naive_attention.hpp Source File

naive_attention.hpp Source File#

Composable Kernel: naive_attention.hpp Source File
// SPDX-License-Identifier: MIT
// Copyright (c) 2018-2025, Advanced Micro Devices, Inc. All rights reserved.
 
#pragma once
 
#include "ck_tile/core.hpp"
#include "ck_tile/host/host_tensor.hpp"
#include "ck_tile/host/kernel_launch.hpp"
#include <thread>
#include <string>
 
namespace ck_tile {
 
enum class naive_attention_layout_enum
{
    DEFAULT, // maybe this tensor is not used, set some irrelevant value
    BSHD,    // [batch, seqlen, nhead, hdim]
    BHSD,    // [batch, nhead, seqlen, hdim]
    BS3HD,   // [batch, nhead, 3, seqlen, hdim], used when qkv are packed
    PHSD,    // [pages, nhead, page_size, hdim]
    // PHSDX, // [pages, nhead, page_size/x, hdim, x], where <# used pages>*page_size = seqlen
    PHDSX, // [pages, nhead, hdim/x, page_size, x], where <# used pages>*page_size = seqlen
    PHDS,  // [pages, nhead, hdim, page_size], where <# used pages>*page_size = seqlen
 
    // scale layout used for dynamic dequant
    SCALE_HS, // [nhead, tokens] or [nhead, tokens-per-group], nhe KVCache quant
    SCALE_SH, // [tokens, nhead]
};
 
// will used to specialize kernel variation
enum class naive_attention_variation_enum
{
    FLASH_BATCHED = 0, // standard flash attention, or xformer/sdpa, used for training
    FLASH_GROUPED,
    DECODE_PAGED, // decode attn, where kv token from another buffer called kvcache
};
 
enum class naive_attention_quant_algo
{
    NO              = 0,
    KV_8BIT_PERHEAD = 1,
    // FP8/INT8 quant for KVCache, per-token quant
    // [num_tokens, nhead, hdim] -> [nhead, num_tokens]
    KV_8BIT_PERTOKEN = 2,
};
 
// TODO: for simplicity, this will be used as host/device arg
struct naive_attention_fwd_args
{
    void* q_ptr;
    void* k_ptr;
    void* v_ptr;
    void* o_ptr;
    void* context_len_ptr; // [batch] used when seqlen kv come from a pointer(each element is a
                           // number, not cumsum)
    void* page_table_ptr;  // [batch, max_pages_per_seq] seqlen_kv is in different block(paged attn)
    void* kscale_ptr;      // [nhead, max_kv_tokens] used for kvcache dequant
    void* vscale_ptr;      // [nhead, max_kv_tokens] used for kvcache dequant
    float scale_s;
    int hdim;
    int hdim_v; // could be cross-attn, where V and Q/K hdim are different
    int batch_q;
    int batch_kv;
    int batch_ratio_kv; // batch_q / batch_kv
    int seqlen_q;       // in decode case, this should be 1
    int seqlen_kv;      // if context_len_ptr is not nullptr, ignore this field
    int nhead_q;
    int nhead_kv;
    int nhead_ratio_kv; // nhead_q / nhead_kv
    int page_size;      // if paged, the seqlen-kv per each block
    int max_pages_per_seq;
    int max_kv_tokens; // used as stride to access kv scale ptr
};
 
// this is trait for host API
struct naive_attention_fwd_traits
{
    std::string q_type;
    std::string k_type;
    std::string v_type;
    std::string o_type;
    std::string q_layout;
    std::string k_layout;
    std::string v_layout;
    std::string o_layout;
    int variation;  // sync with naive_attention_variation_enum
    int quant_algo; // sync with naive_attention_quant_algo
};
 
// this is trait for kernel template
template <naive_attention_variation_enum variation_, naive_attention_quant_algo quant_algo_>
struct naive_attention_fwd_kernel_traits
{
    static constexpr naive_attention_variation_enum variation = variation_;
    static constexpr naive_attention_quant_algo quant_algo    = quant_algo_;
};
 
