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Diffstat (limited to 'libstdc++-v3/include/parallel/random_shuffle.h')
| -rw-r--r-- | libstdc++-v3/include/parallel/random_shuffle.h | 533 |
1 files changed, 533 insertions, 0 deletions
diff --git a/libstdc++-v3/include/parallel/random_shuffle.h b/libstdc++-v3/include/parallel/random_shuffle.h new file mode 100644 index 000000000..c3967c228 --- /dev/null +++ b/libstdc++-v3/include/parallel/random_shuffle.h @@ -0,0 +1,533 @@ +// -*- C++ -*- + +// Copyright (C) 2007, 2008, 2009, 2010, 2011 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_shuffle.h + * @brief Parallel implementation of std::random_shuffle(). + * This file is a GNU parallel extension to the Standard C++ Library. + */ + +// Written by Johannes Singler. + +#ifndef _GLIBCXX_PARALLEL_RANDOM_SHUFFLE_H +#define _GLIBCXX_PARALLEL_RANDOM_SHUFFLE_H 1 + +#include <limits> +#include <bits/stl_numeric.h> +#include <parallel/parallel.h> +#include <parallel/random_number.h> + +namespace __gnu_parallel +{ + /** @brief Type to hold the index of a bin. + * + * Since many variables of this type are allocated, it should be + * chosen as small as possible. + */ + typedef unsigned short _BinIndex; + + /** @brief Data known to every thread participating in + __gnu_parallel::__parallel_random_shuffle(). */ + template<typename _RAIter> + struct _DRandomShufflingGlobalData + { + typedef std::iterator_traits<_RAIter> _TraitsType; + typedef typename _TraitsType::value_type _ValueType; + typedef typename _TraitsType::difference_type _DifferenceType; + + /** @brief Begin iterator of the __source. */ + _RAIter& _M_source; + + /** @brief Temporary arrays for each thread. */ + _ValueType** _M_temporaries; + + /** @brief Two-dimensional array to hold the thread-bin distribution. + * + * Dimensions (_M_num_threads + 1) __x (_M_num_bins + 1). */ + _DifferenceType** _M_dist; + + /** @brief Start indexes of the threads' __chunks. */ + _DifferenceType* _M_starts; + + /** @brief Number of the thread that will further process the + corresponding bin. */ + _ThreadIndex* _M_bin_proc; + + /** @brief Number of bins to distribute to. */ + int _M_num_bins; + + /** @brief Number of bits needed to address the bins. */ + int _M_num_bits; + + /** @brief Constructor. */ + _DRandomShufflingGlobalData(_RAIter& __source) + : _M_source(__source) { } + }; + + /** @brief Local data for a thread participating in + __gnu_parallel::__parallel_random_shuffle(). + */ + template<typename _RAIter, typename _RandomNumberGenerator> + struct _DRSSorterPU + { + /** @brief Number of threads participating in total. */ + int _M_num_threads; + + /** @brief Begin index for bins taken care of by this thread. */ + _BinIndex _M_bins_begin; + + /** @brief End index for bins taken care of by this thread. */ + _BinIndex __bins_end; + + /** @brief Random _M_seed for this thread. */ + uint32_t _M_seed; + + /** @brief Pointer to global data. */ + _DRandomShufflingGlobalData<_RAIter>* _M_sd; + }; + + /** @brief Generate a random number in @c [0,2^__logp). + * @param __logp Logarithm (basis 2) of the upper range __bound. + * @param __rng Random number generator to use. + */ + template<typename _RandomNumberGenerator> + inline int + __random_number_pow2(int __logp, _RandomNumberGenerator& __rng) + { return __rng.