echo / code /flash-linear-attention /fla /ops /ttt /fused_chunk.py
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# Copyright (c) 2023-2025, Songlin Yang, Yu Zhang, Yuqi Pan
import warnings
import torch
import triton
import triton.language as tl
from fla.modules.layernorm import group_norm
from fla.utils import autocast_custom_bwd, autocast_custom_fwd, autotune_cache_kwargs, input_guard, is_nvidia_hopper
NUM_WARPS = [1, 2] if is_nvidia_hopper else [1, 2, 4, 8]
@triton.heuristics({
'USE_INITIAL_STATE': lambda args: args['h0'] is not None,
'USE_INITIAL_STATE_B': lambda args: args['hb0'] is not None,
'STORE_FINAL_STATE': lambda args: args['ht'] is not None,
'IS_VARLEN': lambda args: args['cu_seqlens'] is not None,
})
@triton.autotune(
configs=[
triton.Config({}, num_warps=1),
triton.Config({}, num_warps=2),
triton.Config({}, num_warps=4),
],
key=['BT', 'BK', 'BV'],
**autotune_cache_kwargs,
)
@triton.jit(do_not_specialize=['T'])
def fused_chunk_ttt_linear_fwd_kernel(
q,
k,
v,
eta,
w,
b,
o,
scale,
eps,
h0,
hb0,
ht,
hbt,
cu_seqlens,
T,
H: tl.constexpr,
K: tl.constexpr,
V: tl.constexpr,
BT: tl.constexpr,
BK: tl.constexpr,
BV: tl.constexpr,
USE_INITIAL_STATE: tl.constexpr,
USE_INITIAL_STATE_B: tl.constexpr,
STORE_FINAL_STATE: tl.constexpr,
IS_VARLEN: tl.constexpr,
):
i_nh = tl.program_id(0)
i_n, i_h = i_nh // H, i_nh % H
if IS_VARLEN:
bos, eos = tl.load(cu_seqlens + i_n).to(tl.int32), tl.load(cu_seqlens + i_n + 1).to(tl.int32)
T = eos - bos
NT = tl.cdiv(T, BT)
else:
bos, eos = i_n * T, i_n * T + T
NT = tl.cdiv(T, BT)
o_i = tl.arange(0, BT)
v_i = tl.arange(0, BV)
m_A = o_i[:, None] >= o_i[None, :]
b_w = tl.load(w + i_h * V + v_i, mask=v_i < V, other=0.)
b_b = tl.load(b + i_h * V + v_i, mask=v_i < V, other=0.)
# [BK, BV]
b_h = tl.zeros([BK, BV], dtype=tl.float32)
# [BV]
b_hb = tl.zeros([BV], dtype=tl.float32)
if USE_INITIAL_STATE:
p_h0 = tl.make_block_ptr(h0 + i_nh * K * V, (K, V), (V, 1), (0, 0), (BK, BV), (1, 0))
b_h = tl.load(p_h0, boundary_check=(0, 1), padding_option="zero").to(tl.float32)
if USE_INITIAL_STATE_B:
p_hb0 = tl.make_block_ptr(hb0 + i_nh * V, (V,), (1,), (0,), (BV,), (0,))
b_hb = tl.load(p_hb0, boundary_check=(0,), padding_option="zero").to(tl.float32)
for i_t in range(NT):
p_q = tl.make_block_ptr(q+(bos*H+i_h)*K, (T, K), (H*K, 1), (i_t*BT, 0), (BT, BK), (1, 0))
p_k = tl.make_block_ptr(k+(bos*H+i_h)*K, (K, T), (1, H*K), (0, i_t*BT), (BK, BT), (0, 1))
p_v = tl.make_block_ptr(v+(bos*H+i_h)*V, (T, V), (H*V, 1), (i_t*BT, 0), (BT, BV), (1, 0))
p_o = tl.make_block_ptr(o+(bos*H+i_h)*V, (T, V), (H*V, 1), (i_t*BT, 0), (BT, BV), (1, 0))
p_e = tl.make_block_ptr(eta+(bos*H+i_h), (T,), (H,), (i_t*BT,), (BT,), (0,))
p_e_last = eta+bos*H+i_h + (T-1)*H if i_t == NT-1 else eta+bos*H+i_h + (i_t*BT+BT-1)*H
# [BK, BT]
b_k = tl.load(p_k, boundary_check=(0, 1), padding_option="zero")
# [BT, BV]
b_v = tl.load(p_v, boundary_check=(0, 1), padding_option="zero")
# [BT, BV]
b_kh = tl.dot(tl.trans(b_k), b_h.to(b_k.dtype), allow_tf32=False).to(tl.float32) + b_hb[None, :]
b_kh = tl.where((v_i < V)[None, :], b_kh, 0.)
