Delete flash_attn_triton.py

flash_attn_triton.py

@@ -1,1172 +0,0 @@
-# Copyright (c) 2022, Tri Dao.
-#
-# 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.
-"""
-*Experimental* implementation of FlashAttention in Triton.
-Tested with triton==2.0.0.dev20221202.
-Triton 2.0 has a new backend (MLIR) but seems like it doesn't yet work for head dimensions
-other than 64:
-https://github.com/openai/triton/blob/d376020f90002757eea3ea9475d4f7cfc2ec5ead/python/triton/ops/flash_attention.py#L207
-We'll update this implementation with the new Triton backend once this is fixed.
-
-We use the FlashAttention implementation from Phil Tillet a starting point.
-https://github.com/openai/triton/blob/master/python/tutorials/06-fused-attention.py
-
-Changes:
-- Implement both causal and non-causal attention.
-- Implement both self-attention and cross-attention.
-- Support arbitrary seqlens (not just multiples of 128), for both forward and backward.
-- Support all head dimensions up to 128 (not just 16, 32, 64, 128), for both forward and backward.
-- Support attention bias.
-- Speed up the forward pass a bit, and only store the LSE instead of m and l.
-- Make the backward for d=128 much faster by reducing register spilling.
-- Optionally parallelize the backward pass across seqlen_k, to deal with the case of
-small batch size * nheads.
-
-Caution:
-- This is an *experimental* implementation. The forward pass should be quite robust but
-I'm not 100% sure that the backward pass doesn't have race conditions (due to the Triton compiler).
-- This implementation has only been tested on A100.
-- If you plan to use headdim other than 64 and 128, you should test for race conditions
-(due to the Triton compiler), as done in tests/test_flash_attn.py
-"test_flash_attn_triton_race_condition". I've tested and fixed many race conditions
-for different head dimensions (40, 48, 64, 128, 80, 88, 96), but I'm still not 100% confident
-that there are none left for other head dimensions.
-
-Differences between this Triton version and the CUDA version:
-- Triton version doesn't support dropout.
-- Triton forward is generally faster than CUDA forward, while Triton backward is
-generally slower than CUDA backward. Overall Triton forward + backward is slightly slower
-than CUDA forward + backward.
-- Triton version doesn't support different sequence lengths in a batch (i.e., RaggedTensor/NestedTensor).
-- Triton version supports attention bias, while CUDA version doesn't.
-"""
-
-import math
-
-import torch
-import triton
-import triton.language as tl
-
-
-# Disabling autotune for now, set num_warps=4 if headdim=64 and num_warps=8 if headdim=128
-# @triton.autotune(
-#     configs=[
-#         triton.Config({"BLOCK_M": 128, "BLOCK_N": 128}, num_warps=4, num_stages=1),
-#         # This config has a race condition when EVEN_M == False, disabling it for now.
-#         # triton.Config({"BLOCK_M": 64, "BLOCK_N": 64}, num_warps=4, num_stages=1),
-#     ],
-#     key=['CACHE_KEY_SEQLEN_Q', 'CACHE_KEY_SEQLEN_K', 'BIAS_TYPE', 'IS_CAUSAL', 'BLOCK_HEADDIM']
-# )
-@triton.heuristics(
-    {
-        "EVEN_M": lambda args: args["seqlen_q"] % args["BLOCK_M"] == 0,
-        "EVEN_N": lambda args: args["seqlen_k"] % args["BLOCK_N"] == 0,
-        "EVEN_HEADDIM": lambda args: args["headdim"] == args["BLOCK_HEADDIM"],
-    }
-)
-@triton.jit
-def _fwd_kernel(
-    Q,
-    K,
-    V,
-    Bias,
-    Out,
-    Lse,
-    TMP,  # NOTE: TMP is a scratchpad buffer to workaround a compiler bug
-    softmax_scale,
-    stride_qb,
-    stride_qh,
-    stride_qm,
-    stride_kb,
-    stride_kh,
-    stride_kn,
-    stride_vb,
-    stride_vh,
-    stride_vn,
-    stride_bb,
-    stride_bh,
-    stride_bm,
-    stride_ob,
-    stride_oh,
-    stride_om,
-    nheads,
-    seqlen_q,
-    seqlen_k,
-    seqlen_q_rounded,
-    headdim,
-    CACHE_KEY_SEQLEN_Q,
-    CACHE_KEY_SEQLEN_K,
-    BIAS_TYPE: tl.constexpr,
-    IS_CAUSAL: tl.constexpr,
-    BLOCK_HEADDIM: tl.constexpr,
-    EVEN_M: tl.constexpr,
-    EVEN_N: tl.constexpr,
-    EVEN_HEADDIM: tl.constexpr,
-    BLOCK_M: tl.constexpr,
-    BLOCK_N: tl.constexpr,
-):
-    start_m = tl.program_id(0)
-    off_hb = tl.program_id(1)
-    off_b = off_hb // nheads
-    off_h = off_hb % nheads
-    # off_b = tl.program_id(1)
-    # off_h = tl.program_id(2)
-    # off_hb = off_b * nheads + off_h
-    # initialize offsets
-    offs_m = start_m * BLOCK_M + tl.arange(0, BLOCK_M)
-    offs_n = tl.arange(0, BLOCK_N)
-    offs_d = tl.arange(0, BLOCK_HEADDIM)
-    # Initialize pointers to Q, K, V
-    # Adding parenthesis around indexing might use int32 math instead of int64 math?
-    # https://github.com/openai/triton/issues/741
-    # I'm seeing a tiny bit of difference (5-7us)
-    q_ptrs = (
-        Q + off_b * stride_qb + off_h * stride_qh + (offs_m[:, None] * stride_qm + offs_d[None, :])
-    )
-    k_ptrs = (
-        K + off_b * stride_kb + off_h * stride_kh + (offs_n[:, None] * stride_kn + offs_d[None, :])
-    )
-    v_ptrs = (
-        V + off_b * stride_vb + off_h * stride_vh + (offs_n[:, None] * stride_vn + offs_d[None, :])
-    )
-    if BIAS_TYPE == "vector":
-        b_ptrs = Bias + off_b * stride_bb + off_h * stride_bh + offs_n
-    elif BIAS_TYPE == "matrix":
-        b_ptrs = (
-            Bias
-            + off_b * stride_bb
-            + off_h * stride_bh
-            + (offs_m[:, None] * stride_bm + offs_n[None, :])
-        )
-    # initialize pointer to m and l
-    t_ptrs = TMP + off_hb * seqlen_q_rounded + offs_m
-    lse_i = tl.zeros([BLOCK_M], dtype=tl.float32) - float("inf")
-    m_i = tl.zeros([BLOCK_M], dtype=tl.float32) - float("inf")
-    acc_o = tl.zeros([BLOCK_M, BLOCK_HEADDIM], dtype=tl.float32)
-    # load q: it will stay in SRAM throughout
-    # [2022-10-30] TD: Triton bug - in the case of EVEN_M=True and EVEN_N=False, if we just call
-    # tl.load(q_ptrs), we get the wrong output!