__genrand_bits(__logp); } + + /** @brief Random shuffle code executed by each thread. + * @param __pus Array of thread-local data records. */ + template<typename _RAIter, typename _RandomNumberGenerator> + void + __parallel_random_shuffle_drs_pu(_DRSSorterPU<_RAIter, + _RandomNumberGenerator>* __pus) + { + typedef std::iterator_traits<_RAIter> _TraitsType; + typedef typename _TraitsType::value_type _ValueType; + typedef typename _TraitsType::difference_type _DifferenceType; + + _ThreadIndex __iam = omp_get_thread_num(); + _DRSSorterPU<_RAIter, _RandomNumberGenerator>* __d = &__pus[__iam]; + _DRandomShufflingGlobalData<_RAIter>* __sd = __d->_M_sd; + + // Indexing: _M_dist[bin][processor] + _DifferenceType __length = (__sd->_M_starts[__iam + 1] + - __sd->_M_starts[__iam]); + _BinIndex* __oracles = new _BinIndex[__length]; + _DifferenceType* __dist = new _DifferenceType[__sd->_M_num_bins + 1]; + _BinIndex* __bin_proc = new _BinIndex[__sd->_M_num_bins]; + _ValueType** __temporaries = new _ValueType*[__d->_M_num_threads]; + + // Compute oracles and count appearances. + for (_BinIndex __b = 0; __b < __sd->_M_num_bins + 1; ++__b) + __dist[__b] = 0; + int __num_bits = __sd->_M_num_bits; + + _RandomNumber __rng(__d->_M_seed); + + // First main loop. + for (_DifferenceType __i = 0; __i < __length; ++__i) + { + _BinIndex __oracle = __random_number_pow2(__num_bits, __rng); + __oracles[__i] = __oracle; + + // To allow prefix (partial) sum. + ++(__dist[__oracle + 1]); + } + + for (_BinIndex __b = 0; __b < __sd->_M_num_bins + 1; ++__b) + __sd->_M_dist[__b][__iam + 1] = __dist[__b]; + +# pragma omp barrier + +# pragma omp single + { + // Sum up bins, __sd->_M_dist[__s + 1][__d->_M_num_threads] now + // contains the total number of items in bin __s + for (_BinIndex __s = 0; __s < __sd->_M_num_bins; ++__s) + __gnu_sequential::partial_sum(__sd->_M_dist[__s + 1], + __sd->_M_dist[__s + 1] + + __d->_M_num_threads + 1, + __sd->_M_dist[__s + 1]); + } + +# pragma omp barrier + + _SequenceIndex __offset = 0, __global_offset = 0; + for (_BinIndex __s = 0; __s < __d->_M_bins_begin; ++__s) + __global_offset += __sd->_M_dist[__s + 1][__d->_M_num_threads]; + +# pragma omp barrier + + for (_BinIndex __s = __d->_M_bins_begin; __s < __d->__bins_end; ++__s) + { + for (int __t = 0; __t < __d->_M_num_threads + 1; ++__t) + __sd->_M_dist[__s + 1][__t] += __offset; + __offset = __sd->_M_dist[__s + 1][__d->_M_num_threads]; + } + + __sd->_M_temporaries[__iam] = static_cast<_ValueType*> + (::operator new(sizeof(_ValueType) * __offset)); + +# pragma omp barrier + + // Draw local copies to avoid false sharing. + for (_BinIndex __b = 0; __b < __sd->_M_num_bins + 1; ++__b) + __dist[__b] = __sd->_M_dist[__b][__iam]; + for (_BinIndex __b = 0; __b < __sd->_M_num_bins; ++__b) + __bin_proc[__b] = __sd->_M_bin_proc[__b]; + for (_ThreadIndex __t = 0; __t < __d->_M_num_threads; ++__t) + __temporaries[__t] = __sd->_M_temporaries[__t]; + + _RAIter __source = __sd->_M_source; + _DifferenceType __start = __sd->_M_starts[__iam]; + + // Distribute according to oracles, second main loop. + for (_DifferenceType __i = 0; __i < __length; ++__i) + { + _BinIndex __target_bin = __oracles[__i]; + _ThreadIndex __target_p = __bin_proc[__target_bin]; + + // Last column [__d->_M_num_threads] stays unchanged. + ::new(&(__temporaries[__target_p][__dist[__target_bin + 1]++])) + _ValueType(*(__source + __i + __start)); + } + + delete[] __oracles; + delete[] __dist; + delete[] __bin_proc; + delete[] __temporaries; + +# pragma omp barrier + + // Shuffle bins internally. + for (_BinIndex __b = __d->_M_bins_begin; __b < __d->__bins_end; ++__b) + { + _ValueType* __begin = + (__sd->_M_temporaries[__iam] + + (__b == __d->_M_bins_begin + ? 