Source code for torch.nn.modules.transformer
import copy
from typing import Optional, Any, Union, Callable
import torch
from torch import Tensor
from .. import functional as F
from .module import Module
from .activation import MultiheadAttention
from .container import ModuleList
from ..init import xavier_uniform_
from .dropout import Dropout
from .linear import Linear
from .normalization import LayerNorm
[docs]class Transformer(Module):
r"""A transformer model. User is able to modify the attributes as needed. The architecture
is based on the paper "Attention Is All You Need". Ashish Vaswani, Noam Shazeer,
Niki Parmar, Jakob Uszkoreit, Llion Jones, Aidan N Gomez, Lukasz Kaiser, and
Illia Polosukhin. 2017. Attention is all you need. In Advances in Neural Information
Processing Systems, pages 6000-6010. Users can build the BERT(https://arxiv.org/abs/1810.04805)
model with corresponding parameters.
Args:
d_model: the number of expected features in the encoder/decoder inputs (default=512).
nhead: the number of heads in the multiheadattention models (default=8).
num_encoder_layers: the number of sub-encoder-layers in the encoder (default=6).
num_decoder_layers: the number of sub-decoder-layers in the decoder (default=6).
dim_feedforward: the dimension of the feedforward network model (default=2048).
dropout: the dropout value (default=0.1).
activation: the activation function of encoder/decoder intermediate layer, can be a string
("relu" or "gelu") or a unary callable. Default: relu
custom_encoder: custom encoder (default=None).
custom_decoder: custom decoder (default=None).
layer_norm_eps: the eps value in layer normalization components (default=1e-5).
batch_first: If ``True``, then the input and output tensors are provided
as (batch, seq, feature). Default: ``False`` (seq, batch, feature).
norm_first: if ``True``, encoder and decoder layers will perform LayerNorms before
other attention and feedforward operations, otherwise after. Default: ``False`` (after).
Examples::
>>> transformer_model = nn.Transformer(nhead=16, num_encoder_layers=12)
>>> src = torch.rand((10, 32, 512))
>>> tgt = torch.rand((20, 32, 512))
>>> out = transformer_model(src, tgt)
Note: A full example to apply nn.Transformer module for the word language model is available in
https://github.com/pytorch/examples/tree/master/word_language_model
"""
def __init__(self, d_model: int = 512, nhead: int = 8, num_encoder_layers: int = 6,
num_decoder_layers: int = 6, dim_feedforward: int = 2048, dropout: float = 0.1,
activation: Union[str, Callable[[Tensor], Tensor]] = F.relu,
custom_encoder: Optional[Any] = None, custom_decoder: Optional[Any] = None,
layer_norm_eps: float = 1e-5, batch_first: bool = False, norm_first: bool = False,
device=None, dtype=None) -> None:
factory_kwargs = {'device': device, 'dtype': dtype}
super(Transformer, self).__init__()
if custom_encoder is not None:
self.encoder = custom_encoder
else:
encoder_layer = TransformerEncoderLayer(d_model, nhead, dim_feedforward, dropout,
activation, layer_norm_eps, batch_first, norm_first,
**factory_kwargs)
encoder_norm = LayerNorm(d_model, eps=layer_norm_eps, **factory_kwargs)
self.encoder = TransformerEncoder(encoder_layer, num_encoder_layers, encoder_norm)
if custom_decoder is not None:
self.decoder = custom_decoder
else:
decoder_layer = TransformerDecoderLayer(d_model, nhead, dim_feedforward, dropout,
activation, layer_norm_eps, batch_first, norm_first,
**factory_kwargs)
decoder_norm = LayerNorm(d_model, eps=layer_norm_eps, **factory_kwargs)
self.decoder = TransformerDecoder(decoder_layer, num_decoder_layers, decoder_norm)
self._reset_parameters()
self.d_model = d_model
self.nhead = nhead
self.batch_first = batch_first
[docs] def forward(self, src: Tensor, tgt: Tensor, src_mask: Optional[Tensor] = None, tgt_mask: Optional[Tensor] = None,
memory_mask: Optional[Tensor] = None, src_key_padding_mask: Optional[Tensor] = None,
tgt_key_padding_mask: Optional[Tensor] = None, memory_key_padding_mask: Optional[Tensor] = None) -> Tensor:
r"""Take in and process masked source/target sequences.
