1 // random number generation -*- C++ -*-
3 // Copyright (C) 2006 Free Software Foundation, Inc.
5 // This file is part of the GNU ISO C++ Library. This library is free
6 // software; you can redistribute it and/or modify it under the
7 // terms of the GNU General Public License as published by the
8 // Free Software Foundation; either version 2, or (at your option)
11 // This library is distributed in the hope that it will be useful,
12 // but WITHOUT ANY WARRANTY; without even the implied warranty of
13 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
14 // GNU General Public License for more details.
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18 // Software Foundation, 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301,
21 // As a special exception, you may use this file as part of a free software
22 // library without restriction. Specifically, if other files instantiate
23 // templates or use macros or inline functions from this file, or you compile
24 // this file and link it with other files to produce an executable, this
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28 // the GNU General Public License.
30 #ifndef _STD_TR1_RANDOM
31 #define _STD_TR1_RANDOM 1
35 * This is a TR1 C++ Library header.
39 #include <bits/concept_check.h>
40 #include <bits/cpp_type_traits.h>
42 #include <debug/debug.h>
46 #include <tr1/type_traits>
51 _GLIBCXX_BEGIN_NAMESPACE(tr1)
53 // [5.1] Random number generation
56 * @addtogroup tr1_random Random Number Generation
57 * A facility for generating random numbers on selected distributions.
62 * Implementation-space details.
66 // Type selectors -- are these already implemented elsewhere?
67 template<bool, typename _TpTrue, typename _TpFalse>
70 typedef _TpTrue _Type;
73 template<typename _TpTrue, typename _TpFalse>
74 struct _Select<false, _TpTrue, _TpFalse>
76 typedef _TpFalse _Type;
80 * An adaptor class for converting the output of any Generator into
81 * the input for a specific Distribution.
83 template<typename _Generator, typename _Distribution>
86 typedef typename _Generator::result_type generated_type;
87 typedef typename _Distribution::input_type result_type;
90 _Adaptor(const _Generator& __g)
101 * Converts a value generated by the adapted random number generator into a
102 * value in the input domain for the dependent random number distribution.
104 * Because the type traits are compile time constants only the appropriate
105 * clause of the if statements will actually be emitted by the compiler.
107 template<typename _Generator, typename _Distribution>
108 typename _Adaptor<_Generator, _Distribution>::result_type
109 _Adaptor<_Generator, _Distribution>::
112 result_type __return_value = 0;
113 if (is_integral<generated_type>::value
114 && is_integral<result_type>::value)
115 __return_value = _M_g();
116 else if (is_integral<generated_type>::value
117 && !is_integral<result_type>::value)
118 __return_value = result_type(_M_g())
119 / result_type(_M_g.max() - _M_g.min() + 1);
120 else if (!is_integral<generated_type>::value
121 && !is_integral<result_type>::value)
122 __return_value = result_type(_M_g())
123 / result_type(_M_g.max() - _M_g.min());
124 return __return_value;
127 template<typename _UIntType, int __w, bool =
128 __w != std::numeric_limits<_UIntType>::digits>
130 { static const _UIntType __value = 0; };
132 template<typename _UIntType, int __w>
133 struct _Shift<_UIntType, __w, true>
134 { static const _UIntType __value = _UIntType(1) << __w; };
136 } // namespace std::tr1::_Private
140 * Produces random numbers on a given disribution function using a un uniform
141 * random number generation engine.
143 * @todo the engine_value_type needs to be studied more carefully.
145 template<typename _Generator, typename _Dist>
146 class variate_generator
148 // Concept requirements.
149 __glibcxx_class_requires(_Generator, _CopyConstructibleConcept)
150 // __glibcxx_class_requires(_Generator, _GeneratorConcept)
151 // __glibcxx_class_requires(_Dist, _GeneratorConcept)
154 typedef _Generator engine_type;
155 typedef _Private::_Adaptor<_Generator, _Dist> engine_value_type;
156 typedef _Dist distribution_type;
157 typedef typename _Dist::result_type result_type;
159 // tr1:5.1.1 table 5.1 requirement
160 typedef typename std::__enable_if<result_type,
161 is_arithmetic<result_type>::value
162 >::__type _IsValidType;
166 * Constructs a variate generator with the uniform random number
167 * generator @p __eng for the random distribution @p __dist.
169 * @throws Any exceptions which may thrown by the copy constructors of
170 * the @p _Generator or @p _Dist objects.
172 variate_generator(engine_type __eng, distribution_type __dist)
173 : _M_engine(__eng), _M_dist(__dist) { }
176 * Gets the next generated value on the distribution.
181 template<typename _Tp>
183 operator()(_Tp __value);
186 * Gets a reference to the underlying uniform random number generator
191 { return _M_engine; }
194 * Gets a const reference to the underlying uniform random number
197 const engine_value_type&
199 { return _M_engine; }
202 * Gets a reference to the underlying random distribution.
209 * Gets a const reference to the underlying random distribution.
211 const distribution_type&
216 * Gets the closed lower bound of the distribution interval.
220 { return this->distribution().min(); }
223 * Gets the closed upper bound of the distribution interval.
227 { return this->distribution().max(); }
230 engine_value_type _M_engine;
231 distribution_type _M_dist;
235 * Gets the next random value on the given distribution.
