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240 lines
9.4 KiB
240 lines
9.4 KiB
![]()
11 years ago
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/*
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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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#include <thrust/detail/config.h>
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#include <thrust/system/detail/generic/scan_by_key.h>
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#include <thrust/functional.h>
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#include <thrust/transform.h>
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#include <thrust/replace.h>
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#include <thrust/iterator/zip_iterator.h>
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#include <thrust/iterator/iterator_traits.h>
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#include <thrust/detail/temporary_array.h>
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#include <thrust/detail/internal_functional.h>
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#include <thrust/scan.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 detail
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{
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namespace generic
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{
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namespace detail
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{
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template <typename OutputType, typename HeadFlagType, typename AssociativeOperator>
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struct segmented_scan_functor
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{
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AssociativeOperator binary_op;
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typedef typename thrust::tuple<OutputType, HeadFlagType> result_type;
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__host__ __device__
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segmented_scan_functor(AssociativeOperator _binary_op) : binary_op(_binary_op) {}
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__host__ __device__
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result_type operator()(result_type a, result_type b)
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{
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return result_type(thrust::get<1>(b) ? thrust::get<0>(b) : binary_op(thrust::get<0>(a), thrust::get<0>(b)),
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thrust::get<1>(a) | thrust::get<1>(b));
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}
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};
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} // end namespace detail
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template<typename DerivedPolicy,
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typename InputIterator1,
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typename InputIterator2,
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typename OutputIterator>
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OutputIterator inclusive_scan_by_key(thrust::execution_policy<DerivedPolicy> &exec,
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InputIterator1 first1,
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InputIterator1 last1,
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InputIterator2 first2,
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OutputIterator result)
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{
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typedef typename thrust::iterator_traits<InputIterator1>::value_type InputType1;
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return thrust::inclusive_scan_by_key(exec, first1, last1, first2, result, thrust::equal_to<InputType1>());
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}
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template<typename DerivedPolicy,
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typename InputIterator1,
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typename InputIterator2,
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typename OutputIterator,
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typename BinaryPredicate>
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OutputIterator inclusive_scan_by_key(thrust::execution_policy<DerivedPolicy> &exec,
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InputIterator1 first1,
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InputIterator1 last1,
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InputIterator2 first2,
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OutputIterator result,
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BinaryPredicate binary_pred)
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{
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typedef typename thrust::iterator_traits<OutputIterator>::value_type OutputType;
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return thrust::inclusive_scan_by_key(exec, first1, last1, first2, result, binary_pred, thrust::plus<OutputType>());
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}
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template<typename DerivedPolicy,
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typename InputIterator1,
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typename InputIterator2,
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typename OutputIterator,
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typename BinaryPredicate,
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typename AssociativeOperator>
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OutputIterator inclusive_scan_by_key(thrust::execution_policy<DerivedPolicy> &exec,
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InputIterator1 first1,
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InputIterator1 last1,
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InputIterator2 first2,
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OutputIterator result,
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BinaryPredicate binary_pred,
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AssociativeOperator binary_op)
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{
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typedef typename thrust::iterator_traits<OutputIterator>::value_type OutputType;
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typedef unsigned int HeadFlagType;
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const size_t n = last1 - first1;
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if(n != 0)
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{
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// compute head flags
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thrust::detail::temporary_array<HeadFlagType,DerivedPolicy> flags(exec, n);
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flags[0] = 1; thrust::transform(exec, first1, last1 - 1, first1 + 1, flags.begin() + 1, thrust::detail::not2(binary_pred));
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// scan key-flag tuples,
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// For additional details refer to Section 2 of the following paper
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// S. Sengupta, M. Harris, and M. Garland. "Efficient parallel scan algorithms for GPUs"
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// NVIDIA Technical Report NVR-2008-003, December 2008
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// http://mgarland.org/files/papers/nvr-2008-003.pdf
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thrust::inclusive_scan
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(exec,
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thrust::make_zip_iterator(thrust::make_tuple(first2, flags.begin())),
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thrust::make_zip_iterator(thrust::make_tuple(first2, flags.begin())) + n,
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thrust::make_zip_iterator(thrust::make_tuple(result, flags.begin())),
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detail::segmented_scan_functor<OutputType, HeadFlagType, AssociativeOperator>(binary_op));
