sd_unet_forward.py

# Copyright (c) 2025 PaddlePaddle Authors. 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

# code is heavily based on https://github.com/tianweiy/DMD2

from dataclasses import dataclass
from typing import Any, Dict, Optional, Tuple, Union

import paddle

from ppdiffusers.utils import (
    USE_PEFT_BACKEND,
    BaseOutput,
    deprecate,
    unscale_lora_layers,
)


@dataclass
class UNet2DConditionOutput(BaseOutput):
    """
    The output of [`UNet2DConditionModel`].

    Args:
        sample (`paddle.Tensor` of shape `(batch_size, num_channels, height, width)`):
            The hidden states output conditioned on `encoder_hidden_states` input. Output of last layer of model.
    """

    sample: paddle.Tensor = None


def classify_forward(
    self,
    sample: paddle.Tensor,
    timestep: Union[paddle.Tensor, float, int],
    encoder_hidden_states: paddle.Tensor,
    class_labels: Optional[paddle.Tensor] = None,
    timestep_cond: Optional[paddle.Tensor] = None,
    attention_mask: Optional[paddle.Tensor] = None,
    cross_attention_kwargs: Optional[Dict[str, Any]] = None,
    added_cond_kwargs: Optional[Dict[str, paddle.Tensor]] = None,
    down_block_additional_residuals: Optional[Tuple[paddle.Tensor]] = None,
    mid_block_additional_residual: Optional[paddle.Tensor] = None,
    down_intrablock_additional_residuals: Optional[Tuple[paddle.Tensor]] = None,
    encoder_attention_mask: Optional[paddle.Tensor] = None,
    return_dict: bool = True,
    classify_mode: bool = False,
):
    r"""
    The [`UNet2DConditionModel`] forward method.

    Args:
        sample (`paddle.FloatTensor`):
            The noisy input tensor with the following shape `(batch, channel, height, width)`.
        timestep (`paddle.FloatTensor` or `float` or `int`): The number of timesteps to denoise an input.
        encoder_hidden_states (`paddle.FloatTensor`):
            The encoder hidden states with shape `(batch, sequence_length, feature_dim)`.
        class_labels (`paddle.Tensor`, *optional*, defaults to `None`):
            Optional class labels for conditioning. Their embeddings will be summed with the timestep embeddings.
        timestep_cond: (`paddle.Tensor`, *optional*, defaults to `None`):
            Conditional embeddings for timestep. If provided, the embeddings will be summed with the samples passed
            through the `self.time_embedding` layer to obtain the timestep embeddings.
        attention_mask (`paddle.Tensor`, *optional*, defaults to `None`):
            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.
        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).
        added_cond_kwargs: (`dict`, *optional*):
            A kwargs dictionary containing additional embeddings that if specified are added to the embeddings that
            are passed along to the UNet blocks.
        down_block_additional_residuals: (`tuple` of `paddle.Tensor`, *optional*):
            A tuple of tensors that if specified are added to the residuals of down unet blocks.
        mid_block_additional_residual: (`paddle.Tensor`, *optional*):
            A tensor that if specified is added to the residual of the middle unet block.
        down_intrablock_additional_residuals (`tuple` of `paddle.Tensor`, *optional*):
            additional residuals to be added within UNet down blocks, for example from T2I-Adapter side model(s)
        encoder_attention_mask (`paddle.Tensor`):
            A cross-attention mask of shape `(batch, sequence_length)` is applied to `encoder_hidden_states`. If
            `True` the mask is kept, otherwise if `False` it is discarded. Mask will be converted into a bias,
            which adds large negative values to the attention scores corresponding to "discard" tokens.
        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.unets.unet_2d_condition.UNet2DConditionOutput`] or `tuple`:
            If `return_dict` is True, an [`~models.unets.unet_2d_condition.UNet2DConditionOutput`] is returned, otherwise
            a `tuple` is returned where the first element is the sample tensor.
    """
    # By default samples have to be AT least a multiple of the overall upsampling factor.
    # The overall upsampling factor is equal to 2 ** (# num of upsampling layers).
    # However, the upsampling interpolation output size can be forced to fit any upsampling size
    # on the fly if necessary.
    default_overall_up_factor = 2**self.num_upsamplers