237 template<typename _Generator, typename _Dist>
238 typename variate_generator<_Generator, _Dist>::result_type
239 variate_generator<_Generator, _Dist>::
241 { return _M_dist(_M_engine); }
246 template<typename _Generator, typename _Dist>
247 template<typename _Tp>
248 typename variate_generator<_Generator, _Dist>::result_type
249 variate_generator<_Generator, _Dist>::
250 operator()(_Tp __value)
251 { return _M_dist(_M_engine, __value); }
255 * @addtogroup tr1_random_generators Random Number Generators
256 * @ingroup tr1_random
258 * These classes define objects which provide random or pseudorandom numbers,
259 * either from a discrete or a continuous interval. The random number
260 * generator supplied as a part of this library are all uniform random number
261 * generators which provide a sequence of random number uniformly distributed
264 * A number generator is a function object with an operator() that takes zero
265 * arguments and returns a number.
267 * A compliant random number generator must satisy the following requirements.
268 * <table border=1 cellpadding=10 cellspacing=0>
269 * <caption align=top>Random Number Generator Requirements</caption>
270 * <tr><td>To be documented.</td></tr>
277 * @brief A model of a linear congruential random number generator.
279 * A random number generator that produces pseudorandom numbers using the
280 * linear function @f$x_{i+1}\leftarrow(ax_{i} + c) \bmod m @f$.
282 * The template parameter @p _UIntType must be an unsigned integral type
283 * large enough to store values up to (__m-1). If the template parameter
284 * @p __m is 0, the modulus @p __m used is
285 * std::numeric_limits<_UIntType>::max() plus 1. Otherwise, the template
286 * parameters @p __a and @p __c must be less than @p __m.
288 * The size of the state is @f$ 1 @f$.
290 template<class _UIntType, _UIntType __a, _UIntType __c, _UIntType __m>
291 class linear_congruential
293 __glibcxx_class_requires(_UIntType, _UnsignedIntegerConcept)
294 // __glibcpp_class_requires(__a < __m && __c < __m)
297 /** The type of the generated random value. */
298 typedef _UIntType result_type;
300 /** The multiplier. */
301 static const _UIntType multiplier = __a;
303 static const _UIntType increment = __c;
305 static const _UIntType modulus = __m;
308 * Constructs a %linear_congruential random number generator engine with
309 * seed @p __s. The default seed value is 1.
311 * @param __s The initial seed value.
314 linear_congruential(unsigned long __x0 = 1)
315 { this->seed(__x0); }
318 * Constructs a %linear_congruential random number generator engine
319 * seeded from the generator function @p __g.
321 * @param __g The seed generator function.
324 linear_congruential(_Gen& __g)
328 * Reseeds the %linear_congruential random number generator engine
329 * sequence to the seed @g __s.
331 * @param __s The new seed.
334 seed(unsigned long __s = 1);
337 * Reseeds the %linear_congruential random number generator engine
338 * sequence using values from the generator function @p __g.
340 * @param __g the seed generator function.
345 { seed(__g, typename is_fundamental<_Gen>::type()); }
348 * Gets the smallest possible value in the output range.
354 * Gets the largest possible value in the output range.
360 * Gets the next random number in the sequence.
366 * Compares two linear congruential random number generator objects of the
367 * same type for equality.
369 * @param __lhs A linear congruential random number generator object.
370 * @param __rhs Another linear congruential random number generator obj.
372 * @returns true if the two objects are equal, false otherwise.
375 operator==(const linear_congruential& __lhs,
376 const linear_congruential& __rhs)
377 { return __lhs._M_x == __rhs._M_x; }
380 * Compares two linear congruential random number generator objects of the
381 * same type for inequality.
383 * @param __lhs A linear congruential random number generator object.
384 * @param __rhs Another linear congruential random number generator obj.
386 * @returns true if the two objects are not equal, false otherwise.
389 operator!=(const linear_congruential& __lhs,
390 const linear_congruential& __rhs)
391 { return !(__lhs == __rhs); }
394 * Writes the textual representation of the state x(i) of x to @p __os.
396 * @param __os The output stream.
397 * @param __lcr A linear_congruential random number generator.
400 template<typename _CharT, typename _Traits>
401 friend std::basic_ostream<_CharT, _Traits>&
402 operator<<(std::basic_ostream<_CharT, _Traits>& __os,
403 const linear_congruential& __lcr)
404 { return __os << __lcr._M_x; }
407 * Sets the state of the engine by reading its textual
408 * representation from @p __is.
410 * The textual representation must have been previously written using an
411 * output stream whose imbued locale and whose type's template
412 * specialization arguments _CharT and _Traits were the same as those of
415 * @param __is The input stream.
416 * @param __lcr A linear_congruential random number generator.
419 template<typename _CharT, typename _Traits>
420 friend std::basic_istream<_CharT, _Traits>&
421 operator>>(std::basic_istream<_CharT, _Traits>& __is,
422 linear_congruential& __lcr)
423 { return __is >> __lcr._M_x; }
428 seed(_Gen& __g, true_type)
429 { return seed(static_cast<unsigned long>(__g)); }
433 seed(_Gen& __g, false_type);
440 * The classic Minimum Standard rand0 of Lewis, Goodman, and Miller.
442 typedef linear_congruential<unsigned int, 16807, 0, 2147483647> minstd_rand0;
445 * An alternative LCR (Lehmer Generator function) .
447 typedef linear_congruential<unsigned int, 48271, 0, 2147483647> minstd_rand;
451 * A generalized feedback shift register discrete random number generator.
453 * This algorithm avoind multiplication and division and is designed to be
454 * friendly to a pipelined architecture. If the parameters are chosen
455 * correctly, this generator will produce numbers with a very long period and
456 * fairly good apparent entropy, although still not cryptographically strong.
458 * The best way to use this generator is with the predefined mt19937 class.
460 * This algorithm was originally invented by Makoto Matsumoto and
463 * @var word_size The number of bits in each element of the state vector.
464 * @var state_size The degree of recursion.
