Keras implementation of the IndRNN model from the paper Independently Recurrent Neural Network (IndRNN): Building A Longer and Deeper RNN
Usage of IndRNNCells
from ind_rnn import IndRNNCell, RNN
cells = [IndRNNCell(128), IndRNNCell(128)]
ip = Input(...)
x = RNN(cells)(ip)
...
Usage of IndRNN layer
from ind_rnn import IndRNN
ip = Input(...)
x = IndRNN(128)(x)
IndRnn and its associated cell has additional parameters, recurrent_clip_min and recurrent_clip_max which default to -1.
-1 indicates that they should take their default values of [0, 2 ^ (1 / Timesteps)] as the clipping range for ReLU activation. If you change the activation function, do not forget to change the clipping ranges as well, or the model may diverge during training.
In Keras, there is implicit detection of the number of timesteps if the shape is well specified during training. Since this clipping is most important during training (for initialization of weights) and also during inference (for clipping range of the recurrent weights), it is adviseable to always specify the number of time steps, even during inference.
Since it may not be possible to determine the number of timesteps for variable timestep problems, the model defaults to a max clipping range of 1.0, which is equivalent to an infinite timestep problem. This may cause issues if the model was trained using a pre-set timestep.