Merge branch 'master' into pr/1383

.github/ISSUE_TEMPLATE/--new-model-addition.md

+---
+name: "\U0001F31FNew model addition"
+about: Submit a proposal/request to implement a new Transformer-based model
+title: ''
+labels: ''
+assignees: ''
+
+---
+
+# 🌟New model addition
+
+## Model description
+
+<!-- Important information -->
+
+## Open Source status
+
+* [ ] the model implementation is available: (give details)
+* [ ] the model weights are available: (give details)
+
+## Additional context
+
+<!-- Add any other context about the problem here. -->

.github/ISSUE_TEMPLATE/bug-report.md

 ---
 name: "\U0001F41B Bug Report"
 about: Submit a bug report to help us improve PyTorch Transformers
+title: ''
+labels: ''
+assignees: ''
+
 ---
 
 ## 🐛 Bug
@@ -45,4 +49,4 @@ Steps to reproduce the behavior:
 
 ## Additional context
 
-<!-- Add any other context about the problem here. -->
\ No newline at end of file
+<!-- Add any other context about the problem here. -->

.github/ISSUE_TEMPLATE/feature-request.md

 ---
 name: "\U0001F680 Feature Request"
 about: Submit a proposal/request for a new PyTorch Transformers feature
+title: ''
+labels: ''
+assignees: ''
+
 ---
 
 ## 🚀 Feature
@@ -13,4 +17,4 @@ about: Submit a proposal/request for a new PyTorch Transformers feature
 
 ## Additional context
 
-<!-- Add any other context or screenshots about the feature request here. -->
\ No newline at end of file
+<!-- Add any other context or screenshots about the feature request here. -->

.github/ISSUE_TEMPLATE/migration.md

 ---
 name: "\U0001F4DA Migration from PyTorch-pretrained-Bert"
 about: Report a problem when migrating from PyTorch-pretrained-Bert to Transformers
+title: ''
+labels: ''
+assignees: ''
+
 ---
 
 ## 📚 Migration
@@ -40,4 +44,4 @@ Details of the issue:
 
 ## Additional context
 
-<!-- Add any other context about the problem here. -->
\ No newline at end of file
+<!-- Add any other context about the problem here. -->

.github/ISSUE_TEMPLATE/question-help.md

 ---
 name: "❓Questions & Help"
 about: Start a general discussion related to PyTorch Transformers
+title: ''
+labels: ''
+assignees: ''
+
 ---
 
 ## ❓ Questions & Help
 
-<!-- A clear and concise description of the question. -->
\ No newline at end of file
+<!-- A clear and concise description of the question. -->

CONTRIBUTING.md

+# How to contribute to transformers?
+
+Everyone is welcome to contribute, and we value everybody's contribution. Code
+is thus not the only way to help the community. Answering questions, helping
+others, reaching out and improving the documentations are immensely valuable to
+the community.
+
+It also helps us if you spread the word: reference the library from blog posts
+on the awesome projects it made possible, shout out on Twitter every time it has
+helped you, or simply star the repo to say "thank you".
+
+## You can contribute in so many ways!
+
+There are 4 ways you can contribute to transformers:
+* Fixing outstanding issues with the existing code;
+* Implementing new models;
+* Contributing to the examples or to the documentation;
+* Submitting issues related to bugs or desired new features.
+
+*All are equally valuable to the community.*
+
+## Submitting a new issue or feature request
+
+Do your best to follow these guidelines when submitting an issue or a feature
+request. It will make it easier for us to come back to you quickly and with good
+feedback.
+
+### Did you find a bug?
+
+The transformers are robust and reliable thanks to the users who notify us of
+the problems they encounter. So thank you for reporting an issue.
+
+First, we would really appreciate it if you could **make sure the bug was not
+already reported** (use the search bar on Github under Issues).
+
+Did not find it? :( So we can act quickly on it, please follow these steps:
+
+* Include your **OS type and version**, the versions of **Python**, **PyTorch** and
+  **Tensorflow** when applicable;
+* A short, self-contained, code snippet that allows us to reproduce the bug in
+  less than 30s;
+* Provide the *full* traceback if an exception is raised.
+
+To get the OS and software versions, execute the following code and copy-paste
+the output:
+
+```
+import platform; print("Platform", platform.platform())
+import sys; print("Python", sys.version)
+import torch; print("PyTorch", torch.__version__)
+import tensorflow; print("Tensorflow", tensorflow.__version__)
+```
+
+### Do you want to implement a new model?
+
+Awesome! Please provide the following information:
+
+* Short description of the model and link to the paper;
+* Link to the implementation if it is open-source;
+* Link to the model weights if they are available.
+
+If you are willing to contribute the model yourself, let us know so we can best
+guide you.
+
+### Do you want a new feature (that is not a model)?
+
+A world-class feature request addresses the following points:
+
+1. Motivation first:
+  * Is it related to a problem/frustration with the library? If so, please explain
+    why. Providing a code snippet that demonstrates the problem is best.
+  * Is it related to something you would need for a project? We'd love to hear
+    about it!
+  * Is it something you worked on and think could benefit the community?
+    Awesome! Tell us what problem it solved for you.
+2. Write a *full paragraph* describing the feature;
+3. Provide a **code snippet** that demonstrates its future use;
+4. In case this is related to a paper, please attach a link;
+5. Attach any additional information (drawings, screenshots, etc.) you think may help.
+
+If your issue is well written we're already 80% of the way there by the time you
+post it.
+
+## Start contributing! (Pull Requests)
+
+Before writing code, we strongly advise you to search through the exising PRs or
+issues to make sure that nobody is already working on the same thing. If you are
+unsure, it is always a good idea to open an issue to get some feedback.
+
+You will need basic `git` proficiency to be able to contribute to
+`transformers`. `git` is not the easiest tool to use but it has the greatest
+manual. Type `git --help` in a shell and enjoy. If you prefer books, [Pro
+Git](https://git-scm.com/book/en/v2) is a very good reference.
+
+Follow these steps to start contributing:
+
+1. Fork the [repository](https://github.com/huggingface/transformers) by
+   clicking on the 'Fork' button on the repository's page. This creates a copy of the code
+   under your github user account.
+2. Clone your fork to your local disk, and add the base repository as a remote:
+   
+   ```bash
+   $ git clone git@github.com:<your Github handle>/transformers.git
+   $ cd transformers
+   $ git remote add upstream git@github.com:huggingface/transformers.git
+   ```
+
+3. Create a new branch to hold your development changes:
+
+   ```bash
+   $ git checkout -b a-descriptive-name-for-my-changes
+   ```
+   
+   **do not** work on the `master` branch.
+   
+4. Set up a development environment by running the following command in a virtual environment:
+
+   ```bash
+   $ pip install -r requirements-dev.txt
+   ```
+
+5. Develop the features on your branch. Add changed files using `git add` and
+   then `git commit` to record your changes locally:
+   
+   ```bash
+   $ git add modified_file.py
+   $ git commit
+   ```
+   
+   Please write [good commit
+   messages](https://chris.beams.io/posts/git-commit/). It
+   is a good idea to sync your copy of the code with the original repository
+   regularly. This way you can quickly account for changes:
+   
+   ```bash
+   $ git fetch upstream
+   $ git rebase upstream/master
+   ```
+   
+   Push the changes to your account using:
+   
+   ```bash
+   $ git push -u origin a-descriptive-name-for-my-changes
+   ```
+   
+6. Once you are satisfied (**and the checklist below is happy too**), go to the
+   webpage of your fork on Github. Click on 'Pull request' to send your changes
+   to the project maintainers for review.
+   
+7. It's ok if maintainers ask you for changes. It happens to core contributors
+   too! So everyone can see the changes in the Pull request, work in your local
+   branch and push the changes to your fork. They will automatically appear in
+   the pull request.
+
+
+### Checklist
+
+1. The title of your pull request should be a summary of its contribution;
+2. If your pull request adresses an issue, please mention the issue number in
+   the pull request description to make sure they are linked (and people
+   consulting the issue know you are working on it);
+3. To indicate a work in progress please prefix the title with `[WIP]`. These
+   are useful to avoid duplicated work, and to differentiate it from PRs ready
+   to be merged;
+4. Make sure pre-existing tests still pass;
+5. Add high-coverage tests. No quality test, no merge;
+6. All public methods must have informative doctrings;
+
+
+### Style guide
+
+For documentation strings, `transformers` follows the [google
+style](https://google.github.io/styleguide/pyguide.html).
+
+#### This guide was heavily inspired by the awesome [scikit-learn guide to contributing](https://github.com/scikit-learn/scikit-learn/blob/master/CONTRIBUTING.md)

README.md

@@ -56,7 +56,7 @@ Choose the right framework for every part of a model's lifetime
 | [Quick tour: Usage](#quick-tour) | Tokenizers & models usage: Bert and GPT-2 |
 | [Quick tour: TF 2.0 and PyTorch ](#Quick-tour-TF-20-training-and-PyTorch-interoperability) | Train a TF 2.0 model in 10 lines of code, load it in PyTorch |
 | [Quick tour: Fine-tuning/usage scripts](#quick-tour-of-the-fine-tuningusage-scripts) | Using provided scripts: GLUE, SQuAD and Text generation |
-| [Migrating from pytorch-transformers to transformers](#Migrating-from-pytorch-transformers-to-transformers) | Migrating your code from pytorch-pretrained-bert to transformers |
+| [Migrating from pytorch-transformers to transformers](#Migrating-from-pytorch-transformers-to-transformers) | Migrating your code from pytorch-transformers to transformers |
 | [Migrating from pytorch-pretrained-bert to pytorch-transformers](#Migrating-from-pytorch-pretrained-bert-to-transformers) | Migrating your code from pytorch-pretrained-bert to transformers |
 | [Documentation](https://huggingface.co/transformers/) | Full API documentation and more |
 
@@ -67,7 +67,7 @@ This repo is tested on Python 2.7 and 3.5+ (examples are tested only on python 3
 ### With pip
 
 First you need to install one of, or both, TensorFlow 2.0 and PyTorch.
-Please refere to [TensorFlow installation page](https://www.tensorflow.org/install/pip#tensorflow-2.0-rc-is-available) and/or [PyTorch installation page](https://pytorch.org/get-started/locally/#start-locally) regarding the specific install command for your platform.
+Please refer to [TensorFlow installation page](https://www.tensorflow.org/install/pip#tensorflow-2.0-rc-is-available) and/or [PyTorch installation page](https://pytorch.org/get-started/locally/#start-locally) regarding the specific install command for your platform.
 
