import torch
from torch import nn
from torch.autograd import Variable
from torch.nn import functional as F
class Linear(nn.Module):
def __init__(self,
in_features,
out_features,
bias=True,
init_gain='linear'):
super(Linear, self).__init__()
self.linear_layer = torch.nn.Linear(
in_features, out_features, bias=bias)
self._init_w(init_gain)
def _init_w(self, init_gain):
torch.nn.init.xavier_uniform_(
self.linear_layer.weight,
gain=torch.nn.init.calculate_gain(init_gain))
def forward(self, x):
return self.linear_layer(x)
class LinearBN(nn.Module):
def __init__(self,
in_features,
out_features,
bias=True,
init_gain='linear'):
super(LinearBN, self).__init__()
self.linear_layer = torch.nn.Linear(
in_features, out_features, bias=bias)
self.bn = nn.BatchNorm1d(out_features)
self._init_w(init_gain)
def _init_w(self, init_gain):
torch.nn.init.xavier_uniform_(
self.linear_layer.weight,
gain=torch.nn.init.calculate_gain(init_gain))
def forward(self, x):
out = self.linear_layer(x)
if len(out.shape) == 3:
out = out.permute(1, 2, 0)
out = self.bn(out)
if len(out.shape) == 3:
out = out.permute(2, 0, 1)
return out
class Prenet(nn.Module):
def __init__(self,
in_features,
prenet_type="original",
prenet_dropout=True,
out_features=[256, 256],
bias=True):
super(Prenet, self).__init__()
self.prenet_type = prenet_type
self.prenet_dropout = prenet_dropout
in_features = [in_features] + out_features[:-1]
if prenet_type == "bn":
self.layers = nn.ModuleList([
LinearBN(in_size, out_size, bias=bias)
for (in_size, out_size) in zip(in_features, out_features)
])
elif prenet_type == "original":
self.layers = nn.ModuleList([
Linear(in_size, out_size, bias=bias)
for (in_size, out_size) in zip(in_features, out_features)
])
def forward(self, x):
for linear in self.layers:
if self.prenet_dropout:
x = F.dropout(F.relu(linear(x)), p=0.5, training=self.training)
else:
x = F.relu(linear(x))
return x
class LocationLayer(nn.Module):
def __init__(self,
attention_dim,
attention_n_filters=32,
attention_kernel_size=31):
super(LocationLayer, self).__init__()
self.location_conv = nn.Conv1d(
in_channels=2,
out_channels=attention_n_filters,
kernel_size=attention_kernel_size,
stride=1,
padding=(attention_kernel_size - 1) // 2,
bias=False)
self.location_dense = Linear(
attention_n_filters, attention_dim, bias=False, init_gain='tanh')
def forward(self, attention_cat):
processed_attention = self.location_conv(attention_cat)
processed_attention = self.location_dense(
processed_attention.transpose(1, 2))
return processed_attention
class Attention(nn.Module):
# Pylint gets confused by PyTorch conventions here
#pylint: disable=attribute-defined-outside-init
def __init__(self, query_dim, embedding_dim, attention_dim,
location_attention, attention_location_n_filters,
attention_location_kernel_size, windowing, norm, forward_attn,
trans_agent, forward_attn_mask):
super(Attention, self).__init__()
self.query_layer = Linear(
query_dim, attention_dim, bias=False, init_gain='tanh')
self.inputs_layer = Linear(
embedding_dim, attention_dim, bias=False, init_gain='tanh')
self.v = Linear(attention_dim, 1, bias=True)
if trans_agent:
self.ta = nn.Linear(
query_dim + embedding_dim, 1, bias=True)
if location_attention:
self.location_layer = LocationLayer(
attention_dim,
attention_location_n_filters,
attention_location_kernel_size,
)
self._mask_value = -float("inf")
self.windowing = windowing
self.win_idx = None
self.norm = norm
self.forward_attn = forward_attn
self.trans_agent = trans_agent
self.forward_attn_mask = forward_attn_mask
self.location_attention = location_attention
def init_win_idx(self):
self.win_idx = -1
self.win_back = 2
self.win_front = 6
def init_forward_attn(self, inputs):
B = inputs.shape[0]
T = inputs.shape[1]
self.alpha = torch.cat(
[torch.ones([B, 1]),
