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/*
* Copyright 2008-2013 NVIDIA Corporation
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
/*! \file binary_search.h
* \brief Sequential implementation of binary search algorithms.
*/
#pragma once
#include <thrust/detail/config.h>
#include <thrust/advance.h>
#include <thrust/distance.h>
#include <thrust/iterator/iterator_traits.h>
#include <thrust/detail/function.h>
THRUST_NAMESPACE_BEGIN
namespace system
{
namespace detail
{
namespace sequential
{
__thrust_exec_check_disable__
template<typename DerivedPolicy,
typename ForwardIterator,
typename T,
typename StrictWeakOrdering>
__host__ __device__
ForwardIterator lower_bound(sequential::execution_policy<DerivedPolicy> &,
ForwardIterator first,
ForwardIterator last,
const T& val,
StrictWeakOrdering comp)
{
// wrap comp
thrust::detail::wrapped_function<
StrictWeakOrdering,
bool
> wrapped_comp(comp);
typedef typename thrust::iterator_difference<ForwardIterator>::type difference_type;
difference_type len = thrust::distance(first, last);
while(len > 0)
{
difference_type half = len >> 1;
ForwardIterator middle = first;
thrust::advance(middle, half);
if(wrapped_comp(*middle, val))
{
first = middle;
++first;
len = len - half - 1;
}
else
{
len = half;
}
}
return first;
}
__thrust_exec_check_disable__
template<typename DerivedPolicy,
typename ForwardIterator,
typename T,
typename StrictWeakOrdering>
__host__ __device__
ForwardIterator upper_bound(sequential::execution_policy<DerivedPolicy> &,
ForwardIterator first,
ForwardIterator last,
const T& val,
StrictWeakOrdering comp)
{
// wrap comp
thrust::detail::wrapped_function<
StrictWeakOrdering,
bool
> wrapped_comp(comp);
typedef typename thrust::iterator_difference<ForwardIterator>::type difference_type;
difference_type len = thrust::distance(first, last);
while(len > 0)
{
difference_type half = len >> 1;
ForwardIterator middle = first;
thrust::advance(middle, half);
if(wrapped_comp(val, *middle))
{
len = half;
}
else
{
first = middle;
++first;
len = len - half - 1;
}
}
return first;
}
__thrust_exec_check_disable__
template<typename DerivedPolicy,
typename ForwardIterator,
typename T,
typename StrictWeakOrdering>
__host__ __device__
bool binary_search(sequential::execution_policy<DerivedPolicy> &exec,
ForwardIterator first,
ForwardIterator last,
const T& val,
StrictWeakOrdering comp)
{
ForwardIterator iter = sequential::lower_bound(exec, first, last, val, comp);
// wrap comp
thrust::detail::wrapped_function<
StrictWeakOrdering,
bool
> wrapped_comp(comp);
return iter != last && !wrapped_comp(val,*iter);
}
} // end namespace sequential
} // end namespace detail
} // end namespace system
THRUST_NAMESPACE_END
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