From English to Code-Switching: Transfer Learning with Strong Morphological Clues (ACL 2020)

Authors: Gustavo Aguilar and Thamar Solorio

This repository contains the implementations of the CS-ELMo model introduced in the paper "From English to Code-Switching: Transfer Learning with Strong Morphological Clues" at ACL 2020.

The main contribution of this model is the enhanced character n-gram module (the highlighted component from the image). Please refer to the paper for details.

Installation

We have updated the code to work with Python 3.8, PyTorch 1.6, CUDA 10.2. If you use conda, you can set up the environment as follows:

conda create -n cselmo python=3.8
conda activate cselmo
conda install pytorch==1.6 cudatoolkit=10.2 -c pytorch

Also, install the dependencies specified in the requirements.txt:

pip install -r requirements.txt

Data

This repo contains dataset files that serve as templates for the sake of the example. Please replace the files with your data. You can either add a new directory in CS_ELMo/data/your_dataset_dir or replace the content of one of the existing dataset directories. Make sure you provide the correct paths to the data split in the config file. For example, CS_ELMo/configs/lid.spaeng.exp3.3.json contains this:

    ...
    "dataset": {
        "train": "lid_calcs16_spaeng/train.txt",
        "dev": "lid_calcs16_spaeng/dev.txt",
        "test": "lid_calcs16_spaeng/test.txt"
    },

Running

There are two main stages to run this project.

1. Code-switching adaptation with LID
2. Code-switching downstream fine-tuning

We use config files to specify the details for every experiment (e.g., hyper-parameters, datasets, etc.). You can use or modify any config file from the CS_ELMo/configs directory.

1. Code-switching adaptation with LID

We use multi-task learning (MTL) with the full and simplified LID label schemes. To train this model in the MTL setting, make sure the config file contains the "use_second_task" field:

"model": {
    ...
    "charngrams": {
        "use_second_task": true,
        ...
    }
}

You can train a model from pre-defined config files from this repo like this (Exp3.3 from the paper):

python src/main.py --config configs/lid.spaeng.exp3.3.json --gpu 0

The gpu argument specifies the GPU label and is optional. If gpu is not provided, the code runs on CPU.

The code saves a model checkpoint after every epoch if the model improves (either lower loss or higher metric). You will notice that a directory is created using the experiment id (e.g., CS_ELMo/checkpoints/lid.spaeng.exp3.3/). You can resume training by running the same command.

To evaluate the model, use --mode eval (default: train):

python src/main.py --config configs/lid.spaeng.exp3.3.json --gpu 0 --mode eval

2. Code-switching downstream fine-tuning

Now you can load the CS-adapted model (a.k.a CS-ELMo) and fine-tune it to downstream tasks like NER or POS tagging. Here's an example for NER (Exp 5.2 from the paper):

python src/main.py --config configs/ner.spaeng.exp5.2.json --gpu 0

The config contains the following fields to do the fine-tuning:

    ...
    "pretrained_config": {
        "path": "configs/lid.spaeng.exp3.3.json",
        "pretrained_part": "elmo",
        "finetuning_mode": "frozen_elmo"
    }

the fine-tuning mode can be any option from ['fully_trainable', 'frozen_elmo', 'inference'], and the pre-trained part can be either just the CS-ELMo architecture (i.e., "elmo") or using possible weights that resemble the new model such as BLSTM, word embeddings, and the simplified LID inference layer (i.e., "full").

Visualizations

We have added a Javascript/HTML script to visualize the attention weights in the hierarchical model. The tool is located at CS_ELMO/visualization/attention.html, and you will need to load a JSON file containing the attention weights. This JSON file is automatically generated after evaluating a model. Here's an example of how the tool works:

Citation

@inproceedings{aguilar-solorio-2020-english,
    title = "From {E}nglish to Code-Switching: Transfer Learning with Strong Morphological Clues",
    author = "Aguilar, Gustavo  and Solorio, Thamar",
    booktitle = "Proceedings of the 58th Annual Meeting of the Association for Computational Linguistics",
    month = jul,
    year = "2020",
    address = "Online",
    publisher = "Association for Computational Linguistics",
    url = "https://www.aclweb.org/anthology/2020.acl-main.716",
    doi = "10.18653/v1/2020.acl-main.716",
    pages = "8033--8044"
}

Contact

Feel free to get in touch via email to gaguilaralas@uh.edu.