LSTM Layer

Specify the name of a workspace variable that contains an lstmLayer object from a trained network. The LSTM Layer block configures itself by using the properties of the object and calculates the block output by using the learnable parameters of the object.

Programmatic Use

Data format for the input data. The options use the same notation as the fmt argument of the dlarray object, except layer blocks do not support the Batch (B) dimension and instead assume an observation number of 1.

Programmatic Use

Whether to use stateful prediction, specified as a boolean. If true, the block maintains the cell state and hidden state between time steps. If false, the block performs stateless prediction by resetting cell states and hidden states to their initial values at the beginning of each time step. Use stateless prediction for frame-based processing where Simulink step time represents frame period and the network processes multiple samples at each time step. For more information, see Sample- and Frame-Based Concepts (DSP System Toolbox).

Programmatic Use

If the object that you pass as the value of the Layer parameter uses the tanh state activation function or the sigmoid gate activation function, then the block uses the approximation method that you specify to compute the layer output.

For more information about the CORDIC approximation method, see cordictanh (Fixed-Point Designer).

Programmatic Use

Lower value of the output range that the software checks.

The software uses the minimum to perform:

Tips

Output minimum does not saturate or clip the actual output signal. Use the Saturation (Simulink) block instead.

Dependencies

To enable this parameter, set Output data type to a value other than Inherit: Inherit via internal rule.

Programmatic Use

To set the block parameter value programmatically, use the set_param (Simulink) function.

Upper value of the output range that the software checks.

The software uses the maximum value to perform:

Tips

Output maximum does not saturate or clip the actual output signal. Use the Saturation (Simulink) block instead.

Dependencies

To enable this parameter, set Output data type to a value other than Inherit: Inherit via internal rule.

Programmatic Use

To set the block parameter value programmatically, use the set_param (Simulink) function.

Choose the data type for the output. The type can be inherited, specified directly, or expressed as a data type object such as Simulink.NumericType. When you choose Inherit: Inherit via internal rule, Simulinksets the output data type to the same type as the hidden state.

Programmatic Use

To set the block parameter value programmatically, use the set_param (Simulink) function.

Select this parameter to prevent the fixed-point tools from overriding the Output data type you specify on the block. For more information, see Use Lock Output Data Type Setting (Fixed-Point Designer).

Programmatic Use

To set the block parameter value programmatically, use the set_param (Simulink) function.

Specify the rounding mode for fixed-point operations. For more information, see Rounding Modes (Fixed-Point Designer).

Block parameters always round to the nearest representable value. To control the rounding of a block parameter, enter an expression using a MATLAB^® rounding function into the mask field.

Programmatic Use

To set the block parameter value programmatically, use the set_param (Simulink) function.

Specify whether overflows saturate or wrap.

For example, the maximum value that the signed 8-bit integer int8 can represent is 127. Any block operation result greater than this maximum value causes overflow of the 8-bit integer.

Tips

Programmatic Use

To set the block parameter value programmatically, use the set_param (Simulink) function.

The block casts the value of the InputWeights property of the object that you specify with the Layer parameter to this data type. The type can be inherited, specified directly, or expressed as a data type object such as Simulink.NumericType.

Programmatic Use

To set the block parameter value programmatically, use the set_param (Simulink) function.

The block casts the value of the RecurrentWeights property of the object that you specify with the Layer parameter to this data type. The type can be inherited, specified directly, or expressed as a data type object such as Simulink.NumericType.

Programmatic Use

To set the block parameter value programmatically, use the set_param (Simulink) function.

The block casts the value of the Bias property of the object that you specify with the Layer parameter to this data type. The type can be inherited, specified directly, or expressed as a data type object such as Simulink.NumericType.

Programmatic Use

To set the block parameter value programmatically, use the set_param (Simulink) function.

The block casts the value of the CellState property of the object that you specify with the Layer parameter to this data type. The type can be inherited, specified directly, or expressed as a data type object such as Simulink.NumericType.

This parameter affects only the initial cell state, c₀. To cast later cell state values, use the Cell state parameter. For more information, see Long Short-Term Memory Layer.

Programmatic Use

To set the block parameter value programmatically, use the set_param (Simulink) function.

Choose the data type for the output of the Sum block ForIteratorSubsystem/LSTMCore/CellAdd inside the LSTM Layer block. The type can be inherited, specified directly, or expressed as a data type object such as Simulink.NumericType. When you choose Inherit: Inherit via internal rule, Simulink chooses a data type to balance numerical accuracy, performance, and generated code size, while taking into account the properties of the embedded target hardware.

For a time step t, the Sum block computes the cell state c_t as c_t=f_t⊙c_t-1+i_t⊙g_t, where i, f, and g denote the input gate, forget gate, and cell candidate gate, respectively, and ⊙ denotes the Hadamard product (element-wise multiplication of vectors). For more information, see Long Short-Term Memory Layer.

Programmatic Use

To set the block parameter value programmatically, use the set_param (Simulink) function.

The block casts the value of the HiddenState property of the object that you specify with the Layer parameter to this data type. The type can be inherited, specified directly, or expressed as a data type object such as Simulink.NumericType.

This parameter affects only the initial hidden state, h₀. To cast later hidden state values, use the Hidden state parameter. For more information, see Long Short-Term Memory Layer.

Programmatic Use

To set the block parameter value programmatically, use the set_param (Simulink) function.

