boost/compute/algorithm/detail/balanced_path.hpp
//---------------------------------------------------------------------------// // Copyright (c) 2014 Roshan <thisisroshansmail@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_DETAIL_BALANCED_PATH_HPP #define BOOST_COMPUTE_ALGORITHM_DETAIL_BALANCED_PATH_HPP #include <iterator> #include <boost/compute/algorithm/find_if.hpp> #include <boost/compute/container/vector.hpp> #include <boost/compute/detail/iterator_range_size.hpp> #include <boost/compute/detail/meta_kernel.hpp> #include <boost/compute/lambda.hpp> #include <boost/compute/system.hpp> namespace boost { namespace compute { namespace detail { /// /// \brief Balanced Path kernel class /// /// Subclass of meta_kernel to break two sets into tiles according /// to their balanced path. /// class balanced_path_kernel : public meta_kernel { public: unsigned int tile_size; balanced_path_kernel() : meta_kernel("balanced_path") { tile_size = 4; } template<class InputIterator1, class InputIterator2, class OutputIterator1, class OutputIterator2, class Compare> void set_range(InputIterator1 first1, InputIterator1 last1, InputIterator2 first2, InputIterator2 last2, OutputIterator1 result_a, OutputIterator2 result_b, Compare comp) { typedef typename std::iterator_traits<InputIterator1>::value_type value_type; m_a_count = iterator_range_size(first1, last1); m_a_count_arg = add_arg<uint_>("a_count"); m_b_count = iterator_range_size(first2, last2); m_b_count_arg = add_arg<uint_>("b_count"); *this << "uint i = get_global_id(0);\n" << "uint target = (i+1)*" << tile_size << ";\n" << "uint start = max(convert_int(0),convert_int(target)-convert_int(b_count));\n" << "uint end = min(target,a_count);\n" << "uint a_index, b_index;\n" << "while(start<end)\n" << "{\n" << " a_index = (start + end)/2;\n" << " b_index = target - a_index - 1;\n" << " if(!(" << comp(first2[expr<uint_>("b_index")], first1[expr<uint_>("a_index")]) << "))\n" << " start = a_index + 1;\n" << " else end = a_index;\n" << "}\n" << "a_index = start;\n" << "b_index = target - start;\n" << "if(b_index < b_count)\n" << "{\n" << " " << decl<const value_type>("x") << " = " << first2[expr<uint_>("b_index")] << ";\n" << " uint a_start = 0, a_end = a_index, a_mid;\n" << " uint b_start = 0, b_end = b_index, b_mid;\n" << " while(a_start<a_end)\n" << " {\n" << " a_mid = (a_start + a_end)/2;\n" << " if(" << comp(first1[expr<uint_>("a_mid")], expr<value_type>("x")) << ")\n" << " a_start = a_mid+1;\n" << " else a_end = a_mid;\n" << " }\n" << " while(b_start<b_end)\n" << " {\n" << " b_mid = (b_start + b_end)/2;\n" << " if(" << comp(first2[expr<uint_>("b_mid")], expr<value_type>("x")) << ")\n" << " b_start = b_mid+1;\n" << " else b_end = b_mid;\n" << " }\n" << " uint a_run = a_index - a_start;\n" << " uint b_run = b_index - b_start;\n" << " uint x_count = a_run + b_run;\n" << " uint b_advance = max(x_count / 2, x_count - a_run);\n" << " b_end = min(b_count, b_start + b_advance + 1);\n" << " uint temp_start = b_index, temp_end = b_end, temp_mid;" << " while(temp_start < temp_end)\n" << " {\n" << " temp_mid = (temp_start + temp_end + 1)/2;\n" << " if(" << comp(expr<value_type>("x"), first2[expr<uint_>("temp_mid")]) << ")\n" << " temp_end = temp_mid-1;\n" << " else temp_start = temp_mid;\n" << " }\n" << " b_run = temp_start - b_start + 1;\n" << " b_advance = min(b_advance, b_run);\n" << " uint a_advance = x_count - b_advance;\n" << " uint star = convert_uint((a_advance == b_advance + 1) " << "&& (b_advance < b_run));\n" << " a_index = a_start + a_advance;\n" << " b_index = target - a_index + star;\n" << "}\n" << result_a[expr<uint_>("i")] << " = a_index;\n" << result_b[expr<uint_>("i")] << " = b_index;\n"; } template<class InputIterator1, class InputIterator2, class OutputIterator1, class OutputIterator2> void set_range(InputIterator1 first1, InputIterator1 last1, InputIterator2 first2, InputIterator2 last2, OutputIterator1 result_a, OutputIterator2 result_b) { typedef typename std::iterator_traits<InputIterator1>::value_type value_type; ::boost::compute::less<value_type> less_than; set_range(first1, last1, first2, last2, result_a, result_b, less_than); } event exec(command_queue &queue) { if((m_a_count + m_b_count)/tile_size == 0) { return event(); } set_arg(m_a_count_arg, uint_(m_a_count)); set_arg(m_b_count_arg, uint_(m_b_count)); return exec_1d(queue, 0, (m_a_count + m_b_count)/tile_size); } private: size_t m_a_count; size_t m_a_count_arg; size_t m_b_count; size_t m_b_count_arg; }; } //end detail namespace } //end compute namespace } //end boost namespace #endif // BOOST_COMPUTE_ALGORITHM_DETAIL_BALANCED_PATH_HPP