// for simplicity, please do not use const-reference type for the template type
template <typename QType,
          typename KType,
          typename VType,
          typename OType,
          typename AccType,
          typename KVScaleType,
          naive_attention_layout_enum QLayout,
          naive_attention_layout_enum KLayout,
          naive_attention_layout_enum VLayout,
          naive_attention_layout_enum OLayout,
          naive_attention_layout_enum KScaleLayout,
          naive_attention_layout_enum VScaleLayout,
          typename Traits>
struct naive_attention_fwd_kernel
{
    static constexpr bool is_kvcache_i8 =
        std::is_same_v<KType, int8_t> && std::is_same_v<VType, int8_t>;
    static constexpr bool is_kvcache_fp8 =
        std::is_same_v<KType, fp8_t> && std::is_same_v<VType, fp8_t>;
 
    static constexpr int v_per_token_quant_group_size = 64;
    static constexpr int kBlockSize                   = 256;
    // TODO: hardcode
    using SoftmaxType      = float; // always using float to do softmax compute
    using QuantComputeType = float; // used for quant/dequant scale compute
    using QCompute         = KType; // src A of gemm1, same type as K
    using PType            = VType; // src A of gemm2, same type as V
    using OAccType         = float; // always float, in case int8 FA
 
    using p_vec_type                = ext_vector_t<PType, 16 / sizeof(PType)>;
    static constexpr int p_vec_elem = vector_traits<p_vec_type>::vector_size;
 
    // clang-format off
    template <typename T_> struct scale_max { static constexpr float value = 1; /* dummy code */ };
    template <> struct scale_max<int8_t> { static constexpr float value = 127.0; };
    template <> struct scale_max<fp8_t> { static constexpr float value = 240.0; };
    // clang-format on
 
    __host__ __device__ naive_attention_fwd_kernel() {}
 
    template <typename T, naive_attention_layout_enum Layout>
    struct addresser
    {
        int b, s, h, d; // batch, seqlen, nhead, hdim
        T* base_ptr;
        __device__ addresser(int b_, int s_, int h_, int d_, void* base_ptr_)
            : b(b_), s(s_), h(h_), d(d_), base_ptr(reinterpret_cast<T*>(base_ptr_))
        {
        }
 
        // TODO: all the batch/nhead offset will accumulate to the base pointer
        __device__ T* get_base(int i_b, int i_h)
        {
            if constexpr(Layout == naive_attention_layout_enum::BSHD)
                return base_ptr + i_b * s * h * d + i_h * d;
            else if constexpr(Layout == naive_attention_layout_enum::BHSD)
                return base_ptr + i_b * s * h * d + i_h * s * d;
        }
 
        __device__ int get_offset(int i_s, int i_d)
        {
            if constexpr(Layout == naive_attention_layout_enum::BSHD)
                return i_s * h * d + i_d;
            else if constexpr(Layout == naive_attention_layout_enum::BHSD)
                return i_s * d + i_d;
        }
 
        // below set of API will directly use pointer inside this struct
        __device__ void init(int i_b, int i_h) { base_ptr = get_base(i_b, i_h); }
        __device__ T load(int i_s, int i_d) { return base_ptr[get_offset(i_s, i_d)]; }
        __device__ void store(T value, int i_s, int i_d) { base_ptr[get_offset(i_s, i_d)] = value; }
    };
 
    template <typename T, naive_attention_layout_enum Layout>
    struct page_addresser
    {
        int s, h, d;                             // page_size, nhead, hdim
        static constexpr int x = 16 / sizeof(T); // pack 4 dword
        T* base_ptr;
        int* page_table_ptr; // TODO: page table always int
        int i_h;             // store current head
 
        __device__ page_addresser(int s_, int h_, int d_, void* base_ptr_, void* pptr_)
            : s(s_),
              h(h_),
              d(d_),
              base_ptr(reinterpret_cast<T*>(base_ptr_)),
              page_table_ptr(reinterpret_cast<int*>(pptr_))
        {
        }
 
        __device__ int64_t get_phy_page_idx(int i_s)
        {
            // dynamic compute page idx is simple but slow
            int page_idx = i_s / s;
            int phy      = page_table_ptr[page_idx];
            return static_cast<int64_t>(phy);
        }
 
        __device__ int get_phy_page_offset(int i_s)
        {
            // dynamic compute page idx is simple but slow
            return i_s % s;
        }
 
        __device__ int64_t get_offset(int i_s, int i_d)
        {
            int page_offset  = get_phy_page_offset(i_s);
            int64_t page_idx = get_phy_page_idx(i_s);
            int64_t base_    = page_idx * h * s * d;
            if constexpr(Layout == naive_attention_layout_enum::PHSD)
                return static_cast<int64_t>(i_h * s * d + page_offset * d + i_d) + base_;
            else if constexpr(Layout == naive_attention_layout_enum::PHDSX)
            {
                int d_r = i_d / x;
                int d_x = i_d % x;
                return static_cast<int64_t>(i_h * d * s + d_r * s * x + page_offset * x + d_x) +
                       base_;
            }
            else if constexpr(Layout == naive_attention_layout_enum::PHDS)
            {
                return static_cast<int64_t>(i_h * d * s + i_d * s + page_offset) + base_;
            }
        }
 
