268 lines
9.6 KiB
Plaintext
268 lines
9.6 KiB
Plaintext
/* boost random/inversive_congruential.hpp header file
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*
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* Copyright Jens Maurer 2000-2001
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* Distributed under the Boost Software License, Version 1.0. (See
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* accompanying file LICENSE_1_0.txt or copy at
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* http://www.boost.org/LICENSE_1_0.txt)
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*
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* See http://www.boost.org for most recent version including documentation.
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*
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* $Id$
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*
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* Revision history
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* 2001-02-18 moved to individual header files
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*/
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#ifndef BOOST_RANDOM_INVERSIVE_CONGRUENTIAL_HPP
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#define BOOST_RANDOM_INVERSIVE_CONGRUENTIAL_HPP
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#include <iosfwd>
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#include <stdexcept>
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#include <boost/assert.hpp>
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#include <boost/config.hpp>
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#include <boost/cstdint.hpp>
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#include <boost/integer/static_log2.hpp>
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#include <boost/random/detail/config.hpp>
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#include <boost/random/detail/const_mod.hpp>
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#include <boost/random/detail/seed.hpp>
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#include <boost/random/detail/operators.hpp>
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#include <boost/random/detail/seed_impl.hpp>
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#include <boost/random/detail/disable_warnings.hpp>
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namespace boost {
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namespace random {
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// Eichenauer and Lehn 1986
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/**
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* Instantiations of class template @c inversive_congruential_engine model a
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* \pseudo_random_number_generator. It uses the inversive congruential
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* algorithm (ICG) described in
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*
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* @blockquote
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* "Inversive pseudorandom number generators: concepts, results and links",
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* Peter Hellekalek, In: "Proceedings of the 1995 Winter Simulation
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* Conference", C. Alexopoulos, K. Kang, W.R. Lilegdon, and D. Goldsman
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* (editors), 1995, pp. 255-262. ftp://random.mat.sbg.ac.at/pub/data/wsc95.ps
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* @endblockquote
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*
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* The output sequence is defined by x(n+1) = (a*inv(x(n)) - b) (mod p),
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* where x(0), a, b, and the prime number p are parameters of the generator.
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* The expression inv(k) denotes the multiplicative inverse of k in the
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* field of integer numbers modulo p, with inv(0) := 0.
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*
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* The template parameter IntType shall denote a signed integral type large
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* enough to hold p; a, b, and p are the parameters of the generators. The
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* template parameter val is the validation value checked by validation.
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*
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* @xmlnote
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* The implementation currently uses the Euclidian Algorithm to compute
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* the multiplicative inverse. Therefore, the inversive generators are about
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* 10-20 times slower than the others (see section"performance"). However,
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* the paper talks of only 3x slowdown, so the Euclidian Algorithm is probably
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* not optimal for calculating the multiplicative inverse.
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* @endxmlnote
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*/
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template<class IntType, IntType a, IntType b, IntType p>
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class inversive_congruential_engine
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{
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public:
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typedef IntType result_type;
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BOOST_STATIC_CONSTANT(bool, has_fixed_range = false);
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BOOST_STATIC_CONSTANT(result_type, multiplier = a);
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BOOST_STATIC_CONSTANT(result_type, increment = b);
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BOOST_STATIC_CONSTANT(result_type, modulus = p);
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BOOST_STATIC_CONSTANT(IntType, default_seed = 1);
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static result_type min BOOST_PREVENT_MACRO_SUBSTITUTION () { return b == 0 ? 1 : 0; }
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static result_type max BOOST_PREVENT_MACRO_SUBSTITUTION () { return p-1; }
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/**
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* Constructs an @c inversive_congruential_engine, seeding it with
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* the default seed.
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*/
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inversive_congruential_engine() { seed(); }
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/**
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* Constructs an @c inversive_congruential_engine, seeding it with @c x0.
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*/
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BOOST_RANDOM_DETAIL_ARITHMETIC_CONSTRUCTOR(inversive_congruential_engine,
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IntType, x0)
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{ seed(x0); }
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/**
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* Constructs an @c inversive_congruential_engine, seeding it with values
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* produced by a call to @c seq.generate().
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*/
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BOOST_RANDOM_DETAIL_SEED_SEQ_CONSTRUCTOR(inversive_congruential_engine,
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SeedSeq, seq)
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{ seed(seq); }
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/**
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* Constructs an @c inversive_congruential_engine, seeds it
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* with values taken from the itrator range [first, last),
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* and adjusts first to point to the element after the last one
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* used. If there are not enough elements, throws @c std::invalid_argument.
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*
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* first and last must be input iterators.
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*/
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template<class It> inversive_congruential_engine(It& first, It last)
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{ seed(first, last); }
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/**
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* Calls seed(default_seed)
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*/
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void seed() { seed(default_seed); }
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/**
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* If c mod m is zero and x0 mod m is zero, changes the current value of
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* the generator to 1. Otherwise, changes it to x0 mod m. If c is zero,
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* distinct seeds in the range [1,m) will leave the generator in distinct
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* states. If c is not zero, the range is [0,m).
