<!--Copyright 2020 The HuggingFace Team. All rights reserved.

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.
-->

# XLM

## Overview

The XLM model was proposed in [Cross-lingual Language Model Pretraining](https://arxiv.org/abs/1901.07291) by
Guillaume Lample, Alexis Conneau. It's a transformer pretrained using one of the following objectives:

- a causal language modeling (CLM) objective (next token prediction),
- a masked language modeling (MLM) objective (BERT-like), or
- a Translation Language Modeling (TLM) object (extension of BERT's MLM to multiple language inputs)

The abstract from the paper is the following:

*Recent studies have demonstrated the efficiency of generative pretraining for English natural language understanding.
In this work, we extend this approach to multiple languages and show the effectiveness of cross-lingual pretraining. We
propose two methods to learn cross-lingual language models (XLMs): one unsupervised that only relies on monolingual
data, and one supervised that leverages parallel data with a new cross-lingual language model objective. We obtain
state-of-the-art results on cross-lingual classification, unsupervised and supervised machine translation. On XNLI, our
approach pushes the state of the art by an absolute gain of 4.9% accuracy. On unsupervised machine translation, we
obtain 34.3 BLEU on WMT'16 German-English, improving the previous state of the art by more than 9 BLEU. On supervised
machine translation, we obtain a new state of the art of 38.5 BLEU on WMT'16 Romanian-English, outperforming the
previous best approach by more than 4 BLEU. Our code and pretrained models will be made publicly available.*

Tips:

- XLM has many different checkpoints, which were trained using different objectives: CLM, MLM or TLM. Make sure to
  select the correct objective for your task (e.g. MLM checkpoints are not suitable for generation).
- XLM has multilingual checkpoints which leverage a specific `lang` parameter. Check out the [multi-lingual](../multilingual) page for more information.

This model was contributed by [thomwolf](https://huggingface.co/thomwolf). The original code can be found [here](https://github.com/facebookresearch/XLM/).


## XLMConfig

[[autodoc]] XLMConfig

## XLMTokenizer

[[autodoc]] XLMTokenizer
    - build_inputs_with_special_tokens
    - get_special_tokens_mask
    - create_token_type_ids_from_sequences
    - save_vocabulary

## XLM specific outputs

[[autodoc]] models.xlm.modeling_xlm.XLMForQuestionAnsweringOutput

## XLMModel

[[autodoc]] XLMModel
    - forward

## XLMWithLMHeadModel

[[autodoc]] XLMWithLMHeadModel
    - forward

## XLMForSequenceClassification

[[autodoc]] XLMForSequenceClassification
    - forward

## XLMForMultipleChoice

[[autodoc]] XLMForMultipleChoice
    - forward

## XLMForTokenClassification

[[autodoc]] XLMForTokenClassification
    - forward

## XLMForQuestionAnsweringSimple

[[autodoc]] XLMForQuestionAnsweringSimple
    - forward

## XLMForQuestionAnswering

[[autodoc]] XLMForQuestionAnswering
    - forward

## TFXLMModel

[[autodoc]] TFXLMModel
    - call

## TFXLMWithLMHeadModel

[[autodoc]] TFXLMWithLMHeadModel
    - call

## TFXLMForSequenceClassification

[[autodoc]] TFXLMForSequenceClassification
    - call

## TFXLMForMultipleChoice

[[autodoc]] TFXLMForMultipleChoice
    - call

## TFXLMForTokenClassification

[[autodoc]] TFXLMForTokenClassification
    - call

## TFXLMForQuestionAnsweringSimple

[[autodoc]] TFXLMForQuestionAnsweringSimple
    - call