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