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			591 lines
		
	
	
		
			22 KiB
		
	
	
	
		
			Plaintext
		
	
	
	
	
	
| //---------------------------------------------------------------------------//
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| // Copyright (c) 2016 Jakub Szuppe <j.szuppe@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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| 
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| #ifndef BOOST_COMPUTE_ALGORITHM_DETAIL_MERGE_SORT_ON_GPU_HPP_
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| #define BOOST_COMPUTE_ALGORITHM_DETAIL_MERGE_SORT_ON_GPU_HPP_
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| 
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| #include <algorithm>
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| 
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| #include <boost/compute/kernel.hpp>
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| #include <boost/compute/program.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/memory/local_buffer.hpp>
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| #include <boost/compute/detail/meta_kernel.hpp>
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| #include <boost/compute/detail/iterator_range_size.hpp>
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| 
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| namespace boost {
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| namespace compute {
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| namespace detail {
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| 
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| template<class KeyType, class ValueType>
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| inline size_t pick_bitonic_block_sort_block_size(size_t proposed_wg,
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|                                                  size_t lmem_size,
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|                                                  bool sort_by_key)
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| {
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|     size_t n = proposed_wg;
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| 
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|     size_t lmem_required = n * sizeof(KeyType);
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|     if(sort_by_key) {
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|         lmem_required += n * sizeof(ValueType);
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|     }
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| 
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|     // try to force at least 4 work-groups of >64 elements
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|     // for better occupancy
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|     while(lmem_size < (lmem_required * 4) && (n > 64)) {
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|         n /= 2;
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|         lmem_required = n * sizeof(KeyType);
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|     }
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|     while(lmem_size < lmem_required && (n != 1)) {
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|         n /= 2;
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|         if(n < 1) n = 1;
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|         lmem_required = n * sizeof(KeyType);
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|     }
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| 
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|     if(n < 2)   { return 1; }
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|     else if(n < 4)   { return 2; }
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|     else if(n < 8)   { return 4; }
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|     else if(n < 16)  { return 8; }
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|     else if(n < 32)  { return 16; }
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|     else if(n < 64)  { return 32; }
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|     else if(n < 128) { return 64; }
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|     else if(n < 256) { return 128; }
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|     else             { return 256; }
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| }
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| 
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| 
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| /// Performs bitonic block sort according to \p compare.
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| ///
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| /// Since bitonic sort can be only performed when input size is equal to 2^n,
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| /// in this case input size is block size (\p work_group_size), we would have
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| /// to require \p count be a exact multiple of block size. That would not be
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| /// great.
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| /// Instead, bitonic sort kernel is merged with odd-even merge sort so if the
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| /// last block is not equal to 2^n (where n is some natural number) the odd-even
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| /// sort is performed for that block. That way bitonic_block_sort() works for
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| /// input of any size. Block size (\p work_group_size) still have to be equal
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| /// to 2^n.
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| ///
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| /// This is NOT stable.
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| ///
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| /// \param keys_first first key element in the range to sort
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| /// \param values_first first value element in the range to sort
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| /// \param compare comparison function for keys
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| /// \param count number of elements in the range; count > 0
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| /// \param work_group_size size of the work group, also the block size; must be
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| ///        equal to n^2 where n is natural number
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| /// \param queue command queue to perform the operation
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| template<class KeyIterator, class ValueIterator, class Compare>
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| inline size_t bitonic_block_sort(KeyIterator keys_first,
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|                                  ValueIterator values_first,
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|                                  Compare compare,
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|                                  const size_t count,
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|                                  const bool sort_by_key,
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|                                  command_queue &queue)
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| {
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|     typedef typename std::iterator_traits<KeyIterator>::value_type key_type;
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| 
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|     meta_kernel k("bitonic_block_sort");
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|     size_t count_arg = k.add_arg<const uint_>("count");
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| 
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|     size_t local_keys_arg = k.add_arg<key_type *>(memory_object::local_memory, "lkeys");
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|     size_t local_vals_arg = 0;
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|     if(sort_by_key) {
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|         local_vals_arg = k.add_arg<uchar_ *>(memory_object::local_memory, "lidx");
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|     }
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| 
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|     k <<
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|         // Work item global and local ids
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|         k.decl<const uint_>("gid") << " = get_global_id(0);\n" <<
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|         k.decl<const uint_>("lid") << " = get_local_id(0);\n";
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| 
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|     // declare my_key and my_value
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|     k <<
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|         k.decl<key_type>("my_key") << ";\n";
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|     // Instead of copying values (my_value) in local memory with keys
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|     // we save local index (uchar) and copy my_value at the end at
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|     // final index. This saves local memory.
