Learning with Rejection for Abstractive Text Summarization

This directory contains code necessary to replicate the training and evaluation for our EMNLP 2022 paper "Learning with Rejection for Abstractive Text Summarization" by Meng Cao, Yue Dong, Jingyi He and Jackie Chi Kit Cheung.

Our implementation is heavily based on facebook's fairseq library. The core implementation of the algorithm is in the fairseq/criterions/label_smoothed_cross_entropy_with_rejection.py file.

Requirements and Installation

• PyTorch version >= 1.10.0
• Python version >= 3.8
• spaCy >= 3.4.4
• rouge-score
• For training new models, you'll also need an NVIDIA GPU and NCCL
• To install and develop locally:

git clone https://github.com/mcao516/rej-summ.git
cd rej-summ
pip install --editable ./

Running the Code

To reproduce the results in the paper, you can download the pre-processed XSum dataset from google drive using this link. Besides the document and reference files, the pre-processed dataset contains mask files that mark the position of entities in the sentence.

We need the entity position information since we only apply rejection loss on entities. This is because the uncertainty over tokens contains not only uncertainty about the factuality of the generated information, but also uncertainty about the different possible paraphrasing of the summary. For entities, it is mainly the former.

Training

TOTAL_NUM_UPDATES=20000
WARMUP_UPDATES=500      
LR=3e-05
MAX_TOKENS=2048
UPDATE_FREQ=2

BART_PATH=${HOME}/BART_models/bart.large/model.pt
DATA_PATH=${HOME}/summarization/XSum/xsum-bin
SAVE_DIR=checkpoints/
mkdir $SAVE_DIR

CUDA_VISIBLE_DEVICES=0,1,2,3,4,5,6,7 fairseq-train $DATA_PATH \
    --max-epoch 3 \
    --abstention-mask-dir ${HOME}/summarization/XSum/masks/ \
    --rejection-alpha 1.0 \
    --restore-file $BART_PATH \
    --save-dir $SAVE_DIR \
    --max-tokens $MAX_TOKENS \
    --task translation \
    --source-lang source --target-lang target \
    --truncate-source \
    --layernorm-embedding \
    --share-all-embeddings \
    --share-decoder-input-output-embed \
    --reset-optimizer --reset-dataloader --reset-meters \
    --required-batch-size-multiple 1 \
    --arch bart_large \
    --criterion label_smoothed_cross_entropy_with_rejection \
    --label-smoothing 0.1 \
    --dropout 0.1 --attention-dropout 0.1 \
    --weight-decay 0.01 --optimizer adam --adam-betas "(0.9, 0.999)" --adam-eps 1e-08 \
    --clip-norm 0.1 \
    --lr-scheduler polynomial_decay --lr $LR --total-num-update $TOTAL_NUM_UPDATES --warmup-updates $WARMUP_UPDATES \
    --fp16 --update-freq $UPDATE_FREQ \
    --skip-invalid-size-inputs-valid-test \
    --find-unused-parameters;

Inference

DATA_PATH=${HOME}/summarization/XSum/xsum-bin
SRC_PATH=$HOME/summarization/XSum/test.source
OUTPUT_PATH=hypos/output.hypo

CUDA_VISIBLE_DEVICES=0 python examples/bart/summarize.py \
    --model-dir checkpoints/ \
    --model-file checkpoint_best.pt \
    --dict-dir $DATA_PATH \
    --src $SRC_PATH \
    --out $OUTPUT_PATH \
    --beam_size 6 \
    --bsz 8 \
    --unnormalized \
    --lenpen 1.0 \
    --rejpen 2.0 \
    --xsum-kwargs;

Running the Code on Your Own Data

To run the code on your own data, first make sure that the data is formatted as one document/summary per line. Then, binarize your data following the steps here: https://github.com/mcao516/rej-summ/blob/main/examples/bart/README.summarization.md. You also need to run preprocessing.py to generate a mask file that contains the entity position information.

License

fairseq(-py) is MIT-licensed. The license applies to the pre-trained models as well.

Citation

Please cite as:

@inproceedings{cao-etal-2022-learning,
    title = "Learning with Rejection for Abstractive Text Summarization",
    author = "Cao, Meng  and
      Dong, Yue  and
      He, Jingyi  and
      Cheung, Jackie Chi Kit",
    booktitle = "Proceedings of the 2022 Conference on Empirical Methods in Natural Language Processing",
    month = dec,
    year = "2022",
    address = "Abu Dhabi, United Arab Emirates",
    publisher = "Association for Computational Linguistics",
    url = "https://aclanthology.org/2022.emnlp-main.663",
    pages = "9768--9780",
    abstract = "State-of-the-art abstractive summarization systems frequently hallucinate content that is not supported by the source document, mainly due to noise in the training dataset.Existing methods opt to drop the noisy samples or tokens from the training set entirely, reducing the effective training set size and creating an artificial propensity to copy words from the source. In this work, we propose a training objective for abstractive summarization based on rejection learning, in which the model learns whether or not to reject potentially noisy tokens. We further propose a regularized decoding objective that penalizes non-factual candidate summaries during inference by using the rejection probability learned during training.We show that our method considerably improves the factuality of generated summaries in automatic and human evaluations when compared to five baseline models, and that it does so while increasing the abstractiveness of the generated summaries.",
}