transformers/docs/source/en/model_doc/dpr.md

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*This model was published in HF papers on 2020-04-10 and contributed to Hugging Face Transformers on 2020-11-16.*

# DPR

<div class="flex flex-wrap space-x-1">
<img alt="SDPA" src="https://img.shields.io/badge/SDPA-DE3412?style=flat&logo=pytorch&logoColor=white">
</div>

## Overview

Dense Passage Retrieval (DPR) is a set of tools and models for state-of-the-art open-domain Q&A research. It was
introduced in [Dense Passage Retrieval for Open-Domain Question Answering](https://huggingface.co/papers/2004.04906) by
Vladimir Karpukhin, Barlas Oğuz, Sewon Min, Patrick Lewis, Ledell Wu, Sergey Edunov, Danqi Chen, Wen-tau Yih.

The abstract from the paper is the following:

*Open-domain question answering relies on efficient passage retrieval to select candidate contexts, where traditional
sparse vector space models, such as TF-IDF or BM25, are the de facto method. In this work, we show that retrieval can
be practically implemented using dense representations alone, where embeddings are learned from a small number of
questions and passages by a simple dual-encoder framework. When evaluated on a wide range of open-domain QA datasets,
our dense retriever outperforms a strong Lucene-BM25 system largely by 9%-19% absolute in terms of top-20 passage
retrieval accuracy, and helps our end-to-end QA system establish new state-of-the-art on multiple open-domain QA
benchmarks.*

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

## Usage tips

- DPR consists in three models:

  * Question encoder: encode questions as vectors
  * Context encoder: encode contexts as vectors
  * Reader: extract the answer of the questions inside retrieved contexts, along with a relevance score (high if the inferred span actually answers the question).

## DPRConfig

[[autodoc]] DPRConfig

## DPRContextEncoderTokenizer

[[autodoc]] DPRContextEncoderTokenizer

## DPRContextEncoderTokenizerFast

[[autodoc]] DPRContextEncoderTokenizerFast

## DPRQuestionEncoderTokenizer

[[autodoc]] DPRQuestionEncoderTokenizer

## DPRQuestionEncoderTokenizerFast

[[autodoc]] DPRQuestionEncoderTokenizerFast

## DPRReaderTokenizer

[[autodoc]] DPRReaderTokenizer

## DPRReaderTokenizerFast

[[autodoc]] DPRReaderTokenizerFast

## DPR specific outputs

[[autodoc]] models.dpr.modeling_dpr.DPRContextEncoderOutput

[[autodoc]] models.dpr.modeling_dpr.DPRQuestionEncoderOutput

[[autodoc]] models.dpr.modeling_dpr.DPRReaderOutput

## DPRContextEncoder

[[autodoc]] DPRContextEncoder
    - forward

## DPRQuestionEncoder

[[autodoc]] DPRQuestionEncoder
    - forward

## DPRReader

[[autodoc]] DPRReader
    - forward