Open3D (C++ API)  0.17.0
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ParallelScan.h
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1// ----------------------------------------------------------------------------
2// - Open3D: www.open3d.org -
3// ----------------------------------------------------------------------------
4// Copyright (c) 2018-2023 www.open3d.org
5// SPDX-License-Identifier: MIT
6// ----------------------------------------------------------------------------
7
8#pragma once
9
10#include <tbb/parallel_for.h>
11#include <tbb/parallel_scan.h>
12
13// clang-format off
14#if TBB_INTERFACE_VERSION >= 10000
15 #ifdef OPEN3D_USE_ONEAPI_PACKAGES
16 #include <oneapi/dpl/execution>
17 #include <oneapi/dpl/numeric>
18 #else
19 // Check if the C++ standard library implements parallel algorithms
20 // and use this over parallelstl to avoid conflicts.
21 // Clang does not implement it so far, so checking for C++17 is not sufficient.
22 #ifdef __cpp_lib_parallel_algorithm
23 #include <execution>
24 #include <numeric>
25 #else
26 #include <pstl/execution>
27 #include <pstl/numeric>
28 // parallelstl incorrectly assumes MSVC to unconditionally implement
29 // parallel algorithms even if __cpp_lib_parallel_algorithm is not
30 // defined. So manually include the header which pulls all
31 // "pstl::execution" definitions into the "std" namespace.
32 #if __PSTL_CPP17_EXECUTION_POLICIES_PRESENT
33 #include <pstl/internal/glue_execution_defs.h>
34 #endif
35 #endif
36 #endif
37#endif
38
39// clang-format on
40
41namespace open3d {
42namespace utility {
43
44namespace {
45template <class Tin, class Tout>
46class ScanSumBody {
47 Tout sum;
48 const Tin* in;
49 Tout* const out;
50
51public:
52 ScanSumBody(Tout* out_, const Tin* in_) : sum(0), in(in_), out(out_) {}
53 Tout get_sum() const { return sum; }
54
55 template <class Tag>
56 void operator()(const tbb::blocked_range<size_t>& r, Tag) {
57 Tout temp = sum;
58 for (size_t i = r.begin(); i < r.end(); ++i) {
59 temp = temp + in[i];
60 if (Tag::is_final_scan()) out[i] = temp;
61 }
62 sum = temp;
63 }
64 ScanSumBody(ScanSumBody& b, tbb::split) : sum(0), in(b.in), out(b.out) {}
65 void reverse_join(ScanSumBody& a) { sum = a.sum + sum; }
66 void assign(ScanSumBody& b) { sum = b.sum; }
67};
68} // namespace
69
70template <class Tin, class Tout>
71void InclusivePrefixSum(const Tin* first, const Tin* last, Tout* out) {
72#if TBB_INTERFACE_VERSION >= 10000
73 // use parallelstl if we have TBB 2018 or later
74#ifdef OPEN3D_USE_ONEAPI_PACKAGES
75 std::inclusive_scan(oneapi::dpl::execution::par_unseq, first, last, out);
76
77#else
78 std::inclusive_scan(std::execution::par_unseq, first, last, out);
79#endif
80#else
81 ScanSumBody<Tin, Tout> body(out, first);
82 size_t n = std::distance(first, last);
83 tbb::parallel_scan(tbb::blocked_range<size_t>(0, n), body);
84#endif
85}
86
87} // namespace utility
88} // namespace open3d
void InclusivePrefixSum(const Tin *first, const Tin *last, Tout *out)
Definition ParallelScan.h:71
Definition PinholeCameraIntrinsic.cpp:16