Choose the data type for the output of the Product block ForIteratorSubsystem/LSTMCore/HiddenStateProduct inside the LSTM Layer block. The type can be inherited, specified directly, or expressed as a data type object such as Simulink.NumericType. When you choose Inherit: Inherit via internal rule, Simulink chooses a data type to balance numerical accuracy, performance, and generated code size, while taking into account the properties of the embedded target hardware.

For a time step t, the Product block computes the hidden state h_t as h_t=o_t⊙σ_c(c_t), where o denotes the output gate, σ_c denotes the state activation function, ⊙ denotes the Hadamard product (element-wise multiplication of vectors), and c_t denotes the cell state at the time step. For more information, see Long Short-Term Memory Layer.

Programmatic Use

To set the block parameter value programmatically, use the set_param (Simulink) function.

Choose the data type for the output of the Product block InputWeightsMatrixMultiply/W*x inside the LSTM Layer block. The type can be inherited, specified directly, or expressed as a data type object such as Simulink.NumericType. When you choose Inherit: Inherit via internal rule, Simulink chooses a data type to balance numerical accuracy, performance, and generated code size, while taking into account the properties of the embedded target hardware.

For a time step t, the Product block computes the product of the input weights (W) and the input at the time step (x_t). For more information, see Long Short-Term Memory Layer.

Programmatic Use

To set the block parameter value programmatically, use the set_param (Simulink) function.

Choose the data type for the output of the Product block ForIteratorSubsystem/LSTMCore/RecurrentWeightsMatrixMultiply/R*h_t-1 inside the LSTM Layer block. The type can be inherited, specified directly, or expressed as a data type object such as Simulink.NumericType. When you choose Inherit: Inherit via internal rule, Simulink chooses a data type to balance numerical accuracy, performance, and generated code size, while taking into account the properties of the embedded target hardware.

For a time step t, the Product block computes the product of the recurrent weights (R) and the hidden state at the previous time step (h_t-1). For more information, see Long Short-Term Memory Layer.

Programmatic Use

To set the block parameter value programmatically, use the set_param (Simulink) function.

Choose the data type for the accumulator of the Sum block ForIteratorSubsystem/LSTMCore/LinearGateAdd/Wx+Rh+b inside the LSTM Layer block. The type can be inherited, specified directly, or expressed as a data type object such as Simulink.NumericType. When you choose Inherit: Inherit via internal rule, Simulink chooses a data type to balance numerical accuracy, performance, and generated code size, while taking into account the properties of the embedded target hardware.

For a time step t, Sum block computes the sum Wx_t+Rh_t-1+b, where W denotes the input weights, x_t denotes the input at the time step, h_t-1 denotes the hidden state at the previous time step, and b denotes the bias. For more information, see Long Short-Term Memory Layer.

Programmatic Use

To set the block parameter value programmatically, use the set_param (Simulink) function.

Choose the data type for the output of the Sum block ForIteratorSubsystem/LSTMCore/LinearGateAdd/Wx+Rh+b inside the LSTM Layer block. The type can be inherited, specified directly, or expressed as a data type object such as Simulink.NumericType. When you choose Inherit: Inherit via internal rule, Simulink chooses a data type to balance numerical accuracy, performance, and generated code size, while taking into account the properties of the embedded target hardware.

For a time step t, Sum block computes the sum Wx_t+Rh_t-1+b, where W denotes the input weights, x_t denotes the input at the time step, h_t-1 denotes the hidden state at the previous time step, and b denotes the bias. For more information, see Long Short-Term Memory Layer.

Programmatic Use

To set the block parameter value programmatically, use the set_param (Simulink) function.

Choose the data type for the output of the Product blocks ForIteratorSubsystem/LSTMCore/f*c_t-1 and ForIteratorSubsystem/LSTMCore/i*g inside the LSTM Layer block. The type can be inherited, specified directly, or expressed as a data type object such as Simulink.NumericType. When you choose Inherit: Inherit via internal rule, Simulink chooses a data type to balance numerical accuracy, performance, and generated code size, while taking into account the properties of the embedded target hardware.

For a time step t, the Product blocks compute the Hadamard products (element-wise multiplication of vectors, denoted as ⊙) f_t⊙c_t-1 and i_t⊙g_t, where f denotes the forget gate, c denotes the cell state, i denotes the input gate, and g denotes the cell candidate. For more information, see Long Short-Term Memory Layer.

Programmatic Use

To set the block parameter value programmatically, use the set_param (Simulink) function.

Choose the data type for the accumulator of the Sum block ForIteratorSubsystem/LSTMCore/CellAdd inside the LSTM Layer block. The type can be inherited, specified directly, or expressed as a data type object such as Simulink.NumericType. When you choose Inherit: Inherit via internal rule, Simulink chooses a data type to balance numerical accuracy, performance, and generated code size, while taking into account the properties of the embedded target hardware.

For a time step t, the Sum block computes the cell state c_t asc_t=f_t⊙c_t-1+i_t⊙g_t,

where i, f, and g denote the input gate, forget gate, and cell candidate gate, respectively, and ⊙ denotes the Hadamard product (element-wise multiplication of vectors). For more information, see Long Short-Term Memory Layer.

Programmatic Use

To set the block parameter value programmatically, use the set_param (Simulink) function.

Specify the discrete interval between sample time hits or specify another type of sample time, such as continuous (0) or inherited (-1). For more options, see Types of Sample Time (Simulink).

By default, the block inherits its sample time based upon the context of the block within the model.

Programmatic Use