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| 9 | +an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the |
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| 13 | + |
| 14 | +# Quanto |
| 15 | + |
| 16 | +[Quanto](https://github.com/huggingface/optimum-quanto) is a PyTorch quantization backend for [Optimum](https://huggingface.co/docs/optimum/en/index). It has been designed with versatility and simplicity in mind: |
| 17 | + |
| 18 | +- All features are available in eager mode (works with non-traceable models) |
| 19 | +- Supports quantization aware training |
| 20 | +- Quantized models are compatible with `torch.compile` |
| 21 | +- Quantized models are Device agnostic (e.g CUDA,XPU,MPS,CPU) |
| 22 | + |
| 23 | +In order to use the Quanto backend, you will first need to install `optimum-quanto>=0.2.6` and `accelerate` |
| 24 | + |
| 25 | +```shell |
| 26 | +pip install optimum-quanto accelerate |
| 27 | +``` |
| 28 | + |
| 29 | +Now you can quantize a model by passing the `QuantoConfig` object to the `from_pretrained()` method. Although the Quanto library does allow quantizing `nn.Conv2d` and `nn.LayerNorm` modules, currently, Diffusers only supports quantizing the weights in the `nn.Linear` layers of a model. The following snippet demonstrates how to apply `float8` quantization with Quanto. |
| 30 | + |
| 31 | +```python |
| 32 | +import torch |
| 33 | +from diffusers import FluxTransformer2DModel, QuantoConfig |
| 34 | + |
| 35 | +model_id = "black-forest-labs/FLUX.1-dev" |
| 36 | +quantization_config = QuantoConfig(weights_dtype="float8") |
| 37 | +transformer = FluxTransformer2DModel.from_pretrained( |
| 38 | + model_id, |
| 39 | + subfolder="transformer", |
| 40 | + quantization_config=quantization_config, |
| 41 | + torch_dtype=torch.bfloat16, |
| 42 | +) |
| 43 | + |
| 44 | +pipe = FluxPipeline.from_pretrained(model_id, transformer=transformer, torch_dtype=torch_dtype) |
| 45 | +pipe.to("cuda") |
| 46 | + |
| 47 | +prompt = "A cat holding a sign that says hello world" |
| 48 | +image = pipe( |
| 49 | + prompt, num_inference_steps=50, guidance_scale=4.5, max_sequence_length=512 |
| 50 | +).images[0] |
| 51 | +image.save("output.png") |
| 52 | +``` |
| 53 | + |
| 54 | +## Skipping Quantization on specific modules |
| 55 | + |
| 56 | +It is possible to skip applying quantization on certain modules using the `modules_to_not_convert` argument in the `QuantoConfig`. Please ensure that the modules passed in to this argument match the keys of the modules in the `state_dict` |
| 57 | + |
| 58 | +```python |
| 59 | +import torch |
| 60 | +from diffusers import FluxTransformer2DModel, QuantoConfig |
| 61 | + |
| 62 | +model_id = "black-forest-labs/FLUX.1-dev" |
| 63 | +quantization_config = QuantoConfig(weights_dtype="float8", modules_to_not_convert=["proj_out"]) |
| 64 | +transformer = FluxTransformer2DModel.from_pretrained( |
| 65 | + model_id, |
| 66 | + subfolder="transformer", |
| 67 | + quantization_config=quantization_config, |
| 68 | + torch_dtype=torch.bfloat16, |
| 69 | +) |
| 70 | +``` |
| 71 | + |
| 72 | +## Using `from_single_file` with the Quanto Backend |
| 73 | + |
| 74 | +`QuantoConfig` is compatible with `~FromOriginalModelMixin.from_single_file`. |
| 75 | + |
| 76 | +```python |
| 77 | +import torch |
| 78 | +from diffusers import FluxTransformer2DModel, QuantoConfig |
| 79 | + |
| 80 | +ckpt_path = "https://huggingface.co/black-forest-labs/FLUX.1-dev/blob/main/flux1-dev.safetensors" |
| 81 | +quantization_config = QuantoConfig(weights_dtype="float8") |
| 82 | +transformer = FluxTransformer2DModel.from_single_file(ckpt_path, quantization_config=quantization_config, torch_dtype=torch.bfloat16) |
| 83 | +``` |
| 84 | + |
| 85 | +## Saving Quantized models |
| 86 | + |
| 87 | +Diffusers supports serializing Quanto models using the `~ModelMixin.save_pretrained` method. |
| 88 | + |
| 89 | +The serialization and loading requirements are different for models quantized directly with the Quanto library and models quantized |
| 90 | +with Diffusers using Quanto as the backend. It is currently not possible to load models quantized directly with Quanto into Diffusers using `~ModelMixin.from_pretrained` |
| 91 | + |
| 92 | +```python |
| 93 | +import torch |
| 94 | +from diffusers import FluxTransformer2DModel, QuantoConfig |
| 95 | + |
| 96 | +model_id = "black-forest-labs/FLUX.1-dev" |
| 97 | +quantization_config = QuantoConfig(weights_dtype="float8") |
| 98 | +transformer = FluxTransformer2DModel.from_pretrained( |
| 99 | + model_id, |
| 100 | + subfolder="transformer", |
| 101 | + quantization_config=quantization_config, |
| 102 | + torch_dtype=torch.bfloat16, |
| 103 | +) |
| 104 | +# save quantized model to reuse |
| 105 | +transformer.save_pretrained("<your quantized model save path>") |
| 106 | + |
| 107 | +# you can reload your quantized model with |
| 108 | +model = FluxTransformer2DModel.from_pretrained("<your quantized model save path>") |
| 109 | +``` |
| 110 | + |
| 111 | +## Using `torch.compile` with Quanto |
| 112 | + |
| 113 | +Currently the Quanto backend supports `torch.compile` for the following quantization types: |
| 114 | + |
| 115 | +- `int8` weights |
| 116 | + |
| 117 | +```python |
| 118 | +import torch |
| 119 | +from diffusers import FluxPipeline, FluxTransformer2DModel, QuantoConfig |
| 120 | + |
| 121 | +model_id = "black-forest-labs/FLUX.1-dev" |
| 122 | +quantization_config = QuantoConfig(weights_dtype="int8") |
| 123 | +transformer = FluxTransformer2DModel.from_pretrained( |
| 124 | + model_id, |
| 125 | + subfolder="transformer", |
| 126 | + quantization_config=quantization_config, |
| 127 | + torch_dtype=torch.bfloat16, |
| 128 | +) |
| 129 | +transformer = torch.compile(transformer, mode="max-autotune", fullgraph=True) |
| 130 | + |
| 131 | +pipe = FluxPipeline.from_pretrained( |
| 132 | + model_id, transformer=transformer, torch_dtype=torch_dtype |
| 133 | +) |
| 134 | +pipe.to("cuda") |
| 135 | +images = pipe("A cat holding a sign that says hello").images[0] |
| 136 | +images.save("flux-quanto-compile.png") |
| 137 | +``` |
| 138 | + |
| 139 | +## Supported Quantization Types |
| 140 | + |
| 141 | +### Weights |
| 142 | + |
| 143 | +- float8 |
| 144 | +- int8 |
| 145 | +- int4 |
| 146 | +- int2 |
| 147 | + |
| 148 | + |
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