//===----------------------------------------------------------------------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
#ifndef _LIBCPP___PSTL_BACKENDS_LIBDISPATCH_H
#define _LIBCPP___PSTL_BACKENDS_LIBDISPATCH_H
#include <__algorithm/inplace_merge.h>
#include <__algorithm/lower_bound.h>
#include <__algorithm/max.h>
#include <__algorithm/merge.h>
#include <__algorithm/upper_bound.h>
#include <__atomic/atomic.h>
#include <__config>
#include <__exception/terminate.h>
#include <__iterator/iterator_traits.h>
#include <__iterator/move_iterator.h>
#include <__memory/allocator.h>
#include <__memory/construct_at.h>
#include <__memory/unique_ptr.h>
#include <__numeric/reduce.h>
#include <__pstl/backend_fwd.h>
#include <__pstl/cpu_algos/any_of.h>
#include <__pstl/cpu_algos/cpu_traits.h>
#include <__pstl/cpu_algos/fill.h>
#include <__pstl/cpu_algos/find_if.h>
#include <__pstl/cpu_algos/for_each.h>
#include <__pstl/cpu_algos/merge.h>
#include <__pstl/cpu_algos/stable_sort.h>
#include <__pstl/cpu_algos/transform.h>
#include <__pstl/cpu_algos/transform_reduce.h>
#include <__utility/empty.h>
#include <__utility/exception_guard.h>
#include <__utility/move.h>
#include <__utility/pair.h>
#include <cstddef>
#include <new>
#include <optional>
_LIBCPP_PUSH_MACROS
#include <__undef_macros>
#if _LIBCPP_STD_VER >= 17
_LIBCPP_BEGIN_NAMESPACE_STD
namespace __pstl {
namespace __libdispatch {
// ::dispatch_apply is marked as __attribute__((nothrow)) because it doesn't let exceptions propagate, and neither do
// we.
// TODO: Do we want to add [[_Clang::__callback__(__func, __context, __)]]?
_LIBCPP_EXPORTED_FROM_ABI void
__dispatch_apply(size_t __chunk_count, void* __context, void (*__func)(void* __context, size_t __chunk)) noexcept;
template <class _Func>
_LIBCPP_HIDE_FROM_ABI void __dispatch_apply(size_t __chunk_count, _Func __func) noexcept {
__libdispatch::__dispatch_apply(__chunk_count, &__func, [](void* __context, size_t __chunk) {
(*static_cast<_Func*>(__context))(__chunk);
});
}
struct __chunk_partitions {
ptrdiff_t __chunk_count_; // includes the first chunk
ptrdiff_t __chunk_size_;
ptrdiff_t __first_chunk_size_;
};
[[__gnu__::__const__]] _LIBCPP_EXPORTED_FROM_ABI __chunk_partitions __partition_chunks(ptrdiff_t __size) noexcept;
template <class _RandomAccessIterator, class _Functor>
_LIBCPP_HIDE_FROM_ABI optional<__empty>
__dispatch_parallel_for(__chunk_partitions __partitions, _RandomAccessIterator __first, _Functor __func) {
// Perform the chunked execution.
