/* boost random/linear_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: linear_congruential.hpp 60755 2010-03-22 00:45:06Z steven_watanabe $ * * Revision history * 2001-02-18 moved to individual header files */ #ifndef BOOST_RANDOM_LINEAR_CONGRUENTIAL_HPP #define BOOST_RANDOM_LINEAR_CONGRUENTIAL_HPP #include <iostream> #include <cassert> #include <stdexcept> #include <boost/config.hpp> #include <boost/limits.hpp> #include <boost/static_assert.hpp> #include <boost/random/detail/config.hpp> #include <boost/random/detail/const_mod.hpp> #include <boost/detail/workaround.hpp> #include <boost/random/detail/disable_warnings.hpp> namespace boost { namespace random { /** * Instantiations of class template linear_congruential model a * \pseudo_random_number_generator. Linear congruential pseudo-random * number generators are described in: * * "Mathematical methods in large-scale computing units", D. H. Lehmer, * Proc. 2nd Symposium on Large-Scale Digital Calculating Machines, * Harvard University Press, 1951, pp. 141-146 * * Let x(n) denote the sequence of numbers returned by some pseudo-random * number generator. Then for the linear congruential generator, * x(n+1) := (a * x(n) + c) mod m. Parameters for the generator are * x(0), a, c, m. The template parameter IntType shall denote an integral * type. It must be large enough to hold values a, c, and m. The template * parameters a and c must be smaller than m. * * Note: The quality of the generator crucially depends on the choice of * the parameters. User code should use one of the sensibly parameterized * generators such as minstd_rand instead. */ template<class IntType, IntType a, IntType c, IntType m, IntType val> class linear_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 = ( c == 0 ? 1 : 0 ); static const result_type max_value = m-1; #else BOOST_STATIC_CONSTANT(bool, has_fixed_range = false); #endif BOOST_STATIC_CONSTANT(IntType, multiplier = a); BOOST_STATIC_CONSTANT(IntType, increment = c); BOOST_STATIC_CONSTANT(IntType, modulus = m); // MSVC 6 and possibly others crash when encountering complicated integral // constant expressions. Avoid the check for now. // BOOST_STATIC_ASSERT(m == 0 || a < m); // BOOST_STATIC_ASSERT(m == 0 || c < m); /** * Constructs a linear_congruential generator, seeding it with @c x0. */ explicit linear_congruential(IntType x0 = 1) { seed(x0); // MSVC fails BOOST_STATIC_ASSERT with std::numeric_limits at class scope #ifndef BOOST_NO_LIMITS_COMPILE_TIME_CONSTANTS BOOST_STATIC_ASSERT(std::numeric_limits<IntType>::is_integer); #endif } /** * Constructs a @c linear_congruential generator and seeds it * with values taken from the itrator range [first, last) * and adjusts first to point to the element after the last one * used. If there are not enough elements, throws @c std::invalid_argument. * * first and last must be input iterators. */ template<class It> linear_congruential(It& first, It last) { seed(first, last); } // compiler-generated copy constructor and assignment operator are fine /** * If c mod m is zero and x0 mod m is zero, changes the current value of * the generator to 1. Otherwise, changes it to x0 mod m. If c is zero, * distinct seeds in the range [1,m) will leave the generator in distinct * states. If c is not zero, the range is [0,m). */ void seed(IntType x0 = 1) { // wrap _x if it doesn't fit in the destination if(modulus == 0) { _x = x0; } else { _x = x0 % modulus; } // handle negative seeds if(_x <= 0 && _x != 0) { _x += modulus; } // adjust to the correct range if(increment == 0 && _x == 0) { _x = 1; } assert(_x >= (min)()); assert(_x <= (max)()); } /** * seeds a @c linear_congruential generator with values taken * from the itrator range [first, last) and adjusts @c first to * point to the element after the last one used. If there are * not enough elements, throws @c std::invalid_argument. * * @c first and @c last must be input iterators. */ template<class It> void seed(It& first, It last) { if(first == last) throw std::invalid_argument("linear_congruential::seed"); seed(*first++); } /** * Returns the smallest value that the @c linear_congruential generator * can produce. */ result_type min BOOST_PREVENT_MACRO_SUBSTITUTION () const { return c == 0 ? 