# Copyright 2023-2024 SGLang Team
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#     http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
# ==============================================================================
"""
Memory-efficient attention for decoding.
It supports page size = 1.
"""

# Adapted from
# https://github.com/ModelTC/lightllm/blob/f2a54f0912293f683bf1d1695fd12c4098a5bf82/lightllm/models/llama/triton_kernel/token_attention_nopad_att1.py
# https://github.com/ModelTC/lightllm/blob/f2a54f0912293f683bf1d1695fd12c4098a5bf82/lightllm/models/llama/triton_kernel/token_attention_softmax_and_reducev.py
import triton
import triton.language as tl

from sglang.srt.utils import is_hip


@triton.jit
def tanh(x):
    # Tanh is just a scaled sigmoid
    return 2 * tl.sigmoid(2 * x) - 1


@triton.jit
def _fwd_kernel_stage1(
    Q,
    K_Buffer,
    sm_scale,
    Req_to_tokens,
    B_req_idx,
    B_Start_Loc,
    B_Seqlen,
    Att_Out,
    stride_req_to_tokens_b,
    stride_qbs,
    stride_qh,
    stride_buf_kbs,
    stride_buf_kh,
    att_stride_h,
    kv_group_num: tl.constexpr,
    BLOCK_DMODEL: tl.constexpr,
    BLOCK_N: tl.constexpr,
    logit_cap: tl.constexpr,
    Lk: tl.constexpr,
):
    cur_batch = tl.program_id(0)
    cur_head = tl.program_id(1)
    start_n = tl.program_id(2)

    reduce_dtype = Att_Out.dtype.element_ty
    cur_kv_head = cur_head // kv_group_num

    offs_d = tl.arange(0, BLOCK_DMODEL)
    cur_batch_seq_len = tl.load(B_Seqlen + cur_batch)
    cur_batch_in_all_start_index = tl.load(B_Start_Loc + cur_batch)
    cur_batch_req_idx = tl.load(B_req_idx + cur_batch)

    cur_batch_start_index = 0
    cur_batch_end_index = cur_batch_seq_len

    off_q = cur_batch * stride_qbs + cur_head * stride_qh + offs_d

    offs_n = start_n * BLOCK_N + tl.arange(0, BLOCK_N)

    block_stard_index = start_n * BLOCK_N
    block_mask = tl.where(block_stard_index < cur_batch_seq_len, 1, 0)

    for start_mark in range(0, block_mask, 1):
        q = tl.load(Q + off_q + start_mark).to(reduce_dtype)
        offs_n_new = cur_batch_start_index + offs_n
        k_loc = tl.load(
            Req_to_tokens + stride_req_to_tokens_b * cur_batch_req_idx + offs_n_new,
            mask=offs_n_new < cur_batch_end_index,
            other=0,
        )
        offs_buf_k = (
            k_loc[:, None] * stride_buf_kbs
            + cur_kv_head * stride_buf_kh
            + offs_d[None, :]
        )
        k = tl.load(
            K_Buffer + offs_buf_k,
            mask=(offs_n_new[:, None] < cur_batch_end_index) & (offs_d[None, :] < Lk),
            other=0.0,
        ).to(reduce_dtype)
        att_value = tl.sum(q[None, :] * k, 1)
        att_value *= sm_scale

        if logit_cap > 0:
            att_value = logit_cap * tanh(att_value / logit_cap)

        off_o = cur_head * att_stride_h + (cur_batch_in_all_start_index + offs_n)
        tl.store(Att_Out + off_o, att_value, mask=offs_n_new < cur_batch_end_index)


