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[docs] Models (#12248)

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This commit is contained in:
Steven Liu
2025-09-05 11:52:09 -07:00
committed by GitHub
parent 32798bf242
commit fc337d5853
3 changed files with 128 additions and 33 deletions

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@@ -24,6 +24,8 @@
title: Reproducibility
- local: using-diffusers/schedulers
title: Load schedulers and models
- local: using-diffusers/models
title: Models
- local: using-diffusers/scheduler_features
title: Scheduler features
- local: using-diffusers/other-formats

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@@ -108,23 +108,20 @@ print(pipeline.transformer.dtype, pipeline.vae.dtype)
The `device_map` argument determines individual model or pipeline placement on an accelerator like a GPU. It is especially helpful when there are multiple GPUs.
Diffusers currently provides three options to `device_map`, `"cuda"`, `"balanced"` and `"auto"`. Refer to the table below to compare the three placement strategies.
A pipeline supports two options for `device_map`, `"cuda"` and `"balanced"`. Refer to the table below to compare the placement strategies.
| parameter | description |
|---|---|
| `"cuda"` | places model or pipeline on CUDA device |
| `"balanced"` | evenly distributes model or pipeline on all GPUs |
| `"auto"` | distribute model from fastest device first to slowest |
| `"cuda"` | places pipeline on a supported accelerator device like CUDA |
| `"balanced"` | evenly distributes pipeline on all GPUs |
Use the `max_memory` argument in [`~DiffusionPipeline.from_pretrained`] to allocate a maximum amount of memory to use on each device. By default, Diffusers uses the maximum amount available.
<hfoptions id="device_map">
<hfoption id="pipeline">
```py
import torch
from diffusers import DiffusionPipeline
max_memory = {0: "16GB", 1: "16GB"}
pipeline = DiffusionPipeline.from_pretrained(
"Qwen/Qwen-Image",
torch_dtype=torch.bfloat16,
@@ -132,26 +129,6 @@ pipeline = DiffusionPipeline.from_pretrained(
)
```
</hfoption>
<hfoption id="individual model">
```py
import torch
from diffusers import AutoModel
max_memory = {0: "16GB", 1: "16GB"}
transformer = AutoModel.from_pretrained(
"Qwen/Qwen-Image",
subfolder="transformer",
torch_dtype=torch.bfloat16
device_map="cuda",
max_memory=max_memory
)
```
</hfoption>
</hfoptions>
The `hf_device_map` attribute allows you to access and view the `device_map`.
```py
@@ -189,22 +166,18 @@ pipeline = DiffusionPipeline.from_pretrained(
[`DiffusionPipeline`] is flexible and accommodates loading different models or schedulers. You can experiment with different schedulers to optimize for generation speed or quality, and you can replace models with more performant ones.
The example below swaps the default scheduler to generate higher quality images and a more stable VAE version. Pass the `subfolder` argument in [`~HeunDiscreteScheduler.from_pretrained`] to load the scheduler to the correct subfolder.
The example below uses a more stable VAE version.
```py
import torch
from diffusers import DiffusionPipeline, HeunDiscreteScheduler, AutoModel
from diffusers import DiffusionPipeline, AutoModel
scheduler = HeunDiscreteScheduler.from_pretrained(
"stabilityai/stable-diffusion-xl-base-1.0", subfolder="scheduler"
)
vae = AutoModel.from_pretrained(
"madebyollin/sdxl-vae-fp16-fix", torch_dtype=torch.float16
)
pipeline = DiffusionPipeline.from_pretrained(
"stabilityai/stable-diffusion-xl-base-1.0",
scheduler=scheduler,
vae=vae,
torch_dtype=torch.float16,
device_map="cuda"

