Chris@16: /* boost random/linear_feedback_shift.hpp header file
Chris@16:  *
Chris@16:  * Copyright Jens Maurer 2002
Chris@16:  * Copyright Steven Watanabe 2011
Chris@16:  * Distributed under the Boost Software License, Version 1.0. (See
Chris@16:  * accompanying file LICENSE_1_0.txt or copy at
Chris@16:  * http://www.boost.org/LICENSE_1_0.txt)
Chris@16:  *
Chris@16:  * See http://www.boost.org for most recent version including documentation.
Chris@16:  *
Chris@101:  * $Id$
Chris@16:  *
Chris@16:  */
Chris@16: 
Chris@16: #ifndef BOOST_RANDOM_LINEAR_FEEDBACK_SHIFT_HPP
Chris@16: #define BOOST_RANDOM_LINEAR_FEEDBACK_SHIFT_HPP
Chris@16: 
Chris@16: #include <iosfwd>
Chris@16: #include <stdexcept>
Chris@16: #include <boost/config.hpp>
Chris@16: #include <boost/cstdint.hpp>
Chris@16: #include <boost/static_assert.hpp>
Chris@16: #include <boost/integer/integer_mask.hpp>
Chris@16: #include <boost/random/detail/config.hpp>
Chris@16: #include <boost/random/detail/seed.hpp>
Chris@16: #include <boost/random/detail/operators.hpp>
Chris@16: #include <boost/random/detail/seed_impl.hpp>
Chris@16: 
Chris@16: namespace boost {
Chris@16: namespace random {
Chris@16: 
Chris@16: /**
Chris@16:  * Instatiations of @c linear_feedback_shift model a
Chris@16:  * \pseudo_random_number_generator.  It was originally
Chris@16:  * proposed in
Chris@16:  *
Chris@16:  *  @blockquote
Chris@16:  *  "Random numbers generated by linear recurrence modulo two.",
Chris@16:  *  Tausworthe, R. C.(1965), Mathematics of Computation 19, 201-209.
Chris@16:  *  @endblockquote
Chris@16:  */
Chris@16: template<class UIntType, int w, int k, int q, int s>
Chris@16: class linear_feedback_shift_engine
Chris@16: {
Chris@16: public:
Chris@16:     typedef UIntType result_type;
Chris@16:     BOOST_STATIC_CONSTANT(bool, has_fixed_range = false);
Chris@16:     BOOST_STATIC_CONSTANT(int, word_size = w);
Chris@16:     BOOST_STATIC_CONSTANT(int, exponent1 = k);
Chris@16:     BOOST_STATIC_CONSTANT(int, exponent2 = q);
Chris@16:     BOOST_STATIC_CONSTANT(int, step_size = s);
Chris@16:     BOOST_STATIC_CONSTANT(UIntType, default_seed = 341);
Chris@16: 
Chris@16:     /** Returns the smallest value that the generator can produce. */
Chris@16:     static result_type min BOOST_PREVENT_MACRO_SUBSTITUTION () { return 0; }
Chris@16:     /** Returns the largest value that the generator can produce. */
Chris@16:     static result_type max BOOST_PREVENT_MACRO_SUBSTITUTION ()
Chris@16:     { return wordmask(); }
Chris@16: 
Chris@16:     BOOST_STATIC_ASSERT(w > 0);
Chris@16:     BOOST_STATIC_ASSERT(q > 0);
Chris@16:     BOOST_STATIC_ASSERT(k < w);
Chris@16:     BOOST_STATIC_ASSERT(0 < 2*q && 2*q < k);
Chris@16:     BOOST_STATIC_ASSERT(0 < s && s <= k-q);
Chris@16: 
Chris@16:     /** Constructs a @c linear_feedback_shift_engine, using the default seed. */
Chris@16:     linear_feedback_shift_engine() { seed(); }
Chris@16:     
Chris@16:     /** Constructs a @c linear_feedback_shift_engine, seeding it with s0. */
Chris@16:     BOOST_RANDOM_DETAIL_ARITHMETIC_CONSTRUCTOR(linear_feedback_shift_engine,
Chris@16:         UIntType, s0)
Chris@16:     { seed(s0); }
Chris@16:     
Chris@16:     /** Constructs a @c linear_feedback_shift_engine, seeding it with seq. */
Chris@16:     BOOST_RANDOM_DETAIL_SEED_SEQ_CONSTRUCTOR(linear_feedback_shift_engine,
Chris@16:         SeedSeq, seq)
Chris@16:     { seed(seq); }
Chris@16:     
Chris@16:     /**
Chris@16:      * Constructs a @c linear_feedback_shift_engine, seeding it with 
Chris@16:      * values from the range [first, last).
