89 lines
3.0 KiB
C++
89 lines
3.0 KiB
C++
// ----------------------------------------------------------------------------
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// - Open3D: www.open3d.org -
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// ----------------------------------------------------------------------------
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// Copyright (c) 2018-2023 www.open3d.org
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// SPDX-License-Identifier: MIT
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// ----------------------------------------------------------------------------
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#pragma once
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#include <tbb/parallel_for.h>
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#include <tbb/parallel_scan.h>
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// clang-format off
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#if TBB_INTERFACE_VERSION >= 10000
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#ifdef OPEN3D_USE_ONEAPI_PACKAGES
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#include <oneapi/dpl/execution>
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#include <oneapi/dpl/numeric>
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#else
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// Check if the C++ standard library implements parallel algorithms
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// and use this over parallelstl to avoid conflicts.
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// Clang does not implement it so far, so checking for C++17 is not sufficient.
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#ifdef __cpp_lib_parallel_algorithm
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#include <execution>
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#include <numeric>
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#else
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#include <pstl/execution>
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#include <pstl/numeric>
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// parallelstl incorrectly assumes MSVC to unconditionally implement
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// parallel algorithms even if __cpp_lib_parallel_algorithm is not
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// defined. So manually include the header which pulls all
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// "pstl::execution" definitions into the "std" namespace.
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#if __PSTL_CPP17_EXECUTION_POLICIES_PRESENT
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#include <pstl/internal/glue_execution_defs.h>
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#endif
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#endif
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#endif
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#endif
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// clang-format on
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namespace open3d {
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namespace utility {
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namespace {
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template <class Tin, class Tout>
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class ScanSumBody {
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Tout sum;
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const Tin* in;
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Tout* const out;
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public:
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ScanSumBody(Tout* out_, const Tin* in_) : sum(0), in(in_), out(out_) {}
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Tout get_sum() const { return sum; }
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template <class Tag>
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void operator()(const tbb::blocked_range<size_t>& r, Tag) {
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Tout temp = sum;
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for (size_t i = r.begin(); i < r.end(); ++i) {
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temp = temp + in[i];
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if (Tag::is_final_scan()) out[i] = temp;
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}
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sum = temp;
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}
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ScanSumBody(ScanSumBody& b, tbb::split) : sum(0), in(b.in), out(b.out) {}
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void reverse_join(ScanSumBody& a) { sum = a.sum + sum; }
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void assign(ScanSumBody& b) { sum = b.sum; }
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};
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} // namespace
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template <class Tin, class Tout>
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void InclusivePrefixSum(const Tin* first, const Tin* last, Tout* out) {
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#if TBB_INTERFACE_VERSION >= 10000
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// use parallelstl if we have TBB 2018 or later
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#ifdef OPEN3D_USE_ONEAPI_PACKAGES
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std::inclusive_scan(oneapi::dpl::execution::par_unseq, first, last, out);
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#else
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std::inclusive_scan(std::execution::par_unseq, first, last, out);
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#endif
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#else
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ScanSumBody<Tin, Tout> body(out, first);
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size_t n = std::distance(first, last);
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tbb::parallel_scan(tbb::blocked_range<size_t>(0, n), body);
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#endif
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}
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} // namespace utility
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} // namespace open3d
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