torch.zeros([B, T])[:, :-1] + 1e-7], dim=1).to(inputs.device)
self.u = (0.5 * torch.ones([B, 1])).to(inputs.device)
def init_location_attention(self, inputs):
B = inputs.shape[0]
T = inputs.shape[1]
self.attention_weights_cum = Variable(inputs.data.new(B, T).zero_())
def init_states(self, inputs):
B = inputs.shape[0]
T = inputs.shape[1]
self.attention_weights = Variable(inputs.data.new(B, T).zero_())
if self.location_attention:
self.init_location_attention(inputs)
if self.forward_attn:
self.init_forward_attn(inputs)
if self.windowing:
self.init_win_idx()
def update_location_attention(self, alignments):
self.attention_weights_cum += alignments
def get_location_attention(self, query, processed_inputs):
attention_cat = torch.cat((self.attention_weights.unsqueeze(1),
self.attention_weights_cum.unsqueeze(1)),
dim=1)
processed_query = self.query_layer(query.unsqueeze(1))
processed_attention_weights = self.location_layer(attention_cat)
energies = self.v(
torch.tanh(processed_query + processed_attention_weights +
processed_inputs))
energies = energies.squeeze(-1)
return energies, processed_query
def get_attention(self, query, processed_inputs):
processed_query = self.query_layer(query.unsqueeze(1))
energies = self.v(torch.tanh(processed_query + processed_inputs))
energies = energies.squeeze(-1)
return energies, processed_query
def apply_windowing(self, attention, inputs):
back_win = self.win_idx - self.win_back
front_win = self.win_idx + self.win_front
if back_win > 0:
attention[:, :back_win] = -float("inf")
if front_win < inputs.shape[1]:
attention[:, front_win:] = -float("inf")
# this is a trick to solve a special problem.
# but it does not hurt.
if self.win_idx == -1:
attention[:, 0] = attention.max()
# Update the window
self.win_idx = torch.argmax(attention, 1).long()[0].item()
return attention
def apply_forward_attention(self, alignment):
# forward attention
fwd_shifted_alpha = F.pad(self.alpha[:, :-1].clone().to(alignment.device),
(1, 0, 0, 0))
# compute transition potentials
alpha = ((1 - self.u) * self.alpha
+ self.u * fwd_shifted_alpha
+ 1e-8) * alignment
# force incremental alignment
if not self.training and self.forward_attn_mask:
_, n = fwd_shifted_alpha.max(1)
val, n2 = alpha.max(1)
for b in range(alignment.shape[0]):
alpha[b, n[b] + 3:] = 0
alpha[b, :(
n[b] - 1
)] = 0 # ignore all previous states to prevent repetition.
alpha[b,
(n[b] - 2
)] = 0.01 * val[b] # smoothing factor for the prev step
# renormalize attention weights
alpha = alpha / alpha.sum(dim=1, keepdim=True)
return alpha
def forward(self, query, inputs, processed_inputs, mask):
if self.location_attention:
attention, _ = self.get_location_attention(
query, processed_inputs)
else:
attention, _ = self.get_attention(
query, processed_inputs)
# apply masking
if mask is not None:
attention.data.masked_fill_(~mask, self._mask_value)
# apply windowing - only in eval mode
if not self.training and self.windowing:
attention = self.apply_windowing(attention, inputs)
# normalize attention values
if self.norm == "softmax":
alignment = torch.softmax(attention, dim=-1)
elif self.norm == "sigmoid":
alignment = torch.sigmoid(attention) / torch.sigmoid(
attention).sum(
dim=1, keepdim=True)
else:
raise ValueError("Unknown value for attention norm type")
if self.location_attention:
self.update_location_attention(alignment)
# apply forward attention if enabled
if self.forward_attn:
alignment = self.apply_forward_attention(alignment)
self.alpha = alignment
context = torch.bmm(alignment.unsqueeze(1), inputs)
context = context.squeeze(1)
self.attention_weights = alignment
# compute transition agent
if self.forward_attn and self.trans_agent:
ta_input = torch.cat([context, query.squeeze(1)], dim=-1)
self.u = torch.sigmoid(self.ta(ta_input))
return context