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// -*- C++ -*- |
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|
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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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|
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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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|
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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_shuffle.h |
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* @brief Parallel implementation of std::random_shuffle(). |
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* This file is a GNU parallel extension to the Standard C++ Library. |
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*/ |
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|
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// Written by Johannes Singler. |
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|
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#ifndef _GLIBCXX_PARALLEL_RANDOM_SHUFFLE_H |
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#define _GLIBCXX_PARALLEL_RANDOM_SHUFFLE_H 1 |
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|
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#include <limits> |
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#include <bits/stl_numeric.h> |
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#include <parallel/parallel.h> |
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#include <parallel/random_number.h> |
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|
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namespace __gnu_parallel |
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{ |
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/** @brief Type to hold the index of a bin. |
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* |
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* Since many variables of this type are allocated, it should be |
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* chosen as small as possible. |
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*/ |
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typedef unsigned short _BinIndex; |
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|
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/** @brief Data known to every thread participating in |
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__gnu_parallel::__parallel_random_shuffle(). */ |
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template<typename _RAIter> |
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struct _DRandomShufflingGlobalData |
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{ |
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typedef std::iterator_traits<_RAIter> _TraitsType; |
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typedef typename _TraitsType::value_type _ValueType; |
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typedef typename _TraitsType::difference_type _DifferenceType; |
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|
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/** @brief Begin iterator of the __source. */ |
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_RAIter& _M_source; |
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|
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/** @brief Temporary arrays for each thread. */ |
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_ValueType** _M_temporaries; |
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|
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/** @brief Two-dimensional array to hold the thread-bin distribution. |
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* |
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* Dimensions (_M_num_threads + 1) __x (_M_num_bins + 1). */ |
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_DifferenceType** _M_dist; |
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|
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/** @brief Start indexes of the threads' __chunks. */ |
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_DifferenceType* _M_starts; |
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|
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/** @brief Number of the thread that will further process the |
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corresponding bin. */ |
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_ThreadIndex* _M_bin_proc; |
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|
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/** @brief Number of bins to distribute to. */ |
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int _M_num_bins; |
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|
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/** @brief Number of bits needed to address the bins. */ |
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int _M_num_bits; |
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|
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/** @brief Constructor. */ |
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_DRandomShufflingGlobalData(_RAIter& __source) |
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: _M_source(__source) { } |
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}; |
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|
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/** @brief Local data for a thread participating in |
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__gnu_parallel::__parallel_random_shuffle(). |
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*/ |
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template<typename _RAIter, typename _RandomNumberGenerator> |
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struct _DRSSorterPU |
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{ |
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/** @brief Number of threads participating in total. */ |
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int _M_num_threads; |
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|
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/** @brief Begin index for bins taken care of by this thread. */ |
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_BinIndex _M_bins_begin; |
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|
