TransformerDecoder

class torch.nn.TransformerDecoder(decoder_layer, num_layers, norm=None)

TransformerDecoder is a stack of N decoder layers.

Parameters

• decoder_layer (TransformerDecoderLayer) – an instance of the TransformerDecoderLayer() class (required).

• num_layers (int) – the number of sub-decoder-layers in the decoder (required).

• norm (Optional[Module]) – the layer normalization component (optional).

Examples::

>>> decoder_layer = nn.TransformerDecoderLayer(d_model=512, nhead=8)
>>> transformer_decoder = nn.TransformerDecoder(decoder_layer, num_layers=6)
>>> memory = torch.rand(10, 32, 512)
>>> tgt = torch.rand(20, 32, 512)
>>> out = transformer_decoder(tgt, memory)

forward(tgt, memory, tgt_mask=None, memory_mask=None, tgt_key_padding_mask=None, memory_key_padding_mask=None, tgt_is_causal=None, memory_is_causal=False)

Pass the inputs (and mask) through the decoder layer in turn.

Parameters

• tgt (Tensor) – the sequence to the decoder (required).

• memory (Tensor) – the sequence from the last layer of the encoder (required).

• tgt_mask (Optional[Tensor]) – the mask for the tgt sequence (optional).

• memory_mask (Optional[Tensor]) – the mask for the memory sequence (optional).

• tgt_key_padding_mask (Optional[Tensor]) – the mask for the tgt keys per batch (optional).

• memory_key_padding_mask (Optional[Tensor]) – the mask for the memory keys per batch (optional).

• tgt_is_causal (Optional[bool]) – If specified, applies a causal mask as tgt mask. Default: None; try to detect a causal mask. Warning: tgt_is_causal provides a hint that tgt_mask is the causal mask. Providing incorrect hints can result in incorrect execution, including forward and backward compatibility.

• memory_is_causal (bool) – If specified, applies a causal mask as memory mask. Default: False. Warning: memory_is_causal provides a hint that memory_mask is the causal mask. Providing incorrect hints can result in incorrect execution, including forward and backward compatibility.

Return type

Tensor

Shape:

see the docs in Transformer.