tfm.nlp.layers.TransformerDecoderBlock

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Single transformer layer for decoder.

tfm.nlp.layers.TransformerDecoderBlock(
    num_attention_heads,
    intermediate_size,
    intermediate_activation,
    dropout_rate=0.0,
    attention_dropout_rate=0.0,
    multi_channel_cross_attention=False,
    kernel_initializer='glorot_uniform',
    bias_initializer='zeros',
    kernel_regularizer=None,
    bias_regularizer=None,
    activity_regularizer=None,
    kernel_constraint=None,
    bias_constraint=None,
    use_bias=True,
    norm_first=False,
    norm_epsilon=1e-12,
    intermediate_dropout=0.0,
    attention_initializer=None,
    **kwargs
)

It has three sub-layers: (1) a multi-head self-attention mechanism. (2) a encoder-decoder attention. (3) a positionwise fully connected feed-forward network.

num_attention_heads Number of attention heads.
intermediate_size Size of the intermediate layer.
intermediate_activation Activation for the intermediate layer.
dropout_rate Dropout probability for the post-attention and output dropout.
attention_dropout_rate Dropout probability for within the attention layer.
multi_channel_cross_attention Whether to use MultiChannelAttention for cross-attention between target sequences and source sequences.
kernel_initializer Initializer for dense layer kernels.
bias_initializer Initializer for dense layer biases.
kernel_regularizer Regularizer for dense layer kernels.
bias_regularizer Regularizer for dense layer biases.
activity_regularizer Regularizer for dense layer activity.
kernel_constraint Constraint for dense layer kernels.
bias_constraint Constraint for dense layer kernels.
use_bias Whether to enable use_bias in attention layer. If set False, use_bias in attention layer is disabled.
norm_first Whether to normalize inputs to attention and intermediate dense layers. If set False, output of attention and intermediate dense layers is normalized.
norm_epsilon Epsilon value to initialize normalization layers.
intermediate_dropout Dropout probability for intermediate_dropout_layer.
attention_initializer Initializer for kernels of attention layers. If set None, attention layers use kernel_initializer as initializer for kernel.

Methods

call

View source

call(
    inputs, cache=None, decode_loop_step=None
)

This is where the layer's logic lives.

The call() method may not create state (except in its first invocation, wrapping the creation of variables or other resources in tf.init_scope()). It is recommended to create state, including tf.Variable instances and nested Layer instances, in __init__(), or in the build() method that is called automatically before call() executes for the first time.

Args
inputs Input tensor, or dict/list/tuple of input tensors. The first positional inputs argument is subject to special rules:

  • inputs must be explicitly passed. A layer cannot have zero arguments, and inputs cannot be provided via the default value of a keyword argument.
  • NumPy array or Python scalar values in inputs get cast as tensors.
  • Keras mask metadata is only collected from inputs.
  • Layers are built (build(input_shape) method) using shape info from inputs only.
  • input_spec compatibility is only checked against inputs.
  • Mixed precision input casting is only applied to inputs. If a layer has tensor arguments in *args or **kwargs, their casting behavior in mixed precision should be handled manually.
  • The SavedModel input specification is generated using inputs only.
  • Integration with various ecosystem packages like TFMOT, TFLite, TF.js, etc is only supported for inputs and not for tensors in positional and keyword arguments.
*args Additional positional arguments. May contain tensors, although this is not recommended, for the reasons above.
**kwargs Additional keyword arguments. May contain tensors, although this is not recommended, for the reasons above. The following optional keyword arguments are reserved:
  • training: Boolean scalar tensor of Python boolean indicating whether the call is meant for training or inference.
  • mask: Boolean input mask. If the layer's call() method takes a mask argument, its default value will be set to the mask generated for inputs by the previous layer (if input did come from a layer that generated a corresponding mask, i.e. if it came from a Keras layer with masking support).

    • Returns
    A tensor or list/tuple of tensors.

    common_layers_with_encoder

    View source

    common_layers_with_encoder()

    Gets layer objects that can make a Transformer encoder block.