1// -*- C++ -*-
2//===-- parallel_backend_serial.h -----------------------------------------===//
3//
4// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
5// See https://llvm.org/LICENSE.txt for license information.
6// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
7//
8//===----------------------------------------------------------------------===//
9
10#ifndef _PSTL_PARALLEL_BACKEND_SERIAL_H
11#define _PSTL_PARALLEL_BACKEND_SERIAL_H
12
13#include <algorithm>
14#include <cstddef>
15#include <memory>
16#include <numeric>
17#include <utility>
18
19namespace __pstl
20{
21namespace __serial
22{
23
24template <typename _Tp>
25class __buffer
26{
27    std::allocator<_Tp> __allocator_;
28    _Tp* __ptr_;
29    const std::size_t __buf_size_;
30    __buffer(const __buffer&) = delete;
31    void
32    operator=(const __buffer&) = delete;
33
34  public:
35    __buffer(std::size_t __n) : __allocator_(), __ptr_(__allocator_.allocate(__n)), __buf_size_(__n) {}
36
37    operator bool() const { return __ptr_ != nullptr; }
38    _Tp*
39    get() const
40    {
41        return __ptr_;
42    }
43    ~__buffer() { __allocator_.deallocate(__ptr_, __buf_size_); }
44};
45
46inline void
47__cancel_execution()
48{
49}
50
51template <class _ExecutionPolicy, class _Index, class _Fp>
52void
53__parallel_for(_ExecutionPolicy&&, _Index __first, _Index __last, _Fp __f)
54{
55    __f(__first, __last);
56}
57
58template <class _ExecutionPolicy, class _Value, class _Index, typename _RealBody, typename _Reduction>
59_Value
60__parallel_reduce(_ExecutionPolicy&&, _Index __first, _Index __last, const _Value& __identity,
61                  const _RealBody& __real_body, const _Reduction&)
62{
63    if (__first == __last)
64    {
65        return __identity;
66    }
67    else
68    {
69        return __real_body(__first, __last, __identity);
70    }
71}
72
73template <class _ExecutionPolicy, class _Index, class _UnaryOp, class _Tp, class _BinaryOp, class _Reduce>
74_Tp
75__parallel_transform_reduce(_ExecutionPolicy&&, _Index __first, _Index __last, _UnaryOp, _Tp __init, _BinaryOp,
76                            _Reduce __reduce)
77{
78    return __reduce(__first, __last, __init);
79}
80
81template <class _ExecutionPolicy, typename _Index, typename _Tp, typename _Rp, typename _Cp, typename _Sp, typename _Ap>
82void
83__parallel_strict_scan(_ExecutionPolicy&&, _Index __n, _Tp __initial, _Rp __reduce, _Cp __combine, _Sp __scan,
84                       _Ap __apex)
85{
86    _Tp __sum = __initial;
87    if (__n)
88        __sum = __combine(__sum, __reduce(_Index(0), __n));
89    __apex(__sum);
90    if (__n)
91        __scan(_Index(0), __n, __initial);
92}
93
94template <class _ExecutionPolicy, class _Index, class _UnaryOp, class _Tp, class _BinaryOp, class _Reduce, class _Scan>
95_Tp
96__parallel_transform_scan(_ExecutionPolicy&&, _Index __n, _UnaryOp, _Tp __init, _BinaryOp, _Reduce, _Scan __scan)
97{
98    return __scan(_Index(0), __n, __init);
99}
100
101template <class _ExecutionPolicy, typename _RandomAccessIterator, typename _Compare, typename _LeafSort>
102void
103__parallel_stable_sort(_ExecutionPolicy&&, _RandomAccessIterator __first, _RandomAccessIterator __last, _Compare __comp,
104                       _LeafSort __leaf_sort, std::size_t = 0)
105{
106    __leaf_sort(__first, __last, __comp);
107}
108
109template <class _ExecutionPolicy, typename _RandomAccessIterator1, typename _RandomAccessIterator2,
110          typename _RandomAccessIterator3, typename _Compare, typename _LeafMerge>
111void
112__parallel_merge(_ExecutionPolicy&&, _RandomAccessIterator1 __first1, _RandomAccessIterator1 __last1,
113                 _RandomAccessIterator2 __first2, _RandomAccessIterator2 __last2, _RandomAccessIterator3 __out,
114                 _Compare __comp, _LeafMerge __leaf_merge)
115{
116    __leaf_merge(__first1, __last1, __first2, __last2, __out, __comp);
117}
118
119template <class _ExecutionPolicy, typename _F1, typename _F2>
120void
121__parallel_invoke(_ExecutionPolicy&&, _F1&& __f1, _F2&& __f2)
122{
123    std::forward<_F1>(__f1)();
124    std::forward<_F2>(__f2)();
125}
126
127} // namespace __serial
128} // namespace __pstl
129
130namespace __pstl
131{
132namespace __par_backend
133{
134using namespace __pstl::__serial;
135}
136} // namespace __pstl
137
138#endif /* _PSTL_PARALLEL_BACKEND_SERIAL_H */
139