LSTMCell

Versioned name: LSTMCell-1

Category: Sequence processing

Short description: LSTMCell operation represents a single LSTM cell. It computes the output using the formula described in the original paper Long Short-Term Memory.

Detailed description

Formula:
  *  - matrix mult
 (.) - eltwise mult
 [,] - concatenation
sigm - 1/(1 + e^{-x})
tanh - (e^{2x} - 1)/(e^{2x} + 1)
   f = sigm(Wf*[Hi, X] + Bf)
   i = sigm(Wi*[Hi, X] + Bi)
   c = tanh(Wc*[Hi, X] + Bc)
   o = sigm(Wo*[Hi, X] + Bo)
  Co = f (.) Ci + i (.) c
  Ho = o (.) tanh(Co)

Attributes

• hidden_size
  • Description: hidden_size specifies hidden state size.
  • Range of values: a positive integer
  • Type: int
  • Default value: None
  • Required: yes
• activations
  • Description: activations specifies activation functions for gates, there are three gates, so three activation functions should be specified as a value for this attributes
  • Range of values: any combination of relu, sigmoid, tanh
  • Type: a list of strings
  • Default value: sigmoid,tanh,tanh
  • Required: no
• activations_alpha, activations_beta
  • Description: activations_alpha, activations_beta attributes of functions; applicability and meaning of these attributes depends on chosen activation functions
  • Range of values: a list of floating-point numbers
  • Type: float[]
  • Default value: None
  • Required: no
• clip
  • Description: clip specifies bound values [-C, C] for tensor clipping. Clipping is performed before activations.
  • Range of values: a positive floating-point number
  • Type: float
  • Default value: infinity that means that the clipping is not applied
  • Required: no

Inputs

• 1: X - 2D tensor of type T [batch_size, input_size], input data. Required.
• 2: initial_hidden_state - 2D tensor of type T [batch_size, hidden_size]. Required.
• 3: initial_cell_state - 2D tensor of type T [batch_size, hidden_size]. Required.
• 4: W - 2D tensor of type T [4 * hidden_size, input_size], the weights for matrix multiplication, gate order: fico. Required.
• 5: R - 2D tensor of type T [4 * hidden_size, hidden_size], the recurrence weights for matrix multiplication, gate order: fico. Required.
• 6: B 1D tensor of type T [4 * hidden_size], the sum of biases (weights and recurrence weights). Required.

Outputs

• 1: Ho - 2D tensor of type T [batch_size, hidden_size], the last output value of hidden state.
• 2: Co - 2D tensor of type T [batch_size, hidden_size], the last output value of cell state.

Types

• T: any supported floating point type.

Example

<layer ... type="LSTMCell" ...>
    <data hidden_size="128"/>
    <input>
        <port id="0">
            <dim>1</dim>
            <dim>16</dim>
        </port>
        <port id="1">
            <dim>1</dim>
            <dim>128</dim>
        </port>
        <port id="2">
            <dim>1</dim>
            <dim>128</dim>
        </port>
         <port id="3">
            <dim>512</dim>
            <dim>16</dim>
        </port>
         <port id="4">
            <dim>512</dim>
            <dim>128</dim>
        </port>
         <port id="5">
            <dim>512</dim>
        </port>
    </input>
    <output>
        <port id="6">
            <dim>1</dim>
            <dim>128</dim>
        </port>
        <port id="7">
            <dim>1</dim>
            <dim>128</dim>
        </port>
    </output>
</layer>