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|     if(sort_by_key)
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|     {
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|         k <<
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|             k.decl<uchar_>("my_index") << " = (uchar)(lid);\n";
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|     }
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| 
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|     // load key
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|     k <<
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|         "if(gid < count) {\n" <<
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|             k.var<key_type>("my_key") <<  " = " <<
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|                 keys_first[k.var<const uint_>("gid")] << ";\n" <<
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|         "}\n";
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| 
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|     // load key and index to local memory
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|     k <<
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|         "lkeys[lid] = my_key;\n";
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|     if(sort_by_key)
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|     {
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|         k <<
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|             "lidx[lid] = my_index;\n";
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|     }
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|     k <<
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|         k.decl<const uint_>("offset") << " = get_group_id(0) * get_local_size(0);\n" <<
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|         k.decl<const uint_>("n") << " = min((uint)(get_local_size(0)),(count - offset));\n";
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| 
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|     // When work group size is a power of 2 bitonic sorter can be used;
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|     // otherwise, slower odd-even sort is used.
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| 
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|     k <<
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|         // check if n is power of 2
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|         "if(((n != 0) && ((n & (~n + 1)) == n))) {\n";
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| 
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|     // bitonic sort, not stable
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|     k <<
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|         // wait for keys and vals to be stored in local memory
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|         "barrier(CLK_LOCAL_MEM_FENCE);\n" <<
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| 
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|         "#pragma unroll\n" <<
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|         "for(" <<
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|             k.decl<uint_>("length") << " = 1; " <<
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|             "length < n; " <<
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|             "length <<= 1" <<
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|         ") {\n" <<
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|             // direction of sort: false -> asc, true -> desc
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|             k.decl<bool>("direction") << "= ((lid & (length<<1)) != 0);\n" <<
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|             "for(" <<
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|                 k.decl<uint_>("k") << " = length; " <<
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|                 "k > 0; " <<
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|                 "k >>= 1" <<
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|             ") {\n" <<
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| 
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|             // sibling to compare with my key
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|             k.decl<uint_>("sibling_idx") << " = lid ^ k;\n" <<
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|             k.decl<key_type>("sibling_key") << " = lkeys[sibling_idx];\n" <<
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|             k.decl<bool>("compare") << " = " <<
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|                 compare(k.var<key_type>("sibling_key"),
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|                         k.var<key_type>("my_key")) << ";\n" <<
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|             k.decl<bool>("swap") <<
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|                 " = compare ^ (sibling_idx < lid) ^ direction;\n" <<
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|             "my_key = swap ? sibling_key : my_key;\n";
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|     if(sort_by_key)
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|     {
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|         k <<
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|             "my_index = swap ? lidx[sibling_idx] : my_index;\n";
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|     }
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|     k <<
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|             "barrier(CLK_LOCAL_MEM_FENCE);\n" <<
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|             "lkeys[lid] = my_key;\n";
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|     if(sort_by_key)
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|     {
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|         k <<
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|             "lidx[lid] = my_index;\n";
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|     }
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|     k <<
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|             "barrier(CLK_LOCAL_MEM_FENCE);\n" <<
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|             "}\n" <<
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|          "}\n";
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| 
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|     // end of bitonic sort
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| 
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|     // odd-even sort, not stable
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|     k <<
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|         "}\n" <<
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|         "else { \n";
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| 
