163 lines
5.1 KiB
Plaintext
163 lines
5.1 KiB
Plaintext
//---------------------------------------------------------------------------//
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// Copyright (c) 2013-2014 Kyle Lutz <kyle.r.lutz@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_ADJACENT_FIND_HPP
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#define BOOST_COMPUTE_ALGORITHM_ADJACENT_FIND_HPP
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#include <iterator>
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#include <boost/compute/command_queue.hpp>
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#include <boost/compute/lambda.hpp>
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#include <boost/compute/system.hpp>
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#include <boost/compute/container/detail/scalar.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/functional/operator.hpp>
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#include <boost/compute/type_traits/vector_size.hpp>
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namespace boost {
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namespace compute {
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namespace detail {
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template<class InputIterator, class Compare>
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inline InputIterator
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serial_adjacent_find(InputIterator first,
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InputIterator last,
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Compare compare,
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command_queue &queue)
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{
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if(first == last){
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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::scalar<uint_> output(context);
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detail::meta_kernel k("serial_adjacent_find");
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size_t size_arg = k.add_arg<const uint_>("size");
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size_t output_arg = k.add_arg<uint_ *>(memory_object::global_memory, "output");
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k << k.decl<uint_>("result") << " = size;\n"
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<< "for(uint i = 0; i < size - 1; i++){\n"
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<< " if(" << compare(first[k.expr<uint_>("i")],
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first[k.expr<uint_>("i+1")]) << "){\n"
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<< " result = i;\n"
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<< " break;\n"
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<< " }\n"
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<< "}\n"
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<< "*output = result;\n";
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k.set_arg<const uint_>(
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size_arg, static_cast<uint_>(detail::iterator_range_size(first, last))
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);
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k.set_arg(output_arg, output.get_buffer());
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k.exec_1d(queue, 0, 1, 1);
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return first + output.read(queue);
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}
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template<class InputIterator, class Compare>
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inline InputIterator
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adjacent_find_with_atomics(InputIterator first,
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InputIterator last,
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Compare compare,
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command_queue &queue)
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{
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if(first == last){
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return last;
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}
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const context &context = queue.get_context();
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size_t count = detail::iterator_range_size(first, last);
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// initialize output to the last index
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detail::scalar<uint_> output(context);
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output.write(static_cast<uint_>(count), queue);
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detail::meta_kernel k("adjacent_find_with_atomics");
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size_t output_arg = k.add_arg<uint_ *>(memory_object::global_memory, "output");
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k << "const uint i = get_global_id(0);\n"
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<< "if(" << compare(first[k.expr<uint_>("i")],
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first[k.expr<uint_>("i+1")]) << "){\n"
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<< " atomic_min(output, i);\n"
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<< "}\n";
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k.set_arg(output_arg, output.get_buffer());
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k.exec_1d(queue, 0, count - 1, 1);
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return first + output.read(queue);
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}
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} // end detail namespace
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/// Searches the range [\p first, \p last) for two identical adjacent
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/// elements and returns an iterator pointing to the first.
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///
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/// \param first first element in the range to search
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/// \param last last element in the range to search
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/// \param compare binary comparison function
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/// \param queue command queue to perform the operation
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///
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/// \return \c InputIteratorm to the first element which compares equal
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/// to the following element. If none are equal, returns \c last.
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///
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/// \see find(), adjacent_difference()
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template<class InputIterator, class Compare>
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inline InputIterator
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adjacent_find(InputIterator first,
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InputIterator last,
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Compare compare,
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command_queue &queue = system::default_queue())
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{
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size_t count = detail::iterator_range_size(first, last);
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if(count < 32){
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return detail::serial_adjacent_find(first, last, compare, queue);
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}
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else {
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return detail::adjacent_find_with_atomics(first, last, compare, queue);
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}
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}
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/// \overload
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template<class InputIterator>
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inline InputIterator
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adjacent_find(InputIterator first,
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InputIterator last,
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command_queue &queue = system::default_queue())
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{
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typedef typename std::iterator_traits<InputIterator>::value_type value_type;
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using ::boost::compute::lambda::_1;
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using ::boost::compute::lambda::_2;
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using ::boost::compute::lambda::all;
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if(vector_size<value_type>::value == 1){
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return ::boost::compute::adjacent_find(
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first, last, _1 == _2, queue
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);
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}
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else {
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return ::boost::compute::adjacent_find(
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first, last, all(_1 == _2), queue
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);
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}
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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_ADJACENT_FIND_HPP
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