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20 lines
507 B
Python
20 lines
507 B
Python
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from ray.rllib.utils.framework import try_import_torch
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torch, _ = try_import_torch()
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def sequence_mask(lengths, maxlen, dtype=torch.bool):
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"""
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Exact same behavior as tf.sequence_mask.
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Thanks to Dimitris Papatheodorou
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(https://discuss.pytorch.org/t/pytorch-equivalent-for-tf-sequence-mask/39036).
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"""
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if maxlen is None:
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maxlen = lengths.max()
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mask = ~(torch.ones((len(lengths), maxlen)).cumsum(dim=1).t() > lengths).\
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t()
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mask.type(dtype)
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return mask
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