boost/compute/algorithm/reverse.hpp
//---------------------------------------------------------------------------//
// 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_REVERSE_HPP
#define BOOST_COMPUTE_ALGORITHM_REVERSE_HPP
#include <boost/static_assert.hpp>
#include <boost/compute/system.hpp>
#include <boost/compute/command_queue.hpp>
#include <boost/compute/detail/meta_kernel.hpp>
#include <boost/compute/detail/iterator_range_size.hpp>
#include <boost/compute/type_traits/is_device_iterator.hpp>
namespace boost {
namespace compute {
namespace detail {
template<class Iterator>
struct reverse_kernel : public meta_kernel
{
reverse_kernel(Iterator first, Iterator last)
: meta_kernel("reverse")
{
typedef typename std::iterator_traits<Iterator>::value_type value_type;
// store size of the range
m_size = detail::iterator_range_size(first, last);
add_set_arg<const cl_uint>("size", static_cast<const cl_uint>(m_size));
*this <<
decl<cl_uint>("i") << " = get_global_id(0);\n" <<
decl<cl_uint>("j") << " = size - get_global_id(0) - 1;\n" <<
decl<value_type>("tmp") << "=" << first[var<cl_uint>("i")] << ";\n" <<
first[var<cl_uint>("i")] << "=" << first[var<cl_uint>("j")] << ";\n" <<
first[var<cl_uint>("j")] << "= tmp;\n";
}
void exec(command_queue &queue)
{
exec_1d(queue, 0, m_size / 2);
}
size_t m_size;
};
} // end detail namespace
/// Reverses the elements in the range [\p first, \p last).
///
/// Space complexity: \Omega(1)
///
/// \see reverse_copy()
template<class Iterator>
inline void reverse(Iterator first,
Iterator last,
command_queue &queue = system::default_queue())
{
BOOST_STATIC_ASSERT(is_device_iterator<Iterator>::value);
size_t count = detail::iterator_range_size(first, last);
if(count < 2){
return;
}
detail::reverse_kernel<Iterator> kernel(first, last);
kernel.exec(queue);
}
} // end compute namespace
} // end boost namespace
#endif // BOOST_COMPUTE_ALGORITHM_REVERSE_HPP