/******************************************************************************
 * Copyright (c) 2011, Duane Merrill.  All rights reserved.
 * Copyright (c) 2011-2018, NVIDIA CORPORATION.  All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *     * Redistributions of source code must retain the above copyright
 *       notice, this list of conditions and the following disclaimer.
 *     * Redistributions in binary form must reproduce the above copyright
 *       notice, this list of conditions and the following disclaimer in the
 *       documentation and/or other materials provided with the distribution.
 *     * Neither the name of the NVIDIA CORPORATION nor the
 *       names of its contributors may be used to endorse or promote products
 *       derived from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 * DISCLAIMED. IN NO EVENT SHALL NVIDIA CORPORATION BE LIABLE FOR ANY
 * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
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 * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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/**
 * @file
 * cub::WarpScanShfl provides SHFL-based variants of parallel prefix scan of items partitioned
 * across a CUDA thread warp.
 */

#pragma once

#include <cub/config.cuh>

#if defined(_CCCL_IMPLICIT_SYSTEM_HEADER_GCC)
#  pragma GCC system_header
#elif defined(_CCCL_IMPLICIT_SYSTEM_HEADER_CLANG)
#  pragma clang system_header
#elif defined(_CCCL_IMPLICIT_SYSTEM_HEADER_MSVC)
#  pragma system_header
#endif // no system header

#include <cub/thread/thread_operators.cuh>
#include <cub/util_ptx.cuh>
#include <cub/util_type.cuh>

CUB_NAMESPACE_BEGIN

/**
 * @brief WarpScanShfl provides SHFL-based variants of parallel prefix scan of items partitioned
 *        across a CUDA thread warp.
 *
 * @tparam T
 *   Data type being scanned
 *
 * @tparam LOGICAL_WARP_THREADS
 *   Number of threads per logical warp (must be a power-of-two)
 *
 * @tparam LEGACY_PTX_ARCH
 *   The PTX compute capability for which to to specialize this collective
 */
template <typename T, int LOGICAL_WARP_THREADS, int LEGACY_PTX_ARCH = 0>
struct WarpScanShfl
{
    //---------------------------------------------------------------------
    // 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(0)),

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

        /// The 5-bit SHFL mask for logically splitting warps into sub-segments starts 8-bits up
        SHFL_C = (CUB_WARP_THREADS(0) - LOGICAL_WARP_THREADS) << 8
    };

    template <typename S>
    struct IntegerTraits
    {
        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))
        };
    };

    /// Shared memory storage layout type
    struct TempStorage {};


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

    /// Lane index in logical warp
    unsigned int lane_id;

    /// Logical warp index in 32-thread physical warp
    unsigned int warp_id;

    /// 32-thread physical warp member mask of logical warp
    unsigned int member_mask;

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

    /// Constructor
    explicit __device__ __forceinline__
    WarpScanShfl(TempStorage & /*temp_storage*/)
        : lane_id(LaneId())
        , warp_id(IS_ARCH_WARP ? 0 : (lane_id / LOGICAL_WARP_THREADS))
        , member_mask(WarpMask<LOGICAL_WARP_THREADS>(warp_id))
    {
        if (!IS_ARCH_WARP)
        {
            lane_id = lane_id % LOGICAL_WARP_THREADS;
        }
    }


    //---------------------------------------------------------------------
    // Inclusive scan steps
    //---------------------------------------------------------------------

    /**
     * @brief Inclusive prefix scan step (specialized for summation across int32 types)
     *
     * @param[in] input
     *   Calling thread's input item.
     *
     * @param[in] scan_op
     *   Binary scan operator
     *
     * @param[in] first_lane
     *   Index of first lane in segment
     *
     * @param[in] offset
     *   Up-offset to pull from
     */
    __device__ __forceinline__ int
    InclusiveScanStep(int input, cub::Sum /*scan_op*/, int first_lane, int offset)
    {
        int output;
        int shfl_c = first_lane | SHFL_C;   // Shuffle control (mask and first-lane)

