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""" Embeddings module """
import math
import warnings
import torch
import torch.nn as nn
class PositionalEncoding(nn.Module):
"""Sinusoidal positional encoding for non-recurrent neural networks.
Implementation based on "Attention Is All You Need"
:cite:`DBLP:journals/corr/VaswaniSPUJGKP17`
Args:
dropout (float): dropout parameter
dim (int): embedding size
"""
def __init__(self, dropout, dim, max_len=5000):
if dim % 2 != 0:
raise ValueError("Cannot use sin/cos positional encoding with "
"odd dim (got dim={:d})".format(dim))
pe = torch.zeros(max_len, dim)
position = torch.arange(0, max_len).unsqueeze(1)
div_term = torch.exp((torch.arange(0, dim, 2, dtype=torch.float) *
-(math.log(10000.0) / dim)))
pe[:, 0::2] = torch.sin(position.float() * div_term)
pe[:, 1::2] = torch.cos(position.float() * div_term)
pe = pe.unsqueeze(1)
super(PositionalEncoding, self).__init__()
self.register_buffer('pe', pe)
self.dropout = nn.Dropout(p=dropout)
self.dim = dim
def forward(self, emb, step=None):
"""Embed inputs.
Args:
emb (FloatTensor): Sequence of word vectors
``(seq_len, batch_size, self.dim)``
step (int or NoneType): If stepwise (``seq_len = 1``), use
the encoding for this position.
"""
emb = emb * math.sqrt(self.dim)
if step is None:
emb = emb + self.pe[:emb.size(0)]
else:
emb = emb + self.pe[step]
emb = self.dropout(emb)
return emb
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