//---------------------------------------------------------------------------//
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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_THREADS_HPP
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#define BOOST_COMPUTE_ALGORITHM_DETAIL_COUNT_IF_WITH_THREADS_HPP
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#include <numeric>
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#include <boost/compute/detail/meta_kernel.hpp>
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#include <boost/compute/container/vector.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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class count_if_with_threads_kernel : meta_kernel
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{
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public:
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typedef typename
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std::iterator_traits<InputIterator>::value_type
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value_type;
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count_if_with_threads_kernel()
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: meta_kernel("count_if_with_threads")
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{
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}
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void set_args(InputIterator first,
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InputIterator last,
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Predicate predicate)
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{
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typedef typename std::iterator_traits<InputIterator>::value_type T;
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m_size = detail::iterator_range_size(first, last);
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m_size_arg = add_arg<const ulong_>("size");
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m_counts_arg = add_arg<ulong_ *>(memory_object::global_memory, "counts");
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*this <<
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// thread parameters
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"const uint gid = get_global_id(0);\n" <<
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"const uint block_size = size / get_global_size(0);\n" <<
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"const uint start = block_size * gid;\n" <<
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"uint end = 0;\n" <<
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"if(gid == get_global_size(0) - 1)\n" <<
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" end = size;\n" <<
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"else\n" <<
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" end = block_size * gid + block_size;\n" <<
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// count values
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"uint count = 0;\n" <<
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"for(uint i = start; i < end; i++){\n" <<
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decl<const T>("value") << "="
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<< first[expr<uint_>("i")] << ";\n" <<
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if_(predicate(var<const T>("value"))) << "{\n" <<
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"count++;\n" <<
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"}\n" <<
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"}\n" <<
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// write count
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"counts[gid] = count;\n";
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}
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size_t exec(command_queue &queue)
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{
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const device &device = queue.get_device();
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const context &context = queue.get_context();
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size_t threads = device.compute_units();
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const size_t minimum_block_size = 2048;
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if(m_size / threads < minimum_block_size){
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threads = static_cast<size_t>(
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(std::max)(
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std::ceil(float(m_size) / minimum_block_size),
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1.0f
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)
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);
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}
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// storage for counts
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::boost::compute::vector<ulong_> counts(threads, context);
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// exec kernel
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set_arg(m_size_arg, static_cast<ulong_>(m_size));
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set_arg(m_counts_arg, counts.get_buffer());
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exec_1d(queue, 0, threads, 1);
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// copy counts to the host
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std::vector<ulong_> host_counts(threads);
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::boost::compute::copy(counts.begin(), counts.end(), host_counts.begin(), queue);
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// return sum of counts
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return std::accumulate(host_counts.begin(), host_counts.end(), size_t(0));
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}
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private:
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size_t m_size;
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size_t m_size_arg;
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size_t m_counts_arg;
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};
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// counts values that match the predicate using one thread per block. this is
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// optimized for cpu-type devices with a small number of compute units.
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template<class InputIterator, class Predicate>
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inline size_t count_if_with_threads(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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count_if_with_threads_kernel<InputIterator, Predicate> kernel;
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kernel.set_args(first, last, predicate);
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return kernel.exec(queue);
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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_THREADS_HPP
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