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106 lines
4.4 KiB
C++
106 lines
4.4 KiB
C++
//---------------------------------------------------------------------------//
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// Copyright (c) 2013 Kyle Lutz <kyle.r.lutz@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_MERGE_HPP
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#define BOOST_COMPUTE_ALGORITHM_MERGE_HPP
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#include <boost/compute/system.hpp>
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#include <boost/compute/command_queue.hpp>
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#include <boost/compute/algorithm/copy.hpp>
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#include <boost/compute/algorithm/detail/merge_with_merge_path.hpp>
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#include <boost/compute/algorithm/detail/serial_merge.hpp>
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#include <boost/compute/detail/iterator_range_size.hpp>
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#include <boost/compute/detail/parameter_cache.hpp>
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namespace boost {
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namespace compute {
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/// Merges the sorted values in the range [\p first1, \p last1) with the sorted
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/// values in the range [\p first2, last2) and stores the result in the range
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/// beginning at \p result. Values are compared using the \p comp function. If
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/// no comparision function is given, \c less is used.
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///
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/// \param first1 first element in the first range to merge
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/// \param last1 last element in the first range to merge
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/// \param first2 first element in the second range to merge
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/// \param last2 last element in the second range to merge
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/// \param result first element in the result range
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/// \param comp comparison function (by default \c less)
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/// \param queue command queue to perform the operation
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///
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/// \return \c OutputIterator to the end of the result range
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///
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/// \see inplace_merge()
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template<class InputIterator1,
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class InputIterator2,
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class OutputIterator,
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class Compare>
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inline OutputIterator merge(InputIterator1 first1,
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InputIterator1 last1,
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InputIterator2 first2,
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InputIterator2 last2,
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OutputIterator result,
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Compare comp,
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command_queue &queue = system::default_queue())
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{
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typedef typename std::iterator_traits<InputIterator1>::value_type input1_type;
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typedef typename std::iterator_traits<InputIterator2>::value_type input2_type;
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typedef typename std::iterator_traits<OutputIterator>::value_type output_type;
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const device &device = queue.get_device();
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std::string cache_key =
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std::string("__boost_merge_") + type_name<input1_type>() + "_"
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+ type_name<input2_type>() + "_" + type_name<output_type>();
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boost::shared_ptr<detail::parameter_cache> parameters =
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detail::parameter_cache::get_global_cache(device);
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// default serial merge threshold depends on device type
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size_t default_serial_merge_threshold = 32768;
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if(device.type() & device::gpu) {
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default_serial_merge_threshold = 2048;
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}
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// loading serial merge threshold parameter
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const size_t serial_merge_threshold =
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parameters->get(cache_key, "serial_merge_threshold",
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static_cast<uint_>(default_serial_merge_threshold));
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// choosing merge algorithm
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const size_t total_count =
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detail::iterator_range_size(first1, last1)
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+ detail::iterator_range_size(first2, last2);
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// for small inputs serial merge turns out to outperform
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// merge with merge path algorithm
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if(total_count <= serial_merge_threshold){
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return detail::serial_merge(first1, last1, first2, last2, result, comp, queue);
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}
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return detail::merge_with_merge_path(first1, last1, first2, last2, result, comp, queue);
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}
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/// \overload
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template<class InputIterator1, class InputIterator2, class OutputIterator>
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inline OutputIterator merge(InputIterator1 first1,
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InputIterator1 last1,
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InputIterator2 first2,
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InputIterator2 last2,
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OutputIterator result,
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command_queue &queue = system::default_queue())
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{
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typedef typename std::iterator_traits<InputIterator1>::value_type value_type;
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less<value_type> less_than;
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return merge(first1, last1, first2, last2, result, less_than, 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_MERGE_HPP
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