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Diffstat (limited to 'boost/compute/algorithm/search_n.hpp')
-rw-r--r-- | boost/compute/algorithm/search_n.hpp | 140 |
1 files changed, 140 insertions, 0 deletions
diff --git a/boost/compute/algorithm/search_n.hpp b/boost/compute/algorithm/search_n.hpp new file mode 100644 index 0000000000..9e03111bb0 --- /dev/null +++ b/boost/compute/algorithm/search_n.hpp @@ -0,0 +1,140 @@ +//---------------------------------------------------------------------------// +// 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_SEARCH_N_HPP +#define BOOST_COMPUTE_ALGORITHM_DETAIL_SEARCH_N_HPP + +#include <iterator> + +#include <boost/compute/algorithm/find.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/system.hpp> + +namespace boost { +namespace compute { +namespace detail { + +/// +/// \brief Search kernel class +/// +/// Subclass of meta_kernel which is capable of performing search_n +/// +template<class TextIterator, class OutputIterator> +class search_n_kernel : public meta_kernel +{ +public: + typedef typename std::iterator_traits<TextIterator>::value_type value_type; + + search_n_kernel() : meta_kernel("search_n") + {} + + void set_range(TextIterator t_first, + TextIterator t_last, + value_type value, + size_t n, + OutputIterator result) + { + m_n = n; + m_n_arg = add_arg<uint_>("n"); + + m_value = value; + m_value_arg = add_arg<value_type>("value"); + + m_count = iterator_range_size(t_first, t_last); + m_count = m_count + 1 - m_n; + + *this << + "uint i = get_global_id(0);\n" << + "uint i1 = i;\n" << + "uint j;\n" << + "for(j = 0; j<n; j++,i++)\n" << + "{\n" << + " if(value != " << t_first[expr<uint_>("i")] << ")\n" << + " j = n + 1;\n" << + "}\n" << + "if(j == n)\n" << + result[expr<uint_>("i1")] << " = 1;\n" << + "else\n" << + result[expr<uint_>("i1")] << " = 0;\n"; + } + + event exec(command_queue &queue) + { + if(m_count == 0) { + return event(); + } + + set_arg(m_n_arg, uint_(m_n)); + set_arg(m_value_arg, m_value); + + return exec_1d(queue, 0, m_count); + } + +private: + size_t m_n; + size_t m_n_arg; + size_t m_count; + value_type m_value; + size_t m_value_arg; +}; + +} //end detail namespace + +/// +/// \brief Substring matching algorithm +/// +/// Searches for the first occurrence of n consecutive occurrences of +/// value in text [t_first, t_last). +/// \return Iterator pointing to beginning of first occurrence +/// +/// \param t_first Iterator pointing to start of text +/// \param t_last Iterator pointing to end of text +/// \param n Number of times value repeats +/// \param value Value which repeats +/// \param queue Queue on which to execute +/// +template<class TextIterator, class ValueType> +inline TextIterator search_n(TextIterator t_first, + TextIterator t_last, + size_t n, + ValueType value, + command_queue &queue = system::default_queue()) +{ + // there is no need to check if pattern starts at last n - 1 indices + vector<uint_> matching_indices( + detail::iterator_range_size(t_first, t_last) + 1 - n, + queue.get_context() + ); + + // search_n_kernel puts value 1 at every index in vector where pattern + // of n values starts at + detail::search_n_kernel<TextIterator, + vector<uint_>::iterator> kernel; + + kernel.set_range(t_first, t_last, value, n, matching_indices.begin()); + kernel.exec(queue); + + vector<uint_>::iterator index = ::boost::compute::find( + matching_indices.begin(), matching_indices.end(), uint_(1), queue + ); + + // pattern was not found + if(index == matching_indices.end()) + return t_last; + + return t_first + detail::iterator_range_size(matching_indices.begin(), index); +} + +} //end compute namespace +} //end boost namespace + +#endif // BOOST_COMPUTE_ALGORITHM_DETAIL_SEARCH_N_HPP |