52 lines
2.1 KiB
C
52 lines
2.1 KiB
C
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// ----------------------------------------------------------------------------
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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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namespace open3d {
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namespace ml {
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namespace impl {
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/// Reduces subarrays in linear memory with the sum operation.
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/// The sum for empty subarrays is 0.
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///
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/// \param values The linear array with all values
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/// \param values_size Number of elements of \p values
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/// \param row_splits Defines the start and end of each subarray. This is
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/// an exclusive prefix sum with 0 as the first element
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/// and the length of \p values as last element.
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/// The size is \p num_arrays + 1
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/// \param num_arrays The number of subarrays
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/// \param out_sums The preallocated output array with size
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/// \p num_arrays
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template <class T>
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void ReduceSubarraysSumCPU(const T* const values,
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const size_t values_size,
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const int64_t* const row_splits,
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const size_t num_arrays,
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T* out_sums) {
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tbb::parallel_for(tbb::blocked_range<size_t>(0, num_arrays),
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[&](const tbb::blocked_range<size_t>& r) {
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for (size_t i = r.begin(); i != r.end(); ++i) {
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size_t begin_idx = row_splits[i];
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size_t end_idx = row_splits[i + 1];
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T sum = T(0);
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for (size_t j = begin_idx; j < end_idx; ++j) {
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sum += values[j];
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}
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out_sums[i] = sum;
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}
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});
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}
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} // namespace impl
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} // namespace ml
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} // namespace open3d
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