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/** @brief End index for bins taken care of by this thread. */ |
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_BinIndex __bins_end; |
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|
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/** @brief Random _M_seed for this thread. */ |
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uint32_t _M_seed; |
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|
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/** @brief Pointer to global data. */ |
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_DRandomShufflingGlobalData<_RAIter>* _M_sd; |
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}; |
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|
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/** @brief Generate a random number in @c [0,2^__logp). |
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* @param __logp Logarithm (basis 2) of the upper range __bound. |
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* @param __rng Random number generator to use. |
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*/ |
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template<typename _RandomNumberGenerator> |
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inline int |
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__random_number_pow2(int __logp, _RandomNumberGenerator& __rng) |
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{ return __rng.__genrand_bits(__logp); } |
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|
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/** @brief Random shuffle code executed by each thread. |
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* @param __pus Array of thread-local data records. */ |
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template<typename _RAIter, typename _RandomNumberGenerator> |
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void |
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__parallel_random_shuffle_drs_pu(_DRSSorterPU<_RAIter, |
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_RandomNumberGenerator>* __pus) |
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{ |
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typedef std::iterator_traits<_RAIter> _TraitsType; |
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typedef typename _TraitsType::value_type _ValueType; |
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typedef typename _TraitsType::difference_type _DifferenceType; |
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|
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_ThreadIndex __iam = omp_get_thread_num(); |
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_DRSSorterPU<_RAIter, _RandomNumberGenerator>* __d = &__pus[__iam]; |
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_DRandomShufflingGlobalData<_RAIter>* __sd = __d->_M_sd; |
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|
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// Indexing: _M_dist[bin][processor] |
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_DifferenceType __length = (__sd->_M_starts[__iam + 1] |
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- __sd->_M_starts[__iam]); |
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_BinIndex* __oracles = new _BinIndex[__length]; |
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_DifferenceType* __dist = new _DifferenceType[__sd->_M_num_bins + 1]; |
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_BinIndex* __bin_proc = new _BinIndex[__sd->_M_num_bins]; |
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_ValueType** __temporaries = new _ValueType*[__d->_M_num_threads]; |
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|
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// Compute oracles and count appearances. |
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for (_BinIndex __b = 0; __b < __sd->_M_num_bins + 1; ++__b) |
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__dist[__b] = 0; |
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int __num_bits = __sd->_M_num_bits; |
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|
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_RandomNumber __rng(__d->_M_seed); |
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|
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// First main loop. |
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for (_DifferenceType __i = 0; __i < __length; ++__i) |
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{ |
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_BinIndex __oracle = __random_number_pow2(__num_bits, __rng); |
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__oracles[__i] = __oracle; |
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|
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// To allow prefix (partial) sum. |
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++(__dist[__oracle + 1]); |
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} |
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|
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for (_BinIndex __b = 0; __b < __sd->_M_num_bins + 1; ++__b) |
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__sd->_M_dist[__b][__iam + 1] = __dist[__b]; |
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|
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# pragma omp barrier |
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|
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# pragma omp single |
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{ |
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// Sum up bins, __sd->_M_dist[__s + 1][__d->_M_num_threads] now |
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// contains the total number of items in bin __s |
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for (_BinIndex __s = 0; __s < __sd->_M_num_bins; ++__s) |
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__gnu_sequential::partial_sum(__sd->_M_dist[__s + 1], |
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__sd->_M_dist[__s + 1] |
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+ __d->_M_num_threads + 1, |
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__sd->_M_dist[__s + 1]); |
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} |
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|
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# pragma omp barrier |
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|
