Finetuning with LoRA

Low-rank adaption (LoRA) is a technique to approximate the update to the linear layers in a LLM with a low-rank matrix factorization. This significantly reduces the number of trainable parameters and speeds up training with little impact on the final performance of the model. We demonstrate this method by instruction-finetuning LLaMA 7B on the Alpaca dataset on a single GTX 3090 (24GB) GPU.

Preparation

The steps here only need to be done once:

Follow the instructions in the README to install the dependencies.
Download and convert the weights and save them in the ./checkpoints folder as described here.
Download the data and generate the instruction tuning dataset:
```
python scripts/prepare_alpaca.py
```

Running the finetuning

python finetune_lora.py

The finetuning requires at least one GPU with ~24 GB memory (GTX 3090).

This script will save checkpoints periodically to the folder out/.

Note All scripts support argument customization

Test the model

You can test the finetuned model with your own instructions by running:

python generate_lora.py --prompt "Recommend a movie to watch on the weekend."

Output:

I would recommend the movie The Martian (2015). It is a sci-fi movie starring Matt Damon that follows the story of...

If your GPU supports bfloat16, you can additionally pass --dtype bfloat16 to bring the memory consumption down to ~14 GB.

Tune on your dataset

With only a few modifications, you can prepare and train on your own instruction dataset.

Create a json file in which each row holds one instruction-response pair. A row has an entry for 'instruction', 'input', and 'output', where 'input' is optional an can be the empty string if the instruction doesn't require a context. Below is an example json file:
```
[
    {
        "instruction": "Arrange the given numbers in ascending order.",
        "input": "2, 4, 0, 8, 3",
        "output": "0, 2, 3, 4, 8"
    },
    ...
]
```
Make a copy of scripts/prepare_alpaca.py and name it what you want:
```
cp scripts/prepare_alpaca.py scripts/prepare_mydata.py
```
Modify scripts/prepare_mydata.py to read the json data file.
Run the script to generate the preprocessed, tokenized train-val split:
```
python scripts/prepare_mydata.py --destination_path data/mydata/
```
Run finetune_lora.py by passing in the location of your data (and optionally other parameters):
```
python finetune_lora.py --data_dir data/mydata/ --out_dir out/myexperiment
```

Troubleshooting

If you run into a CUDA error "Expected is_sm80 to be true, but got false", uncomment the line torch.backends.cuda.enable_flash_sdp(False) in the script below (see https://github.com/Lightning-AI/lit-llama/issues/101).