465 * @var shift_size The period parameter.
466 * @var mask_bits The separation point bit index.
467 * @var parameter_a The last row of the twist matrix.
468 * @var output_u The first right-shift tempering matrix parameter.
469 * @var output_s The first left-shift tempering matrix parameter.
470 * @var output_b The first left-shift tempering matrix mask.
471 * @var output_t The second left-shift tempering matrix parameter.
472 * @var output_c The second left-shift tempering matrix mask.
473 * @var output_l The second right-shift tempering matrix parameter.
475 template<class _UIntType, int __w, int __n, int __m, int __r,
476 _UIntType __a, int __u, int __s, _UIntType __b, int __t,
477 _UIntType __c, int __l>
478 class mersenne_twister
480 __glibcxx_class_requires(_UIntType, _UnsignedIntegerConcept)
484 typedef _UIntType result_type ;
487 static const int word_size = __w;
488 static const int state_size = __n;
489 static const int shift_size = __m;
490 static const int mask_bits = __r;
491 static const _UIntType parameter_a = __a;
492 static const int output_u = __u;
493 static const int output_s = __s;
494 static const _UIntType output_b = __b;
495 static const int output_t = __t;
496 static const _UIntType output_c = __c;
497 static const int output_l = __l;
499 // constructors and member function
504 mersenne_twister(unsigned long __value)
508 mersenne_twister(_Gen& __g)
516 seed(unsigned long __value);
521 { seed(__g, typename is_fundamental<_Gen>::type()); }
529 { return _Private::_Shift<_UIntType, __w>::__value - 1; }
535 * Compares two % mersenne_twister random number generator objects of
536 * the same type for equality.
538 * @param __lhs A % mersenne_twister random number generator object.
539 * @param __rhs Another % mersenne_twister random number generator
542 * @returns true if the two objects are equal, false otherwise.
545 operator==(const mersenne_twister& __lhs,
546 const mersenne_twister& __rhs)
547 { return std::equal(__lhs._M_x, __lhs._M_x + state_size, __rhs._M_x); }
550 * Compares two % mersenne_twister random number generator objects of
551 * the same type for inequality.
553 * @param __lhs A % mersenne_twister random number generator object.
554 * @param __rhs Another % mersenne_twister random number generator
557 * @returns true if the two objects are not equal, false otherwise.
560 operator!=(const mersenne_twister& __lhs,
561 const mersenne_twister& __rhs)
562 { return !(__lhs == __rhs); }
565 * Inserts the current state of a % mersenne_twister random number
566 * generator engine @p __x into the output stream @p __os.
568 * @param __os An output stream.
569 * @param __x A % mersenne_twister random number generator engine.
571 * @returns The output stream with the state of @p __x inserted or in
574 template<typename _CharT, typename _Traits>
575 friend std::basic_ostream<_CharT, _Traits>&
576 operator<<(std::basic_ostream<_CharT, _Traits>& __os,
577 const mersenne_twister& __x)
579 std::copy(__x._M_x, __x._M_x + state_size,
580 std::ostream_iterator<_UIntType>(__os, " "));
585 * Extracts the current state of a % mersenne_twister random number
586 * generator engine @p __x from the input stream @p __is.
588 * @param __is An input stream.
589 * @param __x A % mersenne_twister random number generator engine.
591 * @returns The input stream with the state of @p __x extracted or in
594 template<typename _CharT, typename _Traits>
595 friend std::basic_istream<_CharT, _Traits>&
596 operator>>(std::basic_istream<_CharT, _Traits>& __is,
597 mersenne_twister& __x)
599 for (int __i = 0; __i < state_size; ++__i)
600 __is >> __x._M_x[__i];
607 seed(_Gen& __g, true_type)
608 { return seed(static_cast<unsigned long>(__g)); }
612 seed(_Gen& __g, false_type);
615 _UIntType _M_x[state_size];
620 * The classic Mersenne Twister.
623 * M. Matsumoto and T. Nishimura, "Mersenne Twister: A 623-Dimensionally
624 * Equidistributed Uniform Pseudo-Random Number Generator", ACM Transactions
625 * on Modeling and Computer Simulation, Vol. 8, No. 1, January 1998, pp 3-30.
627 typedef mersenne_twister<
628 unsigned long, 32, 624, 397, 31,
636 * @brief The Marsaglia-Zaman generator.
638 * This is a model of a Generalized Fibonacci discrete random number
639 * generator, sometimes referred to as the SWC generator.
641 * A discrete random number generator that produces pseudorandom numbers using
642 * @f$x_{i}\leftarrow(x_{i - s} - x_{i - r} - carry_{i-1}) \bmod m @f$.
644 * The size of the state is @f$ r @f$
645 * and the maximum period of the generator is @f$ m^r - m^s -1 @f$.
647 * N1688[4.13] says "the template parameter _IntType shall denote an integral
648 * type large enough to store values up to m."
651 * @var _M_x The state of te generator. This is a ring buffer.
652 * @var _M_carry The carry.
653 * @var _M_p Current index of x(i - r).
656 template<typename _IntType, _IntType __m, int __s, int __r>
657 class subtract_with_carry
659 __glibcxx_class_requires(_IntType, _IntegerConcept)
662 /** The type of the generated random value. */
663 typedef _IntType result_type;
666 static const _IntType modulus = __m;
667 static const int long_lag = __r;
668 static const int short_lag = __s;
672 * Constructs a default-initialized % subtract_with_carry random number
675 subtract_with_carry()
679 * Constructs an explicitly seeded % subtract_with_carry random number
683 subtract_with_carry(unsigned long __value)
684 { this->seed(__value); }
687 * Constructs a % subtract_with_carry random number generator seeded from
688 * the PAD iterated by [__first, last).
