source: NonGTP/Boost/boost/random/linear_congruential.hpp @ 857

Revision 857, 9.0 KB checked in by igarcia, 19 years ago (diff)
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1/* boost random/linear_congruential.hpp header file
2 *
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)
7 *
8 * See http://www.boost.org for most recent version including documentation.
9 *
10 * $Id: linear_congruential.hpp,v 1.22 2005/05/21 15:57:00 dgregor Exp $
11 *
12 * Revision history
13 *  2001-02-18  moved to individual header files
14 */
15
16#ifndef BOOST_RANDOM_LINEAR_CONGRUENTIAL_HPP
17#define BOOST_RANDOM_LINEAR_CONGRUENTIAL_HPP
18
19#include <iostream>
20#include <cassert>
21#include <stdexcept>
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>
27
28namespace boost {
29namespace random {
30
31// compile-time configurable linear congruential generator
32template<class IntType, IntType a, IntType c, IntType m, IntType val>
33class linear_congruential
34{
35public:
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;
41#else
42  BOOST_STATIC_CONSTANT(bool, has_fixed_range = false);
43#endif
44  BOOST_STATIC_CONSTANT(IntType, multiplier = a);
45  BOOST_STATIC_CONSTANT(IntType, increment = c);
46  BOOST_STATIC_CONSTANT(IntType, modulus = m);
47
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);
52
53  explicit linear_congruential(IntType x0 = 1)
54    : _modulus(modulus), _x(_modulus ? (x0 % _modulus) : x0)
55  {
56    assert(c || x0); /* if c == 0 and x(0) == 0 then x(n) = 0 for all n */
57    // overflow check
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));
60
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);
64#endif
65  }
66
67  template<class It>
68  linear_congruential(It& first, It last) { seed(first, last); }
69
70  // compiler-generated copy constructor and assignment operator are fine
71  void seed(IntType x0 = 1)
72  {
73    assert(c || x0);
74    _x = (_modulus ? (x0 % _modulus) : x0);
75  }
76
77  template<class It>
78  void seed(It& first, It last)
79  {
80    if(first == last)
81      throw std::invalid_argument("linear_congruential::seed");
82    IntType value = *first++;
83    _x = (_modulus ? (value % _modulus) : value);
84  }
85
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; }
88
89  IntType operator()()
90  {
91    _x = const_mod<IntType, m>::mult_add(a, _x, c);
92    return _x;
93  }
94
95  static bool validation(IntType x) { return val == x; }
96
97#ifdef BOOST_NO_OPERATORS_IN_NAMESPACE
98   
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); }
104
105#else
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); }
112   
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)
118  {
119    return os << lcg._x;
120  }
121
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)
126  {
127    return is >> lcg._x;
128  }
129 
130private:
131#endif
132#endif
133   
134  IntType _modulus;   // work-around for gcc "divide by zero" warning in ctor
135  IntType _x;
136};
137
138// probably needs the "no native streams" caveat for STLPort
139#if !defined(__SGI_STL_PORT) && BOOST_WORKAROUND(__GNUC__, == 2)
140template<class IntType, IntType a, IntType c, IntType m, IntType val>
141std::ostream&
142operator<<(std::ostream& os,
143           const linear_congruential<IntType,a,c,m,val>& lcg)
144{
145    return os << lcg._x;
146}
147
148template<class IntType, IntType a, IntType c, IntType m, IntType val>
149std::istream&
150operator>>(std::istream& is,
151           linear_congruential<IntType,a,c,m,val>& lcg)
152{
153    return is >> lcg._x;
154}
155#elif defined(BOOST_NO_OPERATORS_IN_NAMESPACE) || defined(BOOST_NO_MEMBER_TEMPLATE_FRIENDS) || BOOST_WORKAROUND(__BORLANDC__, BOOST_TESTED_AT(0x551))
156template<class CharT, class Traits, class IntType, IntType a, IntType c, IntType m, IntType val>
157std::basic_ostream<CharT,Traits>&
158operator<<(std::basic_ostream<CharT,Traits>& os,
159           const linear_congruential<IntType,a,c,m,val>& lcg)
160{
161    return os << lcg._x;
162}
163
164template<class CharT, class Traits, class IntType, IntType a, IntType c, IntType m, IntType val>
165std::basic_istream<CharT,Traits>&
166operator>>(std::basic_istream<CharT,Traits>& is,
167           linear_congruential<IntType,a,c,m,val>& lcg)
168{
169    return is >> lcg._x;
170}
171#endif
172
173#ifndef BOOST_NO_INCLASS_MEMBER_INITIALIZATION
174//  A definition is required even for integral static constants
175template<class IntType, IntType a, IntType c, IntType m, IntType val>
176const bool linear_congruential<IntType, a, c, m, val>::has_fixed_range;
177template<class IntType, IntType a, IntType c, IntType m, IntType val>
178const typename linear_congruential<IntType, a, c, m, val>::result_type linear_congruential<IntType, a, c, m, val>::min_value;
179template<class IntType, IntType a, IntType c, IntType m, IntType val>
180const typename linear_congruential<IntType, a, c, m, val>::result_type linear_congruential<IntType, a, c, m, val>::max_value;
181template<class IntType, IntType a, IntType c, IntType m, IntType val>
182const IntType linear_congruential<IntType,a,c,m,val>::modulus;
183#endif
184
185} // namespace random
186
187// validation values from the publications
188typedef random::linear_congruential<int32_t, 16807, 0, 2147483647,
189  1043618065> minstd_rand0;
190typedef random::linear_congruential<int32_t, 48271, 0, 2147483647,
191  399268537> minstd_rand;
192
193
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
196class rand48
197{
198public:
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;
204#else
205  enum { has_fixed_range = false };
206#endif
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 (); }
209 
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); }
217
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; }
221
222#ifndef BOOST_NO_OPERATORS_IN_NAMESPACE
223
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; }
229
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; }
234#endif
235
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); }
240#else
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); }
246#endif
247private:
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;  }
253};
254#endif /* !BOOST_NO_INT64_T && !BOOST_NO_INTEGRAL_INT64_T */
255
256} // namespace boost
257
258#endif // BOOST_RANDOM_LINEAR_CONGRUENTIAL_HPP
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