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Diffstat (limited to 'libstdc++-v3/include/parallel/random_number.h')
| -rw-r--r-- | libstdc++-v3/include/parallel/random_number.h | 125 |
1 files changed, 125 insertions, 0 deletions
diff --git a/libstdc++-v3/include/parallel/random_number.h b/libstdc++-v3/include/parallel/random_number.h new file mode 100644 index 000000000..c39f15e12 --- /dev/null +++ b/libstdc++-v3/include/parallel/random_number.h @@ -0,0 +1,125 @@ +// -*- C++ -*- + +// Copyright (C) 2007, 2008, 2009 Free Software Foundation, Inc. +// +// This file is part of the GNU ISO C++ Library. This library is free +// software; you can redistribute it and/or modify it under the terms +// of the GNU General Public License as published by the Free Software +// Foundation; either version 3, or (at your option) any later +// version. + +// This library is distributed in the hope that it will be useful, but +// WITHOUT ANY WARRANTY; without even the implied warranty of +// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU +// General Public License for more details. + +// Under Section 7 of GPL version 3, you are granted additional +// permissions described in the GCC Runtime Library Exception, version +// 3.1, as published by the Free Software Foundation. + +// You should have received a copy of the GNU General Public License and +// a copy of the GCC Runtime Library Exception along with this program; +// see the files COPYING3 and COPYING.RUNTIME respectively. If not, see +// <http://www.gnu.org/licenses/>. + +/** @file parallel/random_number.h + * @brief Random number generator based on the Mersenne twister. + * This file is a GNU parallel extension to the Standard C++ Library. + */ + +// Written by Johannes Singler. + +#ifndef _GLIBCXX_PARALLEL_RANDOM_NUMBER_H +#define _GLIBCXX_PARALLEL_RANDOM_NUMBER_H 1 + +#include <parallel/types.h> +#include <tr1/random> +#include <limits> + +namespace __gnu_parallel +{ + /** @brief Random number generator, based on the Mersenne twister. */ + class _RandomNumber + { + private: + std::tr1::mt19937 _M_mt; + uint64_t _M_supremum; + uint64_t _M_rand_sup; + double _M_supremum_reciprocal; + double _M_rand_sup_reciprocal; + + // Assumed to be twice as long as the usual random number. + uint64_t __cache; + + // Bit results. + int __bits_left; + + static uint32_t + __scale_down(uint64_t __x, +#if _GLIBCXX_SCALE_DOWN_FPU + uint64_t /*_M_supremum*/, double _M_supremum_reciprocal) +#else + uint64_t _M_supremum, double /*_M_supremum_reciprocal*/) +#endif + { +#if _GLIBCXX_SCALE_DOWN_FPU + return uint32_t(__x * _M_supremum_reciprocal); +#else + return static_cast<uint32_t>(__x % _M_supremum); +#endif + } + + public: + /** @brief Default constructor. Seed with 0. */ + _RandomNumber() + : _M_mt(0), _M_supremum(0x100000000ULL), + _M_rand_sup(1ULL << std::numeric_limits<uint32_t>::digits), + _M_supremum_reciprocal(double(_M_supremum) / double(_M_rand_sup)), + _M_rand_sup_reciprocal(1.0 / double(_M_rand_sup)), + __cache(0), __bits_left(0) { } + + /** @brief Constructor. + * @param __seed Random __seed. + * @param _M_supremum Generate integer random numbers in the + * interval @c [0,_M_supremum). */ + _RandomNumber(uint32_t __seed, uint64_t _M_supremum = 0x100000000ULL) + : _M_mt(__seed), _M_supremum(_M_supremum), + _M_rand_sup(1ULL << std::numeric_limits<uint32_t>::digits), + _M_supremum_reciprocal(double(_M_supremum) / double(_M_rand_sup)), + _M_rand_sup_reciprocal(1.0 / double(_M_rand_sup)), + __cache(0), __bits_left(0) { } + + /** @brief Generate unsigned random 32-bit integer. */ + uint32_t + operator()() + { return __scale_down(_M_mt(), _M_supremum, _M_supremum_reciprocal); } + + /** @brief Generate unsigned random 32-bit integer in the + interval @c [0,local_supremum). */ + uint32_t + operator()(uint64_t local_supremum) + { + return __scale_down(_M_mt(), local_supremum, + double(local_supremum * _M_rand_sup_reciprocal)); + } + + /** @brief Generate a number of random bits, run-time parameter. + * @param bits Number of bits to generate. */ + unsigned long + __genrand_bits(int __bits) + { + unsigned long __res = __cache & ((1 << __bits) - 1); + __cache = __cache >> __bits; + __bits_left -= __bits; + if (__bits_left < 32) + { + __cache |= ((uint64_t(_M_mt())) << __bits_left); + __bits_left += 32; + } + return __res; + } +}; + +} // namespace __gnu_parallel + +#endif /* _GLIBCXX_PARALLEL_RANDOM_NUMBER_H */ |