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1//===----------------------------------------------------------------------===//2//3// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.4// See https://llvm.org/LICENSE.txt for license information.5// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception6//7//===----------------------------------------------------------------------===//8 9#ifndef _LIBCPP___PSTL_BACKENDS_LIBDISPATCH_H10#define _LIBCPP___PSTL_BACKENDS_LIBDISPATCH_H11 12#include <__algorithm/inplace_merge.h>13#include <__algorithm/lower_bound.h>14#include <__algorithm/max.h>15#include <__algorithm/merge.h>16#include <__algorithm/upper_bound.h>17#include <__atomic/atomic.h>18#include <__config>19#include <__cstddef/ptrdiff_t.h>20#include <__exception/terminate.h>21#include <__iterator/iterator_traits.h>22#include <__iterator/move_iterator.h>23#include <__memory/allocator.h>24#include <__memory/construct_at.h>25#include <__memory/destroy.h>26#include <__memory/unique_ptr.h>27#include <__new/exceptions.h>28#include <__numeric/reduce.h>29#include <__pstl/backend_fwd.h>30#include <__pstl/cpu_algos/any_of.h>31#include <__pstl/cpu_algos/cpu_traits.h>32#include <__pstl/cpu_algos/fill.h>33#include <__pstl/cpu_algos/find_if.h>34#include <__pstl/cpu_algos/for_each.h>35#include <__pstl/cpu_algos/merge.h>36#include <__pstl/cpu_algos/stable_sort.h>37#include <__pstl/cpu_algos/transform.h>38#include <__pstl/cpu_algos/transform_reduce.h>39#include <__utility/empty.h>40#include <__utility/exception_guard.h>41#include <__utility/move.h>42#include <__utility/pair.h>43#include <optional>44 45_LIBCPP_PUSH_MACROS46#include <__undef_macros>47 48#if _LIBCPP_STD_VER >= 1749 50_LIBCPP_BEGIN_NAMESPACE_STD51namespace __pstl {52 53namespace __libdispatch {54// ::dispatch_apply is marked as __attribute__((nothrow)) because it doesn't let exceptions propagate, and neither do55// we.56// TODO: Do we want to add [[_Clang::__callback__(__func, __context, __)]]?57_LIBCPP_EXPORTED_FROM_ABI void58__dispatch_apply(size_t __chunk_count, void* __context, void (*__func)(void* __context, size_t __chunk)) noexcept;59 60template <class _Func>61_LIBCPP_HIDE_FROM_ABI void __dispatch_apply(size_t __chunk_count, _Func __func) noexcept {62 __libdispatch::__dispatch_apply(__chunk_count, &__func, [](void* __context, size_t __chunk) {63 (*static_cast<_Func*>(__context))(__chunk);64 });65}66 67struct __chunk_partitions {68 ptrdiff_t __chunk_count_; // includes the first chunk69 ptrdiff_t __chunk_size_;70 ptrdiff_t __first_chunk_size_;71};72 73[[__gnu__::__const__]] _LIBCPP_EXPORTED_FROM_ABI __chunk_partitions __partition_chunks(ptrdiff_t __size) noexcept;74 75template <class _RandomAccessIterator, class _Functor>76_LIBCPP_HIDE_FROM_ABI optional<__empty>77__dispatch_parallel_for(__chunk_partitions __partitions, _RandomAccessIterator __first, _Functor __func) {78 // Perform the chunked execution.79 __libdispatch::__dispatch_apply(__partitions.__chunk_count_, [&](size_t __chunk) {80 auto __this_chunk_size = __chunk == 0 ? __partitions.__first_chunk_size_ : __partitions.__chunk_size_;81 auto __index =82 __chunk == 083 ? 084 : (__chunk * __partitions.__chunk_size_) + (__partitions.__first_chunk_size_ - __partitions.