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/******************************************************************************
* Copyright (c) 2016, NVIDIA CORPORATION. All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are met:
* * Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* * Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* * Neither the name of the NVIDIA CORPORATION nor the
* names of its contributors may be used to endorse or promote products
* derived from this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL NVIDIA CORPORATION BE LIABLE FOR ANY
* DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
* (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
* LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
* ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
* SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*
******************************************************************************/
#pragma once
#include <thrust/detail/config.h>
#if THRUST_DEVICE_COMPILER == THRUST_DEVICE_COMPILER_NVCC
#include <thrust/system/cuda/config.h>
#include <thrust/system/cuda/detail/execution_policy.h>
#include <thrust/detail/minmax.h>
#include <thrust/distance.h>
THRUST_NAMESPACE_BEGIN
namespace cuda_cub {
// XXX forward declare to circumvent circular depedency
template <class Derived,
class InputIt,
class Predicate>
InputIt __host__ __device__
find_if(execution_policy<Derived>& policy,
InputIt first,
InputIt last,
Predicate predicate);
template <class Derived,
class InputIt,
class Predicate>
InputIt __host__ __device__
find_if_not(execution_policy<Derived>& policy,
InputIt first,
InputIt last,
Predicate predicate);
template <class Derived,
class InputIt,
class T>
InputIt __host__ __device__
find(execution_policy<Derived> &policy,
InputIt first,
InputIt last,
T const& value);
}; // namespace cuda_cub
THRUST_NAMESPACE_END
#include <thrust/system/cuda/detail/reduce.h>
#include <thrust/iterator/zip_iterator.h>
THRUST_NAMESPACE_BEGIN
namespace cuda_cub {
namespace __find_if {
template <typename TupleType>
struct functor
{
THRUST_DEVICE_FUNCTION 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;
}
}
};
} // namespace __find_if
template <class Derived,
class InputIt,
class Size,
class Predicate>
InputIt __host__ __device__
find_if_n(execution_policy<Derived>& policy,
InputIt first,
Size num_items,
Predicate predicate)
{
typedef typename thrust::tuple<bool,Size> result_type;
// empty sequence
if(num_items == 0) return first;
// this implementation breaks up the sequence into separate intervals
// in an attempt to early-out as soon as a value is found
//
// XXX compose find_if from a look-back prefix scan algorithm
// and abort kernel when the first element is found
// TODO incorporate sizeof(InputType) into interval_threshold and round to multiple of 32
const Size interval_threshold = 1 << 20;
const Size interval_size = (thrust::min)(interval_threshold, num_items);
// force transform_iterator output to bool
typedef transform_input_iterator_t<bool,
InputIt,
Predicate>
XfrmIterator;
typedef thrust::tuple<XfrmIterator,
counting_iterator_t<Size> >
IteratorTuple;
typedef thrust::zip_iterator<IteratorTuple> ZipIterator;
IteratorTuple iter_tuple =
thrust::make_tuple(XfrmIterator(first, predicate),
counting_iterator_t<Size>(0));
ZipIterator begin = thrust::make_zip_iterator(iter_tuple);
ZipIterator end = begin + num_items;
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 = reduce(policy,
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 + num_items;
}
template <class Derived,
class InputIt,
class Predicate>
InputIt __host__ __device__
find_if(execution_policy<Derived>& policy,
InputIt first,
InputIt last,
Predicate predicate)
{
return cuda_cub::find_if_n(policy, first, thrust::distance(first,last), predicate);
}
template <class Derived,
class InputIt,
class Predicate>
InputIt __host__ __device__
find_if_not(execution_policy<Derived>& policy,
InputIt first,
InputIt last,
Predicate predicate)
{
return cuda_cub::find_if(policy, first, last, thrust::detail::not1(predicate));
}
template <class Derived,
class InputIt,
class T>
InputIt __host__ __device__
find(execution_policy<Derived> &policy,
InputIt first,
InputIt last,
T const& value)
{
using thrust::placeholders::_1;
return cuda_cub::find_if(policy,
first,
last,
_1 == value);
}
} // namespace cuda_cub
THRUST_NAMESPACE_END
#endif
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