-    if EVEN_M & EVEN_N:
-        if EVEN_HEADDIM:
-            q = tl.load(q_ptrs)
-        else:
-            q = tl.load(q_ptrs, mask=offs_d[None, :] < headdim, other=0.0)
-    else:
-        if EVEN_HEADDIM:
-            q = tl.load(q_ptrs, mask=offs_m[:, None] < seqlen_q, other=0.0)
-        else:
-            q = tl.load(
-                q_ptrs, mask=(offs_m[:, None] < seqlen_q) & (offs_d[None, :] < headdim), other=0.0
-            )
-    # loop over k, v and update accumulator
-    end_n = seqlen_k if not IS_CAUSAL else tl.minimum((start_m + 1) * BLOCK_M, seqlen_k)
-    for start_n in range(0, end_n, BLOCK_N):
-        start_n = tl.multiple_of(start_n, BLOCK_N)
-        # -- compute qk ----
-        if EVEN_N & EVEN_M:  # If we just do "if EVEN_N", there seems to be some race condition
-            if EVEN_HEADDIM:
-                k = tl.load(k_ptrs + start_n * stride_kn)
-            else:
-                k = tl.load(k_ptrs + start_n * stride_kn, mask=offs_d[None, :] < headdim, other=0.0)
-        else:
-            if EVEN_HEADDIM:
-                k = tl.load(
-                    k_ptrs + start_n * stride_kn,
-                    mask=(start_n + offs_n)[:, None] < seqlen_k,
-                    other=0.0,
-                )
-            else:
-                k = tl.load(
-                    k_ptrs + start_n * stride_kn,
-                    mask=((start_n + offs_n)[:, None] < seqlen_k) & (offs_d[None, :] < headdim),
-                    other=0.0,
-                )
-        qk = tl.zeros([BLOCK_M, BLOCK_N], dtype=tl.float32)
-        qk += tl.dot(q, k, trans_b=True)
-        # Trying to combine the two masks seem to make the result wrong
-        if not EVEN_N:  # Need to mask out otherwise the softmax is wrong
-            qk += tl.where((start_n + offs_n)[None, :] < seqlen_k, 0, float("-inf"))
-        if IS_CAUSAL:
-            qk += tl.where(offs_m[:, None] >= (start_n + offs_n)[None, :], 0, float("-inf"))
-        if BIAS_TYPE != "none":
-            if BIAS_TYPE == "vector":
-                if EVEN_N:
-                    bias = tl.load(b_ptrs + start_n).to(tl.float32)
-                else:
-                    bias = tl.load(
-                        b_ptrs + start_n, mask=(start_n + offs_n) < seqlen_k, other=0.0
-                    ).to(tl.float32)
-                bias = bias[None, :]
-            elif BIAS_TYPE == "matrix":
-                if EVEN_M & EVEN_N:
-                    bias = tl.load(b_ptrs + start_n).to(tl.float32)
-                else:
-                    bias = tl.load(
-                        b_ptrs + start_n,
-                        mask=(offs_m[:, None] < seqlen_q)
-                        & ((start_n + offs_n)[None, :] < seqlen_k),
-                        other=0.0,
-                    ).to(tl.float32)
-            # Slightly faster to multiply the softmax_scale in the tl.exp below since the compiler
-            # can then fuse the mult and add into an fma instruction. But if we have bias we need to
-            # to multiply with softmax_scale here.
-            qk = qk * softmax_scale + bias
-            m_ij = tl.maximum(tl.max(qk, 1), lse_i)
-            p = tl.exp(qk - m_ij[:, None])
-        else:
-            m_ij = tl.maximum(tl.max(qk, 1) * softmax_scale, lse_i)
-            p = tl.exp(qk * softmax_scale - m_ij[:, None])
-        l_ij = tl.sum(p, 1)
-
-        # scale acc_o
-        acc_o_scale = tl.exp(m_i - m_ij)
-
-        # # -- update output accumulator --
-        # BUG: have to store and immediately load
-        tl.store(t_ptrs, acc_o_scale)
-        acc_o_scale = tl.load(t_ptrs)
-        acc_o = acc_o * acc_o_scale[:, None]
-        # update acc_o
-        if EVEN_N & EVEN_M:  # If we just do "if EVEN_N", there seems to be some race condition
-            if EVEN_HEADDIM:
-                v = tl.load(v_ptrs + start_n * stride_vn)
-            else:
-                v = tl.load(v_ptrs + start_n * stride_vn, mask=offs_d[None, :] < headdim, other=0.0)
-        else:
-            if EVEN_HEADDIM:
-                v = tl.load(
-                    v_ptrs + start_n * stride_vn,
-                    mask=(start_n + offs_n)[:, None] < seqlen_k,
-                    other=0.0,
-                )
-            else:
-                v = tl.load(
-                    v_ptrs + start_n * stride_vn,
-                    mask=((start_n + offs_n)[:, None] < seqlen_k) & (offs_d[None, :] < headdim),
-                    other=0.0,
-                )
-        p = p.to(v.dtype)
-        acc_o += tl.dot(p, v)
-
-        # -- update statistics
-        m_i = m_ij
-        l_i_new = tl.exp(lse_i - m_ij) + l_ij
-        lse_i = m_ij + tl.log(l_i_new)
-
-    o_scale = tl.exp(m_i - lse_i)
-    # BUG: have to store and immediately load
-    tl.store(t_ptrs, o_scale)
-    o_scale = tl.load(t_ptrs)
-    acc_o = acc_o * o_scale[:, None]
-    # rematerialize offsets to save registers
-    start_m = tl.program_id(0)
-    offs_m = start_m * BLOCK_M + tl.arange(0, BLOCK_M)
