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[Feat] PixArt-Alpha (#5642)
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* init pixart alpha pipeline

* fix: import

* script

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* add: vae to the pipeline

* add: vae_scale_factor

* add: checkpoint_path

* clean conversion script a bit.

* size embeddings.

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* support for conditioning.

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* DPMSolverMultistepScheduler

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* remove print

* remove support for negative prompt embeds.

* typo.

* remove extra kwargs

* bring conversion script to where it was

* fix

* trying mu luck

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* update example

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* Apply suggestions from code review

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* add a note about size brackets.

* fix

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* fix optional test

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* debug

---------

Co-authored-by: Patrick von Platen <patrick.v.platen@gmail.com>
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sayakpaul and patrickvonplaten authored Nov 6, 2023
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2 changes: 2 additions & 0 deletions docs/source/en/_toctree.yml
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title: Parallel Sampling of Diffusion Models
- local: api/pipelines/pix2pix_zero
title: Pix2Pix Zero
- local: api/pipelines/pixart
title: PixArt
- local: api/pipelines/pndm
title: PNDM
- local: api/pipelines/repaint
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36 changes: 36 additions & 0 deletions docs/source/en/api/pipelines/pixart.md
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<!--Copyright 2023 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.
-->

# PixArt

![](https://huggingface.co/datasets/huggingface/documentation-images/resolve/main/diffusers/pixart/header_collage.png)

[PixArt-α: Fast Training of Diffusion Transformer for Photorealistic Text-to-Image Synthesis](https://huggingface.co/papers/2310.00426) is Junsong Chen, Jincheng Yu, Chongjian Ge, Lewei Yao, Enze Xie, Yue Wu, Zhongdao Wang, James Kwok, Ping Luo, Huchuan Lu, and Zhenguo Li.

The abstract from the paper is:

*The most advanced text-to-image (T2I) models require significant training costs (e.g., millions of GPU hours), seriously hindering the fundamental innovation for the AIGC community while increasing CO2 emissions. This paper introduces PIXART-α, a Transformer-based T2I diffusion model whose image generation quality is competitive with state-of-the-art image generators (e.g., Imagen, SDXL, and even Midjourney), reaching near-commercial application standards. Additionally, it supports high-resolution image synthesis up to 1024px resolution with low training cost, as shown in Figure 1 and 2. To achieve this goal, three core designs are proposed: (1) Training strategy decomposition: We devise three distinct training steps that separately optimize pixel dependency, text-image alignment, and image aesthetic quality; (2) Efficient T2I Transformer: We incorporate cross-attention modules into Diffusion Transformer (DiT) to inject text conditions and streamline the computation-intensive class-condition branch; (3) High-informative data: We emphasize the significance of concept density in text-image pairs and leverage a large Vision-Language model to auto-label dense pseudo-captions to assist text-image alignment learning. As a result, PIXART-α's training speed markedly surpasses existing large-scale T2I models, e.g., PIXART-α only takes 10.8% of Stable Diffusion v1.5's training time (675 vs. 6,250 A100 GPU days), saving nearly $300,000 ($26,000 vs. $320,000) and reducing 90% CO2 emissions. Moreover, compared with a larger SOTA model, RAPHAEL, our training cost is merely 1%. Extensive experiments demonstrate that PIXART-α excels in image quality, artistry, and semantic control. We hope PIXART-α will provide new insights to the AIGC community and startups to accelerate building their own high-quality yet low-cost generative models from scratch.*

You can find the original codebase at [PixArt-alpha/PixArt-alpha](https://github.com/PixArt-alpha/PixArt-alpha) and all the available checkpoints at [PixArt-alpha](https://huggingface.co/PixArt-alpha).

Some notes about this pipeline:

* It uses a Transformer backbone (instead of a UNet) for denoising. As such it has a similar architecture as [DiT](./dit.md).
* It was trained using text conditions computed from T5. This aspect makes the pipeline better at following complex text prompts with intricate details.
* It is good at producing high-resolution images at different aspect ratios. To get the best results, the authors recommend some size brackets which can be found [here](https://github.com/PixArt-alpha/PixArt-alpha/blob/08fbbd281ec96866109bdd2cdb75f2f58fb17610/diffusion/data/datasets/utils.py).
* It rivals the quality of state-of-the-art text-to-image generation systems (as of this writing) such as Stable Diffusion XL, Imagen, and DALL-E 2, while being more efficient than them.

