FastGRNNCell

FastGRNNCell(input_size => hidden_size, [activation];
    init_kernel = glorot_uniform,
    init_recurrent_kernel = glorot_uniform,
    bias = true, recurrent_bias = true, alt_bias=true,
    independent_recurrence = false, integration_mode = :addition)

Fast gated recurrent neural network cell (Kusupati et al., 2018). See FastGRNN for a layer that processes entire sequences.

Arguments

• input_size => hidden_size: input and inner dimension of the layer.
• activation: the activation function, defaults to tanh_fast.

Keyword arguments

• init_kernel: initializer for the input to hidden weights. Default is glorot_uniform.
• init_recurrent_kernel: initializer for the hidden to hidden weights. Default is glorot_uniform.
• init_zeta: Initializer for the zeta parameter. Default is 1.0.
• init_nu: Initializer for the nu parameter. Default is - 4.0.
• bias: include input to recurrent bias or not. Default is true.
• recurrent_bias: include recurrent to recurrent bias or not. Default is true.
• alt_bias: include different bias for the two gates. Default is true
• independent_recurrence: flag to toggle independent recurrence. If true, the recurrent to recurrent weights are a vector instead of a matrix. Default false.
• integration_mode: determines how the input and hidden projections are combined. The options are :addition and :multiplicative_integration. Defaults to :addition.

Equations

\[\begin{aligned} \mathbf{z}(t) &= \sigma\left( \mathbf{W}^{z}_{ih} \mathbf{x}(t) + \mathbf{W}^{z}_{hh} \mathbf{h}(t-1) + \mathbf{b}^{z} \right), \\ \tilde{\mathbf{h}}(t) &= \tanh\left( \mathbf{W}^{h}_{ih} \mathbf{x}(t) + \mathbf{W}^{h}_{hh} \mathbf{h}(t-1) + \mathbf{b}^{h} \right), \\ \mathbf{h}(t) &= \left( \left( \sigma(\zeta) (1 - \mathbf{z}(t)) + 'sigma(\nu) \right) \odot \tilde{\mathbf{h}}(t) \right) + \mathbf{z}(t) \odot \mathbf{h}(t-1) \end{aligned}\]

Forward

fastgrnncell(inp, state)
fastgrnncell(inp)

Arguments

• inp: The input to the fastgrnncell. It should be a vector of size input_size or a matrix of size input_size x batch_size.
• state: The hidden state of the FastGRNN. It should be a vector of size hidden_size or a matrix of size hidden_size x batch_size. If not provided, it is assumed to be a vector of zeros, initialized by Flux.initialstates.

Returns

• A tuple (output, state), where both elements are given by the updated state new_state, a tensor of size hidden_size or hidden_size x batch_size.