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|     k <<
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|         k.decl<bool>("lid_is_even") << " = (lid%2) == 0;\n" <<
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|         k.decl<uint_>("oddsibling_idx") << " = " <<
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|             "(lid_is_even) ? max(lid,(uint)(1)) - 1 : min(lid+1,n-1);\n" <<
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|         k.decl<uint_>("evensibling_idx") << " = " <<
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|             "(lid_is_even) ? min(lid+1,n-1) : max(lid,(uint)(1)) - 1;\n" <<
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| 
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|         // wait for keys and vals to be stored in local memory
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|         "barrier(CLK_LOCAL_MEM_FENCE);\n" <<
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| 
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|         "#pragma unroll\n" <<
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|         "for(" <<
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|             k.decl<uint_>("i") << " = 0; " <<
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|             "i < n; " <<
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|             "i++" <<
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|         ") {\n" <<
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|             k.decl<uint_>("sibling_idx") <<
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|                 " = i%2 == 0 ? evensibling_idx : oddsibling_idx;\n" <<
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|             k.decl<key_type>("sibling_key") << " = lkeys[sibling_idx];\n" <<
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|             k.decl<bool>("compare") << " = " <<
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|                 compare(k.var<key_type>("sibling_key"),
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|                         k.var<key_type>("my_key")) << ";\n" <<
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|             k.decl<bool>("swap") <<
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|                 " = compare ^ (sibling_idx < lid);\n" <<
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|             "my_key = swap ? sibling_key : my_key;\n";
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|     if(sort_by_key)
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|     {
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|         k <<
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|             "my_index = swap ? lidx[sibling_idx] : my_index;\n";
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|     }
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|     k <<
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|             "barrier(CLK_LOCAL_MEM_FENCE);\n" <<
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|             "lkeys[lid] = my_key;\n";
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|     if(sort_by_key)
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|     {
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|         k <<
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|             "lidx[lid] = my_index;\n";
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|     }
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|     k <<
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|             "barrier(CLK_LOCAL_MEM_FENCE);\n"
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|         "}\n" <<  // for
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| 
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|     "}\n"; // else
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|     // end of odd-even sort
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| 
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|     // save key and value
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|     k <<
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|         "if(gid < count) {\n" <<
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|         keys_first[k.var<const uint_>("gid")] << " = " <<
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|             k.var<key_type>("my_key") << ";\n";
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|     if(sort_by_key)
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|     {
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|         k << values_first[k.var<const uint_>("gid")] << " = " <<
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|                 values_first[k.var<const uint_>("offset + my_index")] << ";\n";
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|     }
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|     k <<
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|         // end if
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|         "}\n";
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| 
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|     const context &context = queue.get_context();
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|     const device &device = queue.get_device();
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|     ::boost::compute::kernel kernel = k.compile(context);
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| 
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|     const size_t work_group_size =
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|         pick_bitonic_block_sort_block_size<key_type, uchar_>(
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|             kernel.get_work_group_info<size_t>(
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|                 device, CL_KERNEL_WORK_GROUP_SIZE
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|             ),
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|             device.get_info<size_t>(CL_DEVICE_LOCAL_MEM_SIZE),
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|             sort_by_key
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|         );
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| 
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|     const size_t global_size =
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|         work_group_size * static_cast<size_t>(
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|             std::ceil(float(count) / work_group_size)
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|         );
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| 
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|     kernel.set_arg(count_arg, static_cast<uint_>(count));
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|     kernel.set_arg(local_keys_arg, local_buffer<key_type>(work_group_size));
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|     if(sort_by_key) {
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|         kernel.set_arg(local_vals_arg, local_buffer<uchar_>(work_group_size));
