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# Copyright 2024 The HuggingFace Team. All rights reserved.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
from typing import Any, Dict, Optional
import torch
import torch.nn.functional as F
from torch import nn
from ...configuration_utils import ConfigMixin, register_to_config
from ...utils import is_torch_version, logging
from ..attention import BasicTransformerBlock
from ..embeddings import PatchEmbed
from ..modeling_outputs import Transformer2DModelOutput
from ..modeling_utils import ModelMixin
logger = logging.get_logger(__name__) # pylint: disable=invalid-name
class DiTTransformer2DModel(ModelMixin, ConfigMixin):
r"""
A 2D Transformer model as introduced in DiT (https://arxiv.org/abs/2212.09748).
Parameters:
num_attention_heads (int, optional, defaults to 16): The number of heads to use for multi-head attention.
attention_head_dim (int, optional, defaults to 72): The number of channels in each head.
in_channels (int, defaults to 4): The number of channels in the input.
out_channels (int, optional):
The number of channels in the output. Specify this parameter if the output channel number differs from the
input.
num_layers (int, optional, defaults to 28): The number of layers of Transformer blocks to use.
dropout (float, optional, defaults to 0.0): The dropout probability to use within the Transformer blocks.
norm_num_groups (int, optional, defaults to 32):
Number of groups for group normalization within Transformer blocks.
attention_bias (bool, optional, defaults to True):
Configure if the Transformer blocks' attention should contain a bias parameter.
sample_size (int, defaults to 32):
The width of the latent images. This parameter is fixed during training.
patch_size (int, defaults to 2):
Size of the patches the model processes, relevant for architectures working on non-sequential data.
activation_fn (str, optional, defaults to "gelu-approximate"):
Activation function to use in feed-forward networks within Transformer blocks.
num_embeds_ada_norm (int, optional, defaults to 1000):
Number of embeddings for AdaLayerNorm, fixed during training and affects the maximum denoising steps during
inference.
upcast_attention (bool, optional, defaults to False):
If true, upcasts the attention mechanism dimensions for potentially improved performance.
norm_type (str, optional, defaults to "ada_norm_zero"):
Specifies the type of normalization used, can be 'ada_norm_zero'.
norm_elementwise_affine (bool, optional, defaults to False):
If true, enables element-wise affine parameters in the normalization layers.
norm_eps (float, optional, defaults to 1e-5):
A small constant added to the denominator in normalization layers to prevent division by zero.
"""
_supports_gradient_checkpointing = True
@register_to_config
def __init__(
self,
num_attention_heads: int = 16,
attention_head_dim: int = 72,
in_channels: int = 4,
out_channels: Optional[int] = None,
num_layers: int = 28,
dropout: float = 0.0,
norm_num_groups: int = 32,
attention_bias: bool = True,
sample_size: int = 32,
patch_size: int = 2,
activation_fn: str = "gelu-approximate",
num_embeds_ada_norm: Optional[int] = 1000,
upcast_attention: bool = False,
norm_type: str = "ada_norm_zero",
norm_elementwise_affine: bool = False,
norm_eps: float = 1e-5,
):
super().__init__()
# Validate inputs.
if norm_type != "ada_norm_zero":
raise NotImplementedError(
f"Forward pass is not implemented when `patch_size` is not None and `norm_type` is '{norm_type}'."
)
elif norm_type == "ada_norm_zero" and num_embeds_ada_norm is None:
raise ValueError(
f"When using a `patch_size` and this `norm_type` ({norm_type}), `num_embeds_ada_norm` cannot be None."
)
# Set some common variables used across the board.
self.attention_head_dim = attention_head_dim
self.inner_dim = self.config.num_attention_heads * self.config.attention_head_dim
self.out_channels = in_channels if out_channels is None else out_channels
self.gradient_checkpointing = False
# 2. Initialize the position embedding and transformer blocks.
self.height = self.config.sample_size
self.width = self.config.sample_size
self.patch_size = self.config.patch_size
self.pos_embed = PatchEmbed(
height=self.config.sample_size,
width=self.config.sample_size,
patch_size=self.config.patch_size,
in_channels=self.config.in_channels,
embed_dim=self.inner_dim,
)
self.transformer_blocks = nn.ModuleList(
[
BasicTransformerBlock(
self.inner_dim,
self.config.num_attention_heads,
self.config.attention_head_dim,
dropout=self.config.dropout,
activation_fn=self.config.activation_fn,
num_embeds_ada_norm=self.config.num_embeds_ada_norm,
attention_bias=self.config.attention_bias,
upcast_attention=self.config.upcast_attention,
norm_type=norm_type,
norm_elementwise_affine=self.config.norm_elementwise_affine,
norm_eps=self.config.norm_eps,
)
for _ in range(self.config.num_layers)
]
)
