404 lines
13 KiB
C++
404 lines
13 KiB
C++
/* boost random/linear_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: linear_congruential.hpp 60755 2010-03-22 00:45:06Z steven_watanabe $
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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_LINEAR_CONGRUENTIAL_HPP
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#define BOOST_RANDOM_LINEAR_CONGRUENTIAL_HPP
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#include <iostream>
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#include <cassert>
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#include <stdexcept>
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#include <boost/config.hpp>
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#include <boost/limits.hpp>
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#include <boost/static_assert.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/detail/workaround.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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/**
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* Instantiations of class template linear_congruential model a
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* \pseudo_random_number_generator. Linear congruential pseudo-random
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* number generators are described in:
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*
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* "Mathematical methods in large-scale computing units", D. H. Lehmer,
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* Proc. 2nd Symposium on Large-Scale Digital Calculating Machines,
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* Harvard University Press, 1951, pp. 141-146
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*
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* Let x(n) denote the sequence of numbers returned by some pseudo-random
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* number generator. Then for the linear congruential generator,
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* x(n+1) := (a * x(n) + c) mod m. Parameters for the generator are
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* x(0), a, c, m. The template parameter IntType shall denote an integral
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* type. It must be large enough to hold values a, c, and m. The template
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* parameters a and c must be smaller than m.
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*
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* Note: The quality of the generator crucially depends on the choice of
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* the parameters. User code should use one of the sensibly parameterized
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* generators such as minstd_rand instead.
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*/
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template<class IntType, IntType a, IntType c, IntType m, IntType val>
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class linear_congruential
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{
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public:
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typedef IntType result_type;
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#ifndef BOOST_NO_INCLASS_MEMBER_INITIALIZATION
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static const bool has_fixed_range = true;
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static const result_type min_value = ( c == 0 ? 1 : 0 );
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static const result_type max_value = m-1;
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#else
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BOOST_STATIC_CONSTANT(bool, has_fixed_range = false);
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#endif
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BOOST_STATIC_CONSTANT(IntType, multiplier = a);
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BOOST_STATIC_CONSTANT(IntType, increment = c);
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BOOST_STATIC_CONSTANT(IntType, modulus = m);
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// MSVC 6 and possibly others crash when encountering complicated integral
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// constant expressions. Avoid the check for now.
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// BOOST_STATIC_ASSERT(m == 0 || a < m);
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// BOOST_STATIC_ASSERT(m == 0 || c < m);
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/**
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* Constructs a linear_congruential generator, seeding it with @c x0.
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*/
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explicit linear_congruential(IntType x0 = 1)
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{
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seed(x0);
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// MSVC fails BOOST_STATIC_ASSERT with std::numeric_limits at class scope
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#ifndef BOOST_NO_LIMITS_COMPILE_TIME_CONSTANTS
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BOOST_STATIC_ASSERT(std::numeric_limits<IntType>::is_integer);
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#endif
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}
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/**
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* Constructs a @c linear_congruential generator and 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>
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linear_congruential(It& first, It last)
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{
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seed(first, last);
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}
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// compiler-generated copy constructor and assignment operator are fine
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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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void seed(IntType x0 = 1)
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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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_x = x0;
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} else {
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_x = x0 % modulus;
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}
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// handle negative seeds
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if(_x <= 0 && _x != 0) {
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_x += modulus;
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}
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// adjust to the correct range
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if(increment == 0 && _x == 0) {
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_x = 1;
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}
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assert(_x >= (min)());
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assert(_x <= (max)());
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}
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/**
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* seeds a @c linear_congruential generator 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>
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void seed(It& first, It last)
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{
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if(first == last)
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throw std::invalid_argument("linear_congruential::seed");
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seed(*first++);
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}
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/**
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* Returns the smallest value that the @c linear_congruential generator
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* can produce.
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*/
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result_type min BOOST_PREVENT_MACRO_SUBSTITUTION () const { return c == 0 ? 1 : 0; }
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/**
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* Returns the largest value that the @c linear_congruential generator
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* can produce.
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*/
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result_type max BOOST_PREVENT_MACRO_SUBSTITUTION () const { return modulus-1; }
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/** Returns the next value of the @c linear_congruential generator. */
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IntType operator()()
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{
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_x = const_mod<IntType, m>::mult_add(a, _x, c);
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return _x;
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}
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static bool validation(IntType x) { return val == x; }
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#ifdef BOOST_NO_OPERATORS_IN_NAMESPACE
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// Use a member function; Streamable concept not supported.
