#
Accelerated PyTorch 2.0 support in Diffusers

Starting from version `0.13.0`, Diffusers supports the latest optimization from PyTorch 2.0. These include:

1. Support for accelerated transformers implementation with memory-efficient attention – no extra dependencies (such as `xformers`) required.
2. torch.compile support for extra performance boost when individual models are compiled.

##
Installation

To benefit from the accelerated attention implementation and `torch.compile()`, you just need to install the latest versions of PyTorch 2.0 from pip, and make sure you are on diffusers 0.13.0 or later. As explained below, diffusers automatically uses the optimized attention processor (`AttnProcessor2_0`) (but not `torch.compile()`) when PyTorch 2.0 is available.

    pip install --upgrade torch diffusers

##
Using accelerated transformers and `torch.compile`.

1. Accelerated Transformers implementation

   PyTorch 2.0 includes an optimized and memory-efficient attention implementation through the `torch.nn.functional.scaled_dot_product_attention` function, which automatically enables several optimizations depending on the inputs and the GPU type. This is similar to the `memory_efficient_attention` from xFormers, but built natively into PyTorch.

   These optimizations will be enabled by default in Diffusers if PyTorch 2.0 is installed and if `torch.nn.functional.scaled_dot_product_attention` is available. To use it, just install `torch 2.0` as suggested above and simply use the pipeline. For example:

       import torch
       from diffusers import DiffusionPipeline

       pipe = DiffusionPipeline.from_pretrained("runwayml/stable-diffusion-v1-5", torch_dtype=torch.float16)
       pipe = pipe.to("cuda")

       prompt = "a photo of an astronaut riding a horse on mars"
       image = pipe(prompt).images[0]

   If you want to enable it explicitly (which is not required), you can do so as shown below.

       import torch
       from diffusers import DiffusionPipeline
       + from diffusers.models.attention_processor import AttnProcessor2_0

       pipe = DiffusionPipeline.from_pretrained("runwayml/stable-diffusion-v1-5", torch_dtype=torch.float16).to("cuda")
       + pipe.unet.set_attn_processor(AttnProcessor2_0())

       prompt = "a photo of an astronaut riding a horse on mars"
       image = pipe(prompt).images[0]

   This should be as fast and memory efficient as `xFormers`. More details in our benchmark.

   It is possible to revert to the vanilla attention processor (`AttnProcessor`), which can be helpful to make the pipeline more deterministic, or if you need to convert a fine-tuned model to other formats such as Core ML. To use the normal attention processor you can use the set_default_attn_processor() function:

       import torch
       from diffusers import DiffusionPipeline
       from diffusers.models.attention_processor import AttnProcessor

       pipe = DiffusionPipeline.from_pretrained("runwayml/stable-diffusion-v1-5", torch_dtype=torch.float16).to("cuda")
       pipe.unet.set_default_attn_processor()

       prompt = "a photo of an astronaut riding a horse on mars"
       image = pipe(prompt).images[0]

2. torch.compile

   To get an additional speedup, we can use the new `torch.compile` feature. Since the UNet of the pipeline is usually the most computationally expensive, we wrap the `unet` with `torch.compile` leaving rest of the sub-models (text encoder and VAE) as is. For more information and different options, refer to the torch compile docs.

       pipe.unet = torch.compile(pipe.unet, mode="reduce-overhead", fullgraph=True)
       images = pipe(prompt, num_inference_steps=steps, num_images_per_prompt=batch_size).images

   Depending on the type of GPU, `compile()` can yield between 5% - 300% of additional speed-up over the accelerated transformer optimizations. Note, however, that compilation is able to squeeze more performance improvements in more recent GPU architectures such as Ampere (A100, 3090), Ada (4090) and Hopper (H100).

   Compilation takes some time to complete, so it is best suited for situations where you need to prepare your pipeline once and then perform the same type of inference operations multiple times. Calling the compiled pipeline on a different image size will re-trigger compilation which can be expensive.

##
Benchmark

We conducted a comprehensive benchmark with PyTorch 2.0’s efficient attention implementation and `torch.compile` across different GPUs and batch sizes for five of our most used pipelines. We used `diffusers 0.17.0.dev0`, which makes sure `torch.compile()` is leveraged optimally.

