ComfyUI/comfy/ldm/wan/vae.py
rattus 4e6a1b66a9
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speed up and reduce VRAM of QWEN VAE and WAN (less so) (#12036)
* ops: introduce autopad for conv3d

This works around pytorch missing ability to causal pad as part of the
kernel and avoids massive weight duplications for padding.

* wan-vae: rework causal padding

This currently uses F.pad which takes a full deep copy and is liable to
be the VRAM peak. Instead, kick spatial padding back to the op and
consolidate the temporal padding with the cat for the cache.

* wan-vae: implement zero pad fast path

The WAN VAE is also QWEN where it is used single-image. These
convolutions are however zero padded 3d convolutions, which means the
VAE is actually just 2D down the last element of the conv weight in
the temporal dimension. Fast path this, to avoid adding zeros that
then just evaporate in convoluton math but cost computation.
2026-01-23 19:56:14 -05:00

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# original version: https://github.com/Wan-Video/Wan2.1/blob/main/wan/modules/vae.py
# Copyright 2024-2025 The Alibaba Wan Team Authors. All rights reserved.
import torch
import torch.nn as nn
import torch.nn.functional as F
from einops import rearrange
from comfy.ldm.modules.diffusionmodules.model import vae_attention, torch_cat_if_needed
import comfy.ops
ops = comfy.ops.disable_weight_init
CACHE_T = 2
class CausalConv3d(ops.Conv3d):
"""
Causal 3d convolusion.
"""
def __init__(self, *args, **kwargs):
super().__init__(*args, **kwargs)
self._padding = 2 * self.padding[0]
self.padding = (0, self.padding[1], self.padding[2])
def forward(self, x, cache_x=None, cache_list=None, cache_idx=None):
if cache_list is not None:
cache_x = cache_list[cache_idx]
cache_list[cache_idx] = None
if cache_x is None and x.shape[2] == 1:
#Fast path - the op will pad for use by truncating the weight
#and save math on a pile of zeros.
return super().forward(x, autopad="causal_zero")
if self._padding > 0:
padding_needed = self._padding
if cache_x is not None:
cache_x = cache_x.to(x.device)
padding_needed = max(0, padding_needed - cache_x.shape[2])
padding_shape = list(x.shape)
padding_shape[2] = padding_needed
padding = torch.zeros(padding_shape, device=x.device, dtype=x.dtype)
x = torch_cat_if_needed([padding, cache_x, x], dim=2)
del cache_x
return super().forward(x)
class RMS_norm(nn.Module):
def __init__(self, dim, channel_first=True, images=True, bias=False):
super().__init__()
broadcastable_dims = (1, 1, 1) if not images else (1, 1)
shape = (dim, *broadcastable_dims) if channel_first else (dim,)
self.channel_first = channel_first
self.scale = dim**0.5
self.gamma = nn.Parameter(torch.ones(shape))
self.bias = nn.Parameter(torch.zeros(shape)) if bias else None
def forward(self, x):
return F.normalize(
x, dim=(1 if self.channel_first else -1)) * self.scale * self.gamma.to(x) + (self.bias.to(x) if self.bias is not None else 0)
class Resample(nn.Module):
def __init__(self, dim, mode):
assert mode in ('none', 'upsample2d', 'upsample3d', 'downsample2d',
'downsample3d')
super().__init__()
self.dim = dim
self.mode = mode
# layers
if mode == 'upsample2d':
self.resample = nn.Sequential(
nn.Upsample(scale_factor=(2., 2.), mode='nearest-exact'),
ops.Conv2d(dim, dim // 2, 3, padding=1))
elif mode == 'upsample3d':
