add flash linear attention triton kernel (#10239)

2025-09-10 21:47:20 -07:00
parent 5b64f006ec
commit dc491b399d
14 changed files with 3590 additions and 0 deletions
@@ -0,0 +1,640 @@
+# Adapt from https://github.com/fla-org/flash-linear-attention/blob/main/fla/ops/gated_delta_rule/fused_recurrent.py
+# -*- coding: utf-8 -*-
+# Copyright (c) 2023-2025, Songlin Yang, Yu Zhang
+
+from typing import Optional, Tuple
+
+import torch
+import triton
+import triton.language as tl
+
+from sglang.srt.layers.attention.fla.op import exp
+from sglang.srt.layers.attention.fla.utils import input_guard
+
+
+@triton.heuristics(
+    {
+        "USE_INITIAL_STATE": lambda args: args["h0"] is not None,
+        "STORE_FINAL_STATE": lambda args: args["ht"] is not None,
+        "IS_VARLEN": lambda args: args["cu_seqlens"] is not None,
+    }
+)
+@triton.jit(do_not_specialize=["T"])
+def fused_recurrent_gated_delta_rule_fwd_kernel(
+    q,
+    k,
+    v,
+    g,
+    beta,
+    o,
+    h0,
+    ht,
+    cu_seqlens,
+    scale,
+    T,
+    B: tl.constexpr,
+    H: tl.constexpr,
+    HV: tl.constexpr,
+    K: tl.constexpr,
+    V: tl.constexpr,
+    BK: tl.constexpr,
+    BV: tl.constexpr,
+    USE_INITIAL_STATE: tl.constexpr,  # whether to use initial state
+    STORE_FINAL_STATE: tl.constexpr,  # whether to store final state
+    IS_BETA_HEADWISE: tl.constexpr,  # whether beta is headwise vector or scalar,
+    USE_QK_L2NORM_IN_KERNEL: tl.constexpr,
+    IS_VARLEN: tl.constexpr,
+):
+    i_k, i_v, i_nh = tl.program_id(0), tl.program_id(1), tl.program_id(2)
+    i_n, i_hv = i_nh // HV, i_nh % HV
+    i_h = i_hv // (HV // H)
+    if IS_VARLEN:
+        bos, eos = tl.load(cu_seqlens + i_n).to(tl.int64), tl.load(
+            cu_seqlens + i_n + 1
+        ).to(tl.int64)
+        all = T
+        T = eos - bos
+    else:
+        bos, eos = i_n * T, i_n * T + T
+        all = B * T
+    o_k = i_k * BK + tl.arange(0, BK)
+    o_v = i_v * BV + tl.arange(0, BV)
+
+    p_q = q + (bos * H + i_h) * K + o_k
+    p_k = k + (bos * H + i_h) * K + o_k
+    p_v = v + (bos * HV + i_hv) * V + o_v
+    if IS_BETA_HEADWISE:
+        p_beta = beta + (bos * HV + i_hv) * V + o_v
+    else:
+        p_beta = beta + bos * HV + i_hv
+    p_g = g + bos * HV + i_hv
+    p_o = o + ((i_k * all + bos) * HV + i_hv) * V + o_v
+
+    mask_k = o_k < K
+    mask_v = o_v < V
+    mask_h = mask_k[:, None] & mask_v[None, :]
+
+    b_h = tl.zeros([BK, BV], dtype=tl.float32)
+    if USE_INITIAL_STATE:
+        p_h0 = h0 + i_nh * K * V + o_k[:, None] * V + o_v[None, :]
+        b_h += tl.load(p_h0, mask=mask_h, other=0).to(tl.float32)
+
+    for _ in range(0, T):
+        b_q = tl.load(p_q, mask=mask_k, other=0).to(tl.float32)
+        b_k = tl.load(p_k, mask=mask_k, other=0).to(tl.float32)
+        b_v = tl.load(p_v, mask=mask_v, other=0).to(tl.float32)
+        b_g = tl.load(p_g).to(tl.float32)
+
+        if USE_QK_L2NORM_IN_KERNEL:
+            b_q = b_q / (tl.sqrt(tl.sum(b_q * b_q)) + 1e-6)
+            b_k = b_k / (tl.sqrt(tl.sum(b_k * b_k)) + 1e-6)
+        b_q = b_q * scale
+        # [BK, BV]
+        b_h *= exp(b_g)
+        # [BV]
+        b_v -= tl.sum(b_h * b_k[:, None], 0)
+        if IS_BETA_HEADWISE:
+            b_beta = tl.load(p_beta, mask=mask_v, other=0).to(tl.float32)
+        else:
+            b_beta = tl.load(p_beta).to(tl.float32)
+        b_v *= b_beta
+        # [BK, BV]
+        b_h += b_k[:, None] * b_v[None, :]
+        # [BV]
+        b_o = tl.sum(b_h * b_q[:, None], 0)
+        tl.store(p_o, b_o.to(p_o.dtype.element_ty), mask=mask_v)
+
+        p_q += H * K
+        p_k += H * K
+        p_o += HV * V
+        p_v += HV * V
+        p_g += HV
+        p_beta += HV * (V if IS_BETA_HEADWISE else 1)
+
+    if STORE_FINAL_STATE:
+        p_ht = ht + i_nh * K * V + o_k[:, None] * V + o_v[None, :]
+        tl.store(p_ht, b_h.to(p_ht.dtype.element_ty), mask=mask_h)
+
+
+def fused_recurrent_gated_delta_rule_fwd(
+    q: torch.Tensor,
+    k: torch.Tensor,
+    v: torch.Tensor,
+    g: torch.Tensor,
+    beta: torch.Tensor,
+    scale: float,
+    initial_state: torch.Tensor,
+    output_final_state: bool,
+    use_qk_l2norm_in_kernel: bool = False,
+    cu_seqlens: Optional[torch.LongTensor] = None,
+) -> Tuple[torch.Tensor, torch.Tensor]:
+    B, T, H, K, V = *k.shape, v.shape[-1]
+    HV = v.shape[2]
+    N = B if cu_seqlens is None else len(cu_seqlens) - 1
+    BK, BV = triton.next_power_of_2(K), min(triton.next_power_of_2(V), 8)
+    NK, NV = triton.cdiv(K, BK), triton.cdiv(V, BV)
+    assert NK == 1, "NK > 1 is not supported yet"
+    num_stages = 3
+    num_warps = 1
+
+    o = q.new_empty(NK, *v.shape)
+    if output_final_state:
+        final_state = q.new_empty(N, HV, K, V, dtype=torch.float32)
+    else:
+        final_state = None
+
+    grid = (NK, NV, N * HV)
+    fused_recurrent_gated_delta_rule_fwd_kernel[grid](
+        q=q,
+        k=k,
+        v=v,
+        g=g,
+        beta=beta,
+        o=o,
+        h0=initial_state,
+        ht=final_state,
+        cu_seqlens=cu_seqlens,
+        scale=scale,
+        T=T,
+        B=B,
+        H=H,
+        HV=HV,
+        K=K,
+        V=V,
+        BK=BK,
+        BV=BV,
+        IS_BETA_HEADWISE=beta.ndim == v.ndim,
+        USE_QK_L2NORM_IN_KERNEL=use_qk_l2norm_in_kernel,
+        num_warps=num_warps,
+        num_stages=num_stages,
+    )
+    o = o.squeeze(0)
+    return o, final_state
+
+
+class FusedRecurrentFunction(torch.autograd.Function):
+
+    @staticmethod
+    @input_guard
+    def forward(
+        ctx,
+        q: torch.Tensor,
+        k: torch.Tensor,
+        v: torch.Tensor,
+        g: torch.Tensor,
+        beta: torch.Tensor,
+        scale: float,
+        initial_state: torch.Tensor,
+        output_final_state: bool,
+        cu_seqlens: Optional[torch.LongTensor] = None,
+        use_qk_l2norm_in_kernel: bool = False,
+    ):
+        o, final_state = fused_recurrent_gated_delta_rule_fwd(
+            q=q,
+            k=k,
+            v=v,
+            g=g,
+            beta=beta,
+            scale=scale,
+            initial_state=initial_state,
+            output_final_state=output_final_state,
+            use_qk_l2norm_in_kernel=use_qk_l2norm_in_kernel,
+            cu_seqlens=cu_seqlens,
+        )
+
+        return o, final_state
+
+    @staticmethod
+    @input_guard
+    def backward(ctx, do, dht):
+        raise NotImplementedError(
+            "Backward pass is not implemented yet and we do not have plans to implement it "
+            "because we haven't figured out how to compute dg without materializing the full "
+            "hidden states for all time steps."
