33 lines
1.1 KiB
Python
33 lines
1.1 KiB
Python
# Copyright (c) 2021 Binbin Zhang
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#
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# Licensed under the Apache License, Version 2.0 (the "License");
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# you may not use this file except in compliance with the License.
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# You may obtain a copy of the License at
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#
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# http://www.apache.org/licenses/LICENSE-2.0
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#
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# Unless required by applicable law or agreed to in writing, software
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# distributed under the License is distributed on an "AS IS" BASIS,
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# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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# See the License for the specific language governing permissions and
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# limitations under the License.
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import torch
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def padding_mask(lengths: torch.Tensor) -> torch.Tensor:
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"""
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Examples:
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>>> lengths = torch.tensor([2, 2, 3], dtype=torch.int32)
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>>> mask = padding_mask(lengths)
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>>> print(mask)
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tensor([[False, False, True],
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[False, False, True],
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[False, False, False]])
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"""
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batch_size = lengths.size(0)
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max_len = int(lengths.max().item())
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seq = torch.arange(max_len, dtype=torch.int64, device=lengths.device)
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seq = seq.expand(batch_size, max_len)
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return seq >= lengths.unsqueeze(1)
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