| /* boost random/inversive_congruential.hpp header file |
| * |
| * Copyright Jens Maurer 2000-2001 |
| * 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: inversive_congruential.hpp 60755 2010-03-22 00:45:06Z steven_watanabe $ |
| * |
| * Revision history |
| * 2001-02-18 moved to individual header files |
| */ |
| |
| #ifndef BOOST_RANDOM_INVERSIVE_CONGRUENTIAL_HPP |
| #define BOOST_RANDOM_INVERSIVE_CONGRUENTIAL_HPP |
| |
| #include <iostream> |
| #include <cassert> |
| #include <stdexcept> |
| #include <boost/config.hpp> |
| #include <boost/static_assert.hpp> |
| #include <boost/random/detail/config.hpp> |
| #include <boost/random/detail/const_mod.hpp> |
| |
| namespace boost { |
| namespace random { |
| |
| // Eichenauer and Lehn 1986 |
| /** |
| * Instantiations of class template @c inversive_congruential model a |
| * \pseudo_random_number_generator. It uses the inversive congruential |
| * algorithm (ICG) described in |
| * |
| * @blockquote |
| * "Inversive pseudorandom number generators: concepts, results and links", |
| * Peter Hellekalek, In: "Proceedings of the 1995 Winter Simulation |
| * Conference", C. Alexopoulos, K. Kang, W.R. Lilegdon, and D. Goldsman |
| * (editors), 1995, pp. 255-262. ftp://random.mat.sbg.ac.at/pub/data/wsc95.ps |
| * @endblockquote |
| * |
| * The output sequence is defined by x(n+1) = (a*inv(x(n)) - b) (mod p), |
| * where x(0), a, b, and the prime number p are parameters of the generator. |
| * The expression inv(k) denotes the multiplicative inverse of k in the |
| * field of integer numbers modulo p, with inv(0) := 0. |
| * |
| * The template parameter IntType shall denote a signed integral type large |
| * enough to hold p; a, b, and p are the parameters of the generators. The |
| * template parameter val is the validation value checked by validation. |
| * |
| * @xmlnote |
| * The implementation currently uses the Euclidian Algorithm to compute |
| * the multiplicative inverse. Therefore, the inversive generators are about |
| * 10-20 times slower than the others (see section"performance"). However, |
| * the paper talks of only 3x slowdown, so the Euclidian Algorithm is probably |
| * not optimal for calculating the multiplicative inverse. |
| * @endxmlnote |
| */ |
| template<class IntType, IntType a, IntType b, IntType p, IntType val> |
| class inversive_congruential |
| { |
| public: |
| typedef IntType result_type; |
| #ifndef BOOST_NO_INCLASS_MEMBER_INITIALIZATION |
| static const bool has_fixed_range = true; |
| static const result_type min_value = (b == 0 ? 1 : 0); |
| static const result_type max_value = p-1; |
| #else |
| BOOST_STATIC_CONSTANT(bool, has_fixed_range = false); |
| #endif |
| BOOST_STATIC_CONSTANT(result_type, multiplier = a); |
| BOOST_STATIC_CONSTANT(result_type, increment = b); |
| BOOST_STATIC_CONSTANT(result_type, modulus = p); |
| |
| result_type min BOOST_PREVENT_MACRO_SUBSTITUTION () const { return b == 0 ? 1 : 0; } |
| result_type max BOOST_PREVENT_MACRO_SUBSTITUTION () const { return p-1; } |
| |
| /** |
| * Constructs an inversive_congruential generator with |
| * @c y0 as the initial state. |
| */ |
| explicit inversive_congruential(IntType y0 = 1) : value(y0) |
| { |
| BOOST_STATIC_ASSERT(b >= 0); |
| BOOST_STATIC_ASSERT(p > 1); |
| BOOST_STATIC_ASSERT(a >= 1); |
| if(b == 0) |
| assert(y0 > 0); |
| } |
| template<class It> inversive_congruential(It& first, It last) |
| { seed(first, last); } |
| |
| /** Changes the current state to y0. */ |