+        )
+
+
+def fused_recurrent_gated_delta_rule(
+    q: torch.Tensor,
+    k: torch.Tensor,
+    v: torch.Tensor,
+    g: torch.Tensor,
+    beta: torch.Tensor = None,
+    scale: float = None,
+    initial_state: torch.Tensor = None,
+    output_final_state: bool = False,
+    cu_seqlens: Optional[torch.LongTensor] = None,
+    use_qk_l2norm_in_kernel: bool = False,
+) -> Tuple[torch.Tensor, torch.Tensor]:
+    r"""
+    Args:
+        q (torch.Tensor):
+            queries of shape `[B, T, H, K]`.
+        k (torch.Tensor):
+            keys of shape `[B, T, H, K]`.
+        v (torch.Tensor):
+            values of shape `[B, T, HV, V]`.
+            GVA is applied if `HV > H`.
+        g (torch.Tensor):
+            g (decays) of shape `[B, T, HV]`.
+        beta (torch.Tensor):
+            betas of shape `[B, T, HV]`.
+        scale (Optional[int]):
+            Scale factor for the RetNet attention scores.
+            If not provided, it will default to `1 / sqrt(K)`. Default: `None`.
+        initial_state (Optional[torch.Tensor]):
+            Initial state of shape `[N, HV, K, V]` for `N` input sequences.
+            For equal-length input sequences, `N` equals the batch size `B`.
+            Default: `None`.
+        output_final_state (Optional[bool]):
+            Whether to output the final state of shape `[N, HV, K, V]`. Default: `False`.
+        cu_seqlens (torch.LongTensor):
+            Cumulative sequence lengths of shape `[N+1]` used for variable-length training,
+            consistent with the FlashAttention API.
+    Returns:
+        o (torch.Tensor):
+            Outputs of shape `[B, T, HV, V]`.
+        final_state (torch.Tensor):
+            Final state of shape `[N, HV, K, V]` if `output_final_state=True` else `None`.
+    Examples::
+        >>> import torch
+        >>> import torch.nn.functional as F
+        >>> from einops import rearrange
+        >>> from fla.ops.gated_delta_rule import fused_recurrent_gated_delta_rule
+        # inputs with equal lengths
+        >>> B, T, H, HV, K, V = 4, 2048, 4, 8, 512, 512
+        >>> q = torch.randn(B, T, H, K, device='cuda')
+        >>> k = F.normalize(torch.randn(B, T, H, K, device='cuda'), p=2, dim=-1)
+        >>> v = torch.randn(B, T, HV, V, device='cuda')
+        >>> g = F.logsigmoid(torch.rand(B, T, HV, device='cuda'))
+        >>> beta = torch.rand(B, T, HV, device='cuda').sigmoid()
+        >>> h0 = torch.randn(B, HV, K, V, device='cuda')
+        >>> o, ht = fused_gated_recurrent_delta_rule(
+            q, k, v, g, beta,
+            initial_state=h0,
+            output_final_state=True
+        )
+        # for variable-length inputs, the batch size `B` is expected to be 1 and `cu_seqlens` is required
+        >>> q, k, v, g, beta = map(lambda x: rearrange(x, 'b t ... -> 1 (b t) ...'), (q, k, v, g, beta))
+        # for a batch with 4 sequences, `cu_seqlens` with 5 start/end positions are expected
+        >>> cu_seqlens = q.new_tensor([0, 2048, 4096, 6144, 8192], dtype=torch.long)
+        >>> o_var, ht_var = fused_gated_recurrent_delta_rule(
+            q, k, v, g, beta,
+            initial_state=h0,
+            output_final_state=True,
+            cu_seqlens=cu_seqlens
+        )
+    """
+    if cu_seqlens is not None:
+        if q.shape[0] != 1:
+            raise ValueError(
+                f"The batch size is expected to be 1 rather than {q.shape[0]} when using `cu_seqlens`."
+                f"Please flatten variable-length inputs before processing."
+            )
+        if initial_state is not None and initial_state.shape[0] != len(cu_seqlens) - 1:
+            raise ValueError(
+                f"The number of initial states is expected to be equal to the number of input sequences, "
+                f"i.e., {len(cu_seqlens) - 1} rather than {initial_state.shape[0]}."