mean = tl.sum(b_kh, axis=1, keep_dims=True) / V
xbar = tl.where((v_i < V)[None, :], b_kh - mean, 0.)
var = tl.sum(xbar * xbar, axis=1, keep_dims=True) / V
rstd = 1 / tl.sqrt(var.to(tl.float32) + eps)
b_kh_hat = (b_kh - mean) * rstd
b_v = b_kh_hat.to(b_k.dtype) * b_w[None, :].to(b_k.dtype) + \
b_b[None, :].to(b_k.dtype) - b_v.to(b_k.dtype) + tl.trans(b_k)
b_v = tl.where((v_i < V)[None, :], b_v * b_w[None, :].to(b_k.dtype), 0.)
b_v2 = rstd * (V * b_v - tl.sum(b_v, axis=1, keep_dims=True) - b_kh_hat.to(b_k.dtype)
* tl.sum(b_v * b_kh_hat.to(b_k.dtype), axis=1, keep_dims=True)) / V
# [BT, BK]
b_q = tl.load(p_q, boundary_check=(0, 1), padding_option="zero")
# [BT]
b_e = tl.load(p_e, boundary_check=(0,), padding_option="zero")
b_q = (b_q * scale).to(b_k.dtype)
# [BT, BT]
b_A = tl.dot(b_q, b_k, allow_tf32=False)
b_A = tl.where(m_A, b_A, 0)
b_Ae = tl.where(m_A, b_e[:, None], 0.0)
b_o = - tl.dot(b_e[:, None] * b_A.to(b_v2.dtype), b_v2, allow_tf32=False)
b_o += b_hb[None, :] - tl.dot(b_Ae.to(b_v2.dtype), b_v2, allow_tf32=False)
b_o += tl.dot(b_q, b_h.to(b_q.dtype), allow_tf32=False)
b_e_last = tl.load(p_e_last)
b_h = b_h - tl.dot(b_e_last * b_k, b_v2.to(b_k.dtype), allow_tf32=False)
b_hb = b_hb - tl.sum(b_e_last * b_v2.to(b_k.dtype), axis=0)
b_h = tl.where((v_i < V)[None, :], b_h, 0.)
b_hb = tl.where((v_i < V), b_hb, 0.)
tl.store(p_o, b_o.to(p_o.dtype.element_ty), boundary_check=(0, 1))
if STORE_FINAL_STATE:
p_ht = tl.make_block_ptr(ht + i_nh * K*V, (K, V), (V, 1), (0, 0), (BK, BV), (1, 0))
p_hbt = tl.make_block_ptr(hbt + i_nh * V, (V,), (1,), (0,), (BV,), (0,))
tl.store(p_ht, b_h.to(p_ht.dtype.element_ty), boundary_check=(0, 1))
tl.store(p_hbt, b_hb.to(p_hbt.dtype.element_ty), boundary_check=(0,))
@triton.heuristics({
'USE_INITIAL_STATE': lambda args: args['h0'] is not None,
'USE_INITIAL_STATE_B': lambda args: args['hb0'] is not None,
})
@triton.autotune(
configs=[
triton.Config({}, num_warps=1),
triton.Config({}, num_warps=2),
triton.Config({}, num_warps=4),
],
key=['BT', 'BK', 'BV'],
**autotune_cache_kwargs,
)
@triton.jit(do_not_specialize=['T'])
def fused_chunk_ttt_linear_bwd_kernel_h(
k,
v,
v2,
x,
y,
r,
w,
b,
eta,
h0,
hb0,
h,
do,
dq,
scale,
eps,
T,
H: tl.constexpr,
K: tl.constexpr,
V: tl.constexpr,
BT: tl.constexpr,
BK: tl.constexpr,
BV: tl.constexpr,
USE_INITIAL_STATE: tl.constexpr,
USE_INITIAL_STATE_B: tl.constexpr,
):
i_nh = tl.program_id(0)
i_n, i_h = i_nh // H, i_nh % H
bos, _ = i_n * T, i_n * T + T
NT = tl.cdiv(T, BT)
boh = i_n * NT
o_i = tl.arange(0, BT)
v_i = tl.arange(0, BV)
m_A = o_i[:, None] >= o_i[None, :]
b_w = tl.load(w + i_h * V + v_i, mask=v_i < V, other=0.)
b_b = tl.load(b + i_h * V + v_i, mask=v_i < V, other=0.)
