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+//---------------------------------------------------------------------------//
+// Copyright (c) 2013 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_DETAIL_RADIX_SORT_HPP
+#define BOOST_COMPUTE_ALGORITHM_DETAIL_RADIX_SORT_HPP
+
+#include <iterator>
+
+#include <boost/assert.hpp>
+#include <boost/type_traits/is_signed.hpp>
+#include <boost/type_traits/is_floating_point.hpp>
+
+#include <boost/compute/kernel.hpp>
+#include <boost/compute/program.hpp>
+#include <boost/compute/command_queue.hpp>
+#include <boost/compute/algorithm/exclusive_scan.hpp>
+#include <boost/compute/container/vector.hpp>
+#include <boost/compute/detail/iterator_range_size.hpp>
+#include <boost/compute/detail/parameter_cache.hpp>
+#include <boost/compute/type_traits/type_name.hpp>
+#include <boost/compute/type_traits/is_fundamental.hpp>
+#include <boost/compute/type_traits/is_vector_type.hpp>
+#include <boost/compute/utility/program_cache.hpp>
+
+namespace boost {
+namespace compute {
+namespace detail {
+
+// meta-function returning true if type T is radix-sortable
+template<class T>
+struct is_radix_sortable :
+ boost::mpl::and_<
+ typename ::boost::compute::is_fundamental<T>::type,
+ typename boost::mpl::not_<typename is_vector_type<T>::type>::type
+ >
+{
+};
+
+template<size_t N>
+struct radix_sort_value_type
+{
+};
+
+template<>
+struct radix_sort_value_type<1>
+{
+ typedef uchar_ type;
+};
+
+template<>
+struct radix_sort_value_type<2>
+{
+ typedef ushort_ type;
+};
+
+template<>
+struct radix_sort_value_type<4>
+{
+ typedef uint_ type;
+};
+
+template<>
+struct radix_sort_value_type<8>
+{
+ typedef ulong_ type;
+};
+
+template<typename T>
+inline const char* enable_double()
+{
+ return " -DT2_double=0";
+}
+
+template<>
+inline const char* enable_double<double>()
+{
+ return " -DT2_double=1";
+}
+
+const char radix_sort_source[] =
+"#if T2_double\n"
+"#pragma OPENCL EXTENSION cl_khr_fp64 : enable\n"
+"#endif\n"
+"#define K2_BITS (1 << K_BITS)\n"
+"#define RADIX_MASK ((((T)(1)) << K_BITS) - 1)\n"
+"#define SIGN_BIT ((sizeof(T) * CHAR_BIT) - 1)\n"
+
+"inline uint radix(const T x, const uint low_bit)\n"
+"{\n"
+"#if defined(IS_FLOATING_POINT)\n"
+" const T mask = -(x >> SIGN_BIT) | (((T)(1)) << SIGN_BIT);\n"
+" return ((x ^ mask) >> low_bit) & RADIX_MASK;\n"
+"#elif defined(IS_SIGNED)\n"
+" return ((x ^ (((T)(1)) << SIGN_BIT)) >> low_bit) & RADIX_MASK;\n"
+"#else\n"
+" return (x >> low_bit) & RADIX_MASK;\n"
+"#endif\n"
+"}\n"
+
+"__kernel void count(__global const T *input,\n"
+" const uint input_offset,\n"
+" const uint input_size,\n"
+" __global uint *global_counts,\n"
+" __global uint *global_offsets,\n"
+" __local uint *local_counts,\n"
+" const uint low_bit)\n"
+"{\n"
+ // work-item parameters
+" const uint gid = get_global_id(0);\n"
+" const uint lid = get_local_id(0);\n"
+
+ // zero local counts
+" if(lid < K2_BITS){\n"
+" local_counts[lid] = 0;\n"
+" }\n"
+" barrier(CLK_LOCAL_MEM_FENCE);\n"
+
+ // reduce local counts
+" if(gid < input_size){\n"
+" T value = input[input_offset+gid];\n"
+" uint bucket = radix(value, low_bit);\n"
+" atomic_inc(local_counts + bucket);\n"
+" }\n"
+" barrier(CLK_LOCAL_MEM_FENCE);\n"
+
+ // write block-relative offsets
+" if(lid < K2_BITS){\n"
+" global_counts[K2_BITS*get_group_id(0) + lid] = local_counts[lid];\n"
+
+ // write global offsets
+" if(get_group_id(0) == (get_num_groups(0) - 1)){\n"
+" global_offsets[lid] = local_counts[lid];\n"
+" }\n"
+" }\n"
+"}\n"
+
+"__kernel void scan(__global const uint *block_offsets,\n"
+" __global uint *global_offsets,\n"
+" const uint block_count)\n"
+"{\n"
+" __global const uint *last_block_offsets =\n"
+" block_offsets + K2_BITS * (block_count - 1);\n"
+
+ // calculate and scan global_offsets
+" uint sum = 0;\n"
+" for(uint i = 0; i < K2_BITS; i++){\n"
+" uint x = global_offsets[i] + last_block_offsets[i];\n"
+" global_offsets[i] = sum;\n"