# 3. Output blocks.
self.norm_out = nn.LayerNorm(self.inner_dim, elementwise_affine=False, eps=1e-6)
self.proj_out_1 = nn.Linear(self.inner_dim, 2 * self.inner_dim)
self.proj_out_2 = nn.Linear(
self.inner_dim, self.config.patch_size * self.config.patch_size * self.out_channels
)
def _set_gradient_checkpointing(self, module, value=False):
if hasattr(module, "gradient_checkpointing"):
module.gradient_checkpointing = value
def forward(
self,
hidden_states: torch.Tensor,
timestep: Optional[torch.LongTensor] = None,
class_labels: Optional[torch.LongTensor] = None,
cross_attention_kwargs: Dict[str, Any] = None,
return_dict: bool = True,
):
"""
The [`DiTTransformer2DModel`] forward method.
Args:
hidden_states (`torch.LongTensor` of shape `(batch size, num latent pixels)` if discrete, `torch.FloatTensor` of shape `(batch size, channel, height, width)` if continuous):
Input `hidden_states`.
timestep ( `torch.LongTensor`, *optional*):
Used to indicate denoising step. Optional timestep to be applied as an embedding in `AdaLayerNorm`.
class_labels ( `torch.LongTensor` of shape `(batch size, num classes)`, *optional*):
Used to indicate class labels conditioning. Optional class labels to be applied as an embedding in
`AdaLayerZeroNorm`.
cross_attention_kwargs ( `Dict[str, Any]`, *optional*):
A kwargs dictionary that if specified is passed along to the `AttentionProcessor` as defined under
`self.processor` in
[diffusers.models.attention_processor](https://github.com/huggingface/diffusers/blob/main/src/diffusers/models/attention_processor.py).
return_dict (`bool`, *optional*, defaults to `True`):
Whether or not to return a [`~models.unets.unet_2d_condition.UNet2DConditionOutput`] instead of a plain
tuple.
Returns:
If `return_dict` is True, an [`~models.transformer_2d.Transformer2DModelOutput`] is returned, otherwise a
`tuple` where the first element is the sample tensor.
"""
# 1. Input
height, width = hidden_states.shape[-2] // self.patch_size, hidden_states.shape[-1] // self.patch_size
hidden_states = self.pos_embed(hidden_states)
# 2. Blocks
for block in self.transformer_blocks:
if self.training and self.gradient_checkpointing:
def create_custom_forward(module, return_dict=None):
def custom_forward(*inputs):
if return_dict is not None:
return module(*inputs, return_dict=return_dict)
else:
return module(*inputs)
return custom_forward
ckpt_kwargs: Dict[str, Any] = {"use_reentrant": False} if is_torch_version(">=", "1.11.0") else {}
hidden_states = torch.utils.checkpoint.checkpoint(
create_custom_forward(block),
hidden_states,
None,
None,
None,
timestep,
cross_attention_kwargs,
class_labels,
**ckpt_kwargs,
)
else:
hidden_states = block(
hidden_states,
attention_mask=None,
encoder_hidden_states=None,
encoder_attention_mask=None,
timestep=timestep,
cross_attention_kwargs=cross_attention_kwargs,
class_labels=class_labels,
)
# 3. Output
conditioning = self.transformer_blocks[0].norm1.emb(timestep, class_labels, hidden_dtype=hidden_states.dtype)
shift, scale = self.proj_out_1(F.silu(conditioning)).chunk(2, dim=1)
hidden_states = self.norm_out(hidden_states) * (1 + scale[:, None]) + shift[:, None]
hidden_states = self.proj_out_2(hidden_states)
# unpatchify
height = width = int(hidden_states.shape[1] ** 0.5)
hidden_states = hidden_states.reshape(
shape=(-1, height, width, self.patch_size, self.patch_size, self.out_channels)
)
hidden_states = torch.einsum("nhwpqc->nchpwq", hidden_states)
output = hidden_states.reshape(
shape=(-1, self.out_channels, height * self.patch_size, width * self.patch_size)
)
if not return_dict:
return (output,)
return Transformer2DModelOutput(sample=output)
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