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nemo
61 lines
3.0 KiB
Plaintext
61 lines
3.0 KiB
Plaintext
# Parameter efficient fine-tuning with 🤗 PEFT
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[🤗 PEFT](https://github.com/huggingface/peft) (Parameter-Efficient Fine-Tuning) is a library for efficiently adapting
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large pretrained models such as pre-trained policies (e.g., SmolVLA, π₀, ...) to new tasks without training all
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of the model's parameters while yielding comparable performance.
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To read about all the possible methods of adaption, please refer to the [🤗 PEFT docs](https://huggingface.co/docs/peft/index).
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## Training SmolVLA
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In this section we'll show you how to train a pre-trained SmolVLA policy with PEFT on the libero dataset.
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For brevity we're only training on the `libero_spatial` subset. We will use `lerobot/smolvla_base` as the model
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to parameter efficiently fine-tune:
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```
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lerobot-train \
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--policy.path=lerobot/smolvla_base \
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--policy.repo_id=your_hub_name/my_libero_smolvla \
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--dataset.repo_id=HuggingFaceVLA/libero \
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--policy.output_features=null \
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--policy.input_features=null \
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--policy.optimizer_lr=1e-3 \
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--policy.scheduler_decay_lr=1e-4 \
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--env.type=libero \
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--env.task=libero_spatial \
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--steps=100000 \
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--batch_size=32 \
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--peft.method_type=LORA \
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--peft.r=64
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```
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Note the `--peft.method_type` parameter that let's you select which PEFT method to use. Here we use
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[LoRA](https://huggingface.co/docs/peft/main/en/package_reference/lora) (Low-Rank Adapter) which is probably the most
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popular fine-tuning method to date. Low-rank adaption means that we only fine-tune a matrix with comparably low rank
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instead of the full weight matrix. This rank can be specified using the `--peft.r` parameter. The higher the rank
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the closer you get to full fine-tuning
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There are more complex methods that have more parameters. These are not yet supported, feel free to raise an issue
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if you want to see a specific PEFT method supported.
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By default, PEFT will target the `q_proj` and `v_proj` layers of the LM expert in SmolVLA. It will also target the
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state and action projection matrices as they are most likely taks-dependent. If you need to target different layers
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you can use `--peft.target_modules` to specify which layers to target. You can refer to the respective PEFT method's
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documentation to see what inputs are supported, (e.g., [LoRA's target_modules documentation](https://huggingface.co/docs/peft/main/en/package_reference/lora#peft.LoraConfig.target_modules)).
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Usually a list of suffixes or a regex are supported. For example, to target the MLPs of the `lm_expert` instead of
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the `q` and `v` projections, use:
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```
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--peft.target_modules='(model\.vlm_with_expert\.lm_expert\..*\.(down|gate|up)_proj|.*\.(state_proj|action_in_proj|action_out_proj|action_time_mlp_in|action_time_mlp_out))'
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```
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In case you need to fully fine-tune a layer instead of just adapting it, you can supply a list of layer suffixes
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to the `--peft.full_training_modules` parameter:
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```
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--peft.full_training_modules=["state_proj"]
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```
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The learning rate and the scheduled target learning rate can usually be scaled by a factor of 10 compared to the
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learning rate used for full fine-tuning (e.g., 1e-4 normal, so 1e-3 using LoRA).
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