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Finalize lm examples (#8188)

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* Finish the cleanup of the language-modeling examples

* Update main README

* Apply suggestions from code review

Co-authored-by: Lysandre Debut <lysandre@huggingface.co>

* Apply suggestions from code review

Co-authored-by: Thomas Wolf <thomwolf@users.noreply.github.com>

* Propagate changes

Co-authored-by: Lysandre Debut <lysandre@huggingface.co>
Co-authored-by: Thomas Wolf <thomwolf@users.noreply.github.com>
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examples/language-modeling/README.md
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@@ -1,16 +1,19 @@
## Language model training
Based on the script [`run_language_modeling.py`](https://github.com/huggingface/transformers/blob/master/examples/language-modeling/run_language_modeling.py).
Fine-tuning (or training from scratch) the library models for language modeling on a text dataset for GPT, GPT-2,
ALBERT, BERT, DistilBERT, RoBERTa, XLNet... GPT and GPT-2 are trained or fine-tuned using a causal language modeling
(CLM) loss while ALBERT, BERT, DistilBERT and RoBERTa are trained or fine-tuned using a masked language modeling (MLM)
loss. XLNet uses permutation language modeling (PLM), you can find more information about the differences between those
objectives in our [model summary](https://huggingface.co/transformers/model_summary.html).
Fine-tuning (or training from scratch) the library models for language modeling on a text dataset for GPT, GPT-2, BERT, DistilBERT and RoBERTa. GPT and GPT-2 are fine-tuned using a causal language modeling (CLM) loss while BERT, DistilBERT and RoBERTa
are fine-tuned using a masked language modeling (MLM) loss.
These scripts leverage the 🤗 Datasets library and the Trainer API. You can easily customize them to your needs if you
need extra processing on your datasets.
Before running the following example, you should get a file that contains text on which the language model will be
trained or fine-tuned. A good example of such text is the [WikiText-2 dataset](https://blog.einstein.ai/the-wikitext-long-term-dependency-language-modeling-dataset/).
**Note:** The old script `run_language_modeling.py` is still available
[here](https://github.com/huggingface/transformers/blob/master/examples/contrib/legacy/language-modeling/run_language_modeling.py).
We will refer to two different files: `$TRAIN_FILE`, which contains text for training, and `$TEST_FILE`, which contains
text that will be used for evaluation.
The following examples, will run on a datasets hosted on our [hub](https://huggingface.co/datasets) or with your own
text files for training and validation. We give examples of both below.
### GPT-2/GPT and causal language modeling
@@ -18,66 +21,99 @@ The following example fine-tunes GPT-2 on WikiText-2. We're using the raw WikiTe
the tokenization). The loss here is that of causal language modeling.
```bash
export TRAIN_FILE=/path/to/dataset/wiki.train.raw
export TEST_FILE=/path/to/dataset/wiki.test.raw
python run_language_modeling.py \
--output_dir=output \
--model_type=gpt2 \
--model_name_or_path=gpt2 \
python run_clm.py \
--model_name_or_path gpt2 \
--dataset_name wikitext \
--dataset_config_name wikitext-2-raw-v1 \
--do_train \
--train_data_file=$TRAIN_FILE \
--do_eval \
--eval_data_file=$TEST_FILE
--output_dir /tmp/test-clm
```
This takes about half an hour to train on a single K80 GPU and about one minute for the evaluation to run. It reaches
a score of ~20 perplexity once fine-tuned on the dataset.
To run on your own training and validation files, use the following command:
```bash
python run_clm.py \
--model_name_or_path gpt2 \
--train_file path_to_train_file \
--validation_file path_to_validation_file \
--do_train \
--do_eval \
--output_dir /tmp/test-clm
```
### RoBERTa/BERT/DistilBERT and masked language modeling
The following example fine-tunes RoBERTa on WikiText-2. Here too, we're using the raw WikiText-2. The loss is different
as BERT/RoBERTa have a bidirectional mechanism; we're therefore using the same loss that was used during their
pre-training: masked language modeling.
In accordance to the RoBERTa paper, we use dynamic masking rather than static masking. The model may, therefore, converge
slightly slower (over-fitting takes more epochs).
We use the `--mlm` flag so that the script may change its loss function.
If using whole-word masking, use both the`--mlm` and `--wwm` flags.
In accordance to the RoBERTa paper, we use dynamic masking rather than static masking. The model may, therefore,
converge slightly slower (over-fitting takes more epochs).
```bash
export TRAIN_FILE=/path/to/dataset/wiki.train.raw
export TEST_FILE=/path/to/dataset/wiki.test.raw
python run_language_modeling.py \
--output_dir=output \
--model_type=roberta \
--model_name_or_path=roberta-base \
python run_mlm.py \
--model_name_or_path roberta-base \
--dataset_name wikitext \
--dataset_config_name wikitext-2-raw-v1 \
--do_train \
--train_data_file=$TRAIN_FILE \
--do_eval \
--eval_data_file=$TEST_FILE \
--mlm \
--whole_word_mask