__chunk_size_);85 __func(__first + __index, __first + __index + __this_chunk_size);86 });87 88 return __empty{};89}90} // namespace __libdispatch91 92template <>93struct __cpu_traits<__libdispatch_backend_tag> {94 template <class _RandomAccessIterator, class _Functor>95 _LIBCPP_HIDE_FROM_ABI static optional<__empty>96 __for_each(_RandomAccessIterator __first, _RandomAccessIterator __last, _Functor __func) {97 return __libdispatch::__dispatch_parallel_for(98 __libdispatch::__partition_chunks(__last - __first), std::move(__first), std::move(__func));99 }100 101 template <class _RandomAccessIterator1, class _RandomAccessIterator2, class _RandomAccessIteratorOut>102 struct __merge_range {103 __merge_range(_RandomAccessIterator1 __mid1, _RandomAccessIterator2 __mid2, _RandomAccessIteratorOut __result)104 : __mid1_(__mid1), __mid2_(__mid2), __result_(__result) {}105 106 _RandomAccessIterator1 __mid1_;107 _RandomAccessIterator2 __mid2_;108 _RandomAccessIteratorOut __result_;109 };110 111 template <typename _RandomAccessIterator1,112 typename _RandomAccessIterator2,113 typename _RandomAccessIterator3,114 typename _Compare,115 typename _LeafMerge>116 _LIBCPP_HIDE_FROM_ABI static optional<__empty>117 __merge(_RandomAccessIterator1 __first1,118 _RandomAccessIterator1 __last1,119 _RandomAccessIterator2 __first2,120 _RandomAccessIterator2 __last2,121 _RandomAccessIterator3 __result,122 _Compare __comp,123 _LeafMerge __leaf_merge) noexcept {124 __libdispatch::__chunk_partitions __partitions =125 __libdispatch::__partition_chunks(std::max<ptrdiff_t>(__last1 - __first1, __last2 - __first2));126 127 if (__partitions.__chunk_count_ == 0)128 return __empty{};129 130 if (__partitions.__chunk_count_ == 1) {131 __leaf_merge(__first1, __last1, __first2, __last2, __result, __comp);132 return __empty{};133 }134 135 using __merge_range_t = __merge_range<_RandomAccessIterator1, _RandomAccessIterator2, _RandomAccessIterator3>;136 auto const __n_ranges = __partitions.__chunk_count_ + 1;137 138 // TODO: use __uninitialized_buffer139 auto __destroy = [=](__merge_range_t* __ptr) {140 std::destroy_n(__ptr, __n_ranges);141 std::allocator<__merge_range_t>().deallocate(__ptr, __n_ranges);142 };143 144 unique_ptr<__merge_range_t[], decltype(__destroy)> __ranges(145 [&]() -> __merge_range_t* {146# if _LIBCPP_HAS_EXCEPTIONS147 try {148# endif149 return std::allocator<__merge_range_t>().allocate(__n_ranges);150# if _LIBCPP_HAS_EXCEPTIONS151 } catch (const std::bad_alloc&) {152 return nullptr;153 }154# endif155 }(),156 __destroy);157 158 if (!__ranges)159 return nullopt;160 161 // TODO: Improve the case where the smaller range is merged into just a few (or even one) chunks of the larger case162 __merge_range_t* __r = __ranges.get();163 std::__construct_at(__r++, __first1, __first2, __result);164 165 bool __iterate_first_range = __last1 - __first1 > __last2 - __first2;166 167 auto __compute_chunk = [&](size_t __chunk_size) -> __merge_range_t {168 auto [__mid1, __mid2] = [&] {169 if (__iterate_first_range) {170 auto __m1 = __first1 + __chunk_size;171 auto __m2 = std::lower_bound(__first2, __last2, __m1[-1], __comp);172 return std::make_pair(__m1, __m2);173 } else {174 auto __m2 = __first2 + __chunk_size;175 auto __m1 = std::lower_bound(__first1, __last1, __m2[-1], __comp);176 return std::make_pair(__m1, __m2);177 }178 }();179 180 __result += (__mid1 - __first1) + (__mid2 - __first2);181 __first1 = __mid1;182 __first2 = __mid2;183 return {std::move(__mid1), std::move(__mid2), __result};184 };185 186 // handle first chunk187 std::__construct_at(__r++, __compute_chunk(__partitions.__first_chunk_size_));188 189 // handle 2 -> N - 1 chunks190 for (ptrdiff_t __i = 0; __i != __partitions.__chunk_count_ - 2; ++__i)191 std::__construct_at(__r++, __compute_chunk(__partitions.__chunk_size_));192 193 // handle last chunk194 std::__construct_at(__r, __last1, __last2, __result);195 196 __libdispatch::__dispatch_apply(__partitions.__chunk_count_, [&](size_t __index) {197 auto __first_iters = __ranges[__index];198 auto __last_iters = __ranges[__index + 1];199 __leaf_merge(200 __first_iters.__mid1_,201 __last_iters.__mid1_,202 __first_iters.__mid2_,203 __last_iters.__mid2_,204 __first_iters.