import torch
from espnet.nets.pytorch_backend.transformer.attention import MultiHeadedAttention
from espnet.nets.pytorch_backend.transformer.embedding import PositionalEncoding
from espnet.nets.pytorch_backend.transformer.encoder_layer import EncoderLayer
from espnet.nets.pytorch_backend.transformer.layer_norm import LayerNorm
from espnet.nets.pytorch_backend.transformer.multi_layer_conv import MultiLayeredConv1d
from espnet.nets.pytorch_backend.transformer.positionwise_feed_forward import PositionwiseFeedForward
from espnet.nets.pytorch_backend.transformer.repeat import repeat
from espnet.nets.pytorch_backend.transformer.subsampling import Conv2dSubsampling
[docs]class Encoder(torch.nn.Module):
"""Transformer encoder module
:param int idim: input dim
:param int attention_dim: dimention of attention
:param int attention_heads: the number of heads of multi head attention
:param int linear_units: the number of units of position-wise feed forward
:param int num_blocks: the number of decoder blocks
:param float dropout_rate: dropout rate
:param float attention_dropout_rate: dropout rate in attention
:param float positional_dropout_rate: dropout rate after adding positional encoding
:param str or torch.nn.Module input_layer: input layer type
:param class pos_enc_class: PositionalEncoding or ScaledPositionalEncoding
:param bool normalize_before: whether to use layer_norm before the first block
:param bool concat_after: whether to concat attention layer's input and output
if True, additional linear will be applied. i.e. x -> x + linear(concat(x, att(x)))
if False, no additional linear will be applied. i.e. x -> x + att(x)
:param str positionwise_layer_type: linear of conv1d
:param int positionwise_conv_kernel_size: kernel size of positionwise conv1d layer
:param int padding_idx: padding_idx for input_layer=embed
"""
def __init__(self, idim,
attention_dim=256,
attention_heads=4,
linear_units=2048,
num_blocks=6,
dropout_rate=0.1,
positional_dropout_rate=0.1,
attention_dropout_rate=0.0,
input_layer="conv2d",
pos_enc_class=PositionalEncoding,
normalize_before=True,
concat_after=False,
positionwise_layer_type="linear",
positionwise_conv_kernel_size=1,
padding_idx=-1):
super(Encoder, self).__init__()
if input_layer == "linear":
self.embed = torch.nn.Sequential(
torch.nn.Linear(idim, attention_dim),
torch.nn.LayerNorm(attention_dim),
torch.nn.Dropout(dropout_rate),
torch.nn.ReLU(),
pos_enc_class(attention_dim, positional_dropout_rate)
)
elif input_layer == "conv2d":
self.embed = Conv2dSubsampling(idim, attention_dim, dropout_rate)
elif input_layer == "embed":
self.embed = torch.nn.Sequential(
torch.nn.Embedding(idim, attention_dim, padding_idx=padding_idx),
pos_enc_class(attention_dim, positional_dropout_rate)
)
elif isinstance(input_layer, torch.nn.Module):
self.embed = torch.nn.Sequential(
input_layer,
pos_enc_class(attention_dim, positional_dropout_rate),
)
elif input_layer is None:
self.embed = torch.nn.Sequential(
pos_enc_class(attention_dim, positional_dropout_rate)
)
else:
raise ValueError("unknown input_layer: " + input_layer)
self.normalize_before = normalize_before
if positionwise_layer_type == "linear":
positionwise_layer = PositionwiseFeedForward
positionwise_layer_args = (attention_dim, linear_units, dropout_rate)
elif positionwise_layer_type == "conv1d":
positionwise_layer = MultiLayeredConv1d
positionwise_layer_args = (attention_dim, linear_units, positionwise_conv_kernel_size, dropout_rate)
else:
raise NotImplementedError("Support only linear or conv1d.")
self.encoders = repeat(
num_blocks,
lambda: EncoderLayer(
attention_dim,
MultiHeadedAttention(attention_heads, attention_dim, attention_dropout_rate),
positionwise_layer(*positionwise_layer_args),
dropout_rate,
normalize_before,
concat_after
)
)
if self.normalize_before:
self.after_norm = LayerNorm(attention_dim)
[docs] def forward(self, xs, masks):
"""Embed positions in tensor
:param torch.Tensor xs: input tensor
:param torch.Tensor masks: input mask
:return: position embedded tensor and mask
:rtype Tuple[torch.Tensor, torch.Tensor]:
"""
if isinstance(self.embed, Conv2dSubsampling):
xs, masks = self.embed(xs, masks)
else:
xs = self.embed(xs)
xs, masks = self.encoders(xs, masks)
if self.normalize_before:
xs = self.after_norm(xs)
return xs, masks