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Python

# SPDX-License-Identifier: Apache-2.0
import math
import numpy as np
import torch
import torch.nn as nn
from fastvideo.v1.attention import DistributedAttention, LocalAttention
from fastvideo.v1.configs.models.dits import WanVideoConfig
from fastvideo.v1.configs.sample.wan import WanTeaCacheParams
from fastvideo.v1.distributed.parallel_state import (
get_sequence_model_parallel_world_size)
from fastvideo.v1.forward_context import get_forward_context
from fastvideo.v1.layers.layernorm import (LayerNormScaleShift, RMSNorm,
ScaleResidual,
ScaleResidualLayerNormScaleShift)
from fastvideo.v1.layers.linear import ReplicatedLinear
# from torch.nn import RMSNorm
# TODO: RMSNorm ....
from fastvideo.v1.layers.mlp import MLP
from fastvideo.v1.layers.rotary_embedding import (_apply_rotary_emb,
get_rotary_pos_embed)
from fastvideo.v1.layers.visual_embedding import (ModulateProjection,
PatchEmbed, TimestepEmbedder)
from fastvideo.v1.models.dits.base import CachableDiT
from fastvideo.v1.platforms import _Backend
class WanImageEmbedding(torch.nn.Module):
def __init__(self, in_features: int, out_features: int):
super().__init__()
self.norm1 = nn.LayerNorm(in_features)
self.ff = MLP(in_features, in_features, out_features, act_type="gelu")
self.norm2 = nn.LayerNorm(out_features)
def forward(self,
encoder_hidden_states_image: torch.Tensor) -> torch.Tensor:
dtype = encoder_hidden_states_image.dtype
hidden_states = self.norm1(encoder_hidden_states_image)
hidden_states = self.ff(hidden_states)
hidden_states = self.norm2(hidden_states).to(dtype)
return hidden_states
class WanTimeTextImageEmbedding(nn.Module):
def __init__(
self,
dim: int,
time_freq_dim: int,
text_embed_dim: int,
image_embed_dim: int | None = None,
):
super().__init__()
self.time_embedder = TimestepEmbedder(
dim, frequency_embedding_size=time_freq_dim, act_layer="silu")
self.time_modulation = ModulateProjection(dim,
factor=6,
act_layer="silu")
self.text_embedder = MLP(text_embed_dim,
dim,
dim,
bias=True,
act_type="gelu_pytorch_tanh")
self.image_embedder = None
if image_embed_dim is not None:
self.image_embedder = WanImageEmbedding(image_embed_dim, dim)
def forward(
self,
timestep: torch.Tensor,
encoder_hidden_states: torch.Tensor,
encoder_hidden_states_image: torch.Tensor | None = None,
):
temb = self.time_embedder(timestep)
timestep_proj = self.time_modulation(temb)
encoder_hidden_states = self.text_embedder(encoder_hidden_states)
if encoder_hidden_states_image is not None:
assert self.image_embedder is not None
encoder_hidden_states_image = self.image_embedder(
encoder_hidden_states_image)
return temb, timestep_proj, encoder_hidden_states, encoder_hidden_states_image
class WanSelfAttention(nn.Module):
def __init__(self,
dim: int,
num_heads: int,
window_size=(-1, -1),
qk_norm=True,
eps=1e-6,
parallel_attention=False) -> None:
assert dim % num_heads == 0
super().__init__()
self.dim = dim
self.num_heads = num_heads
self.head_dim = dim // num_heads
self.window_size = window_size
self.qk_norm = qk_norm
self.eps = eps
self.parallel_attention = parallel_attention
# layers
self.to_q = ReplicatedLinear(dim, dim)
self.to_k = ReplicatedLinear(dim, dim)
self.to_v = ReplicatedLinear(dim, dim)
self.to_out = ReplicatedLinear(dim, dim)
self.norm_q = RMSNorm(dim, eps=eps) if qk_norm else nn.Identity()
self.norm_k = RMSNorm(dim, eps=eps) if qk_norm else nn.Identity()
# Scaled dot product attention
self.attn = LocalAttention(
num_heads=num_heads,
head_size=self.head_dim,
dropout_rate=0,
softmax_scale=None,
causal=False,
supported_attention_backends=(_Backend.FLASH_ATTN,
_Backend.TORCH_SDPA))
def forward(self, x: torch.Tensor, context: torch.Tensor,
