Edit: random_number.h
// -*- C++ -*- // Copyright (C) 2007-2018 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 */
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