This is longformer-base-4096 model fine-tuned on SQuAD v1 dataset for question answering task.
Longformer model created by Iz Beltagy, Matthew E. Peters, Arman Coha from AllenAI. As the paper explains it
Longformeris a BERT-like model for long documents.
The pre-trained model can handle sequences with upto 4096 tokens.
Few things to keep in mind while training longformer for QA task,
by default longformer uses sliding-window local attention on all tokens. But For QA, all question tokens should have global attention. For more details on this please refer the paper. The
LongformerForQuestionAnswering model automatically does that for you. To allow it to do that
- The input sequence must have three sep tokens, i.e the sequence should be encoded like this
<s> question</s></s> context</s>. If you encode the question and answer as a input pair, then the tokenizer already takes care of that, you shouldn't worry about it.
input_idsshould always be a batch of examples.
import torch from transformers import AutoTokenizer, AutoModelForQuestionAnswering, tokenizer = AutoTokenizer.from_pretrained("valhalla/longformer-base-4096-finetuned-squadv1") model = AutoModelForQuestionAnswering.from_pretrained("valhalla/longformer-base-4096-finetuned-squadv1") text = "Huggingface has democratized NLP. Huge thanks to Huggingface for this." question = "What has Huggingface done ?" encoding = tokenizer(question, text, return_tensors="pt") input_ids = encoding["input_ids"] # default is local attention everywhere # the forward method will automatically set global attention on question tokens attention_mask = encoding["attention_mask"] start_scores, end_scores = model(input_ids, attention_mask=attention_mask) all_tokens = tokenizer.convert_ids_to_tokens(input_ids.tolist()) answer_tokens = all_tokens[torch.argmax(start_scores) :torch.argmax(end_scores)+1] answer = tokenizer.decode(tokenizer.convert_tokens_to_ids(answer_tokens)) # output => democratized NLP
LongformerForQuestionAnswering isn't yet supported in
pipeline . I'll update this card once the support has been added.
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