context_lens: int):
r"""
Args:
x(Tensor): Shape [B, L, num_heads, C / num_heads]
seq_lens(Tensor): Shape [B]
grid_sizes(Tensor): Shape [B, 3], the second dimension contains (F, H, W)
freqs(Tensor): Rope freqs, shape [1024, C / num_heads / 2]
"""
pass
class WanT2VCrossAttention(WanSelfAttention):
def forward(self, x, context, context_lens):
r"""
Args:
x(Tensor): Shape [B, L1, C]
context(Tensor): Shape [B, L2, C]
context_lens(Tensor): Shape [B]
"""
b, n, d = x.size(0), self.num_heads, self.head_dim
# compute query, key, value
q = self.norm_q(self.to_q(x)[0]).view(b, -1, n, d)
k = self.norm_k(self.to_k(context)[0]).view(b, -1, n, d)
v = self.to_v(context)[0].view(b, -1, n, d)
# compute attention
x = self.attn(q, k, v)
# output
x = x.flatten(2)
x, _ = self.to_out(x)
return x
class WanI2VCrossAttention(WanSelfAttention):
def __init__(
self,
dim: int,
num_heads: int,
window_size=(-1, -1),
qk_norm=True,
eps=1e-6,
supported_attention_backends: tuple[_Backend, ...] | None = None
) -> None:
super().__init__(dim, num_heads, window_size, qk_norm, eps,
supported_attention_backends)
self.add_k_proj = ReplicatedLinear(dim, dim)
self.add_v_proj = ReplicatedLinear(dim, dim)
self.norm_added_k = RMSNorm(dim, eps=eps) if qk_norm else nn.Identity()
self.norm_added_q = RMSNorm(dim, eps=eps) if qk_norm else nn.Identity()
def forward(self, x, context, context_lens):
r"""
Args:
x(Tensor): Shape [B, L1, C]
context(Tensor): Shape [B, L2, C]
context_lens(Tensor): Shape [B]
"""
context_img = context[:, :257]
context = context[:, 257:]
b, n, d = x.size(0), self.num_heads, self.head_dim
# compute query, key, value
q = self.norm_q(self.to_q(x)[0]).view(b, -1, n, d)
k = self.norm_k(self.to_k(context)[0]).view(b, -1, n, d)
v = self.to_v(context)[0].view(b, -1, n, d)
k_img = self.norm_added_k(self.add_k_proj(context_img)[0]).view(
b, -1, n, d)
v_img = self.add_v_proj(context_img)[0].view(b, -1, n, d)
img_x = self.attn(q, k_img, v_img)
# compute attention
x = self.attn(q, k, v)
# output
x = x.flatten(2)
img_x = img_x.flatten(2)
x = x + img_x
x, _ = self.to_out(x)
return x
class WanTransformerBlock(nn.Module):
def __init__(self,
dim: int,
ffn_dim: int,
num_heads: int,
qk_norm: str = "rms_norm_across_heads",
cross_attn_norm: bool = False,
eps: float = 1e-6,
added_kv_proj_dim: int | None = None,
supported_attention_backends: tuple[_Backend, ...]
| None = None,
prefix: str = ""):
super().__init__()
# 1. Self-attention
self.norm1 = nn.LayerNorm(dim, eps, elementwise_affine=False)
self.to_q = ReplicatedLinear(dim, dim, bias=True)
self.to_k = ReplicatedLinear(dim, dim, bias=True)
self.to_v = ReplicatedLinear(dim, dim, bias=True)
self.to_out = ReplicatedLinear(dim, dim, bias=True)
self.attn1 = DistributedAttention(
num_heads=num_heads,
head_size=dim // num_heads,
causal=False,
supported_attention_backends=supported_attention_backends,
prefix=f"{prefix}.attn1")
self.hidden_dim = dim
self.num_attention_heads = num_heads
dim_head = dim // num_heads
if qk_norm == "rms_norm":
self.norm_q = RMSNorm(dim_head, eps=eps)
self.norm_k = RMSNorm(dim_head, eps=eps)
elif qk_norm == "rms_norm_across_heads":
# LTX applies qk norm across all heads
self.norm_q = RMSNorm(dim, eps=eps)
self.norm_k = RMSNorm(dim, eps=eps)
else:
print("QK Norm type not supported")
raise Exception
assert cross_attn_norm is True
self.self_attn_residual_norm = ScaleResidualLayerNormScaleShift(
dim,
norm_type="layer",
eps=eps,
elementwise_affine=True,
dtype=torch.float32)
# 2. Cross-attention
if added_kv_proj_dim is not None:
# I2V
self.attn2 = WanI2VCrossAttention(dim,
num_heads,
qk_norm=qk_norm,
eps=eps)
else:
# T2V
self.attn2 = WanT2VCrossAttention(dim,
num_heads,
qk_norm=qk_norm,
eps=eps)