1 : 0; } /** * Returns the largest value that the @c linear_congruential generator * can produce. */ result_type max BOOST_PREVENT_MACRO_SUBSTITUTION () const { return modulus-1; } /** Returns the next value of the @c linear_congruential generator. */ IntType operator()() { _x = const_mod<IntType, m>::mult_add(a, _x, c); return _x; } static bool validation(IntType x) { return val == x; } #ifdef BOOST_NO_OPERATORS_IN_NAMESPACE // Use a member function; Streamable concept not supported. bool operator==(const linear_congruential& rhs) const { return _x == rhs._x; } bool operator!=(const linear_congruential& rhs) const { return !(*this == rhs); } #else friend bool operator==(const linear_congruential& x, const linear_congruential& y) { return x._x == y._x; } friend bool operator!=(const linear_congruential& x, const linear_congruential& y) { return !(x == y); } #if !defined(BOOST_RANDOM_NO_STREAM_OPERATORS) && !BOOST_WORKAROUND(__BORLANDC__, BOOST_TESTED_AT(0x551)) template<class CharT, class Traits> friend std::basic_ostream<CharT,Traits>& operator<<(std::basic_ostream<CharT,Traits>& os, const linear_congruential& lcg) { return os << lcg._x; } template<class CharT, class Traits> friend std::basic_istream<CharT,Traits>& operator>>(std::basic_istream<CharT,Traits>& is, linear_congruential& lcg) { return is >> lcg._x; } private: #endif #endif IntType _x; }; // probably needs the "no native streams" caveat for STLPort #if !defined(__SGI_STL_PORT) && BOOST_WORKAROUND(__GNUC__, == 2) template<class IntType, IntType a, IntType c, IntType m, IntType val> std::ostream& operator<<(std::ostream& os, const linear_congruential<IntType,a,c,m,val>& lcg) { return os << lcg._x; } template<class IntType, IntType a, IntType c, IntType m, IntType val> std::istream& operator>>(std::istream& is, linear_congruential<IntType,a,c,m,val>& lcg) { return is >> lcg._x; } #elif defined(BOOST_RANDOM_NO_STREAM_OPERATORS) || BOOST_WORKAROUND(__BORLANDC__, BOOST_TESTED_AT(0x551)) template<class CharT, class Traits, class IntType, IntType a, IntType c, IntType m, IntType val> std::basic_ostream<CharT,Traits>& operator<<(std::basic_ostream<CharT,Traits>& os, const linear_congruential<IntType,a,c,m,val>& lcg) { return os << lcg._x; } template<class CharT, class Traits, class IntType, IntType a, IntType c, IntType m, IntType val> std::basic_istream<CharT,Traits>& operator>>(std::basic_istream<CharT,Traits>& is, linear_congruential<IntType,a,c,m,val>& lcg) { return is >> lcg._x; } #endif #ifndef BOOST_NO_INCLASS_MEMBER_INITIALIZATION // A definition is required even for integral static constants template<class IntType, IntType a, IntType c, IntType m, IntType val> const bool linear_congruential<IntType, a, c, m, val>::has_fixed_range; template<class IntType, IntType a, IntType c, IntType m, IntType val> const typename linear_congruential<IntType, a, c, m, val>::result_type linear_congruential<IntType, a, c, m, val>::min_value; template<class IntType, IntType a, IntType c, IntType m, IntType val> const typename linear_congruential<IntType, a, c, m, val>::result_type linear_congruential<IntType, a, c, m, val>::max_value; template<class IntType, IntType a, IntType c, IntType m, IntType val> const IntType linear_congruential<IntType,a,c,m,val>::modulus; #endif } // namespace random // validation values from the publications /** * The specialization \minstd_rand0 was originally suggested in * * @blockquote * A pseudo-random number generator for the System/360, P.A. Lewis, * A.S. Goodman, J.M. Miller, IBM Systems Journal, Vol. 8, No. 2, * 1969, pp. 136-146 * @endblockquote * * It is examined more closely together with \minstd_rand in * * @blockquote * "Random Number Generators: Good ones are hard to find", * Stephen K. Park and Keith W. Miller, Communications of * the ACM, Vol. 31, No. 10, October 1988, pp. 1192-1201 * @endblockquote */ typedef random::linear_congruential<int32_t, 16807, 0, 2147483647, 1043618065> minstd_rand0; /** The specialization \minstd_rand was suggested in * * @blockquote * "Random Number Generators: Good ones are hard to find", * Stephen K. Park and Keith W. Miller, Communications of * the ACM, Vol. 31, No. 10, October 1988, pp. 1192-1201 * @endblockquote */ typedef random::linear_congruential<int32_t, 48271, 0, 2147483647, 399268537> minstd_rand; #if !defined(BOOST_NO_INT64_T) && !defined(BOOST_NO_INTEGRAL_INT64_T) /** Class @c rand48 models a \pseudo_random_number_generator. It uses * the linear congruential algorithm with the parameters a = 0x5DEECE66D, * c = 0xB, m = 2**48. It delivers identical results to the @c lrand48() * function available on some systems (assuming lcong48 has not been called). * * It is only available on systems where @c uint64_t is provided as an * integral type, so that for example static in-class constants and/or * enum definitions with large @c uint64_t numbers work. */ class rand48 { public: typedef int32_t result_type; #ifndef BOOST_NO_INCLASS_MEMBER_INITIALIZATION static const bool has_fixed_range = true; static const int32_t min_value = 0; static const int32_t max_value = integer_traits<int32_t>::const_max; #else enum { has_fixed_range = false }; #endif /** * Returns the smallest value that the generator can produce */ int32_t min BOOST_PREVENT_MACRO_SUBSTITUTION () const { return 0; } /** * Returns the largest value that the generator can produce */ int32_t max BOOST_PREVENT_MACRO_SUBSTITUTION () const { return std::numeric_limits<int32_t>::max BOOST_PREVENT_MACRO_SUBSTITUTION (); } #ifdef BOOST_RANDOM_DOXYGEN /** * If T is an integral type smaller than int46_t, constructs * a \rand48 generator with x(0) := (x0 << 16) | 0x330e. Otherwise * constructs a \rand48 generator with x(0) = x0. */ template<class T> explicit rand48(T x0 = 1); #else rand48() : lcf(cnv(static_cast<int32_t>(1))) {} template<class T> explicit rand48(T x0) : lcf(cnv(x0)) { } #endif template<class It> rand48(It& first, It last) : lcf(first, last) { } // compiler-generated copy ctor and assignment operator are fine #ifdef BOOST_RANDOM_DOXYGEN /** * If T is an integral type smaller than int46_t, changes * the current value x(n) of the generator to (x0 << 16) | 0x330e. * Otherwise changes the current value x(n) to x0. */ template<class T> void seed(T x0 = 1); #else void seed() { seed(static_cast<int32_t>(1)); } template<class T> void seed(T x0) { lcf.seed(cnv(x0)); } #endif template<class It> void seed(It& first, It last) { lcf.seed(first,last); } /** * Returns the next value of the generator. */ int32_t operator()() { return static_cast<int32_t>(lcf() >> 17); } // by experiment from lrand48() static bool validation(int32_t x) { return x == 1993516219; } #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, const rand48& r) { os << r.lcf; return os; } template<class CharT,class Traits> friend std::basic_istream<CharT,Traits>& operator>>(std::basic_istream<CharT,Traits>& is, rand48& r) { is >> r.lcf; return is; } #endif friend bool operator==(const rand48& x, const rand48& y) { return x.lcf == y.lcf; } friend bool operator!=(const rand48& x, const rand48& y) { return !(x == y); } #else // Use a member function; Streamable concept not supported. bool operator==(const rand48& rhs) const { return lcf == rhs.lcf; } bool operator!=(const rand48& rhs) const { return !(*this == rhs); } #endif private: /// \cond hide_private_members random::linear_congruential<uint64_t, uint64_t(0xDEECE66DUL) | (uint64_t(0x5) << 32), // xxxxULL is not portable 0xB, uint64_t(1)<<48, /* unknown */ 0> lcf; template<class T> static uint64_t cnv(T x) { if(sizeof(T) < sizeof(uint64_t)) { return (static_cast<uint64_t>(x) << 16) | 0x330e; } else { return(static_cast<uint64_t>(x)); } } static uint64_t cnv(float x) { return(static_cast<uint64_t>(x)); } static uint64_t cnv(double x) { return(static_cast<uint64_t>(x)); } static uint64_t cnv(long double x) { return(static_cast<uint64_t>(x)); } /// \endcond }; #endif /* !BOOST_NO_INT64_T && !BOOST_NO_INTEGRAL_INT64_T */ } // namespace boost #include <boost/random/detail/enable_warnings.hpp> #endif // BOOST_RANDOM_LINEAR_CONGRUENTIAL_HPP