###
Benchmarking code

####
Stable Diffusion text-to-image

    from diffusers import DiffusionPipeline
    import torch

    path = "runwayml/stable-diffusion-v1-5"

    run_compile = True  # Set True / False

    pipe = DiffusionPipeline.from_pretrained(path, torch_dtype=torch.float16)
    pipe = pipe.to("cuda")
    pipe.unet.to(memory_format=torch.channels_last)

    if run_compile:
        print("Run torch compile")
        pipe.unet = torch.compile(pipe.unet, mode="reduce-overhead", fullgraph=True)

    prompt = "ghibli style, a fantasy landscape with castles"

    for _ in range(3):
        images = pipe(prompt=prompt).images

####
Stable Diffusion image-to-image

    from diffusers import StableDiffusionImg2ImgPipeline
    import requests
    import torch
    from PIL import Image
    from io import BytesIO

    url = "https://raw.githubusercontent.com/CompVis/stable-diffusion/main/assets/stable-samples/img2img/sketch-mountains-input.jpg"

    response = requests.get(url)
    init_image = Image.open(BytesIO(response.content)).convert("RGB")
    init_image = init_image.resize((512, 512))

    path = "runwayml/stable-diffusion-v1-5"

    run_compile = True  # Set True / False

    pipe = StableDiffusionImg2ImgPipeline.from_pretrained(path, torch_dtype=torch.float16)
    pipe = pipe.to("cuda")
    pipe.unet.to(memory_format=torch.channels_last)

    if run_compile:
        print("Run torch compile")
        pipe.unet = torch.compile(pipe.unet, mode="reduce-overhead", fullgraph=True)

    prompt = "ghibli style, a fantasy landscape with castles"

    for _ in range(3):
        image = pipe(prompt=prompt, image=init_image).images[0]

####
Stable Diffusion - inpainting

    from diffusers import StableDiffusionInpaintPipeline
    import requests
    import torch
    from PIL import Image
    from io import BytesIO

    url = "https://raw.githubusercontent.com/CompVis/stable-diffusion/main/assets/stable-samples/img2img/sketch-mountains-input.jpg"

    def download_image(url):
        response = requests.get(url)
        return Image.open(BytesIO(response.content)).convert("RGB")

    img_url = "https://raw.githubusercontent.com/CompVis/latent-diffusion/main/data/inpainting_examples/overture-creations-5sI6fQgYIuo.png"
    mask_url = "https://raw.githubusercontent.com/CompVis/latent-diffusion/main/data/inpainting_examples/overture-creations-5sI6fQgYIuo_mask.png"

    init_image = download_image(img_url).resize((512, 512))
    mask_image = download_image(mask_url).resize((512, 512))

    path = "runwayml/stable-diffusion-inpainting"

    run_compile = True  # Set True / False

    pipe = StableDiffusionInpaintPipeline.from_pretrained(path, torch_dtype=torch.float16)
    pipe = pipe.to("cuda")
    pipe.unet.to(memory_format=torch.channels_last)

    if run_compile:
        print("Run torch compile")
        pipe.unet = torch.compile(pipe.unet, mode="reduce-overhead", fullgraph=True)

    prompt = "ghibli style, a fantasy landscape with castles"

    for _ in range(3):
        image = pipe(prompt=prompt, image=init_image, mask_image=mask_image).images[0]

####
ControlNet

    from diffusers import StableDiffusionControlNetPipeline, ControlNetModel
    import requests
    import torch
    from PIL import Image
    from io import BytesIO

    url = "https://raw.githubusercontent.com/CompVis/stable-diffusion/main/assets/stable-samples/img2img/sketch-mountains-input.jpg"

    response = requests.get(url)
    init_image = Image.open(BytesIO(response.content)).convert("RGB")
    init_image = init_image.resize((512, 512))

    path = "runwayml/stable-diffusion-v1-5"

    run_compile = True  # Set True / False
    controlnet = ControlNetModel.from_pretrained("lllyasviel/sd-controlnet-canny", torch_dtype=torch.float16)
    pipe = StableDiffusionControlNetPipeline.from_pretrained(
        path, controlnet=controlnet, torch_dtype=torch.float16
    )

    pipe = pipe.to("cuda")
    pipe.unet.to(memory_format=torch.channels_last)
    pipe.controlnet.to(memory_format=torch.channels_last)

    if run_compile:
        print("Run torch compile")
        pipe.unet = torch.compile(pipe.unet, mode="reduce-overhead", fullgraph=True)
        pipe.controlnet = torch.compile(pipe.controlnet, mode="reduce-overhead", fullgraph=True)

    prompt = "ghibli style, a fantasy landscape with castles"

    for _ in range(3):
        image = pipe(prompt=prompt, image=init_image).images[0]

