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

Revision 857, 5.1 KB checked in by igarcia, 19 years ago (diff)
RevLine 
[857]1/* boost random/tausworthe.hpp header file
2 *
3 * Copyright Jens Maurer 2002
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_feedback_shift.hpp,v 1.12 2005/05/21 15:57:00 dgregor Exp $
11 *
12 */
13
14#ifndef BOOST_RANDOM_LINEAR_FEEDBACK_SHIFT_HPP
15#define BOOST_RANDOM_LINEAR_FEEDBACK_SHIFT_HPP
16
17#include <iostream>
18#include <cassert>
19#include <stdexcept>
20#include <boost/config.hpp>
21#include <boost/static_assert.hpp>
22#include <boost/limits.hpp>
23
24namespace boost {
25namespace random {
26
27// Tausworte 1965
28template<class UIntType, int w, int k, int q, int s, UIntType val>
29class linear_feedback_shift
30{
31public:
32  typedef UIntType result_type;
33  // avoid the warning trouble when using (1<<w) on 32 bit machines
34  BOOST_STATIC_CONSTANT(bool, has_fixed_range = false);
35  BOOST_STATIC_CONSTANT(int, word_size = w);
36  BOOST_STATIC_CONSTANT(int, exponent1 = k);
37  BOOST_STATIC_CONSTANT(int, exponent2 = q);
38  BOOST_STATIC_CONSTANT(int, step_size = s);
39
40  result_type min BOOST_PREVENT_MACRO_SUBSTITUTION () const { return 0; }
41  result_type max BOOST_PREVENT_MACRO_SUBSTITUTION () const { return wordmask; }
42
43  // MSVC 6 and possibly others crash when encountering complicated integral
44  // constant expressions.  Avoid the checks for now.
45  // BOOST_STATIC_ASSERT(w > 0);
46  // BOOST_STATIC_ASSERT(q > 0);
47  // BOOST_STATIC_ASSERT(k < w);
48  // BOOST_STATIC_ASSERT(0 < 2*q && 2*q < k);
49  // BOOST_STATIC_ASSERT(0 < s && s <= k-q);
50
51  explicit linear_feedback_shift(UIntType s0 = 341) : wordmask(0)
52  {
53    // MSVC fails BOOST_STATIC_ASSERT with std::numeric_limits at class scope
54#ifndef BOOST_NO_LIMITS_COMPILE_TIME_CONSTANTS
55    BOOST_STATIC_ASSERT(std::numeric_limits<UIntType>::is_integer);
56    BOOST_STATIC_ASSERT(!std::numeric_limits<UIntType>::is_signed);
57#endif
58
59    // avoid "left shift count >= with of type" warning
60    for(int i = 0; i < w; ++i)
61      wordmask |= (1u << i);
62    seed(s0);
63  }
64
65  template<class It> linear_feedback_shift(It& first, It last) : wordmask(0)
66  {
67    // MSVC fails BOOST_STATIC_ASSERT with std::numeric_limits at class scope
68#ifndef BOOST_NO_LIMITS_COMPILE_TIME_CONSTANTS
69    BOOST_STATIC_ASSERT(std::numeric_limits<UIntType>::is_integer);
70    BOOST_STATIC_ASSERT(!std::numeric_limits<UIntType>::is_signed);
71#endif
72
73    // avoid "left shift count >= with of type" warning
74    for(int i = 0; i < w; ++i)
75      wordmask |= (1u << i);
76    seed(first, last);
77  }
78
79  void seed(UIntType s0 = 341) { assert(s0 >= (1 << (w-k))); value = s0; }
80  template<class It> void seed(It& first, It last)
81  {
82    if(first == last)
83      throw std::invalid_argument("linear_feedback_shift::seed");
84    value = *first++;
85    assert(value >= (1 << (w-k)));
86  }
87
88  result_type operator()()
89  {
90    const UIntType b = (((value << q) ^ value) & wordmask) >> (k-s);
91    const UIntType mask = ( (~static_cast<UIntType>(0)) << (w-k) ) & wordmask;
92    value = ((value & mask) << s) ^ b;
93    return value;
94  }
95  bool validation(result_type x) const { return val == x; }
96
97#ifndef BOOST_NO_OPERATORS_IN_NAMESPACE
98
99#ifndef BOOST_NO_MEMBER_TEMPLATE_FRIENDS
100  template<class CharT, class Traits>
101  friend std::basic_ostream<CharT,Traits>&
102  operator<<(std::basic_ostream<CharT,Traits>& os, linear_feedback_shift x)
103  { os << x.value; return os; }
104
105  template<class CharT, class Traits>
106  friend std::basic_istream<CharT,Traits>&
107  operator>>(std::basic_istream<CharT,Traits>& is, linear_feedback_shift& x)
108  { is >> x.value; return is; }
109#endif
110
111  friend bool operator==(linear_feedback_shift x, linear_feedback_shift y)
112  { return x.value == y.value; }
113  friend bool operator!=(linear_feedback_shift x, linear_feedback_shift y)
114  { return !(x == y); }
115#else
116  // Use a member function; Streamable concept not supported.
117  bool operator==(linear_feedback_shift rhs) const
118  { return value == rhs.value; }
119  bool operator!=(linear_feedback_shift rhs) const
120  { return !(*this == rhs); }
121#endif
122
123private:
124  UIntType wordmask; // avoid "left shift count >= width of type" warnings
125  UIntType value;
126};
127
128#ifndef BOOST_NO_INCLASS_MEMBER_INITIALIZATION
129//  A definition is required even for integral static constants
130template<class UIntType, int w, int k, int q, int s, UIntType val>
131const bool linear_feedback_shift<UIntType, w, k, q, s, val>::has_fixed_range;
132template<class UIntType, int w, int k, int q, int s, UIntType val>
133const int linear_feedback_shift<UIntType, w, k, q, s, val>::word_size;
134template<class UIntType, int w, int k, int q, int s, UIntType val>
135const int linear_feedback_shift<UIntType, w, k, q, s, val>::exponent1;
136template<class UIntType, int w, int k, int q, int s, UIntType val>
137const int linear_feedback_shift<UIntType, w, k, q, s, val>::exponent2;
138template<class UIntType, int w, int k, int q, int s, UIntType val>
139const int linear_feedback_shift<UIntType, w, k, q, s, val>::step_size;
140#endif
141
142} // namespace random
143} // namespace boost
144
145#endif // BOOST_RANDOM_LINEAR_FEEDBACK_SHIFT_HPP
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