self.resample = nn.Sequential(
nn.Upsample(scale_factor=(2., 2.), mode='nearest-exact'),
ops.Conv2d(dim, dim // 2, 3, padding=1))
self.time_conv = CausalConv3d(
dim, dim * 2, (3, 1, 1), padding=(1, 0, 0))
elif mode == 'downsample2d':
self.resample = nn.Sequential(
nn.ZeroPad2d((0, 1, 0, 1)),
ops.Conv2d(dim, dim, 3, stride=(2, 2)))
elif mode == 'downsample3d':
self.resample = nn.Sequential(
nn.ZeroPad2d((0, 1, 0, 1)),
ops.Conv2d(dim, dim, 3, stride=(2, 2)))
self.time_conv = CausalConv3d(
dim, dim, (3, 1, 1), stride=(2, 1, 1), padding=(0, 0, 0))
else:
self.resample = nn.Identity()
def forward(self, x, feat_cache=None, feat_idx=[0]):
b, c, t, h, w = x.size()
if self.mode == 'upsample3d':
if feat_cache is not None:
idx = feat_idx[0]
if feat_cache[idx] is None:
feat_cache[idx] = 'Rep'
feat_idx[0] += 1
else:
cache_x = x[:, :, -CACHE_T:, :, :].clone()
if cache_x.shape[2] < 2 and feat_cache[
idx] is not None and feat_cache[idx] != 'Rep':
# cache last frame of last two chunk
cache_x = torch.cat([
feat_cache[idx][:, :, -1, :, :].unsqueeze(2).to(
cache_x.device), cache_x
],
dim=2)
if cache_x.shape[2] < 2 and feat_cache[
idx] is not None and feat_cache[idx] == 'Rep':
cache_x = torch.cat([
torch.zeros_like(cache_x).to(cache_x.device),
cache_x
],
dim=2)
if feat_cache[idx] == 'Rep':
x = self.time_conv(x)
else:
x = self.time_conv(x, feat_cache[idx])
feat_cache[idx] = cache_x
feat_idx[0] += 1
x = x.reshape(b, 2, c, t, h, w)
x = torch.stack((x[:, 0, :, :, :, :], x[:, 1, :, :, :, :]),
3)
x = x.reshape(b, c, t * 2, h, w)
t = x.shape[2]
x = rearrange(x, 'b c t h w -> (b t) c h w')
x = self.resample(x)
x = rearrange(x, '(b t) c h w -> b c t h w', t=t)
if self.mode == 'downsample3d':
if feat_cache is not None:
idx = feat_idx[0]
if feat_cache[idx] is None:
feat_cache[idx] = x.clone()
feat_idx[0] += 1
else:
cache_x = x[:, :, -1:, :, :].clone()
# if cache_x.shape[2] < 2 and feat_cache[idx] is not None and feat_cache[idx]!='Rep':
# # cache last frame of last two chunk
# cache_x = torch.cat([feat_cache[idx][:, :, -1, :, :].unsqueeze(2).to(cache_x.device), cache_x], dim=2)
x = self.time_conv(
torch.cat([feat_cache[idx][:, :, -1:, :, :], x], 2))
feat_cache[idx] = cache_x
feat_idx[0] += 1
return x
class ResidualBlock(nn.Module):
def __init__(self, in_dim, out_dim, dropout=0.0):
super().__init__()
self.in_dim = in_dim
self.out_dim = out_dim
# layers
self.residual = nn.Sequential(
RMS_norm(in_dim, images=False), nn.SiLU(),
CausalConv3d(in_dim, out_dim, 3, padding=1),
RMS_norm(out_dim, images=False), nn.SiLU(), nn.Dropout(dropout),
CausalConv3d(out_dim, out_dim, 3, padding=1))
self.shortcut = CausalConv3d(in_dim, out_dim, 1) \
if in_dim != out_dim else nn.Identity()
def forward(self, x, feat_cache=None, feat_idx=[0]):
old_x = x
for layer in self.residual:
if isinstance(layer, CausalConv3d) and feat_cache is not None:
idx = feat_idx[0]
cache_x = x[:, :, -CACHE_T:, :, :].clone()
if cache_x.shape[2] < 2 and feat_cache[idx] is not None:
# cache last frame of last two chunk
cache_x = torch.cat([
feat_cache[idx][:, :, -1, :, :].unsqueeze(2).to(
cache_x.device), cache_x
],
dim=2)
x = layer(x, cache_list=feat_cache, cache_idx=idx)
feat_cache[idx] = cache_x
feat_idx[0] += 1
else:
x = layer(x)
return x + self.shortcut(old_x)
class AttentionBlock(nn.Module):
"""
Causal self-attention with a single head.