        // Use predicate set from SHFL to guard against invalid peers
        asm volatile(
            "{"
            "  .reg .s32 r0;"
            "  .reg .pred p;"
            "  shfl.sync.up.b32 r0|p, %1, %2, %3, %5;"
            "  @p add.s32 r0, r0, %4;"
            "  mov.s32 %0, r0;"
            "}"
            : "=r"(output) : "r"(input), "r"(offset), "r"(shfl_c), "r"(input), "r"(member_mask));

        return output;
    }

    /**
     * @brief Inclusive prefix scan step (specialized for summation across uint32 types)
     *
     * @param[in] input
     *   Calling thread's input item
     *
     * @param[in] scan_op
     *   Binary scan operator
     *
     * @param[in] first_lane
     *   Index of first lane in segment
     *
     * @param[in] offset
     *   Up-offset to pull from
     */
    __device__ __forceinline__ unsigned int
    InclusiveScanStep(unsigned int input, cub::Sum /*scan_op*/, int first_lane, int offset)
    {
        unsigned int output;
        int shfl_c = first_lane | SHFL_C;   // Shuffle control (mask and first-lane)

        // Use predicate set from SHFL to guard against invalid peers
        asm volatile(
            "{"
            "  .reg .u32 r0;"
            "  .reg .pred p;"
            "  shfl.sync.up.b32 r0|p, %1, %2, %3, %5;"
            "  @p add.u32 r0, r0, %4;"
            "  mov.u32 %0, r0;"
            "}"
            : "=r"(output) : "r"(input), "r"(offset), "r"(shfl_c), "r"(input), "r"(member_mask));

        return output;
    }

    /**
     * @brief Inclusive prefix scan step (specialized for summation across fp32 types)
     *
     * @param[in] input
     *   Calling thread's input item
     *
     * @param[in] scan_op
     *   Binary scan operator
     *
     * @param[in] first_lane
     *   Index of first lane in segment
     *
     * @param[in] offset
     *   Up-offset to pull from
     */
    __device__ __forceinline__ float
    InclusiveScanStep(float input, cub::Sum /*scan_op*/, int first_lane, int offset)
    {
        float output;
        int shfl_c = first_lane | SHFL_C;   // Shuffle control (mask and first-lane)

        // Use predicate set from SHFL to guard against invalid peers
        asm volatile(
            "{"
            "  .reg .f32 r0;"
            "  .reg .pred p;"
            "  shfl.sync.up.b32 r0|p, %1, %2, %3, %5;"
            "  @p add.f32 r0, r0, %4;"
            "  mov.f32 %0, r0;"
            "}"
            : "=f"(output) : "f"(input), "r"(offset), "r"(shfl_c), "f"(input), "r"(member_mask));

        return output;
    }

    /**
     * @brief Inclusive prefix scan step (specialized for summation across unsigned long long types)
     *
     * @param[in]  input
     *   Calling thread's input item
     *
     * @param[in] scan_op
     *   Binary scan operator
     *
     * @param[in] first_lane
     *   Index of first lane in segment
     *
     * @param[in] offset
     *   Up-offset to pull from
     */
    __device__ __forceinline__ unsigned long long
    InclusiveScanStep(unsigned long long input, cub::Sum /*scan_op*/, int first_lane, int offset)
    {
        unsigned long long output;
        int shfl_c = first_lane | SHFL_C;   // Shuffle control (mask and first-lane)

        // Use predicate set from SHFL to guard against invalid peers
        asm volatile(
            "{"
            "  .reg .u64 r0;"
            "  .reg .u32 lo;"
            "  .reg .u32 hi;"
            "  .reg .pred p;"
            "  mov.b64 {lo, hi}, %1;"
            "  shfl.sync.up.b32 lo|p, lo, %2, %3, %5;"
            "  shfl.sync.up.b32 hi|p, hi, %2, %3, %5;"
            "  mov.b64 r0, {lo, hi};"
            "  @p add.u64 r0, r0, %4;"
            "  mov.u64 %0, r0;"
            "}"
            : "=l"(output) : "l"(input), "r"(offset), "r"(shfl_c), "l"(input), "r"(member_mask));

        return output;
    }

    /**
     * @brief Inclusive prefix scan step (specialized for summation across long long types)
     *
     * @param[in] input
     *   Calling thread's input item.
     *
     * @param[in] scan_op
     *   Binary scan operator
     *
     * @param[in] first_lane
     *   Index of first lane in segment
     *
     * @param[in] offset
     *   Up-offset to pull from
     */
    __device__ __forceinline__ long long
    InclusiveScanStep(long long input, cub::Sum /*scan_op*/, int first_lane, int offset)
    {
        long long output;
        int shfl_c = first_lane | SHFL_C;   // Shuffle control (mask and first-lane)

