transformers/examples/research_projects/self-training-text-classification

Self-training

This is an implementation of the self-training algorithm (without task augmentation) in the EMNLP 2021 paper: STraTA: Self-Training with Task Augmentation for Better Few-shot Learning. Please check out https://github.com/google-research/google-research/tree/master/STraTA for the original codebase.

Note: The code can be used as a tool for automatic data labeling.

Table of Contents

• Installation
• Self-training
  • Running self-training with a base model
  • Hyperparameters for self-training
  • Distributed training
• Demo
• How to cite

Installation

This repository is tested on Python 3.8+, PyTorch 1.10+, and the 🤗 Transformers 4.16+.

You should install all necessary Python packages in a virtual environment. If you are unfamiliar with Python virtual environments, please check out the user guide.

Below, we create a virtual environment with the Anaconda Python distribution and activate it.

conda create -n strata python=3.9
conda activate strata

Next, you need to install 🤗 Transformers. Please refer to 🤗 Transformers installation page for a detailed guide.

pip install transformers

Finally, install all necessary Python packages for our self-training algorithm.

pip install -r STraTA/selftraining/requirements.txt

This will install PyTorch as a backend.

Self-training

Running self-training with a base model

The following example code shows how to run our self-training algorithm with a base model (e.g., BERT) on the SciTail science entailment dataset, which has two classes ['entails', 'neutral']. We assume that you have a data directory that includes some training data (e.g., train.csv), evaluation data (e.g., eval.csv), and unlabeled data (e.g., infer.csv).

import os
from selftraining import selftrain

data_dir = '/path/to/your/data/dir'
parameters_dict = {
    'max_selftrain_iterations': 100,
    'model_name_or_path': '/path/to/your/base/model',  # could be the id of a model hosted by 🤗 Transformers
    'output_dir': '/path/to/your/output/dir',
    'train_file': os.path.join(data_dir, 'train.csv'),
    'infer_file': os.path.join(data_dir, 'infer.csv'),
    'eval_file': os.path.join(data_dir, 'eval.csv'),
    'eval_strategy': 'steps',
    'task_name': 'scitail',
    'label_list': ['entails', 'neutral'],
    'per_device_train_batch_size': 32,
    'per_device_eval_batch_size': 8,
    'max_length': 128,
    'learning_rate': 2e-5,
    'max_steps': 100000,
    'eval_steps': 1,
    'early_stopping_patience': 50,
    'overwrite_output_dir': True,
    'do_filter_by_confidence': False,
    # 'confidence_threshold': 0.3,
    'do_filter_by_val_performance': True,
    'finetune_on_labeled_data': False,
    'seed': 42,
}
selftrain(**parameters_dict)

Note: We checkpoint periodically during self-training. In case of preemptions, just re-run the above script and self-training will resume from the latest iteration.

Hyperparameters for self-training

If you have development data, you might want to tune some hyperparameters for self-training. Below are hyperparameters that could provide additional gains for your task.

• finetune_on_labeled_data: If set to True, the resulting model from each self-training iteration is further fine-tuned on the original labeled data before the next self-training iteration. Intuitively, this would give the model a chance to "correct" ifself after being trained on pseudo-labeled data.
• do_filter_by_confidence: If set to True, the pseudo-labeled data in each self-training iteration is filtered based on the model confidence. For instance, if confidence_threshold is set to 0.3, pseudo-labeled examples with a confidence score less than or equal to 0.3 will be discarded. Note that confidence_threshold should be greater or equal to 1/num_labels, where num_labels is the number of class labels. Filtering out the lowest-confidence pseudo-labeled examples could be helpful in some cases.
• do_filter_by_val_performance: If set to True, the pseudo-labeled data in each self-training iteration is filtered based on the current validation performance. For instance, if your validation performance is 80% accuracy, you might want to get rid of 20% of the pseudo-labeled data with the lowest the confidence scores.

Distributed training

We strongly recommend distributed training with multiple accelerators. To activate distributed training, please try one of the following methods:

1. Run accelerate config and answer to the questions asked. This will save a default_config.yaml file in your cache folder for 🤗 Accelerate. Now, you can run your script with the following command:

accelerate launch your_script.py --args_to_your_script

2. Run your script with the following command:

python -m torch.distributed.launch --nnodes="{$NUM_NODES}" --nproc_per_node="{$NUM_TRAINERS}" --your_script.py --args_to_your_script

3. Run your script with the following command:

torchrun --nnodes="{$NUM_NODES}" --nproc_per_node="{$NUM_TRAINERS}" --your_script.py --args_to_your_script

Demo

Please check out run.sh to see how to perform our self-training algorithm with a BERT Base model on the SciTail science entailment dataset using 8 labeled examples per class. You can configure your training environment by specifying NUM_NODES and NUM_TRAINERS (number of processes per node). To launch the script, simply run source run.sh.

How to cite

If you extend or use this code, please cite the paper where it was introduced:

@inproceedings{vu-etal-2021-strata,
    title = "{ST}ra{TA}: Self-Training with Task Augmentation for Better Few-shot Learning",
    author = "Vu, Tu  and
      Luong, Minh-Thang  and
      Le, Quoc  and
      Simon, Grady  and
      Iyyer, Mohit",
    booktitle = "Proceedings of the 2021 Conference on Empirical Methods in Natural Language Processing",
    month = nov,
    year = "2021",
    address = "Online and Punta Cana, Dominican Republic",
    publisher = "Association for Computational Linguistics",
    url = "https://aclanthology.org/2021.emnlp-main.462",
    doi = "10.18653/v1/2021.emnlp-main.462",
    pages = "5715--5731",
}