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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/iterator/iterator_traits.h>
#include <thrust/iterator/detail/minimum_system.h>
#include <thrust/detail/type_traits.h>
#include <thrust/detail/type_traits/iterator/is_output_iterator.h>
#include <thrust/detail/type_traits/function_traits.h>
#include <thrust/transform.h>
#include <thrust/scatter.h>
#include <thrust/iterator/zip_iterator.h>
#include <limits>
#include <thrust/detail/internal_functional.h>
#include <thrust/scan.h>
#include <thrust/detail/temporary_array.h>
THRUST_NAMESPACE_BEGIN
namespace system
{
namespace detail
{
namespace generic
{
namespace detail
{
template <typename ValueType, typename TailFlagType, typename AssociativeOperator>
struct reduce_by_key_functor
{
AssociativeOperator binary_op;
typedef typename thrust::tuple<ValueType, TailFlagType> result_type;
__host__ __device__
reduce_by_key_functor(AssociativeOperator _binary_op) : binary_op(_binary_op) {}
__host__ __device__
result_type operator()(result_type a, result_type b)
{
return result_type(thrust::get<1>(b) ? thrust::get<0>(b) : binary_op(thrust::get<0>(a), thrust::get<0>(b)),
thrust::get<1>(a) | thrust::get<1>(b));
}
};
} // end namespace detail
template<typename ExecutionPolicy,
typename InputIterator1,
typename InputIterator2,
typename OutputIterator1,
typename OutputIterator2,
typename BinaryPredicate,
typename BinaryFunction>
__host__ __device__
thrust::pair<OutputIterator1,OutputIterator2>
reduce_by_key(thrust::execution_policy<ExecutionPolicy> &exec,
InputIterator1 keys_first,
InputIterator1 keys_last,
InputIterator2 values_first,
OutputIterator1 keys_output,
OutputIterator2 values_output,
BinaryPredicate binary_pred,
BinaryFunction binary_op)
{
typedef typename thrust::iterator_traits<InputIterator1>::difference_type difference_type;
typedef unsigned int FlagType; // TODO use difference_type
// Use the input iterator's value type per https://wg21.link/P0571
using ValueType = typename thrust::iterator_value<InputIterator2>::type;
if (keys_first == keys_last)
return thrust::make_pair(keys_output, values_output);
// input size
difference_type n = keys_last - keys_first;
InputIterator2 values_last = values_first + n;
// compute head flags
thrust::detail::temporary_array<FlagType,ExecutionPolicy> head_flags(exec, n);
thrust::transform(exec, keys_first, keys_last - 1, keys_first + 1, head_flags.begin() + 1, thrust::detail::not2(binary_pred));
head_flags[0] = 1;
// compute tail flags
thrust::detail::temporary_array<FlagType,ExecutionPolicy> tail_flags(exec, n); //COPY INSTEAD OF TRANSFORM
thrust::transform(exec, keys_first, keys_last - 1, keys_first + 1, tail_flags.begin(), thrust::detail::not2(binary_pred));
tail_flags[n-1] = 1;
// scan the values by flag
thrust::detail::temporary_array<ValueType,ExecutionPolicy> scanned_values(exec, n);
thrust::detail::temporary_array<FlagType,ExecutionPolicy> scanned_tail_flags(exec, n);
thrust::inclusive_scan
(exec,
thrust::make_zip_iterator(thrust::make_tuple(values_first, head_flags.begin())),
thrust::make_zip_iterator(thrust::make_tuple(values_last, head_flags.end())),
thrust::make_zip_iterator(thrust::make_tuple(scanned_values.begin(), scanned_tail_flags.begin())),
detail::reduce_by_key_functor<ValueType, FlagType, BinaryFunction>(binary_op));
thrust::exclusive_scan(exec, tail_flags.begin(), tail_flags.end(), scanned_tail_flags.begin(), FlagType(0), thrust::plus<FlagType>());
// number of unique keys
FlagType N = scanned_tail_flags[n - 1] + 1;
// scatter the keys and accumulated values
thrust::scatter_if(exec, keys_first, keys_last, scanned_tail_flags.begin(), head_flags.begin(), keys_output);
thrust::scatter_if(exec, scanned_values.begin(), scanned_values.end(), scanned_tail_flags.begin(), tail_flags.begin(), values_output);
return thrust::make_pair(keys_output + N, values_output + N);
} // end reduce_by_key()
template<typename ExecutionPolicy,
typename InputIterator1,
typename InputIterator2,
typename OutputIterator1,
typename OutputIterator2>
__host__ __device__
thrust::pair<OutputIterator1,OutputIterator2>
reduce_by_key(thrust::execution_policy<ExecutionPolicy> &exec,
InputIterator1 keys_first,
InputIterator1 keys_last,
InputIterator2 values_first,
OutputIterator1 keys_output,
OutputIterator2 values_output)
{
typedef typename thrust::iterator_value<InputIterator1>::type KeyType;
// use equal_to<KeyType> as default BinaryPredicate
return thrust::reduce_by_key(exec, keys_first, keys_last, values_first, keys_output, values_output, thrust::equal_to<KeyType>());
} // end reduce_by_key()
template<typename ExecutionPolicy,
typename InputIterator1,
typename InputIterator2,
typename OutputIterator1,
typename OutputIterator2,
typename BinaryPredicate>
__host__ __device__
thrust::pair<OutputIterator1,OutputIterator2>
reduce_by_key(thrust::execution_policy<ExecutionPolicy> &exec,
InputIterator1 keys_first,
InputIterator1 keys_last,
InputIterator2 values_first,
OutputIterator1 keys_output,
OutputIterator2 values_output,
BinaryPredicate binary_pred)
{
typedef typename thrust::detail::eval_if<
thrust::detail::is_output_iterator<OutputIterator2>::value,
thrust::iterator_value<InputIterator2>,
thrust::iterator_value<OutputIterator2>
>::type T;
// use plus<T> as default BinaryFunction
return thrust::reduce_by_key(exec,
keys_first, keys_last,
values_first,
keys_output,
values_output,
binary_pred,
thrust::plus<T>());
} // end reduce_by_key()
} // end namespace generic
} // end namespace detail
} // end namespace system
THRUST_NAMESPACE_END
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