A confusion about mrc model
# ❓ Questions & Help

- I found all of pretrain models using for mrc use softmax to pred start and end probability. 

- If a paragraph has multi-answers, softmax not worked, otherwise, adding some postprocess to combine start and end probability to sort that we can choose n-best answer, but the numbert is  fixed for all paragaph.
- Squad 2.0 has unanswerable questions and i found  data processor define start index == end index == 0 to handle this situation.
- So my confusion is why not use sigmoid instead of softmax in the last layer, if i use sigmoid, i can deal with muti-answers or non-answer easily....

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