How to contribute a community pipeline

Community pipelines allow you to add any additional features you’d like on top of the DiffusionPipeline. The main benefit of building on top of the DiffusionPipeline is anyone can load and use your pipeline by only adding one more argument, making it super easy for the community to access.

This guide will show you how to create a community pipeline and explain how they work. To keep things simple, you’ll create a “one-step” pipeline where the UNet does a single forward pass and calls the scheduler once.

Initialize the pipeline

You should start by creating a one_step_unet.py file for your community pipeline. In this file, create a pipeline class that inherits from the DiffusionPipeline to be able to load model weights and the scheduler configuration from the Hub. The one-step pipeline needs a UNet and a scheduler, so you’ll need to add these as arguments to the __init__ function:

from diffusers import DiffusionPipeline
import torch


class UnetSchedulerOneForwardPipeline(DiffusionPipeline):
    def __init__(self, unet, scheduler):
        super().__init__()

To ensure your pipeline and its components (unet and scheduler) can be saved with save_pretrained(), add them to the register_modules function:

  from diffusers import DiffusionPipeline
  import torch

  class UnetSchedulerOneForwardPipeline(DiffusionPipeline):
      def __init__(self, unet, scheduler):
          super().__init__()

+         self.register_modules(unet=unet, scheduler=scheduler)

Cool, the __init__ step is done and you can move to the forward pass now! 🔥

Define the forward pass

In the forward pass, which we recommend defining as __call__, you have complete creative freedom to add whatever feature you’d like. For our amazing one-step pipeline, create a random image and only call the unet and scheduler once by setting timestep=1:

  from diffusers import DiffusionPipeline
  import torch


  class UnetSchedulerOneForwardPipeline(DiffusionPipeline):
      def __init__(self, unet, scheduler):
          super().__init__()

          self.register_modules(unet=unet, scheduler=scheduler)

+     def __call__(self):
+         image = torch.randn(
+             (1, self.unet.config.in_channels, self.unet.config.sample_size, self.unet.config.sample_size),
+         )
+         timestep = 1

+         model_output = self.unet(image, timestep).sample
+         scheduler_output = self.scheduler.step(model_output, timestep, image).prev_sample

+         return scheduler_output

That’s it! 🚀 You can now run this pipeline by passing a unet and scheduler to it:

from diffusers import DDPMScheduler, UNet2DModel

scheduler = DDPMScheduler()
unet = UNet2DModel()

pipeline = UnetSchedulerOneForwardPipeline(unet=unet, scheduler=scheduler)

output = pipeline()

But what’s even better is you can load pre-existing weights into the pipeline if the pipeline structure is identical. For example, you can load the google/ddpm-cifar10-32 weights into the one-step pipeline:

pipeline = UnetSchedulerOneForwardPipeline.from_pretrained("google/ddpm-cifar10-32")

output = pipeline()

Share your pipeline

Open a Pull Request on the 🧨 Diffusers repository to add your awesome pipeline in one_step_unet.py to the examples/community subfolder.

Once it is merged, anyone with diffusers >= 0.4.0 installed can use this pipeline magically 🪄 by specifying it in the custom_pipeline argument:

from diffusers import DiffusionPipeline

pipe = DiffusionPipeline.from_pretrained("google/ddpm-cifar10-32", custom_pipeline="one_step_unet")
pipe()

Another way to share your community pipeline is to upload the one_step_unet.py file directly to your preferred model repository on the Hub. Instead of specifying the one_step_unet.py file, pass the model repository id to the custom_pipeline argument:

from diffusers import DiffusionPipeline

pipeline = DiffusionPipeline.from_pretrained("google/ddpm-cifar10-32", custom_pipeline="stevhliu/one_step_unet")

Take a look at the following table to compare the two sharing workflows to help you decide the best option for you:

How do community pipelines work?

A community pipeline is a class that inherits from DiffusionPipeline which means:

• It can be loaded with the custom_pipeline argument.
• The model weights and scheduler configuration are loaded from pretrained_model_name_or_path.
• The code that implements a feature in the community pipeline is defined in a pipeline.py file.

Sometimes you can’t load all the pipeline components weights from an official repository. In this case, the other components should be passed directly to the pipeline:

from diffusers import DiffusionPipeline
from transformers import CLIPFeatureExtractor, CLIPModel

model_id = "CompVis/stable-diffusion-v1-4"
clip_model_id = "laion/CLIP-ViT-B-32-laion2B-s34B-b79K"

feature_extractor = CLIPFeatureExtractor.from_pretrained(clip_model_id)
clip_model = CLIPModel.from_pretrained(clip_model_id, torch_dtype=torch.float16)

pipeline = DiffusionPipeline.from_pretrained(
    model_id,
    custom_pipeline="clip_guided_stable_diffusion",
    clip_model=clip_model,
    feature_extractor=feature_extractor,
    scheduler=scheduler,
    torch_dtype=torch.float16,
)

The magic behind community pipelines is contained in the following code. It allows the community pipeline to be loaded from GitHub or the Hub, and it’ll be available to all 🧨 Diffusers packages.

# 2. Load the pipeline class, if using custom module then load it from the hub
# if we load from explicit class, let's use it
if custom_pipeline is not None:
    pipeline_class = get_class_from_dynamic_module(
        custom_pipeline, module_file=CUSTOM_PIPELINE_FILE_NAME, cache_dir=custom_pipeline
    )
elif cls != DiffusionPipeline:
    pipeline_class = cls
else:
    diffusers_module = importlib.import_module(cls.__module__.split(".")[0])
    pipeline_class = getattr(diffusers_module, config_dict["_class_name"])