williamr@2: /* boost random/tausworthe.hpp header file
williamr@2:  *
williamr@2:  * Copyright Jens Maurer 2002
williamr@2:  * Distributed under the Boost Software License, Version 1.0. (See
williamr@2:  * accompanying file LICENSE_1_0.txt or copy at
williamr@2:  * http://www.boost.org/LICENSE_1_0.txt)
williamr@2:  *
williamr@2:  * See http://www.boost.org for most recent version including documentation.
williamr@2:  *
williamr@2:  * $Id: linear_feedback_shift.hpp,v 1.12 2005/05/21 15:57:00 dgregor Exp $
williamr@2:  *
williamr@2:  */
williamr@2: 
williamr@2: #ifndef BOOST_RANDOM_LINEAR_FEEDBACK_SHIFT_HPP
williamr@2: #define BOOST_RANDOM_LINEAR_FEEDBACK_SHIFT_HPP
williamr@2: 
williamr@2: #include <iostream>
williamr@2: #include <cassert>
williamr@2: #include <stdexcept>
williamr@2: #include <boost/config.hpp>
williamr@2: #include <boost/static_assert.hpp>
williamr@2: #include <boost/limits.hpp>
williamr@2: 
williamr@2: namespace boost {
williamr@2: namespace random {
williamr@2: 
williamr@2: // Tausworte 1965
williamr@2: template<class UIntType, int w, int k, int q, int s, UIntType val>
williamr@2: class linear_feedback_shift
williamr@2: {
williamr@2: public:
williamr@2:   typedef UIntType result_type;
williamr@2:   // avoid the warning trouble when using (1<<w) on 32 bit machines
williamr@2:   BOOST_STATIC_CONSTANT(bool, has_fixed_range = false);
williamr@2:   BOOST_STATIC_CONSTANT(int, word_size = w);
williamr@2:   BOOST_STATIC_CONSTANT(int, exponent1 = k);
williamr@2:   BOOST_STATIC_CONSTANT(int, exponent2 = q);
williamr@2:   BOOST_STATIC_CONSTANT(int, step_size = s);
williamr@2: 
williamr@2:   result_type min BOOST_PREVENT_MACRO_SUBSTITUTION () const { return 0; }
williamr@2:   result_type max BOOST_PREVENT_MACRO_SUBSTITUTION () const { return wordmask; }
williamr@2: 
williamr@2:   // MSVC 6 and possibly others crash when encountering complicated integral
williamr@2:   // constant expressions.  Avoid the checks for now.
williamr@2:   // BOOST_STATIC_ASSERT(w > 0);
williamr@2:   // BOOST_STATIC_ASSERT(q > 0);
williamr@2:   // BOOST_STATIC_ASSERT(k < w);
williamr@2:   // BOOST_STATIC_ASSERT(0 < 2*q && 2*q < k);
williamr@2:   // BOOST_STATIC_ASSERT(0 < s && s <= k-q);
williamr@2: 
williamr@2:   explicit linear_feedback_shift(UIntType s0 = 341) : wordmask(0)
williamr@2:   {
williamr@2:     // MSVC fails BOOST_STATIC_ASSERT with std::numeric_limits at class scope
williamr@2: #ifndef BOOST_NO_LIMITS_COMPILE_TIME_CONSTANTS
williamr@2:     BOOST_STATIC_ASSERT(std::numeric_limits<UIntType>::is_integer);
williamr@2:     BOOST_STATIC_ASSERT(!std::numeric_limits<UIntType>::is_signed);
williamr@2: #endif
williamr@2: 
williamr@2:     // avoid "left shift count >= with of type" warning
williamr@2:     for(int i = 0; i < w; ++i)
williamr@2:       wordmask |= (1u << i);
williamr@2:     seed(s0);
williamr@2:   }
williamr@2: 
williamr@2:   template<class It> linear_feedback_shift(It& first, It last) : wordmask(0)
williamr@2:   {
williamr@2:     // MSVC fails BOOST_STATIC_ASSERT with std::numeric_limits at class scope
williamr@2: #ifndef BOOST_NO_LIMITS_COMPILE_TIME_CONSTANTS
williamr@2:     BOOST_STATIC_ASSERT(std::numeric_limits<UIntType>::is_integer);
williamr@2:     BOOST_STATIC_ASSERT(!std::numeric_limits<UIntType>::is_signed);
williamr@2: #endif
williamr@2: 
williamr@2:     // avoid "left shift count >= with of type" warning
williamr@2:     for(int i = 0; i < w; ++i)