 When TensorFlow 2.0 and/or PyTorch has been installed, 🤗 Transformers can be installed using pip as follows:
 
@@ -78,9 +78,9 @@ pip install transformers
 ### From source
 
 Here also, you first need to install one of, or both, TensorFlow 2.0 and PyTorch.
-Please refere to [TensorFlow installation page](https://www.tensorflow.org/install/pip#tensorflow-2.0-rc-is-available) and/or [PyTorch installation page](https://pytorch.org/get-started/locally/#start-locally) regarding the specific install command for your platform.
+Please refer to [TensorFlow installation page](https://www.tensorflow.org/install/pip#tensorflow-2.0-rc-is-available) and/or [PyTorch installation page](https://pytorch.org/get-started/locally/#start-locally) regarding the specific install command for your platform.
 
-When TensorFlow 2.0 and/or PyTorch has been installed, you can install from source by cloning the repository and runing:
+When TensorFlow 2.0 and/or PyTorch has been installed, you can install from source by cloning the repository and running:
 
 ```bash
 pip install [--editable] .
@@ -88,7 +88,7 @@ pip install [--editable] .
 
 ### Tests
 
-A series of tests is included for the library and the example scripts. Library tests can be found in the [tests folder](https://github.com/huggingface/transformers/tree/master/transformers/tests) and examples tests in the [examples folder](https://github.com/huggingface/transformers/tree/master/examples).
+A series of tests are included for the library and the example scripts. Library tests can be found in the [tests folder](https://github.com/huggingface/transformers/tree/master/transformers/tests) and examples tests in the [examples folder](https://github.com/huggingface/transformers/tree/master/examples).
 
 These tests can be run using `pytest` (install pytest if needed with `pip install pytest`).
 
@@ -105,7 +105,7 @@ python -m pytest -sv ./examples/
 
 You should check out our [`swift-coreml-transformers`](https://github.com/huggingface/swift-coreml-transformers) repo.
 
-It contains an example of a conversion script from a Pytorch trained Transformer model (here, `GPT-2`) to a CoreML model that runs on iOS devices.
+It contains a set of tools to convert PyTorch or TensorFlow 2.0 trained Transformer models (currently contains `GPT-2`, `DistilGPT-2`, `BERT`, and `DistilBERT`) to CoreML models that run on iOS devices.
 
 At some point in the future, you'll be able to seamlessly move from pre-training or fine-tuning models to productizing them in CoreML, or prototype a model or an app in CoreML then research its hyperparameters or architecture from TensorFlow 2.0 and/or PyTorch. Super exciting!
 
@@ -120,8 +120,7 @@ At some point in the future, you'll be able to seamlessly move from pre-training
 5. **[XLNet](https://github.com/zihangdai/xlnet/)** (from Google/CMU) released with the paper [​XLNet: Generalized Autoregressive Pretraining for Language Understanding](https://arxiv.org/abs/1906.08237) by Zhilin Yang*, Zihang Dai*, Yiming Yang, Jaime Carbonell, Ruslan Salakhutdinov, Quoc V. Le.
 6. **[XLM](https://github.com/facebookresearch/XLM/)** (from Facebook) released together with the paper [Cross-lingual Language Model Pretraining](https://arxiv.org/abs/1901.07291) by Guillaume Lample and Alexis Conneau.
 7. **[RoBERTa](https://github.com/pytorch/fairseq/tree/master/examples/roberta)** (from Facebook), released together with the paper a [Robustly Optimized BERT Pretraining Approach](https://arxiv.org/abs/1907.11692) by Yinhan Liu, Myle Ott, Naman Goyal, Jingfei Du, Mandar Joshi, Danqi Chen, Omer Levy, Mike Lewis, Luke Zettlemoyer, Veselin Stoyanov.
-8. **[DistilBERT](https://github.com/huggingface/transformers/tree/master/examples/distillation)** (from HuggingFace), released together with the blogpost [Smaller, faster, cheaper, lighter: Introducing DistilBERT, a distilled version of BERT](https://medium.com/huggingface/distilbert-8cf3380435b5
-) by Victor Sanh, Lysandre Debut and Thomas Wolf.
+8. **[DistilBERT](https://github.com/huggingface/transformers/tree/master/examples/distillation)** (from HuggingFace), released together with the paper [DistilBERT, a distilled version of BERT: smaller, faster, cheaper and lighter](https://arxiv.org/abs/1910.01108) by Victor Sanh, Lysandre Debut and Thomas Wolf. The same method has been applied to compress GPT2 into [DistilGPT2](https://github.com/huggingface/transformers/tree/master/examples/distillation).
 9. **[CTRL](https://github.com/salesforce/ctrl/)** (from Salesforce) released with the paper [CTRL: A Conditional Transformer Language Model for Controllable Generation](https://arxiv.org/abs/1909.05858) by Nitish Shirish Keskar*, Bryan McCann*, Lav R. Varshney, Caiming Xiong and Richard Socher.
 
 These implementations have been tested on several datasets (see the example scripts) and should match the performances of the original implementations (e.g. ~93 F1 on SQuAD for BERT Whole-Word-Masking, ~88 F1 on RocStories for OpenAI GPT, ~18.3 perplexity on WikiText 103 for Transformer-XL, ~0.916 Peason R coefficient on STS-B for XLNet). You can find more details on the performances in the Examples section of the [documentation](https://huggingface.co/transformers/examples.html).
@@ -182,24 +181,24 @@ for model_class in BERT_MODEL_CLASSES:
     # Load pretrained model/tokenizer
     model = model_class.from_pretrained('bert-base-uncased')
 
-# Models can return full list of hidden-states & attentions weights at each layer
-model = model_class.from_pretrained(pretrained_weights,
-                                    output_hidden_states=True,
-                                    output_attentions=True)
-input_ids = torch.tensor([tokenizer.encode("Let's see all hidden-states and attentions on this text")])
-all_hidden_states, all_attentions = model(input_ids)[-2:]
+    # Models can return full list of hidden-states & attentions weights at each layer
+    model = model_class.from_pretrained(pretrained_weights,
+                                        output_hidden_states=True,
+                                        output_attentions=True)
+    input_ids = torch.tensor([tokenizer.encode("Let's see all hidden-states and attentions on this text")])
+    all_hidden_states, all_attentions = model(input_ids)[-2:]
 
-# Models are compatible with Torchscript
-model = model_class.from_pretrained(pretrained_weights, torchscript=True)
-traced_model = torch.jit.trace(model, (input_ids,))
+    # Models are compatible with Torchscript
+    model = model_class.from_pretrained(pretrained_weights, torchscript=True)
+    traced_model = torch.jit.trace(model, (input_ids,))
 
-# Simple serialization for models and tokenizers
-model.save_pretrained('./directory/to/save/')  # save
-model = model_class.from_pretrained('./directory/to/save/')  # re-load
-tokenizer.save_pretrained('./directory/to/save/')  # save
-tokenizer = tokenizer_class.from_pretrained('./directory/to/save/')  # re-load
+    # Simple serialization for models and tokenizers
+    model.save_pretrained('./directory/to/save/')  # save
+    model = model_class.from_pretrained('./directory/to/save/')  # re-load
+    tokenizer.save_pretrained('./directory/to/save/')  # save
+    tokenizer = BertTokenizer.from_pretrained('./directory/to/save/')  # re-load
 
-# SOTA examples for GLUE, SQUAD, text generation...
+    # SOTA examples for GLUE, SQUAD, text generation...
 ```
 
 ## Quick tour TF 2.0 training and PyTorch interoperability
@@ -396,7 +395,7 @@ This is the model provided as `bert-large-uncased-whole-word-masking-finetuned-s
 ### `run_generation.py`: Text generation with GPT, GPT-2, CTRL, Transformer-XL and XLNet
 
 A conditional generation script is also included to generate text from a prompt.
-The generation script includes the [tricks](https://github.com/rusiaaman/XLNet-gen#methodology) proposed by Aman Rusia to get high quality generation with memory models like Transformer-XL and XLNet (include a predefined text to make short inputs longer).
+The generation script includes the [tricks](https://github.com/rusiaaman/XLNet-gen#methodology) proposed by Aman Rusia to get high-quality generation with memory models like Transformer-XL and XLNet (include a predefined text to make short inputs longer).
 
 Here is how to run the script with the small version of OpenAI GPT-2 model:
 
@@ -436,9 +435,9 @@ Here is a quick summary of what you should take care of when migrating from `pyt
 
 ### Models always output `tuples`
 
-The main breaking change when migrating from `pytorch-pretrained-bert` to `transformers` is that the models forward method always outputs a `tuple` with various elements depending on the model and the configuration parameters.
+The main breaking change when migrating from `pytorch-pretrained-bert` to `transformers` is that every model's forward method always outputs a `tuple` with various elements depending on the model and the configuration parameters.
 
-The exact content of the tuples for each model are detailed in the models' docstrings and the [documentation](https://huggingface.co/transformers/).
+The exact content of the tuples for each model is detailed in the models' docstrings and the [documentation](https://huggingface.co/transformers/).
 
 In pretty much every case, you will be fine by taking the first element of the output as the output you previously used in `pytorch-pretrained-bert`.
 
@@ -470,11 +469,11 @@ By enabling the configuration option `output_hidden_states`, it was possible to
 
 ### Serialization
 
-Breaking change in the `from_pretrained()`method:
+Breaking change in the `from_pretrained()` method:
 
-1. Models are now set in evaluation mode by default when instantiated with the `from_pretrained()` method. To train them don't forget to set them back in training mode (`model.train()`) to activate the dropout modules.
+1. Models are now set in evaluation mode by default when instantiated with the `from_pretrained()` method. To train them, don't forget to set them back in training mode (`model.train()`) to activate the dropout modules.
 
