import torch.nn as nn
|
|
import torch.nn.functional as F
|
|
import numpy as np
|
|
|
|
from transformer.Modules import ScaledDotProductAttention
|
|
import hparams as hp
|
|
|
|
|
|
class MultiHeadAttention(nn.Module):
|
|
''' Multi-Head Attention module '''
|
|
|
|
def __init__(self, n_head, d_model, d_k, d_v, dropout=0.1):
|
|
super().__init__()
|
|
|
|
self.n_head = n_head
|
|
self.d_k = d_k
|
|
self.d_v = d_v
|
|
|
|
self.w_qs = nn.Linear(d_model, n_head * d_k)
|
|
self.w_ks = nn.Linear(d_model, n_head * d_k)
|
|
self.w_vs = nn.Linear(d_model, n_head * d_v)
|
|
nn.init.normal_(self.w_qs.weight, mean=0,
|
|
std=np.sqrt(2.0 / (d_model + d_k)))
|
|
nn.init.normal_(self.w_ks.weight, mean=0,
|
|
std=np.sqrt(2.0 / (d_model + d_k)))
|
|
nn.init.normal_(self.w_vs.weight, mean=0,
|
|
std=np.sqrt(2.0 / (d_model + d_v)))
|
|
|
|
self.attention = ScaledDotProductAttention(
|
|
temperature=np.power(d_k, 0.5))
|
|
self.layer_norm = nn.LayerNorm(d_model)
|
|
|
|
self.fc = nn.Linear(n_head * d_v, d_model)
|
|
nn.init.xavier_normal_(self.fc.weight)
|
|
|
|
self.dropout = nn.Dropout(dropout)
|
|
|
|
def forward(self, q, k, v, mask=None):
|
|
|
|
d_k, d_v, n_head = self.d_k, self.d_v, self.n_head
|
|
|
|
sz_b, len_q, _ = q.size()
|
|
sz_b, len_k, _ = k.size()
|
|
sz_b, len_v, _ = v.size()
|
|
|
|
residual = q
|
|
|
|
q = self.w_qs(q).view(sz_b, len_q, n_head, d_k)
|
|
k = self.w_ks(k).view(sz_b, len_k, n_head, d_k)
|
|
v = self.w_vs(v).view(sz_b, len_v, n_head, d_v)
|
|
|
|
q = q.permute(2, 0, 1, 3).contiguous().view(-1,
|
|
len_q, d_k) # (n*b) x lq x dk
|
|
k = k.permute(2, 0, 1, 3).contiguous().view(-1,
|
|
len_k, d_k) # (n*b) x lk x dk
|
|
v = v.permute(2, 0, 1, 3).contiguous().view(-1,
|
|
len_v, d_v) # (n*b) x lv x dv
|
|
|
|
mask = mask.repeat(n_head, 1, 1) # (n*b) x .. x ..
|
|
output, attn = self.attention(q, k, v, mask=mask)
|
|
|
|
output = output.view(n_head, sz_b, len_q, d_v)
|
|
output = output.permute(1, 2, 0, 3).contiguous().view(
|
|
sz_b, len_q, -1) # b x lq x (n*dv)
|
|
|
|
output = self.dropout(self.fc(output))
|
|
output = self.layer_norm(output + residual)
|
|
|
|
return output, attn
|
|
|
|
|
|
class PositionwiseFeedForward(nn.Module):
|
|
''' A two-feed-forward-layer module '''
|
|
|
|
def __init__(self, d_in, d_hid, dropout=0.1):
|
|
super().__init__()
|
|
|
|
# Use Conv1D
|
|
# position-wise
|
|
self.w_1 = nn.Conv1d(
|
|
d_in, d_hid, kernel_size=hp.fft_conv1d_kernel, padding=hp.fft_conv1d_padding)
|
|
# position-wise
|
|
self.w_2 = nn.Conv1d(
|
|
d_hid, d_in, kernel_size=hp.fft_conv1d_kernel, padding=hp.fft_conv1d_padding)
|
|
|
|
self.layer_norm = nn.LayerNorm(d_in)
|
|
self.dropout = nn.Dropout(dropout)
|
|
|
|
def forward(self, x):
|
|
residual = x
|
|
output = x.transpose(1, 2)
|
|
output = self.w_2(F.relu(self.w_1(output)))
|
|
output = output.transpose(1, 2)
|
|
output = self.dropout(output)
|
|
output = self.layer_norm(output + residual)
|
|
|
|
return output
|