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# Licensed under the Apache License, Version 2.0 (the "License");
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# http://www.apache.org/licenses/LICENSE-2.0
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from typing import Optional
from torch import nn
from ..modeling_outputs import Transformer2DModelOutput
from .transformer_2d import Transformer2DModel
class DualTransformer2DModel(nn.Module):
"""
Dual transformer wrapper that combines two `Transformer2DModel`s for mixed inference.
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*):
Pass if the input is continuous. The number of channels in the input and output.
num_layers (`int`, *optional*, defaults to 1): The number of layers of Transformer blocks to use.
dropout (`float`, *optional*, defaults to 0.1): The dropout probability to use.
cross_attention_dim (`int`, *optional*): The number of encoder_hidden_states dimensions to use.
sample_size (`int`, *optional*): Pass if the input is discrete. The width of the latent images.
Note that this is fixed at training time as it is used for learning a number of position embeddings. See
`ImagePositionalEmbeddings`.
num_vector_embeds (`int`, *optional*):
Pass if the input is discrete. The number of classes of the vector embeddings of the latent pixels.
Includes the class for the masked latent pixel.
activation_fn (`str`, *optional*, defaults to `"geglu"`): Activation function to be used in feed-forward.
num_embeds_ada_norm ( `int`, *optional*): Pass if at least one of the norm_layers is `AdaLayerNorm`.
The number of diffusion steps used during training. Note that this is fixed at training time as 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 than steps than `num_embeds_ada_norm`.
attention_bias (`bool`, *optional*):
Configure if the TransformerBlocks' attention should contain a bias parameter.
"""
def __init__(
self,
num_attention_heads: int = 16,
attention_head_dim: int = 88,
in_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,
sample_size: Optional[int] = None,
num_vector_embeds: Optional[int] = None,
activation_fn: str = "geglu",
num_embeds_ada_norm: Optional[int] = None,
):
super().__init__()
self.transformers = nn.ModuleList(
[
Transformer2DModel(
num_attention_heads=num_attention_heads,
attention_head_dim=attention_head_dim,
in_channels=in_channels,
num_layers=num_layers,
dropout=dropout,
norm_num_groups=norm_num_groups,
cross_attention_dim=cross_attention_dim,
attention_bias=attention_bias,
sample_size=sample_size,
num_vector_embeds=num_vector_embeds,
activation_fn=activation_fn,
num_embeds_ada_norm=num_embeds_ada_norm,
)
for _ in range(2)
]
)
# Variables that can be set by a pipeline:
# The ratio of transformer1 to transformer2's output states to be combined during inference
self.mix_ratio = 0.5
# The shape of `encoder_hidden_states` is expected to be
# `(batch_size, condition_lengths[0]+condition_lengths[1], num_features)`
self.condition_lengths = [77, 257]
# Which transformer to use to encode which condition.
# E.g. `(1, 0)` means that we'll use `transformers[1](conditions[0])` and `transformers[0](conditions[1])`
self.transformer_index_for_condition = [1, 0]
def forward(
self,
hidden_states,
encoder_hidden_states,
timestep=None,
attention_mask=None,
cross_attention_kwargs=None,
return_dict: bool = True,
):
"""
Args:
hidden_states ( When discrete, `torch.LongTensor` of shape `(batch size, num latent pixels)`.
When continuous, `torch.Tensor` of shape `(batch size, channel, height, width)`): Input hidden_states.
encoder_hidden_states ( `torch.LongTensor` of shape `(batch size, encoder_hidden_states dim)`, *optional*):
Conditional embeddings for cross attention layer. If not given, cross-attention defaults to
self-attention.
timestep ( `torch.long`, *optional*):
Optional timestep to be applied as an embedding in AdaLayerNorm's. Used to indicate denoising step.
attention_mask (`torch.Tensor`, *optional*):
Optional attention mask to be applied in Attention.
cross_attention_kwargs (`dict`, *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:
[`~models.transformers.transformer_2d.Transformer2DModelOutput`] or `tuple`:
[`~models.transformers.transformer_2d.Transformer2DModelOutput`] if `return_dict` is True, otherwise a
`tuple`. When returning a tuple, the first element is the sample tensor.
"""
input_states = hidden_states
encoded_states = []
tokens_start = 0
# attention_mask is not used yet
for i in range(2):
# for each of the two transformers, pass the corresponding condition tokens
condition_state = encoder_hidden_states[:, tokens_start : tokens_start + self.condition_lengths[i]]
transformer_index = self.transformer_index_for_condition[i]
encoded_state = self.transformers[transformer_index](
input_states,
encoder_hidden_states=condition_state,
timestep=timestep,
cross_attention_kwargs=cross_attention_kwargs,
return_dict=False,
)[0]
encoded_states.append(encoded_state - input_states)
tokens_start += self.condition_lengths[i]
output_states = encoded_states[0] * self.mix_ratio + encoded_states[1] * (1 - self.mix_ratio)
output_states = output_states + input_states
if not return_dict:
return (output_states,)
return Transformer2DModelOutput(sample=output_states)