####
IF text-to-image + upscaling

    from diffusers import DiffusionPipeline
    import torch

    run_compile = True  # Set True / False

    pipe = DiffusionPipeline.from_pretrained("DeepFloyd/IF-I-M-v1.0", variant="fp16", text_encoder=None, torch_dtype=torch.float16)
    pipe.to("cuda")
    pipe_2 = DiffusionPipeline.from_pretrained("DeepFloyd/IF-II-M-v1.0", variant="fp16", text_encoder=None, torch_dtype=torch.float16)
    pipe_2.to("cuda")
    pipe_3 = DiffusionPipeline.from_pretrained("stabilityai/stable-diffusion-x4-upscaler", torch_dtype=torch.float16)
    pipe_3.to("cuda")

    pipe.unet.to(memory_format=torch.channels_last)
    pipe_2.unet.to(memory_format=torch.channels_last)
    pipe_3.unet.to(memory_format=torch.channels_last)

    if run_compile:
        pipe.unet = torch.compile(pipe.unet, mode="reduce-overhead", fullgraph=True)
        pipe_2.unet = torch.compile(pipe_2.unet, mode="reduce-overhead", fullgraph=True)
        pipe_3.unet = torch.compile(pipe_3.unet, mode="reduce-overhead", fullgraph=True)

    prompt = "the blue hulk"

    prompt_embeds = torch.randn((1, 2, 4096), dtype=torch.float16)
    neg_prompt_embeds = torch.randn((1, 2, 4096), dtype=torch.float16)

    for _ in range(3):
        image = pipe(prompt_embeds=prompt_embeds, negative_prompt_embeds=neg_prompt_embeds, output_type="pt").images
        image_2 = pipe_2(image=image, prompt_embeds=prompt_embeds, negative_prompt_embeds=neg_prompt_embeds, output_type="pt").images
        image_3 = pipe_3(prompt=prompt, image=image, noise_level=100).images

To give you a pictorial overview of the possible speed-ups that can be obtained with PyTorch 2.0 and `torch.compile()`, here is a plot that shows relative speed-ups for the Stable Diffusion text-to-image pipeline across five different GPU families (with a batch size of 4):

To give you an even better idea of how this speed-up holds for the other pipelines presented above, consider the following plot that shows the benchmarking numbers from an A100 across three different batch sizes (with PyTorch 2.0 nightly and `torch.compile()`):

(Our benchmarking metric for the plots above is number of iterations/second)

But we reveal all the benchmarking numbers in the interest of transparency!

In the following tables, we report our findings in terms of the number of iterations processed per second.

###
A100 (batch size: 1)

Pipeline | torch 2.0 - no compile | torch nightly - no compile | torch 2.0 - compile | torch nightly - compile
--- | --- | --- | --- | ---
SD - txt2img | 21.66 | 23.13 | 44.03 | 49.74
SD - img2img | 21.81 | 22.40 | 43.92 | 46.32
SD - inpaint | 22.24 | 23.23 | 43.76 | 49.25
SD - controlnet | 15.02 | 15.82 | 32.13 | 36.08
IF | 20.21 / 13.84 / 24.00 | 20.12 / 13.70 / 24.03 | ❌ | 97.34 / 27.23 / 111.66

###
A100 (batch size: 4)

Pipeline | torch 2.0 - no compile | torch nightly - no compile | torch 2.0 - compile | torch nightly - compile
--- | --- | --- | --- | ---
SD - txt2img | 11.6 | 13.12 | 14.62 | 17.27
SD - img2img | 11.47 | 13.06 | 14.66 | 17.25
SD - inpaint | 11.67 | 13.31 | 14.88 | 17.48
SD - controlnet | 8.28 | 9.38 | 10.51 | 12.41
IF | 25.02 | 18.04 | ❌ | 48.47