@triton.jit
def _fwd_kernel_stage2(
    logits,
    V_Buffer,
    Out,
    Req_to_tokens,
    B_req_idx,
    B_Start_Loc,
    B_Seqlen,
    stride_logic_h,
    stride_buf_vbs,
    stride_buf_vh,
    stride_obs,
    stride_oh,
    stride_req_to_token_b,
    kv_group_num: tl.constexpr,
    BLOCK_DMODEL: tl.constexpr,
    BLOCK_N: tl.constexpr,
    Lv: tl.constexpr,
):
    cur_batch = tl.program_id(0)
    cur_head = tl.program_id(1)

    cur_kv_head = cur_head // kv_group_num

    cur_batch_seq_len = tl.load(B_Seqlen + cur_batch)
    cur_batch_start_loc = tl.load(B_Start_Loc + cur_batch)
    cur_batch_req_idx = tl.load(B_req_idx + cur_batch)

    offs_n = tl.arange(0, BLOCK_N)
    offs_d = tl.arange(0, BLOCK_DMODEL)

    offs_buf_v = cur_kv_head * stride_buf_vh + offs_d[None, :]
    v_ptrs = V_Buffer + offs_buf_v

    e_max = float("-inf")
    e_sum = 0.0
    acc = tl.zeros([BLOCK_DMODEL], dtype=tl.float32)

    for start_n in range(0, cur_batch_seq_len, BLOCK_N):
        start_n = tl.multiple_of(start_n, BLOCK_N)
        v_index = tl.load(
            Req_to_tokens
            + cur_batch_req_idx * stride_req_to_token_b
            + (start_n + offs_n),
            mask=(start_n + offs_n) < cur_batch_seq_len,
            other=0,
        )

        qk = tl.load(
            logits
            + cur_head * stride_logic_h
            + (cur_batch_start_loc + start_n + offs_n),
            mask=start_n + offs_n < cur_batch_seq_len,
            other=float("-inf"),
        )

        n_e_max = tl.maximum(tl.max(qk, 0), e_max)
        old_scale = tl.exp(e_max - n_e_max)
        p = tl.exp(qk - n_e_max)
        e_sum = e_sum * old_scale + tl.sum(p, 0)
        v = tl.load(
            v_ptrs + v_index[:, None] * stride_buf_vbs, mask=(offs_d[None, :] < Lv)
        )
        acc = acc * old_scale + tl.sum(p[:, None] * v, 0)
        e_max = n_e_max

    acc = acc / e_sum
    off_o = cur_batch * stride_obs + cur_head * stride_oh + offs_d
    out_ptrs = Out + off_o
    tl.store(out_ptrs, acc, mask=(offs_d < Lv))


def _decode_att_m_fwd(
    q,
    k_buffer,
    att_out,
    Req_to_tokens,
    B_req_idx,
    B_Start_Loc,
    B_Seqlen,
    max_len_in_batch,
    sm_scale,
    logit_cap,
):
    BLOCK = 32
    Lk = k_buffer.shape[-1]

    batch, head_num = B_req_idx.shape[0], q.shape[1]

    grid = (batch, head_num, triton.cdiv(max_len_in_batch, BLOCK))
    kv_group_num = q.shape[1] // k_buffer.shape[1]

    if kv_group_num == 1:
        num_warps = 4
    else:
        num_warps = 2

    BLOCK_DMODEL = triton.next_power_of_2(Lk)

    _fwd_kernel_stage1[grid](
        q,
        k_buffer,
        sm_scale,
        Req_to_tokens,
        B_req_idx,
        B_Start_Loc,
        B_Seqlen,
        att_out,
        Req_to_tokens.stride(0),
        q.stride(0),
        q.stride(1),
        k_buffer.stride(0),
        k_buffer.stride(1),
        att_out.stride(0),
        kv_group_num=kv_group_num,
        BLOCK_DMODEL=BLOCK_DMODEL,
        BLOCK_N=BLOCK,
        logit_cap=logit_cap,
        num_warps=num_warps,
        num_stages=1,
        Lk=Lk,
    )


def _decode_softmax_reducev_fwd(
    logits,
    v_buffer,
    o,
    req_to_tokens,
    b_req_idx,
    b_start_loc,
    b_seq_len,
):
    BLOCK = 64
    batch, head = b_seq_len.shape[0], logits.shape[0]
    grid = (batch, head, 1)
    kv_group_num = logits.shape[0] // v_buffer.shape[1]

    num_warps = 1

    Lv = v_buffer.shape[-1]
    BLOCK_DMODEL = triton.next_power_of_2(Lv)