Args:
src: the sequence to the encoder (required).
tgt: the sequence to the decoder (required).
src_mask: the additive mask for the src sequence (optional).
tgt_mask: the additive mask for the tgt sequence (optional).
memory_mask: the additive mask for the encoder output (optional).
src_key_padding_mask: the ByteTensor mask for src keys per batch (optional).
tgt_key_padding_mask: the ByteTensor mask for tgt keys per batch (optional).
memory_key_padding_mask: the ByteTensor mask for memory keys per batch (optional).
Shape:
- src: :math:`(S, E)` for unbatched input, :math:`(S, N, E)` if `batch_first=False` or
`(N, S, E)` if `batch_first=True`.
- tgt: :math:`(T, E)` for unbatched input, :math:`(T, N, E)` if `batch_first=False` or
`(N, T, E)` if `batch_first=True`.
- src_mask: :math:`(S, S)` or :math:`(N\cdot\text{num\_heads}, S, S)`.
- tgt_mask: :math:`(T, T)` or :math:`(N\cdot\text{num\_heads}, T, T)`.
- memory_mask: :math:`(T, S)`.
- src_key_padding_mask: :math:`(S)` for unbatched input otherwise :math:`(N, S)`.
- tgt_key_padding_mask: :math:`(T)` for unbatched input otherwise :math:`(N, T)`.
- memory_key_padding_mask: :math:`(S)` for unbatched input otherwise :math:`(N, S)`.
Note: [src/tgt/memory]_mask ensures that position i is allowed to attend the unmasked
positions. If a ByteTensor is provided, the non-zero positions are not allowed to attend
while the zero positions will be unchanged. If a BoolTensor is provided, positions with ``True``
are not allowed to attend while ``False`` values will be unchanged. If a FloatTensor
is provided, it will be added to the attention weight.
[src/tgt/memory]_key_padding_mask provides specified elements in the key to be ignored by
the attention. If a ByteTensor is provided, the non-zero positions will be ignored while the zero
positions will be unchanged. If a BoolTensor is provided, the positions with the
value of ``True`` will be ignored while the position with the value of ``False`` will be unchanged.
- output: :math:`(T, E)` for unbatched input, :math:`(T, N, E)` if `batch_first=False` or
`(N, T, E)` if `batch_first=True`.
Note: Due to the multi-head attention architecture in the transformer model,
the output sequence length of a transformer is same as the input sequence
(i.e. target) length of the decode.
where S is the source sequence length, T is the target sequence length, N is the
batch size, E is the feature number
Examples:
>>> output = transformer_model(src, tgt, src_mask=src_mask, tgt_mask=tgt_mask)
"""
is_batched = src.dim() == 3
if not self.batch_first and src.size(1) != tgt.size(1) and is_batched:
raise RuntimeError("the batch number of src and tgt must be equal")
elif self.batch_first and src.size(0) != tgt.size(0) and is_batched:
raise RuntimeError("the batch number of src and tgt must be equal")
if src.size(-1) != self.d_model or tgt.size(-1) != self.d_model:
raise RuntimeError("the feature number of src and tgt must be equal to d_model")
memory = self.encoder(src, mask=src_mask, src_key_padding_mask=src_key_padding_mask)
output = self.decoder(tgt, memory, tgt_mask=tgt_mask, memory_mask=memory_mask,
tgt_key_padding_mask=tgt_key_padding_mask,
memory_key_padding_mask=memory_key_padding_mask)
return output
[docs] @staticmethod
def generate_square_subsequent_mask(sz: int) -> Tensor:
r"""Generate a square mask for the sequence. The masked positions are filled with float('-inf').
Unmasked positions are filled with float(0.0).
"""
return torch.triu(torch.full((sz, sz), float('-inf')), diagonal=1)
def _reset_parameters(self):
r"""Initiate parameters in the transformer model."""
for p in self.parameters():
if p.dim() > 1:
xavier_uniform_(p)
[docs]class TransformerEncoder(Module):
r"""TransformerEncoder is a stack of N encoder layers
Args:
encoder_layer: an instance of the TransformerEncoderLayer() class (required).
num_layers: the number of sub-encoder-layers in the encoder (required).
norm: the layer normalization component (optional).
enable_nested_tensor: if True, input will automatically convert to nested tensor
(and convert back on output). This will improve the overall performance of
TransformerEncoder when padding rate is high. Default: ``False`` (disabled).