###
A100 (batch size: 16)

Pipeline | torch 2.0 - no compile | torch nightly - no compile | torch 2.0 - compile | torch nightly - compile
--- | --- | --- | --- | ---
SD - txt2img | 3.04 | 3.6 | 3.83 | 4.68
SD - img2img | 2.98 | 3.58 | 3.83 | 4.67
SD - inpaint | 3.04 | 3.66 | 3.9 | 4.76
SD - controlnet | 2.15 | 2.58 | 2.74 | 3.35
IF | 8.78 | 9.82 | ❌ | 16.77

###
V100 (batch size: 1)

Pipeline | torch 2.0 - no compile | torch nightly - no compile | torch 2.0 - compile | torch nightly - compile
--- | --- | --- | --- | ---
SD - txt2img | 18.99 | 19.14 | 20.95 | 22.17
SD - img2img | 18.56 | 19.18 | 20.95 | 22.11
SD - inpaint | 19.14 | 19.06 | 21.08 | 22.20
SD - controlnet | 13.48 | 13.93 | 15.18 | 15.88
IF | 20.01 / 9.08 / 23.34 | 19.79 / 8.98 / 24.10 | ❌ | 55.75 / 11.57 / 57.67

###
V100 (batch size: 4)

Pipeline | torch 2.0 - no compile | torch nightly - no compile | torch 2.0 - compile | torch nightly - compile
--- | --- | --- | --- | ---
SD - txt2img | 5.96 | 5.89 | 6.83 | 6.86
SD - img2img | 5.90 | 5.91 | 6.81 | 6.82
SD - inpaint | 5.99 | 6.03 | 6.93 | 6.95
SD - controlnet | 4.26 | 4.29 | 4.92 | 4.93
IF | 15.41 | 14.76 | ❌ | 22.95

###
V100 (batch size: 16)

Pipeline | torch 2.0 - no compile | torch nightly - no compile | torch 2.0 - compile | torch nightly - compile
--- | --- | --- | --- | ---
SD - txt2img | 1.66 | 1.66 | 1.92 | 1.90
SD - img2img | 1.65 | 1.65 | 1.91 | 1.89
SD - inpaint | 1.69 | 1.69 | 1.95 | 1.93
SD - controlnet | 1.19 | 1.19 | OOM after warmup | 1.36
IF | 5.43 | 5.29 | ❌ | 7.06

###
T4 (batch size: 1)

Pipeline | torch 2.0 - no compile | torch nightly - no compile | torch 2.0 - compile | torch nightly - compile
--- | --- | --- | --- | ---
SD - txt2img | 6.9 | 6.95 | 7.3 | 7.56
SD - img2img | 6.84 | 6.99 | 7.04 | 7.55
SD - inpaint | 6.91 | 6.7 | 7.01 | 7.37
SD - controlnet | 4.89 | 4.86 | 5.35 | 5.48
IF | 17.42 / 2.47 / 18.52 | 16.96 / 2.45 / 18.69 | ❌ | 24.63 / 2.47 / 23.39

###
T4 (batch size: 4)

Pipeline | torch 2.0 - no compile | torch nightly - no compile | torch 2.0 - compile | torch nightly - compile
--- | --- | --- | --- | ---
SD - txt2img | 1.79 | 1.79 | 2.03 | 1.99
SD - img2img | 1.77 | 1.77 | 2.05 | 2.04
SD - inpaint | 1.81 | 1.82 | 2.09 | 2.09
SD - controlnet | 1.34 | 1.27 | 1.47 | 1.46
IF | 5.79 | 5.61 | ❌ | 7.39

###
T4 (batch size: 16)

Pipeline | torch 2.0 - no compile | torch nightly - no compile | torch 2.0 - compile | torch nightly - compile
--- | --- | --- | --- | ---
SD - txt2img | 2.34s | 2.30s | OOM after 2nd iteration | 1.99s
SD - img2img | 2.35s | 2.31s | OOM after warmup | 2.00s
SD - inpaint | 2.30s | 2.26s | OOM after 2nd iteration | 1.95s
SD - controlnet | OOM after 2nd iteration | OOM after 2nd iteration | OOM after warmup | OOM after warmup
IF * | 1.44 | 1.44 | ❌ | 1.94