__libdispatch::__dispatch_apply(__partitions.__chunk_count_, [&](size_t __chunk) {
auto __this_chunk_size = __chunk == 0 ? __partitions.__first_chunk_size_ : __partitions.__chunk_size_;
auto __index =
__chunk == 0
? 0
: (__chunk * __partitions.__chunk_size_) + (__partitions.__first_chunk_size_ - __partitions.__chunk_size_);
__func(__first + __index, __first + __index + __this_chunk_size);
});
return __empty{};
}
} // namespace __libdispatch
template <>
struct __cpu_traits<__libdispatch_backend_tag> {
template <class _RandomAccessIterator, class _Functor>
_LIBCPP_HIDE_FROM_ABI static optional<__empty>
__for_each(_RandomAccessIterator __first, _RandomAccessIterator __last, _Functor __func) {
return __libdispatch::__dispatch_parallel_for(
__libdispatch::__partition_chunks(__last - __first), std::move(__first), std::move(__func));
}
template <class _RandomAccessIterator1, class _RandomAccessIterator2, class _RandomAccessIteratorOut>
struct __merge_range {
__merge_range(_RandomAccessIterator1 __mid1, _RandomAccessIterator2 __mid2, _RandomAccessIteratorOut __result)
: __mid1_(__mid1), __mid2_(__mid2), __result_(__result) {}
_RandomAccessIterator1 __mid1_;
_RandomAccessIterator2 __mid2_;
_RandomAccessIteratorOut __result_;
};
template <typename _RandomAccessIterator1,
typename _RandomAccessIterator2,
typename _RandomAccessIterator3,
typename _Compare,
typename _LeafMerge>
_LIBCPP_HIDE_FROM_ABI static optional<__empty>
__merge(_RandomAccessIterator1 __first1,
_RandomAccessIterator1 __last1,
_RandomAccessIterator2 __first2,
_RandomAccessIterator2 __last2,
_RandomAccessIterator3 __result,
_Compare __comp,
_LeafMerge __leaf_merge) noexcept {
__libdispatch::__chunk_partitions __partitions =
__libdispatch::__partition_chunks(std::max<ptrdiff_t>(__last1 - __first1, __last2 - __first2));
if (__partitions.__chunk_count_ == 0)
return __empty{};
if (__partitions.__chunk_count_ == 1) {
__leaf_merge(__first1, __last1, __first2, __last2, __result, __comp);
return __empty{};
}
using __merge_range_t = __merge_range<_RandomAccessIterator1, _RandomAccessIterator2, _RandomAccessIterator3>;
auto const __n_ranges = __partitions.__chunk_count_ + 1;
// TODO: use __uninitialized_buffer
auto __destroy = [=](__merge_range_t* __ptr) {
std::destroy_n(__ptr, __n_ranges);
std::allocator<__merge_range_t>().deallocate(__ptr, __n_ranges);
};
unique_ptr<__merge_range_t[], decltype(__destroy)> __ranges(
[&]() -> __merge_range_t* {
# ifndef _LIBCPP_HAS_NO_EXCEPTIONS
try {
# endif
return std::allocator<__merge_range_t>().allocate(__n_ranges);
# ifndef _LIBCPP_HAS_NO_EXCEPTIONS
} catch (const std::bad_alloc&) {
return nullptr;
}
# endif
}(),
__destroy);
if (!__ranges)
return nullopt;
// TODO: Improve the case where the smaller range is merged into just a few (or even one) chunks of the larger case
__merge_range_t* __r = __ranges.get();
std::__construct_at(__r++, __first1, __first2, __result);
bool __iterate_first_range = __last1 - __first1 > __last2 - __first2;
auto __compute_chunk = [&](size_t __chunk_size) -> __merge_range_t {
auto [__mid1, __mid2] = [&] {
if (__iterate_first_range) {
auto __m1 = __first1 + __chunk_size;
auto __m2 = std::lower_bound(__first2, __last2, __m1[-1], __comp);
return std::make_pair(__m1, __m2);
} else {
auto __m2 = __first2 + __chunk_size;
auto __m1 = std::lower_bound(__first1, __last1, __m2[-1], __comp);
return std::make_pair(__m1, __m2);
}
}();
__result += (__mid1 - __first1) + (__mid2 - __first2);
__first1 = __mid1;
__first2 = __mid2;
return {std::move(__mid1), std::move(__mid2), __result};
};
// handle first chunk
std::__construct_at(__r++, __compute_chunk(__partitions.__first_chunk_size_));
// handle 2 -> N - 1 chunks
