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