###
RTX 3090 (batch size: 1)

Pipeline | torch 2.0 - no compile | torch nightly - no compile | torch 2.0 - compile | torch nightly - compile
--- | --- | --- | --- | ---
SD - txt2img | 22.56 | 22.84 | 23.84 | 25.69
SD - img2img | 22.25 | 22.61 | 24.1 | 25.83
SD - inpaint | 22.22 | 22.54 | 24.26 | 26.02
SD - controlnet | 16.03 | 16.33 | 17.38 | 18.56
IF | 27.08 / 9.07 / 31.23 | 26.75 / 8.92 / 31.47 | ❌ | 68.08 / 11.16 / 65.29

###
RTX 3090 (batch size: 4)

Pipeline | torch 2.0 - no compile | torch nightly - no compile | torch 2.0 - compile | torch nightly - compile
--- | --- | --- | --- | ---
SD - txt2img | 6.46 | 6.35 | 7.29 | 7.3
SD - img2img | 6.33 | 6.27 | 7.31 | 7.26
SD - inpaint | 6.47 | 6.4 | 7.44 | 7.39
SD - controlnet | 4.59 | 4.54 | 5.27 | 5.26
IF | 16.81 | 16.62 | ❌ | 21.57

###
RTX 3090 (batch size: 16)

Pipeline | torch 2.0 - no compile | torch nightly - no compile | torch 2.0 - compile | torch nightly - compile
--- | --- | --- | --- | ---
SD - txt2img | 1.7 | 1.69 | 1.93 | 1.91
SD - img2img | 1.68 | 1.67 | 1.93 | 1.9
SD - inpaint | 1.72 | 1.71 | 1.97 | 1.94
SD - controlnet | 1.23 | 1.22 | 1.4 | 1.38
IF | 5.01 | 5.00 | ❌ | 6.33

###
RTX 4090 (batch size: 1)

Pipeline | torch 2.0 - no compile | torch nightly - no compile | torch 2.0 - compile | torch nightly - compile
--- | --- | --- | --- | ---
SD - txt2img | 40.5 | 41.89 | 44.65 | 49.81
SD - img2img | 40.39 | 41.95 | 44.46 | 49.8
SD - inpaint | 40.51 | 41.88 | 44.58 | 49.72
SD - controlnet | 29.27 | 30.29 | 32.26 | 36.03
IF | 69.71 / 18.78 / 85.49 | 69.13 / 18.80 / 85.56 | ❌ | 124.60 / 26.37 / 138.79

###
RTX 4090 (batch size: 4)

Pipeline | torch 2.0 - no compile | torch nightly - no compile | torch 2.0 - compile | torch nightly - compile
--- | --- | --- | --- | ---
SD - txt2img | 12.62 | 12.84 | 15.32 | 15.59
SD - img2img | 12.61 | 12,.79 | 15.35 | 15.66
SD - inpaint | 12.65 | 12.81 | 15.3 | 15.58
SD - controlnet | 9.1 | 9.25 | 11.03 | 11.22
IF | 31.88 | 31.14 | ❌ | 43.92

###
RTX 4090 (batch size: 16)

Pipeline | torch 2.0 - no compile | torch nightly - no compile | torch 2.0 - compile | torch nightly - compile
--- | --- | --- | --- | ---
SD - txt2img | 3.17 | 3.2 | 3.84 | 3.85
SD - img2img | 3.16 | 3.2 | 3.84 | 3.85
SD - inpaint | 3.17 | 3.2 | 3.85 | 3.85
SD - controlnet | 2.23 | 2.3 | 2.7 | 2.75
IF | 9.26 | 9.2 | ❌ | 13.31

##
Notes

- Follow this PR for more details on the environment used for conducting the benchmarks.
- For the IF pipeline and batch sizes > 1, we only used a batch size of >1 in the first IF pipeline for text-to-image generation and NOT for upscaling. So, that means the two upscaling pipelines received a batch size of 1.

Thanks to Horace He from the PyTorch team for their support in improving our support of `torch.compile()` in Diffusers.