self.cross_attn_residual_norm = ScaleResidualLayerNormScaleShift(
dim,
norm_type="layer",
eps=eps,
elementwise_affine=False,
dtype=torch.float32)
# 3. Feed-forward
self.ffn = MLP(dim, ffn_dim, act_type="gelu_pytorch_tanh")
self.mlp_residual = ScaleResidual()
self.scale_shift_table = nn.Parameter(torch.randn(1, 6, dim) / dim**0.5)
def forward(
self,
hidden_states: torch.Tensor,
encoder_hidden_states: torch.Tensor,
temb: torch.Tensor,
freqs_cis: tuple[torch.Tensor, torch.Tensor],
) -> torch.Tensor:
if hidden_states.dim() == 4:
hidden_states = hidden_states.squeeze(1)
bs, seq_length, _ = hidden_states.shape
orig_dtype = hidden_states.dtype
assert orig_dtype != torch.float32
e = self.scale_shift_table + temb.float()
shift_msa, scale_msa, gate_msa, c_shift_msa, c_scale_msa, c_gate_msa = e.chunk(
6, dim=1)
assert shift_msa.dtype == torch.float32
# 1. Self-attention
norm_hidden_states = (self.norm1(hidden_states.float()) *
(1 + scale_msa) + shift_msa).to(orig_dtype)
query, _ = self.to_q(norm_hidden_states)
key, _ = self.to_k(norm_hidden_states)
value, _ = self.to_v(norm_hidden_states)
if self.norm_q is not None:
query = self.norm_q.forward_native(query)
if self.norm_k is not None:
key = self.norm_k.forward_native(key)
query = query.squeeze(1).unflatten(2, (self.num_attention_heads, -1))
key = key.squeeze(1).unflatten(2, (self.num_attention_heads, -1))
value = value.squeeze(1).unflatten(2, (self.num_attention_heads, -1))
# Apply rotary embeddings
cos, sin = freqs_cis
query, key = _apply_rotary_emb(query, cos, sin,
is_neox_style=False), _apply_rotary_emb(
key, cos, sin, is_neox_style=False)
attn_output, _ = self.attn1(query, key, value)
attn_output = attn_output.flatten(2)
attn_output, _ = self.to_out(attn_output)
attn_output = attn_output.squeeze(1)
null_shift = null_scale = torch.tensor([0], device=hidden_states.device)
norm_hidden_states, hidden_states = self.self_attn_residual_norm(
hidden_states, attn_output, gate_msa, null_shift, null_scale)
norm_hidden_states, hidden_states = norm_hidden_states.to(
orig_dtype), hidden_states.to(orig_dtype)
# 2. Cross-attention
attn_output = self.attn2(norm_hidden_states,
context=encoder_hidden_states,
context_lens=None)
norm_hidden_states, hidden_states = self.cross_attn_residual_norm(
hidden_states, attn_output, 1, c_shift_msa, c_scale_msa)
norm_hidden_states, hidden_states = norm_hidden_states.to(
orig_dtype), hidden_states.to(orig_dtype)
# 3. Feed-forward
ff_output = self.ffn(norm_hidden_states)
hidden_states = self.mlp_residual(hidden_states, ff_output, c_gate_msa)
hidden_states = hidden_states.to(orig_dtype)
return hidden_states
class WanTransformer3DModel(CachableDiT):
_fsdp_shard_conditions = WanVideoConfig()._fsdp_shard_conditions
_compile_conditions = WanVideoConfig()._compile_conditions
_supported_attention_backends = WanVideoConfig(
)._supported_attention_backends
_param_names_mapping = WanVideoConfig()._param_names_mapping
def __init__(self, config: WanVideoConfig) -> None:
super().__init__(config=config)
inner_dim = config.num_attention_heads * config.attention_head_dim
self.hidden_size = config.hidden_size
self.num_attention_heads = config.num_attention_heads
self.in_channels = config.in_channels
self.out_channels = config.out_channels
self.num_channels_latents = config.num_channels_latents
self.patch_size = config.patch_size
self.text_len = config.text_len
# 1. Patch & position embedding
self.patch_embedding = PatchEmbed(in_chans=config.in_channels,
embed_dim=inner_dim,
patch_size=config.patch_size,
flatten=False)
# 2. Condition embeddings
self.condition_embedder = WanTimeTextImageEmbedding(
dim=inner_dim,
time_freq_dim=config.freq_dim,
text_embed_dim=config.text_dim,
image_embed_dim=config.image_dim,
)