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|     }
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| 
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|     queue.enqueue_1d_range_kernel(kernel, 0, global_size, work_group_size);
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|     // return size of the block
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|     return work_group_size;
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| }
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| 
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| template<class KeyIterator, class ValueIterator, class Compare>
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| inline size_t block_sort(KeyIterator keys_first,
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|                          ValueIterator values_first,
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|                          Compare compare,
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|                          const size_t count,
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|                          const bool sort_by_key,
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|                          const bool stable,
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|                          command_queue &queue)
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| {
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|     if(stable) {
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|         // TODO: Implement stable block sort (stable odd-even merge sort)
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|         return size_t(1);
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|     }
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|     return bitonic_block_sort(
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|         keys_first, values_first,
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|         compare, count,
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|         sort_by_key, queue
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|     );
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| }
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| 
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| /// space: O(n + m); n - number of keys, m - number of values
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| template<class KeyIterator, class ValueIterator, class Compare>
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| inline void merge_blocks_on_gpu(KeyIterator keys_first,
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|                                 ValueIterator values_first,
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|                                 KeyIterator out_keys_first,
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|                                 ValueIterator out_values_first,
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|                                 Compare compare,
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|                                 const size_t count,
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|                                 const size_t block_size,
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|                                 const bool sort_by_key,
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|                                 command_queue &queue)
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| {
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|     typedef typename std::iterator_traits<KeyIterator>::value_type key_type;
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|     typedef typename std::iterator_traits<ValueIterator>::value_type value_type;
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| 
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|     meta_kernel k("merge_blocks");
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|     size_t count_arg = k.add_arg<const uint_>("count");
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|     size_t block_size_arg = k.add_arg<const uint_>("block_size");
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| 
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|     k <<
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|         // get global id
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|         k.decl<const uint_>("gid") << " = get_global_id(0);\n" <<
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|         "if(gid >= count) {\n" <<
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|             "return;\n" <<
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|         "}\n" <<
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| 
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|         k.decl<const key_type>("my_key") << " = " <<
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|             keys_first[k.var<const uint_>("gid")] << ";\n";
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| 
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|     if(sort_by_key) {
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|         k <<
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|             k.decl<const value_type>("my_value") << " = " <<
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|                 values_first[k.var<const uint_>("gid")] << ";\n";
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|     }
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| 
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|     k <<
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|         // get my block idx
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|         k.decl<const uint_>("my_block_idx") << " = gid / block_size;\n" <<
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|         k.decl<const bool>("my_block_idx_is_odd") << " = " <<
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|             "my_block_idx & 0x1;\n" <<
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| 
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|         k.decl<const uint_>("other_block_idx") << " = " <<
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|             // if(my_block_idx is odd) {} else {}
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|             "my_block_idx_is_odd ? my_block_idx - 1 : my_block_idx + 1;\n" <<
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| 
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|         // get ranges of my block and the other block
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|         // [my_block_start; my_block_end)
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|         // [other_block_start; other_block_end)
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|         k.decl<const uint_>("my_block_start") << " = " <<
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|             "min(my_block_idx * block_size, count);\n" << // including
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|         k.decl<const uint_>("my_block_end") << " = " <<