    # upsample size should be forwarded when sample is not a multiple of `default_overall_up_factor`
    forward_upsample_size = False
    upsample_size = None

    for dim in sample.shape[-2:]:
        if dim % default_overall_up_factor != 0:
            # Forward upsample size to force interpolation output size.
            forward_upsample_size = True
            break

    if attention_mask is not None:
        attention_mask = (1 - attention_mask.to(sample.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:
        encoder_attention_mask = (1 - encoder_attention_mask.to(sample.dtype)) * -10000.0
        encoder_attention_mask = encoder_attention_mask.unsqueeze(1)

    # 0. center input if necessary
    if self.config.center_input_sample:
        sample = 2 * sample - 1.0

    # 1. time
    t_emb = self.get_time_embed(sample=sample, timestep=timestep)
    emb = self.time_embedding(t_emb, timestep_cond)
    aug_emb = None

    class_emb = self.get_class_embed(sample=sample, class_labels=class_labels)
    if class_emb is not None:
        if self.config.class_embeddings_concat:
            emb = paddle.concat([emb, class_emb], axis=-1)
        else:
            emb = emb + class_emb

    aug_emb = self.get_aug_embed(
        emb=emb, encoder_hidden_states=encoder_hidden_states, added_cond_kwargs=added_cond_kwargs
    )
    if self.config.addition_embed_type == "image_hint":
        aug_emb, hint = aug_emb
        sample = paddle.concat([sample, hint], dim=1)

    emb = emb + aug_emb if aug_emb is not None else emb

    if self.time_embed_act is not None:
        emb = self.time_embed_act(emb)

    encoder_hidden_states = self.process_encoder_hidden_states(
        encoder_hidden_states=encoder_hidden_states, added_cond_kwargs=added_cond_kwargs
    )

    # 2. pre-process
    sample = self.conv_in(sample)

    # 2.5 GLIGEN position net
    if cross_attention_kwargs is not None and cross_attention_kwargs.get("gligen", None) is not None:
        cross_attention_kwargs = cross_attention_kwargs.copy()
        gligen_args = cross_attention_kwargs.pop("gligen")
        cross_attention_kwargs["gligen"] = {"objs": self.position_net(**gligen_args)}

    # 3. down
    # we're popping the `scale` instead of getting it because otherwise `scale` will be propagated
    # to the internal blocks and will raise deprecation warnings. this will be confusing for our users.
    if cross_attention_kwargs is not None:
        cross_attention_kwargs = cross_attention_kwargs.copy()
        lora_scale = cross_attention_kwargs.pop("scale", 1.0)
    else:
        lora_scale = 1.0

    # if USE_PEFT_BACKEND:
    #     # weight the lora layers by setting `lora_scale` for each PEFT layer
    #     scale_lora_layers(self, lora_scale)

    is_controlnet = mid_block_additional_residual is not None and down_block_additional_residuals is not None
    # using new arg down_intrablock_additional_residuals for T2I-Adapters, to distinguish from controlnets
    is_adapter = down_intrablock_additional_residuals is not None
    # maintain backward compatibility for legacy usage, where
    #       T2I-Adapter and ControlNet both use down_block_additional_residuals arg
    #       but can only use one or the other
    if not is_adapter and mid_block_additional_residual is None and down_block_additional_residuals is not None:
        deprecate(
            "T2I should not use down_block_additional_residuals",
            "1.3.0",
            "Passing intrablock residual connections with `down_block_additional_residuals` is deprecated \
                    and will be removed in diffusers 1.3.0.  `down_block_additional_residuals` should only be used \
                    for ControlNet. Please make sure use `down_intrablock_additional_residuals` instead. ",
            standard_warn=False,
        )
        down_intrablock_additional_residuals = down_block_additional_residuals
        is_adapter = True

