fmha_batch_prefill_kernel.hpp Source File

fmha_batch_prefill_kernel.hpp Source File#

Composable Kernel: fmha_batch_prefill_kernel.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/ops/common.hpp"
#include "ck_tile/ops/fmha/block/block_attention_bias_enum.hpp"
#include "ck_tile/ops/fmha/block/variants.hpp"
 
#include <string>
#include <type_traits>
#include <utility>
#include <variant>
 
// S[seqlen_q, seqlen_k] = Q[seqlen_q, hdim_q] @ K[seqlen_k, hdim_q]
// S'[seqlen_q, seqlen_k] = S[seqlen_q, seqlen_k] * Scale[1]
// S''[seqlen_q, seqlen_k] = S'[seqlen_q, seqlen_k] + Bias[seqlen_q, seqlen_k]
// P[seqlen_q, seqlen_k] = Softmax(S''[seqlen_q, seqlen_k])
// O[seqlen_q, hdim_v] = P[seqlen_q, seqlen_k] @ V^T[hdim_v, seqlen_k]
 
namespace ck_tile {
 
template <typename FmhaPipeline_, typename EpiloguePipeline_>
struct FmhaBatchPrefillWithPagedKVCacheKernel
{
    using FmhaPipeline                           = ck_tile::remove_cvref_t<FmhaPipeline_>;
    using EpiloguePipeline                       = ck_tile::remove_cvref_t<EpiloguePipeline_>;
    static constexpr ck_tile::index_t kBlockSize = FmhaPipeline::kBlockSize;
 
    static constexpr ck_tile::index_t kBlockPerCu = FmhaPipeline::kBlockPerCu;
    static_assert(kBlockPerCu > 0);
    static constexpr ck_tile::index_t kBlockPerCuInput = FmhaPipeline::Problem::kBlockPerCu;
 
    using QDataType    = ck_tile::remove_cvref_t<typename FmhaPipeline::QDataType>;
    using KDataType    = ck_tile::remove_cvref_t<typename FmhaPipeline::KDataType>;
    using VDataType    = ck_tile::remove_cvref_t<typename FmhaPipeline::VDataType>;
    using BiasDataType = ck_tile::remove_cvref_t<typename FmhaPipeline::BiasDataType>;
    using RandValOutputDataType =
        ck_tile::remove_cvref_t<typename FmhaPipeline::RandValOutputDataType>;
    using LSEDataType  = ck_tile::remove_cvref_t<typename FmhaPipeline::LSEDataType>;
    using ODataType    = ck_tile::remove_cvref_t<typename FmhaPipeline::ODataType>;
    using SaccDataType = ck_tile::remove_cvref_t<typename FmhaPipeline::SaccDataType>;
 
    using VLayout = ck_tile::remove_cvref_t<typename FmhaPipeline::VLayout>;
 
    static constexpr bool kIsGroupMode      = FmhaPipeline::kIsGroupMode;
    static constexpr bool kPadSeqLenQ       = FmhaPipeline::kPadSeqLenQ;
    static constexpr bool kPadSeqLenK       = FmhaPipeline::kPadSeqLenK;
    static constexpr bool kPadHeadDimQ      = FmhaPipeline::kPadHeadDimQ;
    static constexpr bool kPadHeadDimV      = FmhaPipeline::kPadHeadDimV;
    static constexpr bool kHasLogitsSoftCap = FmhaPipeline::kHasLogitsSoftCap;
    static constexpr auto BiasEnum          = FmhaPipeline::BiasEnum;
    static constexpr bool kStoreLSE         = FmhaPipeline::kStoreLSE;
    static constexpr bool kHasDropout       = FmhaPipeline::kHasDropout;
    static constexpr bool kDoFp8StaticQuant = FmhaPipeline::Problem::kDoFp8StaticQuant;
    using AttentionVariant = ck_tile::remove_cvref_t<typename FmhaPipeline::AttentionVariant>;
    using FmhaMask         = ck_tile::remove_cvref_t<typename FmhaPipeline::FmhaMask>;
    static constexpr bool kHasMask = FmhaMask::IsMasking;
 
    static constexpr bool kUseAsyncCopy = FmhaPipeline::Policy::AsyncCopy;
 
    // clang-format off
    template <typename T> struct t2s;
    template <> struct t2s<float> { static constexpr const char * name = "fp32"; };
    template <> struct t2s<ck_tile::fp16_t> { static constexpr const char * name = "fp16"; };
    template <> struct t2s<ck_tile::bf16_t> { static constexpr const char * name = "bf16"; };
    template <> struct t2s<ck_tile::fp8_t> { static constexpr const char * name = "fp8"; };
    template <> struct t2s<ck_tile::bf8_t> { static constexpr const char * name = "bf8"; };
    // clang-format on
 
