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vllm/model_executor/layers/fla/ops/wy_fast.py

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+# SPDX-License-Identifier: Apache-2.0
+# SPDX-FileCopyrightText: Copyright contributors to the vLLM project
+# SPDX-FileCopyrightText: Songlin Yang, Yu Zhang
+#
+# This file contains code copied from the flash-linear-attention project.
+# The original source code was licensed under the MIT license and included
+# the following copyright notice:
+# Copyright (c) 2023-2025, Songlin Yang, Yu Zhang
+
+# ruff: noqa: E501
+from typing import Optional
+
+import torch
+
+from vllm.triton_utils import tl, triton
+
+from .index import prepare_chunk_indices
+
+
+@triton.heuristics({'IS_VARLEN': lambda args: args['cu_seqlens'] is not None})
+@triton.autotune(
+    configs=[
+        triton.Config({}, num_warps=num_warps, num_stages=num_stages)
+        for num_warps in [2, 4, 8] for num_stages in [2, 3, 4]
+    ],
+    key=['H', 'K', 'V', 'BT', 'BK', 'BV', 'IS_VARLEN'],
+)
+@triton.jit(do_not_specialize=['T'])
+def recompute_w_u_fwd_kernel(k, v, beta, w, u, A, g, cu_seqlens, chunk_indices,
+                             T, H: tl.constexpr, Hg: tl.constexpr,
+                             K: tl.constexpr, V: tl.constexpr,
+                             BT: tl.constexpr, BK: tl.constexpr,
+                             BV: tl.constexpr, IS_VARLEN: tl.constexpr):
+    i_t, i_bh = tl.program_id(0), tl.program_id(1)
+    i_b, i_h = i_bh // H, i_bh % H
+    if IS_VARLEN:
+        i_n, i_t = tl.load(chunk_indices + i_t * 2).to(
+            tl.int32), tl.load(chunk_indices + i_t * 2 + 1).to(tl.int32)
+        bos, eos = tl.load(cu_seqlens + i_n).to(
+            tl.int32), tl.load(cu_seqlens + i_n + 1).to(tl.int32)
+        T = eos - bos
+    else:
+        bos, eos = i_b * T, i_b * T + T
+    p_beta = tl.make_block_ptr(beta + bos * H + i_h, (T, ), (H, ),
+                               (i_t * BT, ), (BT, ), (0, ))
+    p_g = tl.make_block_ptr(g + (bos * H + i_h), (T, ), (H, ), (i_t * BT, ),
+                            (BT, ), (0, ))
+    p_A = tl.make_block_ptr(A + (bos * H + i_h) * BT, (T, BT), (H * BT, 1),
+                            (i_t * BT, 0), (BT, BT), (1, 0))
+    b_beta = tl.load(p_beta, boundary_check=(0, ))
+    b_A = tl.load(p_A, boundary_check=(0, 1))
+    b_g = tl.exp(tl.load(p_g, boundary_check=(0, )))
+
+    for i_v in range(tl.cdiv(V, BV)):
+        p_v = tl.make_block_ptr(v + (bos * H + i_h) * V, (T, V), (H * V, 1),
+                                (i_t * BT, i_v * BV), (BT, BV), (1, 0))
+        p_u = tl.make_block_ptr(u + (bos * H + i_h) * V, (T, V), (H * V, 1),
+                                (i_t * BT, i_v * BV), (BT, BV), (1, 0))
+        b_v = tl.load(p_v, boundary_check=(0, 1))
+        b_vb = (b_v * b_beta[:, None]).to(b_v.dtype)
+        b_u = tl.dot(b_A, b_vb, allow_tf32=False)
+        tl.store(p_u, b_u.to(p_u.dtype.element_ty), boundary_check=(0, 1))
+
+    for i_k in range(tl.cdiv(K, BK)):
+        p_k = tl.make_block_ptr(k + (bos * Hg + i_h // (H // Hg)) * K, (T, K),
+                                (Hg * K, 1), (i_t * BT, i_k * BK), (BT, BK),
+                                (1, 0))
+        p_w = tl.make_block_ptr(w + (bos * H + i_h) * K, (T, K), (H * K, 1),
+                                (i_t * BT, i_k * BK), (BT, BK), (1, 0))
+        b_k = tl.load(p_k, boundary_check=(0, 1))
+        b_kb = (b_k * b_beta[:, None] * b_g[:, None]).to(b_k.dtype)
+        b_w = tl.dot(b_A, b_kb)
+        tl.store(p_w, b_w.to(p_w.dtype.element_ty), boundary_check=(0, 1))
+
+
+def recompute_w_u_fwd(
+    k: torch.Tensor,
+    v: torch.Tensor,
+    beta: torch.Tensor,
+    g_cumsum: torch.Tensor,
+    A: torch.Tensor,
+    cu_seqlens: Optional[torch.LongTensor],
+) -> tuple[torch.Tensor, torch.Tensor]:
+    B, T, Hg, K, V = *k.shape, v.shape[-1]
+    H = v.shape[-2]
+    BT = A.shape[-1]
+
+    chunk_indices = prepare_chunk_indices(
+        cu_seqlens, BT) if cu_seqlens is not None else None
+    NT = triton.cdiv(T, BT) if cu_seqlens is None else len(chunk_indices)
+    BK = 64
+    BV = 64
+    u = torch.empty_like(v)
+    w = k.new_empty(B, T, H, K)
+    recompute_w_u_fwd_kernel[(NT, B * H)](
+        k=k,
+        v=v,
+        beta=beta,
+        w=w,
+        u=u,
+        A=A,
+        g=g_cumsum,
+        cu_seqlens=cu_seqlens,
+        chunk_indices=chunk_indices,
+        T=T,
+        H=H,
+        Hg=Hg,
+        K=K,
+        V=V,
+        BT=BT,
+        BK=BK,
+        BV=BV,
+    )
+    return w, u