1 /* boost random/linear_congruential.hpp header file
3 * Copyright Jens Maurer 2000-2001
4 * Distributed under the Boost Software License, Version 1.0. (See
5 * accompanying file LICENSE_1_0.txt or copy at
6 * http://www.boost.org/LICENSE_1_0.txt)
8 * See http://www.boost.org for most recent version including documentation.
10 * $Id: linear_congruential.hpp,v 1.22 2005/05/21 15:57:00 dgregor Exp $
13 * 2001-02-18 moved to individual header files
16 #ifndef BOOST_RANDOM_LINEAR_CONGRUENTIAL_HPP
17 #define BOOST_RANDOM_LINEAR_CONGRUENTIAL_HPP
22 #include <boost/config.hpp>
23 #include <boost/limits.hpp>
24 #include <boost/static_assert.hpp>
25 #include <boost/random/detail/const_mod.hpp>
26 #include <boost/detail/workaround.hpp>
31 // compile-time configurable linear congruential generator
32 template<class IntType, IntType a, IntType c, IntType m, IntType val>
33 class linear_congruential
36 typedef IntType result_type;
37 #ifndef BOOST_NO_INCLASS_MEMBER_INITIALIZATION
38 static const bool has_fixed_range = true;
39 static const result_type min_value = ( c == 0 ? 1 : 0 );
40 static const result_type max_value = m-1;
42 BOOST_STATIC_CONSTANT(bool, has_fixed_range = false);
44 BOOST_STATIC_CONSTANT(IntType, multiplier = a);
45 BOOST_STATIC_CONSTANT(IntType, increment = c);
46 BOOST_STATIC_CONSTANT(IntType, modulus = m);
48 // MSVC 6 and possibly others crash when encountering complicated integral
49 // constant expressions. Avoid the check for now.
50 // BOOST_STATIC_ASSERT(m == 0 || a < m);
51 // BOOST_STATIC_ASSERT(m == 0 || c < m);
53 explicit linear_congruential(IntType x0 = 1)
54 : _modulus(modulus), _x(_modulus ? (x0 % _modulus) : x0)
56 assert(c || x0); /* if c == 0 and x(0) == 0 then x(n) = 0 for all n */
58 // disabled because it gives spurious "divide by zero" gcc warnings
59 // assert(m == 0 || (a*(m-1)+c) % m == (c < a ? c-a+m : c-a));
61 // MSVC fails BOOST_STATIC_ASSERT with std::numeric_limits at class scope
62 #ifndef BOOST_NO_LIMITS_COMPILE_TIME_CONSTANTS
63 BOOST_STATIC_ASSERT(std::numeric_limits<IntType>::is_integer);
68 linear_congruential(It& first, It last) { seed(first, last); }
70 // compiler-generated copy constructor and assignment operator are fine
71 void seed(IntType x0 = 1)
74 _x = (_modulus ? (x0 % _modulus) : x0);
78 void seed(It& first, It last)
81 throw std::invalid_argument("linear_congruential::seed");
82 IntType value = *first++;
83 _x = (_modulus ? (value % _modulus) : value);
86 result_type min BOOST_PREVENT_MACRO_SUBSTITUTION () const { return c == 0 ? 1 : 0; }
87 result_type max BOOST_PREVENT_MACRO_SUBSTITUTION () const { return modulus-1; }
91 _x = const_mod<IntType, m>::mult_add(a, _x, c);
95 static bool validation(IntType x) { return val == x; }
97 #ifdef BOOST_NO_OPERATORS_IN_NAMESPACE
99 // Use a member function; Streamable concept not supported.
100 bool operator==(const linear_congruential& rhs) const
101 { return _x == rhs._x; }
102 bool operator!=(const linear_congruential& rhs) const
103 { return !(*this == rhs); }
106 friend bool operator==(const linear_congruential& x,
107 const linear_congruential& y)
108 { return x._x == y._x; }
109 friend bool operator!=(const linear_congruential& x,
110 const linear_congruential& y)
111 { return !(x == y); }
113 #if !defined(BOOST_NO_MEMBER_TEMPLATE_FRIENDS) && !BOOST_WORKAROUND(__BORLANDC__, BOOST_TESTED_AT(0x551))
114 template<class CharT, class Traits>
115 friend std::basic_ostream<CharT,Traits>&
116 operator<<(std::basic_ostream<CharT,Traits>& os,
117 const linear_congruential& lcg)
122 template<class CharT, class Traits>
123 friend std::basic_istream<CharT,Traits>&
124 operator>>(std::basic_istream<CharT,Traits>& is,
125 linear_congruential& lcg)
134 IntType _modulus; // work-around for gcc "divide by zero" warning in ctor
138 // probably needs the "no native streams" caveat for STLPort
139 #if !defined(__SGI_STL_PORT) && BOOST_WORKAROUND(__GNUC__, == 2)
140 template<class IntType, IntType a, IntType c, IntType m, IntType val>
142 operator<<(std::ostream& os,
143 const linear_congruential<IntType,a,c,m,val>& lcg)
148 template<class IntType, IntType a, IntType c, IntType m, IntType val>
150 operator>>(std::istream& is,
151 linear_congruential<IntType,a,c,m,val>& lcg)