## PixArtAlphaPipeline

[[autodoc]] PixArtAlphaPipeline
- all
- __call__
198 changes: 198 additions & 0 deletions scripts/convert_pixart_alpha_to_diffusers.py
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import argparse
import os

import torch
from transformers import T5EncoderModel, T5Tokenizer

from diffusers import AutoencoderKL, DPMSolverMultistepScheduler, PixArtAlphaPipeline, Transformer2DModel


ckpt_id = "PixArt-alpha/PixArt-alpha"
# https://github.com/PixArt-alpha/PixArt-alpha/blob/0f55e922376d8b797edd44d25d0e7464b260dcab/scripts/inference.py#L125
interpolation_scale = {512: 1, 1024: 2}


def main(args):
all_state_dict = torch.load(args.orig_ckpt_path)
state_dict = all_state_dict.pop("state_dict")
converted_state_dict = {}

# Patch embeddings.
converted_state_dict["pos_embed.proj.weight"] = state_dict.pop("x_embedder.proj.weight")
converted_state_dict["pos_embed.proj.bias"] = state_dict.pop("x_embedder.proj.bias")

# Caption projection.
converted_state_dict["caption_projection.y_embedding"] = state_dict.pop("y_embedder.y_embedding")
converted_state_dict["caption_projection.linear_1.weight"] = state_dict.pop("y_embedder.y_proj.fc1.weight")
converted_state_dict["caption_projection.linear_1.bias"] = state_dict.pop("y_embedder.y_proj.fc1.bias")
converted_state_dict["caption_projection.linear_2.weight"] = state_dict.pop("y_embedder.y_proj.fc2.weight")
converted_state_dict["caption_projection.linear_2.bias"] = state_dict.pop("y_embedder.y_proj.fc2.bias")

# AdaLN-single LN
converted_state_dict["adaln_single.emb.timestep_embedder.linear_1.weight"] = state_dict.pop(
"t_embedder.mlp.0.weight"
)
converted_state_dict["adaln_single.emb.timestep_embedder.linear_1.bias"] = state_dict.pop("t_embedder.mlp.0.bias")
converted_state_dict["adaln_single.emb.timestep_embedder.linear_2.weight"] = state_dict.pop(
"t_embedder.mlp.2.weight"
)
converted_state_dict["adaln_single.emb.timestep_embedder.linear_2.bias"] = state_dict.pop("t_embedder.mlp.2.bias")

if args.image_size == 1024:
# Resolution.
converted_state_dict["adaln_single.emb.resolution_embedder.linear_1.weight"] = state_dict.pop(
"csize_embedder.mlp.0.weight"
)
converted_state_dict["adaln_single.emb.resolution_embedder.linear_1.bias"] = state_dict.pop(
"csize_embedder.mlp.0.bias"
)
converted_state_dict["adaln_single.emb.resolution_embedder.linear_2.weight"] = state_dict.pop(
"csize_embedder.mlp.2.weight"
)
converted_state_dict["adaln_single.emb.resolution_embedder.linear_2.bias"] = state_dict.pop(
"csize_embedder.mlp.2.bias"
)
# Aspect ratio.
converted_state_dict["adaln_single.emb.aspect_ratio_embedder.linear_1.weight"] = state_dict.pop(
"ar_embedder.mlp.0.weight"
)
converted_state_dict["adaln_single.emb.aspect_ratio_embedder.linear_1.bias"] = state_dict.pop(
"ar_embedder.mlp.0.bias"
)
converted_state_dict["adaln_single.emb.aspect_ratio_embedder.linear_2.weight"] = state_dict.pop(
"ar_embedder.mlp.2.weight"
)
converted_state_dict["adaln_single.emb.aspect_ratio_embedder.linear_2.bias"] = state_dict.pop(
"ar_embedder.mlp.2.bias"
)
# Shared norm.
converted_state_dict["adaln_single.linear.weight"] = state_dict.pop("t_block.1.weight")
converted_state_dict["adaln_single.linear.bias"] = state_dict.pop("t_block.1.bias")

for depth in range(28):
# Transformer blocks.
converted_state_dict[f"transformer_blocks.{depth}.scale_shift_table"] = state_dict.pop(
f"blocks.{depth}.scale_shift_table"
)

# Attention is all you need 🤘

# Self attention.
q, k, v = torch.chunk(state_dict.pop(f"blocks.{depth}.attn.qkv.weight"), 3, dim=0)
q_bias, k_bias, v_bias = torch.chunk(state_dict.pop(f"blocks.{depth}.attn.qkv.bias"), 3, dim=0)
converted_state_dict[f"transformer_blocks.{depth}.attn1.to_q.weight"] = q
converted_state_dict[f"transformer_blocks.{depth}.attn1.to_q.bias"] = q_bias
converted_state_dict[f"transformer_blocks.{depth}.attn1.to_k.weight"] = k
converted_state_dict[f"transformer_blocks.{depth}.attn1.to_k.bias"] = k_bias
converted_state_dict[f"transformer_blocks.{depth}.attn1.to_v.weight"] = v
converted_state_dict[f"transformer_blocks.{depth}.attn1.to_v.bias"] = v_bias
# Projection.
converted_state_dict[f"transformer_blocks.{depth}.attn1.to_out.0.weight"] = state_dict.pop(
f"blocks.{depth}.attn.proj.weight"
)
converted_state_dict[f"transformer_blocks.{depth}.attn1.to_out.0.bias"] = state_dict.pop(
f"blocks.{depth}.attn.proj.bias"
)

