PyTorch SRU

This is just a independently packaged and properly interfaced SRU in PyTorch. The credits for main source code all belong @taolei87 (https://github.com/taolei87/sru).

This main difference between this package and the author's source code is that

• Basic handling for PackedSequence inputs. However, if there are enough demands for it, further optimization code can be implemented to leverage packed data structures in CUDA-level.

• Handling of variable length sequences in a mini-batch. The capability to handle PackedSequence also means that the underlying CUDA-level code must support variable sequence lengths in a mini-batch. Some basic codes have been modified to output only the last hidden state of each sequence (of variable lengths).

We plan to update this package as soon as the author puts out additional functionalities (layer normalization etc.)