| /* boost random/tausworthe.hpp header file |
| * |
| * Copyright Jens Maurer 2002 |
| * Distributed under the Boost Software License, Version 1.0. (See |
| * accompanying file LICENSE_1_0.txt or copy at |
| * http://www.boost.org/LICENSE_1_0.txt) |
| * |
| * See http://www.boost.org for most recent version including documentation. |
| * |
| * $Id: linear_feedback_shift.hpp 60755 2010-03-22 00:45:06Z steven_watanabe $ |
| * |
| */ |
| |
| #ifndef BOOST_RANDOM_LINEAR_FEEDBACK_SHIFT_HPP |
| #define BOOST_RANDOM_LINEAR_FEEDBACK_SHIFT_HPP |
| |
| #include <iostream> |
| #include <cassert> |
| #include <stdexcept> |
| #include <boost/config.hpp> |
| #include <boost/static_assert.hpp> |
| #include <boost/limits.hpp> |
| #include <boost/random/detail/config.hpp> |
| |
| namespace boost { |
| namespace random { |
| |
| /** |
| * Instatiation of @c linear_feedback_shift model a |
| * \pseudo_random_number_generator. It was originally |
| * proposed in |
| * |
| * @blockquote |
| * "Random numbers generated by linear recurrence modulo two.", |
| * Tausworthe, R. C.(1965), Mathematics of Computation 19, 201-209. |
| * @endblockquote |
| */ |
| template<class UIntType, int w, int k, int q, int s, UIntType val> |
| class linear_feedback_shift |
| { |
| public: |
| typedef UIntType result_type; |
| // avoid the warning trouble when using (1<<w) on 32 bit machines |
| BOOST_STATIC_CONSTANT(bool, has_fixed_range = false); |
| BOOST_STATIC_CONSTANT(int, word_size = w); |
| BOOST_STATIC_CONSTANT(int, exponent1 = k); |
| BOOST_STATIC_CONSTANT(int, exponent2 = q); |
| BOOST_STATIC_CONSTANT(int, step_size = s); |
| |
| result_type min BOOST_PREVENT_MACRO_SUBSTITUTION () const { return 0; } |
| result_type max BOOST_PREVENT_MACRO_SUBSTITUTION () const { return wordmask; } |
| |
| // MSVC 6 and possibly others crash when encountering complicated integral |
| // constant expressions. Avoid the checks for now. |
| // BOOST_STATIC_ASSERT(w > 0); |
| // BOOST_STATIC_ASSERT(q > 0); |
| // BOOST_STATIC_ASSERT(k < w); |
| // BOOST_STATIC_ASSERT(0 < 2*q && 2*q < k); |
| // BOOST_STATIC_ASSERT(0 < s && s <= k-q); |
| |
| explicit linear_feedback_shift(UIntType s0 = 341) : wordmask(0) |
| { |
| // MSVC fails BOOST_STATIC_ASSERT with std::numeric_limits at class scope |
| #ifndef BOOST_NO_LIMITS_COMPILE_TIME_CONSTANTS |
| BOOST_STATIC_ASSERT(std::numeric_limits<UIntType>::is_integer); |
| BOOST_STATIC_ASSERT(!std::numeric_limits<UIntType>::is_signed); |
| #endif |
| |
| // avoid "left shift count >= with of type" warning |
| for(int i = 0; i < w; ++i) |
| wordmask |= (1u << i); |
| seed(s0); |
| } |
| |
| template<class It> linear_feedback_shift(It& first, It last) : wordmask(0) |
| { |
| // MSVC fails BOOST_STATIC_ASSERT with std::numeric_limits at class scope |
| #ifndef BOOST_NO_LIMITS_COMPILE_TIME_CONSTANTS |
| BOOST_STATIC_ASSERT(std::numeric_limits<UIntType>::is_integer); |
| BOOST_STATIC_ASSERT(!std::numeric_limits<UIntType>::is_signed); |
| #endif |
| |
| // avoid "left shift count >= with of type" warning |
| for(int i = 0; i < w; ++i) |
| wordmask |= (1u << i); |
| seed(first, last); |
| } |
| |
| void seed(UIntType s0 = 341) { |
| if(s0 < (1 << (w-k))) { |
| s0 += 1 << (w-k); |
| } |
| value = s0; |
| } |
| template<class It> void seed(It& first, It last) |
| { |
| if(first == last) |
| throw std::invalid_argument("linear_feedback_shift::seed"); |
| value = *first++; |
| assert(value >= (1 << (w-k))); |
| } |
| |
| result_type operator()() |
| { |
| const UIntType b = (((value << q) ^ value) & wordmask) >> (k-s); |
| const UIntType mask = ( (~static_cast<UIntType>(0)) << (w-k) ) & wordmask; |
| value = ((value & mask) << s) ^ b; |
| return value; |
| } |
| static bool validation(result_type x) { return val == x; } |
| |
| #ifndef BOOST_NO_OPERATORS_IN_NAMESPACE |
| |
| #ifndef BOOST_RANDOM_NO_STREAM_OPERATORS |
| template<class CharT, class Traits> |
| friend std::basic_ostream<CharT,Traits>& |
| operator<<(std::basic_ostream<CharT,Traits>& os, linear_feedback_shift x) |
| { os << x.value; return os; } |
| |
| template<class CharT, class Traits> |
| friend std::basic_istream<CharT,Traits>& |
| operator>>(std::basic_istream<CharT,Traits>& is, linear_feedback_shift& x) |
| { is >> x.value; return is; } |
| #endif |
| |
| friend bool operator==(linear_feedback_shift x, linear_feedback_shift y) |
| { return x.value == y.value; } |
| friend bool operator!=(linear_feedback_shift x, linear_feedback_shift y) |
| { return !(x == y); } |
| #else |
| // Use a member function; Streamable concept not supported. |
| bool operator==(linear_feedback_shift rhs) const |
| { return value == rhs.value; } |
| bool operator!=(linear_feedback_shift rhs) const |
| { return !(*this == rhs); } |
| #endif |
| |
| private: |
| UIntType wordmask; // avoid "left shift count >= width of type" warnings |
| UIntType value; |
| }; |
| |
| #ifndef BOOST_NO_INCLASS_MEMBER_INITIALIZATION |
| // A definition is required even for integral static constants |
| template<class UIntType, int w, int k, int q, int s, UIntType val> |
| const bool linear_feedback_shift<UIntType, w, k, q, s, val>::has_fixed_range; |
| template<class UIntType, int w, int k, int q, int s, UIntType val> |
| const int linear_feedback_shift<UIntType, w, k, q, s, val>::word_size; |
| template<class UIntType, int w, int k, int q, int s, UIntType val> |
| const int linear_feedback_shift<UIntType, w, k, q, s, val>::exponent1; |
| template<class UIntType, int w, int k, int q, int s, UIntType val> |
| const int linear_feedback_shift<UIntType, w, k, q, s, val>::exponent2; |
| template<class UIntType, int w, int k, int q, int s, UIntType val> |
| const int linear_feedback_shift<UIntType, w, k, q, s, val>::step_size; |
| #endif |
| |
| } // namespace random |
| } // namespace boost |
| |
| #endif // BOOST_RANDOM_LINEAR_FEEDBACK_SHIFT_HPP |