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Add support for the null answer in QuestionAnsweringPipeline (#3441)

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* Add support for the null answer in `QuestionAnsweringPipeline`

* black

* Fix min null score computation

* Fix a PR comment
This commit is contained in:
Santiago Castro
2020-04-17 11:17:21 -04:00
committed by GitHub
parent edf0582c0b
commit c19727fd38
1 changed files with 9 additions and 2 deletions
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11
src/transformers/pipelines.py
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@@ -944,6 +944,7 @@ class QuestionAnsweringPipeline(Pipeline):
kwargs.setdefault("max_answer_len", 15) kwargs.setdefault("max_answer_len", 15)
kwargs.setdefault("max_seq_len", 384) kwargs.setdefault("max_seq_len", 384)
kwargs.setdefault("max_question_len", 64) kwargs.setdefault("max_question_len", 64)
kwargs.setdefault("handle_impossible_answer", False)
if kwargs["topk"] < 1: if kwargs["topk"] < 1:
raise ValueError("topk parameter should be >= 1 (got {})".format(kwargs["topk"])) raise ValueError("topk parameter should be >= 1 (got {})".format(kwargs["topk"]))
@@ -982,6 +983,7 @@ class QuestionAnsweringPipeline(Pipeline):
start, end = self.model(**fw_args) start, end = self.model(**fw_args)
start, end = start.cpu().numpy(), end.cpu().numpy() start, end = start.cpu().numpy(), end.cpu().numpy()
min_null_score = 1000000 # large and positive
answers = [] answers = []
for (feature, start_, end_) in zip(features, start, end): for (feature, start_, end_) in zip(features, start, end):
# Normalize logits and spans to retrieve the answer # Normalize logits and spans to retrieve the answer
@@ -994,8 +996,9 @@ class QuestionAnsweringPipeline(Pipeline):
end_ * np.abs(np.array(feature.p_mask) - 1), end_ * np.abs(np.array(feature.p_mask) - 1),
) )
# TODO : What happens if not possible if kwargs["handle_impossible_answer"]:
# Mask CLS min_null_score = min(min_null_score, (start_[0] * end_[0]).item())
start_[0] = end_[0] = 0 start_[0] = end_[0] = 0
starts, ends, scores = self.decode(start_, end_, kwargs["topk"], kwargs["max_answer_len"]) starts, ends, scores = self.decode(start_, end_, kwargs["topk"], kwargs["max_answer_len"])
@@ -1013,6 +1016,10 @@ class QuestionAnsweringPipeline(Pipeline):
} }
for s, e, score in zip(starts, ends, scores) for s, e, score in zip(starts, ends, scores)
] ]
if kwargs["handle_impossible_answer"]:
answers.append({"score": min_null_score, "start": 0, "end": 0, "answer": ""})
answers = sorted(answers, key=lambda x: x["score"], reverse=True)[: kwargs["topk"]] answers = sorted(answers, key=lambda x: x["score"], reverse=True)[: kwargs["topk"]]
all_answers += answers all_answers += answers