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@@ -0,0 +1,120 @@
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[[open-in-colab]]
# Models
A diffusion model relies on a few individual models working together to generate an output. These models are responsible for denoising, encoding inputs, and decoding latents into the actual outputs.
This guide will show you how to load models.
## Loading a model
All models are loaded with the [`~ModelMixin.from_pretrained`] method, which downloads and caches the latest model version. If the latest files are available in the local cache, [`~ModelMixin.from_pretrained`] reuses files in the cache.
Pass the `subfolder` argument to [`~ModelMixin.from_pretrained`] to specify where to load the model weights from. Omit the `subfolder` argument if the repository doesn't have a subfolder structure or if you're loading a standalone model.
```py
from diffusers import QwenImageTransformer2DModel
model = QwenImageTransformer2DModel.from_pretrained("Qwen/Qwen-Image", subfolder="transformer")
```
## AutoModel
[`AutoModel`] detects the model class from a `model_index.json` file or a model's `config.json` file. It fetches the correct model class from these files and delegates the actual loading to the model class. [`AutoModel`] is useful for automatic model type detection without needing to know the exact model class beforehand.
```py
from diffusers import AutoModel
model = AutoModel.from_pretrained(
"Qwen/Qwen-Image", subfolder="transformer"
)
```
## Model data types
Use the `torch_dtype` argument in [`~ModelMixin.from_pretrained`] to load a model with a specific data type. This allows you to load a model in a lower precision to reduce memory usage.
```py
import torch
from diffusers import QwenImageTransformer2DModel
model = QwenImageTransformer2DModel.from_pretrained(
"Qwen/Qwen-Image",
subfolder="transformer",
torch_dtype=torch.bfloat16
)
```
[nn.Module.to](https://docs.pytorch.org/docs/stable/generated/torch.nn.Module.html#torch.nn.Module.to) can also convert to a specific data type on the fly. However, it converts *all* weights to the requested data type unlike `torch_dtype` which respects `_keep_in_fp32_modules`. This argument preserves layers in `torch.float32` for numerical stability and best generation quality (see example [_keep_in_fp32_modules](https://github.com/huggingface/diffusers/blob/f864a9a352fa4a220d860bfdd1782e3e5af96382/src/diffusers/models/transformers/transformer_wan.py#L374))
```py
from diffusers import QwenImageTransformer2DModel
model = QwenImageTransformer2DModel.from_pretrained(
"Qwen/Qwen-Image", subfolder="transformer"
)
model = model.to(dtype=torch.float16)
```
## Device placement
Use the `device_map` argument in [`~ModelMixin.from_pretrained`] to place a model on an accelerator like a GPU. It is especially helpful where there are multiple GPUs.
Diffusers currently provides three options to `device_map` for individual models, `"cuda"`, `"balanced"` and `"auto"`. Refer to the table below to compare the three placement strategies.
| parameter | description |
|---|---|
| `"cuda"` | places pipeline on a supported accelerator (CUDA) |
| `"balanced"` | evenly distributes pipeline on all GPUs |
| `"auto"` | distribute model from fastest device first to slowest |
Use the `max_memory` argument in [`~ModelMixin.from_pretrained`] to allocate a maximum amount of memory to use on each device. By default, Diffusers uses the maximum amount available.
```py
import torch
from diffusers import QwenImagePipeline
max_memory = {0: "16GB", 1: "16GB"}
pipeline = QwenImagePipeline.from_pretrained(
"Qwen/Qwen-Image",
torch_dtype=torch.bfloat16,
device_map="cuda",
max_memory=max_memory
)
```
The `hf_device_map` attribute allows you to access and view the `device_map`.
```py
print(transformer.hf_device_map)
# {'': device(type='cuda')}
```
## Saving models
Save a model with the [`~ModelMixin.save_pretrained`] method.
```py
from diffusers import QwenImageTransformer2DModel
model = QwenImageTransformer2DModel.from_pretrained("Qwen/Qwen-Image", subfolder="transformer")
model.save_pretrained("./local/model")
```
For large models, it is helpful to use `max_shard_size` to save a model as multiple shards. A shard can be loaded faster and save memory (refer to the [parallel loading](./loading#parallel-loading) docs for more details), especially if there is more than one GPU.
```py
model.save_pretrained("./local/model", max_shard_size="5GB")
```