Source code for textattack.goal_functions.classification.input_reduction

"""

Determine if maintaining the same predicted label
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"""


from .classification_goal_function import ClassificationGoalFunction


[docs]class InputReduction(ClassificationGoalFunction): """Attempts to reduce the input down to as few words as possible while maintaining the same predicted label. From Feng, Wallace, Grissom, Iyyer, Rodriguez, Boyd-Graber. (2018). Pathologies of Neural Models Make Interpretations Difficult. https://arxiv.org/abs/1804.07781 """ def __init__(self, *args, target_num_words=1, **kwargs): self.target_num_words = target_num_words super().__init__(*args, **kwargs) def _is_goal_complete(self, model_output, attacked_text): return ( self.ground_truth_output == model_output.argmax() and attacked_text.num_words <= self.target_num_words ) def _should_skip(self, model_output, attacked_text): return self.ground_truth_output != model_output.argmax() def _get_score(self, model_output, attacked_text): # Give the lowest score possible to inputs which don't maintain the ground truth label. if self.ground_truth_output != model_output.argmax(): return 0 cur_num_words = attacked_text.num_words initial_num_words = self.initial_attacked_text.num_words # The main goal is to reduce the number of words (num_words_score) # Higher model score for the ground truth label is used as a tiebreaker (model_score) num_words_score = max( (initial_num_words - cur_num_words) / initial_num_words, 0 ) model_score = model_output[self.ground_truth_output] return min(num_words_score + model_score / initial_num_words, 1)
[docs] def extra_repr_keys(self): if self.maximizable: return ["maximizable"] else: return ["maximizable", "target_num_words"]