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180 changes: 180 additions & 0 deletions examples/linear_attention/example_linear_attn_bwd.py
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# Copyright (c) Tile-AI Corporation.
# Licensed under the MIT License.

import torch
import tilelang as tl
import tilelang.language as T
from tilelang.profiler import do_bench

import argparse
from fla.ops.linear_attn import fused_chunk_linear_attn # We compare with FLA


def chunk_linear_attn_bwd_kernel(
B,
S,
H,
DK,
DV,
dtype: str = 'float16',
scale: float = None,
) -> torch.Tensor:

if scale is None:
scale = DK**-0.5
accum_dtype = 'float'

chunk_size = 64
BK = BV = 64
assert S % chunk_size == 0 and DK % BK == 0 and DV % BV == 0
NK = tl.cdiv(DK, BK)
NV = tl.cdiv(DV, BV)
NT = tl.cdiv(S, chunk_size)

@T.prim_func
def main(
Q: T.Tensor([B, S, H, DK], dtype),
K: T.Tensor([B, S, H, DK], dtype),
V: T.Tensor([B, S, H, DV], dtype),
dO: T.Tensor([B, S, H, DV], dtype),
dQ: T.Tensor([NV, B, S, H, DK], dtype),
dK: T.Tensor([NV, B, S, H, DK], dtype),
dV: T.Tensor([NK, B, S, H, DV], dtype),
):
with T.Kernel(NV, NK, B * H) as (i_v, i_k, i_bh):
i_b = i_bh // H
i_h = i_bh % H

ds = T.alloc_fragment([chunk_size, chunk_size], accum_dtype)
ds_shared = T.alloc_shared([chunk_size, chunk_size], dtype)
dq = T.alloc_fragment([chunk_size, BK], accum_dtype)
dk = T.alloc_fragment([chunk_size, BK], accum_dtype)
dv = T.alloc_fragment([chunk_size, BV], accum_dtype)
q = T.alloc_shared([chunk_size, BK], dtype)
k = T.alloc_shared([chunk_size, BK], dtype)
v = T.alloc_shared([chunk_size, BV], dtype)
do = T.alloc_shared([chunk_size, BV], dtype)
h = T.alloc_fragment([BV, BK], accum_dtype)
h_shared = T.alloc_shared([BV, BK], dtype)
dh = T.alloc_fragment([BK, BV], accum_dtype)
dh_shared = T.alloc_shared([BK, BV], dtype)
T.clear(h)
T.clear(dh)

T.annotate_layout({
ds_shared: tl.layout.make_swizzled_layout(ds_shared),
q: tl.layout.make_swizzled_layout(q),
k: tl.layout.make_swizzled_layout(k),
v: tl.layout.make_swizzled_layout(v),
do: tl.layout.make_swizzled_layout(do),
h_shared: tl.layout.make_swizzled_layout(h_shared),
dh_shared: tl.layout.make_swizzled_layout(dh_shared)
})

# Calculate dQ
for i in T.Pipelined(0, NT, num_stages=1):
T.copy(K[i_b, i * chunk_size:(i + 1) * chunk_size, i_h, i_k * BK:(i_k + 1) * BK], k)
T.copy(V[i_b, i * chunk_size:(i + 1) * chunk_size, i_h, i_v * BV:(i_v + 1) * BV], v)
T.copy(dO[i_b, i * chunk_size:(i + 1) * chunk_size, i_h, i_v * BV:(i_v + 1) * BV],
do)

T.gemm(do, v, ds, transpose_B=True, clear_accum=True)
for row, col in T.Parallel(chunk_size, chunk_size):
ds_shared[row, col] = T.if_then_else(row >= col, ds[row, col], 0)

T.gemm(ds_shared, k, dq, clear_accum=True)
T.copy(h, h_shared)
T.gemm(do, h_shared, dq)
T.gemm(v, k, h, transpose_A=True)
for row, col in T.Parallel(chunk_size, BK):
dq[row, col] *= scale
T.copy(
dq, dQ[i_v, i_b, i * chunk_size:(i + 1) * chunk_size, i_h,
i_k * BK:(i_k + 1) * BK])

# Calculate dK, dV (reversely)
for i in T.Pipelined(1, NT + 1, num_stages=1):
start = NT - i
for row, col in T.Parallel(chunk_size, BK):
q[row, col] = Q[i_b, start * chunk_size + row, i_h, i_k * BK + col] * scale
T.copy(
K[i_b, start * chunk_size:(start + 1) * chunk_size, i_h,
i_k * BK:(i_k + 1) * BK], k)
T.copy(
V[i_b, start * chunk_size:(start + 1) * chunk_size, i_h,
i_v * BV:(i_v + 1) * BV], v)
T.copy(
dO[i_b, start * chunk_size:(start + 1) * chunk_size, i_h,
i_v * BV:(i_v + 1) * BV], do)
T.copy(dh, dh_shared)