# [BK, BV]
b_h = tl.zeros([BK, BV], dtype=tl.float32)
# [BV]
b_hb = tl.zeros([BV], dtype=tl.float32)
if USE_INITIAL_STATE:
p_h0 = tl.make_block_ptr(h0 + i_nh * K * V, (K, V), (V, 1), (0, 0), (BK, BV), (1, 0))
b_h = tl.load(p_h0, boundary_check=(0, 1), padding_option="zero").to(tl.float32)
if USE_INITIAL_STATE_B:
p_hb0 = tl.make_block_ptr(hb0 + i_nh * V, (V,), (1,), (0,), (BV,), (0,))
b_hb = tl.load(p_hb0, boundary_check=(0,), padding_option="zero").to(tl.float32)
for i_t in range(NT):
p_h = tl.make_block_ptr(h+((boh+i_t)*H+i_h)*K*V, (K, V), (V, 1), (0, 0), (BK, BV), (1, 0))
p_k = tl.make_block_ptr(k+(bos*H+i_h)*K, (K, T), (1, H*K), (0, i_t*BT), (BK, BT), (0, 1))
p_v = tl.make_block_ptr(v+(bos*H+i_h)*V, (T, V), (H*V, 1), (i_t*BT, 0), (BT, BV), (1, 0))
p_v2 = tl.make_block_ptr(v2+(bos*H+i_h)*V, (T, V), (H*V, 1), (i_t*BT, 0), (BT, BV), (1, 0))
p_x = tl.make_block_ptr(x+(bos*H+i_h)*V, (T, V), (H*V, 1), (i_t*BT, 0), (BT, BV), (1, 0))
p_y = tl.make_block_ptr(y+(bos*H+i_h)*V, (T, V), (H*V, 1), (i_t*BT, 0), (BT, BV), (1, 0))
p_r = tl.make_block_ptr(r+bos*H+i_h, (T, 1), (H, 1), (i_t*BT, 0), (BT, 1), (1, 0))
p_e = tl.make_block_ptr(eta+(bos*H+i_h), (T,), (H,), (i_t*BT,), (BT,), (0,))
p_dq = tl.make_block_ptr(dq+(bos*H+i_h)*K, (T, K), (H*K, 1), (i_t*BT, 0), (BT, BK), (1, 0))
p_do = tl.make_block_ptr(do+(bos*H+i_h)*V, (T, V), (H*V, 1), (i_t*BT, 0), (BT, BV), (1, 0))
p_e_last = eta+bos*H+i_h + (T-1)*H if i_t == NT-1 else eta+bos*H+i_h + (i_t*BT+BT-1)*H
tl.store(p_h, b_h.to(p_h.dtype.element_ty), boundary_check=(0, 1))
# [BK, BT]
b_k = tl.load(p_k, boundary_check=(0, 1), padding_option="zero")
# [BT, BV]
b_v = tl.load(p_v, boundary_check=(0, 1), padding_option="zero")
b_kh = tl.dot(tl.trans(b_k), b_h.to(b_k.dtype), allow_tf32=False).to(tl.float32) + b_hb[None, :]
b_kh = tl.where((v_i < V)[None, :], b_kh, 0.)
mean = tl.sum(b_kh, axis=1, keep_dims=True) / V
xbar = tl.where((v_i < V)[None, :], b_kh - mean, 0.)
var = tl.sum(xbar * xbar, axis=1, keep_dims=True) / V
rstd = 1 / tl.sqrt(var.to(tl.float32) + eps)
b_kh_hat = (b_kh - mean) * rstd
b_v = b_kh_hat.to(b_k.dtype) * b_w[None, :].to(b_k.dtype) + \
b_b[None, :].to(b_k.dtype) - b_v.to(b_k.dtype) + tl.trans(b_k)
b_v = tl.where((v_i < V)[None, :], b_v * b_w[None, :].to(b_k.dtype), 0.)
b_v2 = rstd * (V * b_v - tl.sum(b_v, axis=1, keep_dims=True) - b_kh_hat.to(b_k.dtype)
* tl.sum(b_v * b_kh_hat.to(b_k.dtype), axis=1, keep_dims=True)) / V
tl.store(p_x, b_kh_hat.to(p_x.dtype.element_ty), boundary_check=(0, 1))
tl.store(p_y, b_v.to(p_y.dtype.element_ty), boundary_check=(0, 1))
tl.store(p_r, rstd.to(p_r.dtype.element_ty), boundary_check=(0, 1))
tl.store(p_v2, b_v2.to(p_v2.dtype.element_ty), boundary_check=(0, 1))
b_e = tl.load(p_e, boundary_check=(0,), padding_option="zero")
b_do = tl.load(p_do, boundary_check=(0, 1), padding_option="zero")
b_v2 = tl.where((v_i < V)[None, :], b_v2, 0.)
b_ds = tl.dot(b_do, tl.trans(b_v2).to(b_do.dtype))
b_ds = tl.where(m_A, b_ds, 0)
b_ds = b_ds.to(b_k.dtype)
b_dq = tl.dot(b_do, tl.trans(b_h).to(b_do.dtype))
b_dq -= tl.dot(b_ds, tl.trans(b_k)) * b_e[:, None]
b_dq *= scale
b_e_last = tl.load(p_e_last)
b_h = b_h - tl.dot(b_e_last * b_k, b_v2.to(b_k.dtype), allow_tf32=False)
b_hb = b_hb - tl.sum(b_e_last * b_v2.to(b_k.dtype), axis=0)
b_h = tl.where((v_i < V)[None, :], b_h, 0.)