-2. The additional `*input` and `**kwargs` arguments supplied to the `from_pretrained()` method used to be directly passed to the underlying model's class `__init__()` method. They are now used to update the model configuration attribute instead which can break derived model classes build based on the previous `BertForSequenceClassification` examples. We are working on a way to mitigate this breaking change in [#866](https://github.com/huggingface/transformers/pull/866) by forwarding the the model `__init__()` method (i) the provided positional arguments and (ii) the keyword arguments which do not match any configuration class attributes.
+2. The additional `*input` and `**kwargs` arguments supplied to the `from_pretrained()` method used to be directly passed to the underlying model's class `__init__()` method. They are now used to update the model configuration attribute instead, which can break derived model classes built based on the previous `BertForSequenceClassification` examples. We are working on a way to mitigate this breaking change in [#866](https://github.com/huggingface/transformers/pull/866) by forwarding the the model's `__init__()` method (i) the provided positional arguments and (ii) the keyword arguments which do not match any configuration class attributes.
 
 Also, while not a breaking change, the serialization methods have been standardized and you probably should switch to the new method `save_pretrained(save_directory)` if you were using any other serialization method before.
 
@@ -546,4 +545,4 @@ for batch in train_data:
 
 ## Citation
 
-At the moment, there is no paper associated to Transformers but we are working on preparing one. In the meantime, please include a mention of the library and a link to the present repository if you use this work in a published or open-source project.
+At the moment, there is no paper associated with Transformers but we are working on preparing one. In the meantime, please include a mention of the library and a link to the present repository if you use this work in a published or open-source project.

