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/static_assert.hpp>
17
18 #include <boost/compute/algorithm/find.hpp>
19 #include <boost/compute/container/vector.hpp>
20 #include <boost/compute/detail/iterator_range_size.hpp>
21 #include <boost/compute/detail/meta_kernel.hpp>
22 #include <boost/compute/system.hpp>
23 #include <boost/compute/type_traits/is_device_iterator.hpp>
24
25 namespace boost {
26 namespace compute {
27 namespace detail {
28
29 ///
30 /// \brief Search kernel class
31 ///
32 /// Subclass of meta_kernel which is capable of performing search_n
33 ///
34 template<class TextIterator, class OutputIterator>
35 class search_n_kernel : public meta_kernel
36 {
37 public:
38 typedef typename std::iterator_traits<TextIterator>::value_type value_type;
39
search_n_kernel()40 search_n_kernel() : meta_kernel("search_n")
41 {}
42
set_range(TextIterator t_first,TextIterator t_last,value_type value,size_t n,OutputIterator result)43 void set_range(TextIterator t_first,
44 TextIterator t_last,
45 value_type value,
46 size_t n,
47 OutputIterator result)
48 {
49 m_n = n;
50 m_n_arg = add_arg<uint_>("n");
51
52 m_value = value;
53 m_value_arg = add_arg<value_type>("value");
54
55 m_count = iterator_range_size(t_first, t_last);
56 m_count = m_count + 1 - m_n;
57
58 *this <<
59 "uint i = get_global_id(0);\n" <<
60 "uint i1 = i;\n" <<
61 "uint j;\n" <<
62 "for(j = 0; j<n; j++,i++)\n" <<
63 "{\n" <<
64 " if(value != " << t_first[expr<uint_>("i")] << ")\n" <<
65 " j = n + 1;\n" <<
66 "}\n" <<
67 "if(j == n)\n" <<
68 result[expr<uint_>("i1")] << " = 1;\n" <<
69 "else\n" <<
70 result[expr<uint_>("i1")] << " = 0;\n";
71 }
72
exec(command_queue & queue)73 event exec(command_queue &queue)
74 {
75 if(m_count == 0) {
76 return event();
77 }
78
79 set_arg(m_n_arg, uint_(m_n));
80 set_arg(m_value_arg, m_value);
81
82 return exec_1d(queue, 0, m_count);
83 }
84
85 private:
86 size_t m_n;
87 size_t m_n_arg;
88 size_t m_count;
89 value_type m_value;
90 size_t m_value_arg;
91 };
92
93 } //end detail namespace
94
95 ///
96 /// \brief Substring matching algorithm
97 ///
98 /// Searches for the first occurrence of n consecutive occurrences of
99 /// value in text [t_first, t_last).
100 /// \return Iterator pointing to beginning of first occurrence
101 ///
102 /// \param t_first Iterator pointing to start of text
103 /// \param t_last Iterator pointing to end of text
104 /// \param n Number of times value repeats
105 /// \param value Value which repeats
106 /// \param queue Queue on which to execute
107 ///
108 /// Space complexity: \Omega(distance(\p t_first, \p t_last))
109 template<class TextIterator, class ValueType>
search_n(TextIterator t_first,TextIterator t_last,size_t n,ValueType value,command_queue & queue=system::default_queue ())110 inline TextIterator search_n(TextIterator t_first,
111 TextIterator t_last,
112 size_t n,
113 ValueType value,
114 command_queue &queue = system::default_queue())
115 {
116 BOOST_STATIC_ASSERT(is_device_iterator<TextIterator>::value);
117
118 // there is no need to check if pattern starts at last n - 1 indices
119 vector<uint_> matching_indices(
120 detail::iterator_range_size(t_first, t_last) + 1 - n,
121 queue.get_context()
122 );
123
124 // search_n_kernel puts value 1 at every index in vector where pattern
125 // of n values starts at
126 detail::search_n_kernel<TextIterator,
127 vector<uint_>::iterator> kernel;
128
129 kernel.set_range(t_first, t_last, value, n, matching_indices.begin());
130 kernel.exec(queue);
131
132 vector<uint_>::iterator index = ::boost::compute::find(
133 matching_indices.begin(), matching_indices.end(), uint_(1), queue
134 );
135
136 // pattern was not found
137 if(index == matching_indices.end())
138 return t_last;
139
140 return t_first + detail::iterator_range_size(matching_indices.begin(), index);
141 }
142
143 } //end compute namespace
144 } //end boost namespace
145
146 #endif // BOOST_COMPUTE_ALGORITHM_DETAIL_SEARCH_N_HPP
147