libcxx/include/__algorithm/pstl_backends/cpu_backends/any_of.h

   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-exception
   6 //
   7 //===----------------------------------------------------------------------===//
   8
   9 #ifndef _LIBCPP___ALGORITHM_PSTL_BACKENDS_CPU_BACKEND_ANY_OF_H
  10 #define _LIBCPP___ALGORITHM_PSTL_BACKENDS_CPU_BACKEND_ANY_OF_H
  11
  12 #include <__algorithm/any_of.h>
  13 #include <__algorithm/find_if.h>
  14 #include <__algorithm/pstl_backends/cpu_backends/backend.h>
  15 #include <__atomic/atomic.h>
  16 #include <__atomic/memory_order.h>
  17 #include <__config>
  18 #include <__functional/operations.h>
  19 #include <__iterator/concepts.h>
  20 #include <__type_traits/is_execution_policy.h>
  21 #include <__utility/move.h>
  22 #include <__utility/pair.h>
  23 #include <cstdint>
  24 #include <optional>
  25
  26 #if !defined(_LIBCPP_HAS_NO_INCOMPLETE_PSTL) && _LIBCPP_STD_VER >= 17
  27
  28 _LIBCPP_PUSH_MACROS
  29 #  include <__undef_macros>
  30
  31 _LIBCPP_BEGIN_NAMESPACE_STD
  32
  33 template <class _Index, class _Brick>
  34 _LIBCPP_HIDE_FROM_ABI optional<bool> __parallel_or(_Index __first, _Index __last, _Brick __f) {
  35   std::atomic<bool> __found(false);
  36   auto __ret = __par_backend::__parallel_for(__first, __last, [__f, &__found](_Index __i, _Index __j) {
  37     if (!__found.load(std::memory_order_relaxed) && __f(__i, __j)) {
  38       __found.store(true, std::memory_order_relaxed);
  39       __par_backend::__cancel_execution();
  40     }
  41   });
  42   if (!__ret)
  43     return nullopt;
  44   return static_cast<bool>(__found);
  45 }
  46
  47 // TODO: check whether __simd_first() can be used here
  48 template <class _Index, class _DifferenceType, class _Pred>
  49 _LIBCPP_HIDE_FROM_ABI bool __simd_or(_Index __first, _DifferenceType __n, _Pred __pred) noexcept {
  50   _DifferenceType __block_size = 4 < __n ? 4 : __n;
  51   const _Index __last          = __first + __n;
  52   while (__last != __first) {
  53     int32_t __flag = 1;
  54     _PSTL_PRAGMA_SIMD_REDUCTION(& : __flag)
  55     for (_DifferenceType __i = 0; __i < __block_size; ++__i)
  56       if (__pred(*(__first + __i)))
  57         __flag = 0;
  58     if (!__flag)
  59       return true;
  60
  61     __first += __block_size;
  62     if (__last - __first >= __block_size << 1) {
  63       // Double the block _Size.  Any unnecessary iterations can be amortized against work done so far.
  64       __block_size <<= 1;
  65     } else {
  66       __block_size = __last - __first;
  67     }
  68   }
  69   return false;
  70 }
  71
  72 template <class _ExecutionPolicy, class _ForwardIterator, class _Predicate>
  73 _LIBCPP_HIDE_FROM_ABI optional<bool>
  74 __pstl_any_of(__cpu_backend_tag, _ForwardIterator __first, _ForwardIterator __last, _Predicate __pred) {
  75   if constexpr (__is_parallel_execution_policy_v<_ExecutionPolicy> &&
  76                 __has_random_access_iterator_category_or_concept<_ForwardIterator>::value) {
  77     return std::__parallel_or(
  78         __first, __last, [&__pred](_ForwardIterator __brick_first, _ForwardIterator __brick_last) {
  79           auto __res = std::__pstl_any_of<__remove_parallel_policy_t<_ExecutionPolicy>>(
  80               __cpu_backend_tag{}, __brick_first, __brick_last, __pred);
  81           _LIBCPP_ASSERT_INTERNAL(__res, "unseq/seq should never try to allocate!");
  82           return *std::move(__res);
  83         });
  84   } else if constexpr (__is_unsequenced_execution_policy_v<_ExecutionPolicy> &&
  85                        __has_random_access_iterator_category_or_concept<_ForwardIterator>::value) {
  86     return std::__simd_or(__first, __last - __first, __pred);
  87   } else {
  88     return std::any_of(__first, __last, __pred);
  89   }
  90 }
  91
  92 _LIBCPP_END_NAMESPACE_STD
  93
  94 _LIBCPP_POP_MACROS
  95
  96 #endif // !defined(_LIBCPP_HAS_NO_INCOMPLETE_PSTL) && _LIBCPP_STD_VER >= 17
  97
  98 #endif // _LIBCPP___ALGORITHM_PSTL_BACKENDS_CPU_BACKEND_ANY_OF_H