691 subtract_with_carry(_Gen& __g)
695 * Seeds the initial state @f$ x_0 @f$ of the random number generator.
697 * @note This implementation follows the tr1 specification but will
698 * obviously not work correctly on all platforms, since it has hardcoded
699 * values that may overflow ints on some platforms.
701 * N1688[4.19] modifies this as follows.
702 * If @p __value == 0, sets value to 19780503. In any case, with a linear
703 * congruential generator lcg(i) having parameters @f$ m_{lcg} =
704 * 2147483563, a_{lcg} = 40014, c_{lcg} = 0, and lcg(0) = value @f$, sets
705 * @f$ x_{-r} \dots x_{-1} @f$ to
706 * @f$ lcg(1) \bmod m \dots lcg(r) \bmod m @f$ respectively.
707 * If @f$ x_{-1} = 0 @f$ set carry to 1, otherwise sets carry to 0.
710 seed(unsigned long __value = 19780503);
713 * Seeds the initial state @f$ x_0 @f$ of the % subtract_with_carry
714 * random number generator.
719 { seed(__g, typename is_fundamental<_Gen>::type()); }
722 * Gets the inclusive minimum value of the range of random integers
723 * returned by this generator.
730 * Gets the inclusive maximum value of the range of random integers
731 * returned by this generator.
735 { return this->modulus - 1; }
738 * Gets the next random number in the sequence.
744 * Compares two % subtract_with_carry random number generator objects of
745 * the same type for equality.
747 * @param __lhs A % subtract_with_carry random number generator object.
748 * @param __rhs Another % subtract_with_carry random number generator
751 * @returns true if the two objects are equal, false otherwise.
754 operator==(const subtract_with_carry& __lhs,
755 const subtract_with_carry& __rhs)
756 { return std::equal(__lhs._M_x, __lhs._M_x + long_lag, __rhs._M_x); }
759 * Compares two % subtract_with_carry random number generator objects of
760 * the same type for inequality.
762 * @param __lhs A % subtract_with_carry random number generator object.
763 * @param __rhs Another % subtract_with_carry random number generator
766 * @returns true if the two objects are not equal, false otherwise.
769 operator!=(const subtract_with_carry& __lhs,
770 const subtract_with_carry& __rhs)
771 { return !(__lhs == __rhs); }
774 * Inserts the current state of a % subtract_with_carry random number
775 * generator engine @p __x into the output stream @p __os.
777 * @param __os An output stream.
778 * @param __x A % subtract_with_carry random number generator engine.
780 * @returns The output stream with the state of @p __x inserted or in
783 template<typename _CharT, typename _Traits>
784 friend std::basic_ostream<_CharT, _Traits>&
785 operator<<(std::basic_ostream<_CharT, _Traits>& __os,
786 const subtract_with_carry& __x)
788 std::copy(__x._M_x, __x._M_x + long_lag,
789 std::ostream_iterator<_IntType>(__os, " "));
790 return __os << __x._M_carry;
794 * Extracts the current state of a % subtract_with_carry random number
795 * generator engine @p __x from the input stream @p __is.
797 * @param __is An input stream.
798 * @param __x A % subtract_with_carry random number generator engine.
800 * @returns The input stream with the state of @p __x extracted or in
803 template<typename _CharT, typename _Traits>
804 friend std::basic_istream<_CharT, _Traits>&
805 operator>>(std::basic_istream<_CharT, _Traits>& __is,
806 subtract_with_carry& __x)
808 for (int __i = 0; __i < long_lag; ++__i)
809 __is >> __x._M_x[__i];
810 __is >> __x._M_carry;
817 seed(_Gen& __g, true_type)
818 { return seed(static_cast<unsigned long>(__g)); }
822 seed(_Gen& __g, false_type);
826 result_type _M_x[long_lag];
827 result_type _M_carry;
832 * Produces random numbers from some base engine by discarding blocks of
835 * 0 <= @p __r <= @p __p
837 template<class _UniformRandomNumberGenerator, int __p, int __r>
840 // __glibcxx_class_requires(typename base_type::result_type,
841 // ArithmeticTypeConcept)
844 /** The type of the underlying generator engine. */
845 typedef _UniformRandomNumberGenerator base_type;
846 /** The type of the generated random value. */
847 typedef typename base_type::result_type result_type;
850 static const int block_size = __p;
851 static const int used_block = __r;
854 * Constructs a default %discard_block engine.
856 * The underlying engine is default constructed as well.
862 * Copy constructs a %discard_block engine.
864 * Copies an existing base class random number geenerator.
865 * @param rng An existing (base class) engine object.
868 discard_block(const base_type& __rng)
869 : _M_b(__rng), _M_n(0) { }
872 * Seed constructs a %discard_block engine.
874 * Constructs the underlying generator engine seeded with @p __s.
875 * @param __s A seed value for the base class engine.
878 discard_block(unsigned long __s)
879 : _M_b(__s), _M_n(0) { }
882 * Generator constructs a %discard_block engine.
884 * @param __g A seed generator function.
887 discard_block(_Gen& __g)
888 : _M_b(__g), _M_n(0) { }
891 * Reseeds the %discard_block object with the default seed for the
892 * underlying base class generator engine.
901 * Reseeds the %discard_block object with the given seed generator
903 * @param __g A seed generator function.
913 * Gets a const reference to the underlying generator engine object.
920 * Gets the minimum value in the generated random number range.
924 { return _M_b.min(); }
927 * Gets the maximum value in the generated random number range.
931 { return _M_b.max(); }
934 * Gets the next value in the generated random number sequence.