    CK_TILE_HOST static std::string GetName()
    {
        // sync with generate.py
        // clang-format off
        using bfs = typename FmhaPipeline::BlockFmhaShape;
        using g0br = typename bfs::Gemm0BlockWarps;
        using g1br = typename bfs::Gemm1BlockWarps;
        using g0wt = typename bfs::Gemm0WarpTile;
        using g1wt = typename bfs::Gemm1WarpTile;
        #define _SS_  std::string
        #define _TS_  std::to_string
        auto pn = [&] () {
            std::string n;
            if (kPadSeqLenQ) n += "s";
            if (kPadSeqLenK) n += "sk";
            if (kPadHeadDimQ) n += "d";
            if (kPadHeadDimV) n += "dv";
            return n.empty() ? n : std::string("p") + n; }();
        return
            _SS_("fmha_batch_prefill_d") + _TS_(bfs::kQKHeaddim) + "_" + _SS_(t2s<QDataType>::name) +
            "_" + (kIsGroupMode ? "group" : "batch") + "_"
            "b" + _TS_(bfs::kM0) + "x" + _TS_(bfs::kN0) + "x" + _TS_(bfs::kK0) + "x" +
                    _TS_(bfs::kN1) + "x" + _TS_(bfs::kK1) + "x" + _TS_(bfs::kQKHeaddim) + "_" +
            "r" + _TS_(g0br::at(ck_tile::number<0>{})) + "x" + _TS_(g0br::at(ck_tile::number<1>{})) + "x" + _TS_(g0br::at(ck_tile::number<2>{})) + "_" +
            "r" + _TS_(g1br::at(ck_tile::number<0>{})) + "x" + _TS_(g1br::at(ck_tile::number<1>{})) + "x" + _TS_(g1br::at(ck_tile::number<2>{})) + "_" +
            "w" + _TS_(g0wt::at(ck_tile::number<0>{})) + "x" + _TS_(g0wt::at(ck_tile::number<1>{})) + "x" + _TS_(g0wt::at(ck_tile::number<2>{})) + "_" +
            "w" + _TS_(g1wt::at(ck_tile::number<0>{})) + "x" + _TS_(g1wt::at(ck_tile::number<1>{})) + "x" + _TS_(g1wt::at(ck_tile::number<2>{})) + "_" +
            (kBlockPerCuInput == -1 ? "" : ("o" + _TS_(kBlockPerCu) + "_")) + _SS_(FmhaPipeline::name) + "_" +
            "v" + (std::is_same_v<VLayout, ck_tile::tensor_layout::gemm::RowMajor> ? "r" : "c") + (pn.empty() ? "_npad" : "_" + pn) +
            (kHasLogitsSoftCap ? "_logits" : "_nlogits" ) + (BiasEnum == BlockAttentionBiasEnum::NO_BIAS ? _SS_("_nbias") : (_SS_("_") + BlockAttentionBiasEnumToStr<BiasEnum>::name)) +
            (kHasMask ? "_" + _SS_(FmhaMask::name) : "_nmask") + (kStoreLSE ? "_lse" : "_nlse" ) + (kHasDropout ? "_dropout" : "_ndropout" ) + (kDoFp8StaticQuant ? "_squant" : "_nsquant" );
        #undef _SS_
        #undef _TS_
        // clang-format on
    }
 
    template <ck_tile::index_t I> // to avoid duplicated base class prblem, introduce an template
                                  // arg
    struct FmhaFwdEmptyKargs
    {
    };
 
    // kargs use aggregate initializer, so no constructor will provided
    // use inheritance to minimize karg size
    // user need to use MakeKargs() function to create kargs.
    struct FmhaFwdCommonKargs
    {
        const void* q_ptr;
        const void* k_ptr;
        const void* v_ptr;
        void* o_ptr;
 
        ck_tile::index_t seqlen_q;
        ck_tile::index_t seqlen_k;
        ck_tile::index_t hdim_q;
        ck_tile::index_t hdim_v;
 
        ck_tile::index_t num_head_q;
        // for MQA/GQA, nhead could be different. This parameter is nhead_q / nhead_k
        // if this param is larger than 1, indicate MQA/GQA case
        ck_tile::index_t nhead_ratio_qk;
 
        int32_t num_total_pages;
        const int32_t* kv_indptr;
        const int32_t* kv_page_indices;
#if 0 // we assume page_block_size=1 for now
        const int32_t* kv_last_page_lens;
        ck_tile::index_t page_block_size;
#else
        static constexpr ck_tile::index_t page_block_size = 1;
#endif
 
        float scale_s;
 
        ck_tile::index_t stride_q;
        ck_tile::index_t stride_k;
        ck_tile::index_t stride_v;
        ck_tile::index_t stride_o;
 
        ck_tile::index_t nhead_stride_q;
        ck_tile::index_t nhead_stride_k;
        ck_tile::index_t nhead_stride_v;
        ck_tile::index_t nhead_stride_o;
    };
 
    struct FmhaFwdLogitsSoftCapKargs
    {
        FmhaFwdLogitsSoftCapKargs() = default;
 
        void init_logits_soft_cap(float logits_soft_cap_)
        {
            if(0 < logits_soft_cap_)
            {
                logits_soft_cap     = logits_soft_cap_;
                logits_soft_cap_rcp = 1.f / logits_soft_cap;
            }
            else
            {
                logits_soft_cap     = 0.f;
                logits_soft_cap_rcp = 0.f;
            }
        }
 
        float logits_soft_cap;
        float logits_soft_cap_rcp;
    };
 
    struct FmhaFwdCommonBiasKargs
    {
        const void* bias_ptr               = nullptr;
        ck_tile::index_t stride_bias       = 0;
        ck_tile::index_t nhead_stride_bias = 0;
    };
 
    struct FmhaFwdBatchModeBiasKargs : FmhaFwdCommonBiasKargs
    {
        ck_tile::index_t batch_stride_bias = 0;
    };
 
    struct FmhaFwdAlibiKargs
    {
        // alibi is batch*nhead*1, no matter in batch/group mode, they are the same
        const void* alibi_slope_ptr;
        ck_tile::index_t alibi_slope_stride; // stride in batch, or 0 for all batch share same slope
    };
 
    struct FmhaFwdMaskKargs
    {
        // ck_tile::index_t window_size_left, window_size_right;
        ck_tile::index_t window_size_left, window_size_right;
        ck_tile::GenericAttentionMaskEnum mask_type;
    };
 
    struct FmhaFwdFp8StaticQuantKargs
    {
        float scale_p;
        float scale_o;
    };
 
    struct FmhaFwdCommonLSEKargs
    {
        void* lse_ptr                     = nullptr;
        ck_tile::index_t nhead_stride_lse = 0;
        ck_tile::index_t batch_stride_lse = 0;
    };
 
    struct FmhaFwdDropoutSeedOffset
    {
        template <typename T>
        union ValueOrPointer
        {
            T val;
            const T* ptr;
        };
 