| void seed(IntType y0 = 1) { value = y0; if(b == 0) assert(y0 > 0); } |
| template<class It> void seed(It& first, It last) |
| { |
| if(first == last) |
| throw std::invalid_argument("inversive_congruential::seed"); |
| value = *first++; |
| } |
| IntType operator()() |
| { |
| typedef const_mod<IntType, p> do_mod; |
| value = do_mod::mult_add(a, do_mod::invert(value), b); |
| return value; |
| } |
| |
| static bool validation(result_type x) { return val == x; } |
| |
| #ifndef BOOST_NO_OPERATORS_IN_NAMESPACE |
| |
| #ifndef BOOST_RANDOM_NO_STREAM_OPERATORS |
| template<class CharT, class Traits> |
| friend std::basic_ostream<CharT,Traits>& |
| operator<<(std::basic_ostream<CharT,Traits>& os, inversive_congruential x) |
| { os << x.value; return os; } |
| |
| template<class CharT, class Traits> |
| friend std::basic_istream<CharT,Traits>& |
| operator>>(std::basic_istream<CharT,Traits>& is, inversive_congruential& x) |
| { is >> x.value; return is; } |
| #endif |
| |
| friend bool operator==(inversive_congruential x, inversive_congruential y) |
| { return x.value == y.value; } |
| friend bool operator!=(inversive_congruential x, inversive_congruential y) |
| { return !(x == y); } |
| #else |
| // Use a member function; Streamable concept not supported. |
| bool operator==(inversive_congruential rhs) const |
| { return value == rhs.value; } |
| bool operator!=(inversive_congruential rhs) const |
| { return !(*this == rhs); } |
| #endif |
| private: |
| IntType value; |
| }; |
| |
| #ifndef BOOST_NO_INCLASS_MEMBER_INITIALIZATION |
| // A definition is required even for integral static constants |
| template<class IntType, IntType a, IntType b, IntType p, IntType val> |
| const bool inversive_congruential<IntType, a, b, p, val>::has_fixed_range; |
| template<class IntType, IntType a, IntType b, IntType p, IntType val> |
| const typename inversive_congruential<IntType, a, b, p, val>::result_type inversive_congruential<IntType, a, b, p, val>::min_value; |
| template<class IntType, IntType a, IntType b, IntType p, IntType val> |
| const typename inversive_congruential<IntType, a, b, p, val>::result_type inversive_congruential<IntType, a, b, p, val>::max_value; |
| template<class IntType, IntType a, IntType b, IntType p, IntType val> |
| const typename inversive_congruential<IntType, a, b, p, val>::result_type inversive_congruential<IntType, a, b, p, val>::multiplier; |
| template<class IntType, IntType a, IntType b, IntType p, IntType val> |
| const typename inversive_congruential<IntType, a, b, p, val>::result_type inversive_congruential<IntType, a, b, p, val>::increment; |
| template<class IntType, IntType a, IntType b, IntType p, IntType val> |
| const typename inversive_congruential<IntType, a, b, p, val>::result_type inversive_congruential<IntType, a, b, p, val>::modulus; |
| #endif |
| |
| } // namespace random |
| |
| /** |
| * The specialization hellekalek1995 was suggested in |
| * |
| * @blockquote |
| * "Inversive pseudorandom number generators: concepts, results and links", |
| * Peter Hellekalek, In: "Proceedings of the 1995 Winter Simulation |
| * Conference", C. Alexopoulos, K. Kang, W.R. Lilegdon, and D. Goldsman |
| * (editors), 1995, pp. 255-262. ftp://random.mat.sbg.ac.at/pub/data/wsc95.ps |
| * @endblockquote |
| */ |
| typedef random::inversive_congruential<int32_t, 9102, 2147483647-36884165, |
| 2147483647, 0> hellekalek1995; |
| |
| } // namespace boost |
| |
| #endif // BOOST_RANDOM_INVERSIVE_CONGRUENTIAL_HPP |