+            )
+    if scale is None:
+        scale = k.shape[-1] ** -0.5
+    else:
+        assert scale > 0, "scale must be positive"
+    if beta is None:
+        beta = torch.ones_like(q[..., 0])
+    o, final_state = FusedRecurrentFunction.apply(
+        q,
+        k,
+        v,
+        g,
+        beta,
+        scale,
+        initial_state,
+        output_final_state,
+        cu_seqlens,
+        use_qk_l2norm_in_kernel,
+    )
+    return o, final_state
+
+
+@triton.heuristics(
+    {
+        "USE_INITIAL_STATE": lambda args: args["h0_source"] is not None,
+        "IS_VARLEN": lambda args: args["cu_seqlens"] is not None,
+        "CACHE_INTERMEDIATE_STATES": lambda args: args["intermediate_states_buffer"]
+        is not None,
+    }
+)
+@triton.jit(do_not_specialize=["T"])
+def fused_recurrent_gated_delta_rule_update_fwd_kernel(
+    q,
+    k,
+    v,
+    g,
+    beta,
+    o,
+    h0_source,
+    h0_indices,
+    cu_seqlens,
+    scale,
+    intermediate_states_buffer,
+    cache_steps,
+    T,
+    B: tl.constexpr,
+    H: tl.constexpr,
+    HV: tl.constexpr,
+    K: tl.constexpr,
+    V: tl.constexpr,
+    BK: tl.constexpr,
+    BV: tl.constexpr,
+    USE_INITIAL_STATE: tl.constexpr,  # whether to use initial state
+    IS_BETA_HEADWISE: tl.constexpr,  # whether beta is headwise vector or scalar,
+    USE_QK_L2NORM_IN_KERNEL: tl.constexpr,
+    IS_VARLEN: tl.constexpr,
+    DISABLE_STATE_UPDATE: tl.constexpr,  # whether to disable final state update
+    DISABLE_OUTPUT_CALCULATION: tl.constexpr,  # whether to disable output calculation
+    CACHE_INTERMEDIATE_STATES: tl.constexpr,
+):
+    i_k, i_v, i_nh = tl.program_id(0), tl.program_id(1), tl.program_id(2)
+    i_n, i_hv = i_nh // HV, i_nh % HV
+    i_h = i_hv // (HV // H)
+    if IS_VARLEN:
+        bos, eos = tl.load(cu_seqlens + i_n).to(tl.int64), tl.load(
+            cu_seqlens + i_n + 1
+        ).to(tl.int64)
+        all = T
+        T = eos - bos
+    else:
+        bos, eos = i_n * T, i_n * T + T
+        all = B * T
+    o_k = i_k * BK + tl.arange(0, BK)
+    o_v = i_v * BV + tl.arange(0, BV)
+
+    p_q = q + (bos * H + i_h) * K + o_k
+    p_k = k + (bos * H + i_h) * K + o_k
+    p_v = v + (bos * HV + i_hv) * V + o_v
+    if IS_BETA_HEADWISE:
+        p_beta = beta + (bos * HV + i_hv) * V + o_v
+    else:
+        p_beta = beta + bos * HV + i_hv
+    p_g = g + bos * HV + i_hv
+    p_o = o + ((i_k * all + bos) * HV + i_hv) * V + o_v
+
+    mask_k = o_k < K
+    mask_v = o_v < V
+    mask_h = mask_k[:, None] & mask_v[None, :]
+
+    b_h = tl.zeros([BK, BV], dtype=tl.float32)
+    if USE_INITIAL_STATE:
+        idx = tl.load(h0_indices + i_n)
+        # Add bounds checking for idx
+        if idx >= 0:  # Assuming negative indices are invalid
+            p_h0 = (
+                h0_source
+                + idx * HV * K * V
+                + i_hv * K * V
+                + o_k[:, None] * V
+                + o_v[None, :]
+            )
+            b_h += tl.load(p_h0, mask=mask_h, other=0).to(tl.float32)
+
+    # Prepare intermediate state cache variables if enabled
+    cache_idx = -1
+    if CACHE_INTERMEDIATE_STATES:
+        cache_idx = tl.load(h0_indices + i_n)
+
+    step_idx = 0
+    for _ in range(0, T):
+        b_q = tl.load(p_q, mask=mask_k, other=0).to(tl.float32)
+        b_k = tl.load(p_k, mask=mask_k, other=0).to(tl.float32)
+        b_v = tl.load(p_v, mask=mask_v, other=0).to(tl.float32)
+        b_g = tl.load(p_g).to(tl.float32)
+
+        if USE_QK_L2NORM_IN_KERNEL:
+            b_q = b_q / (tl.sqrt(tl.sum(b_q * b_q)) + 1e-6)
+            b_k = b_k / (tl.sqrt(tl.sum(b_k * b_k)) + 1e-6)
+        b_q = b_q * scale
+        # [BK, BV]
+        b_h *= exp(b_g)