Examples::
>>> encoder_layer = nn.TransformerEncoderLayer(d_model=512, nhead=8)
>>> transformer_encoder = nn.TransformerEncoder(encoder_layer, num_layers=6)
>>> src = torch.rand(10, 32, 512)
>>> out = transformer_encoder(src)
"""
__constants__ = ['norm']
def __init__(self, encoder_layer, num_layers, norm=None, enable_nested_tensor=False):
super(TransformerEncoder, self).__init__()
self.layers = _get_clones(encoder_layer, num_layers)
self.num_layers = num_layers
self.norm = norm
self.enable_nested_tensor = enable_nested_tensor
[docs] def forward(self, src: Tensor, mask: Optional[Tensor] = None, src_key_padding_mask: Optional[Tensor] = None) -> Tensor:
r"""Pass the input through the encoder layers in turn.
Args:
src: the sequence to the encoder (required).
mask: the mask for the src sequence (optional).
src_key_padding_mask: the mask for the src keys per batch (optional).
Shape:
see the docs in Transformer class.
"""
output = src
convert_to_nested = False
first_layer = self.layers[0]
if isinstance(first_layer, torch.nn.TransformerEncoderLayer):
if (not first_layer.norm_first and not first_layer.training and
first_layer.self_attn.batch_first and
first_layer.self_attn._qkv_same_embed_dim and first_layer.activation_relu_or_gelu and
first_layer.norm1.eps == first_layer.norm2.eps and
src.dim() == 3 and self.enable_nested_tensor) :
if src_key_padding_mask is not None and not output.is_nested and mask is None:
tensor_args = (
src,
first_layer.self_attn.in_proj_weight,
first_layer.self_attn.in_proj_bias,
first_layer.self_attn.out_proj.weight,
first_layer.self_attn.out_proj.bias,
first_layer.norm1.weight,
first_layer.norm1.bias,
first_layer.norm2.weight,
first_layer.norm2.bias,
first_layer.linear1.weight,
first_layer.linear1.bias,
first_layer.linear2.weight,
first_layer.linear2.bias,
)
if not torch.overrides.has_torch_function(tensor_args):
if not torch.is_grad_enabled() or all([not x.requires_grad for x in tensor_args]):
if output.is_cuda or 'cpu' in str(output.device):
convert_to_nested = True
output = torch._nested_tensor_from_mask(output, src_key_padding_mask.logical_not())
for mod in self.layers:
if convert_to_nested:
output = mod(output, src_mask=mask)
else:
output = mod(output, src_mask=mask, src_key_padding_mask=src_key_padding_mask)
if convert_to_nested:
output = output.to_padded_tensor(0.)
if self.norm is not None:
output = self.norm(output)
return output
[docs]class TransformerDecoder(Module):
r"""TransformerDecoder is a stack of N decoder layers
Args:
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).
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)
"""
__constants__ = ['norm']
def __init__(self, decoder_layer, num_layers, norm=None):
super(TransformerDecoder, self).__init__()
self.layers = _get_clones(decoder_layer, num_layers)
self.num_layers = num_layers
self.norm = norm
[docs] def forward(self, tgt: Tensor, memory: Tensor, tgt_mask: Optional[Tensor] = None,
memory_mask: Optional[Tensor] = None, tgt_key_padding_mask: Optional[Tensor] = None,
memory_key_padding_mask: Optional[Tensor] = None) -> Tensor:
r"""Pass the inputs (and mask) through the decoder layer in turn.
Args:
tgt: the sequence to the decoder (required).
memory: the sequence from the last layer of the encoder (required).
tgt_mask: the mask for the tgt sequence (optional).
memory_mask: the mask for the memory sequence (optional).
tgt_key_padding_mask: the mask for the tgt keys per batch (optional).
memory_key_padding_mask: the mask for the memory keys per batch (optional).
Shape:
see the docs in Transformer class.
"""
output = tgt
for mod in self.layers:
output = mod(output, memory, tgt_mask=tgt_mask,
memory_mask=memory_mask,
tgt_key_padding_mask=tgt_key_padding_mask,
memory_key_padding_mask=memory_key_padding_mask)
if self.norm is not None:
output = self.norm(output)
return output
class TransformerEncoderLayer(Module):
r"""TransformerEncoderLayer is made up of self-attn and feedforward network.
This standard encoder layer is based on the paper "Attention Is All You Need".
Ashish Vaswani, Noam Shazeer, Niki Parmar, Jakob Uszkoreit, Llion Jones, Aidan N Gomez,
Lukasz Kaiser, and Illia Polosukhin. 2017. Attention is all you need. In Advances in
Neural Information Processing Systems, pages 6000-6010. Users may modify or implement
in a different way during application.