    _fwd_kernel_stage2[grid](
        logits,
        v_buffer,
        o,
        req_to_tokens,
        b_req_idx,
        b_start_loc,
        b_seq_len,
        logits.stride(0),
        v_buffer.stride(0),
        v_buffer.stride(1),
        o.stride(0),
        o.stride(1),
        req_to_tokens.stride(0),
        kv_group_num=kv_group_num,
        BLOCK_DMODEL=BLOCK_DMODEL,
        BLOCK_N=BLOCK,
        num_warps=num_warps,
        num_stages=3,
        Lv=Lv,
    )


@triton.jit
def _fwd_grouped_kernel_stage1(
    Q,
    K_Buffer,
    sm_scale,
    Req_to_tokens,
    B_req_idx,
    B_Start_Loc,
    B_Seqlen,
    Att_Out,
    stride_req_to_tokens_b,
    stride_qbs,
    stride_qh,
    stride_buf_kbs,
    stride_buf_kh,
    att_stride_h,
    kv_group_num: tl.constexpr,
    q_head_num: tl.constexpr,
    BLOCK_DMODEL: tl.constexpr,
    BLOCK_DPE: tl.constexpr,
    BLOCK_N: tl.constexpr,
    BLOCK_H: tl.constexpr,
    logit_cap: tl.constexpr,
    Lk: tl.constexpr,
):
    cur_batch = tl.program_id(0)
    cur_head_id = tl.program_id(1)
    cur_kv_head = cur_head_id // tl.cdiv(kv_group_num, BLOCK_H)
    start_n = tl.program_id(2)

    reduce_dtype = Att_Out.dtype.element_ty

    if BLOCK_H < kv_group_num:
        VALID_BLOCK_H: tl.constexpr = BLOCK_H
    else:
        VALID_BLOCK_H: tl.constexpr = kv_group_num
    cur_head = cur_head_id * VALID_BLOCK_H + tl.arange(0, BLOCK_H)
    mask_h = cur_head < (cur_head_id + 1) * VALID_BLOCK_H
    mask_h = mask_h & (cur_head < q_head_num)

    offs_d = tl.arange(0, BLOCK_DMODEL)
    cur_batch_seq_len = tl.load(B_Seqlen + cur_batch)
    cur_batch_in_all_start_index = tl.load(B_Start_Loc + cur_batch)
    cur_batch_req_idx = tl.load(B_req_idx + cur_batch)

    cur_batch_start_index = 0
    cur_batch_end_index = cur_batch_seq_len

    offs_q = cur_batch * stride_qbs + cur_head[:, None] * stride_qh + offs_d[None, :]

    if BLOCK_DPE > 0:
        offs_dpe = BLOCK_DMODEL + tl.arange(0, BLOCK_DPE)
        off_qpe = (
            cur_batch * stride_qbs + cur_head[:, None] * stride_qh + offs_dpe[None, :]
        )

    offs_n = start_n * BLOCK_N + tl.arange(0, BLOCK_N)

    block_stard_index = start_n * BLOCK_N
    block_mask = tl.where(block_stard_index < cur_batch_seq_len, 1, 0)