b_hb = tl.where((v_i < V), b_hb, 0.)
tl.store(p_dq, b_dq.to(p_dq.dtype.element_ty), boundary_check=(0, 1))
@triton.heuristics({
'USE_INITIAL_STATE': lambda args: args['dh0'] is not None,
'USE_INITIAL_STATE_B': lambda args: args['dhb0'] is not None,
'USE_FINAL_STATE_GRADIENT': lambda args: args['dht'] is not None,
'USE_FINAL_STATE_GRADIENT_B': lambda args: args['dhbt'] is not None,
})
@triton.autotune(
configs=[
triton.Config({}, num_warps=num_warps)
for num_warps in NUM_WARPS
],
key=['BT', 'BK', 'BV'],
**autotune_cache_kwargs,
)
@triton.jit(do_not_specialize=['T'])
def fused_chunk_ttt_linear_bwd_kernel_dh(
q,
k,
v,
v2,
x,
y,
r,
w,
b,
eta,
h,
dht,
dhbt,
dh0,
dhb0,
do,
dk,
dv,
de,
dw,
db,
scale,
T,
H: tl.constexpr,
K: tl.constexpr,
V: tl.constexpr,
BT: tl.constexpr,
BK: tl.constexpr,
BV: tl.constexpr,
USE_INITIAL_STATE: tl.constexpr,
USE_INITIAL_STATE_B: tl.constexpr,
USE_FINAL_STATE_GRADIENT: tl.constexpr,
USE_FINAL_STATE_GRADIENT_B: tl.constexpr,
):
i_nh = tl.program_id(0)
i_n, i_h = i_nh // H, i_nh % H
bos, _ = i_n * T, i_n * T + T
NT = tl.cdiv(T, BT)
boh = i_n * NT
# [BK, BV]
b_dh = tl.zeros([BK, BV], dtype=tl.float32)
# [BV]
b_dhb = tl.zeros([BV], dtype=tl.float32)
if USE_FINAL_STATE_GRADIENT:
p_dht = tl.make_block_ptr(dht + i_nh * K*V, (K, V), (V, 1), (0, 0), (BK, BV), (1, 0))
b_dh += tl.load(p_dht, boundary_check=(0, 1), padding_option="zero")
if USE_FINAL_STATE_GRADIENT_B:
p_dhbt = tl.make_block_ptr(dhbt + i_nh * V, (V,), (1,), (0,), (BV,), (0,))
b_dhb += tl.load(p_dhbt, boundary_check=(0,), padding_option="zero")
# [BV]
o_i = tl.arange(0, BT)
v_i = tl.arange(0, BV)
m_A = o_i[:, None] >= o_i[None, :]
m_A_t = o_i[:, None] <= o_i[None, :]
b_w = tl.load(w + i_h * V + v_i, mask=v_i < V, other=0.)
b_b = tl.load(b + i_h * V + v_i, mask=v_i < V, other=0.)
b_dw = tl.zeros([BV], dtype=b_w.dtype)
b_db = tl.zeros([BV], dtype=b_b.dtype)
p_dw = tl.make_block_ptr(dw + i_nh * V, (V,), (1,), (0,), (BV,), (0,))
p_db = tl.make_block_ptr(db + i_nh * V, (V,), (1,), (0,), (BV,), (0,))
for i_t in range(NT - 1, -1, -1):
p_h = tl.make_block_ptr(h+((boh+i_t)*H+i_h)*K*V, (V, K), (1, V), (0, 0), (BV, BK), (0, 1))
p_q = tl.make_block_ptr(q+(bos*H+i_h)*K, (K, T), (1, H*K), (0, i_t*BT), (BK, BT), (0, 1))
p_k = tl.make_block_ptr(k+(bos*H+i_h)*K, (T, K), (H*K, 1), (i_t*BT, 0), (BT, BK), (1, 0))
p_v = tl.make_block_ptr(v+(bos*H+i_h)*V, (T, V), (H*V, 1), (i_t*BT, 0), (BT, BV), (1, 0))
p_v2 = tl.make_block_ptr(v2+(bos*H+i_h)*V, (T, V), (H*V, 1), (i_t*BT, 0), (BT, BV), (1, 0))
p_x = tl.make_block_ptr(x+(bos*H+i_h)*V, (T, V), (H*V, 1), (i_t*BT, 0), (BT, BV), (1, 0))
p_y = tl.make_block_ptr(y+(bos*H+i_h)*V, (T, V), (H*V, 1), (i_t*BT, 0), (BT, BV), (1, 0))