williamr@2:       wordmask |= (1u << i);
williamr@2:     seed(first, last);
williamr@2:   }
williamr@2: 
williamr@2:   void seed(UIntType s0 = 341) { assert(s0 >= (1 << (w-k))); value = s0; }
williamr@2:   template<class It> void seed(It& first, It last)
williamr@2:   {
williamr@2:     if(first == last)
williamr@2:       throw std::invalid_argument("linear_feedback_shift::seed");
williamr@2:     value = *first++;
williamr@2:     assert(value >= (1 << (w-k)));
williamr@2:   }
williamr@2: 
williamr@2:   result_type operator()()
williamr@2:   {
williamr@2:     const UIntType b = (((value << q) ^ value) & wordmask) >> (k-s);
williamr@2:     const UIntType mask = ( (~static_cast<UIntType>(0)) << (w-k) ) & wordmask;
williamr@2:     value = ((value & mask) << s) ^ b;
williamr@2:     return value;
williamr@2:   }
williamr@2:   bool validation(result_type x) const { return val == x; }
williamr@2: 
williamr@2: #ifndef BOOST_NO_OPERATORS_IN_NAMESPACE
williamr@2: 
williamr@2: #ifndef BOOST_NO_MEMBER_TEMPLATE_FRIENDS
williamr@2:   template<class CharT, class Traits>
williamr@2:   friend std::basic_ostream<CharT,Traits>&
williamr@2:   operator<<(std::basic_ostream<CharT,Traits>& os, linear_feedback_shift x)
williamr@2:   { os << x.value; return os; }
williamr@2: 
williamr@2:   template<class CharT, class Traits>
williamr@2:   friend std::basic_istream<CharT,Traits>&
williamr@2:   operator>>(std::basic_istream<CharT,Traits>& is, linear_feedback_shift& x)
williamr@2:   { is >> x.value; return is; }
williamr@2: #endif
williamr@2: 
williamr@2:   friend bool operator==(linear_feedback_shift x, linear_feedback_shift y)
williamr@2:   { return x.value == y.value; }
williamr@2:   friend bool operator!=(linear_feedback_shift x, linear_feedback_shift y)
williamr@2:   { return !(x == y); }
williamr@2: #else
williamr@2:   // Use a member function; Streamable concept not supported.
williamr@2:   bool operator==(linear_feedback_shift rhs) const
williamr@2:   { return value == rhs.value; }
williamr@2:   bool operator!=(linear_feedback_shift rhs) const
williamr@2:   { return !(*this == rhs); }
williamr@2: #endif
williamr@2: 
williamr@2: private:
williamr@2:   UIntType wordmask; // avoid "left shift count >= width of type" warnings
williamr@2:   UIntType value;
williamr@2: };
williamr@2: 
williamr@2: #ifndef BOOST_NO_INCLASS_MEMBER_INITIALIZATION
williamr@2: //  A definition is required even for integral static constants
williamr@2: template<class UIntType, int w, int k, int q, int s, UIntType val>
williamr@2: const bool linear_feedback_shift<UIntType, w, k, q, s, val>::has_fixed_range;
williamr@2: template<class UIntType, int w, int k, int q, int s, UIntType val>
williamr@2: const int linear_feedback_shift<UIntType, w, k, q, s, val>::word_size;
williamr@2: template<class UIntType, int w, int k, int q, int s, UIntType val>
williamr@2: const int linear_feedback_shift<UIntType, w, k, q, s, val>::exponent1;
williamr@2: template<class UIntType, int w, int k, int q, int s, UIntType val>
williamr@2: const int linear_feedback_shift<UIntType, w, k, q, s, val>::exponent2;
williamr@2: template<class UIntType, int w, int k, int q, int s, UIntType val>
williamr@2: const int linear_feedback_shift<UIntType, w, k, q, s, val>::step_size;
williamr@2: #endif
williamr@2: 
williamr@2: } // namespace random
williamr@2: } // namespace boost
williamr@2: 
williamr@2: #endif // BOOST_RANDOM_LINEAR_FEEDBACK_SHIFT_HPP