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# pylint: disable=E1101
# src/models/transformer_2d.py
"""
This module defines the Transformer2DModel, a PyTorch model that extends ModelMixin and ConfigMixin. It includes
methods for gradient checkpointing, forward propagation, and various utility functions. The model is designed for
2D image-related tasks and uses LoRa (Low-Rank All-Attention) compatible layers for efficient attention computation.
The file includes the following import statements:
- From dataclasses import dataclass
- From typing import Any, Dict, Optional
- Import torch
- From diffusers.configuration_utils import ConfigMixin, register_to_config
- From diffusers.models.lora import LoRACompatibleConv, LoRACompatibleLinear
- From diffusers.models.modeling_utils import ModelMixin
- From diffusers.models.normalization import AdaLayerNormSingle
- From diffusers.utils import (USE_PEFT_BACKEND, BaseOutput, deprecate,
is_torch_version)
- From torch import nn
- From .attention import BasicTransformerBlock
The file also includes the following classes and functions:
- Transformer2DModel: A model class that extends ModelMixin and ConfigMixin. It includes methods for gradient
checkpointing, forward propagation, and various utility functions.
- _set_gradient_checkpointing: A utility function to set gradient checkpointing for a given module.
- forward: The forward propagation method for the Transformer2DModel.
To use this module, you can import the Transformer2DModel class and create an instance of the model with the desired
configuration. Then, you can use the forward method to pass input tensors through the model and get the output tensors.
"""
from dataclasses import dataclass
from typing import Any, Dict, Optional
import torch
from diffusers.configuration_utils import ConfigMixin, register_to_config
# from diffusers.models.embeddings import CaptionProjection
from diffusers.models.lora import LoRACompatibleConv, LoRACompatibleLinear
from diffusers.models.modeling_utils import ModelMixin
from diffusers.models.normalization import AdaLayerNormSingle
from diffusers.utils import (USE_PEFT_BACKEND, BaseOutput, deprecate,
is_torch_version)
from torch import nn
from .attention import BasicTransformerBlock
@dataclass
class Transformer2DModelOutput(BaseOutput):
"""
The output of [`Transformer2DModel`].
Args:
sample (`torch.FloatTensor` of shape `(batch_size, num_channels, height, width)`
or `(batch size, num_vector_embeds - 1, num_latent_pixels)` if [`Transformer2DModel`] is discrete):
The hidden states output conditioned on the `encoder_hidden_states` input. If discrete, returns probability
distributions for the unnoised latent pixels.
"""
sample: torch.FloatTensor
ref_feature: torch.FloatTensor
class Transformer2DModel(ModelMixin, ConfigMixin):
"""
A 2D Transformer model for image-like data.
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 88): The number of channels in each head.
in_channels (`int`, *optional*):
The number of channels in the input and output (specify if the input is **continuous**).
num_layers (`int`, *optional*, defaults to 1): The number of layers of Transformer blocks to use.
dropout (`float`, *optional*, defaults to 0.0): The dropout probability to use.
cross_attention_dim (`int`, *optional*): The number of `encoder_hidden_states` dimensions to use.
sample_size (`int`, *optional*): The width of the latent images (specify if the input is **discrete**).
This is fixed during training since it is used to learn a number of position embeddings.
num_vector_embeds (`int`, *optional*):
The number of classes of the vector embeddings of the latent pixels (specify if the input is **discrete**).
Includes the class for the masked latent pixel.
activation_fn (`str`, *optional*, defaults to `"geglu"`): Activation function to use in feed-forward.
num_embeds_ada_norm ( `int`, *optional*):
The number of diffusion steps used during training. Pass if at least one of the norm_layers is
`AdaLayerNorm`. This is fixed during training since it is used to learn a number of embeddings that are
added to the hidden states.
During inference, you can denoise for up to but not more steps than `num_embeds_ada_norm`.
attention_bias (`bool`, *optional*):
Configure if the `TransformerBlocks` attention should contain a bias parameter.
"""
_supports_gradient_checkpointing = True
@register_to_config
def __init__(
self,
num_attention_heads: int = 16,
attention_head_dim: int = 88,
in_channels: Optional[int] = None,
out_channels: Optional[int] = None,
num_layers: int = 1,
dropout: float = 0.0,
norm_num_groups: int = 32,
cross_attention_dim: Optional[int] = None,
attention_bias: bool = False,
num_vector_embeds: Optional[int] = None,
patch_size: Optional[int] = None,
activation_fn: str = "geglu",
num_embeds_ada_norm: Optional[int] = None,
use_linear_projection: bool = False,
only_cross_attention: bool = False,
double_self_attention: bool = False,
upcast_attention: bool = False,
norm_type: str = "layer_norm",
norm_elementwise_affine: bool = True,
norm_eps: float = 1e-5,
attention_type: str = "default",
):
super().__init__()
self.use_linear_projection = use_linear_projection
self.num_attention_heads = num_attention_heads
self.attention_head_dim = attention_head_dim
inner_dim = num_attention_heads * attention_head_dim
conv_cls = nn.Conv2d if USE_PEFT_BACKEND else LoRACompatibleConv
linear_cls = nn.Linear if USE_PEFT_BACKEND else LoRACompatibleLinear
# 1. Transformer2DModel can process both standard continuous images of
# shape `(batch_size, num_channels, width, height)` as well as quantized image embeddings of
# shape `(batch_size, num_image_vectors)`
# Define whether input is continuous or discrete depending on configuration
self.is_input_continuous = (in_channels is not None) and (patch_size is None)
self.is_input_vectorized = num_vector_embeds is not None
self.is_input_patches = in_channels is not None and patch_size is not None
if norm_type == "layer_norm" and num_embeds_ada_norm is not None:
deprecation_message = (
f"The configuration file of this model: {self.__class__} is outdated. `norm_type` is either not set or"
" incorrectly set to `'layer_norm'`.Make sure to set `norm_type` to `'ada_norm'` in the config."
