## Token classification

Based on the scripts [`run_ner.py`](https://github.com/huggingface/transformers/blob/master/examples/contrib/legacy/token-classification/run_ner.py).

The following examples are covered in this section:

* NER on the GermEval 2014 (German NER) dataset
* Emerging and Rare Entities task: WNUT’17 (English NER) dataset

Details and results for the fine-tuning provided by @stefan-it.

### GermEval 2014 (German NER) dataset

#### Data (Download and pre-processing steps)

Data can be obtained from the [GermEval 2014](https://sites.google.com/site/germeval2014ner/data) shared task page.

Here are the commands for downloading and pre-processing train, dev and test datasets. The original data format has four (tab-separated) columns, in a pre-processing step only the two relevant columns (token and outer span NER annotation) are extracted:

```bash
curl -L 'https://drive.google.com/uc?export=download&id=1Jjhbal535VVz2ap4v4r_rN1UEHTdLK5P' \
| grep -v "^#" | cut -f 2,3 | tr '\t' ' ' > train.txt.tmp
curl -L 'https://drive.google.com/uc?export=download&id=1ZfRcQThdtAR5PPRjIDtrVP7BtXSCUBbm' \
| grep -v "^#" | cut -f 2,3 | tr '\t' ' ' > dev.txt.tmp
curl -L 'https://drive.google.com/uc?export=download&id=1u9mb7kNJHWQCWyweMDRMuTFoOHOfeBTH' \
| grep -v "^#" | cut -f 2,3 | tr '\t' ' ' > test.txt.tmp
```

The GermEval 2014 dataset contains some strange "control character" tokens like `'\x96', '\u200e', '\x95', '\xad' or '\x80'`.
One problem with these tokens is, that `BertTokenizer` returns an empty token for them, resulting in misaligned `InputExample`s.
The `preprocess.py` script located in the `scripts` folder a) filters these tokens and b) splits longer sentences into smaller ones (once the max. subtoken length is reached).

Let's define some variables that we need for further pre-processing steps and training the model:

```bash
export MAX_LENGTH=128
export BERT_MODEL=bert-base-multilingual-cased
```

Run the pre-processing script on training, dev and test datasets:

```bash
python3 scripts/preprocess.py train.txt.tmp $BERT_MODEL $MAX_LENGTH > train.txt
python3 scripts/preprocess.py dev.txt.tmp $BERT_MODEL $MAX_LENGTH > dev.txt
python3 scripts/preprocess.py test.txt.tmp $BERT_MODEL $MAX_LENGTH > test.txt
```

The GermEval 2014 dataset has much more labels than CoNLL-2002/2003 datasets, so an own set of labels must be used:

```bash
cat train.txt dev.txt test.txt | cut -d " " -f 2 | grep -v "^$"| sort | uniq > labels.txt
```

#### Prepare the run

Additional environment variables must be set:

```bash
export OUTPUT_DIR=germeval-model
export BATCH_SIZE=32
export NUM_EPOCHS=3
export SAVE_STEPS=750
export SEED=1
```

#### Run the Pytorch version

To start training, just run:

```bash
python3 run_ner.py --data_dir ./ \
--labels ./labels.txt \
--model_name_or_path $BERT_MODEL \
--output_dir $OUTPUT_DIR \
--max_seq_length  $MAX_LENGTH \
--num_train_epochs $NUM_EPOCHS \
--per_device_train_batch_size $BATCH_SIZE \
--save_steps $SAVE_STEPS \
--seed $SEED \
--do_train \
--do_eval \
--do_predict
```

If your GPU supports half-precision training, just add the `--fp16` flag. After training, the model will be both evaluated on development and test datasets.

#### JSON-based configuration file

Instead of passing all parameters via commandline arguments, the `run_ner.py` script also supports reading parameters from a json-based configuration file:

```json
{
    "data_dir": ".",
    "labels": "./labels.txt",
    "model_name_or_path": "bert-base-multilingual-cased",
    "output_dir": "germeval-model",
    "max_seq_length": 128,
    "num_train_epochs": 3,
    "per_device_train_batch_size": 32,
    "save_steps": 750,
    "seed": 1,
    "do_train": true,
    "do_eval": true,
    "do_predict": true
}
```

It must be saved with a `.json` extension and can be used by running `python3 run_ner.py config.json`.

