137 lines
4.5 KiB
Plaintext
137 lines
4.5 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_FIND_END_HPP
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#define BOOST_COMPUTE_ALGORITHM_FIND_END_HPP
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#include <boost/compute/algorithm/copy.hpp>
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#include <boost/compute/algorithm/detail/search_all.hpp>
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#include <boost/compute/container/detail/scalar.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 Helper function for find_end
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///
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/// Basically a copy of find_if which returns last occurence
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/// instead of first occurence
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///
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template<class InputIterator, class UnaryPredicate>
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inline InputIterator find_end_helper(InputIterator first,
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InputIterator last,
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UnaryPredicate predicate,
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command_queue &queue)
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{
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typedef typename std::iterator_traits<InputIterator>::value_type value_type;
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typedef typename std::iterator_traits<InputIterator>::difference_type difference_type;
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size_t count = detail::iterator_range_size(first, last);
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if(count == 0){
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return last;
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}
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const context &context = queue.get_context();
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detail::meta_kernel k("find_end");
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size_t index_arg = k.add_arg<int *>(memory_object::global_memory, "index");
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atomic_max<int_> atomic_max_int;
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k << k.decl<const int_>("i") << " = get_global_id(0);\n"
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<< k.decl<const value_type>("value") << "="
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<< first[k.var<const int_>("i")] << ";\n"
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<< "if(" << predicate(k.var<const value_type>("value")) << "){\n"
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<< " " << atomic_max_int(k.var<int_ *>("index"), k.var<int_>("i")) << ";\n"
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<< "}\n";
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kernel kernel = k.compile(context);
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scalar<int_> index(context);
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kernel.set_arg(index_arg, index.get_buffer());
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index.write(static_cast<int_>(-1), queue);
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queue.enqueue_1d_range_kernel(kernel, 0, count, 0);
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int result = static_cast<int>(index.read(queue));
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if(result == -1){
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return last;
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}
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else {
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return first + static_cast<difference_type>(result);
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}
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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 last match of the pattern [p_first, p_last)
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/// in text [t_first, t_last).
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/// \return Iterator pointing to beginning of last occurence
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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 p_first Iterator pointing to start of pattern
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/// \param p_last Iterator pointing to end of pattern
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/// \param queue Queue on which to execute
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///
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template<class TextIterator, class PatternIterator>
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inline TextIterator find_end(TextIterator t_first,
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TextIterator t_last,
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PatternIterator p_first,
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PatternIterator p_last,
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command_queue &queue = system::default_queue())
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{
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const context &context = queue.get_context();
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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)
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+ 1 - detail::iterator_range_size(p_first, p_last),
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context
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);
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detail::search_kernel<PatternIterator,
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TextIterator,
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vector<uint_>::iterator> kernel;
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kernel.set_range(p_first, p_last, t_first, t_last, matching_indices.begin());
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kernel.exec(queue);
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using boost::compute::_1;
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vector<uint_>::iterator index =
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detail::find_end_helper(
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matching_indices.begin(),
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matching_indices.end(),
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_1 == 1,
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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_FIND_END_HPP
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