+" sum += x;\n"
+" }\n"
+"}\n"
+
+"__kernel void scatter(__global const T *input,\n"
+" const uint input_offset,\n"
+" const uint input_size,\n"
+" const uint low_bit,\n"
+" __global const uint *counts,\n"
+" __global const uint *global_offsets,\n"
+"#ifndef SORT_BY_KEY\n"
+" __global T *output,\n"
+" const uint output_offset)\n"
+"#else\n"
+" __global T *keys_output,\n"
+" const uint keys_output_offset,\n"
+" __global T2 *values_input,\n"
+" const uint values_input_offset,\n"
+" __global T2 *values_output,\n"
+" const uint values_output_offset)\n"
+"#endif\n"
+"{\n"
+ // work-item parameters
+" const uint gid = get_global_id(0);\n"
+" const uint lid = get_local_id(0);\n"
+
+ // copy input to local memory
+" T value;\n"
+" uint bucket;\n"
+" __local uint local_input[BLOCK_SIZE];\n"
+" if(gid < input_size){\n"
+" value = input[input_offset+gid];\n"
+" bucket = radix(value, low_bit);\n"
+" local_input[lid] = bucket;\n"
+" }\n"
+
+ // copy block counts to local memory
+" __local uint local_counts[(1 << K_BITS)];\n"
+" if(lid < K2_BITS){\n"
+" local_counts[lid] = counts[get_group_id(0) * K2_BITS + lid];\n"
+" }\n"
+
+ // wait until local memory is ready
+" barrier(CLK_LOCAL_MEM_FENCE);\n"
+
+" if(gid >= input_size){\n"
+" return;\n"
+" }\n"
+
+ // get global offset
+" uint offset = global_offsets[bucket] + local_counts[bucket];\n"
+
+ // calculate local offset
+" uint local_offset = 0;\n"
+" for(uint i = 0; i < lid; i++){\n"
+" if(local_input[i] == bucket)\n"
+" local_offset++;\n"
+" }\n"
+
+"#ifndef SORT_BY_KEY\n"
+ // write value to output
+" output[output_offset + offset + local_offset] = value;\n"
+"#else\n"
+ // write key and value if doing sort_by_key
+" keys_output[keys_output_offset+offset + local_offset] = value;\n"
+" values_output[values_output_offset+offset + local_offset] =\n"
+" values_input[values_input_offset+gid];\n"
+"#endif\n"
+"}\n";
+
+template<class T, class T2>
+inline void radix_sort_impl(const buffer_iterator<T> first,
+ const buffer_iterator<T> last,
+ const buffer_iterator<T2> values_first,
+ command_queue &queue)
+{
+
+ typedef T value_type;
+ typedef typename radix_sort_value_type<sizeof(T)>::type sort_type;
+
+ const device &device = queue.get_device();
+ const context &context = queue.get_context();
+
+
+ // if we have a valid values iterator then we are doing a
+ // sort by key and have to set up the values buffer
+ bool sort_by_key = (values_first.get_buffer().get() != 0);
+
+ // load (or create) radix sort program
+ std::string cache_key =
+ std::string("__boost_radix_sort_") + type_name<value_type>();
+
+ if(sort_by_key){
+ cache_key += std::string("_with_") + type_name<T2>();
+ }
+
+ boost::shared_ptr<program_cache> cache =
+ program_cache::get_global_cache(context);
+ boost::shared_ptr<parameter_cache> parameters =
+ detail::parameter_cache::get_global_cache(device);
+
+ // sort parameters
+ const uint_ k = parameters->get(cache_key, "k", 4);
+ const uint_ k2 = 1 << k;
+ const uint_ block_size = parameters->get(cache_key, "tpb", 128);
+
+ // sort program compiler options
+ std::stringstream options;
+ options << "-DK_BITS=" << k;
+ options << " -DT=" << type_name<sort_type>();
+ options << " -DBLOCK_SIZE=" << block_size;
+
+ if(boost::is_floating_point<value_type>::value){
+ options << " -DIS_FLOATING_POINT";
+ }
+
+ if(boost::is_signed<value_type>::value){
+ options << " -DIS_SIGNED";
+ }
+
+ if(sort_by_key){
+ options << " -DSORT_BY_KEY";
+ options << " -DT2=" << type_name<T2>();
+ options << enable_double<T2>();
+ }
+
+ // load radix sort program
+ program radix_sort_program = cache->get_or_build(
+ cache_key, options.str(), radix_sort_source, context
+ );
+
+ kernel count_kernel(radix_sort_program, "count");
+ kernel scan_kernel(radix_sort_program, "scan");
+ kernel scatter_kernel(radix_sort_program, "scatter");
+
+ size_t count = detail::iterator_range_size(first, last);
+
+ uint_ block_count = static_cast<uint_>(count / block_size);
