Initial Commit
This commit is contained in:
Jordan Sherer
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//---------------------------------------------------------------------------//
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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_SCAN_ON_GPU_HPP
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#define BOOST_COMPUTE_ALGORITHM_DETAIL_SCAN_ON_GPU_HPP
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#include <boost/compute/kernel.hpp>
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#include <boost/compute/detail/meta_kernel.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/detail/iterator_range_size.hpp>
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#include <boost/compute/memory/local_buffer.hpp>
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#include <boost/compute/iterator/buffer_iterator.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 OutputIterator, class BinaryOperator>
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class local_scan_kernel : public meta_kernel
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{
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public:
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local_scan_kernel(InputIterator first,
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InputIterator last,
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OutputIterator result,
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bool exclusive,
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BinaryOperator op)
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: meta_kernel("local_scan")
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{
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typedef typename std::iterator_traits<InputIterator>::value_type T;
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(void) last;
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bool checked = true;
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m_block_sums_arg = add_arg<T *>(memory_object::global_memory, "block_sums");
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m_scratch_arg = add_arg<T *>(memory_object::local_memory, "scratch");
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m_block_size_arg = add_arg<const cl_uint>("block_size");
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m_count_arg = add_arg<const cl_uint>("count");
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m_init_value_arg = add_arg<const T>("init");
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// work-item parameters
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*this <<
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"const uint gid = get_global_id(0);\n" <<
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"const uint lid = get_local_id(0);\n";
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// check against data size
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if(checked){
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*this <<
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"if(gid < count){\n";
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}
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// copy values from input to local memory
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if(exclusive){
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*this <<
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decl<const T>("local_init") << "= (gid == 0) ? init : 0;\n" <<
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"if(lid == 0){ scratch[lid] = local_init; }\n" <<
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"else { scratch[lid] = " << first[expr<cl_uint>("gid-1")] << "; }\n";
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}
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else{
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*this <<
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"scratch[lid] = " << first[expr<cl_uint>("gid")] << ";\n";
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}
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if(checked){
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*this <<
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"}\n"
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"else {\n" <<
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" scratch[lid] = 0;\n" <<
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"}\n";
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}
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// wait for all threads to read from input
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*this <<
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"barrier(CLK_LOCAL_MEM_FENCE);\n";
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// perform scan
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*this <<
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"for(uint i = 1; i < block_size; i <<= 1){\n" <<
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" " << decl<const T>("x") << " = lid >= i ? scratch[lid-i] : 0;\n" <<
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" barrier(CLK_LOCAL_MEM_FENCE);\n" <<
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" if(lid >= i){\n" <<
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" scratch[lid] = " << op(var<T>("scratch[lid]"), var<T>("x")) << ";\n" <<
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" }\n" <<
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" barrier(CLK_LOCAL_MEM_FENCE);\n" <<
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"}\n";
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// copy results to output
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if(checked){
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*this <<
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"if(gid < count){\n";
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}
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*this <<
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result[expr<cl_uint>("gid")] << " = scratch[lid];\n";
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if(checked){
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*this << "}\n";
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}
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// store sum for the block
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if(exclusive){
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*this <<
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"if(lid == block_size - 1){\n" <<
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" block_sums[get_group_id(0)] = " <<
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op(first[expr<cl_uint>("gid")], var<T>("scratch[lid]")) <<
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";\n" <<
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"}\n";
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}
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else {
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*this <<
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"if(lid == block_size - 1){\n" <<
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" block_sums[get_group_id(0)] = scratch[lid];\n" <<
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"}\n";
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}
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}
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size_t m_block_sums_arg;
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size_t m_scratch_arg;
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size_t m_block_size_arg;
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size_t m_count_arg;
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size_t m_init_value_arg;
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};
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template<class T, class BinaryOperator>
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class write_scanned_output_kernel : public meta_kernel
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{
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public:
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write_scanned_output_kernel(BinaryOperator op)
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: meta_kernel("write_scanned_output")
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{
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bool checked = true;
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m_output_arg = add_arg<T *>(memory_object::global_memory, "output");
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m_block_sums_arg = add_arg<const T *>(memory_object::global_memory, "block_sums");
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m_count_arg = add_arg<const cl_uint>("count");
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// work-item parameters
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*this <<
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"const uint gid = get_global_id(0);\n" <<
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"const uint block_id = get_group_id(0);\n";
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// check against data size
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if(checked){
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*this << "if(gid < count){\n";
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}
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// write output
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*this <<
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"output[gid] = " <<
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op(var<T>("block_sums[block_id]"), var<T>("output[gid] ")) << ";\n";
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if(checked){
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*this << "}\n";
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}
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}
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size_t m_output_arg;
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size_t m_block_sums_arg;
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size_t m_count_arg;
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};
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template<class InputIterator>
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inline size_t pick_scan_block_size(InputIterator first, InputIterator last)
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{
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size_t count = iterator_range_size(first, last);
