
175 | template<class Engine> |
176 | result_type operator()(Engine& eng, const param_type& parm) |
177 | { return triangle_distribution(parm)(eng); } |
178 | |
179 | /** Writes the distribution to a @c std::ostream. */ |
180 | BOOST_RANDOM_DETAIL_OSTREAM_OPERATOR(os, triangle_distribution, td) |
181 | { |
182 | os << td.param(); |
183 | return os; |
184 | } |
185 | |
186 | /** Reads the distribution from a @c std::istream. */ |
187 | BOOST_RANDOM_DETAIL_ISTREAM_OPERATOR(is, triangle_distribution, td) |
188 | { |
189 | param_type parm; |
190 | if(is >> parm) { |
191 | td.param(parm); |
192 | } |
193 | return is; |
194 | } |
195 | |
196 | /** |
197 | * Returns true if the two distributions will produce identical |
198 | * sequences of values given equal generators. |
199 | */ |
200 | BOOST_RANDOM_DETAIL_EQUALITY_OPERATOR(triangle_distribution, lhs, rhs) |
201 | { return lhs._a == rhs._a && lhs._b == rhs._b && lhs._c == rhs._c; } |
202 | |
203 | /** |
204 | * Returns true if the two distributions may produce different |
205 | * sequences of values given equal generators. |
206 | */ |
207 | BOOST_RANDOM_DETAIL_INEQUALITY_OPERATOR(triangle_distribution) |
208 | |
209 | private: |
210 | /// \cond show_private |
211 | void init() |
212 | { |
213 | using std::sqrt; |
214 | d1 = _b - _a; |
215 | d2 = _c - _a; |
216 | d3 = sqrt(_c - _b); |
217 | q1 = d1 / d2; |
218 | p1 = sqrt(d1 * d2); |
219 | } |
220 | /// \endcond |
221 | |
222 | RealType _a, _b, _c; |
223 | RealType d1, d2, d3, q1, p1; |
224 | }; |
225 | |
226 | } // namespace random |
227 | |
228 | using random::triangle_distribution; |
229 | |
230 | } // namespace boost |
231 | |
232 | #endif // BOOST_RANDOM_TRIANGLE_DISTRIBUTION_HPP |
233 | |