__result_,205 __comp);206 });207 208 return __empty{};209 }210 211 template <class _RandomAccessIterator, class _Transform, class _Value, class _Combiner, class _Reduction>212 _LIBCPP_HIDE_FROM_ABI static optional<_Value> __transform_reduce(213 _RandomAccessIterator __first,214 _RandomAccessIterator __last,215 _Transform __transform,216 _Value __init,217 _Combiner __combiner,218 _Reduction __reduction) {219 if (__first == __last)220 return __init;221 222 auto __partitions = __libdispatch::__partition_chunks(__last - __first);223 224 auto __destroy = [__count = __partitions.__chunk_count_](_Value* __ptr) {225 std::destroy_n(__ptr, __count);226 std::allocator<_Value>().deallocate(__ptr, __count);227 };228 229 // TODO: use __uninitialized_buffer230 // TODO: allocate one element per worker instead of one element per chunk231 unique_ptr<_Value[], decltype(__destroy)> __values(232 std::allocator<_Value>().allocate(__partitions.__chunk_count_), __destroy);233 234 // __dispatch_apply is noexcept235 __libdispatch::__dispatch_apply(__partitions.__chunk_count_, [&](size_t __chunk) {236 auto __this_chunk_size = __chunk == 0 ? __partitions.__first_chunk_size_ : __partitions.__chunk_size_;237 auto __index = __chunk == 0 ? 0238 : (__chunk * __partitions.__chunk_size_) +239 (__partitions.__first_chunk_size_ - __partitions.__chunk_size_);240 if (__this_chunk_size != 1) {241 std::__construct_at(242 __values.get() + __chunk,243 __reduction(__first + __index + 2,244 __first + __index + __this_chunk_size,245 __combiner(__transform(__first + __index), __transform(__first + __index + 1))));246 } else {247 std::__construct_at(__values.get() + __chunk, __transform(__first + __index));248 }249 });250 251 return std::reduce(252 std::make_move_iterator(__values.get()),253 std::make_move_iterator(__values.get() + __partitions.__chunk_count_),254 std::move(__init),255 __combiner);256 }257 258 template <class _RandomAccessIterator, class _Comp, class _LeafSort>259 _LIBCPP_HIDE_FROM_ABI static optional<__empty>260 __stable_sort(_RandomAccessIterator __first, _RandomAccessIterator __last, _Comp __comp, _LeafSort __leaf_sort) {261 const auto __size = __last - __first;262 auto __partitions = __libdispatch::__partition_chunks(__size);263 264 if (__partitions.__chunk_count_ == 0)265 return __empty{};266 267 if (__partitions.__chunk_count_ == 1) {268 __leaf_sort(__first, __last, __comp);269 return __empty{};270 }271 272 using _Value = __iterator_value_type<_RandomAccessIterator>;273 274 auto __destroy = [__size](_Value* __ptr) {275 std::destroy_n(__ptr, __size);276 std::allocator<_Value>().deallocate(__ptr, __size);277 };278 279 // TODO: use __uninitialized_buffer280 unique_ptr<_Value[], decltype(__destroy)> __values(std::allocator<_Value>().allocate(__size), __destroy);281 282 // Initialize all elements to a moved-from state283 // TODO: Don't do this - this can be done in the first merge - see https://llvm.org/PR63928284 std::__construct_at(__values.get(), std::move(*__first));285 for (__iterator_difference_type<_RandomAccessIterator> __i = 1; __i != __size; ++__i) {286 std::__construct_at(__values.get() + __i, std::move(__values.get()[__i - 1]));287 }288 *__first = std::move(__values.get()[__size - 1]);289 290 __libdispatch::__dispatch_parallel_for(291 __partitions,292 __first,293 [&__leaf_sort, &__comp](_RandomAccessIterator __chunk_first, _RandomAccessIterator __chunk_last) {294 __leaf_sort(std::move(__chunk_first), std::move(__chunk_last), __comp);295 });296 297 bool __objects_are_in_buffer = false;298 do {299 const auto __old_chunk_size = __partitions.__chunk_size_;300 if (__partitions.__chunk_count_ % 2 == 1) {301 auto __inplace_merge_chunks = [&__comp, &__partitions](auto __first_chunk_begin) {302 std::inplace_merge(303 __first_chunk_begin,304 __first_chunk_begin + __partitions.