" Please make sure to update the config accordingly as leaving `norm_type` might led to incorrect"
" results in future versions. If you have downloaded this checkpoint from the Hugging Face Hub, it"
" would be very nice if you could open a Pull request for the `transformer/config.json` file"
)
deprecate(
"norm_type!=num_embeds_ada_norm",
"1.0.0",
deprecation_message,
standard_warn=False,
)
norm_type = "ada_norm"
if self.is_input_continuous and self.is_input_vectorized:
raise ValueError(
f"Cannot define both `in_channels`: {in_channels} and `num_vector_embeds`: {num_vector_embeds}. Make"
" sure that either `in_channels` or `num_vector_embeds` is None."
)
if self.is_input_vectorized and self.is_input_patches:
raise ValueError(
f"Cannot define both `num_vector_embeds`: {num_vector_embeds} and `patch_size`: {patch_size}. Make"
" sure that either `num_vector_embeds` or `num_patches` is None."
)
if (
not self.is_input_continuous
and not self.is_input_vectorized
and not self.is_input_patches
):
raise ValueError(
f"Has to define `in_channels`: {in_channels}, `num_vector_embeds`: {num_vector_embeds}, or patch_size:"
f" {patch_size}. Make sure that `in_channels`, `num_vector_embeds` or `num_patches` is not None."
)
# 2. Define input layers
self.in_channels = in_channels
self.norm = torch.nn.GroupNorm(
num_groups=norm_num_groups,
num_channels=in_channels,
eps=1e-6,
affine=True,
)
if use_linear_projection:
self.proj_in = linear_cls(in_channels, inner_dim)
else:
self.proj_in = conv_cls(
in_channels, inner_dim, kernel_size=1, stride=1, padding=0
)
# 3. Define transformers blocks
self.transformer_blocks = nn.ModuleList(
[
BasicTransformerBlock(
inner_dim,
num_attention_heads,
attention_head_dim,
dropout=dropout,
cross_attention_dim=cross_attention_dim,
activation_fn=activation_fn,
num_embeds_ada_norm=num_embeds_ada_norm,
attention_bias=attention_bias,
only_cross_attention=only_cross_attention,
double_self_attention=double_self_attention,
upcast_attention=upcast_attention,
norm_type=norm_type,
norm_elementwise_affine=norm_elementwise_affine,
norm_eps=norm_eps,
attention_type=attention_type,
)
for d in range(num_layers)
]
)
# 4. Define output layers
self.out_channels = in_channels if out_channels is None else out_channels
# TODO: should use out_channels for continuous projections
if use_linear_projection:
self.proj_out = linear_cls(inner_dim, in_channels)
else:
self.proj_out = conv_cls(
inner_dim, in_channels, kernel_size=1, stride=1, padding=0
)
# 5. PixArt-Alpha blocks.
self.adaln_single = None
self.use_additional_conditions = False
if norm_type == "ada_norm_single":
self.use_additional_conditions = self.config.sample_size == 128
# TODO(Sayak, PVP) clean this, for now we use sample size to determine whether to use
# additional conditions until we find better name
self.adaln_single = AdaLayerNormSingle(
inner_dim, use_additional_conditions=self.use_additional_conditions
)
self.caption_projection = None
self.gradient_checkpointing = False
def _set_gradient_checkpointing(self, module, value=False):
if hasattr(module, "gradient_checkpointing"):
module.gradient_checkpointing = value
def forward(
self,
hidden_states: torch.Tensor,
encoder_hidden_states: Optional[torch.Tensor] = None,
timestep: Optional[torch.LongTensor] = None,
_added_cond_kwargs: Dict[str, torch.Tensor] = None,
class_labels: Optional[torch.LongTensor] = None,
cross_attention_kwargs: Dict[str, Any] = None,
attention_mask: Optional[torch.Tensor] = None,
encoder_attention_mask: Optional[torch.Tensor] = None,
return_dict: bool = True,
):
"""
The [`Transformer2DModel`] 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`.
encoder_hidden_states ( `torch.FloatTensor` of shape `(batch size, sequence len, embed dims)`, *optional*):
Conditional embeddings for cross attention layer. If not given, cross-attention defaults to
self-attention.
