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PixArt/conf.py
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"""
List of all PixArt model types / settings
"""
pixart_conf = {
"PixArtMS_XL_2": { # models/PixArtMS
"target" : "PixArtMS",
"input_size" : 1024//8,
"lewei_scale" : 2,
"depth" : 28,
"num_heads" : 16,
"patch_size" : 2,
"hidden_size" : 1152,
},
"PixArt_XL_2": { # models/PixArt
"target" : "PixArt",
"input_size" : 512//8,
"lewei_scale" : 1,
"depth" : 28,
"num_heads" : 16,
"patch_size" : 2,
"hidden_size" : 1152,
},
}
pixart_res = {
"PixArtMS_XL_2": { # models/PixArtMS 1024x1024
'0.25': [512, 2048], '0.26': [512, 1984], '0.27': [512, 1920], '0.28': [512, 1856],
'0.32': [576, 1792], '0.33': [576, 1728], '0.35': [576, 1664], '0.40': [640, 1600],
'0.42': [640, 1536], '0.48': [704, 1472], '0.50': [704, 1408], '0.52': [704, 1344],
'0.57': [768, 1344], '0.60': [768, 1280], '0.68': [832, 1216], '0.72': [832, 1152],
'0.78': [896, 1152], '0.82': [896, 1088], '0.88': [960, 1088], '0.94': [960, 1024],
'1.00': [1024,1024], '1.07': [1024, 960], '1.13': [1088, 960], '1.21': [1088, 896],
'1.29': [1152, 896], '1.38': [1152, 832], '1.46': [1216, 832], '1.67': [1280, 768],
'1.75': [1344, 768], '2.00': [1408, 704], '2.09': [1472, 704], '2.40': [1536, 640],
'2.50': [1600, 640], '2.89': [1664, 576], '3.00': [1728, 576], '3.11': [1792, 576],
'3.62': [1856, 512], '3.75': [1920, 512], '3.88': [1984, 512], '4.00': [2048, 512],
},
"PixArt_XL_2": { # models/PixArt 512x512
'0.25': [256,1024], '0.26': [256, 992], '0.27': [256, 960], '0.28': [256, 928],
'0.32': [288, 896], '0.33': [288, 864], '0.35': [288, 832], '0.40': [320, 800],
'0.42': [320, 768], '0.48': [352, 736], '0.50': [352, 704], '0.52': [352, 672],
'0.57': [384, 672], '0.60': [384, 640], '0.68': [416, 608], '0.72': [416, 576],
'0.78': [448, 576], '0.82': [448, 544], '0.88': [480, 544], '0.94': [480, 512],
'1.00': [512, 512], '1.07': [512, 480], '1.13': [544, 480], '1.21': [544, 448],
'1.29': [576, 448], '1.38': [576, 416], '1.46': [608, 416], '1.67': [640, 384],
'1.75': [672, 384], '2.00': [704, 352], '2.09': [736, 352], '2.40': [768, 320],
'2.50': [800, 320], '2.89': [832, 288], '3.00': [864, 288], '3.11': [896, 288],
'3.62': [928, 256], '3.75': [960, 256], '3.88': [992, 256], '4.00': [1024,256]
},
}
PixArt/loader.py
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import comfy.supported_models_base
import comfy.latent_formats
import comfy.model_patcher
import comfy.model_base
import comfy.utils
import torch
from comfy import model_management
from .models import PixArtMS
class EXM_PixArt(comfy.supported_models_base.BASE):
unet_config = {}
unet_extra_config = {}
latent_format = comfy.latent_formats.SD15
def model_type(self, state_dict, prefix=""):
return comfy.model_base.ModelType.EPS
def load_pixart(model_path, model_conf):
state_dict = comfy.utils.load_torch_file(model_path)
state_dict = state_dict.get("model", state_dict)
parameters = comfy.utils.calculate_parameters(state_dict)
unet_dtype = model_management.unet_dtype(model_params=parameters)
model = comfy.model_base.BaseModel(
EXM_PixArt({"disable_unet_model_creation" : True }),
model_type=comfy.model_base.ModelType.EPS,
device=model_management.get_torch_device()
)
model.pixart_config = model_conf
if model_conf["target"] == "PixArtMS":
from .models.PixArtMS import PixArtMS
model.diffusion_model = PixArtMS(**model_conf)
elif model_conf["target"] == "PixArt":
from .models.PixArt import PixArt
model.diffusion_model = PixArt(**model_conf)
else:
raise NotImplementedError
model.diffusion_model.load_state_dict(state_dict)
model.diffusion_model.dtype = unet_dtype
model.diffusion_model.eval()
model.diffusion_model.to(unet_dtype)
model_patcher = comfy.model_patcher.ModelPatcher(
model,
load_device = comfy.model_management.get_torch_device(),
offload_device = comfy.model_management.unet_offload_device(),
current_device = "cpu",
)
return model_patcher
PixArt/models/PixArt.py
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# Copyright (c) Meta Platforms, Inc. and affiliates.
# All rights reserved.
# This source code is licensed under the license found in the
# LICENSE file in the root directory of this source tree.
# --------------------------------------------------------
# References:
# GLIDE: https://github.com/openai/glide-text2im
# MAE: https://github.com/facebookresearch/mae/blob/main/models_mae.py
# --------------------------------------------------------
import math
import torch
import torch.nn as nn
import os
import numpy as np
from timm.models.layers import DropPath
from timm.models.vision_transformer import PatchEmbed, Mlp
from .utils import auto_grad_checkpoint, to_2tuple
from .PixArt_blocks import t2i_modulate, CaptionEmbedder, WindowAttention, MultiHeadCrossAttention, T2IFinalLayer, TimestepEmbedder, LabelEmbedder, FinalLayer
class PixArtBlock(nn.Module):
"""
A PixArt block with adaptive layer norm (adaLN-single) conditioning.
"""
def __init__(self, hidden_size, num_heads, mlp_ratio=4.0, drop_path=0., window_size=0, input_size=None, use_rel_pos=False, **block_kwargs):
super().__init__()
self.norm1 = nn.LayerNorm(hidden_size, elementwise_affine=False, eps=1e-6)
self.attn = WindowAttention(hidden_size, num_heads=num_heads, qkv_bias=True,
input_size=input_size if window_size == 0 else (window_size, window_size),
use_rel_pos=use_rel_pos, **block_kwargs)
self.cross_attn = MultiHeadCrossAttention(hidden_size, num_heads, **block_kwargs)
self.norm2 = nn.LayerNorm(hidden_size, elementwise_affine=False, eps=1e-6)
# to be compatible with lower version pytorch
approx_gelu = lambda: nn.GELU(approximate="tanh")
self.mlp = Mlp(in_features=hidden_size, hidden_features=int(hidden_size * mlp_ratio), act_layer=approx_gelu, drop=0)
self.drop_path = DropPath(drop_path) if drop_path > 0. else nn.Identity()
self.window_size = window_size
self.scale_shift_table = nn.Parameter(torch.randn(6, hidden_size) / hidden_size ** 0.5)
def forward(self, x, y, t, mask=None):
B, N, C = x.shape
shift_msa, scale_msa, gate_msa, shift_mlp, scale_mlp, gate_mlp = (self.scale_shift_table[None] + t.reshape(B, 6, -1)).chunk(6, dim=1)
x = x + self.drop_path(gate_msa * self.attn(t2i_modulate(self.norm1(x), shift_msa, scale_msa)).reshape(B, N, C))
x = x + self.cross_attn(x, y, mask)
x = x + self.drop_path(gate_mlp * self.mlp(t2i_modulate(self.norm2(x), shift_mlp, scale_mlp)))
return x
#############################################################################
# Core PixArt Model #
#################################################################################
class PixArt(nn.Module):
"""
Diffusion model with a Transformer backbone.
"""
def __init__(
self,
input_size=32,
patch_size=2,
in_channels=4,
hidden_size=1152,
depth=28,
num_heads=16,
mlp_ratio=4.0,
class_dropout_prob=0.1,
pred_sigma=True,
drop_path: float = 0.,
window_size=0,
window_block_indexes=[],
use_rel_pos=False,
caption_channels=4096,
lewei_scale=1.0,
config=None,
**kwargs,
):
super().__init__()
self.pred_sigma = pred_sigma
self.in_channels = in_channels
self.out_channels = in_channels * 2 if pred_sigma else in_channels
self.patch_size = patch_size
self.num_heads = num_heads
self.lewei_scale = lewei_scale,
self.dtype = torch.get_default_dtype()
self.x_embedder = PatchEmbed(input_size, patch_size, in_channels, hidden_size, bias=True)
self.t_embedder = TimestepEmbedder(hidden_size)
num_patches = self.x_embedder.num_patches
self.base_size = input_size // self.patch_size
# Will use fixed sin-cos embedding:
self.register_buffer("pos_embed", torch.zeros(1, num_patches, hidden_size))
approx_gelu = lambda: nn.GELU(approximate="tanh")
self.t_block = nn.Sequential(
nn.SiLU(),
nn.Linear(hidden_size, 6 * hidden_size, bias=True)
)
self.y_embedder = CaptionEmbedder(in_channels=caption_channels, hidden_size=hidden_size, uncond_prob=class_dropout_prob, act_layer=approx_gelu)
drop_path = [x.item() for x in torch.linspace(0, drop_path, depth)] # stochastic depth decay rule
self.blocks = nn.ModuleList([
PixArtBlock(hidden_size, num_heads, mlp_ratio=mlp_ratio, drop_path=drop_path[i],
input_size=(input_size // patch_size, input_size // patch_size),
window_size=window_size if i in window_block_indexes else 0,
use_rel_pos=use_rel_pos if i in window_block_indexes else False)
for i in range(depth)
])
self.final_layer = T2IFinalLayer(hidden_size, patch_size, self.out_channels)
self.initialize_weights()
print(f'Warning: lewei scale: {self.lewei_scale}, base size: {self.base_size}')
def forward_raw(self, x, t, y, mask=None, data_info=None):
"""
Original forward pass of PixArt.
x: (N, C, H, W) tensor of spatial inputs (images or latent representations of images)
t: (N,) tensor of diffusion timesteps
y: (N, 1, 120, C) tensor of class labels
"""
self.h, self.w = x.shape[-2]//self.patch_size, x.shape[-1]//self.patch_size
x = self.x_embedder(x) + self.pos_embed # (N, T, D), where T = H * W / patch_size ** 2
t = self.t_embedder(t) # (N, D)
t0 = self.t_block(t)
y = self.y_embedder(y, self.training) # (N, 1, L, D)
if self.training:
mask = mask.squeeze(1).squeeze(1)
y = y.squeeze(1).masked_select(mask.unsqueeze(-1) != 0).view(1, -1, x.shape[-1])
y_lens = mask.sum(dim=1).tolist()
else:
y_lens = [y.shape[2]] * y.shape[0]
y = y.squeeze(1).view(1, -1, x.shape[-1])
for block in self.blocks:
x = auto_grad_checkpoint(block, x, y, t0, y_lens) # (N, T, D) #support grad checkpoint
x = self.final_layer(x, t) # (N, T, patch_size ** 2 * out_channels)
x = self.unpatchify(x) # (N, out_channels, H, W)
return x
def forward(self, x, timesteps, context, y=None, **kwargs):
"""
Forward pass that adapts comfy input to original forward function
x: (N, C, H, W) tensor of spatial inputs (images or latent representations of images)
timesteps: (N,) tensor of diffusion timesteps
context: (N, 1, 120, C) conditioning
y: extra conditioning.
"""
## Still accepts the input w/o that dim but returns garbage
if len(context.shape) == 3:
context = context.unsqueeze(1)
## run original forward pass
out = self.forward_raw(
x = x.to(self.dtype),
t = timesteps.to(self.dtype),
y = context.to(self.dtype),
)
## only return EPS
out = out.to(torch.float)
eps, rest = out[:, :self.in_channels], out[:, self.in_channels:]
return eps
def forward_with_dpmsolver(self, x, t, y, mask=None, **kwargs):
"""
dpm solver donnot need variance prediction
"""
# https://github.com/openai/glide-text2im/blob/main/notebooks/text2im.ipynb
model_out = self.forward(x, t, y, mask)
return model_out.chunk(2, dim=1)[0]
def forward_with_cfg(self, x, t, y, cfg_scale, **kwargs):
"""
Forward pass of PixArt, but also batches the unconditional forward pass for classifier-free guidance.
