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import torch.nn as nn
import torch.nn.functional as F
import numpy as np
from .Modules import ScaledDotProductAttention
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)
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)
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, kernel_size, dropout=0.1):
super().__init__()
# Use Conv1D
# position-wise
self.w_1 = nn.Conv1d(
d_in,
d_hid,
kernel_size=kernel_size[0],
padding=(kernel_size[0] - 1) // 2,
)
# position-wise
self.w_2 = nn.Conv1d(
d_hid,
d_in,
kernel_size=kernel_size[1],
padding=(kernel_size[1] - 1) // 2,
)
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
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