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[Deltaformer] kernel improvement; if-else optimization; change w to fp32; add 1e-9 to avoid nan #603

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[Deltaformer] kernel improvement; if-else optimization; change w to fp32; add 1e-9 to avoid nan #603

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56 changes: 38 additions & 18 deletions fla/ops/deltaformer/parallel.py
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Original file line number Diff line number Diff line change
Expand Up @@ -167,7 +167,7 @@ def parallel_deltaformer_fwd_kernel(
)
q = tl.load(q_blk_ptr, boundary_check=(0,))

for kv_i in range(0, T, BLOCK_T):
for kv_i in range(0, T-C, BLOCK_T):
k_blk_ptr = tl.make_block_ptr(
base=k_ptr + pid_h * D,
shape=(D, T),
Expand All @@ -179,10 +179,6 @@ def parallel_deltaformer_fwd_kernel(
k = tl.load(k_blk_ptr, boundary_check=(1,))
qk = tl.dot(q, k) * qk_scale

if kv_i >= T - C:
mask = (T - C - kv_i + rowid_block[:, None] - colid_block[None, :] < 1)
qk = tl.where(mask, -1e6, qk)

rowmax_i = tl.maximum(rowmax, tl.max(qk, axis=1))
qk -= rowmax_i[:, None]
p = tl.math.exp2(qk)
Expand All @@ -193,17 +189,41 @@ def parallel_deltaformer_fwd_kernel(
acc = acc * alpha[:, None]
rowmax = rowmax_i

if kv_i < T - C:
u_blk_ptr = tl.make_block_ptr(
base=u_ptr + pid_h * D,
shape=(T, D),
strides=(H * D, 1),
offsets=(kv_i, 0),
block_shape=(BLOCK_T, D),
order=(1, 0),
)
u = tl.load(u_blk_ptr, boundary_check=(0,))
acc = tl.dot(p.to(u_ptr.dtype.element_ty), u, acc)
u_blk_ptr = tl.make_block_ptr(
base=u_ptr + pid_h * D,
shape=(T, D),
strides=(H * D, 1),
offsets=(kv_i, 0),
block_shape=(BLOCK_T, D),
order=(1, 0),
)
u = tl.load(u_blk_ptr, boundary_check=(0,))
acc = tl.dot(p.to(u_ptr.dtype.element_ty), u, acc)

for kv_i in range(T-C, T, BLOCK_T):
k_blk_ptr = tl.make_block_ptr(
base=k_ptr + pid_h * D,
shape=(D, T),
strides=(1, H * D),
offsets=(0, kv_i),
block_shape=(D, BLOCK_T),
order=(0, 1),
)
k = tl.load(k_blk_ptr, boundary_check=(1,))
qk = tl.dot(q, k) * qk_scale

mask = (T - C - kv_i + rowid_block[:, None] - colid_block[None, :] < 1)
qk = tl.where(mask, -1e6, qk)

rowmax_i = tl.maximum(rowmax, tl.max(qk, axis=1))
qk -= rowmax_i[:, None]
p = tl.math.exp2(qk)

rowsum_i = tl.sum(p, axis=1)
alpha = tl.math.exp2(rowmax - rowmax_i)
rowsum = rowsum * alpha + rowsum_i
acc = acc * alpha[:, None]
rowmax = rowmax_i

lse = rowmax + tl.math.log2(rowsum)
lse_block_ptr = lse_ptr + pid_h + rowid_block * H
Expand All @@ -218,7 +238,7 @@ def parallel_deltaformer_fwd_kernel(
block_shape=(BLOCK_C, D),
order=(1, 0),
)
acc = acc / rowsum[:, None]
acc = acc / (rowsum[:, None] + 1e-9)

beta_ptr = tl.make_block_ptr(
base=beta_ptr + pid_h,
Expand Down Expand Up @@ -861,7 +881,7 @@ def _forward_impl(
betai = beta_full[b, i:i + Ci, :]

w, lse_chunk = parallel_deltaformer_chunk_fwd(qi, ki, vi, ui_prev, fa_scale, betai)
w = w * betai.unsqueeze(-1)
w = w * betai.unsqueeze(-1).to(torch.float32)
if need_aux:
wpad = torch.zeros(C, H, C, device=ko.device, dtype=ko.dtype)
wpad[:Ci, :, :Ci].copy_(w)
Expand Down
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