        // below set of API will directly use pointer inside this struct
        __device__ void init(int /*i_b*/, int i_h_) { i_h = i_h_; }
        __device__ T load(int i_s, int i_d) { return base_ptr[get_offset(i_s, i_d)]; }
        __device__ void store(T /*value*/, int /*i_s*/, int /*i_d*/) {}
    };
 
    template <typename T, naive_attention_layout_enum Layout>
    struct kvscale_addresser
    {
        int s, h, d; // seqlen(tokens), nhead, hdim
        T* base_ptr;
        __device__ kvscale_addresser(int s_, int h_, int d_, void* p_)
            : s(s_), h(h_), d(d_), base_ptr(reinterpret_cast<T*>(p_))
        {
        }
        __device__ int get_offset(int i_s, int i_h, int i_d)
        {
            if constexpr(Layout == naive_attention_layout_enum::SCALE_HS)
            {
                // [nhead, tokens]
                (void)i_d;
                return i_h * s + i_s;
            }
            else if constexpr(Layout == naive_attention_layout_enum::DEFAULT)
            {
                return 0;
            }
            // [h, 2, d]
            // return i_h * 2 * d + i_kv * d + i_d;
        }
        __device__ T load(int i_s, int i_h, int i_d) { return base_ptr[get_offset(i_s, i_h, i_d)]; }
    };
 
    __device__ __host__ static constexpr int get_block_size() { return kBlockSize; }
 
    // for simpliciy, 1 WG always compute 1 token along q, compute all token along kv
    // compute all hdim from q, compute WG_SIZE hdim from v
    // 1) in prefill case, seqlen_q >= 1, seqlen_kv >= 1, batch_q=batch_kv
    // 2) in decode case, seqlen_q = 1, batch_q is input num-tokens, batch_kv is 1
    // 3) in paged-attn case, we still use 1 WG compute all the seqlen-kv for simplicity
    // TODO: could support split-kv to validate intermediate logsum
    __host__ static dim3 get_grid_size(naive_attention_fwd_args args)
    {
        constexpr int wg_size = get_block_size();
        auto g =
            dim3((args.hdim_v + wg_size - 1) / wg_size, args.seqlen_q, args.batch_q * args.nhead_q);
        return g;
    }
 
    // reduce single pixel within a wave
    template <typename T, typename F>
    __device__ constexpr T wave_reduce(T local, F reduce_f)
    {
        // constexpr int wave_size = 64;
        constexpr int reduce_stage = 6; // 1<<6=64
        T v_local                  = local;
#pragma unroll
        for(int i_stage = 0; i_stage < reduce_stage; i_stage++)
        {
            int src_lane = __lane_id() ^ (1 << i_stage);
            int32_t v_remote_tmp =
                __builtin_amdgcn_ds_bpermute(src_lane << 2, bit_cast<int32_t>(v_local));
            T v_remote = bit_cast<T>(v_remote_tmp);
            v_local    = reduce_f(v_local, v_remote);
        }
        return v_local;
    }
 
    // Note: this function must be called after wave_reduce
    // Note: better not use this under if...else... with thread divergence (syncthreads)
    template <typename T, typename F>
    __device__ constexpr T cross_wave_reduce(T local, F reduce_f, T* smem)
    {
        constexpr int waves     = 4;
        constexpr int wave_size = 64;
        int lane_id             = threadIdx.x % wave_size;
 
        __syncthreads();
        smem[threadIdx.x] = local;
        __syncthreads();
 
        // the data within single wave is the same
        // but for simplicity, we still use data from each lane.
        T v_local = smem[lane_id];
#pragma unroll
        for(int i_stage = 1; i_stage < waves; i_stage++)
        {
            T v_remote = smem[i_stage * wave_size + lane_id];
            v_local    = reduce_f(v_local, v_remote);
        }
        return v_local;
    }
 