# 3. Transformer blocks
self.blocks = nn.ModuleList([
WanTransformerBlock(inner_dim,
config.ffn_dim,
config.num_attention_heads,
config.qk_norm,
config.cross_attn_norm,
config.eps,
config.added_kv_proj_dim,
self._supported_attention_backends,
prefix=f"{config.prefix}.blocks.{i}")
for i in range(config.num_layers)
])
# 4. Output norm & projection
self.norm_out = LayerNormScaleShift(inner_dim,
norm_type="layer",
eps=config.eps,
elementwise_affine=False,
dtype=torch.float32)
self.proj_out = nn.Linear(
inner_dim, config.out_channels * math.prod(config.patch_size))
self.scale_shift_table = nn.Parameter(
torch.randn(1, 2, inner_dim) / inner_dim**0.5)
self.gradient_checkpointing = False
self.__post_init__()
def forward(self,
hidden_states: torch.Tensor,
encoder_hidden_states: torch.Tensor | list[torch.Tensor],
timestep: torch.LongTensor,
encoder_hidden_states_image: torch.Tensor | list[torch.Tensor]
| None = None,
guidance=None,
**kwargs) -> torch.Tensor:
forward_batch = get_forward_context().forward_batch
enable_teacache = forward_batch is not None and forward_batch.enable_teacache
orig_dtype = hidden_states.dtype
if not isinstance(encoder_hidden_states, torch.Tensor):
encoder_hidden_states = encoder_hidden_states[0]
if isinstance(encoder_hidden_states_image,
list) and len(encoder_hidden_states_image) > 0:
encoder_hidden_states_image = encoder_hidden_states_image[0]
else:
encoder_hidden_states_image = None
batch_size, num_channels, num_frames, height, width = hidden_states.shape
p_t, p_h, p_w = self.patch_size
post_patch_num_frames = num_frames // p_t
post_patch_height = height // p_h
post_patch_width = width // p_w
# Get rotary embeddings
d = self.hidden_size // self.num_attention_heads
rope_dim_list = [d - 4 * (d // 6), 2 * (d // 6), 2 * (d // 6)]
freqs_cos, freqs_sin = get_rotary_pos_embed(
(post_patch_num_frames * get_sequence_model_parallel_world_size(),
post_patch_height, post_patch_width),
self.hidden_size,
self.num_attention_heads,
rope_dim_list,
dtype=torch.float64,
rope_theta=10000)
freqs_cos = freqs_cos.to(hidden_states.device)
freqs_sin = freqs_sin.to(hidden_states.device)
freqs_cis = (freqs_cos.float(),
freqs_sin.float()) if freqs_cos is not None else None
hidden_states = self.patch_embedding(hidden_states)
hidden_states = hidden_states.flatten(2).transpose(1, 2)
temb, timestep_proj, encoder_hidden_states, encoder_hidden_states_image = self.condition_embedder(
timestep, encoder_hidden_states, encoder_hidden_states_image)
timestep_proj = timestep_proj.unflatten(1, (6, -1))
if encoder_hidden_states_image is not None:
encoder_hidden_states = torch.concat(
[encoder_hidden_states_image, encoder_hidden_states], dim=1)
assert encoder_hidden_states.dtype == orig_dtype
# 4. Transformer blocks
# if caching is enabled, we might be able to skip the forward pass
should_skip_forward = self.should_skip_forward_for_cached_states(
timestep_proj=timestep_proj, temb=temb)
if should_skip_forward:
hidden_states = self.retrieve_cached_states(hidden_states)
else:
# if teacache is enabled, we need to cache the original hidden states
if enable_teacache:
original_hidden_states = hidden_states.clone()
if torch.is_grad_enabled() and self.gradient_checkpointing:
for block in self.blocks:
hidden_states = self._gradient_checkpointing_func(
block, hidden_states, encoder_hidden_states,
timestep_proj, freqs_cis)
else:
for block in self.blocks:
hidden_states = block(hidden_states, encoder_hidden_states,
timestep_proj, freqs_cis)
# if teacache is enabled, we need to cache the original hidden states
if enable_teacache:
self.maybe_cache_states(hidden_states, original_hidden_states)
# 5. Output norm, projection & unpatchify
shift, scale = (self.scale_shift_table + temb.unsqueeze(1)).chunk(2,
