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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.
*/
#pragma once
#include <thrust/detail/config.h>
#include <thrust/find.h>
#include <thrust/reduce.h>
#include <thrust/tuple.h>
#include <thrust/detail/minmax.h>
#include <thrust/iterator/counting_iterator.h>
#include <thrust/iterator/transform_iterator.h>
#include <thrust/iterator/zip_iterator.h>
#include <thrust/detail/internal_functional.h>
// Contributed by Erich Elsen
THRUST_NAMESPACE_BEGIN
namespace system
{
namespace detail
{
namespace generic
{
template<typename DerivedPolicy, typename InputIterator, typename T>
__host__ __device__
InputIterator find(thrust::execution_policy<DerivedPolicy> &exec,
InputIterator first,
InputIterator last,
const T& value)
{
using thrust::placeholders::_1;
return thrust::find_if(exec, first, last, _1 == value);
} // end find()
template<typename TupleType>
struct find_if_functor
{
__host__ __device__
TupleType operator()(const TupleType& lhs, const TupleType& rhs) const
{
// select the smallest index among true results
if(thrust::get<0>(lhs) && thrust::get<0>(rhs))
{
return TupleType(true, (thrust::min)(thrust::get<1>(lhs), thrust::get<1>(rhs)));
}
else if(thrust::get<0>(lhs))
{
return lhs;
}
else
{
return rhs;
}
}
};
template<typename DerivedPolicy, typename InputIterator, typename Predicate>
__host__ __device__
InputIterator find_if(thrust::execution_policy<DerivedPolicy> &exec,
InputIterator first,
InputIterator last,
Predicate pred)
{
typedef typename thrust::iterator_traits<InputIterator>::difference_type difference_type;
typedef typename thrust::tuple<bool,difference_type> result_type;
// empty sequence
if(first == last) return last;
const difference_type n = thrust::distance(first, last);
// this implementation breaks up the sequence into separate intervals
// in an attempt to early-out as soon as a value is found
// TODO incorporate sizeof(InputType) into interval_threshold and round to multiple of 32
const difference_type interval_threshold = 1 << 20;
const difference_type interval_size = (thrust::min)(interval_threshold, n);
// force transform_iterator output to bool
typedef thrust::transform_iterator<Predicate, InputIterator, bool> XfrmIterator;
typedef thrust::tuple<XfrmIterator, thrust::counting_iterator<difference_type> > IteratorTuple;
typedef thrust::zip_iterator<IteratorTuple> ZipIterator;
IteratorTuple iter_tuple = thrust::make_tuple(XfrmIterator(first, pred),
thrust::counting_iterator<difference_type>(0));
ZipIterator begin = thrust::make_zip_iterator(iter_tuple);
ZipIterator end = begin + n;
for(ZipIterator interval_begin = begin; interval_begin < end; interval_begin += interval_size)
{
ZipIterator interval_end = interval_begin + interval_size;
if(end < interval_end)
{
interval_end = end;
} // end if
result_type result = thrust::reduce(exec,
interval_begin, interval_end,
result_type(false,interval_end - begin),
find_if_functor<result_type>());
// see if we found something
if(thrust::get<0>(result))
{
return first + thrust::get<1>(result);
}
}
//nothing was found if we reach here...
return first + n;
}
template<typename DerivedPolicy, typename InputIterator, typename Predicate>
__host__ __device__
InputIterator find_if_not(thrust::execution_policy<DerivedPolicy> &exec,
InputIterator first,
InputIterator last,
Predicate pred)
{
return thrust::find_if(exec, first, last, thrust::detail::not1(pred));
} // end find()
} // end namespace generic
} // end namespace detail
} // end namespace system
THRUST_NAMESPACE_END
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