    // kernel entry point
    __device__ void operator()(naive_attention_fwd_args args)
    {
        constexpr int wg_size = get_block_size();
        __shared__ char smem[wg_size * 4 * sizeof(float)];       //  should enough
        char* smem_quant_q = smem + wg_size * 2 * sizeof(float); // second half, should enough
        int i_dv           = blockIdx.x * wg_size + threadIdx.x; // index of hdim_v
        int i_sq           = blockIdx.y;                         // index of seqlen_q
        int i_batch        = blockIdx.z;                         // index of batch_q * nhead_q
        int i_bq           = i_batch / args.nhead_q;             // index of batch_q
        int i_hq           = i_batch % args.nhead_q;             // index of nhead_q
 
        int i_bk = i_bq / args.batch_ratio_kv;
        int i_hk = i_hq / args.nhead_ratio_kv;
 
        void* page_table_ptr = [&]() {
            if constexpr(Traits::variation == naive_attention_variation_enum::DECODE_PAGED)
            {
                return reinterpret_cast<int*>(args.page_table_ptr) + i_bq * args.max_pages_per_seq;
            }
            else
            {
                return nullptr;
            }
        }();
 
        auto q_addr = [&]() {
            if constexpr(Traits::variation == naive_attention_variation_enum::FLASH_BATCHED)
            {
                return addresser<QType, QLayout>{
                    args.batch_q, args.seqlen_q, args.nhead_q, args.hdim, args.q_ptr};
            }
            else if constexpr(Traits::variation == naive_attention_variation_enum::DECODE_PAGED)
            {
                return addresser<QType, QLayout>{
                    args.batch_q, args.seqlen_q, args.nhead_q, args.hdim, args.q_ptr};
            }
        }();
        auto k_addr = [&]() {
            if constexpr(Traits::variation == naive_attention_variation_enum::FLASH_BATCHED)
            {
                return addresser<KType, KLayout>{
                    args.batch_kv, args.seqlen_kv, args.nhead_kv, args.hdim, args.k_ptr};
            }
            else if constexpr(Traits::variation == naive_attention_variation_enum::DECODE_PAGED)
            {
                return page_addresser<KType, KLayout>{
                    args.page_size, args.nhead_kv, args.hdim, args.k_ptr, page_table_ptr};
            }
        }();
        auto v_addr = [&]() {
            if constexpr(Traits::variation == naive_attention_variation_enum::FLASH_BATCHED)
            {
                return addresser<VType, VLayout>{
                    args.batch_kv, args.seqlen_kv, args.nhead_kv, args.hdim_v, args.v_ptr};
            }
            else if constexpr(Traits::variation == naive_attention_variation_enum::DECODE_PAGED)
            {
                return page_addresser<VType, VLayout>{
                    args.page_size, args.nhead_kv, args.hdim_v, args.v_ptr, page_table_ptr};
            }
        }();
        auto o_addr = [&]() {
            if constexpr(Traits::variation == naive_attention_variation_enum::FLASH_BATCHED)
            {
                return addresser<OType, OLayout>{
                    args.batch_q, args.seqlen_q, args.nhead_q, args.hdim_v, args.o_ptr};
            }
            else if constexpr(Traits::variation == naive_attention_variation_enum::DECODE_PAGED)
            {
                return addresser<OType, OLayout>{
                    args.batch_q, args.seqlen_q, args.nhead_q, args.hdim_v, args.o_ptr};
            }
        }();
 
        q_addr.init(i_bq, i_hq);
        k_addr.init(i_bk, i_hk);
        v_addr.init(i_bk, i_hk);
        o_addr.init(i_bq, i_hq);
 
        auto f_max        = [](auto x_, auto y_) { return max(x_, y_); };
        auto f_sum        = [](auto x_, auto y_) { return x_ + y_; };
        auto f_absmax_f32 = [](float v_0_, float v_1_) {
            // float rtn;
            // asm volatile("v_max_f32 %0, abs(%1), abs(%2)" : "=v"(rtn) : "v"(v_0_), "v"(v_1_));
            // return rtn;
            return max(abs(v_0_), abs(v_1_));
        };
 
        int seqlen_kv = [&]() {
            if constexpr(Traits::variation == naive_attention_variation_enum::FLASH_BATCHED)
            {
                return args.seqlen_kv;
            }
            else if constexpr(Traits::variation == naive_attention_variation_enum::DECODE_PAGED)
            {
                return reinterpret_cast<int*>(args.context_len_ptr)[i_bq];
            }
        }();
 
        SoftmaxType row_max = -numeric<SoftmaxType>::infinity();
        SoftmaxType l{0};
        // AccType o_acc = {0};
        OAccType o_acc = {0};
 
        int sk_loops                     = (seqlen_kv + wg_size - 1) / wg_size;
        QuantComputeType q_dequant_scale = .0f;
        kvscale_addresser<KVScaleType, KScaleLayout> kscale_addr{
            args.max_kv_tokens, args.nhead_kv, args.hdim, args.kscale_ptr};
        kvscale_addresser<KVScaleType, VScaleLayout> vscale_addr{
            args.max_kv_tokens, args.nhead_kv, args.hdim_v, args.vscale_ptr};
 
        if constexpr(Traits::quant_algo == naive_attention_quant_algo::KV_8BIT_PERHEAD)
        {
            // AccType is i32 now, seqlen_q = 1, hdim up to 256
            AccType q   = 0;
            AccType k_s = 0;
            if(static_cast<int>(threadIdx.x) < args.hdim)
            {
                q   = type_convert<AccType>(q_addr.load(0, threadIdx.x));
                k_s = type_convert<AccType>(kscale_addr.load(i_hk, threadIdx.x, 0));
            }
            // 1) we apply the k scale to q
            AccType q_forwarded = q * k_s;
 
