//---------------------------------------------------------------------------//
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// Copyright (c) 2013 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_DETAIL_COUNT_IF_WITH_REDUCE_HPP
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#define BOOST_COMPUTE_ALGORITHM_DETAIL_COUNT_IF_WITH_REDUCE_HPP
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#include <boost/compute/algorithm/reduce.hpp>
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#include <boost/compute/iterator/transform_iterator.hpp>
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#include <boost/compute/types/fundamental.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 Predicate, class Arg>
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struct invoked_countable_predicate
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{
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invoked_countable_predicate(Predicate p, Arg a)
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: predicate(p), arg(a)
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{
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}
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Predicate predicate;
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Arg arg;
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};
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template<class Predicate, class Arg>
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inline meta_kernel& operator<<(meta_kernel &kernel,
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const invoked_countable_predicate<Predicate, Arg> &expr)
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{
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return kernel << "(" << expr.predicate(expr.arg) << " ? 1 : 0)";
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}
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// the countable_predicate wraps Predicate and converts its result from
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// bool to ulong so that it can be used with reduce()
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template<class Predicate>
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struct countable_predicate
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{
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typedef ulong_ result_type;
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countable_predicate(Predicate predicate)
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: m_predicate(predicate)
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{
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}
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template<class Arg>
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invoked_countable_predicate<Predicate, Arg> operator()(const Arg &arg) const
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{
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return invoked_countable_predicate<Predicate, Arg>(m_predicate, arg);
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}
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Predicate m_predicate;
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};
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// counts the number of elements matching predicate using reduce()
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template<class InputIterator, class Predicate>
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inline size_t count_if_with_reduce(InputIterator first,
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InputIterator last,
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Predicate predicate,
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command_queue &queue)
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{
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countable_predicate<Predicate> reduce_predicate(predicate);
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ulong_ count = 0;
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::boost::compute::reduce(
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::boost::compute::make_transform_iterator(first, reduce_predicate),
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::boost::compute::make_transform_iterator(last, reduce_predicate),
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&count,
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::boost::compute::plus<ulong_>(),
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queue
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);
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return static_cast<size_t>(count);
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}
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} // end detail namespace
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} // end compute namespace
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} // end boost namespace
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#endif // BOOST_COMPUTE_ALGORITHM_DETAIL_COUNT_IF_WITH_REDUCE_HPP
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