"""
# https://github.com/openai/glide-text2im/blob/main/notebooks/text2im.ipynb
half = x[: len(x) // 2]
combined = torch.cat([half, half], dim=0)
model_out = self.forward(combined, t, y, kwargs)
model_out = model_out['x'] if isinstance(model_out, dict) else model_out
eps, rest = model_out[:, :3], model_out[:, 3:]
cond_eps, uncond_eps = torch.split(eps, len(eps) // 2, dim=0)
half_eps = uncond_eps + cfg_scale * (cond_eps - uncond_eps)
eps = torch.cat([half_eps, half_eps], dim=0)
return torch.cat([eps, rest], dim=1)
def unpatchify(self, x):
"""
x: (N, T, patch_size**2 * C)
imgs: (N, H, W, C)
"""
c = self.out_channels
p = self.x_embedder.patch_size[0]
h = w = int(x.shape[1] ** 0.5)
assert h * w == x.shape[1]
x = x.reshape(shape=(x.shape[0], h, w, p, p, c))
x = torch.einsum('nhwpqc->nchpwq', x)
imgs = x.reshape(shape=(x.shape[0], c, h * p, h * p))
return imgs
def initialize_weights(self):
# Initialize transformer layers:
def _basic_init(module):
if isinstance(module, nn.Linear):
torch.nn.init.xavier_uniform_(module.weight)
if module.bias is not None:
nn.init.constant_(module.bias, 0)
self.apply(_basic_init)
# Initialize (and freeze) pos_embed by sin-cos embedding:
pos_embed = get_2d_sincos_pos_embed(self.pos_embed.shape[-1], int(self.x_embedder.num_patches ** 0.5), lewei_scale=self.lewei_scale, base_size=self.base_size)
self.pos_embed.data.copy_(torch.from_numpy(pos_embed).unsqueeze(0).to(self.dtype))
# Initialize patch_embed like nn.Linear (instead of nn.Conv2d):
w = self.x_embedder.proj.weight.data
nn.init.xavier_uniform_(w.view([w.shape[0], -1]))
# Initialize timestep embedding MLP:
nn.init.normal_(self.t_embedder.mlp[0].weight, std=0.02)
nn.init.normal_(self.t_embedder.mlp[2].weight, std=0.02)
nn.init.normal_(self.t_block[1].weight, std=0.02)
# Initialize caption embedding MLP:
nn.init.normal_(self.y_embedder.y_proj.fc1.weight, std=0.02)
nn.init.normal_(self.y_embedder.y_proj.fc2.weight, std=0.02)
# Zero-out adaLN modulation layers in PixArt blocks:
for block in self.blocks:
nn.init.constant_(block.cross_attn.proj.weight, 0)
nn.init.constant_(block.cross_attn.proj.bias, 0)
# Zero-out output layers:
nn.init.constant_(self.final_layer.linear.weight, 0)
nn.init.constant_(self.final_layer.linear.bias, 0)
def get_2d_sincos_pos_embed(embed_dim, grid_size, cls_token=False, extra_tokens=0, lewei_scale=1.0, base_size=16):
"""
grid_size: int of the grid height and width
return:
pos_embed: [grid_size*grid_size, embed_dim] or [1+grid_size*grid_size, embed_dim] (w/ or w/o cls_token)
"""
if isinstance(grid_size, int):
grid_size = to_2tuple(grid_size)
grid_h = np.arange(grid_size[0], dtype=np.float32) / (grid_size[0]/base_size) / lewei_scale
grid_w = np.arange(grid_size[1], dtype=np.float32) / (grid_size[1]/base_size) / lewei_scale
grid = np.meshgrid(grid_w, grid_h) # here w goes first
grid = np.stack(grid, axis=0)
grid = grid.reshape([2, 1, grid_size[1], grid_size[0]])
pos_embed = get_2d_sincos_pos_embed_from_grid(embed_dim, grid)
if cls_token and extra_tokens > 0:
pos_embed = np.concatenate([np.zeros([extra_tokens, embed_dim]), pos_embed], axis=0)
return pos_embed
def get_2d_sincos_pos_embed_from_grid(embed_dim, grid):
assert embed_dim % 2 == 0
# use half of dimensions to encode grid_h
emb_h = get_1d_sincos_pos_embed_from_grid(embed_dim // 2, grid[0]) # (H*W, D/2)
emb_w = get_1d_sincos_pos_embed_from_grid(embed_dim // 2, grid[1]) # (H*W, D/2)
emb = np.concatenate([emb_h, emb_w], axis=1) # (H*W, D)
return emb
def get_1d_sincos_pos_embed_from_grid(embed_dim, pos):
"""
embed_dim: output dimension for each position
pos: a list of positions to be encoded: size (M,)
out: (M, D)
"""
assert embed_dim % 2 == 0
omega = np.arange(embed_dim // 2, dtype=np.float64)
omega /= embed_dim / 2.
omega = 1. / 10000 ** omega # (D/2,)
pos = pos.reshape(-1) # (M,)
out = np.einsum('m,d->md', pos, omega) # (M, D/2), outer product
emb_sin = np.sin(out) # (M, D/2)
emb_cos = np.cos(out) # (M, D/2)
emb = np.concatenate([emb_sin, emb_cos], axis=1) # (M, D)
return emb
PixArt/models/PixArtMS.py
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# Copyright (c) Meta Platforms, Inc. and affiliates.
# All rights reserved.
# This source code is licensed under the license found in the
# LICENSE file in the root directory of this source tree.
# --------------------------------------------------------
# References:
# GLIDE: https://github.com/openai/glide-text2im
# MAE: https://github.com/facebookresearch/mae/blob/main/models_mae.py
# --------------------------------------------------------
import torch
import torch.nn as nn
from tqdm import tqdm
from timm.models.layers import DropPath
from timm.models.vision_transformer import Mlp
from .utils import auto_grad_checkpoint, to_2tuple
from .PixArt_blocks import t2i_modulate, CaptionEmbedder, WindowAttention, MultiHeadCrossAttention, T2IFinalLayer, TimestepEmbedder, SizeEmbedder
from .PixArt import PixArt, get_2d_sincos_pos_embed
class PatchEmbed(nn.Module):
""" 2D Image to Patch Embedding
"""
def __init__(
self,
patch_size=16,
in_chans=3,
embed_dim=768,
norm_layer=None,
flatten=True,
bias=True,
):
super().__init__()
patch_size = to_2tuple(patch_size)
self.patch_size = patch_size
self.flatten = flatten
self.proj = nn.Conv2d(in_chans, embed_dim, kernel_size=patch_size, stride=patch_size, bias=bias)
self.norm = norm_layer(embed_dim) if norm_layer else nn.Identity()
def forward(self, x):
x = self.proj(x)
if self.flatten:
x = x.flatten(2).transpose(1, 2) # BCHW -> BNC
x = self.norm(x)
return x
class PixArtMSBlock(nn.Module):
"""
A PixArt block with adaptive layer norm zero (adaLN-Zero) conditioning.
"""
def __init__(self, hidden_size, num_heads, mlp_ratio=4.0, drop_path=0., window_size=0, input_size=None, use_rel_pos=False, **block_kwargs):
super().__init__()
self.hidden_size = hidden_size
self.norm1 = nn.LayerNorm(hidden_size, elementwise_affine=False, eps=1e-6)
self.attn = WindowAttention(hidden_size, num_heads=num_heads, qkv_bias=True,
input_size=input_size if window_size == 0 else (window_size, window_size),
use_rel_pos=use_rel_pos, **block_kwargs)
self.cross_attn = MultiHeadCrossAttention(hidden_size, num_heads, **block_kwargs)
self.norm2 = nn.LayerNorm(hidden_size, elementwise_affine=False, eps=1e-6)
# to be compatible with lower version pytorch
approx_gelu = lambda: nn.GELU(approximate="tanh")
self.mlp = Mlp(in_features=hidden_size, hidden_features=int(hidden_size * mlp_ratio), act_layer=approx_gelu, drop=0)
self.drop_path = DropPath(drop_path) if drop_path > 0. else nn.Identity()
self.window_size = window_size
self.scale_shift_table = nn.Parameter(torch.randn(6, hidden_size) / hidden_size ** 0.5)
def forward(self, x, y, t, mask=None, **kwargs):
B, N, C = x.shape
shift_msa, scale_msa, gate_msa, shift_mlp, scale_mlp, gate_mlp = (self.scale_shift_table[None] + t.reshape(B, 6, -1)).chunk(6, dim=1)
x = x + self.drop_path(gate_msa * self.attn(t2i_modulate(self.norm1(x), shift_msa, scale_msa)))
x = x + self.cross_attn(x, y, mask)
x = x + self.drop_path(gate_mlp * self.mlp(t2i_modulate(self.norm2(x), shift_mlp, scale_mlp)))
return x
#############################################################################
# Core PixArt Model #
#################################################################################
class PixArtMS(PixArt):
"""
Diffusion model with a Transformer backbone.
"""
def __init__(
self,
input_size=32,
patch_size=2,
in_channels=4,
hidden_size=1152,
depth=28,
num_heads=16,
mlp_ratio=4.0,
class_dropout_prob=0.1,
learn_sigma=True,
pred_sigma=True,
drop_path: float = 0.,
window_size=0,
window_block_indexes=[],
use_rel_pos=False,
caption_channels=4096,
lewei_scale=1.,
config=None,
**kwargs,
):
super().__init__(
input_size=input_size,
patch_size=patch_size,
in_channels=in_channels,
hidden_size=hidden_size,
depth=depth,
num_heads=num_heads,
mlp_ratio=mlp_ratio,
class_dropout_prob=class_dropout_prob,
learn_sigma=learn_sigma,
pred_sigma=pred_sigma,
drop_path=drop_path,
window_size=window_size,
window_block_indexes=window_block_indexes,
use_rel_pos=use_rel_pos,
lewei_scale=lewei_scale,
config=config,
**kwargs,
)
self.dtype = torch.get_default_dtype()
self.h = self.w = 0
approx_gelu = lambda: nn.GELU(approximate="tanh")
self.t_block = nn.Sequential(
nn.SiLU(),
nn.Linear(hidden_size, 6 * hidden_size, bias=True)
)
self.x_embedder = PatchEmbed(patch_size, in_channels, hidden_size, bias=True)
self.y_embedder = CaptionEmbedder(in_channels=caption_channels, hidden_size=hidden_size, uncond_prob=class_dropout_prob, act_layer=approx_gelu)
self.csize_embedder = SizeEmbedder(hidden_size//3) # c_size embed
self.ar_embedder = SizeEmbedder(hidden_size//3) # aspect ratio embed
drop_path = [x.item() for x in torch.linspace(0, drop_path, depth)] # stochastic depth decay rule
self.blocks = nn.ModuleList([
PixArtMSBlock(hidden_size, num_heads, mlp_ratio=mlp_ratio, drop_path=drop_path[i],
input_size=(input_size // patch_size, input_size // patch_size),
window_size=window_size if i in window_block_indexes else 0,
use_rel_pos=use_rel_pos if i in window_block_indexes else False)
for i in range(depth)
])
self.final_layer = T2IFinalLayer(hidden_size, patch_size, self.out_channels)
self.training = False
self.initialize()
def forward_raw(self, x, t, y, mask=None, data_info=None, **kwargs):
"""
Original forward pass of PixArt.