+        # [BV]
+        b_v -= tl.sum(b_h * b_k[:, None], 0)
+        if IS_BETA_HEADWISE:
+            b_beta = tl.load(p_beta, mask=mask_v, other=0).to(tl.float32)
+        else:
+            b_beta = tl.load(p_beta).to(tl.float32)
+        b_v *= b_beta
+        # [BK, BV]
+        b_h += b_k[:, None] * b_v[None, :]
+        # [BV]
+        if not DISABLE_OUTPUT_CALCULATION:
+            b_o = tl.sum(b_h * b_q[:, None], 0)
+            # core attn output
+            tl.store(p_o, b_o.to(p_o.dtype.element_ty), mask=mask_v)
+
+        # store intermediate states if enabled
+        if CACHE_INTERMEDIATE_STATES:
+            if cache_idx >= 0:
+                # Compute cache pointer for this step
+                step_offset = step_idx * HV * K * V
+                cache_ptr = (
+                    intermediate_states_buffer
+                    + cache_idx * cache_steps * HV * K * V
+                    + step_offset
+                    + i_hv * K * V
+                    + o_k[:, None] * V
+                    + o_v[None, :]
+                )
+                tl.store(cache_ptr, b_h.to(cache_ptr.dtype.element_ty), mask=mask_h)
+
+        step_idx += 1
+
+        p_q += H * K
+        p_k += H * K
+        p_o += HV * V
+        p_v += HV * V
+        p_g += HV
+        p_beta += HV * (V if IS_BETA_HEADWISE else 1)
+
+    # Store final state back to h0_source with bounds checking
+    # ssm states
+    if not DISABLE_STATE_UPDATE:
+        idx = tl.load(h0_indices + i_n)
+        if idx >= 0:  # Add bounds checking
+            p_h0 = (
+                h0_source
+                + idx * HV * K * V
+                + i_hv * K * V
+                + o_k[:, None] * V
+                + o_v[None, :]
+            )
+            tl.store(p_h0, b_h.to(p_h0.dtype.element_ty), mask=mask_h)
+
+
+def fused_recurrent_gated_delta_rule_update_fwd(
+    q: torch.Tensor,
+    k: torch.Tensor,
+    v: torch.Tensor,
+    g: torch.Tensor,
+    beta: torch.Tensor,
+    scale: float,
+    initial_state_source: torch.Tensor,
+    initial_state_indices: torch.Tensor,
+    use_qk_l2norm_in_kernel: bool = False,
+    cu_seqlens: Optional[torch.LongTensor] = None,
+    disable_state_update: bool = False,
+    disable_output_calculation: bool = False,
+    intermediate_states_buffer: Optional[torch.Tensor] = None,
+    cache_steps: Optional[int] = None,
+) -> torch.Tensor:
+    B, T, H, K, V = *k.shape, v.shape[-1]
+    HV = v.shape[2]
+    N = B if cu_seqlens is None else len(cu_seqlens) - 1
+    BK, BV = triton.next_power_of_2(K), min(triton.next_power_of_2(V), 8)
+    NK, NV = triton.cdiv(K, BK), triton.cdiv(V, BV)
+    assert NK == 1, "NK > 1 is not supported yet"
+    num_stages = 3
+    num_warps = 1
+
+    if disable_output_calculation:
+        # When output calculation is disabled, allocate minimal tensor
+        o = q.new_empty(NK, 1, 1, 1, 1)  # minimal allocation
+    else:
+        o = q.new_empty(NK, *v.shape)
+
+    grid = (NK, NV, N * HV)
+
+    fused_recurrent_gated_delta_rule_update_fwd_kernel[grid](
+        q=q,
+        k=k,
+        v=v,
+        g=g,
+        beta=beta,
+        o=o,
+        h0_source=initial_state_source,
+        h0_indices=initial_state_indices,
+        cu_seqlens=cu_seqlens,
+        scale=scale,
+        intermediate_states_buffer=intermediate_states_buffer,
+        cache_steps=0 if cache_steps is None else cache_steps,
+        T=T,
+        B=B,
+        H=H,
+        HV=HV,
+        K=K,
+        V=V,
+        BK=BK,
+        BV=BV,
+        IS_BETA_HEADWISE=beta.ndim == v.ndim,
+        USE_QK_L2NORM_IN_KERNEL=use_qk_l2norm_in_kernel,
+        DISABLE_STATE_UPDATE=disable_state_update,