Args:
d_model: the number of expected features in the input (required).
nhead: the number of heads in the multiheadattention models (required).
dim_feedforward: the dimension of the feedforward network model (default=2048).
dropout: the dropout value (default=0.1).
activation: the activation function of the intermediate layer, can be a string
("relu" or "gelu") or a unary callable. Default: relu
layer_norm_eps: the eps value in layer normalization components (default=1e-5).
batch_first: If ``True``, then the input and output tensors are provided
as (batch, seq, feature). Default: ``False`` (seq, batch, feature).
norm_first: if ``True``, layer norm is done prior to attention and feedforward
operations, respectivaly. Otherwise it's done after. Default: ``False`` (after).
Examples::
>>> encoder_layer = nn.TransformerEncoderLayer(d_model=512, nhead=8)
>>> src = torch.rand(10, 32, 512)
>>> out = encoder_layer(src)
Alternatively, when ``batch_first`` is ``True``:
>>> encoder_layer = nn.TransformerEncoderLayer(d_model=512, nhead=8, batch_first=True)
>>> src = torch.rand(32, 10, 512)
>>> out = encoder_layer(src)
Fast path:
forward() will use a special optimized implementation if all of the following
conditions are met:
- Either autograd is disabled (using ``torch.inference_mode`` or ``torch.no_grad``) or no tensor
argument ``requires_grad``
- training is disabled (using ``.eval()``)
- batch_first is ``True`` and the input is batched (i.e., ``src.dim() == 3``)
- norm_first is ``False`` (this restriction may be loosened in the future)
- activation is one of: ``"relu"``, ``"gelu"``, ``torch.functional.relu``, or ``torch.functional.gelu``
- at most one of ``src_mask`` and ``src_key_padding_mask`` is passed
- if src is a `NestedTensor <https://pytorch.org/docs/stable/nested.html>`_, neither ``src_mask``
nor ``src_key_padding_mask`` is passed
- the two ``LayerNorm`` instances have a consistent ``eps`` value (this will naturally be the case
unless the caller has manually modified one without modifying the other)
If the optimized implementation is in use, a
`NestedTensor <https://pytorch.org/docs/stable/nested.html>`_ can be
passed for ``src`` to represent padding more efficiently than using a padding
mask. In this case, a `NestedTensor <https://pytorch.org/docs/stable/nested.html>`_ will be
returned, and an additional speedup proportional to the fraction of the input that
is padding can be expected.
"""
__constants__ = ['batch_first', 'norm_first']
def __init__(self, d_model: int, nhead: int, dim_feedforward: int = 2048, dropout: float = 0.1,
activation: Union[str, Callable[[Tensor], Tensor]] = F.relu,
layer_norm_eps: float = 1e-5, batch_first: bool = False, norm_first: bool = False,
device=None, dtype=None) -> None:
factory_kwargs = {'device': device, 'dtype': dtype}
super(TransformerEncoderLayer, self).__init__()
self.self_attn = MultiheadAttention(d_model, nhead, dropout=dropout, batch_first=batch_first,
**factory_kwargs)
# Implementation of Feedforward model
self.linear1 = Linear(d_model, dim_feedforward, **factory_kwargs)
self.dropout = Dropout(dropout)
self.linear2 = Linear(dim_feedforward, d_model, **factory_kwargs)
self.norm_first = norm_first
self.norm1 = LayerNorm(d_model, eps=layer_norm_eps, **factory_kwargs)
self.norm2 = LayerNorm(d_model, eps=layer_norm_eps, **factory_kwargs)
self.dropout1 = Dropout(dropout)
self.dropout2 = Dropout(dropout)
# Legacy string support for activation function.
if isinstance(activation, str):
activation = _get_activation_fn(activation)
# We can't test self.activation in forward() in TorchScript,
# so stash some information about it instead.
if activation is F.relu:
self.activation_relu_or_gelu = 1
elif activation is F.gelu:
self.activation_relu_or_gelu = 2
else:
self.activation_relu_or_gelu = 0
self.activation = activation
def __setstate__(self, state):
super(TransformerEncoderLayer, self).__setstate__(state)
if not hasattr(self, 'activation'):
self.activation = F.relu
def forward(self, src: Tensor, src_mask: Optional[Tensor] = None,
src_key_padding_mask: Optional[Tensor] = None) -> Tensor:
r"""Pass the input through the encoder layer.
Args:
src: the sequence to the encoder layer (required).
src_mask: the mask for the src sequence (optional).
src_key_padding_mask: the mask for the src keys per batch (optional).