"""
def __init__(self, dim):
super().__init__()
self.dim = dim
# layers
self.norm = RMS_norm(dim)
self.to_qkv = ops.Conv2d(dim, dim * 3, 1)
self.proj = ops.Conv2d(dim, dim, 1)
self.optimized_attention = vae_attention()
def forward(self, x):
identity = x
b, c, t, h, w = x.size()
x = rearrange(x, 'b c t h w -> (b t) c h w')
x = self.norm(x)
# compute query, key, value
q, k, v = self.to_qkv(x).chunk(3, dim=1)
x = self.optimized_attention(q, k, v)
# output
x = self.proj(x)
x = rearrange(x, '(b t) c h w-> b c t h w', t=t)
return x + identity
class Encoder3d(nn.Module):
def __init__(self,
dim=128,
z_dim=4,
input_channels=3,
dim_mult=[1, 2, 4, 4],
num_res_blocks=2,
attn_scales=[],
temperal_downsample=[True, True, False],
dropout=0.0):
super().__init__()
self.dim = dim
self.z_dim = z_dim
self.dim_mult = dim_mult
self.num_res_blocks = num_res_blocks
self.attn_scales = attn_scales
self.temperal_downsample = temperal_downsample
# dimensions
dims = [dim * u for u in [1] + dim_mult]
scale = 1.0
# init block
self.conv1 = CausalConv3d(input_channels, dims[0], 3, padding=1)
# downsample blocks
downsamples = []
for i, (in_dim, out_dim) in enumerate(zip(dims[:-1], dims[1:])):
# residual (+attention) blocks
for _ in range(num_res_blocks):
downsamples.append(ResidualBlock(in_dim, out_dim, dropout))
if scale in attn_scales:
downsamples.append(AttentionBlock(out_dim))
in_dim = out_dim
# downsample block
if i != len(dim_mult) - 1:
mode = 'downsample3d' if temperal_downsample[
i] else 'downsample2d'
downsamples.append(Resample(out_dim, mode=mode))
scale /= 2.0
self.downsamples = nn.Sequential(*downsamples)
# middle blocks
self.middle = nn.Sequential(
ResidualBlock(out_dim, out_dim, dropout), AttentionBlock(out_dim),
ResidualBlock(out_dim, out_dim, dropout))
# output blocks
self.head = nn.Sequential(
RMS_norm(out_dim, images=False), nn.SiLU(),
CausalConv3d(out_dim, z_dim, 3, padding=1))
def forward(self, x, feat_cache=None, feat_idx=[0]):
if feat_cache is not None:
idx = feat_idx[0]
cache_x = x[:, :, -CACHE_T:, :, :].clone()
if cache_x.shape[2] < 2 and feat_cache[idx] is not None:
# cache last frame of last two chunk
cache_x = torch.cat([
feat_cache[idx][:, :, -1, :, :].unsqueeze(2).to(
cache_x.device), cache_x
],
dim=2)
x = self.conv1(x, feat_cache[idx])
feat_cache[idx] = cache_x
feat_idx[0] += 1
else:
x = self.conv1(x)
## downsamples
for layer in self.downsamples:
if feat_cache is not None:
x = layer(x, feat_cache, feat_idx)
else:
x = layer(x)
## middle
for layer in self.middle:
if isinstance(layer, ResidualBlock) and feat_cache is not None:
x = layer(x, feat_cache, feat_idx)
else:
x = layer(x)
## head
for layer in self.head:
if isinstance(layer, CausalConv3d) and feat_cache is not None:
idx = feat_idx[0]
cache_x = x[:, :, -CACHE_T:, :, :].clone()
if cache_x.shape[2] < 2 and feat_cache[idx] is not None:
# cache last frame of last two chunk
cache_x = torch.cat([
feat_cache[idx][:, :, -1, :, :].unsqueeze(2).to(
cache_x.device), cache_x
],
dim=2)
x = layer(x, feat_cache[idx])
feat_cache[idx] = cache_x
feat_idx[0] += 1
else:
x = layer(x)
return x
class Decoder3d(nn.Module):
def __init__(self,
dim=128,
z_dim=4,
output_channels=3,
dim_mult=[1, 2, 4, 4],
num_res_blocks=2,
attn_scales=[],
temperal_upsample=[False, True, True],
dropout=0.0):
super().__init__()
self.dim = dim
self.z_dim = z_dim
self.dim_mult = dim_mult
self.num_res_blocks = num_res_blocks
self.attn_scales = attn_scales
self.temperal_upsample = temperal_upsample
# dimensions
dims = [dim * u for u in [dim_mult[-1]] + dim_mult[::-1]]
scale = 1.0 / 2**(len(dim_mult) - 2)
# init block
self.conv1 = CausalConv3d(z_dim, dims[0], 3, padding=1)
# middle blocks
self.middle = nn.Sequential(
ResidualBlock(dims[0], dims[0], dropout), AttentionBlock(dims[0]),
