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// -*- C++ -*- |
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// Copyright (C) 2007-2021 Free Software Foundation, Inc. |
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// |
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// This file is part of the GNU ISO C++ Library. This library is free |
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// software; you can redistribute it and/or modify it under the terms |
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// of the GNU General Public License as published by the Free Software |
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// Foundation; either version 3, or (at your option) any later |
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// version. |
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// This library is distributed in the hope that it will be useful, but |
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// WITHOUT ANY WARRANTY; without even the implied warranty of |
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU |
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// General Public License for more details. |
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|
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// Under Section 7 of GPL version 3, you are granted additional |
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// permissions described in the GCC Runtime Library Exception, version |
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// 3.1, as published by the Free Software Foundation. |
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// You should have received a copy of the GNU General Public License and |
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// a copy of the GCC Runtime Library Exception along with this program; |
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// see the files COPYING3 and COPYING.RUNTIME respectively. If not, see |
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// <http://www.gnu.org/licenses/>. |
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|
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/** @file parallel/random_number.h |
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* @brief Random number generator based on the Mersenne twister. |
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* This file is a GNU parallel extension to the Standard C++ Library. |
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*/ |
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// Written by Johannes Singler. |
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|
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#ifndef _GLIBCXX_PARALLEL_RANDOM_NUMBER_H |
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#define _GLIBCXX_PARALLEL_RANDOM_NUMBER_H 1 |
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|
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#include <parallel/types.h> |
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#include <tr1/random> |
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#include <limits> |
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|
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namespace __gnu_parallel |
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{ |
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/** @brief Random number generator, based on the Mersenne twister. */ |
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class _RandomNumber |
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{ |
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private: |
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std::tr1::mt19937 _M_mt; |
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uint64_t _M_supremum; |
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uint64_t _M_rand_sup; |
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double _M_supremum_reciprocal; |
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double _M_rand_sup_reciprocal; |
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|
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// Assumed to be twice as long as the usual random number. |
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uint64_t __cache; |
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|
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// Bit results. |
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int __bits_left; |
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|
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static uint32_t |
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__scale_down(uint64_t __x, |
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#if _GLIBCXX_SCALE_DOWN_FPU |
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uint64_t /*_M_supremum*/, double _M_supremum_reciprocal) |
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#else |
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uint64_t _M_supremum, double /*_M_supremum_reciprocal*/) |
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#endif |
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{ |
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#if _GLIBCXX_SCALE_DOWN_FPU |
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return uint32_t(__x * _M_supremum_reciprocal); |
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#else |
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return static_cast<uint32_t>(__x % _M_supremum); |
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#endif |
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} |
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|
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public: |
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/** @brief Default constructor. Seed with 0. */ |
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_RandomNumber() |
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: _M_mt(0), _M_supremum(0x100000000ULL), |
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_M_rand_sup(1ULL << std::numeric_limits<uint32_t>::digits), |
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_M_supremum_reciprocal(double(_M_supremum) / double(_M_rand_sup)), |
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_M_rand_sup_reciprocal(1.0 / double(_M_rand_sup)), |
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__cache(0), __bits_left(0) { } |
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|
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/** @brief Constructor. |
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* @param __seed Random __seed. |
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* @param _M_supremum Generate integer random numbers in the |
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* interval @c [0,_M_supremum). */ |
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_RandomNumber(uint32_t __seed, uint64_t _M_supremum = 0x100000000ULL) |
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: _M_mt(__seed), _M_supremum(_M_supremum), |
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_M_rand_sup(1ULL << std::numeric_limits<uint32_t>::digits), |
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_M_supremum_reciprocal(double(_M_supremum) / double(_M_rand_sup)), |
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_M_rand_sup_reciprocal(1.0 / double(_M_rand_sup)), |
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__cache(0), __bits_left(0) { } |
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|
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/** @brief Generate unsigned random 32-bit integer. */ |
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uint32_t |
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operator()() |
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{ return __scale_down(_M_mt(), _M_supremum, _M_supremum_reciprocal); } |
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|
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/** @brief Generate unsigned random 32-bit integer in the |
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interval @c [0,local_supremum). */ |
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uint32_t |
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operator()(uint64_t local_supremum) |
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{ |
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return __scale_down(_M_mt(), local_supremum, |
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double(local_supremum * _M_rand_sup_reciprocal)); |
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} |
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|
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/** @brief Generate a number of random bits, run-time parameter. |
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* @param __bits Number of bits to generate. */ |
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unsigned long |
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__genrand_bits(int __bits) |
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{ |
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unsigned long __res = __cache & ((1 << __bits) - 1); |
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__cache = __cache >> __bits; |
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__bits_left -= __bits; |
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if (__bits_left < 32) |
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{ |
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__cache |= ((uint64_t(_M_mt())) << __bits_left); |
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__bits_left += 32; |
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} |
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return __res; |
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} |
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}; |
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|
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} // namespace __gnu_parallel |
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|
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#endif /* _GLIBCXX_PARALLEL_RANDOM_NUMBER_H */ |
