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from typing import Optional
from einops import rearrange
import torch
import torch.nn as nn
from .activation_layers import get_activation_layer
from .attenion import attention
from .norm_layers import get_norm_layer
from .embed_layers import TimestepEmbedder, TextProjection
from .attenion import attention
from .mlp_layers import MLP
from .modulate_layers import modulate, apply_gate
class IndividualTokenRefinerBlock(nn.Module):
def __init__(
self,
hidden_size,
heads_num,
mlp_width_ratio: str = 4.0,
mlp_drop_rate: float = 0.0,
act_type: str = "silu",
qk_norm: bool = False,
qk_norm_type: str = "layer",
qkv_bias: bool = True,
dtype: Optional[torch.dtype] = None,
device: Optional[torch.device] = None,
):
factory_kwargs = {"device": device, "dtype": dtype}
super().__init__()
self.heads_num = heads_num
head_dim = hidden_size // heads_num
mlp_hidden_dim = int(hidden_size * mlp_width_ratio)
self.norm1 = nn.LayerNorm(
hidden_size, elementwise_affine=True, eps=1e-6, **factory_kwargs
)
self.self_attn_qkv = nn.Linear(
hidden_size, hidden_size * 3, bias=qkv_bias, **factory_kwargs
)
qk_norm_layer = get_norm_layer(qk_norm_type)
self.self_attn_q_norm = (
qk_norm_layer(head_dim, elementwise_affine=True, eps=1e-6, **factory_kwargs)
if qk_norm
else nn.Identity()
)
self.self_attn_k_norm = (
qk_norm_layer(head_dim, elementwise_affine=True, eps=1e-6, **factory_kwargs)
if qk_norm
else nn.Identity()
)
self.self_attn_proj = nn.Linear(
hidden_size, hidden_size, bias=qkv_bias, **factory_kwargs
)
self.norm2 = nn.LayerNorm(
hidden_size, elementwise_affine=True, eps=1e-6, **factory_kwargs
)
act_layer = get_activation_layer(act_type)
self.mlp = MLP(
in_channels=hidden_size,
hidden_channels=mlp_hidden_dim,
act_layer=act_layer,
drop=mlp_drop_rate,
**factory_kwargs,
)
self.adaLN_modulation = nn.Sequential(
act_layer(),
nn.Linear(hidden_size, 2 * hidden_size, bias=True, **factory_kwargs),
)
# Zero-initialize the modulation
nn.init.zeros_(self.adaLN_modulation[1].weight)
nn.init.zeros_(self.adaLN_modulation[1].bias)
def forward(
self,
x: torch.Tensor,
c: torch.Tensor, # timestep_aware_representations + context_aware_representations
attn_mask: torch.Tensor = None,
):
gate_msa, gate_mlp = self.adaLN_modulation(c).chunk(2, dim=1)
norm_x = self.norm1(x)
qkv = self.self_attn_qkv(norm_x)
q, k, v = rearrange(qkv, "B L (K H D) -> K B L H D", K=3, H=self.heads_num)
# Apply QK-Norm if needed
q = self.self_attn_q_norm(q).to(v)
k = self.self_attn_k_norm(k).to(v)
# Self-Attention
attn = attention(q, k, v, mode="torch", attn_mask=attn_mask)
x = x + apply_gate(self.self_attn_proj(attn), gate_msa)
# FFN Layer
x = x + apply_gate(self.mlp(self.norm2(x)), gate_mlp)
return x
class IndividualTokenRefiner(nn.Module):
def __init__(
self,
hidden_size,
heads_num,
depth,
mlp_width_ratio: float = 4.0,
mlp_drop_rate: float = 0.0,
act_type: str = "silu",
qk_norm: bool = False,
qk_norm_type: str = "layer",
qkv_bias: bool = True,
dtype: Optional[torch.dtype] = None,
device: Optional[torch.device] = None,
):
factory_kwargs = {"device": device, "dtype": dtype}
super().__init__()
self.blocks = nn.ModuleList(
[
IndividualTokenRefinerBlock(
hidden_size=hidden_size,
heads_num=heads_num,
mlp_width_ratio=mlp_width_ratio,
mlp_drop_rate=mlp_drop_rate,
act_type=act_type,
qk_norm=qk_norm,
qk_norm_type=qk_norm_type,
qkv_bias=qkv_bias,
**factory_kwargs,
)
for _ in range(depth)
]
)
def forward(
self,
x: torch.Tensor,
c: torch.LongTensor,
mask: Optional[torch.Tensor] = None,
):
self_attn_mask = None
if mask is not None:
batch_size = mask.shape[0]
seq_len = mask.shape[1]
mask = mask.to(x.device)
# batch_size x 1 x seq_len x seq_len
self_attn_mask_1 = mask.view(batch_size, 1, 1, seq_len).repeat(
1, 1, seq_len, 1
)
# batch_size x 1 x seq_len x seq_len
self_attn_mask_2 = self_attn_mask_1.transpose(2, 3)
# batch_size x 1 x seq_len x seq_len, 1 for broadcasting of heads_num
self_attn_mask = (self_attn_mask_1 & self_attn_mask_2).bool()
# avoids self-attention weight being NaN for padding tokens
self_attn_mask[:, :, :, 0] = True
for block in self.blocks:
x = block(x, c, self_attn_mask)
return x
class SingleTokenRefiner(nn.Module):
"""
A single token refiner block for llm text embedding refine.
"""
def __init__(
self,
in_channels,
hidden_size,
heads_num,
depth,
mlp_width_ratio: float = 4.0,
mlp_drop_rate: float = 0.0,
act_type: str = "silu",
qk_norm: bool = False,
qk_norm_type: str = "layer",
qkv_bias: bool = True,
attn_mode: str = "torch",
dtype: Optional[torch.dtype] = None,
device: Optional[torch.device] = None,
):
factory_kwargs = {"device": device, "dtype": dtype}
super().__init__()
self.attn_mode = attn_mode
assert self.attn_mode == "torch", "Only support 'torch' mode for token refiner."
self.input_embedder = nn.Linear(
in_channels, hidden_size, bias=True, **factory_kwargs
)
act_layer = get_activation_layer(act_type)
# Build timestep embedding layer
self.t_embedder = TimestepEmbedder(hidden_size, act_layer, **factory_kwargs)
# Build context embedding layer
self.c_embedder = TextProjection(
in_channels, hidden_size, act_layer, **factory_kwargs
)
self.individual_token_refiner = IndividualTokenRefiner(
hidden_size=hidden_size,
heads_num=heads_num,
depth=depth,
mlp_width_ratio=mlp_width_ratio,
mlp_drop_rate=mlp_drop_rate,
act_type=act_type,
qk_norm=qk_norm,
qk_norm_type=qk_norm_type,
qkv_bias=qkv_bias,
**factory_kwargs,
)
def forward(
self,
x: torch.Tensor,
t: torch.LongTensor,
mask: Optional[torch.LongTensor] = None,
):
timestep_aware_representations = self.t_embedder(t)
if mask is None:
context_aware_representations = x.mean(dim=1)
else:
mask_float = mask.float().unsqueeze(-1) # [b, s1, 1]
context_aware_representations = (x * mask_float).sum(
dim=1
) / mask_float.sum(dim=1)
context_aware_representations = self.c_embedder(context_aware_representations)
c = timestep_aware_representations + context_aware_representations
x = self.input_embedder(x)
x = self.individual_token_refiner(x, c, mask)
return x
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