940 * Compares two %discard_block random number generator objects of
941 * the same type for equality.
943 * @param __lhs A %discard_block random number generator object.
944 * @param __rhs Another %discard_block random number generator
947 * @returns true if the two objects are equal, false otherwise.
950 operator==(const discard_block& __lhs, const discard_block& __rhs)
951 { return (__lhs._M_b == __rhs._M_b) && (__lhs._M_n == __rhs._M_n); }
954 * Compares two %discard_block random number generator objects of
955 * the same type for inequality.
957 * @param __lhs A %discard_block random number generator object.
958 * @param __rhs Another %discard_block random number generator
961 * @returns true if the two objects are not equal, false otherwise.
964 operator!=(const discard_block& __lhs, const discard_block& __rhs)
965 { return !(__lhs == __rhs); }
968 * Inserts the current state of a %discard_block random number
969 * generator engine @p __x into the output stream @p __os.
971 * @param __os An output stream.
972 * @param __x A %discard_block random number generator engine.
974 * @returns The output stream with the state of @p __x inserted or in
977 template<typename _CharT, typename _Traits>
978 friend std::basic_ostream<_CharT, _Traits>&
979 operator<<(std::basic_ostream<_CharT, _Traits>& __os,
980 const discard_block& __x)
981 { return __os << __x._M_b << " " << __x._M_n; }
984 * Extracts the current state of a % subtract_with_carry random number
985 * generator engine @p __x from the input stream @p __is.
987 * @param __is An input stream.
988 * @param __x A %discard_block random number generator engine.
990 * @returns The input stream with the state of @p __x extracted or in
993 template<typename _CharT, typename _Traits>
994 friend std::basic_istream<_CharT, _Traits>&
995 operator>>(std::basic_istream<_CharT, _Traits>& __is,
997 { return __is >> __x._M_b >> __x._M_n; }
1006 * James's luxury-level-3 integer adaptation of Luescher's generator.
1008 typedef discard_block<
1009 subtract_with_carry<int, (1 << 24), 10, 24>,
1015 * James's luxury-level-4 integer adaptation of Luescher's generator.
1017 typedef discard_block<
1018 subtract_with_carry<int, (1 << 24), 10, 24>,
1025 * A random number generator adaptor class that combines two random number
1026 * generator engines into a single output sequence.
1028 template<class _UniformRandomNumberGenerator1, int __s1,
1029 class _UniformRandomNumberGenerator2, int __s2>
1032 // __glibcxx_class_requires(typename _UniformRandomNumberGenerator1::
1033 // result_type, ArithmeticTypeConcept)
1034 // __glibcxx_class_requires(typename _UniformRandomNumberGenerator2::
1035 // result_type, ArithmeticTypeConcept)
1038 /** The type of the the first underlying generator engine. */
1039 typedef _UniformRandomNumberGenerator1 base1_type;
1040 /** The type of the the second underlying generator engine. */
1041 typedef _UniformRandomNumberGenerator2 base2_type;
1044 typedef typename base1_type::result_type _Result_type1;
1045 typedef typename base2_type::result_type _Result_type2;
1048 /** The type of the generated random value. */
1049 typedef typename _Private::_Select<
1050 (sizeof(_Result_type1) > sizeof(_Result_type2)),
1051 _Result_type1, _Result_type2>::_Type result_type;
1054 static const int shift1 = __s1;
1055 static const int shift2 = __s2;
1057 // constructors and member function
1060 xor_combine(const base1_type& __rng1, const base2_type& __rng2)
1061 : _M_b1(__rng1), _M_b2(__rng2) { }
1063 xor_combine(unsigned long __s)
1064 : _M_b1(__s), _M_b2(__s + 1) { }
1066 template<class _Gen>
1067 xor_combine(_Gen& __g)
1068 : _M_b1(__g), _M_b2(__g) { }
1077 template<class _Gen>
1095 { return _M_b1.min() ^ _M_b2.min(); }
1099 { return _M_b1.max() | _M_b2.max(); }
1102 * Gets the next random number in the sequence.
1106 { return ((_M_b1() << shift1) ^ (_M_b2() << shift2)); }
1109 * Compares two %xor_combine random number generator objects of
1110 * the same type for equality.
1112 * @param __lhs A %xor_combine random number generator object.
1113 * @param __rhs Another %xor_combine random number generator
1116 * @returns true if the two objects are equal, false otherwise.
1119 operator==(const xor_combine& __lhs, const xor_combine& __rhs)
1121 return (__lhs.base1() == __rhs.base1())
1122 && (__lhs.base2() == __rhs.base2());
1126 * Compares two %xor_combine random number generator objects of
1127 * the same type for inequality.
1129 * @param __lhs A %xor_combine random number generator object.
1130 * @param __rhs Another %xor_combine random number generator
1133 * @returns true if the two objects are not equal, false otherwise.
1136 operator!=(const xor_combine& __lhs, const xor_combine& __rhs)
1137 { return !(__lhs == __rhs); }
1140 * Inserts the current state of a %xor_combine random number
1141 * generator engine @p __x into the output stream @p __os.
1143 * @param __os An output stream.
1144 * @param __x A %xor_combine random number generator engine.
1146 * @returns The output stream with the state of @p __x inserted or in
1149 template<typename _CharT, typename _Traits>
1150 friend std::basic_ostream<_CharT, _Traits>&
1151 operator<<(std::basic_ostream<_CharT, _Traits>& __os,
1152 const xor_combine& __x)
1153 { return __os << __x.base1() << " " << __x.base2(); }
1156 * Extracts the current state of a %xor_combine random number
1157 * generator engine @p __x from the input stream @p __is.