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}
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return result + n;
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}
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template<typename DerivedPolicy,
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typename InputIterator1,
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typename InputIterator2,
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typename OutputIterator>
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OutputIterator exclusive_scan_by_key(thrust::execution_policy<DerivedPolicy> &exec,
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InputIterator1 first1,
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InputIterator1 last1,
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InputIterator2 first2,
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OutputIterator result)
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{
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typedef typename thrust::iterator_traits<OutputIterator>::value_type OutputType;
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return thrust::exclusive_scan_by_key(exec, first1, last1, first2, result, OutputType(0));
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}
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template<typename DerivedPolicy,
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typename InputIterator1,
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typename InputIterator2,
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typename OutputIterator,
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typename T>
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OutputIterator exclusive_scan_by_key(thrust::execution_policy<DerivedPolicy> &exec,
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InputIterator1 first1,
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InputIterator1 last1,
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InputIterator2 first2,
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OutputIterator result,
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T init)
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{
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typedef typename thrust::iterator_traits<InputIterator1>::value_type InputType1;
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return thrust::exclusive_scan_by_key(exec, first1, last1, first2, result, init, thrust::equal_to<InputType1>());
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}
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template<typename DerivedPolicy,
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typename InputIterator1,
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typename InputIterator2,
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typename OutputIterator,
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typename T,
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typename BinaryPredicate>
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OutputIterator exclusive_scan_by_key(thrust::execution_policy<DerivedPolicy> &exec,
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InputIterator1 first1,
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InputIterator1 last1,
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InputIterator2 first2,
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OutputIterator result,
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T init,
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BinaryPredicate binary_pred)
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{
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typedef typename thrust::iterator_traits<OutputIterator>::value_type OutputType;
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return thrust::exclusive_scan_by_key(exec, first1, last1, first2, result, init, binary_pred, thrust::plus<OutputType>());
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}
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template<typename DerivedPolicy,
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typename InputIterator1,
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typename InputIterator2,
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typename OutputIterator,
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typename T,
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typename BinaryPredicate,
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typename AssociativeOperator>
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OutputIterator exclusive_scan_by_key(thrust::execution_policy<DerivedPolicy> &exec,
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InputIterator1 first1,
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InputIterator1 last1,
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InputIterator2 first2,
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OutputIterator result,
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T init,
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BinaryPredicate binary_pred,
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AssociativeOperator binary_op)
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{
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typedef typename thrust::iterator_traits<OutputIterator>::value_type OutputType;
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typedef unsigned int HeadFlagType;
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const size_t n = last1 - first1;
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if(n != 0)
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{
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InputIterator2 last2 = first2 + n;
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// compute head flags
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thrust::detail::temporary_array<HeadFlagType,DerivedPolicy> flags(exec, n);
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flags[0] = 1; thrust::transform(exec, first1, last1 - 1, first1 + 1, flags.begin() + 1, thrust::detail::not2(binary_pred));
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// shift input one to the right and initialize segments with init
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thrust::detail::temporary_array<OutputType,DerivedPolicy> temp(exec, n);
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thrust::replace_copy_if(exec, first2, last2 - 1, flags.begin() + 1, temp.begin() + 1, thrust::negate<HeadFlagType>(), init);
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temp[0] = init;
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// scan key-flag tuples,
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// For additional details refer to Section 2 of the following paper
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// S. Sengupta, M. Harris, and M. Garland. "Efficient parallel scan algorithms for GPUs"
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// NVIDIA Technical Report NVR-2008-003, December 2008
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// http://mgarland.org/files/papers/nvr-2008-003.pdf
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thrust::inclusive_scan(exec,
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thrust::make_zip_iterator(thrust::make_tuple(temp.begin(), flags.begin())),
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thrust::make_zip_iterator(thrust::make_tuple(temp.begin(), flags.begin())) + n,
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thrust::make_zip_iterator(thrust::make_tuple(result, flags.begin())),
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detail::segmented_scan_functor<OutputType, HeadFlagType, AssociativeOperator>(binary_op));
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}
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return result + n;
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}
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} // end namespace generic
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} // end namespace detail
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} // end namespace system
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} // end namespace thrust
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