33 lines
1.6 KiB
Python
33 lines
1.6 KiB
Python
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import torch
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from transformers import LogitsWarper
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class TypicalLogitsWarper(LogitsWarper):
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def __init__(self, mass: float = 0.9, filter_value: float = -float("Inf"), min_tokens_to_keep: int = 1):
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self.filter_value = filter_value
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self.mass = mass
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self.min_tokens_to_keep = min_tokens_to_keep
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def __call__(self, input_ids: torch.LongTensor, scores: torch.FloatTensor) -> torch.FloatTensor:
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# calculate entropy
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normalized = torch.nn.functional.log_softmax(scores, dim=-1)
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p = torch.exp(normalized)
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ent = -(normalized * p).nansum(-1, keepdim=True)
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# shift and sort
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shifted_scores = torch.abs((-normalized) - ent)
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sorted_scores, sorted_indices = torch.sort(shifted_scores, descending=False)
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sorted_logits = scores.gather(-1, sorted_indices)
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cumulative_probs = sorted_logits.softmax(dim=-1).cumsum(dim=-1)
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# Remove tokens with cumulative mass above the threshold
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last_ind = (cumulative_probs < self.mass).sum(dim=1)
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last_ind[last_ind < 0] = 0
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sorted_indices_to_remove = sorted_scores > sorted_scores.gather(1, last_ind.view(-1, 1))
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if self.min_tokens_to_keep > 1:
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# Keep at least min_tokens_to_keep (set to min_tokens_to_keep-1 because we add the first one below)
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sorted_indices_to_remove[..., : self.min_tokens_to_keep] = 0
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indices_to_remove = sorted_indices_to_remove.scatter(1, sorted_indices, sorted_indices_to_remove)
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scores = scores.masked_fill(indices_to_remove, self.filter_value)
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return scores
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