        ValueOrPointer<uint64_t> drop_seed;
        ValueOrPointer<uint64_t> drop_offset;
        bool is_drop_seed_offset_from_host;
    };
 
    struct FmhaFwdCommonDropoutKargs : FmhaFwdDropoutSeedOffset
    {
        void init_dropout(float p_drop, uint64_t seed, uint64_t offset)
        {
            float p_undrop = 1.0 - p_drop;
            p_undrop_in_uint8_t =
                uint8_t(std::floor(p_undrop * std::numeric_limits<uint8_t>::max()));
            rp_undrop = 1.0 / p_undrop;
 
            this->drop_seed.val                 = seed;
            this->drop_offset.val               = offset;
            this->is_drop_seed_offset_from_host = true;
        }
 
        void init_dropout(float p_drop, const uint64_t* seed_ptr, const uint64_t* offset_ptr)
        {
            float p_undrop = 1.0 - p_drop;
            p_undrop_in_uint8_t =
                uint8_t(std::floor(p_undrop * std::numeric_limits<uint8_t>::max()));
            rp_undrop = 1.0 / p_undrop;
 
            this->drop_seed.ptr                 = seed_ptr;
            this->drop_offset.ptr               = offset_ptr;
            this->is_drop_seed_offset_from_host = false;
        }
 
        float rp_undrop             = 1;
        uint8_t p_undrop_in_uint8_t = std::numeric_limits<uint8_t>::max();
        bool is_store_randval       = false;
        void* rand_val_ptr          = nullptr;
 
        ck_tile::index_t stride_randval       = 0;
        ck_tile::index_t nhead_stride_randval = 0;
    };
 
    struct FmhaFwdBatchModeDropoutKargs : FmhaFwdCommonDropoutKargs
    {
        ck_tile::index_t batch_stride_randval = 0;
    };
 
    struct FmhaFwdBatchModeKargs
        : FmhaFwdCommonKargs,
          std::conditional_t<BiasEnum == BlockAttentionBiasEnum::ELEMENTWISE_BIAS,
                             FmhaFwdBatchModeBiasKargs,
                             std::conditional_t<BiasEnum == BlockAttentionBiasEnum::ALIBI,
                                                FmhaFwdAlibiKargs,
                                                FmhaFwdEmptyKargs<0>>>,
          std::conditional_t<kHasMask, FmhaFwdMaskKargs, FmhaFwdEmptyKargs<1>>,
          std::conditional_t<kStoreLSE, FmhaFwdCommonLSEKargs, FmhaFwdEmptyKargs<2>>,
          std::conditional_t<kDoFp8StaticQuant, FmhaFwdFp8StaticQuantKargs, FmhaFwdEmptyKargs<3>>,
          std::conditional_t<kHasDropout, FmhaFwdBatchModeDropoutKargs, FmhaFwdEmptyKargs<4>>,
          std::conditional_t<kHasLogitsSoftCap, FmhaFwdLogitsSoftCapKargs, FmhaFwdEmptyKargs<5>>
    {
        ck_tile::index_t batch_stride_q;
        ck_tile::index_t batch_stride_k;
        ck_tile::index_t batch_stride_v;
        ck_tile::index_t batch_stride_o;
    };
 
    struct FmhaFwdGroupModeKargs
        : FmhaFwdCommonKargs,
          std::conditional_t<BiasEnum == BlockAttentionBiasEnum::ELEMENTWISE_BIAS,
                             FmhaFwdCommonBiasKargs,
                             std::conditional_t<BiasEnum == BlockAttentionBiasEnum::ALIBI,
                                                FmhaFwdAlibiKargs,
                                                FmhaFwdEmptyKargs<0>>>,
          std::conditional_t<kHasMask, FmhaFwdMaskKargs, FmhaFwdEmptyKargs<1>>,
          std::conditional_t<kStoreLSE, FmhaFwdCommonLSEKargs, FmhaFwdEmptyKargs<2>>,
          std::conditional_t<kDoFp8StaticQuant, FmhaFwdFp8StaticQuantKargs, FmhaFwdEmptyKargs<3>>,
          std::conditional_t<kHasDropout, FmhaFwdCommonDropoutKargs, FmhaFwdEmptyKargs<4>>,
          std::conditional_t<kHasLogitsSoftCap, FmhaFwdLogitsSoftCapKargs, FmhaFwdEmptyKargs<5>>
    {
        const int32_t* seqstart_q_ptr;
        ck_tile::index_t batch_stride_k;
        ck_tile::index_t batch_stride_v;
    };
 
    using Kargs = std::conditional_t<kIsGroupMode, FmhaFwdGroupModeKargs, FmhaFwdBatchModeKargs>;
 
    struct BlockIndices
    {
        ck_tile::index_t batch_idx;
        ck_tile::index_t qo_head_idx;
        ck_tile::index_t kv_head_idx;
    };
 
    template <bool Cond = !kIsGroupMode>
    CK_TILE_HOST static constexpr std::enable_if_t<Cond, Kargs>
    MakeKargs(const void* q_ptr,
              const void* k_ptr,
              const void* v_ptr,
              const void* bias_ptr,
              void* rand_val_ptr,
              void* lse_ptr,
              void* o_ptr,
              ck_tile::index_t seqlen_q,
              ck_tile::index_t hdim_q,
              ck_tile::index_t hdim_v,
              ck_tile::index_t num_head_q,
              ck_tile::index_t nhead_ratio_qk,
              int32_t num_total_pages,
              const void* kv_indptr,
              const void* kv_page_indices,
#if 0 // we assume page_block_size=1 for now
              const void* kv_last_page_lens,
              ck_tile::index_t page_block_size,
#endif
              float scale_s,
              float scale_p,
              float scale_o,
              float logits_soft_cap,
              ck_tile::index_t stride_q,
              ck_tile::index_t stride_k,
              ck_tile::index_t stride_v,
              ck_tile::index_t stride_bias,
              ck_tile::index_t stride_randval,
              ck_tile::index_t stride_o,
              ck_tile::index_t nhead_stride_q,
              ck_tile::index_t nhead_stride_k,
              ck_tile::index_t nhead_stride_v,
              ck_tile::index_t nhead_stride_bias,
              ck_tile::index_t nhead_stride_randval,
              ck_tile::index_t nhead_stride_lse,
              ck_tile::index_t nhead_stride_o,
              ck_tile::index_t batch_stride_q,
              ck_tile::index_t batch_stride_k,
              ck_tile::index_t batch_stride_v,
              ck_tile::index_t batch_stride_bias,
              ck_tile::index_t batch_stride_randval,
              ck_tile::index_t batch_stride_lse,
              ck_tile::index_t batch_stride_o,
              ck_tile::index_t window_size_left,
              ck_tile::index_t window_size_right,
              ck_tile::index_t mask_type,
              float p_drop,
              bool s_randval,
              std::variant<std::pair<uint64_t, uint64_t>, std::pair<const void*, const void*>>
                  drop_seed_offset)
    {
        Kargs kargs{{q_ptr,
                     k_ptr,
                     v_ptr,
                     o_ptr,
                     seqlen_q,
                     -1,
                     hdim_q,
                     hdim_v,
                     num_head_q,
                     nhead_ratio_qk,
                     num_total_pages,
                     reinterpret_cast<const int32_t*>(kv_indptr),
                     reinterpret_cast<const int32_t*>(kv_page_indices),
#if 0 // we assume page_block_size=1 for now
                     reinterpret_cast<const int32_t*>(kv_last_page_lens),
                     page_block_size,
#endif
#if CK_TILE_FMHA_FWD_FAST_EXP2
                     static_cast<float>(scale_s * ck_tile::log2e_v<>),
#else
                     scale_s,
#endif
                     stride_q,
                     stride_k,
                     stride_v,
                     stride_o,
                     nhead_stride_q,
                     nhead_stride_k,
                     nhead_stride_v,
                     nhead_stride_o}, // args for common karg
                    {},               // placeholder for bias
                    {},               // placeholder for mask
                    {},               // placeholder for lse
                    {},               // placeholder for fp8_static_quant args
                    {},               // placeholder for dropout
                    {},               // placeholder for logits_soft_cap
                    batch_stride_q,
                    batch_stride_k,
                    batch_stride_v,
                    batch_stride_o};
 
