1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
|
//===----------------------------------------------------------------------===//
//
// 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___ALGORITHM_PSTL_BACKENDS_CPU_BACKENDS_FIND_IF_H
#define _LIBCPP___ALGORITHM_PSTL_BACKENDS_CPU_BACKENDS_FIND_IF_H
#include <__algorithm/find_if.h>
#include <__algorithm/pstl_backends/cpu_backends/backend.h>
#include <__atomic/atomic.h>
#include <__config>
#include <__functional/operations.h>
#include <__iterator/concepts.h>
#include <__iterator/iterator_traits.h>
#include <__pstl/cpu_algos/cpu_traits.h>
#include <__type_traits/is_execution_policy.h>
#include <__utility/move.h>
#include <__utility/pair.h>
#include <cstddef>
#include <optional>
#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
# pragma GCC system_header
#endif
#if !defined(_LIBCPP_HAS_NO_INCOMPLETE_PSTL) && _LIBCPP_STD_VER >= 17
_LIBCPP_PUSH_MACROS
# include <__undef_macros>
_LIBCPP_BEGIN_NAMESPACE_STD
template <class _Backend, class _Index, class _Brick, class _Compare>
_LIBCPP_HIDE_FROM_ABI optional<_Index>
__parallel_find(_Index __first, _Index __last, _Brick __f, _Compare __comp, bool __b_first) {
typedef typename std::iterator_traits<_Index>::difference_type _DifferenceType;
const _DifferenceType __n = __last - __first;
_DifferenceType __initial_dist = __b_first ? __n : -1;
std::atomic<_DifferenceType> __extremum(__initial_dist);
// TODO: find out what is better here: parallel_for or parallel_reduce
auto __res = __pstl::__cpu_traits<_Backend>::__for_each(
__first, __last, [__comp, __f, __first, &__extremum](_Index __i, _Index __j) {
// See "Reducing Contention Through Priority Updates", PPoPP '13, for discussion of
// why using a shared variable scales fairly well in this situation.
if (__comp(__i - __first, __extremum)) {
_Index __result = __f(__i, __j);
// If not '__last' returned then we found what we want so put this to extremum
if (__result != __j) {
const _DifferenceType __k = __result - __first;
for (_DifferenceType __old = __extremum; __comp(__k, __old); __old = __extremum) {
__extremum.compare_exchange_weak(__old, __k);
}
}
}
});
if (!__res)
return nullopt;
return __extremum.load() != __initial_dist ? __first + __extremum.load() : __last;
}
template <class _Backend, class _Index, class _DifferenceType, class _Compare>
_LIBCPP_HIDE_FROM_ABI _Index
__simd_first(_Index __first, _DifferenceType __begin, _DifferenceType __end, _Compare __comp) noexcept {
// Experiments show good block sizes like this
const _DifferenceType __block_size = 8;
alignas(__pstl::__cpu_traits<_Backend>::__lane_size) _DifferenceType __lane[__block_size] = {0};
while (__end - __begin >= __block_size) {
_DifferenceType __found = 0;
_PSTL_PRAGMA_SIMD_REDUCTION(| : __found) for (_DifferenceType __i = __begin; __i < __begin + __block_size; ++__i) {
const _DifferenceType __t = __comp(__first, __i);
__lane[__i - __begin] = __t;
__found |= __t;
}
if (__found) {
_DifferenceType __i;
// This will vectorize
for (__i = 0; __i < __block_size; ++__i) {
if (__lane[__i]) {
break;
}
}
return __first + __begin + __i;
}
__begin += __block_size;
}
// Keep remainder scalar
while (__begin != __end) {
if (__comp(__first, __begin)) {
return __first + __begin;
}
++__begin;
}
return __first + __end;
}
template <class _ExecutionPolicy, class _ForwardIterator, class _Predicate>
_LIBCPP_HIDE_FROM_ABI optional<_ForwardIterator>
__pstl_find_if(__cpu_backend_tag, _ForwardIterator __first, _ForwardIterator __last, _Predicate __pred) {
if constexpr (__is_parallel_execution_policy_v<_ExecutionPolicy> &&
__has_random_access_iterator_category_or_concept<_ForwardIterator>::value) {
return std::__parallel_find<__cpu_backend_tag>(
__first,
__last,
[&__pred](_ForwardIterator __brick_first, _ForwardIterator __brick_last) {
auto __res = std::__pstl_find_if<__remove_parallel_policy_t<_ExecutionPolicy>>(
__cpu_backend_tag{}, __brick_first, __brick_last, __pred);
_LIBCPP_ASSERT_INTERNAL(__res, "unseq/seq should never try to allocate!");
return *std::move(__res);
},
less<>{},
true);
} else if constexpr (__is_unsequenced_execution_policy_v<_ExecutionPolicy> &&
__has_random_access_iterator_category_or_concept<_ForwardIterator>::value) {
using __diff_t = __iter_diff_t<_ForwardIterator>;
return std::__simd_first<__cpu_backend_tag>(
__first, __diff_t(0), __last - __first, [&__pred](_ForwardIterator __iter, __diff_t __i) {
return __pred(__iter[__i]);
});
} else {
return std::find_if(__first, __last, __pred);
}
}
_LIBCPP_END_NAMESPACE_STD
_LIBCPP_POP_MACROS
#endif // !defined(_LIBCPP_HAS_NO_INCOMPLETE_PSTL) && _LIBCPP_STD_VER >= 17
#endif // _LIBCPP___ALGORITHM_PSTL_BACKENDS_CPU_BACKENDS_FIND_IF_H
|