x: (N, C, H, W) tensor of spatial inputs (images or latent representations of images)
t: (N,) tensor of diffusion timesteps
y: (N, 1, 120, C) tensor of class labels
"""
bs = x.shape[0]
c_size, ar = data_info['img_hw'], data_info['aspect_ratio']
self.h, self.w = x.shape[-2]//self.patch_size, x.shape[-1]//self.patch_size
pos_embed = torch.from_numpy(get_2d_sincos_pos_embed(self.pos_embed.shape[-1], (self.h, self.w), lewei_scale=self.lewei_scale, base_size=self.base_size)).unsqueeze(0).to(x.device).to(self.dtype)
x = self.x_embedder(x) + pos_embed # (N, T, D), where T = H * W / patch_size ** 2
t = self.t_embedder(t) # (N, D)
csize = self.csize_embedder(c_size, bs) # (N, D)
ar = self.ar_embedder(ar, bs) # (N, D)
t = t + torch.cat([csize, ar], dim=1)
t0 = self.t_block(t)
y = self.y_embedder(y, self.training) # (N, D)
if self.training:
mask = mask.squeeze(1).squeeze(1)
y = y.squeeze(1).masked_select(mask.unsqueeze(-1) != 0).view(1, -1, x.shape[-1])
y_lens = mask.sum(dim=1).tolist()
else:
y_lens = [y.shape[2]] * y.shape[0]
y = y.squeeze(1).view(1, -1, x.shape[-1])
for block in self.blocks:
x = auto_grad_checkpoint(block, x, y, t0, y_lens, **kwargs) # (N, T, D) #support grad checkpoint
x = self.final_layer(x, t) # (N, T, patch_size ** 2 * out_channels)
x = self.unpatchify(x) # (N, out_channels, H, W)
return x
def forward(self, x, timesteps, context, y=None, **kwargs):
"""
Forward pass that adapts comfy input to original forward function
x: (N, C, H, W) tensor of spatial inputs (images or latent representations of images)
timesteps: (N,) tensor of diffusion timesteps
context: (N, 1, 120, C) conditioning
y: extra conditioning.
"""
## aspect ratio based on the latent image shape.
# Ideally, these should only be used as a fallback with the real ones
# passed in `y` to allow different values to be used for cont/uncond.
bs = x.shape[0]
data_info = {
"img_hw" : torch.tensor(
[[x.shape[2]*8, x.shape[3]*8]],
dtype=self.dtype,
device=x.device
).repeat(bs, 1),
"aspect_ratio" : torch.tensor(
[[x.shape[2]/x.shape[3]]],
dtype=self.dtype,
device=x.device
).repeat(bs, 1),
}
## Still accepts the input w/o that dim but returns garbage
if len(context.shape) == 3:
context = context.unsqueeze(1)
## run original forward pass
out = self.forward_raw(
x = x.to(self.dtype),
t = timesteps.to(self.dtype),
y = context.to(self.dtype),
data_info=data_info,
)
## only return EPS
out = out.to(torch.float)
eps, rest = out[:, :self.in_channels], out[:, self.in_channels:]
return eps
def forward_with_dpmsolver(self, x, t, y, data_info, **kwargs):
"""
dpm solver donnot need variance prediction
"""
# https://github.com/openai/glide-text2im/blob/main/notebooks/text2im.ipynb
model_out = self.forward_raw(x, t, y, data_info=data_info, **kwargs)
return model_out.chunk(2, dim=1)[0]
def forward_with_cfg(self, x, t, y, cfg_scale, data_info, **kwargs):
"""
Forward pass of PixArt, but also batches the unconditional forward pass for classifier-free guidance.
"""
# https://github.com/openai/glide-text2im/blob/main/notebooks/text2im.ipynb
half = x[: len(x) // 2]
combined = torch.cat([half, half], dim=0)
model_out = self.forward_raw(combined, t, y, data_info=data_info)
eps, rest = model_out[:, :3], model_out[:, 3:]
cond_eps, uncond_eps = torch.split(eps, len(eps) // 2, dim=0)
half_eps = uncond_eps + cfg_scale * (cond_eps - uncond_eps)
eps = torch.cat([half_eps, half_eps], dim=0)
return torch.cat([eps, rest], dim=1)
def unpatchify(self, x):
"""
x: (N, T, patch_size**2 * C)
imgs: (N, H, W, C)
"""
c = self.out_channels
p = self.x_embedder.patch_size[0]
assert self.h * self.w == x.shape[1]
x = x.reshape(shape=(x.shape[0], self.h, self.w, p, p, c))
x = torch.einsum('nhwpqc->nchpwq', x)
imgs = x.reshape(shape=(x.shape[0], c, self.h * p, self.w * p))
return imgs
def initialize(self):
# Initialize transformer layers:
def _basic_init(module):
if isinstance(module, nn.Linear):
torch.nn.init.xavier_uniform_(module.weight)
if module.bias is not None:
nn.init.constant_(module.bias, 0)
self.apply(_basic_init)
# Initialize patch_embed like nn.Linear (instead of nn.Conv2d):
w = self.x_embedder.proj.weight.data
nn.init.xavier_uniform_(w.view([w.shape[0], -1]))
# Initialize timestep embedding MLP:
nn.init.normal_(self.t_embedder.mlp[0].weight, std=0.02)
nn.init.normal_(self.t_embedder.mlp[2].weight, std=0.02)
nn.init.normal_(self.t_block[1].weight, std=0.02)
nn.init.normal_(self.csize_embedder.mlp[0].weight, std=0.02)
nn.init.normal_(self.csize_embedder.mlp[2].weight, std=0.02)
nn.init.normal_(self.ar_embedder.mlp[0].weight, std=0.02)
nn.init.normal_(self.ar_embedder.mlp[2].weight, std=0.02)
# Initialize caption embedding MLP:
nn.init.normal_(self.y_embedder.y_proj.fc1.weight, std=0.02)
nn.init.normal_(self.y_embedder.y_proj.fc2.weight, std=0.02)
# Zero-out adaLN modulation layers in PixArt blocks:
for block in self.blocks:
nn.init.constant_(block.cross_attn.proj.weight, 0)
nn.init.constant_(block.cross_attn.proj.bias, 0)
# Zero-out output layers:
nn.init.constant_(self.final_layer.linear.weight, 0)
nn.init.constant_(self.final_layer.linear.bias, 0)
PixArt/models/PixArt_blocks.py
+435
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@@ -0,0 +1,435 @@
# Copyright (c) Meta Platforms, Inc. and affiliates.
# All rights reserved.
# This source code is licensed under the license found in the
# LICENSE file in the root directory of this source tree.
# --------------------------------------------------------
# References:
# GLIDE: https://github.com/openai/glide-text2im
# MAE: https://github.com/facebookresearch/mae/blob/main/models_mae.py
# --------------------------------------------------------
import math
import torch
import torch.nn as nn
from timm.models.vision_transformer import Mlp, Attention as Attention_
from einops import rearrange, repeat
import xformers.ops
from .utils import add_decomposed_rel_pos
from comfy import model_management
if model_management.xformers_enabled():
import xformers
import xformers.ops
def modulate(x, shift, scale):
return x * (1 + scale.unsqueeze(1)) + shift.unsqueeze(1)
def t2i_modulate(x, shift, scale):
return x * (1 + scale) + shift
competent_attention_implementation = False
class MultiHeadCrossAttention(nn.Module):
def __init__(self, d_model, num_heads, attn_drop=0., proj_drop=0., **block_kwargs):
super(MultiHeadCrossAttention, self).__init__()
assert d_model % num_heads == 0, "d_model must be divisible by num_heads"
self.d_model = d_model
self.num_heads = num_heads
self.head_dim = d_model // num_heads
self.q_linear = nn.Linear(d_model, d_model)
self.kv_linear = nn.Linear(d_model, d_model*2)
self.attn_drop = nn.Dropout(attn_drop)
self.proj = nn.Linear(d_model, d_model)
self.proj_drop = nn.Dropout(proj_drop)
def forward(self, x, cond, mask=None):
# query/value: img tokens; key: condition; mask: if padding tokens
B, N, C = x.shape
if model_management.xformers_enabled():
q = self.q_linear(x).view(1, -1, self.num_heads, self.head_dim)
kv = self.kv_linear(cond).view(1, -1, 2, self.num_heads, self.head_dim)
k, v = kv.unbind(2)
attn_bias = None
if mask is not None:
attn_bias = xformers.ops.fmha.BlockDiagonalMask.from_seqlens([N] * B, mask)
x = xformers.ops.memory_efficient_attention(q, k, v, p=self.attn_drop.p, attn_bias=attn_bias)
x = x.view(B, -1, C)
x = self.proj(x)
x = self.proj_drop(x)
return x
else:
global competent_attention_implementation
if not competent_attention_implementation:
print("""\nYou should REALLY consider installing/enabling xformers.\nAlternatively, open up ExtraModels/PixArt/models/PixArt_blocks.py and\n- Fix the attention map on line 77 if you know how to\n- Add scaled_dot_product_attention on line 150\n- Send a PR and remove this message on line 32/66-69\n""")
competent_attention_implementation = True
q = self.q_linear(x).view(1, -1, self.num_heads, self.head_dim)
kv = self.kv_linear(cond).view(1, -1, 2, self.num_heads, self.head_dim)
k, v = kv.unbind(2)
q, k, v = map(lambda t: t.permute(0, 2, 1, 3),(q, k, v),)
attn_mask = None
if mask is not None:
# This is probably wrong
attn_mask = torch.zeros(
[1, q.shape[1], q.shape[2], v.shape[2]],
dtype=q.dtype,
device=q.device
)
attn_mask[:, :, (q.shape[2]//2):, mask[0]:] = True
attn_mask[:, :, :(q.shape[2]//2), :mask[1]] = True
x = torch.nn.functional.scaled_dot_product_attention(q, k, v, attn_mask=attn_mask, dropout_p=self.attn_drop.p)
x = x.permute(0, 2, 1, 3).contiguous()
x = x.view(B, -1, C)
x = self.proj(x)
x = self.proj_drop(x)
return x
class WindowAttention(Attention_):
"""Multi-head Attention block with relative position embeddings."""
def __init__(
self,
dim,
num_heads=8,
qkv_bias=True,
use_rel_pos=False,
rel_pos_zero_init=True,
input_size=None,
**block_kwargs,
):
"""
Args:
dim (int): Number of input channels.
num_heads (int): Number of attention heads.
qkv_bias (bool: If True, add a learnable bias to query, key, value.
rel_pos (bool): If True, add relative positional embeddings to the attention map.
rel_pos_zero_init (bool): If True, zero initialize relative positional parameters.
input_size (int or None): Input resolution for calculating the relative positional
parameter size.
"""
super().__init__(dim, num_heads=num_heads, qkv_bias=qkv_bias, **block_kwargs)
self.use_rel_pos = use_rel_pos
if self.use_rel_pos:
# initialize relative positional embeddings
self.rel_pos_h = nn.Parameter(torch.zeros(2 * input_size[0] - 1, self.head_dim))
self.rel_pos_w = nn.Parameter(torch.zeros(2 * input_size[1] - 1, self.head_dim))
if not rel_pos_zero_init:
nn.init.trunc_normal_(self.rel_pos_h, std=0.02)
nn.init.trunc_normal_(self.rel_pos_w, std=0.02)
def forward(self, x, mask=None):
B, N, C = x.shape # 2 4096 1152
qkv = self.qkv(x).reshape(B, N, 3, self.num_heads, C // self.num_heads)
if model_management.xformers_enabled():
q, k, v = qkv.unbind(2)
if getattr(self, 'fp32_attention', False):
q, k, v = q.float(), k.float(), v.float()
attn_bias = None
if mask is not None:
attn_bias = torch.zeros([B * self.num_heads, q.shape[1], k.shape[1]], dtype=q.dtype, device=q.device)
attn_bias.masked_fill_(mask.squeeze(1).repeat(self.num_heads, 1, 1) == 0, float('-inf'))
# Switch between torch / xformers attention
x = xformers.ops.memory_efficient_attention(q, k, v, p=self.attn_drop.p, attn_bias=attn_bias)
x = x.view(B, N, C)
x = self.proj(x)
x = self.proj_drop(x)
return x
else:
q, k, v = qkv.permute(2, 0, 3, 1, 4).unbind(0)
q = q * self.scale
attn = q @ k.transpose(-2, -1)
attn = attn.softmax(dim=-1)
attn = self.attn_drop(attn)
x = attn @ v
x = x.transpose(1, 2).reshape(B, N, C)
x = self.proj(x)
x = self.proj_drop(x)
return x
#################################################################################
# AMP attention with fp32 softmax to fix loss NaN problem during training #
#################################################################################
class Attention(Attention_):
def forward(self, x):
B, N, C = x.shape
qkv = self.qkv(x).reshape(B, N, 3, self.num_heads, C // self.num_heads).permute(2, 0, 3, 1, 4)
q, k, v = qkv.unbind(0) # make torchscript happy (cannot use tensor as tuple)
use_fp32_attention = getattr(self, 'fp32_attention', False)
if use_fp32_attention:
q, k = q.float(), k.float()
with torch.cuda.amp.autocast(enabled=not use_fp32_attention):
attn = (q @ k.transpose(-2, -1)) * self.scale
attn = attn.softmax(dim=-1)
attn = self.attn_drop(attn)
x = (attn @ v).transpose(1, 2).reshape(B, N, C)
x = self.proj(x)
x = self.proj_drop(x)
return x
class FinalLayer(nn.Module):
"""
The final layer of PixArt.