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|             "min((my_block_idx + 1) * block_size, count);\n" << // excluding
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| 
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|         k.decl<const uint_>("other_block_start") << " = " <<
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|             "min(other_block_idx * block_size, count);\n" << // including
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|         k.decl<const uint_>("other_block_end") << " = " <<
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|             "min((other_block_idx + 1) * block_size, count);\n" << // excluding
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| 
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|         // other block is empty, nothing to merge here
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|         "if(other_block_start == count){\n" <<
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|             out_keys_first[k.var<uint_>("gid")] << " = my_key;\n";
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|         if(sort_by_key) {
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|             k <<
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|                 out_values_first[k.var<uint_>("gid")] << " = my_value;\n";
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|         }
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| 
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|         k <<
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|         "return;\n" <<
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|         "}\n" <<
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| 
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|         // lower bound
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|         // left_idx - lower bound
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|         k.decl<uint_>("left_idx") << " = other_block_start;\n" <<
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|         k.decl<uint_>("right_idx") << " = other_block_end;\n" <<
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|         "while(left_idx < right_idx) {\n" <<
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|             k.decl<uint_>("mid_idx") << " = (left_idx + right_idx) / 2;\n" <<
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|             k.decl<key_type>("mid_key") << " = " <<
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|                     keys_first[k.var<const uint_>("mid_idx")] << ";\n" <<
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|             k.decl<bool>("smaller") << " = " <<
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|                 compare(k.var<key_type>("mid_key"),
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|                         k.var<key_type>("my_key")) << ";\n" <<
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|             "left_idx = smaller ? mid_idx + 1 : left_idx;\n" <<
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|             "right_idx = smaller ? right_idx :  mid_idx;\n" <<
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|         "}\n" <<
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|         // left_idx is found position in other block
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| 
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|         // if my_block is odd we need to get the upper bound
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|         "right_idx = other_block_end;\n" <<
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|         "if(my_block_idx_is_odd && left_idx != right_idx) {\n" <<
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|             k.decl<key_type>("upper_key") << " = " <<
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|                 keys_first[k.var<const uint_>("left_idx")] << ";\n" <<
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|             "while(" <<
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|                 "!(" << compare(k.var<key_type>("upper_key"),
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|                                 k.var<key_type>("my_key")) <<
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|                 ") && " <<
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|                 "!(" << compare(k.var<key_type>("my_key"),
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|                                 k.var<key_type>("upper_key")) <<
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|                 ") && " <<
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|                      "left_idx < right_idx" <<
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|                 ")" <<
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|             "{\n" <<
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|                 k.decl<uint_>("mid_idx") << " = (left_idx + right_idx) / 2;\n" <<
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|                 k.decl<key_type>("mid_key") << " = " <<
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|                     keys_first[k.var<const uint_>("mid_idx")] << ";\n" <<
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|                 k.decl<bool>("equal") << " = " <<
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|                     "!(" << compare(k.var<key_type>("mid_key"),
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|                                     k.var<key_type>("my_key")) <<
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|                     ") && " <<
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|                     "!(" << compare(k.var<key_type>("my_key"),
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|                                     k.var<key_type>("mid_key")) <<
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|                     ");\n" <<
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|                 "left_idx = equal ? mid_idx + 1 : left_idx + 1;\n" <<
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|                 "right_idx = equal ? right_idx : mid_idx;\n" <<
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|                 "upper_key = equal ? upper_key : " <<
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|                     keys_first[k.var<const uint_>("left_idx")] << ";\n" <<
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|             "}\n" <<
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|         "}\n" <<
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| 
 | |
|         k.decl<uint_>("offset") << " = 0;\n" <<
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|         "offset += gid - my_block_start;\n" <<
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|         "offset += left_idx - other_block_start;\n" <<
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|         "offset += min(my_block_start, other_block_start);\n" <<