Chris@16:      */
Chris@16:     template<class It> linear_feedback_shift_engine(It& first, It last)
Chris@16:     { seed(first, last); }
Chris@16:     
Chris@16:     /** Seeds a @c linear_feedback_shift_engine with the default seed. */
Chris@16:     void seed() {  seed(default_seed); }
Chris@16:     
Chris@16:     /** Seeds a @c linear_feedback_shift_engine with @c s0. */
Chris@16:     BOOST_RANDOM_DETAIL_ARITHMETIC_SEED(linear_feedback_shift_engine,
Chris@16:         UIntType, s0)
Chris@16:     {
Chris@16:         value = s0 & wordmask();
Chris@16:         if(value < (1 << (w-k))) {
Chris@16:             value += 1 << (w-k);
Chris@16:         }
Chris@16:     }
Chris@16:     
Chris@16:     /**
Chris@16:      * Seeds a @c linear_feedback_shift_engine with values
Chris@16:      * produced by @c seq.generate().
Chris@16:      */
Chris@16:     BOOST_RANDOM_DETAIL_SEED_SEQ_SEED(linear_feedback_shift_engine,
Chris@16:         SeedSeq, seq)
Chris@16:     { seed(detail::seed_one_int<UIntType, (UIntType(2) << (w - 1))>(seq)); }
Chris@16:     
Chris@16:     /**
Chris@16:      * Seeds a @c linear_feedback_shift_engine with values
Chris@16:      * from the range [first, last).
Chris@16:      */
Chris@16:     template<class It> void seed(It& first, It last)
Chris@16:     {
Chris@16:         seed(detail::get_one_int<UIntType, (UIntType(2) << (w - 1))>(first, last));
Chris@16:     }
Chris@16: 
Chris@16:     /** Returns the next value of the generator. */
Chris@16:     result_type operator()()
Chris@16:     {
Chris@16:         const UIntType b = (((value << q) ^ value) & wordmask()) >> (k-s);
Chris@16:         const UIntType mask = (wordmask() << (w-k)) & wordmask();
Chris@16:         value = ((value & mask) << s) ^ b;
Chris@16:         return value;
Chris@16:     }
Chris@16:   
Chris@16:     /** Fills a range with random values */
Chris@16:     template<class Iter>
Chris@16:     void generate(Iter first, Iter last)
Chris@16:     { detail::generate_from_int(*this, first, last); }
Chris@16: 
Chris@16:     /** Advances the state of the generator by @c z. */
Chris@16:     void discard(boost::uintmax_t z)
Chris@16:     {
Chris@16:         for(boost::uintmax_t j = 0; j < z; ++j) {
Chris@16:             (*this)();
Chris@16:         }
Chris@16:     }
Chris@16:     
Chris@16:     /**
Chris@16:      * Writes the textual representation of the generator to a @c std::ostream.
Chris@16:      */
Chris@16:     BOOST_RANDOM_DETAIL_OSTREAM_OPERATOR(os, linear_feedback_shift_engine, x)
Chris@16:     {
Chris@16:         os << x.value;
Chris@16:         return os;
Chris@16:     }
Chris@16:     
Chris@16:     /**
Chris@16:      * Reads the textual representation of the generator from a @c std::istream.
Chris@16:      */
Chris@16:     BOOST_RANDOM_DETAIL_ISTREAM_OPERATOR(is, linear_feedback_shift_engine, x)
Chris@16:     {
Chris@16:         is >> x.value;
Chris@16:         return is;
Chris@16:     }
Chris@16: 
Chris@16:     /**
Chris@16:      * Returns true if the two generators will produce identical
Chris@16:      * sequences of outputs.
Chris@16:      */
Chris@16:     BOOST_RANDOM_DETAIL_EQUALITY_OPERATOR(linear_feedback_shift_engine, x, y)
Chris@16:     { return x.value == y.value; }
Chris@16:     
Chris@16:     /**
Chris@16:      * Returns true if the two generators will produce different
Chris@16:      * sequences of outputs.
Chris@16:      */
Chris@16:     BOOST_RANDOM_DETAIL_INEQUALITY_OPERATOR(linear_feedback_shift_engine)
Chris@16: 
Chris@16: private:
Chris@16:     /// \cond show_private
Chris@16:     static UIntType wordmask() { return boost::low_bits_mask_t<w>::sig_bits; }
Chris@16:     /// \endcond
Chris@16:     UIntType value;
Chris@16: };
Chris@16: 
Chris@16: #ifndef BOOST_NO_INCLASS_MEMBER_INITIALIZATION
Chris@16: //  A definition is required even for integral static constants
Chris@16: template<class UIntType, int w, int k, int q, int s>
Chris@16: const bool linear_feedback_shift_engine<UIntType, w, k, q, s>::has_fixed_range;
Chris@16: template<class UIntType, int w, int k, int q, int s>
Chris@16: const int linear_feedback_shift_engine<UIntType, w, k, q, s>::word_size;
Chris@16: template<class UIntType, int w, int k, int q, int s>
Chris@16: const int linear_feedback_shift_engine<UIntType, w, k, q, s>::exponent1;
Chris@16: template<class UIntType, int w, int k, int q, int s>
Chris@16: const int linear_feedback_shift_engine<UIntType, w, k, q, s>::exponent2;
Chris@16: template<class UIntType, int w, int k, int q, int s>
Chris@16: const int linear_feedback_shift_engine<UIntType, w, k, q, s>::step_size;
Chris@16: template<class UIntType, int w, int k, int q, int s>
Chris@16: const UIntType linear_feedback_shift_engine<UIntType, w, k, q, s>::default_seed;
Chris@16: #endif
Chris@16: 
Chris@16: /// \cond show_deprecated
Chris@16: 
Chris@16: /** Provided for backwards compatibility. */
Chris@16: template<class UIntType, int w, int k, int q, int s, UIntType v = 0>
Chris@16: class linear_feedback_shift :
Chris@16:     public linear_feedback_shift_engine<UIntType, w, k, q, s>
Chris@16: {
Chris@16:     typedef linear_feedback_shift_engine<UIntType, w, k, q, s> base_type;
Chris@16: public:
Chris@16:     linear_feedback_shift() {}
Chris@16:     BOOST_RANDOM_DETAIL_SEED_SEQ_CONSTRUCTOR(linear_feedback_shift,
Chris@16:         SeedSeq, seq)
Chris@16:     { seed(seq); }
Chris@16:     BOOST_RANDOM_DETAIL_ARITHMETIC_CONSTRUCTOR(linear_feedback_shift,
Chris@16:         UIntType, val)
Chris@16:     { seed(val); }
Chris@16:     template<class It>
Chris@16:     linear_feedback_shift(It& first, It last) : base_type(first, last) {}
Chris@16: };
Chris@16: 
Chris@16: /// \endcond
Chris@16: 
Chris@16: } // namespace random
Chris@16: } // namespace boost
Chris@16: 
Chris@16: #endif // BOOST_RANDOM_LINEAR_FEEDBACK_SHIFT_HPP