-    # write back l and m
-    lse_ptrs = Lse + off_hb * seqlen_q_rounded + offs_m
-    tl.store(lse_ptrs, lse_i)
-    # initialize pointers to output
-    offs_d = tl.arange(0, BLOCK_HEADDIM)
-    out_ptrs = (
-        Out
-        + off_b * stride_ob
-        + off_h * stride_oh
-        + (offs_m[:, None] * stride_om + offs_d[None, :])
-    )
-    if EVEN_M:
-        if EVEN_HEADDIM:
-            tl.store(out_ptrs, acc_o)
-        else:
-            tl.store(out_ptrs, acc_o, mask=offs_d[None, :] < headdim)
-    else:
-        if EVEN_HEADDIM:
-            tl.store(out_ptrs, acc_o, mask=offs_m[:, None] < seqlen_q)
-        else:
-            tl.store(
-                out_ptrs, acc_o, mask=(offs_m[:, None] < seqlen_q) & (offs_d[None, :] < headdim)
-            )
-
-
-@triton.jit
-def _bwd_preprocess_do_o_dot(
-    Out,
-    DO,
-    Delta,
-    stride_ob,
-    stride_oh,
-    stride_om,
-    stride_dob,
-    stride_doh,
-    stride_dom,
-    nheads,
-    seqlen_q,
-    seqlen_q_rounded,
-    headdim,
-    BLOCK_M: tl.constexpr,
-    BLOCK_HEADDIM: tl.constexpr,
-):
-    start_m = tl.program_id(0)
-    off_hb = tl.program_id(1)
-    off_b = off_hb // nheads
-    off_h = off_hb % nheads
-    # initialize offsets
-    offs_m = start_m * BLOCK_M + tl.arange(0, BLOCK_M)
-    offs_d = tl.arange(0, BLOCK_HEADDIM)
-    # load
-    o = tl.load(
-        Out + off_b * stride_ob + off_h * stride_oh + offs_m[:, None] * stride_om + offs_d[None, :],
-        mask=(offs_m[:, None] < seqlen_q) & (offs_d[None, :] < headdim),
-        other=0.0,
-    ).to(tl.float32)
-    do = tl.load(
-        DO
-        + off_b * stride_dob
-        + off_h * stride_doh
-        + offs_m[:, None] * stride_dom
-        + offs_d[None, :],
-        mask=(offs_m[:, None] < seqlen_q) & (offs_d[None, :] < headdim),
-        other=0.0,
-    ).to(tl.float32)
-    delta = tl.sum(o * do, axis=1)
-    # write-back
-    tl.store(Delta + off_hb * seqlen_q_rounded + offs_m, delta)
-
-
-@triton.jit
-def _bwd_store_dk_dv(
-    dk_ptrs,
-    dv_ptrs,
-    dk,
-    dv,
-    offs_n,
-    offs_d,
-    seqlen_k,
-    headdim,
-    EVEN_M: tl.constexpr,
-    EVEN_N: tl.constexpr,
-    EVEN_HEADDIM: tl.constexpr,
-):
-    # [2022-11-01] TD: Same bug. In the case of EVEN_N=True and EVEN_M=False,
-    # if we just call tl.store(dv_ptrs), there's a race condition
-    if EVEN_N & EVEN_M:
-        if EVEN_HEADDIM:
-            tl.store(dv_ptrs, dv)
-            tl.store(dk_ptrs, dk)
-        else:
-            tl.store(dv_ptrs, dv, mask=offs_d[None, :] < headdim)
-            tl.store(dk_ptrs, dk, mask=offs_d[None, :] < headdim)
-    else:
-        if EVEN_HEADDIM:
-            tl.store(dv_ptrs, dv, mask=offs_n[:, None] < seqlen_k)
-            tl.store(dk_ptrs, dk, mask=offs_n[:, None] < seqlen_k)
-        else:
-            tl.store(dv_ptrs, dv, mask=(offs_n[:, None] < seqlen_k) & (offs_d[None, :] < headdim))
-            tl.store(dk_ptrs, dk, mask=(offs_n[:, None] < seqlen_k) & (offs_d[None, :] < headdim))
-
-
-@triton.jit
-def _bwd_kernel_one_col_block(
-    start_n,
-    Q,
-    K,
-    V,
-    Bias,
-    DO,
-    DQ,
-    DK,
-    DV,
-    LSE,
-    D,
-    softmax_scale,
-    stride_qm,
-    stride_kn,
-    stride_vn,
-    stride_bm,
-    stride_dom,
-    stride_dqm,
-    stride_dkn,
-    stride_dvn,
-    seqlen_q,
-    seqlen_k,
-    headdim,
-    ATOMIC_ADD: tl.constexpr,
-    BIAS_TYPE: tl.constexpr,
-    IS_CAUSAL: tl.constexpr,
-    BLOCK_HEADDIM: tl.constexpr,
-    EVEN_M: tl.constexpr,
-    EVEN_N: tl.constexpr,
-    EVEN_HEADDIM: tl.constexpr,
-    BLOCK_M: tl.constexpr,
-    BLOCK_N: tl.constexpr,
-):
-    # We need to make sure begin_m is a multiple of BLOCK_M (not BLOCK_N)
-    begin_m = 0 if not IS_CAUSAL else ((start_n * BLOCK_N) // BLOCK_M) * BLOCK_M
-    # initialize row/col offsets
-    offs_qm = begin_m + tl.arange(0, BLOCK_M)
-    offs_n = start_n * BLOCK_N + tl.arange(0, BLOCK_N)
-    offs_m = tl.arange(0, BLOCK_M)
-    offs_d = tl.arange(0, BLOCK_HEADDIM)
-    # initialize pointers to value-like data
-    q_ptrs = Q + (offs_qm[:, None] * stride_qm + offs_d[None, :])
-    k_ptrs = K + (offs_n[:, None] * stride_kn + offs_d[None, :])
-    v_ptrs = V + (offs_n[:, None] * stride_vn + offs_d[None, :])
-    do_ptrs = DO + (offs_qm[:, None] * stride_dom + offs_d[None, :])
-    dq_ptrs = DQ + (offs_qm[:, None] * stride_dqm + offs_d[None, :])
-    if BIAS_TYPE == "vector":
-        b_ptrs = Bias + offs_n
-    elif BIAS_TYPE == "matrix":
-        b_ptrs = Bias + (offs_qm[:, None] * stride_bm + offs_n[None, :])
-    # initialize dv and dk
-    dv = tl.zeros([BLOCK_N, BLOCK_HEADDIM], dtype=tl.float32)
-    dk = tl.zeros([BLOCK_N, BLOCK_HEADDIM], dtype=tl.float32)
-    # There seems to be some problem with Triton pipelining that makes results wrong for
-    # headdim=64, seqlen=(113, 255), bias_type='matrix'. In this case the for loop
-    # may have zero step, and pipelining with the bias matrix could screw it up.