docs/README.md

@@ -50,7 +50,7 @@ make html
 ---
 **NOTE**
 
-If you are adding/removing elements from the toc-tree or from any strutural item, it is recommended to clean the build
+If you are adding/removing elements from the toc-tree or from any structural item, it is recommended to clean the build
 directory before rebuilding. Run the following command to clean and build:
 
 ```bash

docs/source/_static/css/huggingface.css

-huggingface.css
-
 /* The literal code blocks */
 .rst-content tt.literal, .rst-content tt.literal, .rst-content code.literal {
     color: #6670FF;
@@ -44,11 +42,11 @@ huggingface.css
 /* The text items on the toc tree */
 .wy-menu-vertical a {
     color: #FFFFDD;
-    font-family: Calibre-Light;
+    font-family: Calibre-Light, sans-serif;
 }
 .wy-menu-vertical header, .wy-menu-vertical p.caption{
     color: white;
-    font-family: Calibre-Light;
+    font-family: Calibre-Light, sans-serif;
 }
 
 /* The color inside the selected toc tree block */
@@ -85,7 +83,7 @@ a {
     border-right: solid 2px #FB8D68;
     border-left: solid 2px #FB8D68;
     color: #FB8D68;
-    font-family: Calibre-Light;
+    font-family: Calibre-Light, sans-serif;
     border-top: none;
     font-style: normal !important;
 }
@@ -136,14 +134,14 @@ a {
 
 /* class and method names in doc */
 .rst-content dl:not(.docutils) tt.descname, .rst-content dl:not(.docutils) tt.descclassname, .rst-content dl:not(.docutils) tt.descname, .rst-content dl:not(.docutils) code.descname, .rst-content dl:not(.docutils) tt.descclassname, .rst-content dl:not(.docutils) code.descclassname{
-    font-family: Calibre;
+    font-family: Calibre, sans-serif;
     font-size: 20px !important;
 }
 
 /* class name in doc*/
 .rst-content dl:not(.docutils) tt.descname, .rst-content dl:not(.docutils) tt.descname, .rst-content dl:not(.docutils) code.descname{
     margin-right: 10px;
-    font-family: Calibre-Medium;
+    font-family: Calibre-Medium, sans-serif;
 }
 
 /* Method and class parameters */
@@ -160,17 +158,17 @@ a {
 
 /* FONTS */
 body{
-    font-family: Calibre;
+    font-family: Calibre, sans-serif;
     font-size: 16px;
 }
 
 h1 {
-    font-family: Calibre-Thin;
+    font-family: Calibre-Thin, sans-serif;
     font-size: 70px;
 }
 
 h2, .rst-content .toctree-wrapper p.caption, h3, h4, h5, h6, legend{
-    font-family: Calibre-Medium;
+    font-family: Calibre-Medium, sans-serif;
 }
 
 @font-face {
@@ -196,4 +194,3 @@ h2, .rst-content .toctree-wrapper p.caption, h3, h4, h5, h6, legend{
     src: url(./Calibre-Thin.otf);
     font-weight:400;
 }
-

docs/source/index.rst

@@ -46,8 +46,7 @@ The library currently contains PyTorch and Tensorflow implementations, pre-train
 5. `XLNet <https://github.com/zihangdai/xlnet>`_ (from Google/CMU) released with the paper `​XLNet: Generalized Autoregressive Pretraining for Language Understanding <https://arxiv.org/abs/1906.08237>`_ by Zhilin Yang*, Zihang Dai*, Yiming Yang, Jaime Carbonell, Ruslan Salakhutdinov, Quoc V. Le.
 6. `XLM <https://github.com/facebookresearch/XLM>`_ (from Facebook) released together with the paper `Cross-lingual Language Model Pretraining <https://arxiv.org/abs/1901.07291>`_ by Guillaume Lample and Alexis Conneau.
 7. `RoBERTa <https://github.com/pytorch/fairseq/tree/master/examples/roberta>`_ (from Facebook), released together with the paper a `Robustly Optimized BERT Pretraining Approach <https://arxiv.org/abs/1907.11692>`_ by Yinhan Liu, Myle Ott, Naman Goyal, Jingfei Du, Mandar Joshi, Danqi Chen, Omer Levy, Mike Lewis, Luke Zettlemoyer, Veselin Stoyanov.
-8. `DistilBERT <https://huggingface.co/transformers/model_doc/distilbert.html>`_ (from HuggingFace) released together with the blog post `Smaller, faster, cheaper, lighter: Introducing DistilBERT, a distilled version of BERT <https://medium.com/huggingface/distilbert-8cf3380435b5>`_ by Victor Sanh, Lysandre Debut and Thomas Wolf.
-
+8. `DistilBERT <https://huggingface.co/transformers/model_doc/distilbert.html>`_ (from HuggingFace) released together with the paper `DistilBERT, a distilled version of BERT: smaller, faster, cheaper and lighter <https://arxiv.org/abs/1910.01108>`_ by Victor Sanh, Lysandre Debut and Thomas Wolf. The same method has been applied to compress GPT2 into `DistilGPT2 <https://github.com/huggingface/transformers/tree/master/examples/distillation>`_.
 
 .. toctree::
     :maxdepth: 2
@@ -63,6 +62,7 @@ The library currently contains PyTorch and Tensorflow implementations, pre-train
     migration
     bertology
     torchscript
+    multilingual
 
 .. toctree::
     :maxdepth: 2

docs/source/installation.rst → docs/source/installation.md

-Installation
-================================================
+# Installation
 
 Transformers is tested on Python 2.7 and 3.5+ (examples are tested only on python 3.5+) and PyTorch 1.1.0
 
-With pip
-^^^^^^^^
+## With pip
 
 PyTorch Transformers can be installed using pip as follows:
 
-.. code-block:: bash
+``` bash
+pip install transformers
+```
 
-   pip install transformers
-
-From source
-^^^^^^^^^^^
+## From source
 
 To install from source, clone the repository and install with:
 
-.. code-block:: bash
-
-    git clone https://github.com/huggingface/transformers.git
-    cd transformers
-    pip install [--editable] .
-
+``` bash
+git clone https://github.com/huggingface/transformers.git
+cd transformers
+pip install [--editable] .
+```
 
-Tests
-^^^^^
+## Tests
 
-An extensive test suite is included to test the library behavior and several examples. Library tests can be found in the `tests folder <https://github.com/huggingface/transformers/tree/master/transformers/tests>`_ and examples tests in the `examples folder <https://github.com/huggingface/transformers/tree/master/examples>`_.
+An extensive test suite is included to test the library behavior and several examples. Library tests can be found in the [tests folder](https://github.com/huggingface/transformers/tree/master/transformers/tests) and examples tests in the [examples folder](https://github.com/huggingface/transformers/tree/master/examples).
 
 Tests can be run using `pytest` (install pytest if needed with `pip install pytest`).
 
 Run all the tests from the root of the cloned repository with the commands:
 
-.. code-block:: bash
-
-    python -m pytest -sv ./transformers/tests/
-    python -m pytest -sv ./examples/
-
+``` bash
+python -m pytest -sv ./transformers/tests/
+python -m pytest -sv ./examples/
+```
 
-OpenAI GPT original tokenization workflow
-^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+## OpenAI GPT original tokenization workflow
 
-If you want to reproduce the original tokenization process of the ``OpenAI GPT`` paper, you will need to install ``ftfy`` (use version 4.4.3 if you are using Python 2) and ``SpaCy`` :
+If you want to reproduce the original tokenization process of the `OpenAI GPT` paper, you will need to install `ftfy` (use version 4.4.3 if you are using Python 2) and `SpaCy`:
 
-.. code-block:: bash
+``` bash
+pip install spacy ftfy==4.4.3
+python -m spacy download en
+```
 
-   pip install spacy ftfy==4.4.3
-   python -m spacy download en
+If you don't install `ftfy` and `SpaCy`, the `OpenAI GPT` tokenizer will default to tokenize using BERT's `BasicTokenizer` followed by Byte-Pair Encoding (which should be fine for most usage, don't worry).
 
-If you don't install ``ftfy`` and ``SpaCy``\ , the ``OpenAI GPT`` tokenizer will default to tokenize using BERT's ``BasicTokenizer`` followed by Byte-Pair Encoding (which should be fine for most usage, don't worry).
-
-
-Note on model downloads (Continuous Integration or large-scale deployments)
-^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+## Note on model downloads (Continuous Integration or large-scale deployments)
 
 If you expect to be downloading large volumes of models (more than 1,000) from our hosted bucket (for instance through your CI setup, or a large-scale production deployment), please cache the model files on your end. It will be way faster, and cheaper. Feel free to contact us privately if you need any help.
 
+## Do you want to run a Transformer model on a mobile device?
 
-Do you want to run a Transformer model on a mobile device?
-^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
-
-You should check out our `swift-coreml-transformers <https://github.com/huggingface/swift-coreml-transformers>`_ repo.
-
-It contains an example of a conversion script from a Pytorch trained Transformer model (here, ``GPT-2``) to a CoreML model that runs on iOS devices.
+You should check out our [swift-coreml-transformers](https://github.com/huggingface/swift-coreml-transformers) repo.
 
-It also contains an implementation of BERT for Question answering.
+It contains a set of tools to convert PyTorch or TensorFlow 2.0 trained Transformer models (currently contains `GPT-2`, `DistilGPT-2`, `BERT`, and `DistilBERT`) to CoreML models that run on iOS devices.
 
 At some point in the future, you'll be able to seamlessly move from pre-training or fine-tuning models in PyTorch to productizing them in CoreML,
-or prototype a model or an app in CoreML then research its hyperparameters or architecture from PyTorch. Super exciting!
\ No newline at end of file
+or prototype a model or an app in CoreML then research its hyperparameters or architecture from PyTorch. Super exciting!

docs/source/multilingual.rst

+Multi-lingual models
+================================================
+
+Most of the models available in this library are mono-lingual models (English, Chinese and German). A few
+multi-lingual models are available and have a different mechanisms than mono-lingual models.
+This page details the usage of these models.
+
+The two models that currently support multiple languages are BERT and XLM.
+
+XLM
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+XLM has a total of 10 different checkpoints, only one of which is mono-lingual. The 9 remaining model checkpoints can
+be split in two categories: the checkpoints that make use of language embeddings, and those that don't
+
+XLM & Language Embeddings
+------------------------------------------------
+
+This section concerns the following checkpoints:
+
+- ``xlm-mlm-ende-1024`` (Masked language modeling, English-German)
+- ``xlm-mlm-enfr-1024`` (Masked language modeling, English-French)
+- ``xlm-mlm-enro-1024`` (Masked language modeling, English-Romanian)
+- ``xlm-mlm-xnli15-1024`` (Masked language modeling, XNLI languages)
+- ``xlm-mlm-tlm-xnli15-1024`` (Masked language modeling + Translation, XNLI languages)
+- ``xlm-clm-enfr-1024`` (Causal language modeling, English-French)
+- ``xlm-clm-ende-1024`` (Causal language modeling, English-German)
+
+These checkpoints require language embeddings that will specify the language used at inference time. These language
+embeddings are represented as a tensor that is of the same shape as the input ids passed to the model. The values in
+these tensors depend on the language used and are identifiable using the ``lang2id`` and ``id2lang`` attributes
+from the tokenizer.
+
+Here is an example using the ``xlm-clm-enfr-1024`` checkpoint (Causal language modeling, English-French):
+
+
+.. code-block::
+
+    import torch
+    from transformers import XLMTokenizer, XLMWithLMHeadModel
+
+    tokenizer = XLMTokenizer.from_pretrained("xlm-clm-1024-enfr")
+
+
+The different languages this model/tokenizer handles, as well as the ids of these languages are visible using the
+``lang2id`` attribute:
+
+.. code-block::
+
+    print(tokenizer.lang2id)  # {'en': 0, 'fr': 1}
+
+
+These ids should be used when passing a language parameter during a model pass. Let's define our inputs:
+
+.. code-block::
+
+    input_ids = torch.tensor([tokenizer.encode("Wikipedia was used to")]) # batch size of 1
+
+
+We should now define the language embedding by using the previously defined language id. We want to create a tensor
+filled with the appropriate language ids, of the same size as input_ids. For english, the id is 0:
+
+.. code-block::
+
+    language_id = tokenizer.lang2id['en']  # 0
+    langs = torch.tensor([language_id] * input_ids.shape[1])  # torch.tensor([0, 0, 0, ..., 0])
+
+    # We reshape it to be of size (batch_size, sequence_length)
+    langs = langs.view(1, -1) # is now of shape [1, sequence_length] (we have a batch size of 1)
+
+
+You can then feed it all as input to your model:
+
+.. code-block::
+
+    outputs = model(input_ids, langs=langs)
+
+
+The example `run_generation.py <https://github.com/huggingface/transformers/blob/master/examples/run_generation.py>`__
+can generate text using the CLM checkpoints from XLM, using the language embeddings.
+
+XLM without Language Embeddings
+------------------------------------------------
+
+This section concerns the following checkpoints:
+
+- ``xlm-mlm-17-1280`` (Masked language modeling, 17 languages)
+- ``xlm-mlm-100-1280`` (Masked language modeling, 100 languages)
+
+These checkpoints do not require language embeddings at inference time. These models are used to have generic
+sentence representations, differently from previously-mentioned XLM checkpoints.
+
+
+BERT
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+BERT has two checkpoints that can be used for multi-lingual tasks:
+
+- ``bert-base-multilingual-uncased`` (Masked language modeling + Next sentence prediction, 102 languages)
+- ``bert-base-multilingual-cased`` (Masked language modeling + Next sentence prediction, 104 languages)
+
+These checkpoints do not require language embeddings at inference time. They should identify the language
+used in the context and infer accordingly.
\ No newline at end of file

docs/source/pretrained_models.rst

@@ -98,6 +98,12 @@ Here is the full list of the currently provided pretrained models together with
 |                   +------------------------------------------------------------+---------------------------------------------------------------------------------------------------------------------------------------+
 |                   | ``xlm-clm-ende-1024``                                      | | 6-layer, 1024-hidden, 8-heads                                                                                                       |
 |                   |                                                            | | XLM English-German model trained with CLM (Causal Language Modeling) on the concatenation of English and German wikipedia           |
+|                   +------------------------------------------------------------+---------------------------------------------------------------------------------------------------------------------------------------+
+|                   | ``xlm-mlm-17-1280``                                        | | 16-layer, 1280-hidden, 16-heads                                                                                                     |
+|                   |                                                            | | XLM model trained with MLM (Masked Language Modeling) on 17 languages.                                                              |
+|                   +------------------------------------------------------------+---------------------------------------------------------------------------------------------------------------------------------------+
+|                   | ``xlm-mlm-100-1280``                                       | | 16-layer, 1280-hidden, 16-heads                                                                                                     |
+|                   |                                                            | | XLM model trained with MLM (Masked Language Modeling) on 100 languages.                                                             |
 +-------------------+------------------------------------------------------------+---------------------------------------------------------------------------------------------------------------------------------------+
 | RoBERTa           | ``roberta-base``                                           | | 12-layer, 768-hidden, 12-heads, 125M parameters                                                                                     |
 |                   |                                                            | | RoBERTa using the BERT-base architecture                                                                                            |
@@ -113,11 +119,15 @@ Here is the full list of the currently provided pretrained models together with
 +-------------------+------------------------------------------------------------+---------------------------------------------------------------------------------------------------------------------------------------+
 | DistilBERT        | ``distilbert-base-uncased``                                | | 6-layer, 768-hidden, 12-heads, 66M parameters                                                                                       |
 |                   |                                                            | | The DistilBERT model distilled from the BERT model `bert-base-uncased` checkpoint                                                   |
-|                   |                                                            | (see `details <https://medium.com/huggingface/distilbert-8cf3380435b5>`__)                                                            |
+|                   |                                                            | (see `details <https://github.com/huggingface/transformers/tree/master/examples/distillation>`__)                                     |
 |                   +------------------------------------------------------------+---------------------------------------------------------------------------------------------------------------------------------------+
 |                   | ``distilbert-base-uncased-distilled-squad``                | | 6-layer, 768-hidden, 12-heads, 66M parameters                                                                                       |
 |                   |                                                            | | The DistilBERT model distilled from the BERT model `bert-base-uncased` checkpoint, with an additional linear layer.                 |
-|                   |                                                            | (see `details <https://medium.com/huggingface/distilbert-8cf3380435b5>`__)                                                            |
+|                   |                                                            | (see `details <https://github.com/huggingface/transformers/tree/master/examples/distillation>`__)                                     |
+|                   +------------------------------------------------------------+---------------------------------------------------------------------------------------------------------------------------------------+
+|                   | ``distilgpt2``                                             | | 6-layer, 768-hidden, 12-heads, 82M parameters                                                                                       |
+|                   |                                                            | | The DistilGPT2 model distilled from the GPT2 model `gpt2` checkpoint.                                                               |
+|                   |                                                            | (see `details <https://github.com/huggingface/transformers/tree/master/examples/distillation>`__)                                     |
 +-------------------+------------------------------------------------------------+---------------------------------------------------------------------------------------------------------------------------------------+
 | CTRL              | ``ctrl``                                                   | | 48-layer, 1280-hidden, 16-heads, 1.6B parameters                                                                                    |
 |                   |                                                            | | Salesforce's Large-sized CTRL English model                                                                                         |

examples/distillation/README.md

-# DistilBERT
+# Distil*
 
-This folder contains the original code used to train DistilBERT as well as examples showcasing how to use DistilBERT.
+This folder contains the original code used to train Distil* as well as examples showcasing how to use DistilBERT and DistilGPT2.
+
+**2019, October 3rd - Update** We release our [NeurIPS workshop paper](https://arxiv.org/abs/1910.01108) explaining our approach on **DistilBERT**. It includes updated results and further experiments. We applied the same method to GPT2 and release the weights of **DistilGPT2**. DistilGPT2 is two times faster and 33% smaller than GPT2.
 
 **2019, September 19th - Update:** We fixed bugs in the code and released an upadted version of the weights trained with a modification of the distillation loss. DistilBERT now reaches 97% of `BERT-base`'s performance on GLUE, and 86.9 F1 score on SQuAD v1.1 dev set (compared to 88.5 for `BERT-base`). We will publish a formal write-up of our approach in the near future!
 
-## What is DistilBERT
+## What is Distil*
+
+Distil* is a class of compressed models that started with DistilBERT. DistilBERT stands for Distillated-BERT. DistilBERT is a small, fast, cheap and light Transformer model based on Bert architecture. It has 40% less parameters than `bert-base-uncased`, runs 60% faster while preserving 97% of BERT's performances as measured on the GLUE language understanding benchmark. DistilBERT is trained using knowledge distillation, a technique to compress a large model called the teacher into a smaller model called the student. By distillating Bert, we obtain a smaller Transformer model that bears a lot of similarities with the original BERT model while being lighter, smaller and faster to run. DistilBERT is thus an interesting option to put large-scaled trained Transformer model into production.
 
-DistilBERT stands for Distillated-BERT. DistilBERT is a small, fast, cheap and light Transformer model based on Bert architecture. It has 40% less parameters than `bert-base-uncased`, runs 60% faster while preserving 97% of BERT's performances as measured on the GLUE language understanding benchmark. DistilBERT is trained using knowledge distillation, a technique to compress a large model called the teacher into a smaller model called the student. By distillating Bert, we obtain a smaller Transformer model that bears a lot of similarities with the original BERT model while being lighter, smaller and faster to run. DistilBERT is thus an interesting option to put large-scaled trained Transformer model into production.
+We have applied the same method to GPT2 and release the weights of the compressed model. On the [WikiText-103](https://blog.einstein.ai/the-wikitext-long-term-dependency-language-modeling-dataset/) benchmark, GPT2 reaches a perplexity on the test set of 15.0 compared to 18.5 for DistilGPT2 (after fine-tuning on the train set).
 
-For more information on DistilBERT, please refer to our [detailed blog post](https://medium.com/huggingface/smaller-faster-cheaper-lighter-introducing-distilbert-a-distilled-version-of-bert-8cf3380435b5
-). *Please note that we will publish a formal write-up with updated and more complete results in the near future (September 19th).*
+For more information on DistilBERT, please refer to our [NeurIPS workshop paper](https://arxiv.org/abs/1910.01108). The paper superseeds our [previous blogpost](https://medium.com/huggingface/distilbert-8cf3380435b5) with a different distillation loss and better performances.
 
-Here's the updated results on the dev sets of GLUE:
+Here are the results on the dev sets of GLUE:
 
-| Model      | Macro-score | CoLA | MNLI | MRPC | QNLI | QQP | RTE | SST-2 | STS-B | WNLI |
+| Model      | Macro-score | CoLA | MNLI | MRPC | QNLI | QQP  | RTE  | SST-2| STS-B| WNLI |
 | :---:      |    :---:    | :---:| :---:| :---:| :---:| :---:| :---:| :---:| :---:| :---:|
 | BERT-base  |  **77.6**   | 48.9 | 84.3 | 88.6 | 89.3 | 89.5 | 71.3 | 91.7 | 91.2 | 43.7 |
-| DistilBERT |  **75.2**   | 49.1 | 81.8 | 90.2 | 87.0 | 89.2 | 62.9 | 92.7 | 90.7 | 44.4 |
+| DistilBERT |  **76.8**   | 49.1 | 81.8 | 90.2 | 90.2 | 89.2 | 62.9 | 92.7 | 90.7 | 44.4 |
 
 ## Setup
 
@@ -26,10 +29,12 @@ This part of the library has only be tested with Python3.6+. There are few speci
 
 ## How to use DistilBERT
 
-Transformers includes two pre-trained DistilBERT models, currently only provided for English (we are investigating the possibility to train and release a multilingual version of DistilBERT):
+Transformers includes two pre-trained Distil* models, currently only provided for English (we are investigating the possibility to train and release a multilingual version of DistilBERT):
 
 - `distilbert-base-uncased`: DistilBERT English language model pretrained on the same data used to pretrain Bert (concatenation of the Toronto Book Corpus and full English Wikipedia) using distillation with the supervision of the `bert-base-uncased` version of Bert. The model has 6 layers, 768 dimension and 12 heads, totalizing 66M parameters.
 - `distilbert-base-uncased-distilled-squad`: A finetuned version of `distilbert-base-uncased` finetuned using (a second step of) knwoledge distillation on SQuAD 1.0. This model reaches a F1 score of 86.9 on the dev set (for comparison, Bert `bert-base-uncased` version reaches a 88.5 F1 score).
+- `distilgpt2`: DistilGPT2 English language model pretrained with the supervision of `gpt2` (the smallest version of GPT2) on [OpenWebTextCorpus](https://skylion007.github.io/OpenWebTextCorpus/), a reproduction of OpenAI's WebText dataset and . The model has 6 layers, 768 dimension and 12 heads, totalizing 82M (compared to 124M parameters for GPT2). On average, DistilGPT2 is two times faster than GPT2.
+- and more to come! 🤗🤗🤗
 
 Using DistilBERT is very similar to using BERT. DistilBERT share the same tokenizer as BERT's `bert-base-uncased` even though we provide a link to this tokenizer under the `DistilBertTokenizer` name to have a consistent naming between the library models.
 
@@ -42,9 +47,11 @@ outputs = model(input_ids)
 last_hidden_states = outputs[0]  # The last hidden-state is the first element of the output tuple
 ```
 