            // 2) apply smooth-quant
            // find absmax
            AccType qf_max = wave_reduce(q_forwarded, f_absmax_f32);
            qf_max = cross_wave_reduce(qf_max, f_absmax_f32, reinterpret_cast<AccType*>(smem));
 
            // per-token scale
            q_dequant_scale = type_convert<QuantComputeType>(qf_max) / scale_max<QCompute>::value;
 
            // devide by scale
            q = q / q_dequant_scale;
 
            // fp32->i8
            QCompute quantized_q = static_cast<QCompute>(q);
            __syncthreads();
            reinterpret_cast<QCompute*>(smem)[threadIdx.x] = quantized_q;
            __syncthreads();
 
            // after above process, we have 2 data
            // 1) int8 q data stored in smem(no need to reload)
            // 2) per-token scale q_dequant_scale, to be mul after 1st gemm
        }
        else if constexpr(Traits::quant_algo == naive_attention_quant_algo::KV_8BIT_PERTOKEN)
        {
            if(std::is_same_v<QType, fp16_t> || std::is_same_v<QType, bf16_t>)
            {
                // dyanmic quant q here
                float q = 0;
                if(static_cast<int>(threadIdx.x) < args.hdim)
                {
                    q = type_convert<float>(q_addr.load(i_sq, threadIdx.x));
                }
 
                // apply smooth-quant
                // find absmax
                float q_max = wave_reduce(q, f_absmax_f32);
                q_max = cross_wave_reduce(q_max, f_absmax_f32, reinterpret_cast<float*>(smem));
 
                // per-token scale
                q_dequant_scale =
                    type_convert<QuantComputeType>(q_max) / scale_max<QCompute>::value;
 
                // devide by scale
                q = q / q_dequant_scale;
 
                QCompute quantized_q = type_convert<QCompute>(q);
                __syncthreads();
                reinterpret_cast<QCompute*>(smem_quant_q)[threadIdx.x] = quantized_q;
                __syncthreads();
 
                // after above process, we have 2 data
                // 1) fp8 q data stored in smem(no need to reload from global)
                // 2) per-token scale q_dequant_scale, to be mul after 1st gemm
            }
        }
 
        for(int i_loop1 = 0; i_loop1 < sk_loops; i_loop1++)
        {
            int i_sk = i_loop1 * wg_size + threadIdx.x;
            // gemm-1
            SoftmaxType s_softmax = -numeric<SoftmaxType>::infinity();
            if(i_sk < seqlen_kv)
            {
                AccType s_acc{0}; // clear for every loop
                for(auto i_dq = 0; i_dq < args.hdim; i_dq++)
                {
                    auto q = [&]() {
                        if constexpr(Traits::quant_algo ==
                                         naive_attention_quant_algo::KV_8BIT_PERHEAD ||
                                     Traits::quant_algo ==
                                         naive_attention_quant_algo::KV_8BIT_PERTOKEN)
                        {
                            return reinterpret_cast<QCompute*>(smem_quant_q)[i_dq];
                        }
                        else
                            return q_addr.load(i_sq, i_dq); // q will have duplicate load
                    }();
                    auto k = [&]() { return k_addr.load(i_sk, i_dq); }();
 
                    s_acc += type_convert<AccType>(q) * type_convert<AccType>(k);
                }
                // scale
                s_softmax = type_convert<SoftmaxType>(s_acc);
                s_softmax *=
                    type_convert<SoftmaxType>(args.scale_s * ck_tile::log2e_v<SoftmaxType>);
                if constexpr(Traits::quant_algo == naive_attention_quant_algo::KV_8BIT_PERHEAD)
                {
                    s_softmax *= q_dequant_scale; // post scale the per-token factor
                }
                else if constexpr(Traits::quant_algo ==
                                  naive_attention_quant_algo::KV_8BIT_PERTOKEN)
                {
                    SoftmaxType k_per_token_scale =
                        type_convert<SoftmaxType>(kscale_addr.load(i_sk, i_hk, 0));
                    s_softmax *= q_dequant_scale;
                    s_softmax *= k_per_token_scale;
                }
            }
 