dim=1)
hidden_states = self.norm_out(hidden_states.float(), shift, scale)
hidden_states = self.proj_out(hidden_states)
hidden_states = hidden_states.reshape(batch_size, post_patch_num_frames,
post_patch_height,
post_patch_width, p_t, p_h, p_w,
-1)
hidden_states = hidden_states.permute(0, 7, 1, 4, 2, 5, 3, 6)
output = hidden_states.flatten(6, 7).flatten(4, 5).flatten(2, 3)
return output
def maybe_cache_states(self, hidden_states: torch.Tensor,
original_hidden_states: torch.Tensor) -> None:
if self.is_even:
self.previous_residual_even = hidden_states.squeeze(
0) - original_hidden_states
else:
self.previous_residual_odd = hidden_states.squeeze(
0) - original_hidden_states
def should_skip_forward_for_cached_states(self, **kwargs) -> bool:
forward_context = get_forward_context()
forward_batch = forward_context.forward_batch
if forward_batch is None or not forward_batch.enable_teacache:
return False
teacache_params = forward_batch.teacache_params
assert teacache_params is not None, "teacache_params is not initialized"
assert isinstance(
teacache_params,
WanTeaCacheParams), "teacache_params is not a WanTeaCacheParams"
current_timestep = forward_context.current_timestep
num_inference_steps = forward_batch.num_inference_steps
# initialize the coefficients, cutoff_steps, and ret_steps
coefficients = teacache_params.coefficients
use_ret_steps = teacache_params.use_ret_steps
cutoff_steps = teacache_params.get_cutoff_steps(num_inference_steps)
ret_steps = teacache_params.ret_steps
teacache_thresh = teacache_params.teacache_thresh
if current_timestep == 0:
self.cnt = 0
timestep_proj = kwargs["timestep_proj"]
temb = kwargs["temb"]
modulated_inp = timestep_proj if use_ret_steps else temb
if self.cnt % 2 == 0: # even -> condition
self.is_even = True
if self.cnt < ret_steps or self.cnt >= cutoff_steps:
self.should_calc_even = True
self.accumulated_rel_l1_distance_even = 0
else:
assert self.previous_e0_even is not None, "previous_e0_even is not initialized"
assert self.accumulated_rel_l1_distance_even is not None, "accumulated_rel_l1_distance_even is not initialized"
rescale_func = np.poly1d(coefficients)
self.accumulated_rel_l1_distance_even += rescale_func(
((modulated_inp - self.previous_e0_even).abs().mean() /
self.previous_e0_even.abs().mean()).cpu().item())
if self.accumulated_rel_l1_distance_even < teacache_thresh:
self.should_calc_even = False
else:
self.should_calc_even = True
self.accumulated_rel_l1_distance_even = 0
self.previous_e0_even = modulated_inp.clone()
else: # odd -> unconditon
self.is_even = False
if self.cnt < ret_steps or self.cnt >= cutoff_steps:
self.should_calc_odd = True
self.accumulated_rel_l1_distance_odd = 0
else:
assert self.previous_e0_odd is not None, "previous_e0_odd is not initialized"
assert self.accumulated_rel_l1_distance_odd is not None, "accumulated_rel_l1_distance_odd is not initialized"
rescale_func = np.poly1d(coefficients)
self.accumulated_rel_l1_distance_odd += rescale_func(
((modulated_inp - self.previous_e0_odd).abs().mean() /
self.previous_e0_odd.abs().mean()).cpu().item())
if self.accumulated_rel_l1_distance_odd < teacache_thresh:
self.should_calc_odd = False
else:
self.should_calc_odd = True
self.accumulated_rel_l1_distance_odd = 0
self.previous_e0_odd = modulated_inp.clone()
self.cnt += 1
should_skip_forward = False
if self.is_even:
if not self.should_calc_even:
should_skip_forward = True
else:
if not self.should_calc_odd:
should_skip_forward = True
return should_skip_forward
def retrieve_cached_states(self,
hidden_states: torch.Tensor) -> torch.Tensor:
if self.is_even:
return hidden_states + self.previous_residual_even
else:
return hidden_states + self.previous_residual_odd