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/**
 * \file
 * cub::WarpReduceShfl provides SHFL-based variants of parallel reduction of items partitioned across a CUDA thread warp.
 */

#pragma once

#include "../../thread/thread_operators.cuh"
#include "../../util_ptx.cuh"
#include "../../util_type.cuh"
#include "../../util_macro.cuh"
#include "../../util_namespace.cuh"

/// Optional outer namespace(s)
CUB_NS_PREFIX

/// CUB namespace
namespace cub {


/**
 * \brief WarpReduceShfl provides SHFL-based variants of parallel reduction of items partitioned across a CUDA thread warp.
 *
 * LOGICAL_WARP_THREADS must be a power-of-two
 */
template <
    typename    T,                      ///< Data type being reduced
    int         LOGICAL_WARP_THREADS,   ///< Number of threads per logical warp
    int         PTX_ARCH>               ///< The PTX compute capability for which to to specialize this collective
struct WarpReduceShfl
{
    //---------------------------------------------------------------------
    // Constants and type definitions
    //---------------------------------------------------------------------

    enum
    {
        /// Whether the logical warp size and the PTX warp size coincide
        IS_ARCH_WARP = (LOGICAL_WARP_THREADS == CUB_WARP_THREADS(PTX_ARCH)),

        /// The number of warp reduction steps
        STEPS = Log2<LOGICAL_WARP_THREADS>::VALUE,

        /// Number of logical warps in a PTX warp
        LOGICAL_WARPS = CUB_WARP_THREADS(PTX_ARCH) / LOGICAL_WARP_THREADS,
    };

    template <typename S>
    struct IsInteger
    {
        enum {
            ///Whether the data type is a small (32b or less) integer for which we can use a single SFHL instruction per exchange
            IS_SMALL_UNSIGNED = (Traits<S>::CATEGORY == UNSIGNED_INTEGER) && (sizeof(S) <= sizeof(unsigned int))
        };
    };


    // Creates a mask where the last thread in each logical warp is set
    template <int WARP, int WARPS>
    struct LastLaneMask
    {
        enum {
            BASE_MASK   = 1 << (LOGICAL_WARP_THREADS - 1),
            MASK        = (LastLaneMask<WARP + 1, WARPS>::MASK << LOGICAL_WARP_THREADS) | BASE_MASK,
        };
    };

    // Creates a mask where the last thread in each logical warp is set
    template <int WARP>
    struct LastLaneMask<WARP, WARP>
    {
        enum {
            MASK        = 1 << (LOGICAL_WARP_THREADS - 1),
        };
    };



    /// Shared memory storage layout type
    typedef NullType TempStorage;


    //---------------------------------------------------------------------
    // Thread fields
    //---------------------------------------------------------------------

    int lane_id;

    int member_mask;

    //---------------------------------------------------------------------
    // Construction
    //---------------------------------------------------------------------

    /// Constructor
    __device__ __forceinline__ WarpReduceShfl(
        TempStorage &/*temp_storage*/)
    :