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+//---------------------------------------------------------------------------//
+// Copyright (c) 2013 Kyle Lutz <kyle.r.lutz@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_GATHER_HPP
+#define BOOST_COMPUTE_ALGORITHM_GATHER_HPP
+
+#include <boost/compute/command_queue.hpp>
+#include <boost/compute/detail/iterator_range_size.hpp>
+#include <boost/compute/detail/meta_kernel.hpp>
+#include <boost/compute/exception.hpp>
+#include <boost/compute/iterator/buffer_iterator.hpp>
+#include <boost/compute/system.hpp>
+#include <boost/compute/type_traits/type_name.hpp>
+
+namespace boost {
+namespace compute {
+namespace detail {
+
+template<class InputIterator, class MapIterator, class OutputIterator>
+class gather_kernel : public meta_kernel
+{
+public:
+ gather_kernel() : meta_kernel("gather")
+ {}
+
+ void set_range(MapIterator first,
+ MapIterator last,
+ InputIterator input,
+ OutputIterator result)
+ {
+ m_count = iterator_range_size(first, last);
+ m_offset = first.get_index();
+
+ *this <<
+ "const uint i = get_global_id(0);\n" <<
+ result[expr<uint_>("i")] << "=" <<
+ input[first[expr<uint_>("i")]] << ";\n";
+ }
+
+ event exec(command_queue &queue)
+ {
+ if(m_count == 0) {
+ return event();
+ }
+
+ return exec_1d(queue, m_offset, m_count);
+ }
+
+private:
+ size_t m_count;
+ size_t m_offset;
+};
+
+} // end detail namespace
+
+/// Copies the elements using the indices from the range [\p first, \p last)
+/// to the range beginning at \p result using the input values from the range
+/// beginning at \p input.
+///
+/// \see scatter()
+template<class InputIterator, class MapIterator, class OutputIterator>
+inline void gather(MapIterator first,
+ MapIterator last,
+ InputIterator input,
+ OutputIterator result,
+ command_queue &queue = system::default_queue())
+{
+ detail::gather_kernel<InputIterator, MapIterator, OutputIterator> kernel;
+
+ kernel.set_range(first, last, input, result);
+ kernel.exec(queue);
+}
+
+} // end compute namespace
+} // end boost namespace
+
+#endif // BOOST_COMPUTE_ALGORITHM_GATHER_HPP