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_SequenceIndex __offset = 0, __global_offset = 0; |
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for (_BinIndex __s = 0; __s < __d->_M_bins_begin; ++__s) |
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__global_offset += __sd->_M_dist[__s + 1][__d->_M_num_threads]; |
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|
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# pragma omp barrier |
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|
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for (_BinIndex __s = __d->_M_bins_begin; __s < __d->__bins_end; ++__s) |
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{ |
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for (int __t = 0; __t < __d->_M_num_threads + 1; ++__t) |
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__sd->_M_dist[__s + 1][__t] += __offset; |
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__offset = __sd->_M_dist[__s + 1][__d->_M_num_threads]; |
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} |
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|
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__sd->_M_temporaries[__iam] = static_cast<_ValueType*> |
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(::operator new(sizeof(_ValueType) * __offset)); |
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|
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# pragma omp barrier |
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|
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// Draw local copies to avoid false sharing. |
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for (_BinIndex __b = 0; __b < __sd->_M_num_bins + 1; ++__b) |
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__dist[__b] = __sd->_M_dist[__b][__iam]; |
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for (_BinIndex __b = 0; __b < __sd->_M_num_bins; ++__b) |
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__bin_proc[__b] = __sd->_M_bin_proc[__b]; |
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for (_ThreadIndex __t = 0; __t < __d->_M_num_threads; ++__t) |
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__temporaries[__t] = __sd->_M_temporaries[__t]; |
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|
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_RAIter __source = __sd->_M_source; |
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_DifferenceType __start = __sd->_M_starts[__iam]; |
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|
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// Distribute according to oracles, second main loop. |
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for (_DifferenceType __i = 0; __i < __length; ++__i) |
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{ |
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_BinIndex __target_bin = __oracles[__i]; |
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_ThreadIndex __target_p = __bin_proc[__target_bin]; |
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|
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// Last column [__d->_M_num_threads] stays unchanged. |
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::new(&(__temporaries[__target_p][__dist[__target_bin + 1]++])) |
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_ValueType(*(__source + __i + __start)); |
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} |
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|
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delete[] __oracles; |
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delete[] __dist; |
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delete[] __bin_proc; |
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delete[] __temporaries; |
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|
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# pragma omp barrier |
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|
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// Shuffle bins internally. |
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for (_BinIndex __b = __d->_M_bins_begin; __b < __d->__bins_end; ++__b) |
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{ |
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_ValueType* __begin = |
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(__sd->_M_temporaries[__iam] |
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+ (__b == __d->_M_bins_begin |
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? 0 : __sd->_M_dist[__b][__d->_M_num_threads])), |
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*__end = (__sd->_M_temporaries[__iam] |
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+ __sd->_M_dist[__b + 1][__d->_M_num_threads]); |
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|
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__sequential_random_shuffle(__begin, __end, __rng); |
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std::copy(__begin, __end, __sd->_M_source + __global_offset |
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+ (__b == __d->_M_bins_begin |
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? 0 : __sd->_M_dist[__b][__d->_M_num_threads])); |
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} |
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|
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for (_SequenceIndex __i = 0; __i < __offset; ++__i) |
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__sd->_M_temporaries[__iam][__i].~_ValueType(); |
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::operator delete(__sd->_M_temporaries[__iam]); |
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} |
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|
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/** @brief Round up to the next greater power of 2. |
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* @param __x _Integer to round up */ |
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template<typename _Tp> |
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_Tp |
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__round_up_to_pow2(_Tp __x) |
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{ |
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if (__x <= 1) |
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return 1; |
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else |
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return (_Tp)1 << (__rd_log2(__x - 1) + 1); |