#### Evaluation

Evaluation on development dataset outputs the following for our example:

```bash
10/04/2019 00:42:06 - INFO - __main__ -   ***** Eval results  *****
10/04/2019 00:42:06 - INFO - __main__ -     f1 = 0.8623348017621146
10/04/2019 00:42:06 - INFO - __main__ -     loss = 0.07183869666975543
10/04/2019 00:42:06 - INFO - __main__ -     precision = 0.8467916366258111
10/04/2019 00:42:06 - INFO - __main__ -     recall = 0.8784592370979806
```

On the test dataset the following results could be achieved:

```bash
10/04/2019 00:42:42 - INFO - __main__ -   ***** Eval results  *****
10/04/2019 00:42:42 - INFO - __main__ -     f1 = 0.8614389652384803
10/04/2019 00:42:42 - INFO - __main__ -     loss = 0.07064602487454782
10/04/2019 00:42:42 - INFO - __main__ -     precision = 0.8604651162790697
10/04/2019 00:42:42 - INFO - __main__ -     recall = 0.8624150210424085
```

### Emerging and Rare Entities task: WNUT’17 (English NER) dataset

Description of the WNUT’17 task from the [shared task website](http://noisy-text.github.io/2017/index.html):

> The WNUT’17 shared task focuses on identifying unusual, previously-unseen entities in the context of emerging discussions.
> Named entities form the basis of many modern approaches to other tasks (like event clustering and summarization), but recall on
> them is a real problem in noisy text - even among annotators. This drop tends to be due to novel entities and surface forms.

Six labels are available in the dataset. An overview can be found on this [page](http://noisy-text.github.io/2017/files/).

#### Data (Download and pre-processing steps)

The dataset can be downloaded from the [official GitHub](https://github.com/leondz/emerging_entities_17) repository.

The following commands show how to prepare the dataset for fine-tuning:

```bash
mkdir -p data_wnut_17

curl -L 'https://github.com/leondz/emerging_entities_17/raw/master/wnut17train.conll'  | tr '\t' ' ' > data_wnut_17/train.txt.tmp
curl -L 'https://github.com/leondz/emerging_entities_17/raw/master/emerging.dev.conll' | tr '\t' ' ' > data_wnut_17/dev.txt.tmp
curl -L 'https://raw.githubusercontent.com/leondz/emerging_entities_17/master/emerging.test.annotated' | tr '\t' ' ' > data_wnut_17/test.txt.tmp
```

Let's define some variables that we need for further pre-processing steps:

```bash
export MAX_LENGTH=128
export BERT_MODEL=bert-large-cased
```

Here we use the English BERT large model for fine-tuning.
The `preprocess.py` scripts splits longer sentences into smaller ones (once the max. subtoken length is reached):

```bash
python3 scripts/preprocess.py data_wnut_17/train.txt.tmp $BERT_MODEL $MAX_LENGTH > data_wnut_17/train.txt
python3 scripts/preprocess.py data_wnut_17/dev.txt.tmp $BERT_MODEL $MAX_LENGTH > data_wnut_17/dev.txt
python3 scripts/preprocess.py data_wnut_17/test.txt.tmp $BERT_MODEL $MAX_LENGTH > data_wnut_17/test.txt
```

In the last pre-processing step, the `labels.txt` file needs to be generated. This file contains all available labels:

```bash
cat data_wnut_17/train.txt data_wnut_17/dev.txt data_wnut_17/test.txt | cut -d " " -f 2 | grep -v "^$"| sort | uniq > data_wnut_17/labels.txt
```

#### Run the Pytorch version

Fine-tuning with the PyTorch version can be started using the `run_ner.py` script. In this example we use a JSON-based configuration file.

This configuration file looks like:

```json
{
    "data_dir": "./data_wnut_17",
    "labels": "./data_wnut_17/labels.txt",
    "model_name_or_path": "bert-large-cased",
    "output_dir": "wnut-17-model-1",
    "max_seq_length": 128,
    "num_train_epochs": 3,
    "per_device_train_batch_size": 32,
    "save_steps": 425,
    "seed": 1,
    "do_train": true,
    "do_eval": true,
    "do_predict": true,
    "fp16": false
}
```

If your GPU supports half-precision training, please set `fp16` to `true`.

Save this JSON-based configuration under `wnut_17.json`. The fine-tuning can be started with `python3 run_ner_old.py wnut_17.json`.

#### Evaluation

Evaluation on development dataset outputs the following:

```bash
05/29/2020 23:33:44 - INFO - __main__ -   ***** Eval results *****
05/29/2020 23:33:44 - INFO - __main__ -     eval_loss = 0.26505235286212275
05/29/2020 23:33:44 - INFO - __main__ -     eval_precision = 0.7008264462809918
05/29/2020 23:33:44 - INFO - __main__ -     eval_recall = 0.507177033492823
05/29/2020 23:33:44 - INFO - __main__ -     eval_f1 = 0.5884802220680084
05/29/2020 23:33:44 - INFO - __main__ -     epoch = 3.0
```

On the test dataset the following results could be achieved:

```bash
05/29/2020 23:33:44 - INFO - transformers.trainer -   ***** Running Prediction *****
05/29/2020 23:34:02 - INFO - __main__ -     eval_loss = 0.30948806500973547
05/29/2020 23:34:02 - INFO - __main__ -     eval_precision = 0.5840108401084011
05/29/2020 23:34:02 - INFO - __main__ -     eval_recall = 0.3994439295644115
05/29/2020 23:34:02 - INFO - __main__ -     eval_f1 = 0.47440836543753434
```

WNUT’17 is a very difficult task. Current state-of-the-art results on this dataset can be found [here](http://nlpprogress.com/english/named_entity_recognition.html).