__first_chunk_size_,305 __first_chunk_begin + __partitions.__first_chunk_size_ + __partitions.__chunk_size_,306 __comp);307 };308 if (__objects_are_in_buffer)309 __inplace_merge_chunks(__values.get());310 else311 __inplace_merge_chunks(__first);312 __partitions.__first_chunk_size_ += 2 * __partitions.__chunk_size_;313 } else {314 __partitions.__first_chunk_size_ += __partitions.__chunk_size_;315 }316 317 __partitions.__chunk_size_ *= 2;318 __partitions.__chunk_count_ /= 2;319 320 auto __merge_chunks = [__partitions, __old_chunk_size, &__comp](auto __from_first, auto __to_first) {321 __libdispatch::__dispatch_parallel_for(322 __partitions,323 __from_first,324 [__old_chunk_size, &__from_first, &__to_first, &__comp](auto __chunk_first, auto __chunk_last) {325 std::merge(std::make_move_iterator(__chunk_first),326 std::make_move_iterator(__chunk_last - __old_chunk_size),327 std::make_move_iterator(__chunk_last - __old_chunk_size),328 std::make_move_iterator(__chunk_last),329 __to_first + (__chunk_first - __from_first),330 __comp);331 });332 };333 334 if (__objects_are_in_buffer)335 __merge_chunks(__values.get(), __first);336 else337 __merge_chunks(__first, __values.get());338 __objects_are_in_buffer = !__objects_are_in_buffer;339 } while (__partitions.__chunk_count_ > 1);340 341 if (__objects_are_in_buffer) {342 std::move(__values.get(), __values.get() + __size, __first);343 }344 345 return __empty{};346 }347 348 _LIBCPP_HIDE_FROM_ABI static void __cancel_execution() {}349 350 static constexpr size_t __lane_size = 64;351};352 353// Mandatory implementations of the computational basis354template <class _ExecutionPolicy>355struct __find_if<__libdispatch_backend_tag, _ExecutionPolicy>356 : __cpu_parallel_find_if<__libdispatch_backend_tag, _ExecutionPolicy> {};357 358template <class _ExecutionPolicy>359struct __for_each<__libdispatch_backend_tag, _ExecutionPolicy>360 : __cpu_parallel_for_each<__libdispatch_backend_tag, _ExecutionPolicy> {};361 362template <class _ExecutionPolicy>363struct __merge<__libdispatch_backend_tag, _ExecutionPolicy>364 : __cpu_parallel_merge<__libdispatch_backend_tag, _ExecutionPolicy> {};365 366template <class _ExecutionPolicy>367struct __stable_sort<__libdispatch_backend_tag, _ExecutionPolicy>368 : __cpu_parallel_stable_sort<__libdispatch_backend_tag, _ExecutionPolicy> {};369 370template <class _ExecutionPolicy>371struct __transform<__libdispatch_backend_tag, _ExecutionPolicy>372 : __cpu_parallel_transform<__libdispatch_backend_tag, _ExecutionPolicy> {};373 374template <class _ExecutionPolicy>375struct __transform_binary<__libdispatch_backend_tag, _ExecutionPolicy>376 : __cpu_parallel_transform_binary<__libdispatch_backend_tag, _ExecutionPolicy> {};377 378template <class _ExecutionPolicy>379struct __transform_reduce<__libdispatch_backend_tag, _ExecutionPolicy>380 : __cpu_parallel_transform_reduce<__libdispatch_backend_tag, _ExecutionPolicy> {};381 382template <class _ExecutionPolicy>383struct __transform_reduce_binary<__libdispatch_backend_tag, _ExecutionPolicy>384 : __cpu_parallel_transform_reduce_binary<__libdispatch_backend_tag, _ExecutionPolicy> {};385 386// Not mandatory, but better optimized387template <class _ExecutionPolicy>388struct __any_of<__libdispatch_backend_tag, _ExecutionPolicy>389 : __cpu_parallel_any_of<__libdispatch_backend_tag, _ExecutionPolicy> {};390 391template <class _ExecutionPolicy>392struct __fill<__libdispatch_backend_tag, _ExecutionPolicy>393 : __cpu_parallel_fill<__libdispatch_backend_tag, _ExecutionPolicy> {};394 395} // namespace __pstl396_LIBCPP_END_NAMESPACE_STD397 398#endif // _LIBCPP_STD_VER >= 17399 400_LIBCPP_POP_MACROS401 402#endif // _LIBCPP___PSTL_BACKENDS_LIBDISPATCH_H403