        // Use predicate set from SHFL to guard against invalid peers
        asm volatile(
            "{"
            "  .reg .s64 r0;"
            "  .reg .u32 lo;"
            "  .reg .u32 hi;"
            "  .reg .pred p;"
            "  mov.b64 {lo, hi}, %1;"
            "  shfl.sync.up.b32 lo|p, lo, %2, %3, %5;"
            "  shfl.sync.up.b32 hi|p, hi, %2, %3, %5;"
            "  mov.b64 r0, {lo, hi};"
            "  @p add.s64 r0, r0, %4;"
            "  mov.s64 %0, r0;"
            "}"
            : "=l"(output) : "l"(input), "r"(offset), "r"(shfl_c), "l"(input), "r"(member_mask));

        return output;
    }

    /**
     * @brief Inclusive prefix scan step (specialized for summation across fp64 types)
     *
     * @param[in] input
     *   Calling thread's input item.
     *
     * @param[in] scan_op
     *   Binary scan operator
     *
     * @param[in] first_lane
     *   Index of first lane in segment
     *
     * @param[in] offset
     *   Up-offset to pull from
     */
    __device__ __forceinline__ double
    InclusiveScanStep(double input, cub::Sum /*scan_op*/, int first_lane, int offset)
    {
        double output;
        int shfl_c = first_lane | SHFL_C;   // Shuffle control (mask and first-lane)

        // Use predicate set from SHFL to guard against invalid peers
        asm volatile(
            "{"
            "  .reg .u32 lo;"
            "  .reg .u32 hi;"
            "  .reg .pred p;"
            "  .reg .f64 r0;"
            "  mov.b64 %0, %1;"
            "  mov.b64 {lo, hi}, %1;"
            "  shfl.sync.up.b32 lo|p, lo, %2, %3, %4;"
            "  shfl.sync.up.b32 hi|p, hi, %2, %3, %4;"
            "  mov.b64 r0, {lo, hi};"
            "  @p add.f64 %0, %0, r0;"
            "}"
            : "=d"(output) : "d"(input), "r"(offset), "r"(shfl_c), "r"(member_mask));

        return output;
    }


/*
    /// Inclusive prefix scan (specialized for ReduceBySegmentOp<cub::Sum> across KeyValuePair<OffsetT, Value> types)
    template <typename Value, typename OffsetT>
    __device__ __forceinline__ KeyValuePair<OffsetT, Value>InclusiveScanStep(
        KeyValuePair<OffsetT, Value>    input,              ///< [in] Calling thread's input item.
        ReduceBySegmentOp<cub::Sum>     scan_op,            ///< [in] Binary scan operator
        int                             first_lane,         ///< [in] Index of first lane in segment
        int                             offset)             ///< [in] Up-offset to pull from
    {
        KeyValuePair<OffsetT, Value> output;

        output.value = InclusiveScanStep(input.value, cub::Sum(), first_lane, offset, Int2Type<IntegerTraits<Value>::IS_SMALL_UNSIGNED>());
        output.key = InclusiveScanStep(input.key, cub::Sum(), first_lane, offset, Int2Type<IntegerTraits<OffsetT>::IS_SMALL_UNSIGNED>());

        if (input.key > 0)
            output.value = input.value;

        return output;
    }
*/

    /**
     * @brief Inclusive prefix scan step (generic)
     *
     * @param[in] input
     *   Calling thread's input item.
     *
     * @param[in] scan_op
     *   Binary scan operator
     *
     * @param[in] first_lane
     *   Index of first lane in segment
     *
     * @param[in] offset
     *   Up-offset to pull from
     */
    template <typename _T, typename ScanOpT>
    __device__ __forceinline__ _T
    InclusiveScanStep(_T input, ScanOpT scan_op, int first_lane, int offset)
    {
        _T temp = ShuffleUp<LOGICAL_WARP_THREADS>(input, offset, first_lane, member_mask);

        // Perform scan op if from a valid peer
        _T output = scan_op(temp, input);
        if (static_cast<int>(lane_id) < first_lane + offset)
            output = input;

        return output;
    }

    /**
     * @brief Inclusive prefix scan step (specialized for small integers size 32b or less)
     *
     * @param[in] input
     *   Calling thread's input item
     *
     * @param[in] scan_op
     *   Binary scan operator
     *
     * @param[in] first_lane
     *   Index of first lane in segment
     *
     * @param[in] offset
     *   Up-offset to pull from
     *
     * @param[in] is_small_unsigned
     *   Marker type indicating whether T is a small integer
     */
    template <typename _T, typename ScanOpT>
    __device__ __forceinline__ _T InclusiveScanStep(_T input,
                                                    ScanOpT scan_op,
                                                    int first_lane,
                                                    int offset,
                                                    Int2Type<true> /*is_small_unsigned*/)
    {
        return InclusiveScanStep(input, scan_op, first_lane, offset);
    }