--output_dir /tmp/test-mlm
```
For Chinese models, it's same with English model with only `--mlm`. If using whole-word masking, we need to generate a reference files, because it's char level.
To run on your own training and validation files, use the following command:
**Q :** Why ref file ?
```bash
python run_clm.py \
--model_name_or_path roberta-base \
--train_file path_to_train_file \
--validation_file path_to_validation_file \
--do_train \
--do_eval \
--output_dir /tmp/test-clm
```
**A :** Suppose we have a Chinese sentence like : `我喜欢你` The original Chinese-BERT will tokenize it as `['我','喜','欢','你']` in char level.
Actually, `喜欢` is a whole word. For whole word mask proxy, We need res like `['我','喜','##欢','你']`.
So we need a ref file to tell model which pos of BERT original token should be added `##`.
### Whole word masking
The BERT authors released a new version of BERT using Whole Word Masking in May 2019. Instead of masking randomly
selected tokens (which may be aprt of words), they mask randomly selected words (masking all the tokens corresponding
to that word). This technique has been refined for Chinese in [this paper](https://arxiv.org/abs/1906.08101).
To fine-tune a model using whole word masking, use the following script:
python run_mlm_wwm.py \
--model_name_or_path roberta-base \
--dataset_name wikitext \
--dataset_config_name wikitext-2-raw-v1 \
--do_train \
--do_eval \
--output_dir /tmp/test-mlm-wwm
```
For Chinese models, we need to generate a reference files (which requires the ltp library), because it's tokenized at
the character level.
**Q :** Why a reference file?
**A :** Suppose we have a Chinese sentence like: `我喜欢你` The original Chinese-BERT will tokenize it as
`['我','喜','欢','你']` (character level). But `喜欢` is a whole word. For whole word masking proxy, we need a result
like `['我','喜','##欢','你']`, so we need a reference file to tell the model which position of the BERT original token
should be added `##`.
**Q :** Why LTP ?
**A :** Cause the best known Chinese WWM BERT is [Chinese-BERT-wwm](https://github.com/ymcui/Chinese-BERT-wwm) by HIT. It works well on so many Chines Task like CLUE (Chinese GLUE).
They use LTP, so if we want to fine-tune their model, we need LTP.
**A :** Cause the best known Chinese WWM BERT is [Chinese-BERT-wwm](https://github.com/ymcui/Chinese-BERT-wwm) by HIT.
It works well on so many Chines Task like CLUE (Chinese GLUE). They use LTP, so if we want to fine-tune their model,
we need LTP.
Now LTP only only works well on `transformers==3.2.0`. So we don't add it to requirements.txt.
You need to check to `3.2.0` for `run_chinese_ref.py`. And the code could be found in `examples/contrib`.
You need to create a separate enviromnent with this version of Transformers to run the `run_chinese_ref.py` script that
will create the reference files. The script is in `examples/contrib`. Once in the proper enviromnent, run the
following:
```bash
@@ -87,31 +123,25 @@ export BERT_RESOURCE=/path/to/bert/tokenizer
export SAVE_PATH=/path/to/data/ref.txt
python examples/contrib/run_chinese_ref.py \
--file_name=$TRAIN_FILE \
--ltp=$LTP_RESOURCE \
--bert=$BERT_RESOURCE \
--save_path=$SAVE_PATH
--file_name=path_to_train_or_eval_file \
--ltp=path_to_ltp_tokenizer \
--bert=path_to_bert_tokenizer \
--save_path=path_to_reference_file
```
Now Chinese Ref is only supported by `LineByLineWithRefDataset` Class, so we need add `line_by_line` flag:
Then you can run the script like this:
```bash
export TRAIN_FILE=/path/to/dataset/wiki.train.raw
export TEST_FILE=/path/to/dataset/wiki.test.raw
export REF_FILE=/path/to/ref.txt
python run_language_modeling.py \
--output_dir=output \
--model_type=roberta \
--model_name_or_path=roberta-base \
python run_mlm_wwm.py \
--model_name_or_path roberta-base \
--train_file path_to_train_file \
--validation_file path_to_validation_file \
--train_ref_file path_to_train_chinese_ref_file \
--validation_ref_file path_to_validation_chinese_ref_file \
--do_train \
--train_data_file=$TRAIN_FILE \
--chinese_ref_file=$REF_FILE \
--do_eval \
--eval_data_file=$TEST_FILE \
--mlm \
--line_by_line \
--whole_word_mask
--output_dir /tmp/test-mlm-wwm
```
### XLNet and permutation language modeling
@@ -126,15 +156,26 @@ context length for permutation language modeling.
The `--max_span_length` flag may also be used to limit the length of a span of masked tokens used
for permutation language modeling.
```bash
export TRAIN_FILE=/path/to/dataset/wiki.train.raw
export TEST_FILE=/path/to/dataset/wiki.test.raw
Here is how to fine-tun XLNet on wikitext-2:
python run_language_modeling.py \
--output_dir=output \
```bash
python run_plm.py \
--model_name_or_path=xlnet-base-cased \
--dataset_name wikitext \
--dataset_config_name wikitext-2-raw-v1 \
--do_train \
--train_data_file=$TRAIN_FILE \
--do_eval \
--eval_data_file=$TEST_FILE \
--output_dir /tmp/test-plm
```
To fine-tune it on your own training and validation file, run:
```bash
python run_plm.py \
--model_name_or_path=xlnet-base-cased \
--train_file path_to_train_file \
--validation_file path_to_validation_file \
--do_train \
--do_eval \
--output_dir /tmp/test-plm
```