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README.md

BERT for Keyphrase Extraction (Pytorch)

This repository provides the code of the paper Joint Keyphrase Chunking and Salience Ranking with BERT.

In this paper, we conduct an empirical study of 5 keyphrase extraction models with 3 BERT variants, and then propose a multi-task model BERT-JointKPE. Experiments on two KPE benchmarks, OpenKP with Bing web pages and KP20K demonstrate JointKPE’s state-of-the-art and robust effectiveness. Our further analyses also show that JointKPE has advantages in predicting long keyphrases and non-entity keyphrases, which were challenging for previous KPE techniques.

Please cite our paper if our experimental results, analysis conclusions or the code are helpful to you ~ :)

@misc{sun2020joint,
    title={Joint Keyphrase Chunking and Salience Ranking with BERT},
    author={Si Sun and Chenyan Xiong and Zhenghao Liu and Zhiyuan Liu and Jie Bao},
    year={2020},
    eprint={2004.13639},
    archivePrefix={arXiv},
    primaryClass={cs.CL}
}

🤠 What's New ?

  • 2020/9/5

    Compared with the OpenKP dataset we downloaded from MS MARCO in October of 2019 (all our experiments are based on this version of the dataset), we found that the dataset has been updated. We remind you to download the latest data from the official website. For comparison, we also provide the data version we use. (The dataset version issue was raised by Yansen Wang et al from CMU, thank them ! )

    ~DownLoad from Tsinghua Cloud or ~Email s-sun17@mails.tsinghua.edu.cn for Data

* Model Classes

Index Model Descriptions
1 BERT-JointKPE (Bert2Joint) A multi-task model is trained jointly on the chunking task and the ranking task, balancing the estimation of keyphrase quality and salience.
2 BERT-RankKPE (Bert2Rank) Learn the salience phrases in the documents using a ranking network.
3 BERT-ChunkKPE (Bert2Chunk) Classify high quality keyphrases using a chunking network.
4 BERT-TagKPE (Bert2Tag) We modified the sequence tagging model to generate enough candidate keyphrases for a document.
5 BERT-SpanKPE (Bert2Span) We modified the span extraction model to extract multiple keyphrases from a document.

* BERT Variants

QUICKSTART

python 3.5
Pytorch 1.3.0
Tensorflow (tested on 1.14.0, only for tensorboardX)

1/ Download

  • First download and decompress our data folder to this repo, the folder includes benchmark datasets and pre-trained BERT variants.

  • We also provide 15 checkpoints (5 KPE models * 3 BERT variants) trained on OpenKP training dataset.

2/ Preprocess

  • To preprocess the source datasets using preprocess.sh in the preprocess folder:

    source preprocess.sh
    
  • Optional arguments:

    --dataset_class         choices=['openkp', 'kp20k']
    --source_dataset_dir    The path to the source dataset
    --output_path           The dir to save preprocess data; default: ../data/prepro_dataset
    

3/ Train Models

  • To train a new model from scratch using train.sh in the scripts folder:

    source train.sh
    

    PS. Running the training script for the first time will take some time to perform preprocess such as tokenization, and by default, the processed features will be saved under ../data/cached_features, which can be directly loaded next time.

  • Optional arguments:

    --dataset_class         choices=['openkp', 'kp20k']
    --model_class           choices=['bert2span', 'bert2tag', 'bert2chunk', 'bert2rank', 'bert2joint']
    --pretrain_model_type   choices=['bert-base-cased', 'spanbert-base-cased', 'roberta-base']
    

    Complete optional arguments can be seen in config.py in the scripts folder.

  • Training Parameters:

    We always keep the following settings in all our experiments:

    args.warmup_proportion = 0.1
    args.max_train_steps = 20810 (openkp) , 73430 (kp20k)
    args.per_gpu_train_batch_size * max(1, args.n_gpu) * args.gradient_accumulation_steps = 64
    
  • Distributed Training

    We recommend using DistributedDataParallel to train models on multiple GPUs (It's faster than DataParallel, but it will take up more memory)

    CUDA_VISIBLE_DEVICES=0,1 OMP_NUM_THREADS=2 python -m torch.distributed.launch --nproc_per_node=2 --master_port=1234 train.py
    # if you use DataParallel rather than DistributedDataParallel, remember to set --local_rank=-1
    

4/ Inference

  • To evaluate models using trained checkpoints using test.sh in the scripts folder:

    source test.sh
    
  • Optional arguments:

    --dataset_class         choices=['openkp', 'kp20k']
    --model_class           choices=['bert2span', 'bert2tag', 'bert2chunk', 'bert2rank', 'bert2joint']
    --pretrain_model_type   choices=['bert-base-cased', 'spanbert-base-cased', 'roberta-base']
    --eval_checkpoint       The checkpoint file to be evaluated
    

5/ Re-produce evaluation results using our checkpoints

  • Run test.sh, and change the eval_checkpoint to the checkpoint files we provided to reproduce the following results.