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|         out_keys_first[k.var<uint_>("offset")] << " = my_key;\n";
 | |
|     if(sort_by_key) {
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|         k <<
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|             out_values_first[k.var<uint_>("offset")] << " = my_value;\n";
 | |
|     }
 | |
| 
 | |
|     const context &context = queue.get_context();
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|     ::boost::compute::kernel kernel = k.compile(context);
 | |
| 
 | |
|     const size_t work_group_size = (std::min)(
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|         size_t(256),
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|         kernel.get_work_group_info<size_t>(
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|             queue.get_device(), CL_KERNEL_WORK_GROUP_SIZE
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|         )
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|     );
 | |
|     const size_t global_size =
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|         work_group_size * static_cast<size_t>(
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|             std::ceil(float(count) / work_group_size)
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|         );
 | |
| 
 | |
|     kernel.set_arg(count_arg, static_cast<uint_>(count));
 | |
|     kernel.set_arg(block_size_arg, static_cast<uint_>(block_size));
 | |
|     queue.enqueue_1d_range_kernel(kernel, 0, global_size, work_group_size);
 | |
| }
 | |
| 
 | |
| template<class KeyIterator, class ValueIterator, class Compare>
 | |
| inline void merge_sort_by_key_on_gpu(KeyIterator keys_first,
 | |
|                                      KeyIterator keys_last,
 | |
|                                      ValueIterator values_first,
 | |
|                                      Compare compare,
 | |
|                                      bool stable,
 | |
|                                      command_queue &queue)
 | |
| {
 | |
|     typedef typename std::iterator_traits<KeyIterator>::value_type key_type;
 | |
|     typedef typename std::iterator_traits<ValueIterator>::value_type value_type;
 | |
| 
 | |
|     size_t count = iterator_range_size(keys_first, keys_last);
 | |
|     if(count < 2){
 | |
|         return;
 | |
|     }
 | |
| 
 | |
|     size_t block_size =
 | |
|         block_sort(
 | |
|             keys_first, values_first,
 | |
|             compare, count,
 | |
|             true /* sort_by_key */, stable /* stable */,
 | |
|             queue
 | |
|         );
 | |
| 
 | |
|     // for small input size only block sort is performed
 | |
|     if(count <= block_size) {
 | |
|         return;
 | |
|     }
 | |
| 
 | |
|     const context &context = queue.get_context();
 | |
| 
 | |
|     bool result_in_temporary_buffer = false;
 | |
|     ::boost::compute::vector<key_type> temp_keys(count, context);
 | |
|     ::boost::compute::vector<value_type> temp_values(count, context);
 | |
| 
 | |
|     for(; block_size < count; block_size *= 2) {
 | |
|         result_in_temporary_buffer = !result_in_temporary_buffer;
 | |
|         if(result_in_temporary_buffer) {
 | |
|             merge_blocks_on_gpu(keys_first, values_first,
 | |
|                                 temp_keys.begin(), temp_values.begin(),
 | |
|                                 compare, count, block_size,
 | |
|                                 true /* sort_by_key */, queue);
 | |
|         } else {
 | |
|             merge_blocks_on_gpu(temp_keys.begin(), temp_values.begin(),
 | |
|                                 keys_first, values_first,
 | |
|                                 compare, count, block_size,
 | |
|                                 true /* sort_by_key */, queue);
 | |
|         }
 | |
|     }
 | |
| 
 | |
|     if(result_in_temporary_buffer) {
 | |
|         copy_async(temp_keys.begin(), temp_keys.end(), keys_first, queue);
 | |
|         copy_async(temp_values.begin(), temp_values.end(), values_first, queue);
 | |
|     }
 | |
| }
 | |
| 
 | |
| template<class Iterator, class Compare>
 | |
| inline void merge_sort_on_gpu(Iterator first,
 | |
|                               Iterator last,
 | |
|                               Compare compare,
 | |
|                               bool stable,
 | |
|                               command_queue &queue)
 | |
| {
 | |
|     typedef typename std::iterator_traits<Iterator>::value_type key_type;
 | |
| 
 | |
|     size_t count = iterator_range_size(first, last);
 | |
|     if(count < 2){
 | |
|         return;
 | |
|     }
 | |
| 
 | |
|     Iterator dummy;
 | |
|     size_t block_size =
 | |
|         block_sort(
 | |
|             first, dummy,
 | |
|             compare, count,
 | |
|             false /* sort_by_key */, stable /* stable */,
 | |
|             queue
 | |
|         );
 | |
| 
 | |
|     // for small input size only block sort is performed
 | |
|     if(count <= block_size) {
 | |
|         return;
 | |
|     }
 | |
| 
 | |
|     const context &context = queue.get_context();
 | |
| 
 | |
|     bool result_in_temporary_buffer = false;
 | |
|     ::boost::compute::vector<key_type> temp_keys(count, context);
 | |
| 
 | |
|     for(; block_size < count; block_size *= 2) {
 | |
|         result_in_temporary_buffer = !result_in_temporary_buffer;
 | |
|         if(result_in_temporary_buffer) {
 | |
|             merge_blocks_on_gpu(first, dummy, temp_keys.begin(), dummy,
 | |
|                                 compare, count, block_size,
 | |
|                                 false /* sort_by_key */, queue);
 | |
|         } else {
 | |
|             merge_blocks_on_gpu(temp_keys.begin(), dummy, first, dummy,
 | |
|                                 compare, count, block_size,
 | |
|                                 false /* sort_by_key */, queue);
 | |
|         }
 | |
|     }
 | |
| 
 | |
|     if(result_in_temporary_buffer) {
 | |
|         copy_async(temp_keys.begin(), temp_keys.end(), first, queue);
 | |
|     }
 | |
| }
 | |
| 
 | |
| template<class KeyIterator, class ValueIterator, class Compare>
 | |
| inline void merge_sort_by_key_on_gpu(KeyIterator keys_first,
 | |
|                                      KeyIterator keys_last,
 | |
|                                      ValueIterator values_first,
 | |
|                                      Compare compare,
 | |
|                                      command_queue &queue)
 | |
| {
 | |
|     merge_sort_by_key_on_gpu(
 | |
|         keys_first, keys_last, values_first,
 | |
|         compare, false /* not stable */, queue
 | |
|     );
 | |
| }
 | |
| 
 | |
| template<class Iterator, class Compare>
 | |
| inline void merge_sort_on_gpu(Iterator first,
 | |
|                               Iterator last,
 | |
|                               Compare compare,
 | |
|                               command_queue &queue)
 | |
| {
 | |
|     merge_sort_on_gpu(
 | |
|         first, last, compare, false /* not stable */, queue
 | |
|     );
 | |
| }
 | |
| 
 | |
| } // end detail namespace
 | |
| } // end compute namespace
 | |
| } // end boost namespace
 | |
| 
 | |
| #endif /* BOOST_COMPUTE_ALGORITHM_DETAIL_MERGE_SORT_ON_GPU_HPP_ */
 | 