1159 * @param __is An input stream.
1160 * @param __x A %xor_combine random number generator engine.
1162 * @returns The input stream with the state of @p __x extracted or in
1165 template<typename _CharT, typename _Traits>
1166 friend std::basic_istream<_CharT, _Traits>&
1167 operator>>(std::basic_istream<_CharT, _Traits>& __is,
1169 { return __is >> __x._M_b1 >> __x._M_b2; }
1178 * A standard interface to a platform-specific non-deterministic random number
1179 * generator (if any are available).
1185 typedef unsigned int result_type;
1187 // constructors, destructors and member functions
1189 #ifdef _GLIBCXX_USE_RANDOM_TR1
1192 random_device(const std::string& __token = "/dev/urandom")
1194 if ((__token != "/dev/urandom" && __token != "/dev/random")
1195 || !_M_filebuf.open(__token.c_str(),
1196 std::ios_base::in | std::ios_base::binary))
1197 std::__throw_runtime_error(__N("random_device::"
1198 "random_device(const std::string&)"));
1202 { _M_filebuf.close(); }
1207 random_device(const std::string& __token = "mt19937")
1208 : _M_mt(_M_strtoul(__token)) { }
1211 static unsigned long
1212 _M_strtoul(const std::string& __str)
1214 unsigned long __ret = 5489UL;
1215 if (__str != "mt19937")
1217 const char* __nptr = __str.c_str();
1219 __ret = std::strtoul(__nptr, &__endptr, 0);
1220 if (*__nptr == '\0' || *__endptr != '\0')
1221 std::__throw_runtime_error(__N("random_device::_M_strtoul"
1222 "(const std::string&)"));
1233 { return std::numeric_limits<result_type>::min(); }
1237 { return std::numeric_limits<result_type>::max(); }
1246 #ifdef _GLIBCXX_USE_RANDOM_TR1
1248 _M_filebuf.sgetn(reinterpret_cast<char*>(&__ret), sizeof(result_type));
1256 random_device(const random_device&);
1257 void operator=(const random_device&);
1259 #ifdef _GLIBCXX_USE_RANDOM_TR1
1260 std::filebuf _M_filebuf;
1266 /* @} */ // group tr1_random_generators
1269 * @addtogroup tr1_random_distributions Random Number Distributions
1270 * @ingroup tr1_random
1275 * @addtogroup tr1_random_distributions_discrete Discrete Distributions
1276 * @ingroup tr1_random_distributions
1281 * @brief Uniform discrete distribution for random numbers.
1282 * A discrete random distribution on the range @f$[min, max]@f$ with equal
1283 * probability throughout the range.
1285 template<typename _IntType = int>
1288 __glibcxx_class_requires(_IntType, _IntegerConcept)
1291 /** The type of the parameters of the distribution. */
1292 typedef _IntType input_type;
1293 /** The type of the range of the distribution. */
1294 typedef _IntType result_type;
1298 * Constructs a uniform distribution object.
1301 uniform_int(_IntType __min = 0, _IntType __max = 9)
1302 : _M_min(__min), _M_max(__max)
1304 _GLIBCXX_DEBUG_ASSERT(_M_min <= _M_max);
1308 * Gets the inclusive lower bound of the distribution range.
1315 * Gets the inclusive upper bound of the distribution range.
1322 * Resets the distribution state.
1324 * Does nothing for the uniform integer distribution.
1330 * Gets a uniformly distributed random number in the range
1333 template<typename _UniformRandomNumberGenerator>
1335 operator()(_UniformRandomNumberGenerator& __urng)
1336 { return (__urng() % (_M_max - _M_min + 1)) + _M_min; }
1339 * Gets a uniform random number in the range @f$[0, n)@f$.
1341 * This function is aimed at use with std::random_shuffle.
1343 template<typename _UniformRandomNumberGenerator>
1345 operator()(_UniformRandomNumberGenerator& __urng, result_type __n)
1346 { return __urng() % __n; }
1349 * Inserts a %uniform_int random number distribution @p __x into the
1350 * output stream @p os.
1352 * @param __os An output stream.
1353 * @param __x A %uniform_int random number distribution.
1355 * @returns The output stream with the state of @p __x inserted or in
1358 template<typename _CharT, typename _Traits>
1359 friend std::basic_ostream<_CharT, _Traits>&
1360 operator<<(std::basic_ostream<_CharT, _Traits>& __os,
1361 const uniform_int& __x)
1362 { return __os << __x.min() << " " << __x.max(); }
1365 * Extracts a %unform_int random number distribution
1366 * @p __u from the input stream @p __is.
1368 * @param __is An input stream.
1369 * @param __u A %uniform_int random number generator engine.
1371 * @returns The input stream with @p __u extracted or in an error state.
1373 template<typename _CharT, typename _Traits>
1374 friend std::basic_istream<_CharT, _Traits>&
1375 operator>>(std::basic_istream<_CharT, _Traits>& __is, uniform_int& __u)
1376 { return __is >> __u._M_min >> __u._M_max; }
1385 * @brief A Bernoulli random number distribution.
1387 * Generates a sequence of true and false values with likelihood @f$ p @f$
1388 * that true will come up and @f$ (1 - p) @f$ that false will appear.
1390 class bernoulli_distribution
1393 typedef int input_type;
1394 typedef bool result_type;
1398 * Constructs a Bernoulli distribution with likelihood @p p.
1400 * @param __p [IN] The likelihood of a true result being returned. Must
1401 * be in the interval @f$ [0, 1] @f$.
1404 bernoulli_distribution(double __p = 0.5)
1407 _GLIBCXX_DEBUG_ASSERT((_M_p >= 0.0) && (_M_p <= 1.0));
1411 * Gets the @p p parameter of the distribution.