ResidualBlock(dims[0], dims[0], dropout))
# upsample blocks
upsamples = []
for i, (in_dim, out_dim) in enumerate(zip(dims[:-1], dims[1:])):
# residual (+attention) blocks
if i == 1 or i == 2 or i == 3:
in_dim = in_dim // 2
for _ in range(num_res_blocks + 1):
upsamples.append(ResidualBlock(in_dim, out_dim, dropout))
if scale in attn_scales:
upsamples.append(AttentionBlock(out_dim))
in_dim = out_dim
# upsample block
if i != len(dim_mult) - 1:
mode = 'upsample3d' if temperal_upsample[i] else 'upsample2d'
upsamples.append(Resample(out_dim, mode=mode))
scale *= 2.0
self.upsamples = nn.Sequential(*upsamples)
# output blocks
self.head = nn.Sequential(
RMS_norm(out_dim, images=False), nn.SiLU(),
CausalConv3d(out_dim, output_channels, 3, padding=1))
def forward(self, x, feat_cache=None, feat_idx=[0]):
## conv1
if feat_cache is not None:
idx = feat_idx[0]
cache_x = x[:, :, -CACHE_T:, :, :].clone()
if cache_x.shape[2] < 2 and feat_cache[idx] is not None:
# cache last frame of last two chunk
cache_x = torch.cat([
feat_cache[idx][:, :, -1, :, :].unsqueeze(2).to(
cache_x.device), cache_x
],
dim=2)
x = self.conv1(x, feat_cache[idx])
feat_cache[idx] = cache_x
feat_idx[0] += 1
else:
x = self.conv1(x)
## middle
for layer in self.middle:
if isinstance(layer, ResidualBlock) and feat_cache is not None:
x = layer(x, feat_cache, feat_idx)
else:
x = layer(x)
## upsamples
for layer in self.upsamples:
if feat_cache is not None:
x = layer(x, feat_cache, feat_idx)
else:
x = layer(x)
## head
for layer in self.head:
if isinstance(layer, CausalConv3d) and feat_cache is not None:
idx = feat_idx[0]
cache_x = x[:, :, -CACHE_T:, :, :].clone()
if cache_x.shape[2] < 2 and feat_cache[idx] is not None:
# cache last frame of last two chunk
cache_x = torch.cat([
feat_cache[idx][:, :, -1, :, :].unsqueeze(2).to(
cache_x.device), cache_x
],
dim=2)
x = layer(x, feat_cache[idx])
feat_cache[idx] = cache_x
feat_idx[0] += 1
else:
x = layer(x)
return x
def count_conv3d(model):
count = 0
for m in model.modules():
if isinstance(m, CausalConv3d):
count += 1
return count
class WanVAE(nn.Module):
def __init__(self,
dim=128,
z_dim=4,
dim_mult=[1, 2, 4, 4],
num_res_blocks=2,
attn_scales=[],
temperal_downsample=[True, True, False],
image_channels=3,
dropout=0.0):
super().__init__()
self.dim = dim
self.z_dim = z_dim
self.dim_mult = dim_mult
self.num_res_blocks = num_res_blocks
self.attn_scales = attn_scales
self.temperal_downsample = temperal_downsample
self.temperal_upsample = temperal_downsample[::-1]
# modules
self.encoder = Encoder3d(dim, z_dim * 2, image_channels, dim_mult, num_res_blocks,
attn_scales, self.temperal_downsample, dropout)
self.conv1 = CausalConv3d(z_dim * 2, z_dim * 2, 1)
self.conv2 = CausalConv3d(z_dim, z_dim, 1)
self.decoder = Decoder3d(dim, z_dim, image_channels, dim_mult, num_res_blocks,
attn_scales, self.temperal_upsample, dropout)
def encode(self, x):
conv_idx = [0]
feat_map = [None] * count_conv3d(self.decoder)
## cache
t = x.shape[2]
iter_ = 1 + (t - 1) // 4
## 对encode输入的x按时间拆分为1、4、4、4....
for i in range(iter_):
conv_idx = [0]
if i == 0:
out = self.encoder(
x[:, :, :1, :, :],
feat_cache=feat_map,
feat_idx=conv_idx)
else:
out_ = self.encoder(
x[:, :, 1 + 4 * (i - 1):1 + 4 * i, :, :],
feat_cache=feat_map,
feat_idx=conv_idx)
out = torch.cat([out, out_], 2)
mu, log_var = self.conv1(out).chunk(2, dim=1)
return mu
def decode(self, z):
conv_idx = [0]
feat_map = [None] * count_conv3d(self.decoder)
# z: [b,c,t,h,w]
iter_ = z.shape[2]
x = self.conv2(z)
for i in range(iter_):
conv_idx = [0]
if i == 0:
out = self.decoder(
x[:, :, i:i + 1, :, :],
feat_cache=feat_map,
feat_idx=conv_idx)
else:
out_ = self.decoder(
x[:, :, i:i + 1, :, :],
feat_cache=feat_map,
feat_idx=conv_idx)
out = torch.cat([out, out_], 2)
return out