-## How to train DistilBERT
+Similarly, using DistilGPT2 simply consists in calling the GPT2 classes from a different pretrained checkpoint: `model = GPT2Model.from_pretrained('distilgpt2')`.
+
+## How to train Distil*
 
-In the following, we will explain how you can train your own compressed model.
+In the following, we will explain how you can train DistilBERT.
 
 ### A. Preparing the data
 
@@ -57,7 +64,8 @@ First, we will binarize the data, i.e. tokenize the data and convert each token
 ```bash
 python scripts/binarized_data.py \
     --file_path data/dump.txt \
-    --bert_tokenizer bert-base-uncased \
+    --tokenizer_type bert \
+    --tokenizer_name bert-base-uncased \
     --dump_file data/binarized_text
 ```
 
@@ -66,7 +74,8 @@ Our implementation of masked language modeling loss follows [XLM](https://github
 ```bash
 python scripts/token_counts.py \
     --data_file data/binarized_text.bert-base-uncased.pickle \
-    --token_counts_dump data/token_counts.bert-base-uncased.pickle
+    --token_counts_dump data/token_counts.bert-base-uncased.pickle \
+    --vocab_size 30522
 ```
 
 ### B. Training
@@ -75,6 +84,12 @@ Training with distillation is really simple once you have pre-processed the data
 
 ```bash
 python train.py \
+    --student_type distilbert \
+    --student_config training_configs/distilbert-base-uncased.json \
+    --teacher_type bert \
+    --teacher_name bert-base-uncased \
+    --alpha_ce 5.0 --alpha_mlm 2.0 --alpha_cos 1.0 --mlm \
+    --freeze_pos_embs \
     --dump_path serialization_dir/my_first_training \
     --data_file data/binarized_text.bert-base-uncased.pickle \
     --token_counts data/token_counts.bert-base-uncased.pickle \
@@ -83,7 +98,7 @@ python train.py \
 
 By default, this will launch a training on a single GPU (even if more are available on the cluster). Other parameters are available in the command line, please look in `train.py` or run `python train.py --help` to list them.
 
-We highly encourage you to use distributed training for training DistilBert as the training corpus is quite large. Here's an example that runs a distributed training on a single node having 4 GPUs:
+We highly encourage you to use distributed training for training DistilBERT as the training corpus is quite large. Here's an example that runs a distributed training on a single node having 4 GPUs:
 