    for start_mark in range(0, block_mask, 1):
        q = tl.load(
            Q + offs_q + start_mark, mask=(mask_h[:, None]) & (offs_d[None, :] < Lk)
        ).to(reduce_dtype)
        offs_n_new = cur_batch_start_index + offs_n
        k_loc = tl.load(
            Req_to_tokens + stride_req_to_tokens_b * cur_batch_req_idx + offs_n_new,
            mask=offs_n_new < cur_batch_end_index,
            other=0,
        )
        offs_buf_k = (
            k_loc[None, :] * stride_buf_kbs
            + cur_kv_head * stride_buf_kh
            + offs_d[:, None]
        )
        k = tl.load(
            K_Buffer + offs_buf_k,
            mask=(offs_n_new[None, :] < cur_batch_end_index) & (offs_d[:, None] < Lk),
            other=0.0,
        ).to(reduce_dtype)
        qk = tl.dot(q, k)
        if BLOCK_DPE > 0:
            qpe = tl.load(Q + off_qpe + start_mark, mask=mask_h[:, None]).to(
                reduce_dtype
            )
            offs_buf_kpe = (
                k_loc[None, :] * stride_buf_kbs
                + cur_kv_head * stride_buf_kh
                + offs_dpe[:, None]
            )
            kpe = tl.load(
                K_Buffer + offs_buf_kpe,
                mask=offs_n_new[None, :] < cur_batch_end_index,
                other=0.0,
            ).to(reduce_dtype)
            qk += tl.dot(qpe, kpe)
        qk *= sm_scale

        if logit_cap > 0:
            qk = logit_cap * tanh(qk / logit_cap)

        offs_o = cur_head[:, None] * att_stride_h + (
            cur_batch_in_all_start_index + offs_n[None, :]
        )

        tl.store(
            Att_Out + offs_o,
            qk,
            mask=mask_h[:, None] & (offs_n_new[None, :] < cur_batch_end_index),
        )


@triton.jit
def _fwd_grouped_kernel_stage2(
    logits,
    V_Buffer,
    Out,
    Req_to_tokens,
    B_req_idx,
    B_Start_Loc,
    B_Seqlen,
    stride_logic_h,
    stride_buf_vbs,
    stride_buf_vh,
    stride_obs,
    stride_oh,
    stride_req_to_token_b,
    kv_group_num: tl.constexpr,
    q_head_num: tl.constexpr,
    BLOCK_DMODEL: tl.constexpr,
    BLOCK_N: tl.constexpr,
    BLOCK_H: tl.constexpr,
    Lv: tl.constexpr,
):
    cur_batch = tl.program_id(0)
    cur_head_id = tl.program_id(1)
    cur_kv_head = cur_head_id // tl.cdiv(kv_group_num, BLOCK_H)

    if BLOCK_H < kv_group_num:
        VALID_BLOCK_H: tl.constexpr = BLOCK_H
    else:
        VALID_BLOCK_H: tl.constexpr = kv_group_num
    cur_head = cur_head_id * VALID_BLOCK_H + tl.arange(0, BLOCK_H)
    mask_h = cur_head < (cur_head_id + 1) * VALID_BLOCK_H
    mask_h = mask_h & (cur_head < q_head_num)

    cur_batch_seq_len = tl.load(B_Seqlen + cur_batch)
    cur_batch_start_loc = tl.load(B_Start_Loc + cur_batch)
    cur_batch_req_idx = tl.load(B_req_idx + cur_batch)

    offs_n = tl.arange(0, BLOCK_N)
    offs_d = tl.arange(0, BLOCK_DMODEL)

    offs_buf_v = cur_kv_head * stride_buf_vh + offs_d[None, :]
    v_ptrs = V_Buffer + offs_buf_v

    e_max = tl.zeros([BLOCK_H], dtype=tl.float32) - float("inf")
    e_sum = tl.zeros([BLOCK_H], dtype=tl.float32)
    acc = tl.zeros([BLOCK_H, BLOCK_DMODEL], dtype=tl.float32)

    for start_n in range(0, cur_batch_seq_len, BLOCK_N):
        start_n = tl.multiple_of(start_n, BLOCK_N)
        v_index = tl.load(
            Req_to_tokens
            + cur_batch_req_idx * stride_req_to_token_b
            + (start_n + offs_n),
            mask=(start_n + offs_n) < cur_batch_seq_len,
            other=0,
        )

