""" 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)