+        DISABLE_OUTPUT_CALCULATION=disable_output_calculation,
+        num_warps=num_warps,
+        num_stages=num_stages,
+    )
+    o = o.squeeze(0)
+    return o
+
+
+class FusedRecurrentUpdateFunction(torch.autograd.Function):
+
+    @staticmethod
+    @input_guard
+    def forward(
+        ctx,
+        q: torch.Tensor,
+        k: torch.Tensor,
+        v: torch.Tensor,
+        g: torch.Tensor,
+        beta: torch.Tensor,
+        scale: float,
+        initial_state_source: torch.Tensor,
+        initial_state_indices: torch.Tensor,
+        cu_seqlens: Optional[torch.LongTensor] = None,
+        use_qk_l2norm_in_kernel: bool = False,
+        disable_state_update: bool = False,
+        disable_output_calculation: bool = False,
+        intermediate_states_buffer: Optional[torch.Tensor] = None,
+        cache_steps: Optional[int] = None,
+    ):
+        o = fused_recurrent_gated_delta_rule_update_fwd(
+            q=q,
+            k=k,
+            v=v,
+            g=g,
+            beta=beta,
+            scale=scale,
+            initial_state_source=initial_state_source,
+            initial_state_indices=initial_state_indices,
+            use_qk_l2norm_in_kernel=use_qk_l2norm_in_kernel,
+            cu_seqlens=cu_seqlens,
+            disable_state_update=disable_state_update,
+            disable_output_calculation=disable_output_calculation,
+            intermediate_states_buffer=intermediate_states_buffer,
+            cache_steps=cache_steps,
+        )
+
+        return o
+
+    @staticmethod
+    @input_guard
+    def backward(ctx, do, dht):
+        raise NotImplementedError(
+            "Backward pass is not implemented yet and we do not have plans to implement it "
+            "because we haven't figured out how to compute dg without materializing the full "
+            "hidden states for all time steps."
+        )
+
+
+def fused_recurrent_gated_delta_rule_update(
+    q: torch.Tensor,
+    k: torch.Tensor,
+    v: torch.Tensor,
+    g: torch.Tensor,
+    beta: torch.Tensor = None,
+    scale: float = None,
+    initial_state_source: torch.Tensor = None,
+    initial_state_indices: torch.Tensor = None,
+    cu_seqlens: Optional[torch.LongTensor] = None,
+    use_qk_l2norm_in_kernel: bool = False,
+    disable_state_update: bool = False,
+    disable_output_calculation: bool = False,
+    intermediate_states_buffer: Optional[torch.Tensor] = None,
+    cache_steps: Optional[int] = None,
+) -> torch.Tensor:
+    if cu_seqlens is not None:
+        if q.shape[0] != 1:
+            raise ValueError(
+                f"The batch size is expected to be 1 rather than {q.shape[0]} when using `cu_seqlens`."
+                f"Please flatten variable-length inputs before processing."
+            )
+        if (
+            initial_state_source is not None
+            and initial_state_indices.shape[0] != len(cu_seqlens) - 1
+        ):
+            raise ValueError(
+                f"The number of initial states is expected to be equal to the number of input sequences, "
+                f"i.e., {len(cu_seqlens) - 1} rather than {initial_state_indices.shape[0]}."
+            )
+    if scale is None:
+        scale = k.shape[-1] ** -0.5
+    else:
+        assert scale > 0, "scale must be positive"
+    if beta is None:
+        beta = torch.ones_like(q[..., 0])
+    o = FusedRecurrentUpdateFunction.apply(
+        q,
+        k,
+        v,
+        g,
+        beta,
+        scale,
+        initial_state_source,
+        initial_state_indices,
+        cu_seqlens,
+        use_qk_l2norm_in_kernel,
+        disable_state_update,
+        disable_output_calculation,
+        intermediate_states_buffer,
+        cache_steps,
+    )
+    return o