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} |
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|
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/** @brief Main parallel random shuffle step. |
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* @param __begin Begin iterator of sequence. |
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* @param __end End iterator of sequence. |
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* @param __n Length of sequence. |
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* @param __num_threads Number of threads to use. |
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* @param __rng Random number generator to use. |
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*/ |
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template<typename _RAIter, typename _RandomNumberGenerator> |
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void |
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__parallel_random_shuffle_drs(_RAIter __begin, _RAIter __end, |
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typename std::iterator_traits |
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<_RAIter>::difference_type __n, |
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_ThreadIndex __num_threads, |
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_RandomNumberGenerator& __rng) |
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{ |
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typedef std::iterator_traits<_RAIter> _TraitsType; |
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typedef typename _TraitsType::value_type _ValueType; |
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typedef typename _TraitsType::difference_type _DifferenceType; |
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|
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_GLIBCXX_CALL(__n) |
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|
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const _Settings& __s = _Settings::get(); |
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|
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if (__num_threads > __n) |
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__num_threads = static_cast<_ThreadIndex>(__n); |
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|
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_BinIndex __num_bins, __num_bins_cache; |
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|
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#if _GLIBCXX_RANDOM_SHUFFLE_CONSIDER_L1 |
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// Try the L1 cache first. |
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|
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// Must fit into L1. |
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__num_bins_cache = |
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std::max<_DifferenceType>(1, __n / (__s.L1_cache_size_lb |
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/ sizeof(_ValueType))); |
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__num_bins_cache = __round_up_to_pow2(__num_bins_cache); |
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|
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// No more buckets than TLB entries, power of 2 |
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// Power of 2 and at least one element per bin, at most the TLB size. |
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__num_bins = std::min<_DifferenceType>(__n, __num_bins_cache); |
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|
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#if _GLIBCXX_RANDOM_SHUFFLE_CONSIDER_TLB |
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// 2 TLB entries needed per bin. |
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__num_bins = std::min<_DifferenceType>(__s.TLB_size / 2, __num_bins); |
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#endif |
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__num_bins = __round_up_to_pow2(__num_bins); |
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|
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if (__num_bins < __num_bins_cache) |
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{ |
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#endif |
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// Now try the L2 cache |
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// Must fit into L2 |
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__num_bins_cache = static_cast<_BinIndex> |
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(std::max<_DifferenceType>(1, __n / (__s.L2_cache_size |
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/ sizeof(_ValueType)))); |
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__num_bins_cache = __round_up_to_pow2(__num_bins_cache); |
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|
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// No more buckets than TLB entries, power of 2. |
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__num_bins = static_cast<_BinIndex> |
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(std::min(__n, static_cast<_DifferenceType>(__num_bins_cache))); |
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// Power of 2 and at least one element per bin, at most the TLB size. |
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#if _GLIBCXX_RANDOM_SHUFFLE_CONSIDER_TLB |
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// 2 TLB entries needed per bin. |
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__num_bins = std::min(static_cast<_DifferenceType>(__s.TLB_size / 2), |
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__num_bins); |
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#endif |
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__num_bins = __round_up_to_pow2(__num_bins); |
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#if _GLIBCXX_RANDOM_SHUFFLE_CONSIDER_L1 |
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} |
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#endif |
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|
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__num_bins = __round_up_to_pow2( |
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std::max<_BinIndex>(__num_threads, __num_bins)); |
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|
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if (__num_threads <= 1) |
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{ |