for (ptrdiff_t __i = 0; __i != __partitions.__chunk_count_ - 2; ++__i)
std::__construct_at(__r++, __compute_chunk(__partitions.__chunk_size_));
// handle last chunk
std::__construct_at(__r, __last1, __last2, __result);
__libdispatch::__dispatch_apply(__partitions.__chunk_count_, [&](size_t __index) {
auto __first_iters = __ranges[__index];
auto __last_iters = __ranges[__index + 1];
__leaf_merge(
__first_iters.__mid1_,
__last_iters.__mid1_,
__first_iters.__mid2_,
__last_iters.__mid2_,
__first_iters.__result_,
__comp);
});
return __empty{};
}
template <class _RandomAccessIterator, class _Transform, class _Value, class _Combiner, class _Reduction>
_LIBCPP_HIDE_FROM_ABI static optional<_Value> __transform_reduce(
_RandomAccessIterator __first,
_RandomAccessIterator __last,
_Transform __transform,
_Value __init,
_Combiner __combiner,
_Reduction __reduction) {
if (__first == __last)
return __init;
auto __partitions = __libdispatch::__partition_chunks(__last - __first);
auto __destroy = [__count = __partitions.__chunk_count_](_Value* __ptr) {
std::destroy_n(__ptr, __count);
std::allocator<_Value>().deallocate(__ptr, __count);
};
// TODO: use __uninitialized_buffer
// TODO: allocate one element per worker instead of one element per chunk
unique_ptr<_Value[], decltype(__destroy)> __values(
std::allocator<_Value>().allocate(__partitions.__chunk_count_), __destroy);
// __dispatch_apply is noexcept
__libdispatch::__dispatch_apply(__partitions.__chunk_count_, [&](size_t __chunk) {
auto __this_chunk_size = __chunk == 0 ? __partitions.__first_chunk_size_ : __partitions.__chunk_size_;
auto __index = __chunk == 0 ? 0
: (__chunk * __partitions.__chunk_size_) +
(__partitions.__first_chunk_size_ - __partitions.__chunk_size_);
if (__this_chunk_size != 1) {
std::__construct_at(
__values.get() + __chunk,
__reduction(__first + __index + 2,
__first + __index + __this_chunk_size,
__combiner(__transform(__first + __index), __transform(__first + __index + 1))));
} else {
std::__construct_at(__values.get() + __chunk, __transform(__first + __index));
}
});
return std::reduce(
std::make_move_iterator(__values.get()),
std::make_move_iterator(__values.get() + __partitions.__chunk_count_),
std::move(__init),
__combiner);
}
template <class _RandomAccessIterator, class _Comp, class _LeafSort>
_LIBCPP_HIDE_FROM_ABI static optional<__empty>
__stable_sort(_RandomAccessIterator __first, _RandomAccessIterator __last, _Comp __comp, _LeafSort __leaf_sort) {
const auto __size = __last - __first;
auto __partitions = __libdispatch::__partition_chunks(__size);
if (__partitions.__chunk_count_ == 0)
return __empty{};
if (__partitions.__chunk_count_ == 1) {
__leaf_sort(__first, __last, __comp);
return __empty{};
}
using _Value = __iter_value_type<_RandomAccessIterator>;
auto __destroy = [__size](_Value* __ptr) {
std::destroy_n(__ptr, __size);
std::allocator<_Value>().deallocate(__ptr, __size);
};
// TODO: use __uninitialized_buffer
unique_ptr<_Value[], decltype(__destroy)> __values(std::allocator<_Value>().allocate(__size), __destroy);
// Initialize all elements to a moved-from state
// TODO: Don't do this - this can be done in the first merge - see https://llvm.org/PR63928
std::__construct_at(__values.get(), std::move(*__first));
for (__iter_diff_t<_RandomAccessIterator> __i = 1; __i != __size; ++__i) {
std::__construct_at(__values.get() + __i, std::move(__values.get()[__i - 1]));
}
*__first = std::move(__values.get()[__size - 1]);
__libdispatch::__dispatch_parallel_for(
__partitions,
__first,
[&__leaf_sort, &__comp](_RandomAccessIterator __chunk_first, _RandomAccessIterator __chunk_last) {
__leaf_sort(std::move(__chunk_first), std::move(__chunk_last), __comp);
});
bool __objects_are_in_buffer = false;
do {