# Calculate dk
T.gemm(
v, do, ds, transpose_B=True, clear_accum=True
) # ds here actually means `s`, but we simply reuse the buffer `ds`
for row, col in T.Parallel(chunk_size, chunk_size):
ds_shared[row, col] = T.if_then_else(row <= col, ds[row, col], 0)
T.gemm(ds_shared, q, dk, clear_accum=True)
T.gemm(v, dh_shared, dk, transpose_B=True)

# Calculate dv
T.gemm(k, q, ds, transpose_B=True, clear_accum=True)
for row, col in T.Parallel(chunk_size, chunk_size):
ds_shared[row, col] = T.if_then_else(row <= col, ds[row, col], 0)
T.gemm(ds_shared, do, dv, clear_accum=True)
T.gemm(k, dh_shared, dv)

# Update dh
T.gemm(q, do, dh, transpose_A=True)

T.copy(
dk, dK[i_v, i_b, start * chunk_size:(start + 1) * chunk_size, i_h,
i_k * BK:(i_k + 1) * BK])
T.copy(
dv, dV[i_k, i_b, start * chunk_size:(start + 1) * chunk_size, i_h,
i_v * BV:(i_v + 1) * BV])

return main


def postprocess(dQ, dK, dV):
dQ = dQ[0] if dQ.size(0) == 1 else dQ.sum(0)
dK = dK[0] if dK.size(0) == 1 else dK.sum(0)
dV = dV[0] if dV.size(0) == 1 else dV.sum(0)
return dQ, dK, dV


def main():
parser = argparse.ArgumentParser()
parser.add_argument('--B', type=int, default=8, help='Batch size')
parser.add_argument('--S', type=int, default=2048, help='Seq len')
parser.add_argument('--H', type=int, default=64, help='Num heads')
parser.add_argument('--D', type=int, default=256, help='Head dim')
args = parser.parse_args()
B, S, H, D = args.B, args.S, args.H, args.D

q = torch.randn((B, S, H, D), device='cuda', dtype=torch.float16, requires_grad=True)
k = torch.randn((B, S, H, D), device='cuda', dtype=torch.float16, requires_grad=True)
v = torch.randn((B, S, H, D), device='cuda', dtype=torch.float16, requires_grad=True)
do = torch.randn((B, S, H, D), device='cuda', dtype=torch.float16)

fn = chunk_linear_attn_bwd_kernel(B, S, H, D, D)
kernel = tl.compile(fn, out_idx=[4, 5, 6], target='cuda')
dq, dk, dv = postprocess(*kernel(q, k, v, do))
o_ref, h_ref = fused_chunk_linear_attn(q, k, v, output_final_state=True, normalize=False)
o_ref.backward(do, retain_graph=True)
if torch.allclose(dq, q.grad) and torch.allclose(dk, k.grad) and torch.allclose(dv, v.grad):
print('Passed all tests!✅')
else:
print('Failed some tests!❌')
t1 = do_bench(lambda: o_ref.backward(do, retain_graph=True), warmup=25, rep=100)
q.grad = k.grad = v.grad = None
o_ref, h_ref = fused_chunk_linear_attn(q, k, v, output_final_state=True, normalize=False)
t2 = do_bench(lambda: postprocess(*kernel(q, k, v, do)), warmup=25, rep=100)
print(f'Triton latency: {t1:.3f} ms')
print(f'TileLang latency: {t2:.3f} ms')
print(f'Speedup: {t1/t2:.3f}x')


if __name__ == '__main__':
main()
124 changes: 124 additions & 0 deletions examples/linear_attention/example_linear_attn_fwd.py
Original file line number Diff line number Diff line change
@@ -0,0 +1,124 @@
# Copyright (c) Tile-AI Corporation.
# Licensed under the MIT License.

import torch
import tilelang as tl
import tilelang.language as T
from tilelang.profiler import do_bench

import argparse
from fla.ops.linear_attn import fused_chunk_linear_attn # We compare with FLA


def chunk_linear_attn_fwd_kernel(
B,
S,
H,
DK,
DV,
dtype: str = 'float16',
scale: float = None,
) -> torch.Tensor:

if scale is None:
scale = DK**-0.5
accum_dtype = 'float'

chunk_size = 64
BK = BV = 64
assert S % chunk_size == 0 and DK % BK == 0 and DV % BV == 0
NK = tl.cdiv(DK, BK)
NV = tl.cdiv(DV, BV)
NT = tl.cdiv(S, chunk_size)

