.. _pytorch-ops-torch.nn.transformer-decoder:

modelzoo.common.pytorch.layers.TransformerDecoder
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import path: ``modelzoo.common.pytorch.layers.TransformerDecoder``

TransformerDecoder (decoder_layer, num_layers, norm=None):

- **decoder_layer**: an instance of the TransformerDecoderLayer() class (required).

- **num_layers**: the number of sub-decoder-layers in the decoder (required).

- **norm**: the layer normalization component (optional).

**forward** (tgt=None, memory=None, tgt_mask=None, memory_mask=None, tgt_key_padding_mask=None, memory_key_padding_mask=None, rotary_position_embedding_helper=None):

- **tgt**: the sequence to the decoder (required). shape ``[batch_size, tgt_seq_length, embed_dim]``.

- **memory**: the sequence from the last layer of the encoder (optional). shape ``[batch_size, memory_length, embed_dim]``.

- **tgt_mask**: the mask for the tgt sequence (optional). shape ``[tgt_seq_length, tgt_seq_length]``.

- **memory_mask**: the mask for the memory sequence (optional). shape ``[memory_length, src_seq_length]``.

- **tgt_key_padding_mask**: the mask for the tgt keys per batch (optional). shape ``[batch_size, tgt_seq_length]``.

- **memory_key_padding_mask**: the mask for the memory keys per batch (optional). shape ``[batch_size, memory_length]``.

- **rotary_position_embedding_helper** (RotaryPositionEmbeddingHelper): Helper to create rotary embeddings according to the paper `RoFormer: Enhanced Transformer with Rotary Position Embedding <https://arxiv.org/abs/2104.09864>`_