        if constexpr(BiasEnum == BlockAttentionBiasEnum::ELEMENTWISE_BIAS)
        {
            kargs.bias_ptr          = bias_ptr;
            kargs.stride_bias       = stride_bias;
            kargs.nhead_stride_bias = nhead_stride_bias;
            kargs.batch_stride_bias = batch_stride_bias;
        }
        else if constexpr(BiasEnum == BlockAttentionBiasEnum::ALIBI)
        {
            kargs.alibi_slope_ptr    = bias_ptr;
            kargs.alibi_slope_stride = stride_bias;
        }
        if constexpr(kHasMask)
        {
            kargs.window_size_left  = window_size_left;
            kargs.window_size_right = window_size_right;
            kargs.mask_type         = static_cast<ck_tile::GenericAttentionMaskEnum>(mask_type);
        }
        if constexpr(kStoreLSE)
        {
            kargs.lse_ptr          = lse_ptr;
            kargs.nhead_stride_lse = nhead_stride_lse;
            kargs.batch_stride_lse = batch_stride_lse;
        }
        if constexpr(kDoFp8StaticQuant)
        {
            kargs.scale_p = scale_p;
            kargs.scale_o = scale_o;
        }
        if constexpr(kHasDropout)
        {
            if(drop_seed_offset.index() == 0) // seed & offset come from host
            {
                const auto& [seed, offset] = std::get<0>(drop_seed_offset);
                kargs.init_dropout(p_drop, seed, offset);
            }
            else // seed & offset come from device
            {
                const auto& [seed_ptr, offset_ptr] = std::get<1>(drop_seed_offset);
                kargs.init_dropout(p_drop,
                                   reinterpret_cast<const uint64_t*>(seed_ptr),
                                   reinterpret_cast<const uint64_t*>(offset_ptr));
            }
 
            kargs.rand_val_ptr         = rand_val_ptr;
            kargs.stride_randval       = stride_randval;
            kargs.nhead_stride_randval = nhead_stride_randval;
            kargs.batch_stride_randval = batch_stride_randval;
            kargs.is_store_randval     = s_randval;
        }
        if constexpr(kHasLogitsSoftCap)
        {
            kargs.init_logits_soft_cap(logits_soft_cap);
        }
 
        return kargs;
    }
 
    template <bool Cond = kIsGroupMode>
    CK_TILE_HOST static constexpr std::enable_if_t<Cond, Kargs>
    MakeKargs(const void* q_ptr,
              const void* k_ptr,
              const void* v_ptr,
              const void* bias_ptr,
              void* rand_val_ptr,
              void* lse_ptr,
              void* o_ptr,
              const void* seqstart_q_ptr,
              ck_tile::index_t hdim_q,
              ck_tile::index_t hdim_v,
              ck_tile::index_t num_head_q,
              ck_tile::index_t nhead_ratio_qk,
              int32_t num_total_pages,
              const void* kv_indptr,
              const void* kv_page_indices,
#if 0 // we assume page_block_size=1 for now
              const void* kv_last_page_lens,
              ck_tile::index_t page_block_size,
#endif
              float scale_s,
              float scale_p,
              float scale_o,
              float logits_soft_cap,
              ck_tile::index_t stride_q,
              ck_tile::index_t stride_k,
              ck_tile::index_t stride_v,
              ck_tile::index_t stride_bias,
              ck_tile::index_t stride_randval,
              ck_tile::index_t stride_o,
              ck_tile::index_t nhead_stride_q,
              ck_tile::index_t nhead_stride_k,
              ck_tile::index_t nhead_stride_v,
              ck_tile::index_t nhead_stride_bias,
              ck_tile::index_t nhead_stride_randval,
              ck_tile::index_t nhead_stride_lse,
              ck_tile::index_t nhead_stride_o,
              ck_tile::index_t batch_stride_k,
              ck_tile::index_t batch_stride_v,
              ck_tile::index_t window_size_left,
              ck_tile::index_t window_size_right,
              ck_tile::index_t mask_type,
              float p_drop,
              bool s_randval,
              std::variant<std::pair<uint64_t, uint64_t>, std::pair<const void*, const void*>>
                  drop_seed_offset)
    {
        Kargs kargs{{q_ptr,
                     k_ptr,
                     v_ptr,
                     o_ptr,
                     -1, // seqlen will be updated by another pointer
                     -1, //
                     hdim_q,
                     hdim_v,
                     num_head_q,
                     nhead_ratio_qk,
                     num_total_pages,
                     reinterpret_cast<const int32_t*>(kv_indptr),
                     reinterpret_cast<const int32_t*>(kv_page_indices),
#if 0 // we assume page_block_size=1 for now
                     reinterpret_cast<const int32_t*>(kv_last_page_lens),
                     page_block_size,
#endif
#if CK_TILE_FMHA_FWD_FAST_EXP2
                     static_cast<float>(scale_s * ck_tile::log2e_v<>),
#else
                     scale_s,
#endif
                     stride_q,
                     stride_k,
                     stride_v,
                     stride_o,
                     nhead_stride_q,
                     nhead_stride_k,
                     nhead_stride_v,
                     nhead_stride_o}, // args for common karg
                    {},               // placeholder for bias
                    {},               // placeholder for mask
                    {},               // placeholder for lse
                    {},               // placeholder for fp8_static_quant args
                    {},               // placeholder for dropout
                    {},               // placeholder for logits_soft_cap
                    reinterpret_cast<const int32_t*>(seqstart_q_ptr),
                    batch_stride_k,
                    batch_stride_v};
 