            // s->p
            QuantComputeType p_dequant_scale = 1.;
            {
                // softmax, find max
                SoftmaxType old_max = row_max;
                SoftmaxType cur_max = wave_reduce(s_softmax, f_max);
 
                cur_max = cross_wave_reduce(cur_max, f_max, reinterpret_cast<SoftmaxType*>(smem));
                row_max = max(old_max, cur_max); // update row_max
                // softmax, exp(i_elem - max)
                SoftmaxType p_compute = __builtin_amdgcn_exp2f(s_softmax - row_max);
 
                // compute exp_sum
                SoftmaxType row_sum = wave_reduce(p_compute, f_sum);
                row_sum = cross_wave_reduce(row_sum, f_sum, reinterpret_cast<SoftmaxType*>(smem));
 
                // l, pre-scall o_acc
                SoftmaxType tmp = __builtin_amdgcn_exp2f(old_max - row_max);
                l               = tmp * l + row_sum;
                o_acc           = type_convert<OAccType>(type_convert<SoftmaxType>(o_acc) * tmp);
 
                // prepare the p_compute into smem, to let every thread read same p_compute and do
                // 2nd gemm
                if constexpr(Traits::quant_algo == naive_attention_quant_algo::KV_8BIT_PERHEAD)
                {
                    QuantComputeType v_s = 0;
                    if(static_cast<int>(threadIdx.x) < args.hdim_v)
                    {
                        v_s =
                            type_convert<QuantComputeType>(vscale_addr.load(i_hk, threadIdx.x, 1));
                    }
 
                    // 1) we apply the v scale to p
                    QuantComputeType p_forwarded = p_compute * v_s;
 
                    // 2) apply smooth-quant
                    // find absmax
                    QuantComputeType pf_max = wave_reduce(p_forwarded, f_absmax_f32);
                    pf_max                  = cross_wave_reduce(
                        pf_max, f_absmax_f32, reinterpret_cast<QuantComputeType*>(smem));
 
                    // per-token scale
                    p_dequant_scale = pf_max / scale_max<PType>::value; // 127.0;
 
                    // devide by scale
                    p_compute = p_compute / p_dequant_scale;
 
                    // fp32->i8
                    PType quantized_p = static_cast<PType>(p_compute);
                    __syncthreads();
                    reinterpret_cast<PType*>(smem)[threadIdx.x] = quantized_p;
                    __syncthreads();
                    // after above process, we have 2 data
                    // 1) int8 p data stored in smem(no need to reload)
                    // 2) per-token scale p_dequant_scale, to be mul after 2nd gemm
                }
                else if constexpr(Traits::quant_algo ==
                                  naive_attention_quant_algo::KV_8BIT_PERTOKEN)
                {
                    // forward apply the v scale to p_compute, this is compute friendly
                    auto v_scale = type_convert<QuantComputeType>(vscale_addr.load(i_sk, i_hk, 0));
                    p_compute *= v_scale;
                    // smooth-quant
                    // find absmax
                    QuantComputeType p_max = wave_reduce(p_compute, f_absmax_f32);
                    p_max                  = cross_wave_reduce(
                        p_max, f_absmax_f32, reinterpret_cast<QuantComputeType*>(smem));
 
                    // per-token scale
                    p_dequant_scale = p_max / scale_max<PType>::value; // 240.0;
 
                    // devide by scale
                    p_compute = p_compute / p_dequant_scale;
 
                    // fp32->i8
                    PType quantized_p = type_convert<PType>(p_compute);
                    __syncthreads();
                    reinterpret_cast<PType*>(smem)[threadIdx.x] = quantized_p;
                    __syncthreads();
                    // after above process, we have 2 data
                    // 1) fp8_t p data stored in smem(no need to reload)
                    // 2) per-token scale p_dequant_scale, to be mul after 2nd gemm
                }
                else
                {
                    __syncthreads();
                    reinterpret_cast<PType*>(smem)[threadIdx.x] = type_convert<PType>(p_compute);
                    __syncthreads();
                }
            }
 
            // gemm-2, simple loop over vector by vector
            constexpr int gemm_2_loop = wg_size / p_vec_elem;
            {
                AccType o_acc_local = {0};
                int sk_start = i_loop1 * wg_size; // we start from the first seqlen_kv element
                for(int i_loop2 = 0; i_loop2 < gemm_2_loop; i_loop2++)
                {
                    p_vec_type p_vec = reinterpret_cast<p_vec_type*>(smem)[i_loop2];
#pragma unroll
                    for(int i_j = 0; i_j < p_vec_elem; i_j++)
                    {
                        int sv_offset = i_loop2 * p_vec_elem + i_j;
                        int i_sv      = sk_start + sv_offset;
 