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bool operator==(const linear_congruential& rhs) const
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{ return _x == rhs._x; }
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bool operator!=(const linear_congruential& rhs) const
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{ return !(*this == rhs); }
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#else
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friend bool operator==(const linear_congruential& x,
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const linear_congruential& y)
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{ return x._x == y._x; }
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friend bool operator!=(const linear_congruential& x,
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const linear_congruential& y)
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{ return !(x == y); }
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#if !defined(BOOST_RANDOM_NO_STREAM_OPERATORS) && !BOOST_WORKAROUND(__BORLANDC__, BOOST_TESTED_AT(0x551))
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template<class CharT, class Traits>
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friend std::basic_ostream<CharT,Traits>&
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operator<<(std::basic_ostream<CharT,Traits>& os,
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const linear_congruential& lcg)
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{
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return os << lcg._x;
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}
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template<class CharT, class Traits>
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friend std::basic_istream<CharT,Traits>&
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operator>>(std::basic_istream<CharT,Traits>& is,
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linear_congruential& lcg)
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{
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return is >> lcg._x;
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}
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private:
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#endif
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#endif
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IntType _x;
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};
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// probably needs the "no native streams" caveat for STLPort
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#if !defined(__SGI_STL_PORT) && BOOST_WORKAROUND(__GNUC__, == 2)
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template<class IntType, IntType a, IntType c, IntType m, IntType val>
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std::ostream&
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operator<<(std::ostream& os,
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const linear_congruential<IntType,a,c,m,val>& lcg)
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{
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return os << lcg._x;
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}
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template<class IntType, IntType a, IntType c, IntType m, IntType val>
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std::istream&
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operator>>(std::istream& is,
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linear_congruential<IntType,a,c,m,val>& lcg)
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{
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return is >> lcg._x;
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}
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#elif defined(BOOST_RANDOM_NO_STREAM_OPERATORS) || BOOST_WORKAROUND(__BORLANDC__, BOOST_TESTED_AT(0x551))
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template<class CharT, class Traits, class IntType, IntType a, IntType c, IntType m, IntType val>
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std::basic_ostream<CharT,Traits>&
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operator<<(std::basic_ostream<CharT,Traits>& os,
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const linear_congruential<IntType,a,c,m,val>& lcg)
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{
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return os << lcg._x;
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}
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template<class CharT, class Traits, class IntType, IntType a, IntType c, IntType m, IntType val>
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std::basic_istream<CharT,Traits>&
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operator>>(std::basic_istream<CharT,Traits>& is,
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linear_congruential<IntType,a,c,m,val>& lcg)
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{
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return is >> lcg._x;
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}
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#endif
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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 c, IntType m, IntType val>
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const bool linear_congruential<IntType, a, c, m, val>::has_fixed_range;
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template<class IntType, IntType a, IntType c, IntType m, IntType val>
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const typename linear_congruential<IntType, a, c, m, val>::result_type linear_congruential<IntType, a, c, m, val>::min_value;
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template<class IntType, IntType a, IntType c, IntType m, IntType val>
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const typename linear_congruential<IntType, a, c, m, val>::result_type linear_congruential<IntType, a, c, m, val>::max_value;
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template<class IntType, IntType a, IntType c, IntType m, IntType val>
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const IntType linear_congruential<IntType,a,c,m,val>::modulus;
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#endif
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} // namespace random
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// validation values from the publications
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/**
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* The specialization \minstd_rand0 was originally suggested in
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*
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* @blockquote
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* A pseudo-random number generator for the System/360, P.A. Lewis,
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* A.S. Goodman, J.M. Miller, IBM Systems Journal, Vol. 8, No. 2,
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* 1969, pp. 136-146
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* @endblockquote
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*
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* It is examined more closely together with \minstd_rand in
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*
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* @blockquote
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* "Random Number Generators: Good ones are hard to find",
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* Stephen K. Park and Keith W. Miller, Communications of
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* the ACM, Vol. 31, No. 10, October 1988, pp. 1192-1201
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* @endblockquote
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*/
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typedef random::linear_congruential<int32_t, 16807, 0, 2147483647,
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1043618065> minstd_rand0;
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/** The specialization \minstd_rand was suggested in
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*
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* @blockquote
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* "Random Number Generators: Good ones are hard to find",
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* Stephen K. Park and Keith W. Miller, Communications of
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* the ACM, Vol. 31, No. 10, October 1988, pp. 1192-1201
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* @endblockquote
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*/
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typedef random::linear_congruential<int32_t, 48271, 0, 2147483647,
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399268537> minstd_rand;
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#if !defined(BOOST_NO_INT64_T) && !defined(BOOST_NO_INTEGRAL_INT64_T)
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/** Class @c rand48 models a \pseudo_random_number_generator. It uses
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* the linear congruential algorithm with the parameters a = 0x5DEECE66D,
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* c = 0xB, m = 2**48. It delivers identical results to the @c lrand48()
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* function available on some systems (assuming lcong48 has not been called).