p_r = tl.make_block_ptr(r+bos*H+i_h, (T, 1), (H, 1), (i_t*BT, 0), (BT, 1), (1, 0))
p_e = tl.make_block_ptr(eta+(bos*H+i_h), (T,), (H,), (i_t*BT,), (BT,), (0,))
p_dv = tl.make_block_ptr(dv+(bos*H+i_h)*V, (T, V), (H*V, 1), (i_t*BT, 0), (BT, BV), (1, 0))
p_dk = tl.make_block_ptr(dk+(bos*H+i_h)*K, (T, K), (H*K, 1), (i_t*BT, 0), (BT, BK), (1, 0))
p_do = tl.make_block_ptr(do+(bos*H+i_h)*V, (T, V), (H*V, 1), (i_t*BT, 0), (BT, BV), (1, 0))
p_de = tl.make_block_ptr(de+(bos*H+i_h), (T,), (H,), (i_t*BT,), (BT,), (0,))
p_e_last = eta+bos*H+i_h + (T-1)*H if i_t == NT-1 else eta+bos*H+i_h + (i_t*BT+BT-1)*H
b_q = tl.load(p_q, boundary_check=(0, 1), padding_option="zero")
b_k = tl.load(p_k, boundary_check=(0, 1), padding_option="zero")
b_e = tl.load(p_e, boundary_check=(0,), padding_option="zero")
b_do = tl.load(p_do, boundary_check=(0, 1), padding_option="zero")
b_e_last = tl.load(p_e_last)
b_A = tl.dot(b_k, b_q)
b_A = - tl.where(m_A_t, b_A * scale * b_e[None, :], 0).to(do.dtype.element_ty)
b_Ae = - tl.where(m_A_t, b_e[None, :], 0).to(do.dtype.element_ty)
b_dv_new = tl.dot(b_A.to(b_do.dtype), b_do) + tl.dot(b_Ae.to(b_do.dtype), b_do)
b_dv_new -= tl.dot(b_e_last * b_k, b_dh.to(b_k.dtype))
b_dv_new -= b_e_last * b_dhb.to(b_k.dtype)[None, :]
b_v2 = tl.load(p_v2, boundary_check=(0, 1), padding_option="zero").to(b_k.dtype)
b_x = tl.load(p_x, boundary_check=(0, 1), padding_option="zero").to(b_k.dtype)
b_y = tl.load(p_y, boundary_check=(0, 1), padding_option="zero").to(b_k.dtype)
b_rstd = tl.load(p_r, boundary_check=(0, 1), padding_option="zero").to(tl.float32)
b_dy = b_rstd * (b_dv_new * V - tl.sum(b_dv_new, axis=1, keep_dims=True) -
b_x * tl.sum(b_dv_new * b_x, axis=1, keep_dims=True)) / V
b_dx = -b_rstd * (b_dv_new * tl.sum(b_x * b_y, axis=1, keep_dims=True) +
b_y * tl.sum(b_dv_new * b_x, axis=1, keep_dims=True)) / V
b_drstd = tl.sum(b_dv_new.to(b_rstd.dtype) * b_v2.to(b_rstd.dtype) / b_rstd, axis=1, keep_dims=True)
b_v = tl.load(p_v, boundary_check=(0, 1), padding_option="zero")
b_w = b_w.to(b_k.dtype)
b_b = b_b.to(b_k.dtype)
b_dv = -b_w * b_dy.to(b_k.dtype)
b_dk = b_w * b_dy.to(b_k.dtype)
b_dw += tl.sum(2 * b_w * b_x * b_dy.to(b_k.dtype) +
(b_b - b_v.to(b_k.dtype) + b_k) * b_dy.to(b_k.dtype), axis=0).to(b_dw.dtype)
b_db += tl.sum(b_w * b_dy.to(b_k.dtype), axis=0).to(b_db.dtype)
b_dx = b_dx.to(b_k.dtype) + b_w * b_w * b_dy.to(b_k.dtype)
b_h = tl.load(p_h, boundary_check=(0, 1), padding_option="zero")
b_q = (b_q * scale).to(b_q.dtype)
b_dkh = b_rstd * (V * b_dx - tl.sum(b_dx, axis=1, keep_dims=True) -
b_x * tl.sum(b_x * b_dx, axis=1, keep_dims=True)) / V
b_dkh -= b_rstd * b_rstd * b_drstd * b_x / V
b_dkh = tl.where((v_i < V)[None, :] * (o_i < T-i_t*BT)[:, None], b_dkh, 0.)
