dreamo/transformer.py

# Copyright (c) 2025 Bytedance Ltd. and/or its affiliates
# Copyright 2024 Black Forest Labs and 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, Union

import numpy as np
import torch
from diffusers.models.modeling_outputs import Transformer2DModelOutput
from diffusers.utils import (
    USE_PEFT_BACKEND,
    logging,
    scale_lora_layers,
    unscale_lora_layers,
)

logger = logging.get_logger(__name__)  # pylint: disable=invalid-name


def flux_transformer_forward(
    self,
    hidden_states: torch.Tensor,
    encoder_hidden_states: torch.Tensor = None,
    pooled_projections: torch.Tensor = None,
    timestep: torch.LongTensor = None,
    img_ids: torch.Tensor = None,
    txt_ids: torch.Tensor = None,
    guidance: torch.Tensor = None,
    joint_attention_kwargs: Optional[Dict[str, Any]] = None,
    controlnet_block_samples=None,
    controlnet_single_block_samples=None,
    return_dict: bool = True,
    controlnet_blocks_repeat: bool = False,
    embeddings: torch.Tensor = None,
) -> Union[torch.Tensor, Transformer2DModelOutput]:
    """
    The [`FluxTransformer2DModel`] forward method.

    Args:
        hidden_states (`torch.Tensor` of shape `(batch_size, image_sequence_length, in_channels)`):
            Input `hidden_states`.
        encoder_hidden_states (`torch.Tensor` of shape `(batch_size, text_sequence_length, joint_attention_dim)`):
            Conditional embeddings (embeddings computed from the input conditions such as prompts) to use.
        pooled_projections (`torch.Tensor` of shape `(batch_size, projection_dim)`): Embeddings projected
            from the embeddings of input conditions.
        timestep ( `torch.LongTensor`):
            Used to indicate denoising step.
        block_controlnet_hidden_states: (`list` of `torch.Tensor`):
            A list of tensors that if specified are added to the residuals of transformer blocks.
        joint_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.transformer_2d.Transformer2DModelOutput`] 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.
    """
    if joint_attention_kwargs is not None:
        joint_attention_kwargs = joint_attention_kwargs.copy()
        lora_scale = joint_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)
    else:
        if joint_attention_kwargs is not None and joint_attention_kwargs.get("scale", None) is not None:
            logger.warning(
                "Passing `scale` via `joint_attention_kwargs` when not using the PEFT backend is ineffective."
            )

    hidden_states = self.x_embedder(hidden_states)
    # add task and idx embedding
    if embeddings is not None:
        hidden_states = hidden_states + embeddings

    timestep = timestep.to(hidden_states.dtype) * 1000
    guidance = guidance.to(hidden_states.dtype) * 1000 if guidance is not None else None

    temb = (
        self.time_text_embed(timestep, pooled_projections)
        if guidance is None
        else self.time_text_embed(timestep, guidance, pooled_projections)
    )
    encoder_hidden_states = self.context_embedder(encoder_hidden_states)

    if txt_ids.ndim == 3:
        # logger.warning(
        #     "Passing `txt_ids` 3d torch.Tensor is deprecated."
        #     "Please remove the batch dimension and pass it as a 2d torch Tensor"
        # )
        txt_ids = txt_ids[0]
    if img_ids.ndim == 3:
        # logger.warning(
        #     "Passing `img_ids` 3d torch.Tensor is deprecated."
        #     "Please remove the batch dimension and pass it as a 2d torch Tensor"
        # )
        img_ids = img_ids[0]

    ids = torch.cat((txt_ids, img_ids), dim=0)
    image_rotary_emb = self.pos_embed(ids)

    for index_block, block in enumerate(self.transformer_blocks):
        if torch.is_grad_enabled() and self.gradient_checkpointing:
            encoder_hidden_states, hidden_states = self._gradient_checkpointing_func(
                block,
                hidden_states,
                encoder_hidden_states,
                temb,
                image_rotary_emb,
            )

        else:
            encoder_hidden_states, hidden_states = block(
                hidden_states=hidden_states,
                encoder_hidden_states=encoder_hidden_states,
                temb=temb,
                image_rotary_emb=image_rotary_emb,
                joint_attention_kwargs=joint_attention_kwargs,
            )

        # controlnet residual
        if controlnet_block_samples is not None:
            interval_control = len(self.transformer_blocks) / len(controlnet_block_samples)
            interval_control = int(np.ceil(interval_control))
            # For Xlabs ControlNet.
            if controlnet_blocks_repeat:
                hidden_states = hidden_states + controlnet_block_samples[index_block % len(controlnet_block_samples)]
            else:
                hidden_states = hidden_states + controlnet_block_samples[index_block // interval_control]
    hidden_states = torch.cat([encoder_hidden_states, hidden_states], dim=1)

    for index_block, block in enumerate(self.single_transformer_blocks):
        if torch.is_grad_enabled() and self.gradient_checkpointing:
            hidden_states = self._gradient_checkpointing_func(
                block,
                hidden_states,
                temb,
                image_rotary_emb,
            )

        else:
            hidden_states = block(
                hidden_states=hidden_states,
                temb=temb,
                image_rotary_emb=image_rotary_emb,
                joint_attention_kwargs=joint_attention_kwargs,
            )

        # controlnet residual
        if controlnet_single_block_samples is not None:
            interval_control = len(self.single_transformer_blocks) / len(controlnet_single_block_samples)
            interval_control = int(np.ceil(interval_control))
            hidden_states[:, encoder_hidden_states.shape[1] :, ...] = (
                hidden_states[:, encoder_hidden_states.shape[1] :, ...]
                + controlnet_single_block_samples[index_block // interval_control]
            )

    hidden_states = hidden_states[:, encoder_hidden_states.shape[1] :, ...]

    hidden_states = self.norm_out(hidden_states, temb)
    output = self.proj_out(hidden_states)

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

    if not return_dict:
        return (output,)

    return Transformer2DModelOutput(sample=output)