# Feed-forward.
converted_state_dict[f"transformer_blocks.{depth}.ff.net.0.proj.weight"] = state_dict.pop(
f"blocks.{depth}.mlp.fc1.weight"
)
converted_state_dict[f"transformer_blocks.{depth}.ff.net.0.proj.bias"] = state_dict.pop(
f"blocks.{depth}.mlp.fc1.bias"
)
converted_state_dict[f"transformer_blocks.{depth}.ff.net.2.weight"] = state_dict.pop(
f"blocks.{depth}.mlp.fc2.weight"
)
converted_state_dict[f"transformer_blocks.{depth}.ff.net.2.bias"] = state_dict.pop(
f"blocks.{depth}.mlp.fc2.bias"
)

# Cross-attention.
q = state_dict.pop(f"blocks.{depth}.cross_attn.q_linear.weight")
q_bias = state_dict.pop(f"blocks.{depth}.cross_attn.q_linear.bias")
k, v = torch.chunk(state_dict.pop(f"blocks.{depth}.cross_attn.kv_linear.weight"), 2, dim=0)
k_bias, v_bias = torch.chunk(state_dict.pop(f"blocks.{depth}.cross_attn.kv_linear.bias"), 2, dim=0)

converted_state_dict[f"transformer_blocks.{depth}.attn2.to_q.weight"] = q
converted_state_dict[f"transformer_blocks.{depth}.attn2.to_q.bias"] = q_bias
converted_state_dict[f"transformer_blocks.{depth}.attn2.to_k.weight"] = k
converted_state_dict[f"transformer_blocks.{depth}.attn2.to_k.bias"] = k_bias
converted_state_dict[f"transformer_blocks.{depth}.attn2.to_v.weight"] = v
converted_state_dict[f"transformer_blocks.{depth}.attn2.to_v.bias"] = v_bias

converted_state_dict[f"transformer_blocks.{depth}.attn2.to_out.0.weight"] = state_dict.pop(
f"blocks.{depth}.cross_attn.proj.weight"
)
converted_state_dict[f"transformer_blocks.{depth}.attn2.to_out.0.bias"] = state_dict.pop(
f"blocks.{depth}.cross_attn.proj.bias"
)

# Final block.
converted_state_dict["proj_out.weight"] = state_dict.pop("final_layer.linear.weight")
converted_state_dict["proj_out.bias"] = state_dict.pop("final_layer.linear.bias")
converted_state_dict["scale_shift_table"] = state_dict.pop("final_layer.scale_shift_table")

# DiT XL/2
transformer = Transformer2DModel(
sample_size=args.image_size // 8,
num_layers=28,
attention_head_dim=72,
in_channels=4,
out_channels=8,
patch_size=2,
attention_bias=True,
num_attention_heads=16,
cross_attention_dim=1152,
activation_fn="gelu-approximate",
num_embeds_ada_norm=1000,
norm_type="ada_norm_single",
norm_elementwise_affine=False,
norm_eps=1e-6,
caption_channels=4096,
)
transformer.load_state_dict(converted_state_dict, strict=True)

assert transformer.pos_embed.pos_embed is not None
state_dict.pop("pos_embed")
assert len(state_dict) == 0, f"State dict is not empty, {state_dict.keys()}"

num_model_params = sum(p.numel() for p in transformer.parameters())
print(f"Total number of transformer parameters: {num_model_params}")

if args.only_transformer:
transformer.save_pretrained(os.path.join(args.dump_path, "transformer"))
else:
scheduler = DPMSolverMultistepScheduler()

vae = AutoencoderKL.from_pretrained(ckpt_id, subfolder="sd-vae-ft-ema")

tokenizer = T5Tokenizer.from_pretrained(ckpt_id, subfolder="t5-v1_1-xxl")
text_encoder = T5EncoderModel.from_pretrained(ckpt_id, subfolder="t5-v1_1-xxl")

pipeline = PixArtAlphaPipeline(
tokenizer=tokenizer, text_encoder=text_encoder, transformer=transformer, vae=vae, scheduler=scheduler
)

pipeline.save_pretrained(args.dump_path)


if __name__ == "__main__":
parser = argparse.ArgumentParser()

parser.add_argument(
"--orig_ckpt_path", default=None, type=str, required=False, help="Path to the checkpoint to convert."
)
parser.add_argument(
"--image_size",
default=1024,
type=int,
choices=[512, 1024],
required=False,
help="Image size of pretrained model, either 512 or 1024.",
)
parser.add_argument("--dump_path", default=None, type=str, required=True, help="Path to the output pipeline.")
parser.add_argument("--only_transformer", default=True, type=bool, required=True)

args = parser.parse_args()
main(args)
2 changes: 2 additions & 0 deletions src/diffusers/__init__.py
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"LDMTextToImagePipeline",
"MusicLDMPipeline",
"PaintByExamplePipeline",
"PixArtAlphaPipeline",
"SemanticStableDiffusionPipeline",
"ShapEImg2ImgPipeline",
"ShapEPipeline",
Expand Down Expand Up @@ -579,6 +580,7 @@
LDMTextToImagePipeline,
MusicLDMPipeline,
PaintByExamplePipeline,
PixArtAlphaPipeline,
SemanticStableDiffusionPipeline,
ShapEImg2ImgPipeline,
ShapEPipeline,
Expand Down
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