b_dk += tl.dot(b_dkh, b_h.to(b_dkh.dtype)).to(b_k.dtype)
b_ds = tl.dot(b_do, tl.trans(b_v2))
b_ds = tl.where(m_A, b_ds, 0)
b_ds = b_ds.to(b_k.dtype)
i_last = (BT-1) if (i_t*BT+BT) <= T else (T % BT-1)
mask = (o_i == i_last)
b_dk -= b_e_last * tl.dot(b_v2, tl.trans(b_dh).to(b_v2.dtype))
b_dk -= tl.dot(tl.trans(b_ds), tl.trans(b_q) * b_e[:, None])
b_de = mask * tl.sum(- b_dh * tl.trans(tl.dot(tl.trans(b_v2), b_k))).to(b_k.dtype)
b_de -= mask * tl.sum(b_dhb * tl.sum(b_v2, axis=0)).to(b_k.dtype)
b_de -= tl.sum(tl.dot(b_ds, b_k) * tl.trans(b_q).to(b_k.dtype), axis=1)
b_de -= tl.sum(b_ds, axis=1)
b_dh += tl.dot(b_q, b_do.to(b_q.dtype)) + tl.dot(tl.trans(b_k).to(b_dkh.dtype), b_dkh)
b_dhb += tl.sum(b_do + b_dkh, axis=0)
b_dh = tl.where((v_i < V)[None, :], b_dh, 0.)
b_dhb = tl.where((v_i < V), b_dhb, 0.)
tl.store(p_dk, b_dk.to(p_dk.dtype.element_ty), boundary_check=(0, 1))
tl.store(p_dv, b_dv.to(p_dv.dtype.element_ty), boundary_check=(0, 1))
tl.store(p_de, b_de.to(p_de.dtype.element_ty), boundary_check=(0,))
tl.store(p_dw, b_dw.to(p_dw.dtype.element_ty), boundary_check=(0,))
tl.store(p_db, b_db.to(p_db.dtype.element_ty), boundary_check=(0,))
if USE_INITIAL_STATE:
p_dh0 = tl.make_block_ptr(dh0+i_nh*K*V, (K, V), (V, 1), (0, 0), (BK, BV), (1, 0))
tl.store(p_dh0, b_dh.to(p_dh0.dtype.element_ty), boundary_check=(0, 1))
if USE_INITIAL_STATE_B:
p_dhb0 = tl.make_block_ptr(dhb0+i_nh*V, (V,), (1,), (0,), (BV,), (0,))
tl.store(p_dhb0, b_dhb.to(p_dhb0.dtype.element_ty), boundary_check=(0,))
def fused_chunk_ttt_linear_bwd_h(
q: torch.Tensor,
k: torch.Tensor,
v: torch.Tensor,
w: torch.Tensor,
b: torch.Tensor,
eta: torch.Tensor,
scale: float,
eps: float,
do: torch.Tensor,
BT: int = 16,
initial_state: torch.Tensor = None,
initial_state_bias: torch.Tensor = None,
cu_seqlens: torch.LongTensor | None = None,
):
assert cu_seqlens is None, "bwd of varlen is not implemented yet."
B, T, H, K, V = *k.shape, v.shape[-1]
# N: the actual number of sequences in the batch with either equal or variable lengths
N, NT = B, triton.cdiv(T, BT)
BK, BV = max(triton.next_power_of_2(K), 16), max(triton.next_power_of_2(V), 16)
assert max(BK, BV) <= 128, "current kernel does not support head dimension larger than 128."
h = k.new_empty(B, NT, H, K, V)
r = v.new_empty(B, T, H, 1, dtype=torch.float32)
v2 = torch.empty_like(v)
x = torch.empty_like(v)
y = torch.empty_like(v)
dq = torch.empty_like(q)
grid = (N * H,)
fused_chunk_ttt_linear_bwd_kernel_h[grid](
k=k,
v=v,
v2=v2,
x=x,
y=y,
r=r,
w=w,
b=b,
eta=eta,
h0=initial_state,
hb0=initial_state_bias,
h=h,
do=do,
dq=dq,
scale=scale,
eps=eps,
T=T,
H=H,
K=K,
V=V,
BT=BT,
BK=BK,
BV=BV,
)
return dq, h, v2, x, y, r
def fused_chunk_ttt_linear_bwd_dh(
q: torch.Tensor,
k: torch.Tensor,
v: torch.Tensor,
v2: torch.Tensor,
x: torch.Tensor,
y: torch.Tensor,
r: torch.Tensor,
w: torch.Tensor,
b: torch.Tensor,
eta: torch.Tensor,
scale: float,
h: torch.Tensor,
do: torch.Tensor,
dht: torch.Tensor,
dhbt: torch.Tensor,
BT: int = 16,
initial_state: torch.Tensor = None,
initial_state_bias: torch.Tensor = None,
cu_seqlens: torch.LongTensor | None = None,
):
assert cu_seqlens is None, "bwd of varlen is not implemented yet."