    /**
     * @brief Inclusive prefix scan step (specialized for types other than small integers size
     *        32b or less)
     *
     * @param[in] input
     *   Calling thread's input item.
     *
     * @param[in] scan_op
     *   Binary scan operator
     *
     * @param[in] first_lane
     *   Index of first lane in segment
     *
     * @param[in] offset
     *   Up-offset to pull from
     *
     * @param[in] is_small_unsigned
     *   Marker type indicating whether T is a small integer
     */
    template <typename _T, typename ScanOpT>
    __device__ __forceinline__ _T InclusiveScanStep(_T input,
                                                    ScanOpT scan_op,
                                                    int first_lane,
                                                    int offset,
                                                    Int2Type<false> /*is_small_unsigned*/)
    {
        return InclusiveScanStep(input, scan_op, first_lane, offset);
    }


    /******************************************************************************
     * Interface
     ******************************************************************************/

    //---------------------------------------------------------------------
    // Broadcast
    //---------------------------------------------------------------------

    /**
     * @brief Broadcast
     *
     * @param[in] input
     *   The value to broadcast
     *
     * @param[in] src_lane
     *   Which warp lane is to do the broadcasting
     */
    __device__ __forceinline__ T Broadcast(T input, int src_lane)
    {
        return ShuffleIndex<LOGICAL_WARP_THREADS>(input, src_lane, member_mask);
    }


    //---------------------------------------------------------------------
    // Inclusive operations
    //---------------------------------------------------------------------

    /**
     * @brief Inclusive scan
     *
     * @param[in] input
     *   Calling thread's input item
     *
     * @param[out] inclusive_output
     *   Calling thread's output item. May be aliased with @p input
     *
     * @param[in] scan_op
     *   Binary scan operator
     */
    template <typename _T, typename ScanOpT>
    __device__ __forceinline__ void InclusiveScan(_T input, _T &inclusive_output, ScanOpT scan_op)
    {
        inclusive_output = input;

        // Iterate scan steps
        int segment_first_lane = 0;

        // Iterate scan steps
        #pragma unroll
        for (int STEP = 0; STEP < STEPS; STEP++)
        {
            inclusive_output = InclusiveScanStep(
                inclusive_output,
                scan_op,
                segment_first_lane,
                (1 << STEP),
                Int2Type<IntegerTraits<T>::IS_SMALL_UNSIGNED>());
        }

    }

    /**
     * @brief Inclusive scan, specialized for reduce-value-by-key
     *
     * @param[in] input
     *   Calling thread's input item
     *
     * @param[out] inclusive_output
     *   Calling thread's output item. May be aliased with @p input
     *
     * @param[in] scan_op
     *   Binary scan operator
     */
    template <typename KeyT, typename ValueT, typename ReductionOpT>
    __device__ __forceinline__ void InclusiveScan(KeyValuePair<KeyT, ValueT> input,
                                                  KeyValuePair<KeyT, ValueT> &inclusive_output,
                                                  ReduceByKeyOp<ReductionOpT> scan_op)
    {
        inclusive_output = input;

        KeyT pred_key = ShuffleUp<LOGICAL_WARP_THREADS>(inclusive_output.key, 1, 0, member_mask);

        unsigned int ballot = WARP_BALLOT((pred_key != inclusive_output.key), member_mask);

        // Mask away all lanes greater than ours
        ballot = ballot & LaneMaskLe();

        // Find index of first set bit
        int segment_first_lane = CUB_MAX(0, 31 - __clz(ballot));

        // Iterate scan steps
        #pragma unroll
        for (int STEP = 0; STEP < STEPS; STEP++)
        {
            inclusive_output.value = InclusiveScanStep(
                inclusive_output.value,
                scan_op.op,
                segment_first_lane,
                (1 << STEP),
                Int2Type<IntegerTraits<T>::IS_SMALL_UNSIGNED>());
        }
    }

