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# Copyright (c) 2021 Mobvoi Inc (Binbin Zhang, Di Wu)
# 2022 Xingchen Song ([email protected])
# 2022 58.com(Wuba) Inc AI Lab.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
# Modified from ESPnet(https://github.com/espnet/espnet)
"""Encoder self-attention layer definition."""
from typing import Optional, Tuple
import torch
from torch import nn
class StrideConformerEncoderLayer(nn.Module):
"""Encoder layer module.
Args:
size (int): Input dimension.
self_attn (torch.nn.Module): Self-attention module instance.
`MultiHeadedAttention` or `RelPositionMultiHeadedAttention`
instance can be used as the argument.
feed_forward (torch.nn.Module): Feed-forward module instance.
`PositionwiseFeedForward` instance can be used as the argument.
feed_forward_macaron (torch.nn.Module): Additional feed-forward module
instance.
`PositionwiseFeedForward` instance can be used as the argument.
conv_module (torch.nn.Module): Convolution module instance.
`ConvlutionModule` instance can be used as the argument.
dropout_rate (float): Dropout rate.
normalize_before (bool):
True: use layer_norm before each sub-block.
False: use layer_norm after each sub-block.
"""
def __init__(self,
size: int,
self_attn: torch.nn.Module,
feed_forward: Optional[nn.Module] = None,
feed_forward_macaron: Optional[nn.Module] = None,
conv_module: Optional[nn.Module] = None,
pointwise_conv_layer: Optional[nn.Module] = None,
dropout_rate: float = 0.1,
normalize_before: bool = True):
"""Construct an EncoderLayer object."""
super().__init__()
self.self_attn = self_attn
self.feed_forward = feed_forward
self.feed_forward_macaron = feed_forward_macaron
self.conv_module = conv_module
self.pointwise_conv_layer = pointwise_conv_layer
self.norm_ff = nn.LayerNorm(size, eps=1e-5) # for the FNN module
self.norm_mha = nn.LayerNorm(size, eps=1e-5) # for the MHA module
if feed_forward_macaron is not None:
self.norm_ff_macaron = nn.LayerNorm(size, eps=1e-5)
self.ff_scale = 0.5
else:
self.ff_scale = 1.0
if self.conv_module is not None:
self.norm_conv = nn.LayerNorm(size, eps=1e-5) # for the CNN module
self.norm_final = nn.LayerNorm(
size, eps=1e-5) # for the final output of the block
self.dropout = nn.Dropout(dropout_rate)
self.size = size
self.normalize_before = normalize_before
self.concat_linear = nn.Linear(size + size, size)
def forward(
self,
x: torch.Tensor,
mask: torch.Tensor,
pos_emb: torch.Tensor,
mask_pad: torch.Tensor = torch.ones((0, 0, 0), dtype=torch.bool),
att_cache: torch.Tensor = torch.zeros((0, 0, 0, 0)),
cnn_cache: torch.Tensor = torch.zeros((0, 0, 0, 0)),
) -> Tuple[torch.Tensor, torch.Tensor, torch.Tensor, torch.Tensor]:
"""Compute encoded features.
Args:
x (torch.Tensor): (#batch, time, size)
mask (torch.Tensor): Mask tensor for the input (#batch, time，time),
(0, 0, 0) means fake mask.
pos_emb (torch.Tensor): positional encoding, must not be None
for ConformerEncoderLayer.
mask_pad (torch.Tensor): batch padding mask used for conv module.
(#batch, 1，time), (0, 0, 0) means fake mask.
att_cache (torch.Tensor): Cache tensor of the KEY & VALUE
(#batch=1, head, cache_t1, d_k * 2), head * d_k == size.
cnn_cache (torch.Tensor): Convolution cache in conformer layer
(#batch=1, size, cache_t2)
Returns:
torch.Tensor: Output tensor (#batch, time, size).
torch.Tensor: Mask tensor (#batch, time, time).
torch.Tensor: att_cache tensor,
(#batch=1, head, cache_t1 + time, d_k * 2).
torch.Tensor: cnn_cahce tensor (#batch, size, cache_t2).
"""
# whether to use macaron style
if self.feed_forward_macaron is not None:
residual = x
if self.normalize_before:
x = self.norm_ff_macaron(x)
x = residual + self.ff_scale * self.dropout(
self.feed_forward_macaron(x))
if not self.normalize_before:
x = self.norm_ff_macaron(x)
# multi-headed self-attention module
residual = x
if self.normalize_before:
x = self.norm_mha(x)
x_att, new_att_cache = self.self_attn(x, x, x, mask, pos_emb,
att_cache)
x = residual + self.dropout(x_att)
if not self.normalize_before:
x = self.norm_mha(x)
# convolution module
# Fake new cnn cache here, and then change it in conv_module
new_cnn_cache = torch.tensor([0.0], dtype=x.dtype, device=x.device)
if self.conv_module is not None:
residual = x
if self.normalize_before:
x = self.norm_conv(x)
x, new_cnn_cache = self.conv_module(x, mask_pad, cnn_cache)
# add pointwise_conv for efficient conformer
# pointwise_conv_layer does not change shape
if self.pointwise_conv_layer is not None:
residual = residual.transpose(1, 2)
residual = self.pointwise_conv_layer(residual)
residual = residual.transpose(1, 2)
assert residual.size(0) == x.size(0)
assert residual.size(1) == x.size(1)
assert residual.size(2) == x.size(2)
x = residual + self.dropout(x)
if not self.normalize_before:
x = self.norm_conv(x)
# feed forward module
residual = x
if self.normalize_before:
x = self.norm_ff(x)
x = residual + self.ff_scale * self.dropout(self.feed_forward(x))
if not self.normalize_before:
x = self.norm_ff(x)
if self.conv_module is not None:
x = self.norm_final(x)
return x, mask, new_att_cache, new_cnn_cache
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