//---------------------------------------------------------------------------//
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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_BALLOT_HPP
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#define BOOST_COMPUTE_ALGORITHM_DETAIL_COUNT_IF_WITH_BALLOT_HPP
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#include <boost/compute/context.hpp>
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#include <boost/compute/command_queue.hpp>
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#include <boost/compute/container/vector.hpp>
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#include <boost/compute/algorithm/reduce.hpp>
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#include <boost/compute/functional/detail/nvidia_ballot.hpp>
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#include <boost/compute/functional/detail/nvidia_popcount.hpp>
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#include <boost/compute/detail/meta_kernel.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 Predicate>
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inline size_t count_if_with_ballot(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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size_t count = iterator_range_size(first, last);
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size_t block_size = 32;
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size_t block_count = count / block_size;
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if(block_count * block_size != count){
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block_count++;
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}
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const ::boost::compute::context &context = queue.get_context();
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::boost::compute::vector<uint_> counts(block_count, context);
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::boost::compute::detail::nvidia_popcount<uint_> popc;
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::boost::compute::detail::nvidia_ballot<uint_> ballot;
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meta_kernel k("count_if_with_ballot");
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k <<
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"const uint gid = get_global_id(0);\n" <<
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"bool value = false;\n" <<
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"if(gid < count)\n" <<
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" value = " << predicate(first[k.var<const uint_>("gid")]) << ";\n" <<
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"uint bits = " << ballot(k.var<const uint_>("value")) << ";\n" <<
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"if(get_local_id(0) == 0)\n" <<
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counts.begin()[k.var<uint_>("get_group_id(0)") ]
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<< " = " << popc(k.var<uint_>("bits")) << ";\n";
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k.add_set_arg<const uint_>("count", count);
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k.exec_1d(queue, 0, block_size * block_count, block_size);
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uint_ result;
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::boost::compute::reduce(
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counts.begin(),
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counts.end(),
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&result,
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queue
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);
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return result;
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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_BALLOT_HPP
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