141 lines
4.2 KiB
Plaintext
141 lines
4.2 KiB
Plaintext
//---------------------------------------------------------------------------//
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// Copyright (c) 2014 Roshan <thisisroshansmail@gmail.com>
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//
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// Distributed under the Boost Software License, Version 1.0
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// See accompanying file LICENSE_1_0.txt or copy at
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// http://www.boost.org/LICENSE_1_0.txt
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//
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// See http://boostorg.github.com/compute for more information.
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//---------------------------------------------------------------------------//
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#ifndef BOOST_COMPUTE_ALGORITHM_DETAIL_SEARCH_N_HPP
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#define BOOST_COMPUTE_ALGORITHM_DETAIL_SEARCH_N_HPP
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#include <iterator>
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#include <boost/compute/algorithm/find.hpp>
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#include <boost/compute/container/vector.hpp>
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#include <boost/compute/detail/iterator_range_size.hpp>
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#include <boost/compute/detail/meta_kernel.hpp>
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#include <boost/compute/system.hpp>
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namespace boost {
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namespace compute {
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namespace detail {
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///
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/// \brief Search kernel class
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///
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/// Subclass of meta_kernel which is capable of performing search_n
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///
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template<class TextIterator, class OutputIterator>
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class search_n_kernel : public meta_kernel
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{
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public:
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typedef typename std::iterator_traits<TextIterator>::value_type value_type;
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search_n_kernel() : meta_kernel("search_n")
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{}
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void set_range(TextIterator t_first,
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TextIterator t_last,
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value_type value,
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size_t n,
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OutputIterator result)
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{
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m_n = n;
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m_n_arg = add_arg<uint_>("n");
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m_value = value;
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m_value_arg = add_arg<value_type>("value");
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m_count = iterator_range_size(t_first, t_last);
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m_count = m_count + 1 - m_n;
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*this <<
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"uint i = get_global_id(0);\n" <<
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"uint i1 = i;\n" <<
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"uint j;\n" <<
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"for(j = 0; j<n; j++,i++)\n" <<
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"{\n" <<
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" if(value != " << t_first[expr<uint_>("i")] << ")\n" <<
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" j = n + 1;\n" <<
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"}\n" <<
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"if(j == n)\n" <<
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result[expr<uint_>("i1")] << " = 1;\n" <<
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"else\n" <<
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result[expr<uint_>("i1")] << " = 0;\n";
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}
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event exec(command_queue &queue)
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{
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if(m_count == 0) {
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return event();
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}
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set_arg(m_n_arg, uint_(m_n));
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set_arg(m_value_arg, m_value);
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return exec_1d(queue, 0, m_count);
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}
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private:
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size_t m_n;
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size_t m_n_arg;
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size_t m_count;
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value_type m_value;
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size_t m_value_arg;
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};
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} //end detail namespace
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///
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/// \brief Substring matching algorithm
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///
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/// Searches for the first occurrence of n consecutive occurrences of
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/// value in text [t_first, t_last).
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/// \return Iterator pointing to beginning of first occurrence
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///
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/// \param t_first Iterator pointing to start of text
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/// \param t_last Iterator pointing to end of text
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/// \param n Number of times value repeats
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/// \param value Value which repeats
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/// \param queue Queue on which to execute
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///
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template<class TextIterator, class ValueType>
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inline TextIterator search_n(TextIterator t_first,
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TextIterator t_last,
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size_t n,
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ValueType value,
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command_queue &queue = system::default_queue())
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{
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// there is no need to check if pattern starts at last n - 1 indices
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vector<uint_> matching_indices(
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detail::iterator_range_size(t_first, t_last) + 1 - n,
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queue.get_context()
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);
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// search_n_kernel puts value 1 at every index in vector where pattern
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// of n values starts at
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detail::search_n_kernel<TextIterator,
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vector<uint_>::iterator> kernel;
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kernel.set_range(t_first, t_last, value, n, matching_indices.begin());
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kernel.exec(queue);
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vector<uint_>::iterator index = ::boost::compute::find(
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matching_indices.begin(), matching_indices.end(), uint_(1), queue
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);
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// pattern was not found
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if(index == matching_indices.end())
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return t_last;
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return t_first + detail::iterator_range_size(matching_indices.begin(), index);
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}
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} //end compute namespace
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} //end boost namespace
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#endif // BOOST_COMPUTE_ALGORITHM_DETAIL_SEARCH_N_HPP
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