Shape:
see the docs in Transformer class.
"""
# see Fig. 1 of https://arxiv.org/pdf/2002.04745v1.pdf
if (src.dim() == 3 and not self.norm_first and not self.training and
self.self_attn.batch_first and
self.self_attn._qkv_same_embed_dim and self.activation_relu_or_gelu and
self.norm1.eps == self.norm2.eps and
src_mask is None and
not (src.is_nested and src_key_padding_mask is not None)):
tensor_args = (
src,
self.self_attn.in_proj_weight,
self.self_attn.in_proj_bias,
self.self_attn.out_proj.weight,
self.self_attn.out_proj.bias,
self.norm1.weight,
self.norm1.bias,
self.norm2.weight,
self.norm2.bias,
self.linear1.weight,
self.linear1.bias,
self.linear2.weight,
self.linear2.bias,
)
if (not torch.overrides.has_torch_function(tensor_args) and
# We have to use a list comprehension here because TorchScript
# doesn't support generator expressions.
all([(x.is_cuda or 'cpu' in str(x.device)) for x in tensor_args]) and
(not torch.is_grad_enabled() or all([not x.requires_grad for x in tensor_args]))):
return torch._transformer_encoder_layer_fwd(
src,
self.self_attn.embed_dim,
self.self_attn.num_heads,
self.self_attn.in_proj_weight,
self.self_attn.in_proj_bias,
self.self_attn.out_proj.weight,
self.self_attn.out_proj.bias,
self.activation_relu_or_gelu == 2,
False, # norm_first, currently not supported
self.norm1.eps,
self.norm1.weight,
self.norm1.bias,
self.norm2.weight,
self.norm2.bias,
self.linear1.weight,
self.linear1.bias,
self.linear2.weight,
self.linear2.bias,
src_mask if src_mask is not None else src_key_padding_mask, # TODO: split into two args
)
x = src
if self.norm_first:
x = x + self._sa_block(self.norm1(x), src_mask, src_key_padding_mask)
x = x + self._ff_block(self.norm2(x))
else:
x = self.norm1(x + self._sa_block(x, src_mask, src_key_padding_mask))
x = self.norm2(x + self._ff_block(x))
return x
# self-attention block
def _sa_block(self, x: Tensor,
attn_mask: Optional[Tensor], key_padding_mask: Optional[Tensor]) -> Tensor:
x = self.self_attn(x, x, x,
attn_mask=attn_mask,
key_padding_mask=key_padding_mask,
need_weights=False)[0]
return self.dropout1(x)
# feed forward block
def _ff_block(self, x: Tensor) -> Tensor:
x = self.linear2(self.dropout(self.activation(self.linear1(x))))
return self.dropout2(x)
[docs]class TransformerDecoderLayer(Module):
r"""TransformerDecoderLayer is made up of self-attn, multi-head-attn and feedforward network.
This standard decoder layer is based on the paper "Attention Is All You Need".
Ashish Vaswani, Noam Shazeer, Niki Parmar, Jakob Uszkoreit, Llion Jones, Aidan N Gomez,
Lukasz Kaiser, and Illia Polosukhin. 2017. Attention is all you need. In Advances in
Neural Information Processing Systems, pages 6000-6010. Users may modify or implement
in a different way during application.
Args:
d_model: the number of expected features in the input (required).
nhead: the number of heads in the multiheadattention models (required).
dim_feedforward: the dimension of the feedforward network model (default=2048).
dropout: the dropout value (default=0.1).
activation: the activation function of the intermediate layer, can be a string
("relu" or "gelu") or a unary callable. Default: relu
layer_norm_eps: the eps value in layer normalization components (default=1e-5).
batch_first: If ``True``, then the input and output tensors are provided
as (batch, seq, feature). Default: ``False`` (seq, batch, feature).
norm_first: if ``True``, layer norm is done prior to self attention, multihead
attention and feedforward operations, respectivaly. Otherwise it's done after.
Default: ``False`` (after).