        if constexpr(BiasEnum == BlockAttentionBiasEnum::ELEMENTWISE_BIAS)
        {
            kargs.bias_ptr          = bias_ptr;
            kargs.stride_bias       = stride_bias;
            kargs.nhead_stride_bias = nhead_stride_bias;
        }
        else if constexpr(BiasEnum == BlockAttentionBiasEnum::ALIBI)
        {
            kargs.alibi_slope_ptr    = bias_ptr;
            kargs.alibi_slope_stride = stride_bias;
        }
        if constexpr(kHasMask)
        {
            kargs.window_size_left  = window_size_left;
            kargs.window_size_right = window_size_right;
            kargs.mask_type         = static_cast<ck_tile::GenericAttentionMaskEnum>(mask_type);
        }
        if constexpr(kStoreLSE)
        {
            kargs.lse_ptr          = lse_ptr;
            kargs.nhead_stride_lse = nhead_stride_lse;
        }
        if constexpr(kDoFp8StaticQuant)
        {
            kargs.scale_p = scale_p;
            kargs.scale_o = scale_o;
        }
        if constexpr(kHasDropout)
        {
            if(drop_seed_offset.index() == 0) // seed & offset come from host
            {
                const auto& [seed, offset] = std::get<0>(drop_seed_offset);
                kargs.init_dropout(p_drop, seed, offset);
            }
            else // seed & offset come from device
            {
                const auto& [seed_ptr, offset_ptr] = std::get<1>(drop_seed_offset);
                kargs.init_dropout(p_drop,
                                   reinterpret_cast<const uint64_t*>(seed_ptr),
                                   reinterpret_cast<const uint64_t*>(offset_ptr));
            }
 
            kargs.rand_val_ptr         = rand_val_ptr;
            kargs.stride_randval       = stride_randval;
            kargs.nhead_stride_randval = nhead_stride_randval;
            kargs.is_store_randval     = s_randval;
        }
        if constexpr(kHasLogitsSoftCap)
        {
            kargs.init_logits_soft_cap(logits_soft_cap);
        }
 
        return kargs;
    }
 
    CK_TILE_HOST static constexpr auto GridSize(ck_tile::index_t batch_size_,
                                                ck_tile::index_t nhead_,
                                                ck_tile::index_t seqlen_q_,
                                                ck_tile::index_t hdim_v_)
    {
        if constexpr(kIsGroupMode)
        {
            // TODO: this may need tuning
            return dim3(nhead_,
                        batch_size_,
                        ck_tile::integer_divide_ceil(seqlen_q_, FmhaPipeline::kM0) *
                            ck_tile::integer_divide_ceil(hdim_v_, FmhaPipeline::kN1));
        }
        else
        {
            // TODO: this may need tuning
            return dim3(ck_tile::integer_divide_ceil(seqlen_q_, FmhaPipeline::kM0) *
                            ck_tile::integer_divide_ceil(hdim_v_, FmhaPipeline::kN1),
                        nhead_,
                        batch_size_);
        }
    }
 
    CK_TILE_DEVICE static constexpr auto GetTileIndex(const Kargs& kargs)
    {
        if constexpr(kIsGroupMode)
        {
            // const index_t num_tile_m0 = seqlen_q / kM0;
            const index_t num_tile_n1 =
                ck_tile::integer_divide_ceil(kargs.hdim_v, FmhaPipeline::kN1);
 
            const index_t i_block = blockIdx.z;
            const index_t i_nhead = blockIdx.x;
            const index_t i_batch = blockIdx.y;
 
            const auto f = [](index_t dividend, index_t divisor) {
                index_t quotient = dividend / divisor;
                index_t modulus  = dividend - quotient * divisor;
                return ck_tile::make_tuple(quotient, modulus);
            };
 
            const auto [i_tile_m, i_tile_n] = f(i_block, num_tile_n1);
            if constexpr(kHasMask)
            {
                // assume that num_tile_n1 is always 1
                return ck_tile::make_tuple(gridDim.z - 1 - i_tile_m, i_tile_n, i_nhead, i_batch);
            }
            else
            {
                return ck_tile::make_tuple(i_tile_m, i_tile_n, i_nhead, i_batch);
            }
        }
        else
        {
            // const index_t num_tile_m0 = seqlen_q / kM0;
            const index_t num_tile_n1 =
                ck_tile::integer_divide_ceil(kargs.hdim_v, FmhaPipeline::kN1);
 
            const index_t i_block = blockIdx.x;
            const index_t i_nhead = blockIdx.y;
            const index_t i_batch = blockIdx.z;
 
            const auto f = [](index_t dividend, index_t divisor) {
                index_t quotient = dividend / divisor;
                index_t modulus  = dividend - quotient * divisor;
                return ck_tile::make_tuple(quotient, modulus);
            };
 
            const auto [i_tile_m, i_tile_n] = f(i_block, num_tile_n1);
 
            if constexpr(kHasMask)
            {
                // assume that num_tile_n1 is always 1
                return ck_tile::make_tuple(gridDim.x - 1 - i_tile_m, i_tile_n, i_nhead, i_batch);
            }
            else
            {
                return ck_tile::make_tuple(i_tile_m, i_tile_n, i_nhead, i_batch);
            }
        }
    }
 
    CK_TILE_HOST static dim3 BlockSize()
    {
        if(is_wave32())
        {
            return dim3(kBlockSize / 2);
        }
        else
        {
            return dim3(kBlockSize);
        }
    }
 
