# DPR
## 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://arxiv.org/abs/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
## TFDPRContextEncoder
[[autodoc]] TFDPRContextEncoder
- call
## TFDPRQuestionEncoder
[[autodoc]] TFDPRQuestionEncoder
- call
## TFDPRReader
[[autodoc]] TFDPRReader
- call
