🤗 PEFT-RoSA

This repository is a fork of the huggingface Parameter-Efficient Fine-Tuning (PEFT) library, containing the official implementation for the paper Robust Adaptation (RoSA). The RoSA-related code can be found in src/peft/tuners/rosa/. Also here, we have integrated this library into MosaicML's llm-foundry, containing the experiments reported in the paper.

Installation

1. Make sure you have pytorch installed. Preferably, install pytorch using conda instead of pip to ensure the dependencies are installed correctly.
2. Install the spops library, which we use under the hood to perform sparse operations. Simply run

pip install git+https://github.com/IST-DASLab/spops.git

3. Finally, clone this repository and run

pip install -e .

Usage

The usage is almost identical to LoRA in the PEFT library, with some extra configuration parameters in RosaConfig + a single line of code adding a RosaScheduler. The required changes are shown in the code block below.

from transformers import AutoModelForSeq2SeqLM
from peft import get_peft_model, TaskType
from peft.tuners.rosa import RosaConfig, RosaScheduler
model_name_or_path = "bigscience/mt0-large"

peft_config = RosaConfig(
    task_type=TaskType.SEQ_2_SEQ_LM,
    r=8,
    lora_alpha=32,
    lora_dropout=0.1,

    d=0.006,                                |
    spa_num_grads=1,                        |   <---- the new config parameters 
    grad_acc_mode='mean_squared',           |
    schedule='wl64'                         |
)

model = AutoModelForSeq2SeqLM.from_pretrained(model_name_or_path)
model = get_peft_model(model, peft_config)

trainer = Trainer(
    model=model,
    ...,
    callbacks=[RosaScheduler(model)]        |   <---- add RosaScheduler as a callback
)

The new config parameters, in line with the paper, are the following ones:

• d: Density of the sparse adaptation matrix.
• spa_num_grads: How many batches of gradients to use for RoSA mask generation. One batch (the default value) usually works well.
• grad_acc_mode: How to accumulate the gradients. mean_squared corresponds to the empirical diagonal Fisher estimation, while mean corresponds to simply averaging the gradients. mean_squared is default, and usually obtains good results.
• schedule: TL;DR just use wl64 to warm up with only low-rank adapter for 64 steps, and then start collecting gradients for sparse adaptation's mask generation. See the next section for a complete guide.

Finally, just add RosaScheduler(model) as a callback to the Trainer. RosaScheduler is also compatible with MosaicML's composer (just add it as an Algorithm). Additionally, you can customize it for any other framework by calling scheduler's _on_step_begin() and _on_step_end() before forward and after backward, respectively.

RoSA Schedule

The schedule argument in RosaConfig determines when each of low-rank and sparse adapters should be active, and when to generate the sparsity masks. The (currently) supported options are discussed below.

• default: the sparse and low-rank adapters will be enabled as soon as possible. This means that the low-rank adapter is always activated, and gradient collection will start right away and the sparse adapter will be activated once the masks are generated.
• lora_only: the low-rank adapter is always active, while the sparse adapter is disabled.
• spa_only: the low-rank adapter is always disabled, while the sparse adapter will be activated once enough gradients are collected.
• wl64 (or wl + any number): start by fine-tuning the low-rank adapter alone for 64 steps, then collect gradients as long as needed and activate sparse adaptation.

Finally, as discussed in the paper, we found it beneficial to warm up with low-rank adapter only (wl64 schedule), generate the masks, and then restart the training with both adapters activated. To do this, we suggest following the steps below, taking advantage of three extra parameters in RosaConfig.

1. First run your RoSA training with schedule=wl64, mask_save_path=./tmp_mask, and terminate_after_mask_generation=True passed into RosaConfig, which saves the generated mask (after low-rank warmup) in the ./tmp_mask file and terminates the run.
2. Re-run the training with schedule=default and mask_load_path=./tmp_mask, which loads the masks directly from the file and activates both low-rank and sparse adapters right away.

Citation

If you plan to use our work in your projects, please consider citing our paper:

@article{nikdan2024rosa,
  title={RoSA: Accurate Parameter-Efficient Fine-Tuning via Robust Adaptation},
  author={Nikdan, Mahdi and Tabesh, Soroush and Crnčević, Elvir and Alistarh, Dan},
  journal={arXiv preprint arXiv:2401.04679},
  year={2024}
}