    down_block_res_samples = (sample,)
    for downsample_block in self.down_blocks:
        if hasattr(downsample_block, "has_cross_attention") and downsample_block.has_cross_attention:
            # For t2i-adapter CrossAttnDownBlock2D
            additional_residuals = {}
            if is_adapter and len(down_intrablock_additional_residuals) > 0:
                additional_residuals["additional_residuals"] = down_intrablock_additional_residuals.pop(0)

            sample, res_samples = downsample_block(
                hidden_states=sample,
                temb=emb,
                encoder_hidden_states=encoder_hidden_states,
                attention_mask=attention_mask,
                cross_attention_kwargs=cross_attention_kwargs,
                encoder_attention_mask=encoder_attention_mask,
                **additional_residuals,
            )
        else:
            sample, res_samples = downsample_block(hidden_states=sample, temb=emb)
            if is_adapter and len(down_intrablock_additional_residuals) > 0:
                sample += down_intrablock_additional_residuals.pop(0)

        down_block_res_samples += res_samples

    if is_controlnet:
        new_down_block_res_samples = ()

        for down_block_res_sample, down_block_additional_residual in zip(
            down_block_res_samples, down_block_additional_residuals
        ):
            down_block_res_sample = down_block_res_sample + down_block_additional_residual
            new_down_block_res_samples = new_down_block_res_samples + (down_block_res_sample,)

        down_block_res_samples = new_down_block_res_samples

    # 4. mid
    if self.mid_block is not None:
        if hasattr(self.mid_block, "has_cross_attention") and self.mid_block.has_cross_attention:
            sample = self.mid_block(
                sample,
                emb,
                encoder_hidden_states=encoder_hidden_states,
                attention_mask=attention_mask,
                cross_attention_kwargs=cross_attention_kwargs,
                encoder_attention_mask=encoder_attention_mask,
            )
        else:
            sample = self.mid_block(sample, emb)

        # To support T2I-Adapter-XL
        if (
            is_adapter
            and len(down_intrablock_additional_residuals) > 0
            and sample.shape == down_intrablock_additional_residuals[0].shape
        ):
            sample += down_intrablock_additional_residuals.pop(0)

    if is_controlnet:
        sample = sample + mid_block_additional_residual

    if classify_mode:
        output_list = list(down_block_res_samples) + [sample]
        return output_list

    # 5. up
    for i, upsample_block in enumerate(self.up_blocks):
        is_final_block = i == len(self.up_blocks) - 1

        res_samples = down_block_res_samples[-len(upsample_block.resnets) :]
        down_block_res_samples = down_block_res_samples[: -len(upsample_block.resnets)]

        # if we have not reached the final block and need to forward the
        # upsample size, we do it here
        if not is_final_block and forward_upsample_size:
            upsample_size = down_block_res_samples[-1].shape[2:]

        if hasattr(upsample_block, "has_cross_attention") and upsample_block.has_cross_attention:
            sample = upsample_block(
                hidden_states=sample,
                temb=emb,
                res_hidden_states_tuple=res_samples,
                encoder_hidden_states=encoder_hidden_states,
                cross_attention_kwargs=cross_attention_kwargs,
                upsample_size=upsample_size,
                attention_mask=attention_mask,
                encoder_attention_mask=encoder_attention_mask,
            )
        else:
            sample = upsample_block(
                hidden_states=sample,
                temb=emb,
                res_hidden_states_tuple=res_samples,
                upsample_size=upsample_size,
            )

    # 6. post-process
    if self.conv_norm_out:
        sample = self.conv_norm_out(sample)
        sample = self.conv_act(sample)
    sample = self.conv_out(sample)

    if USE_PEFT_BACKEND:
        # remove `lora_scale` from each PEFT layer
        unscale_lora_layers(self, lora_scale)

    if not return_dict:
        return (sample,)

    return UNet2DConditionOutput(sample=sample)