0 : __sd->_M_dist[__b][__d->_M_num_threads])), + *__end = (__sd->_M_temporaries[__iam] + + __sd->_M_dist[__b + 1][__d->_M_num_threads]); + + __sequential_random_shuffle(__begin, __end, __rng); + std::copy(__begin, __end, __sd->_M_source + __global_offset + + (__b == __d->_M_bins_begin + ? 0 : __sd->_M_dist[__b][__d->_M_num_threads])); + } + + for (_SequenceIndex __i = 0; __i < __offset; ++__i) + __sd->_M_temporaries[__iam][__i].~_ValueType(); + ::operator delete(__sd->_M_temporaries[__iam]); + } + + /** @brief Round up to the next greater power of 2. + * @param __x _Integer to round up */ + template<typename _Tp> + _Tp + __round_up_to_pow2(_Tp __x) + { + if (__x <= 1) + return 1; + else + return (_Tp)1 << (__rd_log2(__x - 1) + 1); + } + + /** @brief Main parallel random shuffle step. + * @param __begin Begin iterator of sequence. + * @param __end End iterator of sequence. + * @param __n Length of sequence. + * @param __num_threads Number of threads to use. + * @param __rng Random number generator to use. + */ + template<typename _RAIter, typename _RandomNumberGenerator> + void + __parallel_random_shuffle_drs(_RAIter __begin, _RAIter __end, + typename std::iterator_traits + <_RAIter>::difference_type __n, + _ThreadIndex __num_threads, + _RandomNumberGenerator& __rng) + { + typedef std::iterator_traits<_RAIter> _TraitsType; + typedef typename _TraitsType::value_type _ValueType; + typedef typename _TraitsType::difference_type _DifferenceType; + + _GLIBCXX_CALL(__n) + + const _Settings& __s = _Settings::get(); + + if (__num_threads > __n) + __num_threads = static_cast<_ThreadIndex>(__n); + + _BinIndex __num_bins, __num_bins_cache; + +#if _GLIBCXX_RANDOM_SHUFFLE_CONSIDER_L1 + // Try the L1 cache first. + + // Must fit into L1. + __num_bins_cache = + std::max<_DifferenceType>(1, __n / (__s.L1_cache_size_lb + / sizeof(_ValueType))); + __num_bins_cache = __round_up_to_pow2(__num_bins_cache); + + // No more buckets than TLB entries, power of 2 + // Power of 2 and at least one element per bin, at most the TLB size. + __num_bins = std::min<_DifferenceType>(__n, __num_bins_cache); + +#if _GLIBCXX_RANDOM_SHUFFLE_CONSIDER_TLB + // 2 TLB entries needed per bin. + __num_bins = std::min<_DifferenceType>(__s.TLB_size / 2, __num_bins); +#endif + __num_bins = __round_up_to_pow2(__num_bins); + + if (__num_bins < __num_bins_cache) + { +#endif + // Now try the L2 cache + // Must fit into L2 + __num_bins_cache = static_cast<_BinIndex> + (std::max<_DifferenceType>(1, __n / (__s.L2_cache_size + / sizeof(_ValueType)))); + __num_bins_cache = __round_up_to_pow2(__num_bins_cache); + + // No more buckets than TLB entries, power of 2. + __num_bins = static_cast<_BinIndex> + (std::min(__n, static_cast<_DifferenceType>(__num_bins_cache))); + // Power of 2 and at least one element per bin, at most the TLB size. +#if _GLIBCXX_RANDOM_SHUFFLE_CONSIDER_TLB + // 2 TLB entries needed per bin. + __num_bins = std::min(static_cast<_DifferenceType>(__s.TLB_size / 2), + __num_bins); +#endif + __num_bins = __round_up_to_pow2(__num_bins); +#if _GLIBCXX_RANDOM_SHUFFLE_CONSIDER_L1 + } +#endif + + __num_bins = __round_up_to_pow2( + std::max<_BinIndex>(__num_threads, __num_bins)); + + if (__num_threads <= 1) + { + _RandomNumber __derived_rng( + __rng(std::numeric_limits<uint32_t>::max())); + __sequential_random_shuffle(__begin, __end, __derived_rng); + return; + } + + _DRandomShufflingGlobalData<_RAIter> __sd(__begin); + _DRSSorterPU<_RAIter, _RandomNumber >* __pus; + _DifferenceType* __starts; + +# pragma omp parallel num_threads(__num_threads) + { + _ThreadIndex __num_threads = omp_get_num_threads(); +# pragma omp single + { + __pus = new _DRSSorterPU<_RAIter, _RandomNumber>[__num_threads]; + + __sd._M_temporaries = new _ValueType*[__num_threads]; + __sd._M_dist = new _DifferenceType*[__num_bins + 1]; + __sd._M_bin_proc = new _ThreadIndex[__num_bins]; + for (_BinIndex __b = 0; __b < __num_bins + 1; ++__b) + __sd._M_dist[__b] = new _DifferenceType[__num_threads + 1]; + for (_BinIndex __b = 0; __b < (__num_bins + 1); ++__b) + { + __sd._M_dist[0][0] = 0; + __sd._M_dist[__b][0] = 0; + } + __starts = __sd._M_starts = new _DifferenceType[__num_threads + 1]; + int __bin_cursor = 0; + __sd._M_num_bins = __num_bins; + __sd._M_num_bits = __rd_log2(__num_bins); + + _DifferenceType __chunk_length = __n / __num_threads, + __split = __n % __num_threads, + __start = 0; + _DifferenceType __bin_chunk_length = __num_bins / __num_threads, + __bin_split = __num_bins % __num_threads; + for (_ThreadIndex __i = 0; __i < __num_threads; ++__i) + { + __starts[__i] = __start; + __start += (__i < __split + ? (__chunk_length + 1) : __chunk_length); + int __j = __pus[__i]._M_bins_begin = __bin_cursor; + + // Range of bins for this processor. + __bin_cursor += (__i < __bin_split + ? (__bin_chunk_length + 1) + : __bin_chunk_length); + __pus[__i].__bins_end = __bin_cursor; + for (; __j < __bin_cursor; ++__j) + __sd._M_bin_proc[__j] = __i; + __pus[__i]._M_num_threads = __num_threads; + __pus[__i]._M_seed = __rng(std::numeric_limits<uint32_t>::max()); + __pus[__i]._M_sd = &__sd; + } + __starts[__num_threads] = __start; + } //single + // Now shuffle in parallel. + __parallel_random_shuffle_drs_pu(__pus); + } // parallel + + delete[] __starts; + delete[] __sd._M_bin_proc; + for (int __s = 0; __s < (__num_bins + 1); ++__s) + delete[] __sd._M_dist[__s]; + delete[] __sd._M_dist; + delete[] __sd._M_temporaries; + + delete[] __pus; + } + + /** @brief Sequential cache-efficient random shuffle. + * @param __begin Begin iterator of sequence. + * @param __end End iterator of sequence. + * @param __rng Random number generator to use. + */ + template<typename _RAIter, typename _RandomNumberGenerator> + void + __sequential_random_shuffle(_RAIter __begin, _RAIter __end, + _RandomNumberGenerator& __rng) + { + typedef std::iterator_traits<_RAIter> _TraitsType; + typedef typename _TraitsType::value_type _ValueType; + typedef typename _TraitsType::difference_type _DifferenceType; + + _DifferenceType __n = __end - __begin; + const _Settings& __s = _Settings::get(); + + _BinIndex __num_bins, __num_bins_cache; + +#if _GLIBCXX_RANDOM_SHUFFLE_CONSIDER_L1 + // Try the L1 cache first, must fit into L1. + __num_bins_cache = std::max<_DifferenceType> + (1, __n / (__s.L1_cache_size_lb / sizeof(_ValueType))); + __num_bins_cache = __round_up_to_pow2(__num_bins_cache); + + // No more buckets than TLB entries, power of 2 + // Power of 2 and at least one element per bin, at most the TLB size + __num_bins = std::min(__n, (_DifferenceType)__num_bins_cache); +#if _GLIBCXX_RANDOM_SHUFFLE_CONSIDER_TLB + // 2 TLB entries needed per bin + __num_bins = std::min((_DifferenceType)__s.TLB_size / 2, __num_bins); +#endif + __num_bins = __round_up_to_pow2(__num_bins); + + if (__num_bins < __num_bins_cache) + { +#endif + // Now try the L2 cache, must fit into L2. + __num_bins_cache = static_cast<_BinIndex> + (std::max<_DifferenceType>(1, __n / (__s.L2_cache_size + / sizeof(_ValueType)))); + __num_bins_cache = __round_up_to_pow2(__num_bins_cache); + + // No more buckets than TLB entries, power of 2 + // Power of 2 and at least one element per bin, at most the TLB size. + __num_bins = static_cast<_BinIndex> + (std::min(__n, static_cast<_DifferenceType>(__num_bins_cache))); + +#if _GLIBCXX_RANDOM_SHUFFLE_CONSIDER_TLB + // 2 TLB entries needed per bin + __num_bins = std::min<_DifferenceType>(__s.TLB_size / 2, __num_bins); +#endif + __num_bins = __round_up_to_pow2(__num_bins); +#if _GLIBCXX_RANDOM_SHUFFLE_CONSIDER_L1 + } +#endif + + int __num_bits = __rd_log2(__num_bins); + + if (__num_bins > 1) + { + _ValueType* __target = + static_cast<_ValueType*>(::operator new(sizeof(_ValueType) * __n)); + _BinIndex* __oracles = new _BinIndex[__n]; + _DifferenceType* __dist0 = new _DifferenceType[__num_bins + 1], + * __dist1 = new _DifferenceType[__num_bins + 1]; + + for (int __b = 0; __b < __num_bins + 1; ++__b) + __dist0[__b] = 0; + + _RandomNumber __bitrng(__rng(0xFFFFFFFF)); + + for (_DifferenceType __i = 0; __i < __n; ++__i) + { + _BinIndex __oracle = __random_number_pow2(__num_bits, __bitrng); + __oracles[__i] = __oracle; + + // To allow prefix (partial) sum. + ++(__dist0[__oracle + 1]); + } + + // Sum up bins. + __gnu_sequential::partial_sum(__dist0, __dist0 + __num_bins + 1, + __dist0); + + for (int __b = 0; __b < __num_bins + 1; ++__b) + __dist1[__b] = __dist0[__b]; + + // Distribute according to oracles. + for (_DifferenceType __i = 0; __i < __n; ++__i) + ::new(&(__target[(__dist0[__oracles[__i]])++])) + _ValueType(*(__begin + __i)); + + for (int __b = 0; __b < __num_bins; ++__b) + __sequential_random_shuffle(__target + __dist1[__b], + __target + __dist1[__b + 1], __rng); + + // Copy elements back. + std::copy(__target, __target + __n, __begin); + + delete[] __dist0; + delete[] __dist1; + delete[] __oracles; + + for (_DifferenceType __i = 0; __i < __n; ++__i) + __target[__i].~_ValueType(); + ::operator delete(__target); + } + else + __gnu_sequential::random_shuffle(__begin, __end, __rng); + } + + /** @brief Parallel random public call. + * @param __begin Begin iterator of sequence. + * @param __end End iterator of sequence. + * @param __rng Random number generator to use. + */ + template<typename _RAIter, typename _RandomNumberGenerator> + inline void + __parallel_random_shuffle(_RAIter __begin, _RAIter __end, + _RandomNumberGenerator __rng = _RandomNumber()) + { + typedef std::iterator_traits<_RAIter> _TraitsType; + typedef typename _TraitsType::difference_type _DifferenceType; + _DifferenceType __n = __end - __begin; + __parallel_random_shuffle_drs(__begin, __end, __n, + __get_max_threads(), __rng); + } +} + +#endif /* _GLIBCXX_PARALLEL_RANDOM_SHUFFLE_H */ |