bitonic_sort.hpp

/*
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*  Author: Anatoly Baskeheev, Itseez Ltd, (myname.mysurname@mycompany.com)
*/
 
#ifndef PCL_GPU_BITONIC_SORT_WARP_HPP
#define PCL_GPU_BITONIC_SORT_WARP_HPP
 
namespace pcl
{
    namespace device
    {
        template<typename T>    
        __device__ __forceinline__ void swap(T& a, T& b) { T t = a; a = b; b = t; }
 
        template<typename V, typename K>
        __device__ __forceinline__ void bitonicSortWarp(volatile K* keys, volatile V* vals, unsigned int dir = 1)
        {
            const unsigned int arrayLength = 64;   
            unsigned int lane = threadIdx.x & 31;
 
            for(unsigned int size = 2; size < arrayLength; size <<= 1)
            {
                //Bitonic merge
                unsigned int ddd = dir ^ ( (lane & (size / 2)) != 0 );
 
                for(unsigned int stride = size / 2; stride > 0; stride >>= 1)
                {            
                    unsigned int pos = 2 * lane - (lane & (stride - 1));
 
                    if ( (keys[pos] > keys[pos + stride]) == ddd )
                    {
                        swap(keys[pos], keys[pos + stride]);
                        swap(vals[pos], vals[pos + stride]);
                    }            
                }
            }
 
            //ddd == dir for the last bitonic merge step
            for(unsigned int stride = arrayLength / 2; stride > 0; stride >>= 1)
            {        
                unsigned int pos = 2 * lane - (lane & (stride - 1));
 
                if ( (keys[pos] > keys[pos + stride]) == dir )
                {
                    swap(keys[pos], keys[pos + stride]);
                    swap(vals[pos], vals[pos + stride]);
                }     
            }
        }
 
    }
}
 
#endif /* PCL_GPU_BITONIC_SORT_WARP_HPP */