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).
attention_mask ( `torch.Tensor`, *optional*):
An attention mask of shape `(batch, key_tokens)` is applied to `encoder_hidden_states`. If `1` the mask
is kept, otherwise if `0` it is discarded. Mask will be converted into a bias, which adds large
negative values to the attention scores corresponding to "discard" tokens.
encoder_attention_mask ( `torch.Tensor`, *optional*):
Cross-attention mask applied to `encoder_hidden_states`. Two formats supported:
* Mask `(batch, sequence_length)` True = keep, False = discard.
* Bias `(batch, 1, sequence_length)` 0 = keep, -10000 = discard.
If `ndim == 2`: will be interpreted as a mask, then converted into a bias consistent with the format
above. This bias will be added to the cross-attention scores.
return_dict (`bool`, *optional*, defaults to `True`):
Whether or not to return a [`~models.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.
"""
# ensure attention_mask is a bias, and give it a singleton query_tokens dimension.
# we may have done this conversion already, e.g. if we came here via UNet2DConditionModel#forward.
# we can tell by counting dims; if ndim == 2: it's a mask rather than a bias.
# expects mask of shape:
# [batch, key_tokens]
# adds singleton query_tokens dimension:
# [batch, 1, key_tokens]
# this helps to broadcast it as a bias over attention scores, which will be in one of the following shapes:
# [batch, heads, query_tokens, key_tokens] (e.g. torch sdp attn)
# [batch * heads, query_tokens, key_tokens] (e.g. xformers or classic attn)
if attention_mask is not None and attention_mask.ndim == 2:
# assume that mask is expressed as:
# (1 = keep, 0 = discard)
# convert mask into a bias that can be added to attention scores:
# (keep = +0, discard = -10000.0)
attention_mask = (1 - attention_mask.to(hidden_states.dtype)) * -10000.0
attention_mask = attention_mask.unsqueeze(1)
# convert encoder_attention_mask to a bias the same way we do for attention_mask
if encoder_attention_mask is not None and encoder_attention_mask.ndim == 2:
encoder_attention_mask = (
1 - encoder_attention_mask.to(hidden_states.dtype)
) * -10000.0
encoder_attention_mask = encoder_attention_mask.unsqueeze(1)
# Retrieve lora scale.
lora_scale = (
cross_attention_kwargs.get("scale", 1.0)
if cross_attention_kwargs is not None
else 1.0
)
# 1. Input
batch, _, height, width = hidden_states.shape
residual = hidden_states
hidden_states = self.norm(hidden_states)
if not self.use_linear_projection:
hidden_states = (
self.proj_in(hidden_states, scale=lora_scale)
if not USE_PEFT_BACKEND
else self.proj_in(hidden_states)
)
inner_dim = hidden_states.shape[1]
hidden_states = hidden_states.permute(0, 2, 3, 1).reshape(
batch, height * width, inner_dim
)
else:
inner_dim = hidden_states.shape[1]
hidden_states = hidden_states.permute(0, 2, 3, 1).reshape(
batch, height * width, inner_dim
)
hidden_states = (
self.proj_in(hidden_states, scale=lora_scale)
if not USE_PEFT_BACKEND
else self.proj_in(hidden_states)
)
# 2. Blocks
if self.caption_projection is not None:
batch_size = hidden_states.shape[0]
encoder_hidden_states = self.caption_projection(encoder_hidden_states)
encoder_hidden_states = encoder_hidden_states.view(
batch_size, -1, hidden_states.shape[-1]
)
ref_feature = hidden_states.reshape(batch, height, width, inner_dim)
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)
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,
attention_mask,
encoder_hidden_states,
encoder_attention_mask,
timestep,
cross_attention_kwargs,
class_labels,
**ckpt_kwargs,
)
else:
hidden_states = block(
hidden_states, # shape [5, 4096, 320]
attention_mask=attention_mask,
encoder_hidden_states=encoder_hidden_states, # shape [1,4,768]
encoder_attention_mask=encoder_attention_mask,
timestep=timestep,
cross_attention_kwargs=cross_attention_kwargs,
class_labels=class_labels,
)
# 3. Output
output = None
if self.is_input_continuous:
if not self.use_linear_projection:
hidden_states = (
hidden_states.reshape(batch, height, width, inner_dim)
.permute(0, 3, 1, 2)
.contiguous()
)
hidden_states = (
self.proj_out(hidden_states, scale=lora_scale)
if not USE_PEFT_BACKEND
else self.proj_out(hidden_states)
)
else:
hidden_states = (
self.proj_out(hidden_states, scale=lora_scale)
if not USE_PEFT_BACKEND
else self.proj_out(hidden_states)
)
hidden_states = (
hidden_states.reshape(batch, height, width, inner_dim)
.permute(0, 3, 1, 2)
.contiguous()
)
output = hidden_states + residual
if not return_dict:
return (output, ref_feature)
return Transformer2DModelOutput(sample=output, ref_feature=ref_feature)