1418 * Resets the distribution state.
1420 * Does nothing for a bernoulli distribution.
1426 * Gets the next value in the Bernoullian sequence.
1428 template<class UniformRandomNumberGenerator>
1430 operator()(UniformRandomNumberGenerator& __urng)
1432 if (__urng() < _M_p)
1438 * Inserts a %bernoulli_distribution random number distribution
1439 * @p __x into the output stream @p __os.
1441 * @param __os An output stream.
1442 * @param __x A %bernoulli_distribution random number distribution.
1444 * @returns The output stream with the state of @p __x inserted or in
1447 template<typename _CharT, typename _Traits>
1448 friend std::basic_ostream<_CharT, _Traits>&
1449 operator<<(std::basic_ostream<_CharT, _Traits>& __os,
1450 const bernoulli_distribution& __x)
1451 { return __os << __x.p(); }
1454 * Extracts a %bernoulli_distribution random number distribution
1455 * @p __u from the input stream @p __is.
1457 * @param __is An input stream.
1458 * @param __u A %bernoulli_distribution random number generator engine.
1460 * @returns The input stream with @p __u extracted or in an error state.
1462 template<typename _CharT, typename _Traits>
1463 friend std::basic_istream<_CharT, _Traits>&
1464 operator>>(std::basic_istream<_CharT, _Traits>& __is,
1465 bernoulli_distribution& __u)
1466 { return __is >> __u._M_p; }
1474 * @brief A discrete geometric random number distribution.
1476 * The formula for the geometric probability mass function is
1477 * @f$ p(i) = (1 - p)p^{i-1} @f$ where @f$ p @f$ is the parameter of the
1480 template<typename _IntType = int, typename _RealType = double>
1481 class geometric_distribution
1485 typedef _RealType input_type;
1486 typedef _IntType result_type;
1488 // constructors and member function
1491 geometric_distribution(const _RealType& __p = _RealType(0.5))
1492 : _M_p(__p), _M_log_p(std::log(_M_p))
1494 _GLIBCXX_DEBUG_ASSERT((_M_p >= 0.0) && (_M_p <= 1.0));
1498 * Gets the distribution parameter @p p.
1507 template<class _UniformRandomNumberGenerator>
1509 operator()(_UniformRandomNumberGenerator& __urng)
1510 { return result_type(std::ceil(std::log(__urng()) / _M_log_p)); }
1513 * Inserts a %geometric_distribution random number distribution
1514 * @p __x into the output stream @p __os.
1516 * @param __os An output stream.
1517 * @param __x A %geometric_distribution random number distribution.
1519 * @returns The output stream with the state of @p __x inserted or in
1522 template<typename _CharT, typename _Traits>
1523 friend std::basic_ostream<_CharT, _Traits>&
1524 operator<<(std::basic_ostream<_CharT, _Traits>& __os,
1525 const geometric_distribution& __x)
1526 { return __os << __x.p(); }
1529 * Extracts a %geometric_distribution random number distribution
1530 * @p __u from the input stream @p __is.
1532 * @param __is An input stream.
1533 * @param __u A %geometric_distribution random number generator engine.
1535 * @returns The input stream with @p __u extracted or in an error state.
1537 template<typename _CharT, typename _Traits>
1538 friend std::basic_istream<_CharT, _Traits>&
1539 operator>>(std::basic_istream<_CharT, _Traits>& __is,
1540 geometric_distribution& __u)
1543 __u._M_log_p = std::log(__u._M_p);
1552 /* @} */ // group tr1_random_distributions_discrete
1555 * @addtogroup tr1_random_distributions_continuous Continuous Distributions
1556 * @ingroup tr1_random_distributions
1561 * @brief Uniform continuous distribution for random numbers.
1563 * A continuous random distribution on the range [min, max) with equal
1564 * probability throughout the range. The URNG should be real-valued and
1565 * deliver number in the range [0, 1).
1567 template<typename _RealType = double>
1572 typedef _RealType input_type;
1573 typedef _RealType result_type;
1577 * Constructs a uniform_real object.
1579 * @param __min [IN] The lower bound of the distribution.
1580 * @param __max [IN] The upper bound of the distribution.
1583 uniform_real(_RealType __min = _RealType(0),
1584 _RealType __max = _RealType(1))
1585 : _M_min(__min), _M_max(__max)
1587 _GLIBCXX_DEBUG_ASSERT(_M_min <= _M_max);
1601 template<class _UniformRandomNumberGenerator>
1603 operator()(_UniformRandomNumberGenerator& __urng)
1604 { return (__urng() * (_M_max - _M_min)) + _M_min; }
1607 * Inserts a %uniform_real random number distribution @p __x into the
1608 * output stream @p __os.
1610 * @param __os An output stream.
1611 * @param __x A %uniform_real random number distribution.
1613 * @returns The output stream with the state of @p __x inserted or in
1616 template<typename _CharT, typename _Traits>
1617 friend std::basic_ostream<_CharT, _Traits>&
1618 operator<<(std::basic_ostream<_CharT, _Traits>& __os,
1619 const uniform_real& __x)
1620 { return __os << __x.min() << " " << __x.max(); }
1623 * Extracts a %unform_real random number distribution
1624 * @p __u from the input stream @p __is.
1626 * @param __is An input stream.
1627 * @param __u A %uniform_real random number generator engine.
1629 * @returns The input stream with @p __u extracted or in an error state.
1631 template<typename _CharT, typename _Traits>
1632 friend std::basic_istream<_CharT, _Traits>&
1633 operator>>(std::basic_istream<_CharT, _Traits>& __is,
1635 { return __is >> __u._M_min >> __u._M_max; }
1644 * @brief An exponential continuous distribution for random numbers.