        offs_qk = cur_head[:, None] * stride_logic_h + (
            cur_batch_start_loc + start_n + offs_n[None, :]
        )

        qk = tl.load(
            logits + offs_qk,
            mask=mask_h[:, None] & (start_n + offs_n[None, :] < cur_batch_seq_len),
            other=float("-inf"),
        )

        n_e_max = tl.maximum(tl.max(qk, 1), e_max)
        old_scale = tl.exp(e_max - n_e_max)
        p = tl.exp(qk - n_e_max[:, None])
        e_sum = e_sum * old_scale + tl.sum(p, 1)
        v = tl.load(
            v_ptrs + v_index[:, None] * stride_buf_vbs, mask=(offs_d[None, :] < Lv)
        )
        p = p.to(v.dtype)
        acc = acc * old_scale[:, None] + tl.dot(p, v)
        e_max = n_e_max

    acc = acc / e_sum[:, None]
    off_o = cur_batch * stride_obs + cur_head[:, None] * stride_oh + offs_d[None, :]
    out_ptrs = Out + off_o
    tl.store(out_ptrs, acc, mask=(mask_h[:, None]) & (offs_d[None, :] < Lv))


def _decode_grouped_att_m_fwd(
    q,
    k_buffer,
    att_out,
    Req_to_tokens,
    B_req_idx,
    B_Start_Loc,
    B_Seqlen,
    max_len_in_batch,
    sm_scale,
    logit_cap,
):
    BLOCK = 64
    Lk = k_buffer.shape[-1]

    if Lk == 576:
        BLOCK_DMODEL = 512
        BLOCK_DPE = 64
    elif Lk == 288:
        BLOCK_DMODEL = 256
        BLOCK_DPE = 32
    else:
        BLOCK_DMODEL = triton.next_power_of_2(Lk)
        BLOCK_DPE = 0

    batch, head_num = B_req_idx.shape[0], q.shape[1]
    kv_group_num = q.shape[1] // k_buffer.shape[1]

    BLOCK_H = max(16, min(64, triton.next_power_of_2(kv_group_num)))
    grid = (
        batch,
        triton.cdiv(head_num, min(BLOCK_H, kv_group_num)),
        triton.cdiv(max_len_in_batch, BLOCK),
    )

    num_warps = 4

    extra_kargs = {}
    if is_hip():
        # https://rocm.docs.amd.com/en/docs-6.2.0/how-to/llm-fine-tuning-optimization/optimizing-triton-kernel.html
        # https://github.com/triton-lang/triton/blob/main/third_party/amd/backend/compiler.py
        extra_kargs = {"waves_per_eu": 4, "matrix_instr_nonkdim": 16, "kpack": 2}

    _fwd_grouped_kernel_stage1[grid](
        q,
        k_buffer,
        sm_scale,
        Req_to_tokens,
        B_req_idx,
        B_Start_Loc,
        B_Seqlen,
        att_out,
        Req_to_tokens.stride(0),
        q.stride(0),
        q.stride(1),
        k_buffer.stride(0),
        k_buffer.stride(1),
        att_out.stride(0),
        kv_group_num=kv_group_num,
        q_head_num=head_num,
        BLOCK_DMODEL=BLOCK_DMODEL,
        BLOCK_DPE=BLOCK_DPE,
        BLOCK_N=BLOCK,
        BLOCK_H=BLOCK_H,
        logit_cap=logit_cap,
        num_warps=num_warps,
        num_stages=1,
        Lk=Lk,
        **extra_kargs,
    )


def _decode_grouped_softmax_reducev_fwd(
    logits,
    v_buffer,
    o,
    req_to_tokens,
    b_req_idx,
    b_start_loc,
    b_seq_len,
):
    BLOCK = 128
    batch, head_num = b_seq_len.shape[0], logits.shape[0]
    kv_group_num = logits.shape[0] // v_buffer.shape[1]
    BLOCK_H = max(16, min(64, triton.next_power_of_2(kv_group_num)))
    grid = (batch, triton.cdiv(head_num, min(BLOCK_H, kv_group_num)), 1)