    /**
     * @brief Inclusive scan with aggregate
     *
     * @param[in] input
     *   Calling thread's input item
     *
     * @param[out] inclusive_output
     *   Calling thread's output item. May be aliased with @p input
     *
     * @param[in] scan_op
     *   Binary scan operator
     *
     * @param[out] warp_aggregate
     *   Warp-wide aggregate reduction of input items
     */
    template <typename ScanOpT>
    __device__ __forceinline__ void
    InclusiveScan(T input, T &inclusive_output, ScanOpT scan_op, T &warp_aggregate)
    {
        InclusiveScan(input, inclusive_output, scan_op);

        // Grab aggregate from last warp lane
        warp_aggregate = ShuffleIndex<LOGICAL_WARP_THREADS>(inclusive_output, LOGICAL_WARP_THREADS - 1, member_mask);
    }


    //---------------------------------------------------------------------
    // Get exclusive from inclusive
    //---------------------------------------------------------------------

    /**
     * @brief Update inclusive and exclusive using input and inclusive
     *
     * @param[in] input
     *
     * @param[out] inclusive
     *
     * @param[out] exclusive
     *
     * @param[in] scan_op
     *
     * @param[in] is_integer
     */
    template <typename ScanOpT, typename IsIntegerT>
    __device__ __forceinline__ void
    Update(T /*input*/, T &inclusive, T &exclusive, ScanOpT /*scan_op*/, IsIntegerT /*is_integer*/)
    {
        // initial value unknown
        exclusive = ShuffleUp<LOGICAL_WARP_THREADS>(inclusive, 1, 0, member_mask);
    }

    /**
     * @brief Update inclusive and exclusive using input and inclusive (specialized for summation of
     *        integer types)
     */
    __device__ __forceinline__ void Update(
        T                       input,
        T                       &inclusive,
        T                       &exclusive,
        cub::Sum                /*scan_op*/,
        Int2Type<true>          /*is_integer*/)
    {
        // initial value presumed 0
        exclusive = inclusive - input;
    }

    /**
     * @brief Update inclusive and exclusive using initial value using input, inclusive, and initial
     *        value
     */
    template <typename ScanOpT, typename IsIntegerT>
    __device__ __forceinline__ void Update (
        T                       /*input*/,
        T                       &inclusive,
        T                       &exclusive,
        ScanOpT                 scan_op,
        T                       initial_value,
        IsIntegerT              /*is_integer*/)
    {
        inclusive = scan_op(initial_value, inclusive);
        exclusive = ShuffleUp<LOGICAL_WARP_THREADS>(inclusive, 1, 0, member_mask);

        if (lane_id == 0)
            exclusive = initial_value;
    }

    /**
     * @brief Update inclusive and exclusive using initial value using input and inclusive
     *        (specialized for summation of integer types)
     */
    __device__ __forceinline__ void Update (
        T                       input,
        T                       &inclusive,
        T                       &exclusive,
        cub::Sum                scan_op,
        T                       initial_value,
        Int2Type<true>          /*is_integer*/)
    {
        inclusive = scan_op(initial_value, inclusive);
        exclusive = inclusive - input;
    }

    /**
     * @brief Update inclusive, exclusive, and warp aggregate using input and inclusive
     */
    template <typename ScanOpT, typename IsIntegerT>
    __device__ __forceinline__ void Update (
        T                       input,
        T                       &inclusive,
        T                       &exclusive,
        T                       &warp_aggregate,
        ScanOpT                 scan_op,
        IsIntegerT              is_integer)
    {
        warp_aggregate = ShuffleIndex<LOGICAL_WARP_THREADS>(inclusive, LOGICAL_WARP_THREADS - 1, member_mask);
        Update(input, inclusive, exclusive, scan_op, is_integer);
    }

    /**
     * @brief Update inclusive, exclusive, and warp aggregate using input, inclusive, and initial
     *        value
     */
    template <typename ScanOpT, typename IsIntegerT>
    __device__ __forceinline__ void Update (
        T                       input,
        T                       &inclusive,
        T                       &exclusive,
        T                       &warp_aggregate,
        ScanOpT                 scan_op,
        T                       initial_value,
        IsIntegerT              is_integer)
    {
        warp_aggregate = ShuffleIndex<LOGICAL_WARP_THREADS>(inclusive, LOGICAL_WARP_THREADS - 1, member_mask);
        Update(input, inclusive, exclusive, scan_op, initial_value, is_integer);
    }



};


CUB_NAMESPACE_END