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_RandomNumber __derived_rng( |
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__rng(std::numeric_limits<uint32_t>::max())); |
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__sequential_random_shuffle(__begin, __end, __derived_rng); |
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return; |
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} |
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|
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_DRandomShufflingGlobalData<_RAIter> __sd(__begin); |
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_DRSSorterPU<_RAIter, _RandomNumber >* __pus; |
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_DifferenceType* __starts; |
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|
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# pragma omp parallel num_threads(__num_threads) |
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{ |
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_ThreadIndex __num_threads = omp_get_num_threads(); |
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# pragma omp single |
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{ |
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__pus = new _DRSSorterPU<_RAIter, _RandomNumber>[__num_threads]; |
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|
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__sd._M_temporaries = new _ValueType*[__num_threads]; |
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__sd._M_dist = new _DifferenceType*[__num_bins + 1]; |
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__sd._M_bin_proc = new _ThreadIndex[__num_bins]; |
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for (_BinIndex __b = 0; __b < __num_bins + 1; ++__b) |
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__sd._M_dist[__b] = new _DifferenceType[__num_threads + 1]; |
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for (_BinIndex __b = 0; __b < (__num_bins + 1); ++__b) |
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{ |
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__sd._M_dist[0][0] = 0; |
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__sd._M_dist[__b][0] = 0; |
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} |
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__starts = __sd._M_starts = new _DifferenceType[__num_threads + 1]; |
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int __bin_cursor = 0; |
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__sd._M_num_bins = __num_bins; |
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__sd._M_num_bits = __rd_log2(__num_bins); |
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|
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_DifferenceType __chunk_length = __n / __num_threads, |
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__split = __n % __num_threads, |
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__start = 0; |
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_DifferenceType __bin_chunk_length = __num_bins / __num_threads, |
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__bin_split = __num_bins % __num_threads; |
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for (_ThreadIndex __i = 0; __i < __num_threads; ++__i) |
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{ |
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__starts[__i] = __start; |
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__start += (__i < __split |
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? (__chunk_length + 1) : __chunk_length); |
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int __j = __pus[__i]._M_bins_begin = __bin_cursor; |
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|
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// Range of bins for this processor. |
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__bin_cursor += (__i < __bin_split |
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? (__bin_chunk_length + 1) |
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: __bin_chunk_length); |
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__pus[__i].__bins_end = __bin_cursor; |
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for (; __j < __bin_cursor; ++__j) |
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__sd._M_bin_proc[__j] = __i; |
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__pus[__i]._M_num_threads = __num_threads; |
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__pus[__i]._M_seed = __rng(std::numeric_limits<uint32_t>::max()); |
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__pus[__i]._M_sd = &__sd; |
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} |
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__starts[__num_threads] = __start; |
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} //single |
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// Now shuffle in parallel. |
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__parallel_random_shuffle_drs_pu(__pus); |
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} // parallel |
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|
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delete[] __starts; |
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delete[] __sd._M_bin_proc; |
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for (int __s = 0; __s < (__num_bins + 1); ++__s) |
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delete[] __sd._M_dist[__s]; |
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delete[] __sd._M_dist; |
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delete[] __sd._M_temporaries; |
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|
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delete[] __pus; |
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} |
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|
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/** @brief Sequential cache-efficient random shuffle. |
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* @param __begin Begin iterator of sequence. |
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* @param __end End iterator of sequence. |
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* @param __rng Random number generator to use. |
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*/ |
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template<typename _RAIter, typename _RandomNumberGenerator> |
