thread_reduce.cuh

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 * Copyright (c) 2011, Duane Merrill.  All rights reserved.
 * Copyright (c) 2011-2018, NVIDIA CORPORATION.  All rights reserved.
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#pragma once

#include "../thread/thread_operators.cuh"
#include "../util_namespace.cuh"

CUB_NS_PREFIX

namespace cub {

namespace internal {

template <
    int         LENGTH,
    typename    T,
    typename    ReductionOp>
__device__ __forceinline__ T ThreadReduce(
    T*                  input,                  
    ReductionOp         reduction_op,           
    T                   prefix,                 
    Int2Type<LENGTH>    /*length*/)
{
    T retval = prefix;

    #pragma unroll
    for (int i = 0; i < LENGTH; ++i)
        retval = reduction_op(retval, input[i]);

    return retval;
}


template <
    int         LENGTH,
    typename    T,
    typename    ReductionOp>
__device__ __forceinline__ T ThreadReduce(
    T*          input,                  
    ReductionOp reduction_op,           
    T           prefix)                 
{
    return ThreadReduce(input, reduction_op, prefix, Int2Type<LENGTH>());
}


template <
    int         LENGTH,
    typename    T,
    typename    ReductionOp>
__device__ __forceinline__ T ThreadReduce(
    T*          input,                  
    ReductionOp reduction_op)           
{
    T prefix = input[0];
    return ThreadReduce<LENGTH - 1>(input + 1, reduction_op, prefix);
}


template <
    int         LENGTH,
    typename    T,
    typename    ReductionOp>
__device__ __forceinline__ T ThreadReduce(
    T           (&input)[LENGTH],       
    ReductionOp reduction_op,           
    T           prefix)                 
{
    return ThreadReduce(input, reduction_op, prefix, Int2Type<LENGTH>());
}


template <
    int         LENGTH,
    typename    T,
    typename    ReductionOp>
__device__ __forceinline__ T ThreadReduce(
    T           (&input)[LENGTH],       
    ReductionOp reduction_op)           
{
    return ThreadReduce<LENGTH>((T*) input, reduction_op);
}


}               // internal namespace
}               // CUB namespace
CUB_NS_POSTFIX  // Optional outer namespace(s)