warp_reduce.hpp

/*
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*  Author: Anatoly Baskeheev, Itseez Ltd, (myname.mysurname@mycompany.com)
*/
 
#ifndef PCL_GPU_WARP_REDUCE
#define PCL_GPU_WARP_REDUCE
 
 
namespace pcl
{
    namespace device
    {   
        template <class T> 
        __device__ __forceinline__ T warp_reduce ( volatile T *ptr , const unsigned int tid = threadIdx.x )
        {
            const unsigned int lane = tid & 31; // index of thread in warp (0..31)
 
            if (lane < 16)
            {       
                T partial = ptr[tid];
 
                ptr[tid] = partial = partial + ptr[tid + 16];
                ptr[tid] = partial = partial + ptr[tid + 8];
                ptr[tid] = partial = partial + ptr[tid + 4];
                ptr[tid] = partial = partial + ptr[tid + 2];
                ptr[tid] = partial = partial + ptr[tid + 1];            
            }
            return ptr[tid - lane];
 
        }
    }
}
 
#endif