# MobileBERT

## Overview

The MobileBERT model was proposed in [MobileBERT: a Compact Task-Agnostic BERT for Resource-Limited Devices](https://arxiv.org/abs/2004.02984) by Zhiqing Sun, Hongkun Yu, Xiaodan Song, Renjie Liu, Yiming Yang, and Denny

Zhou. It's a bidirectional transformer based on the BERT model, which is compressed and accelerated using several

approaches.

The abstract from the paper is the following:

*Natural Language Processing (NLP) has recently achieved great success by using huge pre-trained models with hundreds

of millions of parameters. However, these models suffer from heavy model sizes and high latency such that they cannot

be deployed to resource-limited mobile devices. In this paper, we propose MobileBERT for compressing and accelerating

the popular BERT model. Like the original BERT, MobileBERT is task-agnostic, that is, it can be generically applied to

various downstream NLP tasks via simple fine-tuning. Basically, MobileBERT is a thin version of BERT_LARGE, while

equipped with bottleneck structures and a carefully designed balance between self-attentions and feed-forward networks.

To train MobileBERT, we first train a specially designed teacher model, an inverted-bottleneck incorporated BERT_LARGE

model. Then, we conduct knowledge transfer from this teacher to MobileBERT. Empirical studies show that MobileBERT is

4.3x smaller and 5.5x faster than BERT_BASE while achieving competitive results on well-known benchmarks. On the

natural language inference tasks of GLUE, MobileBERT achieves a GLUEscore o 77.7 (0.6 lower than BERT_BASE), and 62 ms

latency on a Pixel 4 phone. On the SQuAD v1.1/v2.0 question answering task, MobileBERT achieves a dev F1 score of

90.0/79.2 (1.5/2.1 higher than BERT_BASE).*

This model was contributed by [vshampor](https://huggingface.co/vshampor). The original code can be found [here](https://github.com/google-research/google-research/tree/master/mobilebert).

## Usage tips

- MobileBERT is a model with absolute position embeddings so it's usually advised to pad the inputs on the right rather

  than the left.

- MobileBERT is similar to BERT and therefore relies on the masked language modeling (MLM) objective. It is therefore

  efficient at predicting masked tokens and at NLU in general, but is not optimal for text generation. Models trained

  with a causal language modeling (CLM) objective are better in that regard.

## Resources

- [Text classification task guide](../tasks/sequence_classification)

- [Token classification task guide](../tasks/token_classification)

- [Question answering task guide](../tasks/question_answering)

- [Masked language modeling task guide](../tasks/masked_language_modeling)

- [Multiple choice task guide](../tasks/multiple_choice)

## MobileBertConfig

[[autodoc]] MobileBertConfig

## MobileBertTokenizer

[[autodoc]] MobileBertTokenizer

## MobileBertTokenizerFast

[[autodoc]] MobileBertTokenizerFast

## MobileBert specific outputs

[[autodoc]] models.mobilebert.modeling_mobilebert.MobileBertForPreTrainingOutput

[[autodoc]] models.mobilebert.modeling_tf_mobilebert.TFMobileBertForPreTrainingOutput

## MobileBertModel

[[autodoc]] MobileBertModel

    - forward

## MobileBertForPreTraining

[[autodoc]] MobileBertForPreTraining

    - forward

## MobileBertForMaskedLM

[[autodoc]] MobileBertForMaskedLM

    - forward

## MobileBertForNextSentencePrediction

[[autodoc]] MobileBertForNextSentencePrediction

    - forward

## MobileBertForSequenceClassification

[[autodoc]] MobileBertForSequenceClassification

    - forward

## MobileBertForMultipleChoice

[[autodoc]] MobileBertForMultipleChoice

    - forward

## MobileBertForTokenClassification

[[autodoc]] MobileBertForTokenClassification

    - forward

## MobileBertForQuestionAnswering

[[autodoc]] MobileBertForQuestionAnswering

    - forward

## TFMobileBertModel

[[autodoc]] TFMobileBertModel

    - call

## TFMobileBertForPreTraining

[[autodoc]] TFMobileBertForPreTraining

    - call

## TFMobileBertForMaskedLM

[[autodoc]] TFMobileBertForMaskedLM

    - call

## TFMobileBertForNextSentencePrediction

[[autodoc]] TFMobileBertForNextSentencePrediction

    - call

## TFMobileBertForSequenceClassification

[[autodoc]] TFMobileBertForSequenceClassification

    - call

## TFMobileBertForMultipleChoice

[[autodoc]] TFMobileBertForMultipleChoice

    - call

## TFMobileBertForTokenClassification

[[autodoc]] TFMobileBertForTokenClassification

    - call

## TFMobileBertForQuestionAnswering

[[autodoc]] TFMobileBertForQuestionAnswering

    - call