    num_warps = 8

    Lv = v_buffer.shape[-1]
    BLOCK_DMODEL = triton.next_power_of_2(Lv)

    extra_kargs = {}
    if is_hip():
        # https://rocm.docs.amd.com/en/docs-6.2.0/how-to/llm-fine-tuning-optimization/optimizing-triton-kernel.html
        # https://github.com/triton-lang/triton/blob/main/third_party/amd/backend/compiler.py
        extra_kargs = {"waves_per_eu": 4, "matrix_instr_nonkdim": 16, "kpack": 2}

    _fwd_grouped_kernel_stage2[grid](
        logits,
        v_buffer,
        o,
        req_to_tokens,
        b_req_idx,
        b_start_loc,
        b_seq_len,
        logits.stride(0),
        v_buffer.stride(0),
        v_buffer.stride(1),
        o.stride(0),
        o.stride(1),
        req_to_tokens.stride(0),
        kv_group_num=kv_group_num,
        q_head_num=head_num,
        BLOCK_DMODEL=BLOCK_DMODEL,
        BLOCK_N=BLOCK,
        BLOCK_H=BLOCK_H,
        Lv=Lv,
        num_warps=num_warps,
        num_stages=1,
        **extra_kargs,
    )


def decode_attention_fwd_normal(
    q,
    k_buffer,
    v_buffer,
    o,
    req_to_token,
    b_req_idx,
    b_start_loc,
    b_seq_len,
    attn_logits,
    max_len_in_batch,
    sm_scale,
    logit_cap=0.0,
):
    _decode_att_m_fwd(
        q,
        k_buffer,
        attn_logits,
        req_to_token,
        b_req_idx,
        b_start_loc,
        b_seq_len,
        max_len_in_batch,
        sm_scale,
        logit_cap,
    )
    _decode_softmax_reducev_fwd(
        attn_logits,
        v_buffer,
        o,
        req_to_token,
        b_req_idx,
        b_start_loc,
        b_seq_len,
    )


def decode_attention_fwd_grouped(
    q,
    k_buffer,
    v_buffer,
    o,
    req_to_token,
    b_req_idx,
    b_start_loc,
    b_seq_len,
    attn_logits,
    max_len_in_batch,
    sm_scale,
    logit_cap=0.0,
):
    _decode_grouped_att_m_fwd(
        q,
        k_buffer,
        attn_logits,
        req_to_token,
        b_req_idx,
        b_start_loc,
        b_seq_len,
        max_len_in_batch,
        sm_scale,
        logit_cap,
    )
    _decode_grouped_softmax_reducev_fwd(
        attn_logits,
        v_buffer,
        o,
        req_to_token,
        b_req_idx,
        b_start_loc,
        b_seq_len,
    )


def decode_attention_fwd(
    q,
    k_buffer,
    v_buffer,
    o,
    req_to_token,
    b_req_idx,
    b_start_loc,
    b_seq_len,
    attn_logits,
    max_len_in_batch,
    sm_scale,
    logit_cap=0.0,
):
    kv_group_num = q.shape[1] // v_buffer.shape[1]

    if kv_group_num == 1:
        # MHA
        decode_attention_fwd_normal(
            q,
            k_buffer,
            v_buffer,
            o,
            req_to_token,
            b_req_idx,
            b_start_loc,
            b_seq_len,
            attn_logits,
            max_len_in_batch,
            sm_scale,
            logit_cap,
        )
    else:
        # GQA/MQA/MLA
        decode_attention_fwd_grouped(
            q,
            k_buffer,
            v_buffer,
            o,
            req_to_token,
            b_req_idx,
            b_start_loc,
            b_seq_len,
            attn_logits,
            max_len_in_batch,
            sm_scale,
            logit_cap,
        )