B, T, H, K, V = *k.shape, v.shape[-1]
# N: the actual number of sequences in the batch with either equal or variable lengths
N = B
BK, BV = max(triton.next_power_of_2(K), 16), max(triton.next_power_of_2(V), 16)
assert max(BK, BV) <= 128, "current kernel does not support head dimension larger than 128."
dh0 = torch.empty_like(initial_state, dtype=torch.float32) if initial_state is not None else None
dhb0 = torch.empty_like(initial_state_bias, dtype=torch.float32) if initial_state_bias is not None else None
dk = torch.empty_like(k)
dv = torch.empty_like(v)
de = torch.empty_like(eta)
dw = w.new_empty(B, H, V)
db = b.new_empty(B, H, V)
grid = (N * H,)
fused_chunk_ttt_linear_bwd_kernel_dh[grid](
q=q,
k=k,
v=v,
v2=v2,
x=x,
y=y,
r=r,
w=w,
b=b,
eta=eta,
h=h,
dht=dht,
dhbt=dhbt,
dh0=dh0,
dhb0=dhb0,
do=do,
dk=dk,
dv=dv,
de=de,
dw=dw,
db=db,
scale=scale,
T=T,
H=H,
K=K,
V=V,
BT=BT,
BK=BK,
BV=BV,
)
dw = dw.sum(dim=0)
db = db.sum(dim=0)
return dk, dv, de, dw, db, dh0, dhb0
def fused_chunk_ttt_linear_fwd(
q: torch.Tensor,
k: torch.Tensor,
v: torch.Tensor,
w: torch.Tensor,
b: torch.Tensor,
eta: torch.Tensor,
scale: float,
eps: float,
initial_state: torch.Tensor,
initial_state_bias: torch.Tensor,
output_final_state: bool,
cu_seqlens: torch.LongTensor | None = None,
BT: int = 16,
):
B, T, H, K, V = *k.shape, v.shape[-1]
# N: the actual number of sequences in the batch with either equal or variable lengths
N = B if cu_seqlens is None else len(cu_seqlens) - 1
BK, BV = max(triton.next_power_of_2(K), 16), max(triton.next_power_of_2(V), 16)
assert max(BK, BV) <= 128, "current kernel does not support head dimension larger than 128."
o = torch.empty_like(v)
final_state = k.new_empty(N, H, K, V, dtype=torch.float32) if output_final_state else None
final_state_bias = k.new_empty(N, H, 1, V, dtype=torch.float32) if output_final_state else None
grid = (N * H,)
fused_chunk_ttt_linear_fwd_kernel[grid](
q=q,
k=k,
v=v,
eta=eta,
w=w,
b=b,
o=o,
scale=scale,
eps=eps,
h0=initial_state,
hb0=initial_state_bias,
ht=final_state,
hbt=final_state_bias,
cu_seqlens=cu_seqlens,
T=T,
H=H,
K=K,
V=V,
BT=BT,
BK=BK,
BV=BV,
)
return o, final_state, final_state_bias
def fused_chunk_ttt_linear_bwd(
q: torch.Tensor,
k: torch.Tensor,
v: torch.Tensor,
w: torch.Tensor,
b: torch.Tensor,
eta: torch.Tensor,
scale: float,
eps: float,
do: torch.Tensor,
dht: torch.Tensor,
dhbt: torch.Tensor,
BT: int = 16,
initial_state: torch.Tensor = None,
initial_state_bias: torch.Tensor = None,
cu_seqlens: torch.LongTensor | None = None,
):
assert cu_seqlens is None, "bwd of varlen is not implemented yet."