"""
def __init__(self, hidden_size, patch_size, out_channels):
super().__init__()
self.norm_final = nn.LayerNorm(hidden_size, elementwise_affine=False, eps=1e-6)
self.linear = nn.Linear(hidden_size, patch_size * patch_size * out_channels, bias=True)
self.adaLN_modulation = nn.Sequential(
nn.SiLU(),
nn.Linear(hidden_size, 2 * hidden_size, bias=True)
)
def forward(self, x, c):
shift, scale = self.adaLN_modulation(c).chunk(2, dim=1)
x = modulate(self.norm_final(x), shift, scale)
x = self.linear(x)
return x
class T2IFinalLayer(nn.Module):
"""
The final layer of PixArt.
"""
def __init__(self, hidden_size, patch_size, out_channels):
super().__init__()
self.norm_final = nn.LayerNorm(hidden_size, elementwise_affine=False, eps=1e-6)
self.linear = nn.Linear(hidden_size, patch_size * patch_size * out_channels, bias=True)
self.scale_shift_table = nn.Parameter(torch.randn(2, hidden_size) / hidden_size ** 0.5)
self.out_channels = out_channels
def forward(self, x, t):
shift, scale = (self.scale_shift_table[None] + t[:, None]).chunk(2, dim=1)
x = t2i_modulate(self.norm_final(x), shift, scale)
x = self.linear(x)
return x
class MaskFinalLayer(nn.Module):
"""
The final layer of PixArt.
"""
def __init__(self, final_hidden_size, c_emb_size, patch_size, out_channels):
super().__init__()
self.norm_final = nn.LayerNorm(final_hidden_size, elementwise_affine=False, eps=1e-6)
self.linear = nn.Linear(final_hidden_size, patch_size * patch_size * out_channels, bias=True)
self.adaLN_modulation = nn.Sequential(
nn.SiLU(),
nn.Linear(c_emb_size, 2 * final_hidden_size, bias=True)
)
def forward(self, x, t):
shift, scale = self.adaLN_modulation(t).chunk(2, dim=1)
x = modulate(self.norm_final(x), shift, scale)
x = self.linear(x)
return x
class DecoderLayer(nn.Module):
"""
The final layer of PixArt.
"""
def __init__(self, hidden_size, decoder_hidden_size):
super().__init__()
self.norm_decoder = nn.LayerNorm(hidden_size, elementwise_affine=False, eps=1e-6)
self.linear = nn.Linear(hidden_size, decoder_hidden_size, bias=True)
self.adaLN_modulation = nn.Sequential(
nn.SiLU(),
nn.Linear(hidden_size, 2 * hidden_size, bias=True)
)
def forward(self, x, t):
shift, scale = self.adaLN_modulation(t).chunk(2, dim=1)
x = modulate(self.norm_decoder(x), shift, scale)
x = self.linear(x)
return x
#################################################################################
# Embedding Layers for Timesteps and Class Labels #
#################################################################################
class TimestepEmbedder(nn.Module):
"""
Embeds scalar timesteps into vector representations.
"""
def __init__(self, hidden_size, frequency_embedding_size=256):
super().__init__()
self.mlp = nn.Sequential(
nn.Linear(frequency_embedding_size, hidden_size, bias=True),
nn.SiLU(),
nn.Linear(hidden_size, hidden_size, bias=True),
)
self.frequency_embedding_size = frequency_embedding_size
@staticmethod
def timestep_embedding(t, dim, max_period=10000):
"""
Create sinusoidal timestep embeddings.
:param t: a 1-D Tensor of N indices, one per batch element.
These may be fractional.
:param dim: the dimension of the output.
:param max_period: controls the minimum frequency of the embeddings.
:return: an (N, D) Tensor of positional embeddings.
"""
# https://github.com/openai/glide-text2im/blob/main/glide_text2im/nn.py
half = dim // 2
freqs = torch.exp(
-math.log(max_period) * torch.arange(start=0, end=half, dtype=torch.float32, device=t.device) / half)
args = t[:, None].float() * freqs[None]
embedding = torch.cat([torch.cos(args), torch.sin(args)], dim=-1)
if dim % 2:
embedding = torch.cat([embedding, torch.zeros_like(embedding[:, :1])], dim=-1)
return embedding
def forward(self, t):
t_freq = self.timestep_embedding(t, self.frequency_embedding_size)
t_emb = self.mlp(t_freq.to(t.dtype))
return t_emb
class SizeEmbedder(TimestepEmbedder):
"""
Embeds scalar timesteps into vector representations.
"""
def __init__(self, hidden_size, frequency_embedding_size=256):
super().__init__(hidden_size=hidden_size, frequency_embedding_size=frequency_embedding_size)
self.mlp = nn.Sequential(
nn.Linear(frequency_embedding_size, hidden_size, bias=True),
nn.SiLU(),
nn.Linear(hidden_size, hidden_size, bias=True),
)
self.frequency_embedding_size = frequency_embedding_size
self.outdim = hidden_size
def forward(self, s, bs):
if s.ndim == 1:
s = s[:, None]
assert s.ndim == 2
if s.shape[0] != bs:
s = s.repeat(bs//s.shape[0], 1)
assert s.shape[0] == bs
b, dims = s.shape[0], s.shape[1]
s = rearrange(s, "b d -> (b d)")
s_freq = self.timestep_embedding(s, self.frequency_embedding_size)
s_emb = self.mlp(s_freq.to(s.dtype))
s_emb = rearrange(s_emb, "(b d) d2 -> b (d d2)", b=b, d=dims, d2=self.outdim)
return s_emb
class LabelEmbedder(nn.Module):
"""
Embeds class labels into vector representations. Also handles label dropout for classifier-free guidance.
"""
def __init__(self, num_classes, hidden_size, dropout_prob):
super().__init__()
use_cfg_embedding = dropout_prob > 0
self.embedding_table = nn.Embedding(num_classes + use_cfg_embedding, hidden_size)
self.num_classes = num_classes
self.dropout_prob = dropout_prob
def token_drop(self, labels, force_drop_ids=None):
"""
Drops labels to enable classifier-free guidance.
"""
if force_drop_ids is None:
drop_ids = torch.rand(labels.shape[0]).cuda() < self.dropout_prob
else:
drop_ids = force_drop_ids == 1
labels = torch.where(drop_ids, self.num_classes, labels)
return labels
def forward(self, labels, train, force_drop_ids=None):
use_dropout = self.dropout_prob > 0
if (train and use_dropout) or (force_drop_ids is not None):
labels = self.token_drop(labels, force_drop_ids)
embeddings = self.embedding_table(labels)
return embeddings
class CaptionEmbedder(nn.Module):
"""
Embeds class labels into vector representations. Also handles label dropout for classifier-free guidance.
"""
def __init__(self, in_channels, hidden_size, uncond_prob, act_layer=nn.GELU(approximate='tanh'), token_num=120):
super().__init__()
self.y_proj = Mlp(in_features=in_channels, hidden_features=hidden_size, out_features=hidden_size, act_layer=act_layer, drop=0)
self.register_buffer("y_embedding", nn.Parameter(torch.randn(token_num, in_channels) / in_channels ** 0.5))
self.uncond_prob = uncond_prob
def token_drop(self, caption, force_drop_ids=None):
"""
Drops labels to enable classifier-free guidance.
"""
if force_drop_ids is None:
drop_ids = torch.rand(caption.shape[0]).cuda() < self.uncond_prob
else:
drop_ids = force_drop_ids == 1
caption = torch.where(drop_ids[:, None, None, None], self.y_embedding, caption)
return caption
def forward(self, caption, train, force_drop_ids=None):
if train:
assert caption.shape[2:] == self.y_embedding.shape
use_dropout = self.uncond_prob > 0
if (train and use_dropout) or (force_drop_ids is not None):
caption = self.token_drop(caption, force_drop_ids)
caption = self.y_proj(caption)
return caption
class CaptionEmbedderDoubleBr(nn.Module):
"""
Embeds class labels into vector representations. Also handles label dropout for classifier-free guidance.
"""
def __init__(self, in_channels, hidden_size, uncond_prob, act_layer=nn.GELU(approximate='tanh'), token_num=120):
super().__init__()
self.proj = Mlp(in_features=in_channels, hidden_features=hidden_size, out_features=hidden_size, act_layer=act_layer, drop=0)
self.embedding = nn.Parameter(torch.randn(1, in_channels) / 10 ** 0.5)
self.y_embedding = nn.Parameter(torch.randn(token_num, in_channels) / 10 ** 0.5)
self.uncond_prob = uncond_prob
def token_drop(self, global_caption, caption, force_drop_ids=None):
"""
Drops labels to enable classifier-free guidance.
"""
if force_drop_ids is None:
drop_ids = torch.rand(global_caption.shape[0]).cuda() < self.uncond_prob
else:
drop_ids = force_drop_ids == 1
global_caption = torch.where(drop_ids[:, None], self.embedding, global_caption)
caption = torch.where(drop_ids[:, None, None, None], self.y_embedding, caption)
return global_caption, caption
def forward(self, caption, train, force_drop_ids=None):
assert caption.shape[2: ] == self.y_embedding.shape
global_caption = caption.mean(dim=2).squeeze()
use_dropout = self.uncond_prob > 0
if (train and use_dropout) or (force_drop_ids is not None):
global_caption, caption = self.token_drop(global_caption, caption, force_drop_ids)
y_embed = self.proj(global_caption)
return y_embed, caption
PixArt/models/utils.py
+122
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@@ -0,0 +1,122 @@
import torch
import torch.nn as nn
import torch.nn.functional as F
from torch.utils.checkpoint import checkpoint, checkpoint_sequential
from collections.abc import Iterable
from itertools import repeat
def _ntuple(n):
def parse(x):
if isinstance(x, Iterable) and not isinstance(x, str):
return x
return tuple(repeat(x, n))
return parse
to_1tuple = _ntuple(1)
to_2tuple = _ntuple(2)
def set_grad_checkpoint(model, use_fp32_attention=False, gc_step=1):
assert isinstance(model, nn.Module)
def set_attr(module):
module.grad_checkpointing = True
module.fp32_attention = use_fp32_attention
module.grad_checkpointing_step = gc_step
model.apply(set_attr)
def auto_grad_checkpoint(module, *args, **kwargs):
if getattr(module, 'grad_checkpointing', False):
if isinstance(module, Iterable):
gc_step = module[0].grad_checkpointing_step
return checkpoint_sequential(module, gc_step, *args, **kwargs)
else:
return checkpoint(module, *args, **kwargs)
return module(*args, **kwargs)
def checkpoint_sequential(functions, step, input, *args, **kwargs):
# Hack for keyword-only parameter in a python 2.7-compliant way
preserve = kwargs.pop('preserve_rng_state', True)
if kwargs:
raise ValueError("Unexpected keyword arguments: " + ",".join(arg for arg in kwargs))
def run_function(start, end, functions):
def forward(input):
for j in range(start, end + 1):
input = functions[j](input, *args)
return input
return forward
if isinstance(functions, torch.nn.Sequential):
functions = list(functions.children())
# the last chunk has to be non-volatile
end = -1
segment = len(functions) // step
for start in range(0, step * (segment - 1), step):
end = start + step - 1
input = checkpoint(run_function(start, end, functions), input, preserve_rng_state=preserve)
return run_function(end + 1, len(functions) - 1, functions)(input)
def get_rel_pos(q_size, k_size, rel_pos):
"""
Get relative positional embeddings according to the relative positions of
query and key sizes.