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*/
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BOOST_RANDOM_DETAIL_ARITHMETIC_SEED(inversive_congruential_engine, IntType, x0)
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{
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// wrap _x if it doesn't fit in the destination
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if(modulus == 0) {
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_value = x0;
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} else {
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_value = x0 % modulus;
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}
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// handle negative seeds
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if(_value <= 0 && _value != 0) {
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_value += modulus;
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}
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// adjust to the correct range
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if(increment == 0 && _value == 0) {
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_value = 1;
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}
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BOOST_ASSERT(_value >= (min)());
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BOOST_ASSERT(_value <= (max)());
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}
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/**
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* Seeds an @c inversive_congruential_engine using values from a SeedSeq.
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*/
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BOOST_RANDOM_DETAIL_SEED_SEQ_SEED(inversive_congruential_engine, SeedSeq, seq)
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{ seed(detail::seed_one_int<IntType, modulus>(seq)); }
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/**
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* seeds an @c inversive_congruential_engine with values taken
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* from the itrator range [first, last) and adjusts @c first to
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* point to the element after the last one used. If there are
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* not enough elements, throws @c std::invalid_argument.
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*
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* @c first and @c last must be input iterators.
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*/
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template<class It> void seed(It& first, It last)
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{ seed(detail::get_one_int<IntType, modulus>(first, last)); }
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/** Returns the next output of the generator. */
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IntType operator()()
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{
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typedef const_mod<IntType, p> do_mod;
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_value = do_mod::mult_add(a, do_mod::invert(_value), b);
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return _value;
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}
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/** Fills a range with random values */
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template<class Iter>
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void generate(Iter first, Iter last)
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{ detail::generate_from_int(*this, first, last); }
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/** Advances the state of the generator by @c z. */
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void discard(boost::uintmax_t z)
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{
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for(boost::uintmax_t j = 0; j < z; ++j) {
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(*this)();
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}
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}
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/**
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* Writes the textual representation of the generator to a @c std::ostream.
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*/
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BOOST_RANDOM_DETAIL_OSTREAM_OPERATOR(os, inversive_congruential_engine, x)
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{
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os << x._value;
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return os;
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}
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/**
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* Reads the textual representation of the generator from a @c std::istream.
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*/
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BOOST_RANDOM_DETAIL_ISTREAM_OPERATOR(is, inversive_congruential_engine, x)
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{
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is >> x._value;
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return is;
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}
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/**
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* Returns true if the two generators will produce identical
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* sequences of outputs.
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*/
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BOOST_RANDOM_DETAIL_EQUALITY_OPERATOR(inversive_congruential_engine, x, y)
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{ return x._value == y._value; }
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/**
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* Returns true if the two generators will produce different
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* sequences of outputs.
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*/
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BOOST_RANDOM_DETAIL_INEQUALITY_OPERATOR(inversive_congruential_engine)
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private:
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IntType _value;
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};
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#ifndef BOOST_NO_INCLASS_MEMBER_INITIALIZATION
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// A definition is required even for integral static constants
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template<class IntType, IntType a, IntType b, IntType p>
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const bool inversive_congruential_engine<IntType, a, b, p>::has_fixed_range;
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template<class IntType, IntType a, IntType b, IntType p>
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const typename inversive_congruential_engine<IntType, a, b, p>::result_type inversive_congruential_engine<IntType, a, b, p>::multiplier;
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template<class IntType, IntType a, IntType b, IntType p>
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const typename inversive_congruential_engine<IntType, a, b, p>::result_type inversive_congruential_engine<IntType, a, b, p>::increment;
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template<class IntType, IntType a, IntType b, IntType p>
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const typename inversive_congruential_engine<IntType, a, b, p>::result_type inversive_congruential_engine<IntType, a, b, p>::modulus;
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template<class IntType, IntType a, IntType b, IntType p>
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const typename inversive_congruential_engine<IntType, a, b, p>::result_type inversive_congruential_engine<IntType, a, b, p>::default_seed;
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#endif
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/// \cond show_deprecated
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// provided for backwards compatibility
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template<class IntType, IntType a, IntType b, IntType p, IntType val = 0>
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class inversive_congruential : public inversive_congruential_engine<IntType, a, b, p>
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{
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typedef inversive_congruential_engine<IntType, a, b, p> base_type;
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public:
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inversive_congruential(IntType x0 = 1) : base_type(x0) {}
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template<class It>
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inversive_congruential(It& first, It last) : base_type(first, last) {}
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};
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/// \endcond
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/**
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* The specialization hellekalek1995 was suggested in
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*
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* @blockquote
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* "Inversive pseudorandom number generators: concepts, results and links",
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* Peter Hellekalek, In: "Proceedings of the 1995 Winter Simulation
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* Conference", C. Alexopoulos, K. Kang, W.R. Lilegdon, and D. Goldsman
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* (editors), 1995, pp. 255-262. ftp://random.mat.sbg.ac.at/pub/data/wsc95.ps
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* @endblockquote
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*/
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typedef inversive_congruential_engine<uint32_t, 9102, 2147483647-36884165,
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2147483647> hellekalek1995;
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} // namespace random
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using random::hellekalek1995;
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} // namespace boost
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#include <boost/random/detail/enable_warnings.hpp>
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#endif // BOOST_RANDOM_INVERSIVE_CONGRUENTIAL_HPP
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