dq, h, v2, x, y, rstd = fused_chunk_ttt_linear_bwd_h(
q=q,
k=k,
v=v,
w=w,
b=b,
eta=eta,
scale=scale,
eps=eps,
do=do,
BT=BT,
initial_state=initial_state,
initial_state_bias=initial_state_bias,
cu_seqlens=cu_seqlens,
)
dk, dv, de, dw, db, dh0, dhb0 = fused_chunk_ttt_linear_bwd_dh(
q=q,
k=k,
v=v,
v2=v2,
x=x,
y=y,
r=rstd,
w=w,
b=b,
eta=eta,
scale=scale,
h=h,
do=do,
dht=dht,
dhbt=dhbt,
BT=BT,
initial_state=initial_state,
initial_state_bias=initial_state_bias,
cu_seqlens=cu_seqlens,
)
return dq, dk, dv, de, dw, db, dh0, dhb0
class FusedChunkTTTLinearFunction(torch.autograd.Function):
@staticmethod
@input_guard
@autocast_custom_fwd
def forward(ctx, q, k, v, w, b, BT, eta, scale, eps, initial_state,
initial_state_bias, output_final_state, cu_seqlens):
o, final_state, final_state_bias = fused_chunk_ttt_linear_fwd(
q=q,
k=k,
v=v,
w=w,
b=b,
eta=eta,
scale=scale,
eps=eps,
BT=BT,
initial_state=initial_state,
initial_state_bias=initial_state_bias,
output_final_state=output_final_state,
cu_seqlens=cu_seqlens,
)
ctx.save_for_backward(q, k, v, eta, w, b, initial_state, initial_state_bias)
ctx.BT = BT
ctx.scale = scale
ctx.eps = eps
ctx.cu_seqlens = cu_seqlens
return o.to(q.dtype), final_state, final_state_bias
@staticmethod
@input_guard
@autocast_custom_bwd
def backward(ctx, do, dht, dhbt):
q, k, v, eta, w, b, initial_state, initial_state_bias = ctx.saved_tensors
dq, dk, dv, de, dw, db, dh0, dhb0 = fused_chunk_ttt_linear_bwd(
q=q,
k=k,
v=v,
w=w,
b=b,
eta=eta,
scale=ctx.scale,
eps=ctx.eps,
do=do,
dht=dht,
dhbt=dhbt,
BT=ctx.BT,
initial_state=initial_state,
initial_state_bias=initial_state_bias,
cu_seqlens=ctx.cu_seqlens,
)
return dq.to(q), dk.to(k), dv.to(v), dw.to(w), db.to(b), None, de.to(eta), None, None, dh0, dhb0, None, None
def norm_residual(x, weight, bias, eps):
# GroupNorm and Residual
B, T, H, D = x.shape
x += group_norm(
x.reshape(B, T, -1).clone(),
weight=weight.reshape(-1).clone(),
bias=bias.reshape(-1).clone(),
eps=eps,
num_groups=H,
).reshape(x.shape)
return x
def fused_chunk_ttt_linear(
q: torch.Tensor,
k: torch.Tensor,
v: torch.Tensor,
w: torch.Tensor,
b: torch.Tensor,
eta: torch.Tensor,
scale: float = None,
eps: float = 1e-6,
chunk_size: int = 16,
initial_state: torch.Tensor = None,
initial_state_bias: torch.Tensor = None,
output_final_state: bool = False,
cu_seqlens: torch.LongTensor | None = None,
head_first: bool = False,
):
r"""
Args:
q (torch.Tensor):
queries of shape `(B, H, T, K)`
k (torch.Tensor):
keys of shape `(B, H, T, K)`
v (torch.Tensor):
values of shape `(B, H, T, V)`
w (torch.Tensor):
layer norm weight of shape `(H, V)`
b (torch.Tensor):
layer norm bias of shape `(H, V)`
eta (torch.Tensor):
Learning rate for hidden state, of shape `(B, H, T, 1)`.
scale (Optional[float]):
Scale factor for the RetNet attention scores.
If not provided, it will default to `1 / sqrt(K)`. Default: `None`.
chunk_size (int):
chunk size. Default: `16`.
initial_state (Optional[torch.Tensor]):
Initial state of shape `(B, H, K, V)`. Default: `None`.
initial_state_bias (Optional[torch.Tensor]):
Initial state bias of shape `(B, H, 1, V)`. Default: `None`.
output_final_state (Optional[bool]):
Whether to output the final state of shape `(B, H, 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.
head_first (Optional[bool]):
Whether the inputs are in the head-first format. Default: `False`.
This argument has been deprecated.
Returns:
o (torch.Tensor):
Outputs of shape `[B, H, T, V]`
final_state (torch.Tensor):
Final state of shape `[B, H, K, V]` if `output_final_state=True` else `None`.
final_state_bias (torch.Tensor):
Final state bias of shape `[B, H, 1, V]` if `output_final_state=True` else `None`.
"""
assert q.dtype == k.dtype == v.dtype
assert k.shape[-1] == v.shape[-1], "DK must equal to DV."
if isinstance(eta, float):
eta = torch.full_like(q[:, :, :, :1], eta)
if head_first:
raise DeprecationWarning(
"head_first is deprecated and will be removed in a future version. "
"Please use head_first=False for now instead.",
)
if not head_first and q.shape[1] < q.shape[2]:
warnings.warn(
f"Input tensor shape suggests potential format mismatch: seq_len ({q.shape[1]}) < num_heads ({q.shape[2]}). "
"This may indicate the inputs were passed in head-first format [B, H, T, ...] "
"when head_first=False was specified. "
"Please verify your input tensor format matches the expected shape [B, T, H, ...].",
)
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."
o, final_state, final_state_bias = FusedChunkTTTLinearFunction.apply(
q,
k,
v,
w,
b,
chunk_size,
eta,
scale,
eps,
initial_state,
initial_state_bias,
output_final_state,
cu_seqlens,
)
o = norm_residual(o, w, b, eps)
return o, final_state, final_state_bias