readme: ---
  language: en
  license: apache-2.0
  datasets:
  - wiki_dpr
  thumbnail: https://huggingface.co/front/thumbnails/facebook.png
  ---
  ## RAG
  
  This is the RAG-Token Model of the the paper [Retrieval-Augmented Generation for Knowledge-Intensive NLP Tasks](https://arxiv.org/pdf/2005.11401.pdf) 
  by Patrick Lewis, Ethan Perez, Aleksandara Piktus et al.
  
  The model is a *uncased* model, which means that capital letters are simply converted to lower-case letters.
  
  The model consits of a *question_encoder*, *retriever* and a *generator*. The retriever extracts relevant passages from the *wiki_dpr* `train` datasets, which is linked above.
  The question_encoder and retriever are based on `facebook/dpr-question_encoder-single-nq-base` and `facebook/bart-large`, which were jointly finetuned on 
  on the *wiki_dpr* QA dataset in an end-to-end fashion.
  
  ## Usage:
  
  **Note**: In the usage example below only the *dummy* retriever of *wiki_dpr* is used because the complete *lecagy* index requires over 75 GB of RAM.
  The model can generate answers to any factoid question as follows:
  
  ```python
  from transformers import RagTokenizer, RagRetriever, RagTokenForGeneration
  
  tokenizer = RagTokenizer.from_pretrained("facebook/rag-token-nq")
  retriever = RagRetriever.from_pretrained("facebook/rag-token-nq", index_name="exact", use_dummy_dataset=True)
  model = RagTokenForGeneration.from_pretrained("facebook/rag-token-nq", retriever=retriever)
  
  input_dict = tokenizer.prepare_seq2seq_batch("who holds the record in 100m freestyle", return_tensors="pt") 
  
  generated = model.generate(input_ids=input_dict["input_ids"]) 
  print(tokenizer.batch_decode(generated, skip_special_tokens=True)[0]) 
  
  # should give michael phelps => sounds reasonable
  ```
  