-    # So we just exit early.
-    if begin_m >= seqlen_q:
-        dv_ptrs = DV + (offs_n[:, None] * stride_dvn + offs_d[None, :])
-        dk_ptrs = DK + (offs_n[:, None] * stride_dkn + offs_d[None, :])
-        _bwd_store_dk_dv(
-            dk_ptrs,
-            dv_ptrs,
-            dk,
-            dv,
-            offs_n,
-            offs_d,
-            seqlen_k,
-            headdim,
-            EVEN_M=EVEN_M,
-            EVEN_N=EVEN_N,
-            EVEN_HEADDIM=EVEN_HEADDIM,
-        )
-        return
-    # k and v stay in SRAM throughout
-    # [2022-10-30] TD: Same bug as the fwd. In the case of EVEN_N=True and EVEN_M=False,
-    # if we just call tl.load(k_ptrs), we get the wrong output!
-    if EVEN_N & EVEN_M:
-        if EVEN_HEADDIM:
-            k = tl.load(k_ptrs)
-            v = tl.load(v_ptrs)
-        else:
-            k = tl.load(k_ptrs, mask=offs_d[None, :] < headdim, other=0.0)
-            v = tl.load(v_ptrs, mask=offs_d[None, :] < headdim, other=0.0)
-    else:
-        if EVEN_HEADDIM:
-            k = tl.load(k_ptrs, mask=offs_n[:, None] < seqlen_k, other=0.0)
-            v = tl.load(v_ptrs, mask=offs_n[:, None] < seqlen_k, other=0.0)
-        else:
-            k = tl.load(
-                k_ptrs, mask=(offs_n[:, None] < seqlen_k) & (offs_d[None, :] < headdim), other=0.0
-            )
-            v = tl.load(
-                v_ptrs, mask=(offs_n[:, None] < seqlen_k) & (offs_d[None, :] < headdim), other=0.0
-            )
-    # loop over rows
-    num_block_m = tl.cdiv(seqlen_q, BLOCK_M)
-    for start_m in range(begin_m, num_block_m * BLOCK_M, BLOCK_M):
-        start_m = tl.multiple_of(start_m, BLOCK_M)
-        offs_m_curr = start_m + offs_m
-        # load q, k, v, do on-chip
-        # Same bug as below. Otherwise gives wrong result for headdim=40, seqlen=(128, 117)
-        if EVEN_M & EVEN_HEADDIM:
-            q = tl.load(q_ptrs)
-        else:
-            if EVEN_HEADDIM:
-                q = tl.load(q_ptrs, mask=offs_m_curr[:, None] < seqlen_q, other=0.0)
-            else:
-                q = tl.load(
-                    q_ptrs,
-                    mask=(offs_m_curr[:, None] < seqlen_q) & (offs_d[None, :] < headdim),
-                    other=0.0,
-                )
-        # recompute p = softmax(qk, dim=-1).T
-        qk = tl.dot(q, k, trans_b=True)
-        # Trying to combine the two masks seem to make the result wrong
-        if not EVEN_N:  # Need to mask out otherwise the softmax is wrong
-            qk = tl.where(offs_n[None, :] < seqlen_k, qk, float("-inf"))
-        if IS_CAUSAL:
-            qk = tl.where(offs_m_curr[:, None] >= (offs_n[None, :]), qk, float("-inf"))
-        if BIAS_TYPE != "none":
-            tl.debug_barrier()  # Race condition otherwise
-            if BIAS_TYPE == "vector":
-                if EVEN_N:
-                    bias = tl.load(b_ptrs).to(tl.float32)
-                else:
-                    bias = tl.load(b_ptrs, mask=offs_n < seqlen_k, other=0.0).to(tl.float32)
-                bias = bias[None, :]
-            elif BIAS_TYPE == "matrix":
-                if EVEN_M & EVEN_N:
-                    bias = tl.load(b_ptrs).to(tl.float32)
-                else:
-                    bias = tl.load(
-                        b_ptrs,
-                        mask=(offs_m_curr[:, None] < seqlen_q) & (offs_n[None, :] < seqlen_k),
-                        other=0.0,
-                    ).to(tl.float32)
-            qk = qk * softmax_scale + bias
-        # There seems to be a race condition when headdim=48/96, and dq, dk, dv are wrong.
-        # Also wrong for headdim=64.
-        if not (EVEN_M & EVEN_HEADDIM):
-            tl.debug_barrier()
-        lse_i = tl.load(LSE + offs_m_curr)
-        if BIAS_TYPE == "none":
-            p = tl.exp(qk * softmax_scale - lse_i[:, None])
-        else:
-            p = tl.exp(qk - lse_i[:, None])
-        # compute dv
-        # [2022-10-30] TD: A Triton bug: if EVEN_M=True and EVEN_HEADDIM=False, if we call
-        # do = tl.load(do_ptrs, mask=offs_d[None, :] < headdim, other=0.0), we get wrong outputs
-        # in the case of headdim=48/96, seqlen_q & seqlen_k >= 512. If headdim=40 or seqlen < 512,
-        # the output is correct.
-        if EVEN_M & EVEN_HEADDIM:
-            do = tl.load(do_ptrs)
-        else:
-            # [2022-11-01] TD: Triton bug, there's a race condition if we just use m_mask and not d_mask.
-            do = tl.load(
-                do_ptrs,
-                mask=(offs_m_curr[:, None] < seqlen_q) & (offs_d[None, :] < headdim),
-                other=0.0,
-            )
-        # if EVEN_M:
-        #     if EVEN_HEADDIM:
-        #         do = tl.load(do_ptrs)
-        #     else:
-        #         do = tl.load(do_ptrs, mask=offs_d[None, :] < headdim, other=0.0)
-        # else:
-        #     if EVEN_HEADDIM:
-        #         do = tl.load(do_ptrs, mask=offs_m_curr[:, None] < seqlen_q, other=0.0)
-        #     else:
-        #         do = tl.load(do_ptrs, mask=(offs_m_curr[:, None] < seqlen_q)
-        #                                    & (offs_d[None, :] < headdim), other=0.0)
-        dv += tl.dot(p.to(do.dtype), do, trans_a=True)
-        # compute dp = dot(v, do)
-        # There seems to be a race condition when headdim=48/96, and dq, dk are wrong.
-        # Also wrong for headdim=128, seqlen=(108, 256), and ATOMIC_ADD=True
-        # Also wrong for headdim=64, seqlen=(1023, 1024), and ATOMIC_ADD=False
-        if not (EVEN_M & EVEN_HEADDIM):
-            tl.debug_barrier()
-        dp = tl.dot(do, v, trans_b=True)
-        # There's a race condition for headdim=48
-        if not EVEN_HEADDIM:
-            tl.debug_barrier()
-        # compute ds = p * (dp - delta[:, None])
-        # Putting the subtraction after the dp matmul (instead of before) is slightly faster
-        Di = tl.load(D + offs_m_curr)
-        # Converting ds to q.dtype here reduces register pressure and makes it much faster
-        # for BLOCK_HEADDIM=128
-        ds = (p * (dp - Di[:, None]) * softmax_scale).to(q.dtype)
-        # compute dk = dot(ds.T, q)
-        dk += tl.dot(ds, q, trans_a=True)
-        # compute dq
-        if not (
-            EVEN_M & EVEN_HEADDIM
-        ):  # Otherewise there's a race condition when BIAS_TYPE='matrix'
-            tl.debug_barrier()
-        if not ATOMIC_ADD:
-            if EVEN_M & EVEN_HEADDIM:  # Race condition if we just do EVEN_M
-                dq = tl.load(dq_ptrs, eviction_policy="evict_last")
-                dq += tl.dot(ds, k)
-                tl.store(dq_ptrs, dq, eviction_policy="evict_last")
-            else:
-                if EVEN_HEADDIM:
-                    dq = tl.load(
-                        dq_ptrs,
-                        mask=offs_m_curr[:, None] < seqlen_q,
-                        other=0.0,
-                        eviction_policy="evict_last",
-                    )
-                    dq += tl.dot(ds, k)
-                    tl.store(
-                        dq_ptrs,
-                        dq,
-                        mask=offs_m_curr[:, None] < seqlen_q,
-                        eviction_policy="evict_last",
-                    )
-                else:
-                    dq = tl.load(
-                        dq_ptrs,
-                        mask=(offs_m_curr[:, None] < seqlen_q) & (offs_d[None, :] < headdim),
-                        other=0.0,
-                        eviction_policy="evict_last",
-                    )
-                    dq += tl.dot(ds, k)
-                    tl.store(
-                        dq_ptrs,
-                        dq,
-                        mask=(offs_m_curr[:, None] < seqlen_q) & (offs_d[None, :] < headdim),
-                        eviction_policy="evict_last",
-                    )
-        else:  # If we're parallelizing across the seqlen_k dimension
-            dq = tl.dot(ds, k)
-            if EVEN_M & EVEN_HEADDIM:  # Race condition if we just do EVEN_M
-                tl.atomic_add(dq_ptrs, dq)
-            else:
-                if EVEN_HEADDIM:
-                    tl.atomic_add(dq_ptrs, dq, mask=offs_m_curr[:, None] < seqlen_q)
-                else:
-                    tl.atomic_add(
-                        dq_ptrs,
-                        dq,
-                        mask=(offs_m_curr[:, None] < seqlen_q) & (offs_d[None, :] < headdim),
-                    )
-        # increment pointers
-        dq_ptrs += BLOCK_M * stride_dqm
-        q_ptrs += BLOCK_M * stride_qm
-        do_ptrs += BLOCK_M * stride_dom
-        if BIAS_TYPE == "matrix":
-            b_ptrs += BLOCK_M * stride_bm
-    # write-back
-    dv_ptrs = DV + (offs_n[:, None] * stride_dvn + offs_d[None, :])
-    dk_ptrs = DK + (offs_n[:, None] * stride_dkn + offs_d[None, :])
-    _bwd_store_dk_dv(
-        dk_ptrs,
-        dv_ptrs,
-        dk,
-        dv,
-        offs_n,
-        offs_d,
-        seqlen_k,
-        headdim,
-        EVEN_M=EVEN_M,
-        EVEN_N=EVEN_N,
-        EVEN_HEADDIM=EVEN_HEADDIM,
-    )
-
-
-def init_to_zero(name):
-    return lambda nargs: nargs[name].zero_()
-
-
-@triton.autotune(
-    configs=[
-        triton.Config(
-            {"BLOCK_M": 128, "BLOCK_N": 128, "SEQUENCE_PARALLEL": False},
-            num_warps=8,
-            num_stages=1,
-            pre_hook=init_to_zero("DQ"),
-        ),
-        triton.Config(
-            {"BLOCK_M": 128, "BLOCK_N": 128, "SEQUENCE_PARALLEL": True},
-            num_warps=8,
-            num_stages=1,
-            pre_hook=init_to_zero("DQ"),
-        ),
-        # Other configs seem to give wrong results when seqlen_q % 128 != 0, disabling them for now
-        # # Kernel is buggy (give wrong result) if we set BLOCK_m=128, BLOCK_n=64, num_warps=*4*
-        # triton.Config({"BLOCK_M": 128, "BLOCK_N": 64, "SEQUENCE_PARALLEL": False}, num_warps=8, num_stages=1, pre_hook=init_to_zero('DQ')),
-        # triton.Config({"BLOCK_M": 128, "BLOCK_N": 64, "SEQUENCE_PARALLEL": True}, num_warps=8, num_stages=1, pre_hook=init_to_zero('DQ')),
-        # triton.Config({"BLOCK_M": 64, "BLOCK_N": 64, "SEQUENCE_PARALLEL": False}, num_warps=4, num_stages=1, pre_hook=init_to_zero('DQ')),
-        # triton.Config({"BLOCK_M": 64, "BLOCK_N": 64, "SEQUENCE_PARALLEL": True}, num_warps=4, num_stages=1, pre_hook=init_to_zero('DQ')),
-    ],
-    key=["CACHE_KEY_SEQLEN_Q", "CACHE_KEY_SEQLEN_K", "BIAS_TYPE", "IS_CAUSAL", "BLOCK_HEADDIM"],
-)
-@triton.heuristics(
-    {
-        "EVEN_M": lambda args: args["seqlen_q"] % args["BLOCK_M"] == 0,
-        "EVEN_N": lambda args: args["seqlen_k"] % args["BLOCK_N"] == 0,
-        "EVEN_HEADDIM": lambda args: args["headdim"] == args["BLOCK_HEADDIM"],
-    }
-)
-@triton.jit
-def _bwd_kernel(
-    Q,
-    K,
-    V,
-    Bias,
-    DO,
-    DQ,
-    DK,
-    DV,
-    LSE,
-    D,
-    softmax_scale,
-    stride_qb,
-    stride_qh,
-    stride_qm,
-    stride_kb,
-    stride_kh,
-    stride_kn,
-    stride_vb,
-    stride_vh,
-    stride_vn,
-    stride_bb,
-    stride_bh,
-    stride_bm,
-    stride_dob,
-    stride_doh,
-    stride_dom,
-    stride_dqb,
-    stride_dqh,
-    stride_dqm,
-    stride_dkb,
-    stride_dkh,
-    stride_dkn,
-    stride_dvb,
-    stride_dvh,
-    stride_dvn,
-    nheads,
-    seqlen_q,
-    seqlen_k,
-    seqlen_q_rounded,
-    headdim,
-    CACHE_KEY_SEQLEN_Q,
-    CACHE_KEY_SEQLEN_K,
-    BIAS_TYPE: tl.constexpr,
-    IS_CAUSAL: tl.constexpr,
-    BLOCK_HEADDIM: tl.constexpr,
-    SEQUENCE_PARALLEL: tl.constexpr,
-    EVEN_M: tl.constexpr,
-    EVEN_N: tl.constexpr,
-    EVEN_HEADDIM: tl.constexpr,
-    BLOCK_M: tl.constexpr,
-    BLOCK_N: tl.constexpr,
-):
-    off_hb = tl.program_id(1)
-    off_b = off_hb // nheads
-    off_h = off_hb % nheads
-    # offset pointers for batch/head
-    Q += off_b * stride_qb + off_h * stride_qh
-    K += off_b * stride_kb + off_h * stride_kh
-    V += off_b * stride_vb + off_h * stride_vh
-    DO += off_b * stride_dob + off_h * stride_doh
-    DQ += off_b * stride_dqb + off_h * stride_dqh
-    DK += off_b * stride_dkb + off_h * stride_dkh
-    DV += off_b * stride_dvb + off_h * stride_dvh
-    if BIAS_TYPE != "none":
-        Bias += off_b * stride_bb + off_h * stride_bh
-    # pointer to row-wise quantities in value-like data
-    D += off_hb * seqlen_q_rounded
-    LSE += off_hb * seqlen_q_rounded
-    if not SEQUENCE_PARALLEL:
-        num_block_n = tl.cdiv(seqlen_k, BLOCK_N)
-        for start_n in range(0, num_block_n):
-            _bwd_kernel_one_col_block(
-                start_n,
-                Q,
-                K,
-                V,
-                Bias,
-                DO,
-                DQ,
-                DK,
-                DV,
-                LSE,
-                D,
-                softmax_scale,
-                stride_qm,
-                stride_kn,
-                stride_vn,
-                stride_bm,
-                stride_dom,
-                stride_dqm,
-                stride_dkn,
-                stride_dvn,
-                seqlen_q,
-                seqlen_k,
-                headdim,
-                ATOMIC_ADD=False,
-                BIAS_TYPE=BIAS_TYPE,
-                IS_CAUSAL=IS_CAUSAL,
-                BLOCK_HEADDIM=BLOCK_HEADDIM,
-                EVEN_M=EVEN_M,
-                EVEN_N=EVEN_N,
-                EVEN_HEADDIM=EVEN_HEADDIM,
-                BLOCK_M=BLOCK_M,
-                BLOCK_N=BLOCK_N,
-            )
-    else:
-        start_n = tl.program_id(0)
-        _bwd_kernel_one_col_block(
-            start_n,
-            Q,
-            K,
-            V,
-            Bias,
-            DO,
-            DQ,
-            DK,
-            DV,
-            LSE,
-            D,
-            softmax_scale,
-            stride_qm,
-            stride_kn,
-            stride_vn,
-            stride_bm,
-            stride_dom,
-            stride_dqm,
-            stride_dkn,
-            stride_dvn,
-            seqlen_q,
-            seqlen_k,
-            headdim,
-            ATOMIC_ADD=True,
-            BIAS_TYPE=BIAS_TYPE,
-            IS_CAUSAL=IS_CAUSAL,
-            BLOCK_HEADDIM=BLOCK_HEADDIM,
-            EVEN_M=EVEN_M,
-            EVEN_N=EVEN_N,
-            EVEN_HEADDIM=EVEN_HEADDIM,
-            BLOCK_M=BLOCK_M,
-            BLOCK_N=BLOCK_N,
-        )
-
-
-def _flash_attn_forward(q, k, v, bias=None, causal=False, softmax_scale=None):
-    # shape constraints
-    batch, seqlen_q, nheads, d = q.shape
-    _, seqlen_k, _, _ = k.shape
-    assert k.shape == (batch, seqlen_k, nheads, d)
-    assert v.shape == (batch, seqlen_k, nheads, d)
-    assert d <= 128, "FlashAttention only support head dimensions up to 128"
-    assert q.dtype == k.dtype == v.dtype, "All tensors must have the same type"
-    assert q.dtype in [torch.float16, torch.bfloat16], "Only support fp16 and bf16"
-    assert q.is_cuda and k.is_cuda and v.is_cuda
-    softmax_scale = softmax_scale or 1.0 / math.sqrt(d)
-
-    has_bias = bias is not None
-    bias_type = "none"
-    if has_bias:
-        assert bias.dtype in [q.dtype, torch.float]
-        assert bias.is_cuda
-        assert bias.dim() == 4
-        if bias.stride(-1) != 1:
-            bias = bias.contiguous()
-        if bias.shape[2:] == (1, seqlen_k):
-            bias_type = "vector"
-        elif bias.shape[2:] == (seqlen_q, seqlen_k):
-            bias_type = "matrix"
-        else:
-            raise RuntimeError(
-                "Last 2 dimensions of bias must be (1, seqlen_k)" " or (seqlen_q, seqlen_k)"
-            )
-        bias = bias.expand(batch, nheads, seqlen_q, seqlen_k)
-    bias_strides = (bias.stride(0), bias.stride(1), bias.stride(2)) if has_bias else (0, 0, 0)
-
-    seqlen_q_rounded = math.ceil(seqlen_q / 128) * 128
-    lse = torch.empty((batch, nheads, seqlen_q_rounded), device=q.device, dtype=torch.float32)
-    tmp = torch.empty((batch, nheads, seqlen_q_rounded), device=q.device, dtype=torch.float32)
-    o = torch.empty_like(q)
-
-    BLOCK_HEADDIM = max(triton.next_power_of_2(d), 16)
-    BLOCK = 128
-    num_warps = 4 if d <= 64 else 8
-    grid = lambda META: (triton.cdiv(seqlen_q, META["BLOCK_M"]), batch * nheads)
-    _fwd_kernel[grid](
-        q,
-        k,
-        v,
-        bias,
-        o,
-        lse,
-        tmp,
-        softmax_scale,
-        q.stride(0),
-        q.stride(2),
-        q.stride(1),
-        k.stride(0),
-        k.stride(2),
-        k.stride(1),
-        v.stride(0),
-        v.stride(2),
-        v.stride(1),
-        *bias_strides,
-        o.stride(0),
-        o.stride(2),
-        o.stride(1),
-        nheads,
-        seqlen_q,
-        seqlen_k,
-        seqlen_q_rounded,
-        d,
-        seqlen_q // 32,
-        seqlen_k // 32,  # key for triton cache (limit number of compilations)
-        # Can't use kwargs here because triton autotune expects key to be args, not kwargs
-        # IS_CAUSAL=causal, BLOCK_HEADDIM=d,
-        bias_type,
-        causal,
-        BLOCK_HEADDIM,
-        BLOCK_M=BLOCK,
-        BLOCK_N=BLOCK,
-        num_warps=num_warps,
-        num_stages=1,
-    )
-    return o, lse, softmax_scale  # softmax_scale could have been updated
-
-
-def _flash_attn_backward(
-    do, q, k, v, o, lse, dq, dk, dv, bias=None, causal=False, softmax_scale=None
-):
-    # Make sure that the last dimension is contiguous
-    if do.stride(-1) != 1:
-        do = do.contiguous()
-    batch, seqlen_q, nheads, d = q.shape
-    _, seqlen_k, _, _ = k.shape
-    # assert d in {16, 32, 64, 128}
-    assert d <= 128
-    seqlen_q_rounded = math.ceil(seqlen_q / 128) * 128
-    assert lse.shape == (batch, nheads, seqlen_q_rounded)
-    assert q.stride(-1) == k.stride(-1) == v.stride(-1) == o.stride(-1) == 1
-    assert dq.stride(-1) == dk.stride(-1) == dv.stride(-1) == 1
-    softmax_scale = softmax_scale or 1.0 / math.sqrt(d)
-    # dq_accum = torch.zeros_like(q, dtype=torch.float32)
-    dq_accum = torch.empty_like(q, dtype=torch.float32)
-    delta = torch.empty_like(lse)
-    # delta = torch.zeros_like(lse)
-
-    BLOCK_HEADDIM = max(triton.next_power_of_2(d), 16)
-    grid = lambda META: (triton.cdiv(seqlen_q, META["BLOCK_M"]), batch * nheads)
-    _bwd_preprocess_do_o_dot[grid](
-        o,
-        do,
-        delta,
-        o.stride(0),
-        o.stride(2),
-        o.stride(1),
-        do.stride(0),
-        do.stride(2),
-        do.stride(1),
-        nheads,
-        seqlen_q,
-        seqlen_q_rounded,
-        d,
-        BLOCK_M=128,
-        BLOCK_HEADDIM=BLOCK_HEADDIM,
-    )
-
-    has_bias = bias is not None
-    bias_type = "none"
-    if has_bias:
-        assert bias.dtype in [q.dtype, torch.float]
-        assert bias.is_cuda
-        assert bias.dim() == 4
-        assert bias.stride(-1) == 1
-        if bias.shape[2:] == (1, seqlen_k):
-            bias_type = "vector"
-        elif bias.shape[2:] == (seqlen_q, seqlen_k):
-            bias_type = "matrix"
-        else:
-            raise RuntimeError(
-                "Last 2 dimensions of bias must be (1, seqlen_k)" " or (seqlen_q, seqlen_k)"
-            )
-        bias = bias.expand(batch, nheads, seqlen_q, seqlen_k)
-    bias_strides = (bias.stride(0), bias.stride(1), bias.stride(2)) if has_bias else (0, 0, 0)
-
-    # BLOCK_M = 128
-    # BLOCK_N = 64
-    # num_warps = 4
-    grid = lambda META: (
-        triton.cdiv(seqlen_k, META["BLOCK_N"]) if META["SEQUENCE_PARALLEL"] else 1,
-        batch * nheads,
-    )
-    _bwd_kernel[grid](
-        q,
-        k,
-        v,
-        bias,
-        do,
-        dq_accum,
-        dk,
-        dv,
-        lse,
-        delta,
-        softmax_scale,
-        q.stride(0),
-        q.stride(2),
-        q.stride(1),
-        k.stride(0),
-        k.stride(2),
-        k.stride(1),
-        v.stride(0),
-        v.stride(2),
-        v.stride(1),
-        *bias_strides,
-        do.stride(0),
-        do.stride(2),
-        do.stride(1),
-        dq_accum.stride(0),
-        dq_accum.stride(2),
-        dq_accum.stride(1),
-        dk.stride(0),
-        dk.stride(2),
-        dk.stride(1),
-        dv.stride(0),
-        dv.stride(2),
-        dv.stride(1),
-        nheads,
-        seqlen_q,
-        seqlen_k,
-        seqlen_q_rounded,
-        d,
-        seqlen_q // 32,
-        seqlen_k // 32,  # key for triton cache (limit number of compilations)
-        # Can't use kwargs here because triton autotune expects key to be args, not kwargs
-        # IS_CAUSAL=causal, BLOCK_HEADDIM=d,
-        bias_type,
-        causal,
-        BLOCK_HEADDIM,
-        # SEQUENCE_PARALLEL=False,
-        # BLOCK_M=BLOCK_M, BLOCK_N=BLOCK_N,
-        # num_warps=num_warps,
-        # num_stages=1,
-    )
-    dq.copy_(dq_accum)
-
-
-class FlashAttnQKVPackedFunc(torch.autograd.Function):
-    @staticmethod
-    def forward(ctx, qkv, bias=None, causal=False, softmax_scale=None):
-        """
-        qkv: (batch, seqlen, 3, nheads, headdim)
-        bias: optional, shape broadcastible to (batch, nheads, seqlen, seqlen).
-            For example, ALiBi mask for causal would have shape (1, nheads, 1, seqlen).
-            ALiBi mask for non-causal would have shape (1, nheads, seqlen, seqlen)
-        """
-        # Make sure that the last dimension is contiguous
-        if qkv.stride(-1) != 1:
-            qkv = qkv.contiguous()
-        o, lse, ctx.softmax_scale = _flash_attn_forward(
-            qkv[:, :, 0],
-            qkv[:, :, 1],
-            qkv[:, :, 2],
-            bias=bias,
-            causal=causal,
-            softmax_scale=softmax_scale,
-        )
-        ctx.save_for_backward(qkv, o, lse, bias)
-        ctx.causal = causal
-        return o
-
-    @staticmethod
-    def backward(ctx, do):
-        qkv, o, lse, bias = ctx.saved_tensors
-        assert not ctx.needs_input_grad[1], "FlashAttention does not support bias gradient yet"
-        # Triton's autotune causes the Tensor._version to change, and so Pytorch autograd
-        # does a memcpy. To avoid this we run in inference_mode, which doesn't track the version.
-        with torch.inference_mode():
-            dqkv = torch.empty_like(qkv)
-            _flash_attn_backward(
-                do,
-                qkv[:, :, 0],
-                qkv[:, :, 1],
-                qkv[:, :, 2],
-                o,
-                lse,
-                dqkv[:, :, 0],
-                dqkv[:, :, 1],
-                dqkv[:, :, 2],
-                bias=bias,
-                causal=ctx.causal,
-                softmax_scale=ctx.softmax_scale,
-            )
-        return dqkv, None, None, None
-
-
-flash_attn_qkvpacked_func = FlashAttnQKVPackedFunc.apply
-
-
-class FlashAttnKVPackedFunc(torch.autograd.Function):
-    @staticmethod
-    def forward(ctx, q, kv, bias=None, causal=False, softmax_scale=None):
-        """
-        q: (batch, seqlen_q, nheads, headdim)
-        kv: (batch, seqlen_k, 2, nheads, headdim)
-        bias: optional, shape broadcastible to (batch, nheads, seqlen_q, seqlen_k).
-            For example, ALiBi mask for causal would have shape (1, nheads, 1, seqlen_k).
-            ALiBi mask for non-causal would have shape (1, nheads, seqlen_q, seqlen_k)
-        """
-        # Make sure that the last dimension is contiguous
-        q, kv = [x if x.stride(-1) == 1 else x.contiguous() for x in [q, kv]]
-        o, lse, ctx.softmax_scale = _flash_attn_forward(
-            q, kv[:, :, 0], kv[:, :, 1], bias=bias, causal=causal, softmax_scale=softmax_scale
-        )
-        ctx.save_for_backward(q, kv, o, lse, bias)
-        ctx.causal = causal
-        return o
-
-    @staticmethod
-    def backward(ctx, do):
-        q, kv, o, lse, bias = ctx.saved_tensors
-        if len(ctx.needs_input_grad) >= 3:
-            assert not ctx.needs_input_grad[2], "FlashAttention does not support bias gradient yet"
-        # Triton's autotune causes the Tensor._version to change, and so Pytorch autograd
-        # does a memcpy. To avoid this we run in inference_mode, which doesn't track the version.
-        with torch.inference_mode():
-            dq = torch.empty_like(q)
-            dkv = torch.empty_like(kv)
-            _flash_attn_backward(
-                do,
-                q,
-                kv[:, :, 0],
-                kv[:, :, 1],
-                o,
-                lse,
-                dq,
-                dkv[:, :, 0],
-                dkv[:, :, 1],
-                bias=bias,
-                causal=ctx.causal,
-                softmax_scale=ctx.softmax_scale,
-            )
-        return dq, dkv, None, None, None
-
-
-flash_attn_kvpacked_func = FlashAttnKVPackedFunc.apply
-
-
-class FlashAttnFunc(torch.autograd.Function):
-    @staticmethod
-    def forward(ctx, q, k, v, bias=None, causal=False, softmax_scale=None):
-        """
-        q: (batch_size, seqlen_q, nheads, headdim)
-        k, v: (batch_size, seqlen_k, nheads, headdim)
-        bias: optional, shape broadcastible to (batch, nheads, seqlen_q, seqlen_k).
-            For example, ALiBi mask for causal would have shape (1, nheads, 1, seqlen_k).
-            ALiBi mask for non-causal would have shape (1, nheads, seqlen_q, seqlen_k)
-        """
-        # Make sure that the last dimension is contiguous
-        q, k, v = [x if x.stride(-1) == 1 else x.contiguous() for x in [q, k, v]]
-        o, lse, ctx.softmax_scale = _flash_attn_forward(
-            q, k, v, bias=bias, causal=causal, softmax_scale=softmax_scale
-        )
-        ctx.save_for_backward(q, k, v, o, lse, bias)
-        ctx.causal = causal
-        return o
-
-    @staticmethod
-    def backward(ctx, do):
-        q, k, v, o, lse, bias = ctx.saved_tensors
-        assert not ctx.needs_input_grad[3], "FlashAttention does not support bias gradient yet"
-        # Triton's autotune causes the Tensor._version to change, and so Pytorch autograd
-        # does a memcpy. To avoid this we run in inference_mode, which doesn't track the version.
-        with torch.inference_mode():
-            dq = torch.empty_like(q)
-            dk = torch.empty_like(k)
-            dv = torch.empty_like(v)
-            _flash_attn_backward(
-                do,
-                q,
-                k,
-                v,
-                o,
-                lse,
-                dq,
-                dk,
-                dv,
-                bias=bias,
-                causal=ctx.causal,
-                softmax_scale=ctx.softmax_scale,
-            )
-        return dq, dk, dv, None, None, None
-
-flash_attn_func = FlashAttnFunc.apply