const auto __old_chunk_size = __partitions.__chunk_size_;
if (__partitions.__chunk_count_ % 2 == 1) {
auto __inplace_merge_chunks = [&__comp, &__partitions](auto __first_chunk_begin) {
std::inplace_merge(
__first_chunk_begin,
__first_chunk_begin + __partitions.__first_chunk_size_,
__first_chunk_begin + __partitions.__first_chunk_size_ + __partitions.__chunk_size_,
__comp);
};
if (__objects_are_in_buffer)
__inplace_merge_chunks(__values.get());
else
__inplace_merge_chunks(__first);
__partitions.__first_chunk_size_ += 2 * __partitions.__chunk_size_;
} else {
__partitions.__first_chunk_size_ += __partitions.__chunk_size_;
}
__partitions.__chunk_size_ *= 2;
__partitions.__chunk_count_ /= 2;
auto __merge_chunks = [__partitions, __old_chunk_size, &__comp](auto __from_first, auto __to_first) {
__libdispatch::__dispatch_parallel_for(
__partitions,
__from_first,
[__old_chunk_size, &__from_first, &__to_first, &__comp](auto __chunk_first, auto __chunk_last) {
std::merge(std::make_move_iterator(__chunk_first),
std::make_move_iterator(__chunk_last - __old_chunk_size),
std::make_move_iterator(__chunk_last - __old_chunk_size),
std::make_move_iterator(__chunk_last),
__to_first + (__chunk_first - __from_first),
__comp);
});
};
if (__objects_are_in_buffer)
__merge_chunks(__values.get(), __first);
else
__merge_chunks(__first, __values.get());
__objects_are_in_buffer = !__objects_are_in_buffer;
} while (__partitions.__chunk_count_ > 1);
if (__objects_are_in_buffer) {
std::move(__values.get(), __values.get() + __size, __first);
}
return __empty{};
}
_LIBCPP_HIDE_FROM_ABI static void __cancel_execution() {}
static constexpr size_t __lane_size = 64;
};
// Mandatory implementations of the computational basis
template <class _ExecutionPolicy>
struct __find_if<__libdispatch_backend_tag, _ExecutionPolicy>
: __cpu_parallel_find_if<__libdispatch_backend_tag, _ExecutionPolicy> {};
template <class _ExecutionPolicy>
struct __for_each<__libdispatch_backend_tag, _ExecutionPolicy>
: __cpu_parallel_for_each<__libdispatch_backend_tag, _ExecutionPolicy> {};
template <class _ExecutionPolicy>
struct __merge<__libdispatch_backend_tag, _ExecutionPolicy>
: __cpu_parallel_merge<__libdispatch_backend_tag, _ExecutionPolicy> {};
template <class _ExecutionPolicy>
struct __stable_sort<__libdispatch_backend_tag, _ExecutionPolicy>
: __cpu_parallel_stable_sort<__libdispatch_backend_tag, _ExecutionPolicy> {};
template <class _ExecutionPolicy>
struct __transform<__libdispatch_backend_tag, _ExecutionPolicy>
: __cpu_parallel_transform<__libdispatch_backend_tag, _ExecutionPolicy> {};
template <class _ExecutionPolicy>
struct __transform_binary<__libdispatch_backend_tag, _ExecutionPolicy>
: __cpu_parallel_transform_binary<__libdispatch_backend_tag, _ExecutionPolicy> {};
template <class _ExecutionPolicy>
struct __transform_reduce<__libdispatch_backend_tag, _ExecutionPolicy>
: __cpu_parallel_transform_reduce<__libdispatch_backend_tag, _ExecutionPolicy> {};
template <class _ExecutionPolicy>
struct __transform_reduce_binary<__libdispatch_backend_tag, _ExecutionPolicy>
: __cpu_parallel_transform_reduce_binary<__libdispatch_backend_tag, _ExecutionPolicy> {};
// Not mandatory, but better optimized
template <class _ExecutionPolicy>
struct __any_of<__libdispatch_backend_tag, _ExecutionPolicy>
: __cpu_parallel_any_of<__libdispatch_backend_tag, _ExecutionPolicy> {};
template <class _ExecutionPolicy>
struct __fill<__libdispatch_backend_tag, _ExecutionPolicy>
: __cpu_parallel_fill<__libdispatch_backend_tag, _ExecutionPolicy> {};
} // namespace __pstl
_LIBCPP_END_NAMESPACE_STD
#endif // _LIBCPP_STD_VER >= 17
_LIBCPP_POP_MACROS
#endif // _LIBCPP___PSTL_BACKENDS_LIBDISPATCH_H
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