Args:
q_size (int): size of query q.
k_size (int): size of key k.
rel_pos (Tensor): relative position embeddings (L, C).
Returns:
Extracted positional embeddings according to relative positions.
"""
max_rel_dist = int(2 * max(q_size, k_size) - 1)
# Interpolate rel pos if needed.
if rel_pos.shape[0] != max_rel_dist:
# Interpolate rel pos.
rel_pos_resized = F.interpolate(
rel_pos.reshape(1, rel_pos.shape[0], -1).permute(0, 2, 1),
size=max_rel_dist,
mode="linear",
)
rel_pos_resized = rel_pos_resized.reshape(-1, max_rel_dist).permute(1, 0)
else:
rel_pos_resized = rel_pos
# Scale the coords with short length if shapes for q and k are different.
q_coords = torch.arange(q_size)[:, None] * max(k_size / q_size, 1.0)
k_coords = torch.arange(k_size)[None, :] * max(q_size / k_size, 1.0)
relative_coords = (q_coords - k_coords) + (k_size - 1) * max(q_size / k_size, 1.0)
return rel_pos_resized[relative_coords.long()]
def add_decomposed_rel_pos(attn, q, rel_pos_h, rel_pos_w, q_size, k_size):
"""
Calculate decomposed Relative Positional Embeddings from :paper:`mvitv2`.
https://github.com/facebookresearch/mvit/blob/19786631e330df9f3622e5402b4a419a263a2c80/mvit/models/attention.py # noqa B950
Args:
attn (Tensor): attention map.
q (Tensor): query q in the attention layer with shape (B, q_h * q_w, C).
rel_pos_h (Tensor): relative position embeddings (Lh, C) for height axis.
rel_pos_w (Tensor): relative position embeddings (Lw, C) for width axis.
q_size (Tuple): spatial sequence size of query q with (q_h, q_w).
k_size (Tuple): spatial sequence size of key k with (k_h, k_w).
Returns:
attn (Tensor): attention map with added relative positional embeddings.
"""
q_h, q_w = q_size
k_h, k_w = k_size
Rh = get_rel_pos(q_h, k_h, rel_pos_h)
Rw = get_rel_pos(q_w, k_w, rel_pos_w)
B, _, dim = q.shape
r_q = q.reshape(B, q_h, q_w, dim)
rel_h = torch.einsum("bhwc,hkc->bhwk", r_q, Rh)
rel_w = torch.einsum("bhwc,wkc->bhwk", r_q, Rw)
attn = (
attn.view(B, q_h, q_w, k_h, k_w) + rel_h[:, :, :, :, None] + rel_w[:, :, :, None, :]
).view(B, q_h * q_w, k_h * k_w)
return attn
PixArt/nodes.py
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import os
import json
import torch
import folder_paths
from .conf import pixart_conf, pixart_res
from .loader import load_pixart
from .sampler import sample_pixart
class PixArtCheckpointLoader:
@classmethod
def INPUT_TYPES(s):
return {
"required": {
"ckpt_name": (folder_paths.get_filename_list("checkpoints"),),
"model": (list(pixart_conf.keys()),),
}
}
RETURN_TYPES = ("MODEL",)
RETURN_NAMES = ("model",)
FUNCTION = "load_checkpoint"
CATEGORY = "ExtraModels/PixArt"
TITLE = "PixArt Checkpoint Loader"
def load_checkpoint(self, ckpt_name, model):
ckpt_path = folder_paths.get_full_path("checkpoints", ckpt_name)
model_conf = pixart_conf[model]
model = load_pixart(
model_path = ckpt_path,
model_conf = model_conf,
)
return (model,)
class PixArtResolutionSelect():
@classmethod
def INPUT_TYPES(s):
return {
"required": {
"model": (list(pixart_conf.keys()),),
# keys are the same for both
"ratio": (list(pixart_res["PixArtMS_XL_2"].keys()),{"default":"1.00"}),
}
}
RETURN_TYPES = ("INT","INT")
RETURN_NAMES = ("width","height")
FUNCTION = "get_res"
CATEGORY = "ExtraModels/PixArt"
TITLE = "PixArt Resolution Select"
def get_res(self, model, ratio):
width, height = pixart_res[model][ratio]
return (width,height)
class PixArtDPMSampler:
"""
The sampler from the reference code.
"""
@classmethod
def INPUT_TYPES(s):
return {
"required": {
"model": ("MODEL", ),
"seed": ("INT", {"default": 0, "min": 0, "max": 0xffffffffffffffff}),
"steps": ("INT", {"default": 20, "min": 1, "max": 10000}),
"cfg": ("FLOAT", {"default": 4.5, "min": 0.0, "max": 100.0, "step":0.5, "round": 0.01}),
"noise_schedule": (["linear","squaredcos_cap_v2"],{"default":"linear"}),
"noise_schedule_vp": (["linear","discrete"],{"default":"discrete"}),
"positive": ("CONDITIONING", ),
"negative": ("CONDITIONING", ),
"latent_image": ("LATENT", ),
}
}
RETURN_TYPES = ("LATENT",)
FUNCTION = "sample"
CATEGORY = "ExtraModels/PixArt"
TITLE = "PixArt DPM Sampler [Reference]"
def sample(self, model, seed, steps, cfg, noise_schedule, noise_schedule_vp, positive, negative, latent_image):
samples = sample_pixart(
model = model,
seed = seed,
steps = steps,
cfg = cfg,
positive = positive,
negative = negative,
latent_image = latent_image["samples"],
noise_schedule = noise_schedule,
noise_schedule_vp = noise_schedule_vp,
)
return ({"samples":samples},)
class PixArtT5TextEncode:
"""
Reference code, mostly to verify compatibility.
Once everything works, this should instead inherit from the
T5 text encode node and simply add the extra conds (res/ar).
"""
@classmethod
def INPUT_TYPES(s):
return {
"required": {
"text": ("STRING", {"multiline": True}),
"T5": ("T5",),
}
}
RETURN_TYPES = ("CONDITIONING",)
FUNCTION = "encode"
CATEGORY = "ExtraModels/PixArt"
TITLE = "PixArt T5 Text Encode [Reference]"
def mask_feature(self, emb, mask):
if emb.shape[0] == 1:
keep_index = mask.sum().item()
return emb[:, :, :keep_index, :], keep_index
else:
masked_feature = emb * mask[:, None, :, None]
return masked_feature, emb.shape[2]
def encode(self, text, T5):
text = text.lower().strip()
tokenizer_out = T5.tokenizer.tokenizer(
text,
max_length = 120,
padding = 'max_length',
truncation = True,
return_attention_mask = True,
add_special_tokens = True,
return_tensors = 'pt'
)
tokens = tokenizer_out["input_ids"]
mask = tokenizer_out["attention_mask"]
embs = T5.cond_stage_model.transformer(
input_ids = tokens.to(T5.load_device),
attention_mask = mask.to(T5.load_device),
)['last_hidden_state'].float()[:, None]
masked_embs, keep_index = self.mask_feature(
embs.detach().to("cpu"),
mask.detach().to("cpu")
).squeeze(0) # match CLIP/internal
print("Encoded T5:", masked_embs.shape)
return ([[masked_embs, {}]], )
NODE_CLASS_MAPPINGS = {
"PixArtCheckpointLoader" : PixArtCheckpointLoader,
"PixArtResolutionSelect" : PixArtResolutionSelect,
"PixArtDPMSampler" : PixArtDPMSampler,
"PixArtT5TextEncode" : PixArtT5TextEncode,
}
PixArt/sampler.py
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import torch
from .sampling import gaussian_diffusion as gd
from .sampling.dpm_solver import model_wrapper, DPM_Solver, NoiseScheduleVP
from comfy.sample import prepare_sampling, prepare_noise, cleanup_additional_models, get_models_from_cond
import comfy.utils
import latent_preview
def sample_pixart(model, seed, steps, cfg, noise_schedule, noise_schedule_vp, positive, negative, latent_image):
"""
Mostly just a wrapper around the reference code.
"""
# prepare model
noise = prepare_noise(latent_image, seed)
real_model, _, _, _, models = prepare_sampling(model, noise.shape, positive, negative, noise_mask=None)
# negative cond
cond = positive[0][0]
raw_uncond = negative[0][0]
# Sampler seems to want the same dim for cond and uncond
# truncate uncond to the length of cond
# if shorter, pad uncond with y_null
null_y = real_model.diffusion_model.y_embedder.y_embedding[None].repeat(latent_image.shape[0], 1, 1)
uncond = null_y[:, :cond.shape[1], :]
uncond[:, :raw_uncond.shape[1], :] = raw_uncond[:, :cond.shape[1], :]
if raw_uncond.shape[1] > cond.shape[1]:
print("PixArt: Warning. Your negative prompt is too long.")
uncond[:, -1, :] = raw_uncond[:, -1, :] # add back EOS token
# Move inputs
cond = cond.to(model.load_device).to(real_model.diffusion_model.dtype)
uncond = uncond.to(model.load_device).to(real_model.diffusion_model.dtype)
noise = noise.to(model.load_device).to(real_model.diffusion_model.dtype)
# preview
pbar = comfy.utils.ProgressBar(steps)
previewer = latent_preview.get_previewer(model.load_device, model.model.latent_format)
## Noise schedule.
betas = torch.tensor(gd.get_named_beta_schedule(noise_schedule, steps))
noise_schedule = NoiseScheduleVP(schedule=noise_schedule_vp, betas=betas)
## Convert your discrete-time `model` to the continuous-time
## noise prediction model. Here is an example for a diffusion model
## `model` with the noise prediction type ("noise") .
model_fn = model_wrapper(
real_model.diffusion_model.forward,
noise_schedule,
model_type="noise", # 'noise', "x_start", "v", "score"
model_kwargs={},
guidance_type="classifier-free",
condition=cond,
unconditional_condition=uncond,
guidance_scale=cfg,
)
dpm_solver = DPM_Solver(
model_fn,
noise_schedule,
algorithm_type="dpmsolver++"
)
samples = dpm_solver.sample(
noise,
steps=steps,
order=2,
skip_type="time_uniform",
method="multistep",
pbar=pbar,
previewer=previewer,
)
cleanup_additional_models(models)
cleanup_additional_models(set(get_models_from_cond(positive, "control")))
return samples.detach().cpu().float() * (1 / model.model.latent_format.scale_factor)
PixArt/sampling/diffusion_utils.py
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# Modified from OpenAI's diffusion repos
# GLIDE: https://github.com/openai/glide-text2im/blob/main/glide_text2im/gaussian_diffusion.py
# ADM: https://github.com/openai/guided-diffusion/blob/main/guided_diffusion
# IDDPM: https://github.com/openai/improved-diffusion/blob/main/improved_diffusion/gaussian_diffusion.py
import numpy as np
import torch as th
def normal_kl(mean1, logvar1, mean2, logvar2):
"""
Compute the KL divergence between two gaussians.
Shapes are automatically broadcasted, so batches can be compared to
scalars, among other use cases.