 ```bash
 export NODE_RANK=0
@@ -105,11 +120,17 @@ python -m torch.distributed.launch \
     train.py \
         --force \
         --n_gpu $WORLD_SIZE \
+        --student_type distilbert \
+        --student_config training_configs/distilbert-base-uncased.json \
+        --teacher_type bert \
+        --teacher_name bert-base-uncased \
+        --alpha_ce 0.33 --alpha_mlm 0.33 --alpha_cos 0.33 --mlm \
+        --freeze_pos_embs \
+        --dump_path serialization_dir/my_first_training \
         --data_file data/binarized_text.bert-base-uncased.pickle \
-        --token_counts data/token_counts.bert-base-uncased.pickle \
-        --dump_path serialization_dir/my_first_distillation
+        --token_counts data/token_counts.bert-base-uncased.pickle
 ```
 
-**Tips:** Starting distillated training with good initialization of the model weights is crucial to reach decent performance. In our experiments, we initialized our model from a few layers of the teacher (Bert) itself! Please refer to `scripts/extract_for_distil.py` to create a valid initialization checkpoint and use `--from_pretrained_weights` and `--from_pretrained_config` arguments to use this initialization for the distilled training!
+**Tips:** Starting distillated training with good initialization of the model weights is crucial to reach decent performance. In our experiments, we initialized our model from a few layers of the teacher (Bert) itself! Please refer to `scripts/extract.py` and `scripts/extract_distilbert.py` to create a valid initialization checkpoint and use `--student_pretrained_weights` argument to use this initialization for the distilled training!
 
 Happy distillation!

examples/distillation/distiller.py

@@ -12,8 +12,8 @@
 # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 # See the License for the specific language governing permissions and
 # limitations under the License.
-""" The distiller to distil DistilBERT
-    adapted in part from Facebook, Inc XLM model (https://github.com/facebookresearch/XLM)
+""" The distiller to distil the student.
+    Adapted in part from Facebook, Inc XLM model (https://github.com/facebookresearch/XLM)
 """
 import os
 import math
@@ -28,16 +28,19 @@ import torch
 import torch.nn as nn
 import torch.nn.functional as F
 from torch.optim import AdamW
+from torch.utils.data.distributed import DistributedSampler
+from torch.utils.data import RandomSampler, BatchSampler, DataLoader
 
 from transformers import WarmupLinearSchedule
 
 from utils import logger
-from dataset import Dataset
+from lm_seqs_dataset import LmSeqsDataset
+from grouped_batch_sampler import GroupedBatchSampler, create_lengths_groups
 
 class Distiller:
     def __init__(self,
                  params: dict,
-                 dataloader: Dataset,
+                 dataset: LmSeqsDataset,
                  token_probs: torch.tensor,
                  student: nn.Module,
                  teacher: nn.Module):
@@ -50,33 +53,47 @@ class Distiller:
         self.student = student
         self.teacher = teacher
 
-        self.dataloader = dataloader
-        if self.params.n_gpu > 1:
-            self.dataloader.split()
-        self.get_iterator(seed=params.seed)
+        self.student_config = student.config
+        self.vocab_size = student.config.vocab_size
+
+        if params.n_gpu <= 1:
+            sampler = RandomSampler(dataset)
+        else:
+            sampler = DistributedSampler(dataset)
+
+        if params.group_by_size:
+            groups = create_lengths_groups(lengths=dataset.lengths, k=params.max_model_input_size)
+            sampler = GroupedBatchSampler(sampler=sampler, group_ids=groups, batch_size=params.batch_size)
+        else:
+            sampler = BatchSampler(sampler=sampler, batch_size=params.batch_size, drop_last=False)
+
+        self.dataloader = DataLoader(dataset=dataset,
+                                     batch_sampler=sampler,
+                                     collate_fn=dataset.batch_sequences)
 
         self.temperature = params.temperature
         assert self.temperature > 0.
 
         self.alpha_ce = params.alpha_ce
         self.alpha_mlm = params.alpha_mlm
+        self.alpha_clm = params.alpha_clm
         self.alpha_mse = params.alpha_mse
         self.alpha_cos = params.alpha_cos
-        assert self.alpha_ce >= 0.
-        assert self.alpha_mlm >= 0.
-        assert self.alpha_mse >= 0.
-        assert self.alpha_cos >= 0.
-        assert self.alpha_ce + self.alpha_mlm + self.alpha_mse + self.alpha_cos > 0.
-
-        self.mlm_mask_prop = params.mlm_mask_prop
-        assert 0.0 <= self.mlm_mask_prop <= 1.0
-        assert params.word_mask + params.word_keep + params.word_rand == 1.0
-        self.pred_probs = torch.FloatTensor([params.word_mask, params.word_keep, params.word_rand])
-        self.pred_probs = self.pred_probs.to(f'cuda:{params.local_rank}') if params.n_gpu > 0 else self.pred_probs
-        self.token_probs = token_probs.to(f'cuda:{params.local_rank}') if params.n_gpu > 0 else token_probs
-        if self.fp16:
-            self.pred_probs = self.pred_probs.half()
-            self.token_probs = self.token_probs.half()
+
+        self.mlm = params.mlm
+        if self.mlm:
+            logger.info(f'Using MLM loss for LM step.')
+            self.mlm_mask_prop = params.mlm_mask_prop
+            assert 0.0 <= self.mlm_mask_prop <= 1.0
+            assert params.word_mask + params.word_keep + params.word_rand == 1.0
+            self.pred_probs = torch.FloatTensor([params.word_mask, params.word_keep, params.word_rand])
+            self.pred_probs = self.pred_probs.to(f'cuda:{params.local_rank}') if params.n_gpu > 0 else self.pred_probs
+            self.token_probs = token_probs.to(f'cuda:{params.local_rank}') if params.n_gpu > 0 else token_probs
+            if self.fp16:
+                self.pred_probs = self.pred_probs.half()
+                self.token_probs = self.token_probs.half()
+        else:
+            logger.info(f'Using CLM loss for LM step.')
 
         self.epoch = 0
         self.n_iter = 0
@@ -86,12 +103,13 @@ class Distiller:
         self.last_loss = 0
         self.last_loss_ce = 0
         self.last_loss_mlm = 0
+        self.last_loss_clm = 0
         if self.alpha_mse > 0.: self.last_loss_mse = 0
         if self.alpha_cos > 0.: self.last_loss_cos = 0
         self.last_log = 0
 
         self.ce_loss_fct = nn.KLDivLoss(reduction='batchmean')
-        self.mlm_loss_fct = nn.CrossEntropyLoss(ignore_index=-1)
+        self.lm_loss_fct = nn.CrossEntropyLoss(ignore_index=-1)
         if self.alpha_mse > 0.:
             self.mse_loss_fct = nn.MSELoss(reduction='sum')
         if self.alpha_cos > 0.:
@@ -99,7 +117,7 @@ class Distiller:
 
         logger.info('--- Initializing model optimizer')
         assert params.gradient_accumulation_steps >= 1
-        self.num_steps_epoch = int(len(self.dataloader) / params.batch_size) + 1
+        self.num_steps_epoch = len(self.dataloader)
         num_train_optimization_steps = int(self.num_steps_epoch / params.gradient_accumulation_steps * params.n_epoch) + 1
 
         no_decay = ['bias', 'LayerNorm.weight']
@@ -140,43 +158,18 @@ class Distiller:
                 logger.info("Using nn.parallel.DistributedDataParallel for distributed training.")
                 self.student = DistributedDataParallel(self.student,
                                                        device_ids=[params.local_rank],
-                                                       output_device=params.local_rank)
+                                                       output_device=params.local_rank,
+                                                       find_unused_parameters=True)
 
         self.is_master = params.is_master
         if self.is_master:
             logger.info('--- Initializing Tensorboard')
             self.tensorboard = SummaryWriter(log_dir=os.path.join(self.dump_path, 'log', 'train'))
-            self.tensorboard.add_text(tag='config', text_string=str(self.params), global_step=0)
-
-    def get_iterator(self,
-                     seed: int = None):
-        """
-        Initialize the data iterator.
-        Each process has its own data iterator (iterating on his own random portion of the dataset).
+            self.tensorboard.add_text(tag='config/training', text_string=str(self.params), global_step=0)
+            self.tensorboard.add_text(tag='config/student', text_string=str(self.student_config), global_step=0)
 
-        Input:
-        ------
-            seed: `int` - The random seed.
-        """
-        logger.info('--- Initializing Data Iterator')
-        self.data_iterator = self.dataloader.get_iterator(seed=seed)
-
-    def get_batch(self):
-        """
-        Call the data iterator to output a new batch.
-        If the data iterator went through the whole dataset, create a new iterator.
-        """
-        assert hasattr(self, 'data_iterator')
-        try:
-            x = next(self.data_iterator)
-        except StopIteration:
-            logger.warning('--- Went through the whole dataset. Creating new data iterator.')
-            self.data_iterator = self.dataloader.get_iterator()
-            x = next(self.data_iterator)
-        return x
-
-    def prepare_batch(self,
-                      batch):
+    def prepare_batch_mlm(self,
+                          batch):
         """
         Prepare the batch: from the token_ids and the lenghts, compute the attention mask and the masked label for MLM.
 
@@ -222,7 +215,7 @@ class Distiller:
                 assert pred_mask.sum().item() % 8 == 0, pred_mask.sum().item()
 
         _token_ids_real = token_ids[pred_mask]
-        _token_ids_rand = _token_ids_real.clone().random_(self.params.vocab_size)
+        _token_ids_rand = _token_ids_real.clone().random_(self.vocab_size)
         _token_ids_mask = _token_ids_real.clone().fill_(self.params.special_tok_ids['mask_token'])
         probs = torch.multinomial(self.pred_probs, len(_token_ids_real), replacement=True)
         _token_ids = _token_ids_mask * (probs == 0).long() + _token_ids_real * (probs == 1).long() + _token_ids_rand * (probs == 2).long()
@@ -230,8 +223,41 @@ class Distiller:
 
         mlm_labels[~pred_mask] = -1 # previously `mlm_labels[1-pred_mask] = -1`, cf pytorch 1.2.0 compatibility
 
+        # sanity checks
+        assert 0 <= token_ids.min() <= token_ids.max() < self.vocab_size
+
         return token_ids, attn_mask, mlm_labels
 
+    def prepare_batch_clm(self,
+                          batch):
+        """
+        Prepare the batch: from the token_ids and the lenghts, compute the attention mask and the labels for CLM.
+
+        Input:
+        ------
+            batch: `Tuple`
+                token_ids: `torch.tensor(bs, seq_length)` - The token ids for each of the sequence. It is padded.
+                lengths: `torch.tensor(bs)` - The lengths of each of the sequences in the batch.
+
+        Output:
+        -------
+            token_ids: `torch.tensor(bs, seq_length)` - The token ids after the modifications for MLM.
+            attn_mask: `torch.tensor(bs, seq_length)` - The attention mask for the self-attention.
+            clm_labels: `torch.tensor(bs, seq_length)` - The causal languge modeling labels. There is a -1 where there is nothing to predict.
+        """
+        token_ids, lengths = batch
+        token_ids, lengths = self.round_batch(x=token_ids, lengths=lengths)
+        assert token_ids.size(0) == lengths.size(0)
+
+        attn_mask = (torch.arange(token_ids.size(1), dtype=torch.long, device=lengths.device) < lengths[:, None])
+        clm_labels = token_ids.new(token_ids.size()).copy_(token_ids)
+        clm_labels[~attn_mask] = -1 # previously `clm_labels[1-attn_mask] = -1`, cf pytorch 1.2.0 compatibility
+
+        # sanity checks
+        assert 0 <= token_ids.min() <= token_ids.max() < self.vocab_size
+
+        return token_ids, attn_mask, clm_labels
+
     def round_batch(self,
                     x: torch.tensor,
                     lengths: torch.tensor):
@@ -269,7 +295,10 @@ class Distiller:
         if ml1 % 8 != 0:
             pad = 8 - (ml1 % 8)
             ml2 = ml1 + pad
-            pad_id = self.params.special_tok_ids['pad_token']
+            if self.mlm:
+                pad_id = self.params.special_tok_ids['pad_token']
+            else:
+                pad_id = self.params.special_tok_ids['unk_token']
             padding_tensor = torch.zeros(bs2, pad, dtype=torch.long, device=x.device).fill_(pad_id)
             x = torch.cat([x, padding_tensor], 1)
             assert x.size() == (bs2, ml2)
@@ -292,14 +321,16 @@ class Distiller:
             if self.multi_gpu:
                 torch.distributed.barrier()
 
-            iter_bar = trange(self.num_steps_epoch, desc="-Iter", disable=self.params.local_rank not in [-1, 0])
-            for __ in range(self.num_steps_epoch):
-                batch = self.get_batch()
+            iter_bar = tqdm(self.dataloader, desc="-Iter", disable=self.params.local_rank not in [-1, 0])
+            for batch in iter_bar:
                 if self.params.n_gpu > 0:
                     batch = tuple(t.to(f'cuda:{self.params.local_rank}') for t in batch)
-                token_ids, attn_mask, mlm_labels = self.prepare_batch(batch=batch)
 
-                self.step(input_ids=token_ids, attention_mask=attn_mask, mlm_labels=mlm_labels)
+                if self.mlm:
+                    token_ids, attn_mask, lm_labels = self.prepare_batch_mlm(batch=batch)
+                else:
+                    token_ids, attn_mask, lm_labels = self.prepare_batch_clm(batch=batch)
+                self.step(input_ids=token_ids, attention_mask=attn_mask, lm_labels=lm_labels)
 
                 iter_bar.update()
                 iter_bar.set_postfix({'Last_loss': f'{self.last_loss:.2f}',
@@ -317,7 +348,7 @@ class Distiller:
     def step(self,
              input_ids: torch.tensor,
              attention_mask: torch.tensor,
-             mlm_labels: torch.tensor):
+             lm_labels: torch.tensor):
         """
         One optimization step: forward of student AND teacher, backward on the loss (for gradient accumulation),
         and possibly a parameter update (depending on the gradient accumulation).
@@ -326,17 +357,22 @@ class Distiller:
         ------
         input_ids: `torch.tensor(bs, seq_length)` - The token ids.
         attention_mask: `torch.tensor(bs, seq_length)` - The attention mask for self attention.
-        mlm_labels: `torch.tensor(bs, seq_length)` - The masked language modeling labels.
+        lm_labels: `torch.tensor(bs, seq_length)` - The language modeling labels (mlm labels for MLM and clm labels for CLM).
         """
-        s_logits, s_hidden_states = self.student(input_ids=input_ids, attention_mask=attention_mask)     # (bs, seq_length, voc_size)
-        with torch.no_grad():
-            t_logits, t_hidden_states = self.teacher(input_ids=input_ids, attention_mask=attention_mask) # (bs, seq_length, voc_size)
+        if self.mlm:
+            s_logits, s_hidden_states = self.student(input_ids=input_ids, attention_mask=attention_mask)     # (bs, seq_length, voc_size)
+            with torch.no_grad():
+                t_logits, t_hidden_states = self.teacher(input_ids=input_ids, attention_mask=attention_mask) # (bs, seq_length, voc_size)
+        else:
+            s_logits, _, s_hidden_states = self.student(input_ids=input_ids, attention_mask=None)            # (bs, seq_length, voc_size)
+            with torch.no_grad():
+                t_logits, _, t_hidden_states = self.teacher(input_ids=input_ids, attention_mask=None)           # (bs, seq_length, voc_size)
         assert s_logits.size() == t_logits.size()
 
         #https://github.com/peterliht/knowledge-distillation-pytorch/blob/master/model/net.py#L100
         #https://github.com/peterliht/knowledge-distillation-pytorch/issues/2
         if self.params.restrict_ce_to_mask:
-            mask = (mlm_labels>-1).unsqueeze(-1).expand_as(s_logits)   # (bs, seq_lenth, voc_size)
+            mask = (lm_labels>-1).unsqueeze(-1).expand_as(s_logits)    # (bs, seq_lenth, voc_size)
         else:
             mask = attention_mask.unsqueeze(-1).expand_as(s_logits)    # (bs, seq_lenth, voc_size)
         s_logits_slct = torch.masked_select(s_logits, mask)            # (bs * seq_length * voc_size) modulo the 1s in mask
@@ -348,13 +384,20 @@ class Distiller:
         loss_ce = self.ce_loss_fct(F.log_softmax(s_logits_slct/self.temperature, dim=-1),
                                    F.softmax(t_logits_slct/self.temperature, dim=-1)) * (self.temperature)**2
         loss = self.alpha_ce*loss_ce
+
         if self.alpha_mlm > 0.:
-            loss_mlm = self.mlm_loss_fct(s_logits.view(-1, s_logits.size(-1)), mlm_labels.view(-1))
+            loss_mlm = self.lm_loss_fct(s_logits.view(-1, s_logits.size(-1)), lm_labels.view(-1))
             loss += self.alpha_mlm * loss_mlm
+        if self.alpha_clm > 0.:
+            shift_logits = s_logits[..., :-1, :].contiguous()
+            shift_labels = lm_labels[..., 1:].contiguous()
+            loss_clm = self.lm_loss_fct(shift_logits.view(-1, shift_logits.size(-1)),
+                                        shift_labels.view(-1))
+            loss += self.alpha_clm * loss_clm
+
         if self.alpha_mse > 0.:
             loss_mse = self.mse_loss_fct(s_logits_slct, t_logits_slct)/s_logits_slct.size(0) # Reproducing batchmean reduction
             loss += self.alpha_mse * loss_mse
-        
         if self.alpha_cos > 0.:
             s_hidden_states = s_hidden_states[-1]                              # (bs, seq_length, dim)
             t_hidden_states = t_hidden_states[-1]                              # (bs, seq_length, dim)
@@ -376,6 +419,8 @@ class Distiller:
         self.last_loss_ce = loss_ce.item()
         if self.alpha_mlm > 0.:
             self.last_loss_mlm = loss_mlm.item()
+        if self.alpha_clm > 0.:
+            self.last_loss_clm = loss_clm.item()
         if self.alpha_mse > 0.:
             self.last_loss_mse = loss_mse.item()
         if self.alpha_cos > 0.:
@@ -452,6 +497,8 @@ class Distiller:
         self.tensorboard.add_scalar(tag="losses/loss_ce", scalar_value=self.last_loss_ce, global_step=self.n_total_iter)
         if self.alpha_mlm > 0.:
             self.tensorboard.add_scalar(tag="losses/loss_mlm", scalar_value=self.last_loss_mlm, global_step=self.n_total_iter)
+        if self.alpha_clm > 0.:
+            self.tensorboard.add_scalar(tag="losses/loss_clm", scalar_value=self.last_loss_clm, global_step=self.n_total_iter)
         if self.alpha_mse > 0.:
             self.tensorboard.add_scalar(tag="losses/loss_mse", scalar_value=self.last_loss_mse, global_step=self.n_total_iter)
         if self.alpha_cos > 0.:

examples/distillation/grouped_batch_sampler.py

+# coding=utf-8
+# Copyright 2019-present, the HuggingFace Inc. team and Facebook, Inc.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+""" Adapted from PyTorch Vision (https://github.com/pytorch/vision/blob/master/references/detection/group_by_aspect_ratio.py)
+"""
+import bisect
+import copy
+from collections import defaultdict
+import numpy as np
+
+from torch.utils.data.sampler import BatchSampler, Sampler
+
+from utils import logger
+
+def _quantize(x, bins):
+    bins = copy.deepcopy(bins)
+    bins = sorted(bins)
+    quantized = list(map(lambda y: bisect.bisect_right(bins, y), x))
+    return quantized
+
+def create_lengths_groups(lengths, k=0):
+    bins = np.arange(start=3, stop=k, step=4).tolist() if k > 0 else [10]
+    groups = _quantize(lengths, bins)
+    # count number of elements per group
+    counts = np.unique(groups, return_counts=True)[1]
+    fbins = [0] + bins + [np.inf]
+    logger.info("Using {} as bins for aspect lengths quantization".format(fbins))
+    logger.info("Count of instances per bin: {}".format(counts))
+    return groups
+
+class GroupedBatchSampler(BatchSampler):
+    """
+    Wraps another sampler to yield a mini-batch of indices.
+    It enforces that the batch only contain elements from the same group.
+    It also tries to provide mini-batches which follows an ordering which is
+    as close as possible to the ordering from the original sampler.
+    Arguments:
+        sampler (Sampler): Base sampler.
+        group_ids (list[int]): If the sampler produces indices in range [0, N),
+            `group_ids` must be a list of `N` ints which contains the group id of each sample.
+            The group ids must be a continuous set of integers starting from
+            0, i.e. they must be in the range [0, num_groups).
+        batch_size (int): Size of mini-batch.
+    """
+    def __init__(self, sampler, group_ids, batch_size):
+        if not isinstance(sampler, Sampler):
+            raise ValueError(
+                "sampler should be an instance of "
+                "torch.utils.data.Sampler, but got sampler={}".format(sampler)
+            )
+        self.sampler = sampler
+        self.group_ids = group_ids
+        self.batch_size = batch_size
+
+    def __iter__(self):
+        buffer_per_group = defaultdict(list)
+        samples_per_group = defaultdict(list)
+
+        num_batches = 0
+        for idx in self.sampler:
+            group_id = self.group_ids[idx]
+            buffer_per_group[group_id].append(idx)
+            samples_per_group[group_id].append(idx)
+            if len(buffer_per_group[group_id]) == self.batch_size:
+                yield buffer_per_group[group_id] #TODO
+                num_batches += 1
+                del buffer_per_group[group_id]
+            assert len(buffer_per_group[group_id]) < self.batch_size
+
+        # now we have run out of elements that satisfy
+        # the group criteria, let's return the remaining
+        # elements so that the size of the sampler is
+        # deterministic
+        expected_num_batches = len(self)
+        num_remaining = expected_num_batches - num_batches
+        if num_remaining > 0:
+            # for the remaining batches, group the batches by similar lengths
+            batch_idx = []
+            for group_id, idxs in sorted(buffer_per_group.items(), key=lambda x: x[0]):
+                batch_idx.extend(idxs)
+                if len(batch_idx) >= self.batch_size:
+                    yield batch_idx[:self.batch_size]
+                    batch_idx = batch_idx[self.batch_size:]
+                    num_remaining -= 1
+            if len(batch_idx) > 0:
+                yield batch_idx
+                num_remaining -= 1
+        assert num_remaining == 0
+
+    def __len__(self):
+        """
+        Return the number of mini-batches rather than the number of samples.
+        """
+        return (len(self.sampler) + self.batch_size - 1) // self.batch_size

examples/distillation/dataset.py → examples/distillation/lm_seqs_dataset.py

@@ -12,30 +12,33 @@
 # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 # See the License for the specific language governing permissions and
 # limitations under the License.
-""" Dataloaders to train DistilBERT
+""" Dataset to distilled models
     adapted in part from Facebook, Inc XLM model (https://github.com/facebookresearch/XLM)
 """
-from typing import List
-import math
-from itertools import chain
-from collections import Counter
-import numpy as np
 import torch
+from torch.utils.data import Dataset
 
+import numpy as np
 from utils import logger
 
-class Dataset:
+class LmSeqsDataset(Dataset):
+    """Custom Dataset wrapping language modeling sequences.
+
+    Each sample will be retrieved by indexing the list of token_ids and their corresponding lengths.
+
+    Input:
+    ------
+        params: `NameSpace` parameters
+        data: `List[np.array[int]]
+    """
+
     def __init__(self,
                  params,
                  data):
         self.params = params
-        self.tokens_per_batch = params.tokens_per_batch
-        self.batch_size = params.batch_size
-        self.shuffle = params.shuffle
-        self.group_by_size = params.group_by_size
 
         self.token_ids = np.array(data)
-        self.lengths = np.uint16([len(t) for t in data])
+        self.lengths = np.array([len(t) for t in data])
 
         self.check()
         self.remove_long_sequences()
@@ -43,6 +46,9 @@ class Dataset:
         self.check()
         self.print_statistics()
 
+    def __getitem__(self, index):
+        return (self.token_ids[index], self.lengths[index])
+
     def __len__(self):
         return len(self.lengths)
 
@@ -51,12 +57,14 @@ class Dataset:
         Some sanity checks
         """
         assert len(self.token_ids) == len(self.lengths)
+        assert all(self.lengths[i] == len(self.token_ids[i]) for i in range(len(self.lengths))) 
 
     def remove_long_sequences(self):
         """
-        Sequences that are too long are splitted by chunk of max_position_embeddings.
+        Sequences that are too long are splitted by chunk of max_model_input_size.
         """
-        indices = self.lengths >= self.params.max_position_embeddings
+        max_len = self.params.max_model_input_size
+        indices = self.lengths > max_len
         logger.info(f'Splitting {sum(indices)} too long sequences.')
 
         def divide_chunks(l, n):
@@ -64,10 +72,13 @@ class Dataset:
 
         new_tok_ids = []
         new_lengths = []
-        cls_id, sep_id = self.params.special_tok_ids['cls_token'], self.params.special_tok_ids['sep_token']
-        max_len = self.params.max_position_embeddings
+        if self.params.mlm:
+            cls_id, sep_id = self.params.special_tok_ids['cls_token'], self.params.special_tok_ids['sep_token']
+        else:
+            cls_id, sep_id = self.params.special_tok_ids['bos_token'], self.params.special_tok_ids['eos_token']
 
         for seq_, len_ in zip(self.token_ids, self.lengths):
+            assert (seq_[0] == cls_id) and (seq_[-1] == sep_id), seq_
             if len_ <= max_len:
                 new_tok_ids.append(seq_)
                 new_lengths.append(len_)
@@ -79,6 +90,7 @@ class Dataset:
                     if sub_s[-1] != sep_id:
                         sub_s = np.insert(sub_s, len(sub_s), sep_id)
                     assert len(sub_s) <= max_len
+                    assert (sub_s[0] == cls_id) and (sub_s[-1] == sep_id), sub_s
                     sub_seqs.append(sub_s)
 
                 new_tok_ids.extend(sub_seqs)
@@ -113,89 +125,27 @@ class Dataset:
         # nb_unkown = sum([(t==unk_idx).sum() for t in self.token_ids])
         # logger.info(f'{nb_unkown} unknown tokens (covering {100*nb_unkown/data_len:.2f}% of the data)')
 
-    def select_data(self, a: int, b: int):
-        """
-        Select a subportion of the data.
-        """
-        n_sequences = len(self)
-        assert 0 <= a < b <= n_sequences, ValueError(f'`0 <= a < b <= n_sequences` is not met with a={a} and b={b}')
-
-        logger.info(f'Selecting sequences from {a} to {b} (excluded).')
-        self.token_ids = self.token_ids[a:b]
-        self.lengths = self.lengths[a:b]
-
-        self.check()
-
-    def split(self):
-        """
-        Distributed training: split the data accross the processes.
-        """
-        assert self.params.n_gpu > 1
-        logger.info('Splitting the data accross the processuses.')
-        n_seq = len(self)
-        n_seq_per_procesus = n_seq // self.params.world_size
-        a = n_seq_per_procesus * self.params.global_rank
-        b = a + n_seq_per_procesus
-        self.select_data(a=a, b=b)
-
     def batch_sequences(self,
-                        token_ids: List[List[int]],
-                        lengths: List[int]):
+                        batch):
         """
         Do the padding and transform into torch.tensor.
         """
+        token_ids = [t[0] for t in batch]
+        lengths = [t[1] for t in batch]
         assert len(token_ids) == len(lengths)
 
         # Max for paddings
         max_seq_len_ = max(lengths)
 
         # Pad token ids
-        pad_idx = self.params.special_tok_ids['pad_token']
+        if self.params.mlm:
+            pad_idx = self.params.special_tok_ids['pad_token']
+        else:
+            pad_idx = self.params.special_tok_ids['unk_token']
         tk_ = [list(t.astype(int)) + [pad_idx]*(max_seq_len_-len(t)) for t in token_ids]
         assert len(tk_) == len(token_ids)
         assert all(len(t) == max_seq_len_ for t in tk_)
 
-        tk_t = torch.tensor(tk_)                  # (bs, max_seq_len_)
-        lg_t = torch.tensor(lengths.astype(int))  # (bs)
+        tk_t = torch.tensor(tk_)      # (bs, max_seq_len_)
+        lg_t = torch.tensor(lengths)  # (bs)
         return tk_t, lg_t
-
-    def get_batches_iterator(self,
-                             batches):
-        """
-        Return an iterator over batches.
-        """
-        for sequences_ids in batches:
-            token_ids, lengths = self.batch_sequences(self.token_ids[sequences_ids],
-                                                    self.lengths[sequences_ids])
-            yield (token_ids, lengths)
-
-    def get_iterator(self,
-                     seed: int = None):
-        """
-        Return a data iterator.
-        """
-        rng = np.random.RandomState(seed)
-
-        n_sequences = len(self)
-        indices = np.arange(n_sequences)
-
-        if self.group_by_size:
-            indices = indices[np.argsort(self.lengths[indices], kind='mergesort')]
-
-        if self.tokens_per_batch == -1:
-            batches = np.array_split(indices, math.ceil(len(indices) * 1. / self.batch_size))
-        else:
-            assert self.tokens_per_batch > 0
-            batch_ids = np.cumsum(self.lengths[indices]) // self.tokens_per_batch
-            _, bounds = np.unique(batch_ids, return_index=True)
-            batches = [indices[bounds[i]:bounds[i + 1]] for i in range(len(bounds) - 1)]
-            if bounds[-1] < len(indices):
-                batches.append(indices[bounds[-1]:])
-
-        if self.shuffle:
-            rng.shuffle(batches)
-
-        assert n_sequences == sum([len(x) for x in batches])
-        assert self.lengths[indices].sum() == sum([self.lengths[x].sum() for x in batches])
-
-        return self.get_batches_iterator(batches=batches)

examples/distillation/requirements.txt

@@ -3,4 +3,4 @@ tensorboard>=1.14.0
 tensorboardX==1.8
 psutil==5.6.3
 scipy==1.3.1
-pytorch_transformers==1.2.0
+transformers==2.0.0

examples/distillation/scripts/binarized_data.py

@@ -13,14 +13,14 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 """
-Preprocessing script before training DistilBERT.
+Preprocessing script before distillation.
 """
 import argparse
 import pickle
 import random
 import time
 import numpy as np
-from transformers import BertTokenizer, RobertaTokenizer
+from transformers import BertTokenizer, RobertaTokenizer, GPT2Tokenizer
 import logging
 
 logging.basicConfig(format = '%(asctime)s - %(levelname)s - %(name)s -   %(message)s',
@@ -32,7 +32,7 @@ def main():
     parser = argparse.ArgumentParser(description="Preprocess the data to avoid re-doing it several times by (tokenization + token_to_ids).")
     parser.add_argument('--file_path', type=str, default='data/dump.txt',
                         help='The path to the data.')
-    parser.add_argument('--tokenizer_type', type=str, default='bert', choices=['bert', 'roberta'])
+    parser.add_argument('--tokenizer_type', type=str, default='bert', choices=['bert', 'roberta', 'gpt2'])
     parser.add_argument('--tokenizer_name', type=str, default='bert-base-uncased',
                         help="The tokenizer to use.")
     parser.add_argument('--dump_file', type=str, default='data/dump',
@@ -43,10 +43,16 @@ def main():
     logger.info(f'Loading Tokenizer ({args.tokenizer_name})')
     if args.tokenizer_type == 'bert':
         tokenizer = BertTokenizer.from_pretrained(args.tokenizer_name)
+        bos = tokenizer.special_tokens_map['cls_token'] # `[CLS]`
+        sep = tokenizer.special_tokens_map['sep_token'] # `[SEP]`
     elif args.tokenizer_type == 'roberta':
         tokenizer = RobertaTokenizer.from_pretrained(args.tokenizer_name)
-    bos = tokenizer.special_tokens_map['bos_token'] # `[CLS]` for bert, `<s>` for roberta
-    sep = tokenizer.special_tokens_map['sep_token'] # `[SEP]` for bert, `</s>` for roberta
+        bos = tokenizer.special_tokens_map['cls_token'] # `<s>`
+        sep = tokenizer.special_tokens_map['sep_token'] # `</s>`
+    elif args.tokenizer_type == 'gpt2':
+        tokenizer = GPT2Tokenizer.from_pretrained(args.tokenizer_name)
+        bos = tokenizer.special_tokens_map['bos_token'] # `<|endoftext|>`
+        sep = tokenizer.special_tokens_map['eos_token'] # `<|endoftext|>`    
 
     logger.info(f'Loading text from {args.file_path}')
     with open(args.file_path, 'r', encoding='utf8') as fp: