Chris@16: /* boost random/inversive_congruential.hpp header file
Chris@16:  *
Chris@16:  * Copyright Jens Maurer 2000-2001
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:  * Revision history
Chris@16:  *  2001-02-18  moved to individual header files
Chris@16:  */
Chris@16: 
Chris@16: #ifndef BOOST_RANDOM_INVERSIVE_CONGRUENTIAL_HPP
Chris@16: #define BOOST_RANDOM_INVERSIVE_CONGRUENTIAL_HPP
Chris@16: 
Chris@16: #include <iosfwd>
Chris@16: #include <stdexcept>
Chris@16: #include <boost/assert.hpp>
Chris@16: #include <boost/config.hpp>
Chris@16: #include <boost/cstdint.hpp>
Chris@16: #include <boost/integer/static_log2.hpp>
Chris@16: #include <boost/random/detail/config.hpp>
Chris@16: #include <boost/random/detail/const_mod.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: #include <boost/random/detail/disable_warnings.hpp>
Chris@16: 
Chris@16: namespace boost {
Chris@16: namespace random {
Chris@16: 
Chris@16: // Eichenauer and Lehn 1986
Chris@16: /**
Chris@16:  * Instantiations of class template @c inversive_congruential_engine model a
Chris@16:  * \pseudo_random_number_generator. It uses the inversive congruential
Chris@16:  * algorithm (ICG) described in
Chris@16:  *
Chris@16:  *  @blockquote
Chris@16:  *  "Inversive pseudorandom number generators: concepts, results and links",
Chris@16:  *  Peter Hellekalek, In: "Proceedings of the 1995 Winter Simulation
Chris@16:  *  Conference", C. Alexopoulos, K. Kang, W.R. Lilegdon, and D. Goldsman
Chris@16:  *  (editors), 1995, pp. 255-262. ftp://random.mat.sbg.ac.at/pub/data/wsc95.ps
Chris@16:  *  @endblockquote
Chris@16:  *
Chris@16:  * The output sequence is defined by x(n+1) = (a*inv(x(n)) - b) (mod p),
Chris@16:  * where x(0), a, b, and the prime number p are parameters of the generator.
Chris@16:  * The expression inv(k) denotes the multiplicative inverse of k in the
Chris@16:  * field of integer numbers modulo p, with inv(0) := 0.
Chris@16:  *
Chris@16:  * The template parameter IntType shall denote a signed integral type large
Chris@16:  * enough to hold p; a, b, and p are the parameters of the generators. The
Chris@16:  * template parameter val is the validation value checked by validation.
Chris@16:  *
Chris@16:  * @xmlnote
Chris@16:  * The implementation currently uses the Euclidian Algorithm to compute
Chris@16:  * the multiplicative inverse. Therefore, the inversive generators are about
Chris@16:  * 10-20 times slower than the others (see section"performance"). However,
Chris@16:  * the paper talks of only 3x slowdown, so the Euclidian Algorithm is probably
Chris@16:  * not optimal for calculating the multiplicative inverse.
Chris@16:  * @endxmlnote
Chris@16:  */
Chris@16: template<class IntType, IntType a, IntType b, IntType p>
Chris@16: class inversive_congruential_engine
Chris@16: {
Chris@16: public:
Chris@16:     typedef IntType result_type;
Chris@16:     BOOST_STATIC_CONSTANT(bool, has_fixed_range = false);
Chris@16: 
Chris@16:     BOOST_STATIC_CONSTANT(result_type, multiplier = a);
Chris@16:     BOOST_STATIC_CONSTANT(result_type, increment = b);
Chris@16:     BOOST_STATIC_CONSTANT(result_type, modulus = p);
Chris@16:     BOOST_STATIC_CONSTANT(IntType, default_seed = 1);
Chris@16: 
Chris@16:     static result_type min BOOST_PREVENT_MACRO_SUBSTITUTION () { return b == 0 ? 1 : 0; }
Chris@16:     static result_type max BOOST_PREVENT_MACRO_SUBSTITUTION () { return p-1; }
Chris@16:     
Chris@16:     /**
Chris@16:      * Constructs an @c inversive_congruential_engine, seeding it with
Chris@16:      * the default seed.
Chris@16:      */
Chris@16:     inversive_congruential_engine() { seed(); }
Chris@16: 
Chris@16:     /**
Chris@16:      * Constructs an @c inversive_congruential_engine, seeding it with @c x0.
Chris@16:      */
Chris@16:     BOOST_RANDOM_DETAIL_ARITHMETIC_CONSTRUCTOR(inversive_congruential_engine,
Chris@16:                                                IntType, x0)
Chris@16:     { seed(x0); }
Chris@16:     
Chris@16:     /**
Chris@16:      * Constructs an @c inversive_congruential_engine, seeding it with values
Chris@16:      * produced by a call to @c seq.generate().
Chris@16:      */
Chris@16:     BOOST_RANDOM_DETAIL_SEED_SEQ_CONSTRUCTOR(inversive_congruential_engine,
Chris@16:                                              SeedSeq, seq)
Chris@16:     { seed(seq); }
Chris@16:     
Chris@16:     /**
Chris@16:      * Constructs an @c inversive_congruential_engine, seeds it
Chris@16:      * with values taken from the itrator range [first, last),
Chris@16:      * and adjusts first to point to the element after the last one
Chris@16:      * used.  If there are not enough elements, throws @c std::invalid_argument.
Chris@16:      *
Chris@16:      * first and last must be input iterators.
Chris@16:      */
Chris@16:     template<class It> inversive_congruential_engine(It& first, It last)
Chris@16:     { seed(first, last); }
Chris@16: 
Chris@16:     /**
Chris@16:      * Calls seed(default_seed)
Chris@16:      */
Chris@16:     void seed() { seed(default_seed); }
Chris@16:   
Chris@16:     /**
Chris@16:      * If c mod m is zero and x0 mod m is zero, changes the current value of
Chris@16:      * the generator to 1. Otherwise, changes it to x0 mod m. If c is zero,
Chris@16:      * distinct seeds in the range [1,m) will leave the generator in distinct
Chris@16:      * states. If c is not zero, the range is [0,m).
Chris@16:      */
Chris@16:     BOOST_RANDOM_DETAIL_ARITHMETIC_SEED(inversive_congruential_engine, IntType, x0)
Chris@16:     {
Chris@16:         // wrap _x if it doesn't fit in the destination
Chris@16:         if(modulus == 0) {
Chris@16:             _value = x0;
Chris@16:         } else {
Chris@16:             _value = x0 % modulus;
Chris@16:         }
Chris@16:         // handle negative seeds
Chris@16:         if(_value <= 0 && _value != 0) {
Chris@16:             _value += modulus;
Chris@16:         }
Chris@16:         // adjust to the correct range
Chris@16:         if(increment == 0 && _value == 0) {
Chris@16:             _value = 1;
Chris@16:         }
Chris@16:         BOOST_ASSERT(_value >= (min)());
Chris@16:         BOOST_ASSERT(_value <= (max)());
Chris@16:     }
Chris@16: 
Chris@16:     /**
Chris@16:      * Seeds an @c inversive_congruential_engine using values from a SeedSeq.
Chris@16:      */
Chris@16:     BOOST_RANDOM_DETAIL_SEED_SEQ_SEED(inversive_congruential_engine, SeedSeq, seq)
Chris@16:     { seed(detail::seed_one_int<IntType, modulus>(seq)); }
Chris@16:     
Chris@16:     /**
Chris@16:      * seeds an @c inversive_congruential_engine with values taken
Chris@16:      * from the itrator range [first, last) and adjusts @c first to
Chris@16:      * point to the element after the last one used.  If there are
Chris@16:      * not enough elements, throws @c std::invalid_argument.
Chris@16:      *
Chris@16:      * @c first and @c last must be input iterators.
Chris@16:      */
Chris@16:     template<class It> void seed(It& first, It last)
Chris@16:     { seed(detail::get_one_int<IntType, modulus>(first, last)); }
Chris@16: 
Chris@16:     /** Returns the next output of the generator. */
Chris@16:     IntType operator()()
Chris@16:     {
Chris@16:         typedef const_mod<IntType, p> do_mod;
Chris@16:         _value = do_mod::mult_add(a, do_mod::invert(_value), 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, inversive_congruential_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, inversive_congruential_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(inversive_congruential_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(inversive_congruential_engine)
Chris@16: 
Chris@16: private:
Chris@16:     IntType _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 IntType, IntType a, IntType b, IntType p>
Chris@16: const bool inversive_congruential_engine<IntType, a, b, p>::has_fixed_range;
Chris@16: template<class IntType, IntType a, IntType b, IntType p>
Chris@16: const typename inversive_congruential_engine<IntType, a, b, p>::result_type inversive_congruential_engine<IntType, a, b, p>::multiplier;
Chris@16: template<class IntType, IntType a, IntType b, IntType p>
Chris@16: const typename inversive_congruential_engine<IntType, a, b, p>::result_type inversive_congruential_engine<IntType, a, b, p>::increment;
Chris@16: template<class IntType, IntType a, IntType b, IntType p>
Chris@16: const typename inversive_congruential_engine<IntType, a, b, p>::result_type inversive_congruential_engine<IntType, a, b, p>::modulus;
Chris@16: template<class IntType, IntType a, IntType b, IntType p>
Chris@16: const typename inversive_congruential_engine<IntType, a, b, p>::result_type inversive_congruential_engine<IntType, a, b, p>::default_seed;
Chris@16: #endif
Chris@16: 
Chris@16: /// \cond show_deprecated
Chris@16: 
Chris@16: // provided for backwards compatibility
Chris@16: template<class IntType, IntType a, IntType b, IntType p, IntType val = 0>
Chris@16: class inversive_congruential : public inversive_congruential_engine<IntType, a, b, p>
Chris@16: {
Chris@16:     typedef inversive_congruential_engine<IntType, a, b, p> base_type;
Chris@16: public:
Chris@16:     inversive_congruential(IntType x0 = 1) : base_type(x0) {}
Chris@16:     template<class It>
Chris@16:     inversive_congruential(It& first, It last) : base_type(first, last) {}
Chris@16: };
Chris@16: 
Chris@16: /// \endcond
Chris@16: 
Chris@16: /**
Chris@16:  * The specialization hellekalek1995 was suggested in
Chris@16:  *
Chris@16:  *  @blockquote
Chris@16:  *  "Inversive pseudorandom number generators: concepts, results and links",
Chris@16:  *  Peter Hellekalek, In: "Proceedings of the 1995 Winter Simulation
Chris@16:  *  Conference", C. Alexopoulos, K. Kang, W.R. Lilegdon, and D. Goldsman
Chris@16:  *  (editors), 1995, pp. 255-262. ftp://random.mat.sbg.ac.at/pub/data/wsc95.ps
Chris@16:  *  @endblockquote
Chris@16:  */
Chris@16: typedef inversive_congruential_engine<uint32_t, 9102, 2147483647-36884165,
Chris@16:   2147483647> hellekalek1995;
Chris@16: 
Chris@16: } // namespace random
Chris@16: 
Chris@16: using random::hellekalek1995;
Chris@16: 
Chris@16: } // namespace boost
Chris@16: 
Chris@16: #include <boost/random/detail/enable_warnings.hpp>
Chris@16: 
Chris@16: #endif // BOOST_RANDOM_INVERSIVE_CONGRUENTIAL_HPP