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void |
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__sequential_random_shuffle(_RAIter __begin, _RAIter __end, |
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_RandomNumberGenerator& __rng) |
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{ |
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typedef std::iterator_traits<_RAIter> _TraitsType; |
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typedef typename _TraitsType::value_type _ValueType; |
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typedef typename _TraitsType::difference_type _DifferenceType; |
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|
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_DifferenceType __n = __end - __begin; |
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const _Settings& __s = _Settings::get(); |
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|
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_BinIndex __num_bins, __num_bins_cache; |
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|
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#if _GLIBCXX_RANDOM_SHUFFLE_CONSIDER_L1 |
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// Try the L1 cache first, must fit into L1. |
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__num_bins_cache = std::max<_DifferenceType> |
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(1, __n / (__s.L1_cache_size_lb / sizeof(_ValueType))); |
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__num_bins_cache = __round_up_to_pow2(__num_bins_cache); |
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|
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// No more buckets than TLB entries, power of 2 |
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// Power of 2 and at least one element per bin, at most the TLB size |
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__num_bins = std::min(__n, (_DifferenceType)__num_bins_cache); |
| 431 |
#if _GLIBCXX_RANDOM_SHUFFLE_CONSIDER_TLB |
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// 2 TLB entries needed per bin |
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__num_bins = std::min((_DifferenceType)__s.TLB_size / 2, __num_bins); |
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#endif |
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__num_bins = __round_up_to_pow2(__num_bins); |
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|
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if (__num_bins < __num_bins_cache) |
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{ |
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#endif |
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// Now try the L2 cache, must fit into L2. |
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__num_bins_cache = static_cast<_BinIndex> |
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(std::max<_DifferenceType>(1, __n / (__s.L2_cache_size |
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/ sizeof(_ValueType)))); |
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__num_bins_cache = __round_up_to_pow2(__num_bins_cache); |
| 445 |
|
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// No more buckets than TLB entries, power of 2 |
| 447 |
// Power of 2 and at least one element per bin, at most the TLB size. |
| 448 |
__num_bins = static_cast<_BinIndex> |
| 449 |
(std::min(__n, static_cast<_DifferenceType>(__num_bins_cache))); |
| 450 |
|
| 451 |
#if _GLIBCXX_RANDOM_SHUFFLE_CONSIDER_TLB |
| 452 |
// 2 TLB entries needed per bin |
| 453 |
__num_bins = std::min<_DifferenceType>(__s.TLB_size / 2, __num_bins); |
| 454 |
#endif |
| 455 |
__num_bins = __round_up_to_pow2(__num_bins); |
| 456 |
#if _GLIBCXX_RANDOM_SHUFFLE_CONSIDER_L1 |
| 457 |
} |
| 458 |
#endif |
| 459 |
|
| 460 |
int __num_bits = __rd_log2(__num_bins); |
| 461 |
|
| 462 |
if (__num_bins > 1) |
| 463 |
{ |
| 464 |
_ValueType* __target = |
| 465 |
static_cast<_ValueType*>(::operator new(sizeof(_ValueType) * __n)); |
| 466 |
_BinIndex* __oracles = new _BinIndex[__n]; |
| 467 |
_DifferenceType* __dist0 = new _DifferenceType[__num_bins + 1], |
| 468 |
* __dist1 = new _DifferenceType[__num_bins + 1]; |
| 469 |
|
| 470 |
for (int __b = 0; __b < __num_bins + 1; ++__b) |
| 471 |
__dist0[__b] = 0; |
| 472 |
|
| 473 |
_RandomNumber __bitrng(__rng(0xFFFFFFFF)); |
| 474 |
|
| 475 |
for (_DifferenceType __i = 0; __i < __n; ++__i) |
| 476 |
{ |
| 477 |
_BinIndex __oracle = __random_number_pow2(__num_bits, __bitrng); |
| 478 |
__oracles[__i] = __oracle; |
| 479 |
|
| 480 |
// To allow prefix (partial) sum. |
| 481 |
++(__dist0[__oracle + 1]); |
| 482 |
} |
| 483 |
|
| 484 |
// Sum up bins. |
| 485 |
__gnu_sequential::partial_sum(__dist0, __dist0 + __num_bins + 1, |
| 486 |
__dist0); |
| 487 |
|
| 488 |
for (int __b = 0; __b < __num_bins + 1; ++__b) |
| 489 |
__dist1[__b] = __dist0[__b]; |
| 490 |
|
| 491 |
// Distribute according to oracles. |
| 492 |
for (_DifferenceType __i = 0; __i < __n; ++__i) |
| 493 |
::new(&(__target[(__dist0[__oracles[__i]])++])) |
| 494 |
_ValueType(*(__begin + __i)); |
| 495 |
|
| 496 |
for (int __b = 0; __b < __num_bins; ++__b) |
| 497 |
__sequential_random_shuffle(__target + __dist1[__b], |
| 498 |
__target + __dist1[__b + 1], __rng); |
| 499 |
|
| 500 |
// Copy elements back. |
| 501 |
std::copy(__target, __target + __n, __begin); |
| 502 |
|
| 503 |
delete[] __dist0; |
| 504 |
delete[] __dist1; |
| 505 |
delete[] __oracles; |
| 506 |
|
| 507 |
for (_DifferenceType __i = 0; __i < __n; ++__i) |
| 508 |
__target[__i].~_ValueType(); |
| 509 |
::operator delete(__target); |
| 510 |
} |
| 511 |
else |
| 512 |
__gnu_sequential::random_shuffle(__begin, __end, __rng); |
| 513 |
} |
| 514 |
|
| 515 |
/** @brief Parallel random public call. |
| 516 |
* @param __begin Begin iterator of sequence. |
| 517 |
* @param __end End iterator of sequence. |
| 518 |
* @param __rng Random number generator to use. |
| 519 |
*/ |
| 520 |
template<typename _RAIter, typename _RandomNumberGenerator> |
| 521 |
inline void |
| 522 |
__parallel_random_shuffle(_RAIter __begin, _RAIter __end, |
| 523 |
_RandomNumberGenerator __rng = _RandomNumber()) |
| 524 |
{ |
| 525 |
typedef std::iterator_traits<_RAIter> _TraitsType; |
| 526 |
typedef typename _TraitsType::difference_type _DifferenceType; |
| 527 |
_DifferenceType __n = __end - __begin; |
| 528 |
__parallel_random_shuffle_drs(__begin, __end, __n, |
| 529 |
__get_max_threads(), __rng); |
| 530 |
} |
| 531 |
} |
| 532 |
|
| 533 |
#endif /* _GLIBCXX_PARALLEL_RANDOM_SHUFFLE_H */ |
