Phrase-based Machine Translation is State-of-the-Art for Automatic Grammatical Error Correction

Last update: 15/7/2017

This repository contains baseline models, training scripts, and instructions on how to reproduce our results for our state-of-art grammar correction system from M. Junczys-Dowmunt, R. Grundkiewicz: Phrase-based Machine Translation is State-of-the-Art for Automatic Grammatical Error Correction, EMNLP 2016.

Citation

@InProceedings{junczysdowmunt-grundkiewicz:2016:EMNLP2016,
  author    = {Junczys-Dowmunt, Marcin  and  Grundkiewicz, Roman},
  title     = {Phrase-based Machine Translation is State-of-the-Art for
               Automatic Grammatical Error Correction},
  booktitle = {Proceedings of the 2016 Conference on Empirical Methods in
               Natural Language Processing},
  month     = {November},
  year      = {2016},
  address   = {Austin, Texas},
  publisher = {Association for Computational Linguistics},
  pages     = {1546--1556},
  url       = {https://aclweb.org/anthology/D16-1161}
}

Results on JFLEG data sets

Outputs generated by our models for the JFLEG data sets are available in the folder jfleg. These are produced by our systems tuned on M^2. See the README in that folder for more information.

New: We also report results for the systems tuned on GLEU using JFLEG dev.

Update on phrase tables

The phrase table that we have made publicly available for download were filtered for CoNLL test sets. The evaluation of our systems with that PT on other data sets makes no sense. Now, we provide the original unfiltered phrase table in binarized format (due to its size). The outputs for CoNLL test sets produced with a binarized PT should remain unchanged.

All .ini files and instructions how to use them have been updated.

Update on CCLM+sparse models

We have updated the model which use CCLM and sparse features. That model was used to generate results reported in the paper as Best sparse + CCLM. Moses .ini files are available in the folder models.

We also provide the script models/run_gecsmt.py to run our models (see notes below).

Update for 10gec dataset

The results reported in the camera-ready version of the paper on the dataset from Bryant and Ng (2015) (Tab. 4, three last columns) are understated due to the invalid preparation of the M2 file. The correct scores are as follows:

System	Prec.	Recall	M^2
Baseline	69.22	37.00	58.95
+CCLM	76.66	36.39	62.77
Best dense	71.11	37.44	60.27
+CCLM	79.76	39.52	66.27
Best sparse	76.48	35.99	62.43
+CCLM	80.57	39.74	66.83

We would like to thank Shamil Chollampatt for reporting this issue!

Outputs

Outputs generated by our models for the CoNLL-2014 test set are available in the folder outputs. These correspond to Table 4 of our paper. See the README in that folder for more information.

Baseline models

You can download and run our baseline models (1,3G).

models/
├── data
│   ├── lm.cor.kenlm
│   ├── osm.kenlm
│   ├── phrase-table.0-0.gz
│   └── phrase-table.0-0.unfiltered.minphr
├── moses.dense-cclm.mert.avg.ini
├── moses.dense.mert.avg.ini
├── moses.sparse-cclm.mert.avg.ini
├── moses.sparse.mert.avg.ini
└── sparse
    ├── moses.cc.sparse
    └── moses.wiki.sparse

The four configuration *.ini files corresponds to the last four systems described in Table 4.

To use the models you need to install Moses decoder (branch master). It has to be compiled with support for 9-gram kenLM language models, and binarized tables by providing path to CMPH library (see details here, e.g.:

/usr/bin/bjam -j16 --max-kenlm-order=9 --with-cmph=/path/to/cmph

The language model data are available in separate packages:

• Wikipedia language model (22G)
• Common Crawl language model (26G)

The packages contain:

wikilm/
├── wiki.blm
├── wiki.classes.gz
└── wiki.wclm.kenlm
cclm/
├── cc.classes.gz
├── cc.kenlm
└── cc.wclm.kenlm

Adjust absolute paths in moses.*.ini files. You can do this by replacing /path/to/ with the path to the directory where you downloaded models and language models. Finally, run moses, e.g.:

/path/to/mosesdecoder/bin/moses -f moses.dense.mert.avg.ini < input.txt

The input file should contain one sentence per line and each sentence has to follow the Moses tokenization and truecasing as it is presented in train/run_cross.perl.

Alternatively you can use the script models/run_gecsmt.py, which performs pre- and postprocessing, e.g.:

python ./run/run_gecsmt.py -f moses.ini -w workdir -i input.txt -o output.txt

It can be used to evaluate M2 input:

python ./run/run_gecsmt.py -f moses.ini -w workdir -i test2014.m2 --m2

You will need to provide paths to Moses, Lazy and this repository. Use --help option for more details.

Running our models might give slightly different results (up to +/- 0.0020 F-score) than the results presented in the paper due to the different versions of the official CoNLL-2014 test set (we used the version provided during the CoNLL shared task), M2Scorer, NLTK tokenizer, Moses, and the LM used for truecasing.

Training models

Training is described in the README in the folder train.

Acknowledgments

This project was partially funded by the Polish National Science Centre (Grant No. 2014/15/N/ST6/02330).