/* 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 |