    CK_TILE_HOST_DEVICE static constexpr ck_tile::index_t GetSmemSize()
    {
        return ck_tile::max(FmhaPipeline::GetSmemSize(), EpiloguePipeline::GetSmemSize());
    }
 
    CK_TILE_DEVICE void operator()(Kargs kargs) const
    {
        // allocate LDS
        __shared__ char smem_ptr[GetSmemSize()];
 
        // divide problem
        const auto [i_tile_m, i_tile_n, i_nhead, i_batch] = GetTileIndex(kargs);
 
        const index_t i_m0 = amd_wave_read_first_lane(i_tile_m * FmhaPipeline::kM0);
        const index_t i_n1 = amd_wave_read_first_lane(i_tile_n * FmhaPipeline::kN1);
 
        long_index_t batch_offset_q       = 0;
        long_index_t batch_offset_bias    = 0;
        long_index_t batch_offset_randval = 0;
        long_index_t batch_offset_lse     = 0;
        long_index_t batch_offset_o       = 0;
 
        const int32_t num_page_blocks = kargs.kv_indptr[i_batch + 1] - kargs.kv_indptr[i_batch];
#if 0 // we assume page_block_size=1 for now
        const int32_t last_page_len   = kargs.kv_last_page_lens[i_batch];
#endif
        if constexpr(kIsGroupMode)
        {
            // get starting offset for each batch
            const long_index_t query_start = kargs.seqstart_q_ptr[i_batch];
 
            batch_offset_q = query_start * kargs.stride_q;
 
            kargs.kv_page_indices += kargs.kv_indptr[i_batch];
 
            if constexpr(BiasEnum == BlockAttentionBiasEnum::ELEMENTWISE_BIAS)
            {
                batch_offset_bias = query_start * kargs.stride_bias;
            }
            if constexpr(kStoreLSE)
            {
                batch_offset_lse = query_start;
            }
            if constexpr(kHasDropout)
            {
                batch_offset_randval = query_start * kargs.stride_randval;
            }
            batch_offset_o = query_start * kargs.stride_o;
 
            // get real # queries & # keys under group mode
            kargs.seqlen_q = kargs.seqstart_q_ptr[i_batch + 1] - query_start;
 
            // # of required blocks is different in each groups, terminate unnecessary blocks
            // earlier
            if(kargs.seqlen_q <= i_m0)
            {
                return;
            }
 
#if 0 // we assume page_block_size=1 for now
            kargs.seqlen_k = (num_page_blocks - 1) * kargs.page_block_size + last_page_len;
#else
            kargs.seqlen_k = num_page_blocks;
#endif
        }
        else
        {
            batch_offset_q = static_cast<long_index_t>(i_batch) * kargs.batch_stride_q;
 
            kargs.kv_page_indices += kargs.kv_indptr[i_batch];
 
            if constexpr(BiasEnum == BlockAttentionBiasEnum::ELEMENTWISE_BIAS)
            {
                batch_offset_bias = static_cast<long_index_t>(i_batch) * kargs.batch_stride_bias;
            }
            if constexpr(kStoreLSE)
            {
                batch_offset_lse = static_cast<long_index_t>(i_batch) * kargs.batch_stride_lse;
            }
            if constexpr(kHasDropout)
            {
                batch_offset_randval =
                    static_cast<long_index_t>(i_batch) * kargs.batch_stride_randval;
            }
            batch_offset_o = static_cast<long_index_t>(i_batch) * kargs.batch_stride_o;
 
#if 0 // we assume page_block_size=1 for now
            kargs.seqlen_k = (num_page_blocks - 1) * kargs.page_block_size + last_page_len;
#else
            kargs.seqlen_k = num_page_blocks;
#endif
        }
 
        // for simplicity, batch stride we just modify the pointer
        const QDataType* q_ptr = reinterpret_cast<const QDataType*>(kargs.q_ptr) +
                                 static_cast<long_index_t>(i_nhead) * kargs.nhead_stride_q +
                                 batch_offset_q;
        const KDataType* k_ptr =
            reinterpret_cast<const KDataType*>(kargs.k_ptr) +
            static_cast<long_index_t>(i_nhead / kargs.nhead_ratio_qk) * kargs.nhead_stride_k;
        const VDataType* v_ptr =
            reinterpret_cast<const VDataType*>(kargs.v_ptr) +
            static_cast<long_index_t>(i_nhead / kargs.nhead_ratio_qk) * kargs.nhead_stride_v;
        ODataType* o_ptr = reinterpret_cast<ODataType*>(kargs.o_ptr) +
                           static_cast<long_index_t>(i_nhead) * kargs.nhead_stride_o +
                           batch_offset_o;
 
        // Q/K/V DRAM and DRAM window
        const auto q_dram = [&]() {
            const auto q_dram_naive = make_naive_tensor_view<address_space_enum::global>(
                q_ptr,
                make_tuple(kargs.seqlen_q, kargs.hdim_q),
                make_tuple(kargs.stride_q, 1),
                number<FmhaPipeline::kAlignmentQ>{},
                number<1>{});
            if constexpr(FmhaPipeline::kQLoadOnce)
            {
                return pad_tensor_view(
                    q_dram_naive,
                    make_tuple(number<FmhaPipeline::kM0>{}, number<FmhaPipeline::kSubQKHeaddim>{}),
                    sequence<kPadSeqLenQ, kPadHeadDimQ>{});
            }
            else
            {
                return pad_tensor_view(
                    q_dram_naive,
                    make_tuple(number<FmhaPipeline::kM0>{}, number<FmhaPipeline::kK0>{}),
                    sequence<kPadSeqLenQ, kPadHeadDimQ>{});
            }
        }();
        const auto k_dram = [&]() {
            const auto k_dram_naive = make_naive_tensor_view<address_space_enum::global>(
                k_ptr,
                make_tuple(kargs.num_total_pages * kargs.page_block_size, kargs.hdim_q),
                make_tuple(kargs.stride_k, 1),
                number<FmhaPipeline::kAlignmentK>{},
                number<1>{});
 
