Created
October 13, 2021 12:04
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Inverse function for torch.nn.utils.rnn.pack_sequence.
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| import torch | |
| from torch.nn.utils.rnn import pack_sequence, pad_packed_sequence | |
| def unpack_sequence(packed_sequences): | |
| """Unpacks PackedSequence into a list of variable length Tensors""" | |
| unpacked_sequences = [] | |
| padded_sequences, lengths = pad_packed_sequence(packed_sequences, batch_first=True) | |
| max_length = padded_sequences.shape[1] | |
| idx = torch.arange(max_length) | |
| for seq, length in zip(padded_sequences, lengths): | |
| mask = idx < length | |
| unpacked_seq = seq[mask] | |
| unpacked_sequences.append(unpacked_seq) | |
| return unpacked_sequences | |
| a = torch.tensor([1,2,3]) | |
| b = torch.tensor([4,5]) | |
| c = torch.tensor([6]) | |
| sequences = [a, b, c] | |
| packed_sequences = pack_sequence(sequences) | |
| unpacked_sequences = unpack_sequence(packed_sequences) | |
| assert all([torch.allclose(a, b) for a, b in zip(sequences, unpacked_sequences)]) |
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