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131 lines
3.4 KiB
131 lines
3.4 KiB
/* |
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* Copyright 2008-2012 NVIDIA Corporation |
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* |
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* Licensed under the Apache License, Version 2.0 (the "License"); |
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* you may not use this file except in compliance with the License. |
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* You may obtain a copy of the License at |
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* |
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* http://www.apache.org/licenses/LICENSE-2.0 |
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* |
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* Unless required by applicable law or agreed to in writing, software |
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* distributed under the License is distributed on an "AS IS" BASIS, |
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
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* See the License for the specific language governing permissions and |
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* limitations under the License. |
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*/ |
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#pragma once |
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#include <thrust/detail/config.h> |
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#include <thrust/detail/function.h> |
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#include <thrust/detail/static_assert.h> |
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#include <thrust/iterator/iterator_traits.h> |
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#include <thrust/distance.h> |
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#include <thrust/reduce.h> |
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#include <tbb/blocked_range.h> |
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#include <tbb/parallel_reduce.h> |
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namespace thrust |
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{ |
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namespace system |
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{ |
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namespace tbb |
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{ |
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namespace detail |
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{ |
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namespace reduce_detail |
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{ |
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template<typename RandomAccessIterator, |
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typename OutputType, |
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typename BinaryFunction> |
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struct body |
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{ |
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RandomAccessIterator first; |
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OutputType sum; |
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bool first_call; // TBB can invoke operator() multiple times on the same body |
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thrust::detail::host_function<BinaryFunction,OutputType> binary_op; |
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// note: we only initalize sum with init to avoid calling OutputType's default constructor |
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body(RandomAccessIterator first, OutputType init, BinaryFunction binary_op) |
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: first(first), sum(init), first_call(true), binary_op(binary_op) |
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{} |
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// note: we only initalize sum with b.sum to avoid calling OutputType's default constructor |
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body(body& b, ::tbb::split) |
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: first(b.first), sum(b.sum), first_call(true), binary_op(b.binary_op) |
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{} |
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template <typename Size> |
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void operator()(const ::tbb::blocked_range<Size> &r) |
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{ |
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// we assume that blocked_range specifies a contiguous range of integers |
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if (r.empty()) return; // nothing to do |
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RandomAccessIterator iter = first + r.begin(); |
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OutputType temp = thrust::raw_reference_cast(*iter); |
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++iter; |
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for (Size i = r.begin() + 1; i != r.end(); ++i, ++iter) |
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temp = binary_op(temp, *iter); |
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if (first_call) |
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{ |
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// first time body has been invoked |
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first_call = false; |
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sum = temp; |
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} |
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else |
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{ |
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// body has been previously invoked, accumulate temp into sum |
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sum = binary_op(sum, temp); |
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} |
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} // end operator()() |
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void join(body& b) |
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{ |
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sum = binary_op(sum, b.sum); |
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} |
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}; // end body |
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} // end reduce_detail |
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template<typename DerivedPolicy, |
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typename InputIterator, |
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typename OutputType, |
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typename BinaryFunction> |
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OutputType reduce(execution_policy<DerivedPolicy> &exec, |
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InputIterator begin, |
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InputIterator end, |
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OutputType init, |
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BinaryFunction binary_op) |
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{ |
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typedef typename thrust::iterator_difference<InputIterator>::type Size; |
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Size n = thrust::distance(begin, end); |
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if (n == 0) |
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{ |
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return init; |
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} |
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else |
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{ |
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typedef typename reduce_detail::body<InputIterator,OutputType,BinaryFunction> Body; |
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Body reduce_body(begin, init, binary_op); |
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::tbb::parallel_reduce(::tbb::blocked_range<Size>(0,n), reduce_body); |
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return binary_op(init, reduce_body.sum); |
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} |
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} |
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} // end namespace detail |
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} // end namespace tbb |
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} // end namespace system |
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} // end namespace thrust |
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