            constexpr bool kPadSeqLenK_ = kUseAsyncCopy ? kPadSeqLenK : true;
            return pad_tensor_view(
                k_dram_naive,
                make_tuple(number<FmhaPipeline::kN0>{}, number<FmhaPipeline::kK0>{}),
                sequence<kPadSeqLenK_, kPadHeadDimQ>{});
        }();
        const auto v_dram = [&]() {
            if constexpr(std::is_same_v<VLayout, ck_tile::tensor_layout::gemm::RowMajor>)
            {
                const auto v_dram_naive = make_naive_tensor_view<address_space_enum::global>(
                    v_ptr,
                    make_tuple(kargs.num_total_pages * kargs.page_block_size, kargs.hdim_v),
                    make_tuple(kargs.stride_v, 1),
                    number<FmhaPipeline::kAlignmentV>{},
                    number<1>{});
 
                const auto v_dram_transposed = transform_tensor_view(
                    v_dram_naive,
                    make_tuple(
                        make_pass_through_transform(kargs.hdim_v),
                        make_pass_through_transform(kargs.num_total_pages * kargs.page_block_size)),
                    make_tuple(sequence<1>{}, sequence<0>{}),
                    make_tuple(sequence<0>{}, sequence<1>{}));
 
                constexpr bool kPadSeqLenK_ = kUseAsyncCopy ? kPadSeqLenK : true;
                return pad_tensor_view(
                    v_dram_transposed,
                    make_tuple(number<FmhaPipeline::kN1>{}, number<FmhaPipeline::kK1>{}),
                    sequence<kPadHeadDimV, kPadSeqLenK_>{});
            }
            else
            {
                const auto v_dram_naive = make_naive_tensor_view<address_space_enum::global>(
                    v_ptr,
                    make_tuple(kargs.hdim_v, kargs.num_total_pages * kargs.page_block_size),
                    make_tuple(kargs.stride_v, 1),
                    number<FmhaPipeline::kAlignmentV>{},
                    number<1>{});
 
                constexpr bool kPadHeadDimV_ = kUseAsyncCopy ? kPadHeadDimV : false;
                return pad_tensor_view(
                    v_dram_naive,
                    make_tuple(number<FmhaPipeline::kN1>{}, number<FmhaPipeline::kK1>{}),
                    sequence<kPadHeadDimV_, kPadSeqLenK>{});
            }
        }();
 
        auto q_dram_window = make_tile_window(
            q_dram,
            [&]() {
                if constexpr(FmhaPipeline::kQLoadOnce)
                    return make_tuple(number<FmhaPipeline::kM0>{},
                                      number<FmhaPipeline::kSubQKHeaddim>{});
                else
                    return make_tuple(number<FmhaPipeline::kM0>{}, number<FmhaPipeline::kK0>{});
            }(),
            {i_m0, 0});
 
        auto k_dram_window = make_tile_window(
            k_dram, make_tuple(number<FmhaPipeline::kN0>{}, number<FmhaPipeline::kK0>{}), {0, 0});
 
        auto v_dram_window =
            make_tile_window(v_dram,
                             make_tuple(number<FmhaPipeline::kN1>{}, number<FmhaPipeline::kK1>{}),
                             {i_n1, 0});
        const auto bias_dram_window = [&, i_nhead_ = i_nhead]() {
            constexpr auto bias_dram_window_lengths =
                make_tuple(number<FmhaPipeline::kM0>{}, number<FmhaPipeline::kN0>{});
            if constexpr(BiasEnum == BlockAttentionBiasEnum::ELEMENTWISE_BIAS)
            {
                const BiasDataType* bias_ptr =
                    reinterpret_cast<const BiasDataType*>(kargs.bias_ptr) +
                    static_cast<long_index_t>(i_nhead_) * kargs.nhead_stride_bias +
                    batch_offset_bias;
 
                const auto bias_dram = [&]() {
                    const auto bias_dram_naive = make_naive_tensor_view<address_space_enum::global>(
                        bias_ptr,
                        make_tuple(kargs.seqlen_q, kargs.seqlen_k),
                        make_tuple(kargs.stride_bias, 1),
                        number<FmhaPipeline::kAlignmentBias>{},
                        number<1>{});
 
                    return pad_tensor_view(bias_dram_naive,
                                           bias_dram_window_lengths,
                                           sequence<kPadSeqLenQ, kPadSeqLenK>{});
                }();
 
                return make_tile_window(bias_dram, bias_dram_window_lengths, {i_m0, 0});
            }
            else
            {
                return make_null_tile_window(bias_dram_window_lengths);
            }
        }();
 
        // lse
        auto lse_dram_window = [&, i_nhead_ = i_nhead]() {
            constexpr auto lse_dram_window_lengths = make_tuple(number<FmhaPipeline::kM0>{});
            if constexpr(kStoreLSE)
            {
                LSEDataType* lse_ptr =
                    reinterpret_cast<LSEDataType*>(kargs.lse_ptr) +
                    static_cast<long_index_t>(i_nhead_) * kargs.nhead_stride_lse + batch_offset_lse;
 
                const auto lse_dram = [&]() {
                    const auto lse_dram_naive = make_naive_tensor_view<address_space_enum::global>(
                        lse_ptr,
                        make_tuple(kargs.seqlen_q),
                        make_tuple(1),
                        number<1>{},
                        number<1>{});
 
                    return pad_tensor_view(
                        lse_dram_naive, lse_dram_window_lengths, sequence<kPadSeqLenQ>{});
                }();
 
                return make_tile_window(lse_dram, lse_dram_window_lengths, {i_m0});
            }
            else
            {
                return make_null_tile_window(lse_dram_window_lengths);
            }
        }();
 
        auto dropout = [&, i_nhead_ = i_nhead, i_batch_ = i_batch]() {
            if constexpr(kHasDropout)
            {
                return BlockDropout{i_batch_,
                                    i_nhead_,
                                    kargs.num_head_q,
                                    kargs.is_drop_seed_offset_from_host ? kargs.drop_seed.val
                                                                        : *kargs.drop_seed.ptr,
                                    kargs.is_drop_seed_offset_from_host ? kargs.drop_offset.val
                                                                        : *kargs.drop_offset.ptr,
                                    kargs.rp_undrop,
                                    kargs.p_undrop_in_uint8_t,
                                    kargs.is_store_randval};
            }
            else
            {
                return NullBlockDropout{};
            };
        }();
 