"""
tensor = None
for obj in (mean1, logvar1, mean2, logvar2):
if isinstance(obj, th.Tensor):
tensor = obj
break
assert tensor is not None, "at least one argument must be a Tensor"
# Force variances to be Tensors. Broadcasting helps convert scalars to
# Tensors, but it does not work for th.exp().
logvar1, logvar2 = [
x if isinstance(x, th.Tensor) else th.tensor(x, device=tensor.device)
for x in (logvar1, logvar2)
]
return 0.5 * (
-1.0
+ logvar2
- logvar1
+ th.exp(logvar1 - logvar2)
+ ((mean1 - mean2) ** 2) * th.exp(-logvar2)
)
def approx_standard_normal_cdf(x):
"""
A fast approximation of the cumulative distribution function of the
standard normal.
"""
return 0.5 * (1.0 + th.tanh(np.sqrt(2.0 / np.pi) * (x + 0.044715 * th.pow(x, 3))))
def continuous_gaussian_log_likelihood(x, *, means, log_scales):
"""
Compute the log-likelihood of a continuous Gaussian distribution.
:param x: the targets
:param means: the Gaussian mean Tensor.
:param log_scales: the Gaussian log stddev Tensor.
:return: a tensor like x of log probabilities (in nats).
"""
centered_x = x - means
inv_stdv = th.exp(-log_scales)
normalized_x = centered_x * inv_stdv
log_probs = th.distributions.Normal(th.zeros_like(x), th.ones_like(x)).log_prob(normalized_x)
return log_probs
def discretized_gaussian_log_likelihood(x, *, means, log_scales):
"""
Compute the log-likelihood of a Gaussian distribution discretizing to a
given image.
:param x: the target images. It is assumed that this was uint8 values,
rescaled to the range [-1, 1].
:param means: the Gaussian mean Tensor.
:param log_scales: the Gaussian log stddev Tensor.
:return: a tensor like x of log probabilities (in nats).
"""
assert x.shape == means.shape == log_scales.shape
centered_x = x - means
inv_stdv = th.exp(-log_scales)
plus_in = inv_stdv * (centered_x + 1.0 / 255.0)
cdf_plus = approx_standard_normal_cdf(plus_in)
min_in = inv_stdv * (centered_x - 1.0 / 255.0)
cdf_min = approx_standard_normal_cdf(min_in)
log_cdf_plus = th.log(cdf_plus.clamp(min=1e-12))
log_one_minus_cdf_min = th.log((1.0 - cdf_min).clamp(min=1e-12))
cdf_delta = cdf_plus - cdf_min
log_probs = th.where(
x < -0.999,
log_cdf_plus,
th.where(x > 0.999, log_one_minus_cdf_min, th.log(cdf_delta.clamp(min=1e-12))),
)
assert log_probs.shape == x.shape
return log_probs
PixArt/sampling/dpm_solver.py
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PixArt/sampling/gaussian_diffusion.py
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# Modified from OpenAI's diffusion repos
# GLIDE: https://github.com/openai/glide-text2im/blob/main/glide_text2im/gaussian_diffusion.py
# ADM: https://github.com/openai/guided-diffusion/blob/main/guided_diffusion
# IDDPM: https://github.com/openai/improved-diffusion/blob/main/improved_diffusion/gaussian_diffusion.py
import enum
import math
import numpy as np
import torch as th
import torch.nn.functional as F
from .diffusion_utils import discretized_gaussian_log_likelihood, normal_kl
def mean_flat(tensor):
"""
Take the mean over all non-batch dimensions.
"""
return tensor.mean(dim=list(range(1, len(tensor.shape))))
class ModelMeanType(enum.Enum):
"""
Which type of output the model predicts.
"""
PREVIOUS_X = enum.auto() # the model predicts x_{t-1}
START_X = enum.auto() # the model predicts x_0
EPSILON = enum.auto() # the model predicts epsilon
class ModelVarType(enum.Enum):
"""
What is used as the model's output variance.
The LEARNED_RANGE option has been added to allow the model to predict
values between FIXED_SMALL and FIXED_LARGE, making its job easier.
"""
LEARNED = enum.auto()
FIXED_SMALL = enum.auto()
FIXED_LARGE = enum.auto()
LEARNED_RANGE = enum.auto()
class LossType(enum.Enum):
MSE = enum.auto() # use raw MSE loss (and KL when learning variances)
RESCALED_MSE = (
enum.auto()
) # use raw MSE loss (with RESCALED_KL when learning variances)
KL = enum.auto() # use the variational lower-bound
RESCALED_KL = enum.auto() # like KL, but rescale to estimate the full VLB
def is_vb(self):
return self == LossType.KL or self == LossType.RESCALED_KL
def _warmup_beta(beta_start, beta_end, num_diffusion_timesteps, warmup_frac):
betas = beta_end * np.ones(num_diffusion_timesteps, dtype=np.float64)
warmup_time = int(num_diffusion_timesteps * warmup_frac)
betas[:warmup_time] = np.linspace(beta_start, beta_end, warmup_time, dtype=np.float64)
return betas
def get_beta_schedule(beta_schedule, *, beta_start, beta_end, num_diffusion_timesteps):
"""
This is the deprecated API for creating beta schedules.
See get_named_beta_schedule() for the new library of schedules.
"""
if beta_schedule == "quad":
betas = (
np.linspace(
beta_start ** 0.5,
beta_end ** 0.5,
num_diffusion_timesteps,
dtype=np.float64,
)
** 2
)
elif beta_schedule == "linear":
betas = np.linspace(beta_start, beta_end, num_diffusion_timesteps, dtype=np.float64)
elif beta_schedule == "warmup10":
betas = _warmup_beta(beta_start, beta_end, num_diffusion_timesteps, 0.1)
elif beta_schedule == "warmup50":
betas = _warmup_beta(beta_start, beta_end, num_diffusion_timesteps, 0.5)
elif beta_schedule == "const":
betas = beta_end * np.ones(num_diffusion_timesteps, dtype=np.float64)
elif beta_schedule == "jsd": # 1/T, 1/(T-1), 1/(T-2), ..., 1
betas = 1.0 / np.linspace(
num_diffusion_timesteps, 1, num_diffusion_timesteps, dtype=np.float64
)
else:
raise NotImplementedError(beta_schedule)
assert betas.shape == (num_diffusion_timesteps,)
return betas
def get_named_beta_schedule(schedule_name, num_diffusion_timesteps):
"""
Get a pre-defined beta schedule for the given name.
The beta schedule library consists of beta schedules which remain similar
in the limit of num_diffusion_timesteps.
Beta schedules may be added, but should not be removed or changed once
they are committed to maintain backwards compatibility.
"""
if schedule_name == "linear":
# Linear schedule from Ho et al, extended to work for any number of
# diffusion steps.
scale = 1000 / num_diffusion_timesteps
return get_beta_schedule(
"linear",
beta_start=scale * 0.0001,
beta_end=scale * 0.02,
num_diffusion_timesteps=num_diffusion_timesteps,
)
elif schedule_name == "squaredcos_cap_v2":
return betas_for_alpha_bar(
num_diffusion_timesteps,
lambda t: math.cos((t + 0.008) / 1.008 * math.pi / 2) ** 2,
)
else:
raise NotImplementedError(f"unknown beta schedule: {schedule_name}")
def betas_for_alpha_bar(num_diffusion_timesteps, alpha_bar, max_beta=0.999):
"""
Create a beta schedule that discretizes the given alpha_t_bar function,
which defines the cumulative product of (1-beta) over time from t = [0,1].
:param num_diffusion_timesteps: the number of betas to produce.
:param alpha_bar: a lambda that takes an argument t from 0 to 1 and
produces the cumulative product of (1-beta) up to that
part of the diffusion process.
:param max_beta: the maximum beta to use; use values lower than 1 to
prevent singularities.
"""
betas = []
for i in range(num_diffusion_timesteps):
t1 = i / num_diffusion_timesteps
t2 = (i + 1) / num_diffusion_timesteps
betas.append(min(1 - alpha_bar(t2) / alpha_bar(t1), max_beta))
return np.array(betas)
class GaussianDiffusion:
"""
Utilities for training and sampling diffusion models.
Original ported from this codebase:
https://github.com/hojonathanho/diffusion/blob/1e0dceb3b3495bbe19116a5e1b3596cd0706c543/diffusion_tf/diffusion_utils_2.py#L42
:param betas: a 1-D numpy array of betas for each diffusion timestep,
starting at T and going to 1.
"""
def __init__(
self,
*,
betas,
model_mean_type,
model_var_type,
loss_type,
snr=False
):
self.model_mean_type = model_mean_type
self.model_var_type = model_var_type
self.loss_type = loss_type
self.snr = snr
# Use float64 for accuracy.
betas = np.array(betas, dtype=np.float64)
self.betas = betas
assert len(betas.shape) == 1, "betas must be 1-D"
assert (betas > 0).all() and (betas <= 1).all()
self.num_timesteps = int(betas.shape[0])
alphas = 1.0 - betas
self.alphas_cumprod = np.cumprod(alphas, axis=0)
self.alphas_cumprod_prev = np.append(1.0, self.alphas_cumprod[:-1])
self.alphas_cumprod_next = np.append(self.alphas_cumprod[1:], 0.0)
assert self.alphas_cumprod_prev.shape == (self.num_timesteps,)
# calculations for diffusion q(x_t | x_{t-1}) and others
self.sqrt_alphas_cumprod = np.sqrt(self.alphas_cumprod)
self.sqrt_one_minus_alphas_cumprod = np.sqrt(1.0 - self.alphas_cumprod)
self.log_one_minus_alphas_cumprod = np.log(1.0 - self.alphas_cumprod)
self.sqrt_recip_alphas_cumprod = np.sqrt(1.0 / self.alphas_cumprod)
self.sqrt_recipm1_alphas_cumprod = np.sqrt(1.0 / self.alphas_cumprod - 1)
# calculations for posterior q(x_{t-1} | x_t, x_0)
self.posterior_variance = (
betas * (1.0 - self.alphas_cumprod_prev) / (1.0 - self.alphas_cumprod)
)
# below: log calculation clipped because the posterior variance is 0 at the beginning of the diffusion chain
self.posterior_log_variance_clipped = np.log(
np.append(self.posterior_variance[1], self.posterior_variance[1:])
) if len(self.posterior_variance) > 1 else np.array([])
self.posterior_mean_coef1 = (
betas * np.sqrt(self.alphas_cumprod_prev) / (1.0 - self.alphas_cumprod)
)
self.posterior_mean_coef2 = (
(1.0 - self.alphas_cumprod_prev) * np.sqrt(alphas) / (1.0 - self.alphas_cumprod)
)
def q_mean_variance(self, x_start, t):
"""
Get the distribution q(x_t | x_0).
:param x_start: the [N x C x ...] tensor of noiseless inputs.
:param t: the number of diffusion steps (minus 1). Here, 0 means one step.
:return: A tuple (mean, variance, log_variance), all of x_start's shape.
"""
mean = _extract_into_tensor(self.sqrt_alphas_cumprod, t, x_start.shape) * x_start
variance = _extract_into_tensor(1.0 - self.alphas_cumprod, t, x_start.shape)
log_variance = _extract_into_tensor(self.log_one_minus_alphas_cumprod, t, x_start.shape)
return mean, variance, log_variance
def q_sample(self, x_start, t, noise=None):
"""
Diffuse the data for a given number of diffusion steps.
In other words, sample from q(x_t | x_0).
:param x_start: the initial data batch.
:param t: the number of diffusion steps (minus 1). Here, 0 means one step.
:param noise: if specified, the split-out normal noise.
:return: A noisy version of x_start.