+ if(block_count * block_size != count){
+ block_count++;
+ }
+
+ // setup temporary buffers
+ vector<value_type> output(count, context);
+ vector<T2> values_output(sort_by_key ? count : 0, context);
+ vector<uint_> offsets(k2, context);
+ vector<uint_> counts(block_count * k2, context);
+
+ const buffer *input_buffer = &first.get_buffer();
+ uint_ input_offset = static_cast<uint_>(first.get_index());
+ const buffer *output_buffer = &output.get_buffer();
+ uint_ output_offset = 0;
+ const buffer *values_input_buffer = &values_first.get_buffer();
+ uint_ values_input_offset = static_cast<uint_>(values_first.get_index());
+ const buffer *values_output_buffer = &values_output.get_buffer();
+ uint_ values_output_offset = 0;
+
+ for(uint_ i = 0; i < sizeof(sort_type) * CHAR_BIT / k; i++){
+ // write counts
+ count_kernel.set_arg(0, *input_buffer);
+ count_kernel.set_arg(1, input_offset);
+ count_kernel.set_arg(2, static_cast<uint_>(count));
+ count_kernel.set_arg(3, counts);
+ count_kernel.set_arg(4, offsets);
+ count_kernel.set_arg(5, block_size * sizeof(uint_), 0);
+ count_kernel.set_arg(6, i * k);
+ queue.enqueue_1d_range_kernel(count_kernel,
+ 0,
+ block_count * block_size,
+ block_size);
+
+ // scan counts
+ if(k == 1){
+ typedef uint2_ counter_type;
+ ::boost::compute::exclusive_scan(
+ make_buffer_iterator<counter_type>(counts.get_buffer(), 0),
+ make_buffer_iterator<counter_type>(counts.get_buffer(), counts.size() / 2),
+ make_buffer_iterator<counter_type>(counts.get_buffer()),
+ queue
+ );
+ }
+ else if(k == 2){
+ typedef uint4_ counter_type;
+ ::boost::compute::exclusive_scan(
+ make_buffer_iterator<counter_type>(counts.get_buffer(), 0),
+ make_buffer_iterator<counter_type>(counts.get_buffer(), counts.size() / 4),
+ make_buffer_iterator<counter_type>(counts.get_buffer()),
+ queue
+ );
+ }
+ else if(k == 4){
+ typedef uint16_ counter_type;
+ ::boost::compute::exclusive_scan(
+ make_buffer_iterator<counter_type>(counts.get_buffer(), 0),
+ make_buffer_iterator<counter_type>(counts.get_buffer(), counts.size() / 16),
+ make_buffer_iterator<counter_type>(counts.get_buffer()),
+ queue
+ );
+ }
+ else {
+ BOOST_ASSERT(false && "unknown k");
+ break;
+ }
+
+ // scan global offsets
+ scan_kernel.set_arg(0, counts);
+ scan_kernel.set_arg(1, offsets);
+ scan_kernel.set_arg(2, block_count);
+ queue.enqueue_task(scan_kernel);
+
+ // scatter values
+ scatter_kernel.set_arg(0, *input_buffer);
+ scatter_kernel.set_arg(1, input_offset);
+ scatter_kernel.set_arg(2, static_cast<uint_>(count));
+ scatter_kernel.set_arg(3, i * k);
+ scatter_kernel.set_arg(4, counts);
+ scatter_kernel.set_arg(5, offsets);
+ scatter_kernel.set_arg(6, *output_buffer);
+ scatter_kernel.set_arg(7, output_offset);
+ if(sort_by_key){
+ scatter_kernel.set_arg(8, *values_input_buffer);
+ scatter_kernel.set_arg(9, values_input_offset);
+ scatter_kernel.set_arg(10, *values_output_buffer);
+ scatter_kernel.set_arg(11, values_output_offset);
+ }
+ queue.enqueue_1d_range_kernel(scatter_kernel,
+ 0,
+ block_count * block_size,
+ block_size);
+
+ // swap buffers
+ std::swap(input_buffer, output_buffer);
+ std::swap(values_input_buffer, values_output_buffer);
+ std::swap(input_offset, output_offset);
+ std::swap(values_input_offset, values_output_offset);
+ }
+}
+
+template<class Iterator>
+inline void radix_sort(Iterator first,
+ Iterator last,
+ command_queue &queue)
+{
+ radix_sort_impl(first, last, buffer_iterator<int>(), queue);
+}
+
+template<class KeyIterator, class ValueIterator>
+inline void radix_sort_by_key(KeyIterator keys_first,
+ KeyIterator keys_last,
+ ValueIterator values_first,
+ command_queue &queue)
+{
+ radix_sort_impl(keys_first, keys_last, values_first, queue);
+}
+
+} // end detail namespace
+} // end compute namespace
+} // end boost namespace
+
+#endif // BOOST_COMPUTE_ALGORITHM_DETAIL_RADIX_SORT_HPP
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