ceph/src/boost/libs/compute/include/boost/compute/algorithm/search_n.hpp

   1 //---------------------------------------------------------------------------//
   2 // Copyright (c) 2014 Roshan <thisisroshansmail@gmail.com>
   3 //
   4 // Distributed under the Boost Software License, Version 1.0
   5 // See accompanying file LICENSE_1_0.txt or copy at
   6 // http://www.boost.org/LICENSE_1_0.txt
   7 //
   8 // See http://boostorg.github.com/compute for more information.
   9 //---------------------------------------------------------------------------//
  10
  11 #ifndef BOOST_COMPUTE_ALGORITHM_DETAIL_SEARCH_N_HPP
  12 #define BOOST_COMPUTE_ALGORITHM_DETAIL_SEARCH_N_HPP
  13
  14 #include <iterator>
  15
  16 #include <boost/compute/algorithm/find.hpp>
  17 #include <boost/compute/container/vector.hpp>
  18 #include <boost/compute/detail/iterator_range_size.hpp>
  19 #include <boost/compute/detail/meta_kernel.hpp>
  20 #include <boost/compute/system.hpp>
  21
  22 namespace boost {
  23 namespace compute {
  24 namespace detail {
  25
  26 ///
  27 /// \brief Search kernel class
  28 ///
  29 /// Subclass of meta_kernel which is capable of performing search_n
  30 ///
  31 template<class TextIterator, class OutputIterator>
  32 class search_n_kernel : public meta_kernel
  33 {
  34 public:
  35     typedef typename std::iterator_traits<TextIterator>::value_type value_type;
  36
  37     search_n_kernel() : meta_kernel("search_n")
  38     {}
  39
  40     void set_range(TextIterator t_first,
  41                    TextIterator t_last,
  42                    value_type value,
  43                    size_t n,
  44                    OutputIterator result)
  45     {
  46         m_n = n;
  47         m_n_arg = add_arg<uint_>("n");
  48
  49         m_value = value;
  50         m_value_arg = add_arg<value_type>("value");
  51
  52         m_count = iterator_range_size(t_first, t_last);
  53         m_count = m_count + 1 - m_n;
  54
  55         *this <<
  56             "uint i = get_global_id(0);\n" <<
  57             "uint i1 = i;\n" <<
  58             "uint j;\n" <<
  59             "for(j = 0; j<n; j++,i++)\n" <<
  60             "{\n" <<
  61             "   if(value != " << t_first[expr<uint_>("i")] << ")\n" <<
  62             "       j = n + 1;\n" <<
  63             "}\n" <<
  64             "if(j == n)\n" <<
  65             result[expr<uint_>("i1")] << " = 1;\n" <<
  66             "else\n" <<
  67             result[expr<uint_>("i1")] << " = 0;\n";
  68     }
  69
  70     event exec(command_queue &queue)
  71     {
  72         if(m_count == 0) {
  73             return event();
  74         }
  75
  76         set_arg(m_n_arg, uint_(m_n));
  77         set_arg(m_value_arg, m_value);
  78
  79         return exec_1d(queue, 0, m_count);
  80     }
  81
  82 private:
  83     size_t m_n;
  84     size_t m_n_arg;
  85     size_t m_count;
  86     value_type m_value;
  87     size_t m_value_arg;
  88 };
  89
  90 } //end detail namespace
  91
  92 ///
  93 /// \brief Substring matching algorithm
  94 ///
  95 /// Searches for the first occurrence of n consecutive occurrences of
  96 /// value in text [t_first, t_last).
  97 /// \return Iterator pointing to beginning of first occurrence
  98 ///
  99 /// \param t_first Iterator pointing to start of text
 100 /// \param t_last Iterator pointing to end of text
 101 /// \param n Number of times value repeats
 102 /// \param value Value which repeats
 103 /// \param queue Queue on which to execute
 104 ///
 105 template<class TextIterator, class ValueType>
 106 inline TextIterator search_n(TextIterator t_first,
 107                              TextIterator t_last,
 108                              size_t n,
 109                              ValueType value,
 110                              command_queue &queue = system::default_queue())
 111 {
 112     // there is no need to check if pattern starts at last n - 1 indices
 113     vector<uint_> matching_indices(
 114         detail::iterator_range_size(t_first, t_last) + 1 - n,
 115         queue.get_context()
 116     );
 117
 118     // search_n_kernel puts value 1 at every index in vector where pattern
 119     // of n values starts at
 120     detail::search_n_kernel<TextIterator,
 121                             vector<uint_>::iterator> kernel;
 122
 123     kernel.set_range(t_first, t_last, value, n, matching_indices.begin());
 124     kernel.exec(queue);
 125
 126     vector<uint_>::iterator index = ::boost::compute::find(
 127         matching_indices.begin(), matching_indices.end(), uint_(1), queue
 128     );
 129
 130     // pattern was not found
 131     if(index == matching_indices.end())
 132         return t_last;
 133
 134     return t_first + detail::iterator_range_size(matching_indices.begin(), index);
 135 }
 136
 137 } //end compute namespace
 138 } //end boost namespace
 139
 140 #endif // BOOST_COMPUTE_ALGORITHM_DETAIL_SEARCH_N_HPP