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if(count == 0) { return 0; }
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else if(count <= 1) { return 1; }
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else if(count <= 2) { return 2; }
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else if(count <= 4) { return 4; }
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else if(count <= 8) { return 8; }
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else if(count <= 16) { return 16; }
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else if(count <= 32) { return 32; }
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else if(count <= 64) { return 64; }
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else if(count <= 128) { return 128; }
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else { return 256; }
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}
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template<class InputIterator, class OutputIterator, class T, class BinaryOperator>
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inline OutputIterator scan_impl(InputIterator first,
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InputIterator last,
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OutputIterator result,
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bool exclusive,
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T init,
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BinaryOperator op,
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command_queue &queue)
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{
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typedef typename
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std::iterator_traits<InputIterator>::value_type
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input_type;
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typedef typename
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std::iterator_traits<InputIterator>::difference_type
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difference_type;
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typedef typename
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std::iterator_traits<OutputIterator>::value_type
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output_type;
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const context &context = queue.get_context();
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const size_t count = detail::iterator_range_size(first, last);
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size_t block_size = pick_scan_block_size(first, last);
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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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::boost::compute::vector<input_type> block_sums(block_count, context);
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// zero block sums
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input_type zero;
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std::memset(&zero, 0, sizeof(input_type));
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::boost::compute::fill(block_sums.begin(), block_sums.end(), zero, queue);
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// local scan
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local_scan_kernel<InputIterator, OutputIterator, BinaryOperator>
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local_scan_kernel(first, last, result, exclusive, op);
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::boost::compute::kernel kernel = local_scan_kernel.compile(context);
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kernel.set_arg(local_scan_kernel.m_scratch_arg, local_buffer<input_type>(block_size));
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kernel.set_arg(local_scan_kernel.m_block_sums_arg, block_sums);
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kernel.set_arg(local_scan_kernel.m_block_size_arg, static_cast<cl_uint>(block_size));
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kernel.set_arg(local_scan_kernel.m_count_arg, static_cast<cl_uint>(count));
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kernel.set_arg(local_scan_kernel.m_init_value_arg, static_cast<output_type>(init));
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queue.enqueue_1d_range_kernel(kernel,
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0,
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block_count * block_size,
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block_size);
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// inclusive scan block sums
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if(block_count > 1){
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scan_impl(block_sums.begin(),
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block_sums.end(),
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block_sums.begin(),
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false,
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init,
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op,
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queue
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);
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}
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// add block sums to each block
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if(block_count > 1){
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write_scanned_output_kernel<input_type, BinaryOperator>
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write_output_kernel(op);
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kernel = write_output_kernel.compile(context);
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kernel.set_arg(write_output_kernel.m_output_arg, result.get_buffer());
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kernel.set_arg(write_output_kernel.m_block_sums_arg, block_sums);
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kernel.set_arg(write_output_kernel.m_count_arg, static_cast<cl_uint>(count));
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queue.enqueue_1d_range_kernel(kernel,
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block_size,
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block_count * block_size,
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block_size);
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}
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return result + static_cast<difference_type>(count);
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}
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template<class InputIterator, class OutputIterator, class T, class BinaryOperator>
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inline OutputIterator dispatch_scan(InputIterator first,
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InputIterator last,
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OutputIterator result,
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bool exclusive,
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T init,
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BinaryOperator op,
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command_queue &queue)
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{
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return scan_impl(first, last, result, exclusive, init, op, queue);
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}
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template<class InputIterator, class T, class BinaryOperator>
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inline InputIterator dispatch_scan(InputIterator first,
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InputIterator last,
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InputIterator result,
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bool exclusive,
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T init,
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BinaryOperator op,
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command_queue &queue)
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{
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typedef typename std::iterator_traits<InputIterator>::value_type value_type;
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if(first == result){
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// scan input in-place
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const context &context = queue.get_context();
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// make a temporary copy the input
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size_t count = iterator_range_size(first, last);
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vector<value_type> tmp(count, context);
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copy(first, last, tmp.begin(), queue);
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// scan from temporary values
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return scan_impl(tmp.begin(), tmp.end(), first, exclusive, init, op, queue);
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}
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else {
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// scan input to output
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return scan_impl(first, last, result, exclusive, init, op, queue);
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}
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}
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template<class InputIterator, class OutputIterator, class T, class BinaryOperator>
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inline OutputIterator scan_on_gpu(InputIterator first,
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InputIterator last,
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OutputIterator result,
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bool exclusive,
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T init,
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BinaryOperator op,
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command_queue &queue)
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{
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if(first == last){
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return result;
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}
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return dispatch_scan(first, last, result, exclusive, init, op, 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_SCAN_ON_GPU_HPP
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