1646 * The formula for the exponential probability mass function is
1647 * @f$ p(x) = \lambda e^{-\lambda x} @f$.
1649 * <table border=1 cellpadding=10 cellspacing=0>
1650 * <caption align=top>Distribution Statistics</caption>
1651 * <tr><td>Mean</td><td>@f$ \frac{1}{\lambda} @f$</td></tr>
1652 * <tr><td>Median</td><td>@f$ \frac{\ln 2}{\lambda} @f$</td></tr>
1653 * <tr><td>Mode</td><td>@f$ zero @f$</td></tr>
1654 * <tr><td>Range</td><td>@f$[0, \infty]@f$</td></tr>
1655 * <tr><td>Standard Deviation</td><td>@f$ \frac{1}{\lambda} @f$</td></tr>
1658 template<typename _RealType = double>
1659 class exponential_distribution
1663 typedef _RealType input_type;
1664 typedef _RealType result_type;
1668 * Constructs an exponential distribution with inverse scale parameter
1672 exponential_distribution(const result_type& __lambda = result_type(1))
1673 : _M_lambda(__lambda)
1675 _GLIBCXX_DEBUG_ASSERT(_M_lambda > 0);
1679 * Gets the inverse scale parameter of the distribution.
1683 { return _M_lambda; }
1686 * Resets the distribution.
1688 * Has no effect on exponential distributions.
1693 template<class _UniformRandomNumberGenerator>
1695 operator()(_UniformRandomNumberGenerator& __urng)
1696 { return -std::log(__urng()) / _M_lambda; }
1699 * Inserts a %exponential_distribution random number distribution
1700 * @p __x into the output stream @p __os.
1702 * @param __os An output stream.
1703 * @param __x A %exponential_distribution random number distribution.
1705 * @returns The output stream with the state of @p __x inserted or in
1708 template<typename _CharT, typename _Traits>
1709 friend std::basic_ostream<_CharT, _Traits>&
1710 operator<<(std::basic_ostream<_CharT, _Traits>& __os,
1711 const exponential_distribution& __x)
1712 { return __os << __x.lambda(); }
1715 * Extracts a %exponential_distribution random number distribution
1716 * @p __u from the input stream @p __is.
1718 * @param __is An input stream.
1719 * @param __u A %exponential_distribution random number generator engine.
1721 * @returns The input stream with @p __u extracted or in an error state.
1723 template<typename _CharT, typename _Traits>
1724 friend std::basic_istream<_CharT, _Traits>&
1725 operator>>(std::basic_istream<_CharT, _Traits>& __is,
1726 exponential_distribution& __u)
1727 { return __is >> __u._M_lambda; }
1730 result_type _M_lambda;
1735 * @brief A normal continuous distribution for random numbers.
1737 * The formula for the normal probability mass function is
1738 * @f$ p(x) = \frac{1}{\sigma \sqrt{2 \pi}}
1739 * e^{- \frac{{x - mean}^ {2}}{2 \sigma ^ {2}} } @f$.
1741 template<typename _RealType = double>
1742 class normal_distribution
1746 typedef _RealType input_type;
1747 typedef _RealType result_type;
1751 * Constructs a normal distribution with parameters @f$ mean @f$ and
1755 normal_distribution(const result_type& __mean = result_type(0),
1756 const result_type& __sigma = result_type(1))
1757 : _M_mean(__mean), _M_sigma(__sigma), _M_saved_available(false)
1759 _GLIBCXX_DEBUG_ASSERT(_M_sigma > 0);
1763 * Gets the mean of the distribution.
1770 * Gets the @f$ \sigma @f$ of the distribution.
1774 { return _M_sigma; }
1777 * Resets the distribution.
1781 { _M_saved_available = false; }
1783 template<class _UniformRandomNumberGenerator>
1785 operator()(_UniformRandomNumberGenerator& __urng);
1788 * Inserts a %normal_distribution random number distribution
1789 * @p __x into the output stream @p __os.
1791 * @param __os An output stream.
1792 * @param __x A %normal_distribution random number distribution.
1794 * @returns The output stream with the state of @p __x inserted or in
1797 template<typename _CharT, typename _Traits>
1798 friend std::basic_ostream<_CharT, _Traits>&
1799 operator<<(std::basic_ostream<_CharT, _Traits>& __os,
1800 const normal_distribution& __x)
1802 return __os << __x.mean() << " " << __x.sigma()
1803 << " " << __x._M_saved << " " << __x._M_saved_available;
1807 * Extracts a %normal_distribution random number distribution
1808 * @p __u from the input stream @p __is.
1810 * @param __is An input stream.
1811 * @param __u A %normal_distribution random number generator engine.
1813 * @returns The input stream with @p __u extracted or in an error state.
1815 template<typename _CharT, typename _Traits>
1816 friend std::basic_istream<_CharT, _Traits>&
1817 operator>>(std::basic_istream<_CharT, _Traits>& __is,
1818 normal_distribution& __u)
1820 return __is >> __u._M_mean >> __u._M_sigma
1821 >> __u._M_saved >> __u._M_saved_available;
1825 result_type _M_mean;
1826 result_type _M_sigma;
1827 result_type _M_saved;
1828 bool _M_saved_available;
1831 /* @} */ // group tr1_random_distributions_continuous
1832 /* @} */ // group tr1_random_distributions
1833 /* @} */ // group tr1_random
1835 _GLIBCXX_END_NAMESPACE
1838 #include <tr1/random.tcc>
1840 #endif // _STD_TR1_RANDOM