boost/random/linear_feedback_shift.hpp
/* 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 29116 2005-05-21 15:57:01Z dgregor $
*
*/
#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>
namespace boost {
namespace random {
// Tausworte 1965
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) { assert(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;
}
bool validation(result_type x) const { return val == x; }
#ifndef BOOST_NO_OPERATORS_IN_NAMESPACE
#ifndef BOOST_NO_MEMBER_TEMPLATE_FRIENDS
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