        auto randval_dram_window = [&, i_nhead_ = i_nhead]() {
            constexpr auto randval_dram_window_lengths =
                make_tuple(number<FmhaPipeline::kM0>{}, number<FmhaPipeline::kN0>{});
            if constexpr(kHasDropout)
            {
                RandValOutputDataType* rand_val_ptr =
                    reinterpret_cast<RandValOutputDataType*>(kargs.rand_val_ptr) +
                    static_cast<long_index_t>(i_nhead_) * kargs.nhead_stride_randval +
                    batch_offset_randval;
 
                const auto randval_dram = [&]() {
                    const auto randval_dram_naive =
                        make_naive_tensor_view<address_space_enum::global>(
                            rand_val_ptr,
                            make_tuple(kargs.seqlen_q, kargs.seqlen_k),
                            make_tuple(kargs.stride_randval, 1),
                            number<1>{},
                            number<1>{});
 
                    return pad_tensor_view(randval_dram_naive,
                                           randval_dram_window_lengths,
                                           sequence<kPadSeqLenQ, kPadSeqLenK>{});
                }();
 
                return make_tile_window(randval_dram, randval_dram_window_lengths, {i_m0, 0});
            }
            else
            {
                return make_null_tile_window(randval_dram_window_lengths);
            }
        }();
 
        FmhaMask mask = [&]() {
            if constexpr(kHasMask)
                return ck_tile::make_generic_attention_mask_from_lr_window<FmhaMask>(
                    kargs.window_size_left,
                    kargs.window_size_right,
                    kargs.seqlen_q,
                    kargs.seqlen_k,
                    kargs.mask_type == GenericAttentionMaskEnum::MASK_FROM_TOP_LEFT);
            else
                return FmhaMask{kargs.seqlen_q, kargs.seqlen_k};
        }();
 
        // WA i_batch capture structure binding before c++20
        auto position_encoding = [&, i_batch_ = i_batch, i_nhead_ = i_nhead]() {
            if constexpr(BiasEnum == BlockAttentionBiasEnum::ALIBI)
            {
                // data loading, shared by entire wg
                // TODO: how to use s_read?
                SaccDataType slope =
                    *(reinterpret_cast<const SaccDataType*>(kargs.alibi_slope_ptr) +
                      i_batch_ * kargs.alibi_slope_stride + i_nhead_);
#if CK_TILE_FMHA_FWD_FAST_EXP2
                slope *= ck_tile::log2e_v<>;
#endif
                if constexpr(kHasMask)
                {
                    return make_alibi_from_lr_mask<SaccDataType, true>(slope,
                                                                       kargs.window_size_left,
                                                                       kargs.window_size_right,
                                                                       kargs.seqlen_q,
                                                                       kargs.seqlen_k,
                                                                       kargs.mask_type);
                }
                else
                {
                    return Alibi<SaccDataType, true>{
                        slope, kargs.seqlen_q, kargs.seqlen_k, AlibiMode::FROM_BOTTOM_RIGHT};
                }
            }
            else
            {
                return EmptyPositionEncoding<SaccDataType>{};
            }
        }();
 
        AttentionVariant variant;
        const auto variant_params = [&] {
            if constexpr(kHasLogitsSoftCap)
            {
                return ck_tile::LogitsSoftCapParams<FmhaMask, CK_TILE_FMHA_FWD_FAST_EXP2>{
                    mask, kargs.scale_s, kargs.logits_soft_cap, kargs.logits_soft_cap_rcp};
            }
            else
            {
                return ck_tile::StandardAttentionParams<FmhaMask>{mask, kargs.scale_s};
            }
        }();
 
        BlockIndices block_indices{i_batch, i_nhead, i_nhead / kargs.nhead_ratio_qk};
 
        auto o_acc_tile = [&]() {
            if constexpr(kDoFp8StaticQuant)
            {
                return FmhaPipeline{}(
                    q_dram_window,
                    identity{}, // q_element_func
                    k_dram_window,
                    identity{}, // k_element_func
                    v_dram_window,
                    identity{}, // v_element_func
                    bias_dram_window,
                    identity{}, // bias_element_func
                    randval_dram_window,
                    lse_dram_window,
                    identity{},                                          // lse_element_func
                    identity{},                                          // s_acc_element_func
                    scales{kargs.scale_p},                               // p_compute_element_func
                    composes(saturates<fp8_t>{}, scales{kargs.scale_o}), // o_acc_element_func
                    mask,
                    position_encoding,
                    kargs.scale_s,
                    variant,
                    variant_params,
                    block_indices,
                    smem_ptr,
                    kargs.kv_page_indices,
                    kargs.stride_k,
                    kargs.stride_v,
                    dropout);
            }
            else
            {
                return FmhaPipeline{}(q_dram_window,
                                      k_dram_window,
                                      v_dram_window,
                                      bias_dram_window,
                                      randval_dram_window,
                                      lse_dram_window,
                                      mask,
                                      position_encoding,
                                      kargs.scale_s,
                                      variant,
                                      variant_params,
                                      block_indices,
                                      smem_ptr,
                                      kargs.kv_page_indices,
                                      kargs.stride_k,
                                      kargs.stride_v,
                                      dropout);
            }
        }();
 
        // O DRAM and O DRAM window
        auto o_dram = [&]() {
            const auto o_dram_naive = make_naive_tensor_view<address_space_enum::global>(
                o_ptr,
                make_tuple(kargs.seqlen_q, kargs.hdim_v),
                make_tuple(kargs.stride_o, 1),
                number<FmhaPipeline::kAlignmentO>{},
                number<1>{});
 
            return pad_tensor_view(
                o_dram_naive,
                make_tuple(number<FmhaPipeline::kM0>{}, number<FmhaPipeline::kN1>{}),
                sequence<kPadSeqLenQ, kPadHeadDimV>{});
        }();
 
        auto o_dram_window =
            make_tile_window(o_dram,
                             make_tuple(number<FmhaPipeline::kM0>{}, number<FmhaPipeline::kN1>{}),
                             {i_m0, i_n1});
 
        EpiloguePipeline{}(o_dram_window, o_acc_tile, nullptr);
    }
};
 
} // namespace ck_tile