"""
if noise is None:
noise = th.randn_like(x_start)
assert noise.shape == x_start.shape
return (
_extract_into_tensor(self.sqrt_alphas_cumprod, t, x_start.shape) * x_start
+ _extract_into_tensor(self.sqrt_one_minus_alphas_cumprod, t, x_start.shape) * noise
)
def q_posterior_mean_variance(self, x_start, x_t, t):
"""
Compute the mean and variance of the diffusion posterior:
q(x_{t-1} | x_t, x_0)
"""
assert x_start.shape == x_t.shape
posterior_mean = (
_extract_into_tensor(self.posterior_mean_coef1, t, x_t.shape) * x_start
+ _extract_into_tensor(self.posterior_mean_coef2, t, x_t.shape) * x_t
)
posterior_variance = _extract_into_tensor(self.posterior_variance, t, x_t.shape)
posterior_log_variance_clipped = _extract_into_tensor(
self.posterior_log_variance_clipped, t, x_t.shape
)
assert (
posterior_mean.shape[0]
== posterior_variance.shape[0]
== posterior_log_variance_clipped.shape[0]
== x_start.shape[0]
)
return posterior_mean, posterior_variance, posterior_log_variance_clipped
def p_mean_variance(self, model, x, t, clip_denoised=True, denoised_fn=None, model_kwargs=None):
"""
Apply the model to get p(x_{t-1} | x_t), as well as a prediction of
the initial x, x_0.
:param model: the model, which takes a signal and a batch of timesteps
as input.
:param x: the [N x C x ...] tensor at time t.
:param t: a 1-D Tensor of timesteps.
:param clip_denoised: if True, clip the denoised signal into [-1, 1].
:param denoised_fn: if not None, a function which applies to the
x_start prediction before it is used to sample. Applies before
clip_denoised.
:param model_kwargs: if not None, a dict of extra keyword arguments to
pass to the model. This can be used for conditioning.
:return: a dict with the following keys:
- 'mean': the model mean output.
- 'variance': the model variance output.
- 'log_variance': the log of 'variance'.
- 'pred_xstart': the prediction for x_0.
"""
if model_kwargs is None:
model_kwargs = {}
B, C = x.shape[:2]
assert t.shape == (B,)
model_output = model(x, t, **model_kwargs)
if isinstance(model_output, tuple):
model_output, extra = model_output
else:
extra = None
if self.model_var_type in [ModelVarType.LEARNED, ModelVarType.LEARNED_RANGE]:
assert model_output.shape == (B, C * 2, *x.shape[2:])
model_output, model_var_values = th.split(model_output, C, dim=1)
min_log = _extract_into_tensor(self.posterior_log_variance_clipped, t, x.shape)
max_log = _extract_into_tensor(np.log(self.betas), t, x.shape)
# The model_var_values is [-1, 1] for [min_var, max_var].
frac = (model_var_values + 1) / 2
model_log_variance = frac * max_log + (1 - frac) * min_log
model_variance = th.exp(model_log_variance)
elif self.model_var_type in [ModelVarType.FIXED_LARGE, ModelVarType.FIXED_SMALL]:
model_variance, model_log_variance = {
# for fixedlarge, we set the initial (log-)variance like so
# to get a better decoder log likelihood.
ModelVarType.FIXED_LARGE: (
np.append(self.posterior_variance[1], self.betas[1:]),
np.log(np.append(self.posterior_variance[1], self.betas[1:])),
),
ModelVarType.FIXED_SMALL: (
self.posterior_variance,
self.posterior_log_variance_clipped,
),
}[self.model_var_type]
model_variance = _extract_into_tensor(model_variance, t, x.shape)
model_log_variance = _extract_into_tensor(model_log_variance, t, x.shape)
else:
model_variance = th.zeros_like(model_output)
model_log_variance = th.zeros_like(model_output)
def process_xstart(x):
if denoised_fn is not None:
x = denoised_fn(x)
if clip_denoised:
return x.clamp(-1, 1)
return x
if self.model_mean_type == ModelMeanType.START_X:
pred_xstart = process_xstart(model_output)
else:
pred_xstart = process_xstart(
self._predict_xstart_from_eps(x_t=x, t=t, eps=model_output)
)
model_mean, _, _ = self.q_posterior_mean_variance(x_start=pred_xstart, x_t=x, t=t)
assert model_mean.shape == model_log_variance.shape == pred_xstart.shape == x.shape
return {
"mean": model_mean,
"variance": model_variance,
"log_variance": model_log_variance,
"pred_xstart": pred_xstart,
"extra": extra,
}
def _predict_xstart_from_eps(self, x_t, t, eps):
assert x_t.shape == eps.shape
return (
_extract_into_tensor(self.sqrt_recip_alphas_cumprod, t, x_t.shape) * x_t
- _extract_into_tensor(self.sqrt_recipm1_alphas_cumprod, t, x_t.shape) * eps
)
def _predict_eps_from_xstart(self, x_t, t, pred_xstart):
return (
_extract_into_tensor(self.sqrt_recip_alphas_cumprod, t, x_t.shape) * x_t - pred_xstart
) / _extract_into_tensor(self.sqrt_recipm1_alphas_cumprod, t, x_t.shape)
def condition_mean(self, cond_fn, p_mean_var, x, t, model_kwargs=None):
"""
Compute the mean for the previous step, given a function cond_fn that
computes the gradient of a conditional log probability with respect to
x. In particular, cond_fn computes grad(log(p(y|x))), and we want to
condition on y.
This uses the conditioning strategy from Sohl-Dickstein et al. (2015).
"""
gradient = cond_fn(x, t, **model_kwargs)
new_mean = p_mean_var["mean"].float() + p_mean_var["variance"] * gradient.float()
return new_mean
def condition_score(self, cond_fn, p_mean_var, x, t, model_kwargs=None):
"""
Compute what the p_mean_variance output would have been, should the
model's score function be conditioned by cond_fn.
See condition_mean() for details on cond_fn.
Unlike condition_mean(), this instead uses the conditioning strategy
from Song et al (2020).
"""
alpha_bar = _extract_into_tensor(self.alphas_cumprod, t, x.shape)
eps = self._predict_eps_from_xstart(x, t, p_mean_var["pred_xstart"])
eps = eps - (1 - alpha_bar).sqrt() * cond_fn(x, t, **model_kwargs)
out = p_mean_var.copy()
out["pred_xstart"] = self._predict_xstart_from_eps(x, t, eps)
out["mean"], _, _ = self.q_posterior_mean_variance(x_start=out["pred_xstart"], x_t=x, t=t)
return out
def p_sample(
self,
model,
x,
t,
clip_denoised=True,
denoised_fn=None,
cond_fn=None,
model_kwargs=None,
):
"""
Sample x_{t-1} from the model at the given timestep.
:param model: the model to sample from.
:param x: the current tensor at x_{t-1}.
:param t: the value of t, starting at 0 for the first diffusion step.
:param clip_denoised: if True, clip the x_start prediction to [-1, 1].
:param denoised_fn: if not None, a function which applies to the
x_start prediction before it is used to sample.
:param cond_fn: if not None, this is a gradient function that acts
similarly to the model.
:param model_kwargs: if not None, a dict of extra keyword arguments to
pass to the model. This can be used for conditioning.
:return: a dict containing the following keys:
- 'sample': a random sample from the model.
- 'pred_xstart': a prediction of x_0.
"""
out = self.p_mean_variance(
model,
x,
t,
clip_denoised=clip_denoised,
denoised_fn=denoised_fn,
model_kwargs=model_kwargs,
)
noise = th.randn_like(x)
nonzero_mask = (
(t != 0).float().view(-1, *([1] * (len(x.shape) - 1)))
) # no noise when t == 0
if cond_fn is not None:
out["mean"] = self.condition_mean(cond_fn, out, x, t, model_kwargs=model_kwargs)
sample = out["mean"] + nonzero_mask * th.exp(0.5 * out["log_variance"]) * noise
return {"sample": sample, "pred_xstart": out["pred_xstart"]}
def p_sample_loop(
self,
model,
shape,
noise=None,
clip_denoised=True,
denoised_fn=None,
cond_fn=None,
model_kwargs=None,
device=None,
progress=False,
):
"""
Generate samples from the model.
:param model: the model module.
:param shape: the shape of the samples, (N, C, H, W).
:param noise: if specified, the noise from the encoder to sample.
Should be of the same shape as `shape`.
:param clip_denoised: if True, clip x_start predictions to [-1, 1].
:param denoised_fn: if not None, a function which applies to the
x_start prediction before it is used to sample.
:param cond_fn: if not None, this is a gradient function that acts
similarly to the model.
:param model_kwargs: if not None, a dict of extra keyword arguments to
pass to the model. This can be used for conditioning.
:param device: if specified, the device to create the samples on.
If not specified, use a model parameter's device.
:param progress: if True, show a tqdm progress bar.
:return: a non-differentiable batch of samples.
"""
final = None
for sample in self.p_sample_loop_progressive(
model,
shape,
noise=noise,
clip_denoised=clip_denoised,
denoised_fn=denoised_fn,
cond_fn=cond_fn,
model_kwargs=model_kwargs,
device=device,
progress=progress,
):
final = sample
return final["sample"]
def p_sample_loop_progressive(
self,
model,
shape,
noise=None,
clip_denoised=True,
denoised_fn=None,
cond_fn=None,
model_kwargs=None,
device=None,
progress=False,
):
"""
Generate samples from the model and yield intermediate samples from
each timestep of diffusion.
Arguments are the same as p_sample_loop().
Returns a generator over dicts, where each dict is the return value of
p_sample().
"""
if device is None:
device = next(model.parameters()).device
assert isinstance(shape, (tuple, list))
if noise is not None:
img = noise
else:
img = th.randn(*shape, device=device)
indices = list(range(self.num_timesteps))[::-1]
if progress:
# Lazy import so that we don't depend on tqdm.
from tqdm.auto import tqdm
indices = tqdm(indices)
for i in indices:
t = th.tensor([i] * shape[0], device=device)
with th.no_grad():
out = self.p_sample(
model,
img,
t,
clip_denoised=clip_denoised,
denoised_fn=denoised_fn,
cond_fn=cond_fn,
model_kwargs=model_kwargs,
)
yield out
img = out["sample"]
def ddim_sample(
self,
model,
x,
t,
clip_denoised=True,
denoised_fn=None,
cond_fn=None,
model_kwargs=None,
eta=0.0,
):
"""
Sample x_{t-1} from the model using DDIM.
Same usage as p_sample().
"""
out = self.p_mean_variance(
model,
x,
t,
clip_denoised=clip_denoised,
denoised_fn=denoised_fn,
model_kwargs=model_kwargs,
)
if cond_fn is not None:
out = self.condition_score(cond_fn, out, x, t, model_kwargs=model_kwargs)
# Usually our model outputs epsilon, but we re-derive it
# in case we used x_start or x_prev prediction.
eps = self._predict_eps_from_xstart(x, t, out["pred_xstart"])
alpha_bar = _extract_into_tensor(self.alphas_cumprod, t, x.shape)
alpha_bar_prev = _extract_into_tensor(self.alphas_cumprod_prev, t, x.shape)
sigma = (
eta
* th.sqrt((1 - alpha_bar_prev) / (1 - alpha_bar))
* th.sqrt(1 - alpha_bar / alpha_bar_prev)
)
# Equation 12.
noise = th.randn_like(x)
mean_pred = (
out["pred_xstart"] * th.sqrt(alpha_bar_prev)
+ th.sqrt(1 - alpha_bar_prev - sigma ** 2) * eps
)
nonzero_mask = (
(t != 0).float().view(-1, *([1] * (len(x.shape) - 1)))
) # no noise when t == 0
sample = mean_pred + nonzero_mask * sigma * noise
return {"sample": sample, "pred_xstart": out["pred_xstart"]}
def ddim_reverse_sample(
self,
model,
x,
t,
clip_denoised=True,
denoised_fn=None,
cond_fn=None,
model_kwargs=None,
eta=0.0,
):
"""
Sample x_{t+1} from the model using DDIM reverse ODE.