155 #elif defined(BOOST_NO_OPERATORS_IN_NAMESPACE) || defined(BOOST_NO_MEMBER_TEMPLATE_FRIENDS) || BOOST_WORKAROUND(__BORLANDC__, BOOST_TESTED_AT(0x551))
156 template<class CharT, class Traits, class IntType, IntType a, IntType c, IntType m, IntType val>
157 std::basic_ostream<CharT,Traits>&
158 operator<<(std::basic_ostream<CharT,Traits>& os,
159 const linear_congruential<IntType,a,c,m,val>& lcg)
164 template<class CharT, class Traits, class IntType, IntType a, IntType c, IntType m, IntType val>
165 std::basic_istream<CharT,Traits>&
166 operator>>(std::basic_istream<CharT,Traits>& is,
167 linear_congruential<IntType,a,c,m,val>& lcg)
173 #ifndef BOOST_NO_INCLASS_MEMBER_INITIALIZATION
174 // A definition is required even for integral static constants
175 template<class IntType, IntType a, IntType c, IntType m, IntType val>
176 const bool linear_congruential<IntType, a, c, m, val>::has_fixed_range;
177 template<class IntType, IntType a, IntType c, IntType m, IntType val>
178 const typename linear_congruential<IntType, a, c, m, val>::result_type linear_congruential<IntType, a, c, m, val>::min_value;
179 template<class IntType, IntType a, IntType c, IntType m, IntType val>
180 const typename linear_congruential<IntType, a, c, m, val>::result_type linear_congruential<IntType, a, c, m, val>::max_value;
181 template<class IntType, IntType a, IntType c, IntType m, IntType val>
182 const IntType linear_congruential<IntType,a,c,m,val>::modulus;
185 } // namespace random
187 // validation values from the publications
188 typedef random::linear_congruential<int32_t, 16807, 0, 2147483647,
189 1043618065> minstd_rand0;
190 typedef random::linear_congruential<int32_t, 48271, 0, 2147483647,
191 399268537> minstd_rand;
194 #if !defined(BOOST_NO_INT64_T) && !defined(BOOST_NO_INTEGRAL_INT64_T)
195 // emulate the lrand48() C library function; requires support for uint64_t
199 typedef int32_t result_type;
200 #ifndef BOOST_NO_INCLASS_MEMBER_INITIALIZATION
201 static const bool has_fixed_range = true;
202 static const int32_t min_value = 0;
203 static const int32_t max_value = integer_traits<int32_t>::const_max;
205 enum { has_fixed_range = false };
207 int32_t min BOOST_PREVENT_MACRO_SUBSTITUTION () const { return 0; }
208 int32_t max BOOST_PREVENT_MACRO_SUBSTITUTION () const { return std::numeric_limits<int32_t>::max BOOST_PREVENT_MACRO_SUBSTITUTION (); }
210 explicit rand48(int32_t x0 = 1) : lcf(cnv(x0)) { }
211 explicit rand48(uint64_t x0) : lcf(x0) { }
212 template<class It> rand48(It& first, It last) : lcf(first, last) { }
213 // compiler-generated copy ctor and assignment operator are fine
214 void seed(int32_t x0 = 1) { lcf.seed(cnv(x0)); }
215 void seed(uint64_t x0) { lcf.seed(x0); }
216 template<class It> void seed(It& first, It last) { lcf.seed(first,last); }
218 int32_t operator()() { return static_cast<int32_t>(lcf() >> 17); }
219 // by experiment from lrand48()
220 static bool validation(int32_t x) { return x == 1993516219; }
222 #ifndef BOOST_NO_OPERATORS_IN_NAMESPACE
224 #ifndef BOOST_NO_MEMBER_TEMPLATE_FRIENDS
225 template<class CharT,class Traits>
226 friend std::basic_ostream<CharT,Traits>&
227 operator<<(std::basic_ostream<CharT,Traits>& os, const rand48& r)
228 { os << r.lcf; return os; }
230 template<class CharT,class Traits>
231 friend std::basic_istream<CharT,Traits>&
232 operator>>(std::basic_istream<CharT,Traits>& is, rand48& r)
233 { is >> r.lcf; return is; }
236 friend bool operator==(const rand48& x, const rand48& y)
237 { return x.lcf == y.lcf; }
238 friend bool operator!=(const rand48& x, const rand48& y)
239 { return !(x == y); }
241 // Use a member function; Streamable concept not supported.
242 bool operator==(const rand48& rhs) const
243 { return lcf == rhs.lcf; }
244 bool operator!=(const rand48& rhs) const
245 { return !(*this == rhs); }
248 random::linear_congruential<uint64_t,
249 uint64_t(0xDEECE66DUL) | (uint64_t(0x5) << 32), // xxxxULL is not portable
250 0xB, uint64_t(1)<<48, /* unknown */ 0> lcf;
251 static uint64_t cnv(int32_t x)
252 { return (static_cast<uint64_t>(x) << 16) | 0x330e; }
254 #endif /* !BOOST_NO_INT64_T && !BOOST_NO_INTEGRAL_INT64_T */
258 #endif // BOOST_RANDOM_LINEAR_CONGRUENTIAL_HPP