119 lines
4.9 KiB
Plaintext
119 lines
4.9 KiB
Plaintext
//---------------------------------------------------------------------------//
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// Copyright (c) 2015 Jakub Szuppe <j.szuppe@gmail.com>
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//
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// Distributed under the Boost Software License, Version 1.0
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// See accompanying file LICENSE_1_0.txt or copy at
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// http://www.boost.org/LICENSE_1_0.txt
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//
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// See http://boostorg.github.com/compute for more information.
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//---------------------------------------------------------------------------//
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#ifndef BOOST_COMPUTE_ALGORITHM_REDUCE_BY_KEY_HPP
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#define BOOST_COMPUTE_ALGORITHM_REDUCE_BY_KEY_HPP
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#include <iterator>
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#include <utility>
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#include <boost/compute/command_queue.hpp>
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#include <boost/compute/device.hpp>
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#include <boost/compute/functional.hpp>
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#include <boost/compute/system.hpp>
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#include <boost/compute/algorithm/detail/reduce_by_key.hpp>
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namespace boost {
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namespace compute {
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/// The \c reduce_by_key() algorithm performs reduction for each contiguous
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/// subsequence of values determinate by equivalent keys.
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///
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/// Returns a pair of iterators at the end of the ranges [\p keys_result, keys_result_last)
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/// and [\p values_result, \p values_result_last).
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///
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/// If no function is specified, \c plus will be used.
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/// If no predicate is specified, \c equal_to will be used.
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///
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/// \param keys_first the first key
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/// \param keys_last the last key
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/// \param values_first the first input value
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/// \param keys_result iterator pointing to the key output
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/// \param values_result iterator pointing to the reduced value output
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/// \param function binary reduction function
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/// \param predicate binary predicate which returns true only if two keys are equal
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/// \param queue command queue to perform the operation
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///
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/// The \c reduce_by_key() algorithm assumes that the binary reduction function
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/// is associative. When used with non-associative functions the result may
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/// be non-deterministic and vary in precision. Notably this affects the
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/// \c plus<float>() function as floating-point addition is not associative
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/// and may produce slightly different results than a serial algorithm.
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///
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/// For example, to calculate the sum of the values for each key:
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///
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/// \snippet test/test_reduce_by_key.cpp reduce_by_key_int
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///
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/// \see reduce()
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template<class InputKeyIterator, class InputValueIterator,
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class OutputKeyIterator, class OutputValueIterator,
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class BinaryFunction, class BinaryPredicate>
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inline std::pair<OutputKeyIterator, OutputValueIterator>
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reduce_by_key(InputKeyIterator keys_first,
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InputKeyIterator keys_last,
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InputValueIterator values_first,
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OutputKeyIterator keys_result,
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OutputValueIterator values_result,
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BinaryFunction function,
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BinaryPredicate predicate,
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command_queue &queue = system::default_queue())
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{
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return detail::dispatch_reduce_by_key(keys_first, keys_last, values_first,
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keys_result, values_result,
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function, predicate,
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queue);
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}
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/// \overload
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template<class InputKeyIterator, class InputValueIterator,
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class OutputKeyIterator, class OutputValueIterator,
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class BinaryFunction>
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inline std::pair<OutputKeyIterator, OutputValueIterator>
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reduce_by_key(InputKeyIterator keys_first,
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InputKeyIterator keys_last,
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InputValueIterator values_first,
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OutputKeyIterator keys_result,
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OutputValueIterator values_result,
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BinaryFunction function,
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command_queue &queue = system::default_queue())
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{
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typedef typename std::iterator_traits<InputKeyIterator>::value_type key_type;
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return reduce_by_key(keys_first, keys_last, values_first,
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keys_result, values_result,
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function, equal_to<key_type>(),
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queue);
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}
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/// \overload
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template<class InputKeyIterator, class InputValueIterator,
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class OutputKeyIterator, class OutputValueIterator>
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inline std::pair<OutputKeyIterator, OutputValueIterator>
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reduce_by_key(InputKeyIterator keys_first,
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InputKeyIterator keys_last,
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InputValueIterator values_first,
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OutputKeyIterator keys_result,
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OutputValueIterator values_result,
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command_queue &queue = system::default_queue())
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{
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typedef typename std::iterator_traits<InputKeyIterator>::value_type key_type;
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typedef typename std::iterator_traits<InputValueIterator>::value_type value_type;
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return reduce_by_key(keys_first, keys_last, values_first,
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keys_result, values_result,
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plus<value_type>(), equal_to<key_type>(),
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queue);
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}
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} // end compute namespace
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} // end boost namespace
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#endif // BOOST_COMPUTE_ALGORITHM_REDUCE_BY_KEY_HPP
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