                        VType v = 0;
                        if(i_dv < args.hdim_v && i_sv < seqlen_kv)
                        {
                            v = v_addr.load(i_sv, i_dv);
                        }
 
                        AccType v_compute = [&]() { return type_convert<AccType>(v); }();
 
                        o_acc_local += type_convert<AccType>(p_vec[i_j]) * v_compute;
                    }
                }
 
                OAccType post_scale_o_acc_local = [&]() {
                    if constexpr(Traits::quant_algo == naive_attention_quant_algo::KV_8BIT_PERHEAD)
                    {
                        // apply pr scale to local acc
                        return type_convert<OAccType>(type_convert<QuantComputeType>(o_acc_local) *
                                                      p_dequant_scale);
                    }
                    else if constexpr(Traits::quant_algo ==
                                      naive_attention_quant_algo::KV_8BIT_PERTOKEN)
                    {
                        // apply pr scale to local acc
                        return type_convert<OAccType>(type_convert<QuantComputeType>(o_acc_local) *
                                                      p_dequant_scale);
                    }
                    else
                    {
                        return type_convert<OAccType>(o_acc_local);
                    }
                }();
                o_acc += post_scale_o_acc_local;
            }
        }
 
        // post scale o_acc
        {
            SoftmaxType tmp = l == 0.f ? 0.f : 1.f / l; // in case masking
            o_acc           = type_convert<OAccType>(type_convert<SoftmaxType>(o_acc) * tmp);
        }
 
        // store O
        if(i_dv < args.hdim_v)
            o_addr.store(type_convert<OType>(o_acc), i_sq, i_dv);
    }
};
 
#define CK_TILE_DISPATCH_NAIVE_ATTEN_FWD_INTERNAL_()                                                        \
    {                                                                                                       \
        using ktraits_ = naive_attention_fwd_kernel_traits<                                                 \
            static_cast<naive_attention_variation_enum>(variation_),                                        \
            static_cast<naive_attention_quant_algo>(quant_algo_)>;                                          \
        using k_   = naive_attention_fwd_kernel<q_type_,                                                    \
                                                k_type_,                                                    \
                                                v_type_,                                                    \
                                                o_type_,                                                    \
                                                acc_type_,                                                  \
                                                kvscale_type_,                                              \
                                                q_layout_,                                                  \
                                                k_layout_,                                                  \
                                                v_layout_,                                                  \
                                                o_layout_,                                                  \
                                                k_scale_layout_,                                            \
                                                v_scale_layout_,                                            \
                                                ktraits_>;                                                  \
        dim3 grids = k_::get_grid_size(a);                                                                  \
        r          = ck_tile::launch_kernel(s,                                                              \
                                   ck_tile::make_kernel(k_{}, grids, k_::get_block_size(), 0, a)); \
    }
 
#define CK_TILE_DISPATCH_NAIVE_ATTEN_FWD_LAOYUT_()                                                 \
    if(t.variation == 0 && t.q_layout == "bshd" && t.k_layout == "bshd" && t.v_layout == "bshd" && \
       t.o_layout == "bshd")                                                                       \
    {                                                                                              \
        constexpr auto q_layout_       = naive_attention_layout_enum::BSHD;                        \
        constexpr auto k_layout_       = naive_attention_layout_enum::BSHD;                        \
        constexpr auto v_layout_       = naive_attention_layout_enum::BSHD;                        \
        constexpr auto o_layout_       = naive_attention_layout_enum::BSHD;                        \
        constexpr auto k_scale_layout_ = naive_attention_layout_enum::DEFAULT;                     \
        constexpr auto v_scale_layout_ = naive_attention_layout_enum::DEFAULT;                     \
        constexpr int variation_       = 0;                                                        \
        CK_TILE_DISPATCH_NAIVE_ATTEN_FWD_INTERNAL_();                                              \
    }                                                                                              \
    else if(t.variation == 0 && t.q_layout == "bhsd" && t.k_layout == "bhsd" &&                    \
            t.v_layout == "bhsd" && t.o_layout == "bhsd")                                          \
    {                                                                                              \
        constexpr auto q_layout_       = naive_attention_layout_enum::BHSD;                        \
        constexpr auto k_layout_       = naive_attention_layout_enum::BHSD;                        \
        constexpr auto v_layout_       = naive_attention_layout_enum::BHSD;                        \
        constexpr auto o_layout_       = naive_attention_layout_enum::BHSD;                        \
        constexpr auto k_scale_layout_ = naive_attention_layout_enum::DEFAULT;                     \
        constexpr auto v_scale_layout_ = naive_attention_layout_enum::DEFAULT;                     \
        constexpr int variation_       = 0;                                                        \
        CK_TILE_DISPATCH_NAIVE_ATTEN_FWD_INTERNAL_();                                              \
    }                                                                                              \
    else if(t.variation == 2 && t.q_layout == "bhsd" && t.k_layout == "phdsx" &&                   \
            t.v_layout == "phds" && t.o_layout == "bhsd")                                          \
    {                                                                                              \
        constexpr auto q_layout_       = naive_attention_layout_enum::BHSD;                        \
        constexpr auto k_layout_       = naive_attention_layout_enum::PHDSX;                       \
        constexpr auto v_layout_       = naive_attention_layout_enum::PHDS;                        \
        constexpr auto o_layout_       = naive_attention_layout_enum::BHSD;                        \
        constexpr auto k_scale_layout_ = naive_attention_layout_enum::SCALE_HS;                    \
        constexpr auto v_scale_layout_ = naive_attention_layout_enum::SCALE_HS;                    \
        constexpr int variation_       = 2;                                                        \
        CK_TILE_DISPATCH_NAIVE_ATTEN_FWD_INTERNAL_();                                              \
    }
 