    --dataset_class         openkp
    --eval_checkpoint       The filepath of our provided checkpoint
    

* RESULTS

The following results are ranked by F1@3 on OpenKP Dev dataset, the eval results can be seen in the OpenKP Leaderboard.

* BERT (Base)

Rank Method F1 @1,@3,@5 Precision @1,@3,@5 Recall @1,@3,@5
1 Bert2Joint 0.371, 0.384, 0.326 0.504, 0.313, 0.227 0.315, 0.555, 0.657
2 Bert2Rank 0.369, 0.381, 0.325 0.502, 0.311, 0.227 0.315, 0.551, 0.655
3 Bert2Tag 0.370, 0.374, 0.318 0.502, 0.305, 0.222 0.315, 0.541, 0.642
4 Bert2Chunk 0.370, 0.370, 0.311 0.504, 0.302, 0.217 0.314, 0.533, 0.627
5 Bert2Span 0.341, 0.340, 0.293 0.466, 0.277, 0.203 0.289, 0.492, 0.593

* SpanBERT (Base)

Rank Method F1 @1,@3,@5 Precision @1,@3,@5 Recall @1,@3,@5
1 Bert2Joint 0.388, 0.393, 0.333 0.527, 0.321, 0.232 0.331, 0.567, 0.671
2 Bert2Rank 0.385, 0.390, 0.332 0.521, 0.319, 0.232 0.328, 0.564, 0.666
3 Bert2Tag 0.384, 0.385, 0.327 0.520, 0.315, 0.228 0.327, 0.555, 0.657
4 Bert2Chunk 0.378, 0.385, 0.326 0.514, 0.314, 0.228 0.322, 0.555, 0.656
5 Bert2Span 0.347, 0.359, 0.304 0.477, 0.294, 0.212 0.293, 0.518, 0.613

* RoBERTa (Base)

Rank Method F1 @1,@3,@5 Precision @1,@3,@5 Recall @1,@3,@5
1 Bert2Joint 0.391, 0.398, 0.338 0.532, 0.325, 0.235 0.334, 0.577, 0.681
2 Bert2Rank 0.388, 0.395, 0.335 0.526, 0.322, 0.233 0.330, 0.570, 0.677
3 Bert2Tag 0.387, 0.389, 0.330 0.525, 0.318, 0.230 0.329, 0.562, 0.666
4 Bert2Chunk 0.380, 0.382, 0.327 0.518, 0.312, 0.228 0.324, 0.551, 0.660
5 Bert2Span 0.358, 0.355, 0.306 0.487, 0.289, 0.213 0.304, 0.513, 0.619

MODEL OVERVIEW

* BERT-JointKPE, RankKPE, ChunkKPE (See Paper)

* BERT-TagKPE (See Code)

  • Word-Level Representations : We encode an input document into a sequence of WordPiece tokens' vectors with a pretrained BERT (or its variants), and then we pick up the first sub-token vector of each word to represent the input in word-level.

  • Phrase-Level Representations : We perform a soft-select method to decode phrase from word-level vector instead of hard-select used in the standard sequence tagging task .

    The word-level representation is feed into an classification layer to obtain the tag probabilities of each word on 5 classes (O, B, I, E, U) , and then we employ different tag patterns for extracting different n-grams ( 1 ≤ n ≤ 5 ) over the whole sequence.

    Last there are a collect of n-gram candidates, each word of the n-gram just has one score.

    Soft-select Example : considering all 3-grams (B I E) on the L-length document, we can extract (L-3+1) 3-grams sequentially like sliding window. In each 3-gram, we only keep B score for the first word, I score for the middle word, and E score for the last word, etc.

    O : Non Keyphrase ; B : Begin word of the keyprase ; I : Middle word of the keyphrase ; E : End word of keyprhase ; U : Uni-word keyphrase

  • Document-Level Keyphrase : At the Last stage, the recovering from phrase-level n-grams to document-level keyphrases can be naturally formulated as a ranking task.

    Incorporating with term frequency, we employ Min Pooling to get the final score of each n-gram (we called it Buckets Effect: No matter how high a bucket, it depends on the height of the water in which the lowest piece of wood) . Based on the final scores, we extract 5 top ranked keyprhase candidates for each document.

* BERT-SpanKPE (See Code)

  • Word-Level Representations : Same as BERT-TagKPE

  • Phrase-Level Representations : Traditional span extraction model could not extract multiple important keyphrase spans for the same document. Therefore, we propose an self-attention span extraction model.

    Given the token representations {t1, t2, ..., tn}, we first calculate the probability that the token is the starting word Ps(ti), and then apply the single-head self-attention layer to calculate the ending word probability of all j>=i tokens Pe(tj).

  • Document-Level Keyphrase : We select the spans with the highest probability P = Ps(ti) * Pe(tj) as the keyphrase spans.

CONTACT

For any question, please contact Si Sun by email s-sun17@mails.tsinghua.edu.cn , we will try our best to solve.

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