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*
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* It is only available on systems where @c uint64_t is provided as an
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* integral type, so that for example static in-class constants and/or
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* enum definitions with large @c uint64_t numbers work.
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*/
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class rand48
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{
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public:
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typedef int32_t result_type;
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#ifndef BOOST_NO_INCLASS_MEMBER_INITIALIZATION
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static const bool has_fixed_range = true;
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static const int32_t min_value = 0;
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static const int32_t max_value = integer_traits<int32_t>::const_max;
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#else
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enum { has_fixed_range = false };
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#endif
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/**
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* Returns the smallest value that the generator can produce
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*/
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int32_t min BOOST_PREVENT_MACRO_SUBSTITUTION () const { return 0; }
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/**
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* Returns the largest value that the generator can produce
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*/
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int32_t max BOOST_PREVENT_MACRO_SUBSTITUTION () const { return std::numeric_limits<int32_t>::max BOOST_PREVENT_MACRO_SUBSTITUTION (); }
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#ifdef BOOST_RANDOM_DOXYGEN
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/**
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* If T is an integral type smaller than int46_t, constructs
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* a \rand48 generator with x(0) := (x0 << 16) | 0x330e. Otherwise
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* constructs a \rand48 generator with x(0) = x0.
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*/
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template<class T> explicit rand48(T x0 = 1);
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#else
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rand48() : lcf(cnv(static_cast<int32_t>(1))) {}
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template<class T> explicit rand48(T x0) : lcf(cnv(x0)) { }
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#endif
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template<class It> rand48(It& first, It last) : lcf(first, last) { }
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// compiler-generated copy ctor and assignment operator are fine
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#ifdef BOOST_RANDOM_DOXYGEN
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/**
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* If T is an integral type smaller than int46_t, changes
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* the current value x(n) of the generator to (x0 << 16) | 0x330e.
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* Otherwise changes the current value x(n) to x0.
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*/
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template<class T> void seed(T x0 = 1);
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#else
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void seed() { seed(static_cast<int32_t>(1)); }
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template<class T> void seed(T x0) { lcf.seed(cnv(x0)); }
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#endif
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template<class It> void seed(It& first, It last) { lcf.seed(first,last); }
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/**
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* Returns the next value of the generator.
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*/
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int32_t operator()() { return static_cast<int32_t>(lcf() >> 17); }
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// by experiment from lrand48()
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static bool validation(int32_t x) { return x == 1993516219; }
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#ifndef BOOST_NO_OPERATORS_IN_NAMESPACE
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#ifndef BOOST_RANDOM_NO_STREAM_OPERATORS
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template<class CharT,class Traits>
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friend std::basic_ostream<CharT,Traits>&
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operator<<(std::basic_ostream<CharT,Traits>& os, const rand48& r)
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{ os << r.lcf; return os; }
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template<class CharT,class Traits>
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friend std::basic_istream<CharT,Traits>&
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operator>>(std::basic_istream<CharT,Traits>& is, rand48& r)
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{ is >> r.lcf; return is; }
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#endif
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friend bool operator==(const rand48& x, const rand48& y)
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{ return x.lcf == y.lcf; }
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friend bool operator!=(const rand48& x, const rand48& y)
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{ return !(x == y); }
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#else
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// Use a member function; Streamable concept not supported.
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bool operator==(const rand48& rhs) const
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{ return lcf == rhs.lcf; }
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bool operator!=(const rand48& rhs) const
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{ return !(*this == rhs); }
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#endif
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private:
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/// \cond hide_private_members
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random::linear_congruential<uint64_t,
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uint64_t(0xDEECE66DUL) | (uint64_t(0x5) << 32), // xxxxULL is not portable
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0xB, uint64_t(1)<<48, /* unknown */ 0> lcf;
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template<class T>
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static uint64_t cnv(T x)
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{
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if(sizeof(T) < sizeof(uint64_t)) {
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return (static_cast<uint64_t>(x) << 16) | 0x330e;
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} else {
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return(static_cast<uint64_t>(x));
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}
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}
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static uint64_t cnv(float x) { return(static_cast<uint64_t>(x)); }
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static uint64_t cnv(double x) { return(static_cast<uint64_t>(x)); }
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static uint64_t cnv(long double x) { return(static_cast<uint64_t>(x)); }
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/// \endcond
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};
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#endif /* !BOOST_NO_INT64_T && !BOOST_NO_INTEGRAL_INT64_T */
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} // namespace boost
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#include <boost/random/detail/enable_warnings.hpp>
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#endif // BOOST_RANDOM_LINEAR_CONGRUENTIAL_HPP
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