RuntimeError: ‘lengths’ argument should be a 1D CPU int64 tensor, but got 1D cuda:0 Long tensor

I just had this problem yesterday, in my case the rnn pad sequences wants length to be on the cpu, so just put the lengths to CPU in your function call like this:

packed_sequences = nn.utils.rnn.pack_padded_sequence(padded_tensor, valid_frames.to('cpu'), batch_first=True, enforce_sorted=True) 

This might not be the exact function you're using but I think it will apply to most of the rnn utils functions.