//
CK_TILE_HOST float naive_attention_fwd(naive_attention_fwd_traits t,
                                       naive_attention_fwd_args a,
                                       ck_tile::stream_config s)
{
    float r = -1;
    // TODO: do not explicitly create too much instance!
    if(t.q_type == "fp16" && t.k_type == "fp16" && t.v_type == "fp16" && t.o_type == "fp16" &&
       t.quant_algo == 0)
    {
        using q_type_             = fp16_t;
        using k_type_             = fp16_t;
        using v_type_             = fp16_t;
        using o_type_             = fp16_t;
        using acc_type_           = float;
        using kvscale_type_       = float;
        constexpr int quant_algo_ = 0;
        CK_TILE_DISPATCH_NAIVE_ATTEN_FWD_LAOYUT_();
    }
    else if(t.q_type == "bf16" && t.k_type == "bf16" && t.v_type == "bf16" && t.o_type == "bf16" &&
            t.quant_algo == 0)
    {
        using q_type_             = bf16_t;
        using k_type_             = bf16_t;
        using v_type_             = bf16_t;
        using o_type_             = bf16_t;
        using acc_type_           = float;
        using kvscale_type_       = float;
        constexpr int quant_algo_ = 0;
        CK_TILE_DISPATCH_NAIVE_ATTEN_FWD_LAOYUT_();
    }
    else if(t.q_type == "bf16" && t.k_type == "fp8" && t.v_type == "fp8" && t.o_type == "bf16" &&
            t.quant_algo == 2)
    {
        using q_type_             = bf16_t;
        using k_type_             = fp8_t;
        using v_type_             = fp8_t;
        using o_type_             = bf16_t;
        using acc_type_           = float; // NOTE!
        using kvscale_type_       = float;
        constexpr int quant_algo_ = 2;
        CK_TILE_DISPATCH_NAIVE_ATTEN_FWD_LAOYUT_();
    }
    else if(t.q_type == "fp16" && t.k_type == "fp8" && t.v_type == "fp8" && t.o_type == "fp16" &&
            t.quant_algo == 2)
    {
        using q_type_             = fp16_t;
        using k_type_             = fp8_t;
        using v_type_             = fp8_t;
        using o_type_             = fp16_t;
        using acc_type_           = float; // NOTE!
        using kvscale_type_       = float;
        constexpr int quant_algo_ = 2;
        CK_TILE_DISPATCH_NAIVE_ATTEN_FWD_LAOYUT_();
    }
    else if(t.q_type == "bf16" && t.k_type == "int8" && t.v_type == "int8" && t.o_type == "bf16" &&
            t.quant_algo == 2)
    {
        using q_type_             = bf16_t;
        using k_type_             = int8_t;
        using v_type_             = int8_t;
        using o_type_             = bf16_t;
        using acc_type_           = int32_t; // NOTE!
        using kvscale_type_       = float;
        constexpr int quant_algo_ = 2;
        CK_TILE_DISPATCH_NAIVE_ATTEN_FWD_LAOYUT_();
    }
    return r;
}
 
#undef CK_TILE_DISPATCH_NAIVE_ATTEN_FWD_LAOYUT_
#undef CK_TILE_DISPATCH_NAIVE_ATTEN_FWD_INTERNAL_
 
} // namespace ck_tile