Examples::
>>> decoder_layer = nn.TransformerDecoderLayer(d_model=512, nhead=8)
>>> memory = torch.rand(10, 32, 512)
>>> tgt = torch.rand(20, 32, 512)
>>> out = decoder_layer(tgt, memory)
Alternatively, when ``batch_first`` is ``True``:
>>> decoder_layer = nn.TransformerDecoderLayer(d_model=512, nhead=8, batch_first=True)
>>> memory = torch.rand(32, 10, 512)
>>> tgt = torch.rand(32, 20, 512)
>>> out = decoder_layer(tgt, memory)
"""
__constants__ = ['batch_first', 'norm_first']
def __init__(self, d_model: int, nhead: int, dim_feedforward: int = 2048, dropout: float = 0.1,
activation: Union[str, Callable[[Tensor], Tensor]] = F.relu,
layer_norm_eps: float = 1e-5, batch_first: bool = False, norm_first: bool = False,
device=None, dtype=None) -> None:
factory_kwargs = {'device': device, 'dtype': dtype}
super(TransformerDecoderLayer, self).__init__()
self.self_attn = MultiheadAttention(d_model, nhead, dropout=dropout, batch_first=batch_first,
**factory_kwargs)
self.multihead_attn = MultiheadAttention(d_model, nhead, dropout=dropout, batch_first=batch_first,
**factory_kwargs)
# Implementation of Feedforward model
self.linear1 = Linear(d_model, dim_feedforward, **factory_kwargs)
self.dropout = Dropout(dropout)
self.linear2 = Linear(dim_feedforward, d_model, **factory_kwargs)
self.norm_first = norm_first
self.norm1 = LayerNorm(d_model, eps=layer_norm_eps, **factory_kwargs)
self.norm2 = LayerNorm(d_model, eps=layer_norm_eps, **factory_kwargs)
self.norm3 = LayerNorm(d_model, eps=layer_norm_eps, **factory_kwargs)
self.dropout1 = Dropout(dropout)
self.dropout2 = Dropout(dropout)
self.dropout3 = Dropout(dropout)
# Legacy string support for activation function.
if isinstance(activation, str):
self.activation = _get_activation_fn(activation)
else:
self.activation = activation
def __setstate__(self, state):
if 'activation' not in state:
state['activation'] = F.relu
super(TransformerDecoderLayer, self).__setstate__(state)
[docs] def forward(self, tgt: Tensor, memory: Tensor, tgt_mask: Optional[Tensor] = None, memory_mask: Optional[Tensor] = None,
tgt_key_padding_mask: Optional[Tensor] = None, memory_key_padding_mask: Optional[Tensor] = None) -> Tensor:
r"""Pass the inputs (and mask) through the decoder layer.
Args:
tgt: the sequence to the decoder layer (required).
memory: the sequence from the last layer of the encoder (required).
tgt_mask: the mask for the tgt sequence (optional).
memory_mask: the mask for the memory sequence (optional).
tgt_key_padding_mask: the mask for the tgt keys per batch (optional).
memory_key_padding_mask: the mask for the memory keys per batch (optional).
Shape:
see the docs in Transformer class.
"""
# see Fig. 1 of https://arxiv.org/pdf/2002.04745v1.pdf
x = tgt
if self.norm_first:
x = x + self._sa_block(self.norm1(x), tgt_mask, tgt_key_padding_mask)
x = x + self._mha_block(self.norm2(x), memory, memory_mask, memory_key_padding_mask)
x = x + self._ff_block(self.norm3(x))
else:
x = self.norm1(x + self._sa_block(x, tgt_mask, tgt_key_padding_mask))
x = self.norm2(x + self._mha_block(x, memory, memory_mask, memory_key_padding_mask))
x = self.norm3(x + self._ff_block(x))
return x
# self-attention block
def _sa_block(self, x: Tensor,
attn_mask: Optional[Tensor], key_padding_mask: Optional[Tensor]) -> Tensor:
x = self.self_attn(x, x, x,
attn_mask=attn_mask,
key_padding_mask=key_padding_mask,
need_weights=False)[0]
return self.dropout1(x)
# multihead attention block
def _mha_block(self, x: Tensor, mem: Tensor,
attn_mask: Optional[Tensor], key_padding_mask: Optional[Tensor]) -> Tensor:
x = self.multihead_attn(x, mem, mem,
attn_mask=attn_mask,
key_padding_mask=key_padding_mask,
need_weights=False)[0]
return self.dropout2(x)
# feed forward block
def _ff_block(self, x: Tensor) -> Tensor:
x = self.linear2(self.dropout(self.activation(self.linear1(x))))
return self.dropout3(x)
def _get_clones(module, N):
return ModuleList([copy.deepcopy(module) for i in range(N)])
def _get_activation_fn(activation: str) -> Callable[[Tensor], Tensor]:
if activation == "relu":
return F.relu
elif activation == "gelu":
return F.gelu
raise RuntimeError("activation should be relu/gelu, not {}".format(activation))