@T.prim_func
def main(Q: T.Tensor([B, S, H, DK], dtype), K: T.Tensor([B, S, H, DK], dtype),
V: T.Tensor([B, S, H, DV], dtype), O: T.Tensor([NK, B, S, H, DV], dtype),
final_state: T.Tensor([B, H, DK, DV], accum_dtype)):
with T.Kernel(NV, NK, B * H) as (i_v, i_k, i_bh):
i_b = i_bh // H
i_h = i_bh % H

q = T.alloc_shared([chunk_size, BK], dtype)
k = T.alloc_shared([chunk_size, BK], dtype)
v = T.alloc_shared([chunk_size, BV], dtype)
h = T.alloc_fragment([BK, BV], accum_dtype)
h_shared = T.alloc_shared([BK, BV], dtype)
s = T.alloc_fragment([chunk_size, chunk_size], accum_dtype)
s_shared = T.alloc_shared([chunk_size, chunk_size], dtype)
o = T.alloc_fragment([chunk_size, BV], accum_dtype)
T.clear(h)

T.annotate_layout({
q: tl.layout.make_swizzled_layout(q),
k: tl.layout.make_swizzled_layout(k),
v: tl.layout.make_swizzled_layout(v),
h_shared: tl.layout.make_swizzled_layout(h_shared),
s_shared: tl.layout.make_swizzled_layout(s_shared),
})
T.use_swizzle(8)

for i in T.Pipelined(0, NT, num_stages=1):
for row, col in T.Parallel(chunk_size, BK):
q[row, col] = Q[i_b, i * chunk_size + row, i_h, i_k * BK + col] * scale
T.copy(K[i_b, i * chunk_size:(i + 1) * chunk_size, i_h, i_k * BK:(i_k + 1) * BK], k)
T.copy(V[i_b, i * chunk_size:(i + 1) * chunk_size, i_h, i_v * BV:(i_v + 1) * BV], v)

T.gemm(q, k, s, clear_accum=True, transpose_B=True)
for row, col in T.Parallel(chunk_size, chunk_size):
s_shared[row, col] = T.if_then_else(row >= col, s[row, col], 0)

T.gemm(s_shared, v, o, clear_accum=True)
T.copy(h, h_shared)
T.gemm(q, h_shared, o)
T.gemm(k, v, h, transpose_A=True)
T.copy(
o, O[i_k, i_b, i * chunk_size:(i + 1) * chunk_size, i_h,
i_v * BV:(i_v + 1) * BV])

# Output final state
T.copy(h, final_state[i_b, i_h, i_k * BK:(i_k + 1) * BK, i_v * BV:(i_v + 1) * BV])

return main


def postprocess(o, h):
o = o[0] if o.size(0) == 1 else o.sum(0)
return o, h


def main():
parser = argparse.ArgumentParser()
parser.add_argument('--B', type=int, default=8, help='Batch size')
parser.add_argument('--S', type=int, default=2048, help='Seq len')
parser.add_argument('--H', type=int, default=64, help='Num heads')
parser.add_argument('--D', type=int, default=256, help='Head dim')
args = parser.parse_args()
B, S, H, D = args.B, args.S, args.H, args.D

q = torch.randn((B, S, H, D), device='cuda', dtype=torch.float16)
k = torch.randn((B, S, H, D), device='cuda', dtype=torch.float16)
v = torch.randn((B, S, H, D), device='cuda', dtype=torch.float16)

fn = chunk_linear_attn_fwd_kernel(B, S, H, D, D)
kernel = tl.compile(fn, out_idx=[3, 4], target='cuda')
o, h = postprocess(*kernel(q, k, v))
o_ref, h_ref = fused_chunk_linear_attn(q, k, v, output_final_state=True, normalize=False)

if torch.allclose(o, o_ref) and torch.allclose(h, h_ref):
print('Passed all tests!✅')
else:
print('Failed some tests!❌')

t1 = do_bench(
lambda: fused_chunk_linear_attn(q, k, v, output_final_state=True, normalize=False)[0],
warmup=25,
rep=100)
t2 = do_bench(lambda: kernel(q, k, v)[0].sum(0), warmup=25, rep=100)
print(f'Triton latency: {t1:.3f} ms')
print(f'TileLang latency: {t2:.3f} ms')
print(f'Speedup: {t1/t2:.3f}x')


if __name__ == '__main__':
main()
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