"""
assert eta == 0.0, "Reverse ODE only for deterministic path"
out = self.p_mean_variance(
model,
x,
t,
clip_denoised=clip_denoised,
denoised_fn=denoised_fn,
model_kwargs=model_kwargs,
)
if cond_fn is not None:
out = self.condition_score(cond_fn, out, x, t, model_kwargs=model_kwargs)
# Usually our model outputs epsilon, but we re-derive it
# in case we used x_start or x_prev prediction.
eps = (
_extract_into_tensor(self.sqrt_recip_alphas_cumprod, t, x.shape) * x
- out["pred_xstart"]
) / _extract_into_tensor(self.sqrt_recipm1_alphas_cumprod, t, x.shape)
alpha_bar_next = _extract_into_tensor(self.alphas_cumprod_next, t, x.shape)
# Equation 12. reversed
mean_pred = out["pred_xstart"] * th.sqrt(alpha_bar_next) + th.sqrt(1 - alpha_bar_next) * eps
return {"sample": mean_pred, "pred_xstart": out["pred_xstart"]}
def ddim_sample_loop(
self,
model,
shape,
noise=None,
clip_denoised=True,
denoised_fn=None,
cond_fn=None,
model_kwargs=None,
device=None,
progress=False,
eta=0.0,
):
"""
Generate samples from the model using DDIM.
Same usage as p_sample_loop().
"""
final = None
for sample in self.ddim_sample_loop_progressive(
model,
shape,
noise=noise,
clip_denoised=clip_denoised,
denoised_fn=denoised_fn,
cond_fn=cond_fn,
model_kwargs=model_kwargs,
device=device,
progress=progress,
eta=eta,
):
final = sample
return final["sample"]
def ddim_sample_loop_progressive(
self,
model,
shape,
noise=None,
clip_denoised=True,
denoised_fn=None,
cond_fn=None,
model_kwargs=None,
device=None,
progress=False,
eta=0.0,
):
"""
Use DDIM to sample from the model and yield intermediate samples from
each timestep of DDIM.
Same usage as p_sample_loop_progressive().
"""
if device is None:
device = next(model.parameters()).device
assert isinstance(shape, (tuple, list))
if noise is not None:
img = noise
else:
img = th.randn(*shape, device=device)
indices = list(range(self.num_timesteps))[::-1]
if progress:
# Lazy import so that we don't depend on tqdm.
from tqdm.auto import tqdm
indices = tqdm(indices)
for i in indices:
t = th.tensor([i] * shape[0], device=device)
with th.no_grad():
out = self.ddim_sample(
model,
img,
t,
clip_denoised=clip_denoised,
denoised_fn=denoised_fn,
cond_fn=cond_fn,
model_kwargs=model_kwargs,
eta=eta,
)
yield out
img = out["sample"]
def _vb_terms_bpd(
self, model, x_start, x_t, t, clip_denoised=True, model_kwargs=None
):
"""
Get a term for the variational lower-bound.
The resulting units are bits (rather than nats, as one might expect).
This allows for comparison to other papers.
:return: a dict with the following keys:
- 'output': a shape [N] tensor of NLLs or KLs.
- 'pred_xstart': the x_0 predictions.
"""
true_mean, _, true_log_variance_clipped = self.q_posterior_mean_variance(
x_start=x_start, x_t=x_t, t=t
)
out = self.p_mean_variance(
model, x_t, t, clip_denoised=clip_denoised, model_kwargs=model_kwargs
)
kl = normal_kl(
true_mean, true_log_variance_clipped, out["mean"], out["log_variance"]
)
kl = mean_flat(kl) / np.log(2.0)
decoder_nll = -discretized_gaussian_log_likelihood(
x_start, means=out["mean"], log_scales=0.5 * out["log_variance"]
)
assert decoder_nll.shape == x_start.shape
decoder_nll = mean_flat(decoder_nll) / np.log(2.0)
# At the first timestep return the decoder NLL,
# otherwise return KL(q(x_{t-1}|x_t,x_0) || p(x_{t-1}|x_t))
output = th.where((t == 0), decoder_nll, kl)
return {"output": output, "pred_xstart": out["pred_xstart"]}
def training_losses(self, model, x_start, t, model_kwargs=None, noise=None):
"""
Compute training losses for a single timestep.
:param model: the model to evaluate loss on.
:param x_start: the [N x C x ...] tensor of inputs.
:param t: a batch of timestep indices.
:param model_kwargs: if not None, a dict of extra keyword arguments to
pass to the model. This can be used for conditioning.
:param noise: if specified, the specific Gaussian noise to try to remove.
:return: a dict with the key "loss" containing a tensor of shape [N].
Some mean or variance settings may also have other keys.
"""
if model_kwargs is None:
model_kwargs = {}
if noise is None:
noise = th.randn_like(x_start)
x_t = self.q_sample(x_start, t, noise=noise)
terms = {}
if self.loss_type == LossType.KL or self.loss_type == LossType.RESCALED_KL:
terms["loss"] = self._vb_terms_bpd(
model=model,
x_start=x_start,
x_t=x_t,
t=t,
clip_denoised=False,
model_kwargs=model_kwargs,
)["output"]
if self.loss_type == LossType.RESCALED_KL:
terms["loss"] *= self.num_timesteps
elif self.loss_type == LossType.MSE or self.loss_type == LossType.RESCALED_MSE:
model_output = model(x_t, t, **model_kwargs)
if isinstance(model_output, dict) and model_output.get('x', None) is not None:
output = model_output['x']
else:
output = model_output
if self.model_var_type in [
ModelVarType.LEARNED,
ModelVarType.LEARNED_RANGE,
]:
B, C = x_t.shape[:2]
assert output.shape == (B, C * 2, *x_t.shape[2:])
output, model_var_values = th.split(output, C, dim=1)
# Learn the variance using the variational bound, but don't let it affect our mean prediction.
frozen_out = th.cat([output.detach(), model_var_values], dim=1)
terms["vb"] = self._vb_terms_bpd(
model=lambda *args, r=frozen_out: r,
x_start=x_start,
x_t=x_t,
t=t,
clip_denoised=False,
)["output"]
if self.loss_type == LossType.RESCALED_MSE:
# Divide by 1000 for equivalence with initial implementation.
# Without a factor of 1/1000, the VB term hurts the MSE term.
terms["vb"] *= self.num_timesteps / 1000.0
target = {
ModelMeanType.PREVIOUS_X: self.q_posterior_mean_variance(
x_start=x_start, x_t=x_t, t=t
)[0],
ModelMeanType.START_X: x_start,
ModelMeanType.EPSILON: noise,
}[self.model_mean_type]
assert output.shape == target.shape == x_start.shape
if self.snr:
if self.model_mean_type == ModelMeanType.START_X:
pred_noise = self._predict_eps_from_xstart(x_t=x_t, t=t, pred_xstart=output)
pred_startx = output
elif self.model_mean_type == ModelMeanType.EPSILON:
pred_noise = output
pred_startx = self._predict_xstart_from_eps(x_t=x_t, t=t, eps=output)
# terms["mse_eps"] = mean_flat((noise - pred_noise) ** 2)
# terms["mse_x0"] = mean_flat((x_start - pred_startx) ** 2)
t = t[:, None, None, None].expand(pred_startx.shape) # [128, 4, 32, 32]
# best
target = th.where(t > 249, noise, x_start)
output = th.where(t > 249, pred_noise, pred_startx)
loss = (target - output) ** 2
if model_kwargs.get('mask_ratio', False) and model_kwargs['mask_ratio'] > 0:
assert 'mask' in model_output
loss = F.avg_pool2d(loss.mean(dim=1), model.model.module.patch_size).flatten(1)
mask = model_output['mask']
unmask = 1 - mask
terms['mse'] = mean_flat(loss * unmask) * unmask.shape[1]/unmask.sum(1)
if model_kwargs['mask_loss_coef'] > 0:
terms['mae'] = model_kwargs['mask_loss_coef'] * mean_flat(loss * mask) * mask.shape[1]/mask.sum(1)
else:
terms["mse"] = mean_flat(loss)
if "vb" in terms:
terms["loss"] = terms["mse"] + terms["vb"]
else:
terms["loss"] = terms["mse"]
if "mae" in terms:
terms["loss"] = terms["loss"] + terms["mae"]
else:
raise NotImplementedError(self.loss_type)
return terms
def _prior_bpd(self, x_start):
"""
Get the prior KL term for the variational lower-bound, measured in
bits-per-dim.
This term can't be optimized, as it only depends on the encoder.
:param x_start: the [N x C x ...] tensor of inputs.
:return: a batch of [N] KL values (in bits), one per batch element.
"""
batch_size = x_start.shape[0]
t = th.tensor([self.num_timesteps - 1] * batch_size, device=x_start.device)
qt_mean, _, qt_log_variance = self.q_mean_variance(x_start, t)
kl_prior = normal_kl(
mean1=qt_mean, logvar1=qt_log_variance, mean2=0.0, logvar2=0.0
)
return mean_flat(kl_prior) / np.log(2.0)
def calc_bpd_loop(self, model, x_start, clip_denoised=True, model_kwargs=None):
"""
Compute the entire variational lower-bound, measured in bits-per-dim,
as well as other related quantities.
:param model: the model to evaluate loss on.
:param x_start: the [N x C x ...] tensor of inputs.
:param clip_denoised: if True, clip denoised samples.
:param model_kwargs: if not None, a dict of extra keyword arguments to
pass to the model. This can be used for conditioning.
:return: a dict containing the following keys:
- total_bpd: the total variational lower-bound, per batch element.
- prior_bpd: the prior term in the lower-bound.
- vb: an [N x T] tensor of terms in the lower-bound.
- xstart_mse: an [N x T] tensor of x_0 MSEs for each timestep.
- mse: an [N x T] tensor of epsilon MSEs for each timestep.
"""
device = x_start.device
batch_size = x_start.shape[0]
vb = []
xstart_mse = []
mse = []
for t in list(range(self.num_timesteps))[::-1]:
t_batch = th.tensor([t] * batch_size, device=device)
noise = th.randn_like(x_start)
x_t = self.q_sample(x_start=x_start, t=t_batch, noise=noise)
# Calculate VLB term at the current timestep
with th.no_grad():
out = self._vb_terms_bpd(
model,
x_start=x_start,
x_t=x_t,
t=t_batch,
clip_denoised=clip_denoised,
model_kwargs=model_kwargs,
)
vb.append(out["output"])
xstart_mse.append(mean_flat((out["pred_xstart"] - x_start) ** 2))
eps = self._predict_eps_from_xstart(x_t, t_batch, out["pred_xstart"])
mse.append(mean_flat((eps - noise) ** 2))
vb = th.stack(vb, dim=1)
xstart_mse = th.stack(xstart_mse, dim=1)
mse = th.stack(mse, dim=1)
prior_bpd = self._prior_bpd(x_start)
total_bpd = vb.sum(dim=1) + prior_bpd
return {
"total_bpd": total_bpd,
"prior_bpd": prior_bpd,
"vb": vb,
"xstart_mse": xstart_mse,
"mse": mse,
}
def _extract_into_tensor(arr, timesteps, broadcast_shape):
"""
Extract values from a 1-D numpy array for a batch of indices.
:param arr: the 1-D numpy array.
:param timesteps: a tensor of indices into the array to extract.
:param broadcast_shape: a larger shape of K dimensions with the batch
dimension equal to the length of timesteps.
:return: a tensor of shape [batch_size, 1, ...] where the shape has K dims.
"""
res = th.from_numpy(arr).to(device=timesteps.device)[timesteps].float()
while len(res.shape) < len(broadcast_shape):
res = res[..., None]
return res + th.zeros(broadcast_shape, device=timesteps.device)
__init__.py
+4
View File
@@ -14,6 +14,10 @@ else:
from .DiT.nodes import NODE_CLASS_MAPPINGS as DiT_Nodes
NODE_CLASS_MAPPINGS.update(DiT_Nodes)
# PixArt
from .PixArt.nodes import NODE_CLASS_MAPPINGS as PixArt_Nodes
NODE_CLASS_MAPPINGS.update(PixArt_Nodes)
# T5
from .T5.nodes import NODE_CLASS_MAPPINGS as T5_Nodes
NODE_CLASS_MAPPINGS.update(T5_Nodes)
requirements.txt
+1
View File
@@ -0,0 +1 @@
timm==0.6.13