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143 lines
3.2 KiB
143 lines
3.2 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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/*! \file binary_search.h |
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* \brief Sequential implementation of binary search algorithms. |
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*/ |
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#pragma once |
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#include <thrust/advance.h> |
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#include <thrust/distance.h> |
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#include <thrust/iterator/iterator_traits.h> |
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#include <thrust/detail/function.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 internal |
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{ |
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namespace scalar |
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{ |
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template <typename ForwardIterator, |
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typename T, |
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typename StrictWeakOrdering> |
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ForwardIterator lower_bound(ForwardIterator first, |
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ForwardIterator last, |
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const T& val, |
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StrictWeakOrdering comp) |
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{ |
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// wrap comp |
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thrust::detail::host_function< |
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StrictWeakOrdering, |
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bool |
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> wrapped_comp(comp); |
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typedef typename thrust::iterator_difference<ForwardIterator>::type difference_type; |
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difference_type len = thrust::distance(first, last); |
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while(len > 0) |
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{ |
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difference_type half = len >> 1; |
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ForwardIterator middle = first; |
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thrust::advance(middle, half); |
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if(wrapped_comp(*middle, val)) |
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{ |
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first = middle; |
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++first; |
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len = len - half - 1; |
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} |
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else |
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{ |
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len = half; |
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} |
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} |
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return first; |
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} |
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template <typename ForwardIterator, typename T, typename StrictWeakOrdering> |
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ForwardIterator upper_bound(ForwardIterator first, |
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ForwardIterator last, |
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const T& val, |
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StrictWeakOrdering comp) |
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{ |
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// wrap comp |
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thrust::detail::host_function< |
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StrictWeakOrdering, |
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bool |
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> wrapped_comp(comp); |
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typedef typename thrust::iterator_difference<ForwardIterator>::type difference_type; |
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difference_type len = thrust::distance(first, last); |
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while(len > 0) |
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{ |
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difference_type half = len >> 1; |
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ForwardIterator middle = first; |
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thrust::advance(middle, half); |
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if(wrapped_comp(val, *middle)) |
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{ |
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len = half; |
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} |
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else |
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{ |
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first = middle; |
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++first; |
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len = len - half - 1; |
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} |
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} |
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return first; |
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} |
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template <typename ForwardIterator, |
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typename T, |
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typename StrictWeakOrdering> |
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bool binary_search(ForwardIterator first, |
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ForwardIterator last, |
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const T& val, |
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StrictWeakOrdering comp) |
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{ |
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ForwardIterator iter = thrust::system::detail::internal::scalar::lower_bound(first, last, val, comp); |
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// wrap comp |
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thrust::detail::host_function< |
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StrictWeakOrdering, |
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bool |
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> wrapped_comp(comp); |
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return iter != last && !wrapped_comp(val,*iter); |
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} |
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} // end namespace scalar |
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} // end namespace internal |
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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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