TimeSeriesSeq2Seq

Seq2Seq, Seq2Point modeling implementations using 1D convolution, LSTM, Attention mechanisms, Transformer, and Temporal Fusion Transformer(TFT).
The repo implements the following:

• Basic convolution and LSTM layers implementation
• Bahdanau attention LSTM Encoder-Decoder network by Bahdanau et al.(2014)
• Vanilla Transformer by Vaswani et al.(2017). See architectures.transformer.Transformer.
• Temporal Fusion Transformer by Lim et al.(2020). See architectures.tft.TemporalFusionTransformer.

Transformer-based classes always produce sequence-to-sequence outputs.
RNN-based classes can selectively produce sequence or point outputs:

• Difference between rnn_seq2seq and rnn_seq2point is the decoder part. The former uses autoregressive LSTM decoder to generate sequence of vectors, while the latter uses MLP decoder to generate a single vector.

All network parameters are initialized from $\mathcal{N}\sim(0,0.01^2)$, except for bias initialized from torch.zeros. See architectures.init.

See Tutorial.ipynb for details.

Configuration

Supports $(B,L_{in},C_{in})\xrightarrow{network}(B,L_{out},C_{out})$ operations, where

$$\begin{aligned} B&=\text{batch\_size}\\\ L_{in}&=\text{input\_sequence\_length (variable)}\\\ C_{in}&=\text{input\_feature\_size}\\\ L_{out}&=\text{output\_sequence\_length (variable)}\\\ C_{out}&=\text{output\_feature\_size}\\\ \end{aligned}$$

• hidden_size Hidden state size of LSTM encoder.
• num_layers Number of stacks in CNN, LSTM encoder, LSTM decoder, and FC layers.
• bidirectional Whether to use bidirectional LSTM encoder.
• dropout Dropout rate. Applies to:
  Residual drop path in 1DCNN
  hidden state dropout in LSTM encoder/decoder(for every time step).
  Unlike torch.nn.LSTM, dropout is applied from the first LSTM layer.
• layernorm Layer normalization in LSTM encoder and decoder.
• attention Attention in LSTM decoder.
  Supports 'bahdanau' for Bahdanau style, 'dotproduct' for Dot Product style, and 'none for non-attended decoder.

Creating model instances

from architectures.rnn_seq2seq import *
from architectures.rnn_seq2point import *
from architectures.transformer import *
from architectures.tft import *

# LSTM encoder - LSTM decoder - MLP
seq2seq_lstm = LSTMSeq2Seq(
    Cin, Cout, hidden_size, num_layers, bidirectional, dropout, layernorm, attention
)  

# 1DCNN+LSTM encoder - LSTM decoder
seq2seq_cnnlstm = CNNLSTMSeq2Seq(
    Cin, Cout, hidden_size, num_layers, bidirectional, dropout, layernorm, attention
)

# LSTM encoder - MLP
seq2point_lstm = LSTMSeq2Point(
    Cin, Cout, hidden_size, num_layers, bidirectional, dropout, layernorm
)

# 1DCNN+LSTM encoder - MLP
seq2point_cnnlstm = CNNLSTMSeq2Point(
    Cin, Cout, hidden_size, num_layers, bidirectional, dropout, layernorm
)

# Transformer
seq2seq_transformer = Transformer(
    Cin, Cout, num_layers, n_heads, d_model, dropout, d_ff
)

# Temporal Fusion Transformer
seq2seq_tft = TemporalFusionTransformer(
    Cin, Cout, num_layers, n_heads, d_model, dropout
)

Autoregressive forward operation

• x Input to the network. Supports $(B,L_{in},C_{in})$ only.
• y Output label for teacher forcing. Supports $(B,*,C_{out})$ only. Defaults to None (fully autoregressive).
• teacher_forcing Teacher forcing ratio $\in [0,1]$. Defaults to -1 (fully autoregressive).
• trg_len Target sequence length to generate. Defaults to 1.

If only x and trg_len is given as arguments, the model will autoregressively produce trg_len length of outputs.

Accessing model properties

By inheriting architectures.skeleton.Skeleton, model properties are automatically saved to attributes:

• Parameters can be counted by model.count_params()
• Properties are accessed using model.model_info attribute.
• The identical model instance can be created by ModelClass(**model.model_init_args).

seq2seq_lstm.count_params()

model_info = seq2seq_lstm.model_info
model_init_args = seq2seq_lstm.model_init_args
print(model_info)

another_model_instance = LSTMSeq2Seq(**model_init_args)

Number of trainable parameters: 10422835
{'attention': 'bahdanau', 'bidirectional': True, 'dropout': 0.3, 'hidden_size': 256, 'input_size': 6, 'layernorm': True, 'num_layers': 3, 'output_size': 50}