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# Copyright (c) 2023 Amphion. | |
# | |
# This source code is licensed under the MIT license found in the | |
# LICENSE file in the root directory of this source tree. | |
import torch | |
import torch.nn as nn | |
import math | |
class SinePositionalEmbedding(nn.Module): | |
def __init__( | |
self, | |
dim_model: int, | |
dropout: float = 0.0, | |
scale: bool = False, | |
alpha: bool = False, | |
): | |
super().__init__() | |
self.dim_model = dim_model | |
self.x_scale = math.sqrt(dim_model) if scale else 1.0 | |
self.alpha = nn.Parameter(torch.ones(1), requires_grad=alpha) | |
self.dropout = torch.nn.Dropout(p=dropout) | |
self.reverse = False | |
self.pe = None | |
self.extend_pe(torch.tensor(0.0).expand(1, 4000)) | |
def extend_pe(self, x): | |
"""Reset the positional encodings.""" | |
if self.pe is not None: | |
if self.pe.size(1) >= x.size(1): | |
if self.pe.dtype != x.dtype or self.pe.device != x.device: | |
self.pe = self.pe.to(dtype=x.dtype, device=x.device) | |
return | |
pe = torch.zeros(x.size(1), self.dim_model) | |
if self.reverse: | |
position = torch.arange( | |
x.size(1) - 1, -1, -1.0, dtype=torch.float32 | |
).unsqueeze(1) | |
else: | |
position = torch.arange( | |
0, x.size(1), dtype=torch.float32 | |
).unsqueeze(1) | |
div_term = torch.exp( | |
torch.arange(0, self.dim_model, 2, dtype=torch.float32) | |
* -(math.log(10000.0) / self.dim_model) | |
) | |
pe[:, 0::2] = torch.sin(position * div_term) | |
pe[:, 1::2] = torch.cos(position * div_term) | |
pe = pe.unsqueeze(0) | |
self.pe = pe.to(device=x.device, dtype=x.dtype).detach() | |
def forward(self, x: torch.Tensor) -> torch.Tensor: | |
self.extend_pe(x) | |
output = x.unsqueeze(-1) if x.ndim == 2 else x | |
output = output * self.x_scale + self.alpha * self.pe[:, : x.size(1)] | |
return self.dropout(output) | |
# import torch | |
# import torch.nn as nn | |
# import math | |
# class SinePositionalEmbedding(nn.Module): | |
# def __init__( | |
# self, | |
# dim_model: int, | |
# dropout: float = 0.0, | |
# scale: bool = False, | |
# alpha: bool = False, | |
# ): | |
# super().__init__() | |
# self.dim_model = dim_model | |
# self.x_scale = math.sqrt(dim_model) if scale else 1.0 | |
# self.alpha = nn.Parameter(torch.ones(1), requires_grad=alpha) | |
# self.dropout = torch.nn.Dropout(p=dropout) | |
# self.reverse = False | |
# self.pe = None | |
# self.extend_pe(torch.zeros(1, 4000)) | |
# def extend_pe(self, x): | |
# """Reset the positional encodings.""" | |
# if self._pe_needs_extension(x): | |
# self.pe = self._generate_positional_encodings(x) | |
# def _pe_needs_extension(self, x): | |
# return self.pe is None or self.pe.size(1) < x.size(1) or self.pe.dtype != x.dtype or self.pe.device != x.device | |
# def _generate_positional_encodings(self, x): | |
# pe = torch.zeros(x.size(1), self.dim_model) | |
# position = self._get_position_tensor(x) | |
# div_term = self._get_div_term() | |
# pe[:, 0::2] = torch.sin(position * div_term) | |
# pe[:, 1::2] = torch.cos(position * div_term) | |
# return pe.unsqueeze(0).to(device=x.device, dtype=x.dtype).detach() | |
# def _get_position_tensor(self, x): | |
# position = torch.arange(x.size(1), dtype=torch.float32).unsqueeze(1) | |
# return position.flip(0) if self.reverse else position | |
# def _get_div_term(self): | |
# return torch.exp(torch.arange(0, self.dim_model, 2, dtype=torch.float32) * -(math.log(10000.0) / self.dim_model)) | |
# def forward(self, x: torch.Tensor) -> torch.Tensor: | |
# self.extend_pe(x) | |
# output = x.unsqueeze(-1) if x.ndim == 2 else x | |
# output = output * self.x_scale + self.alpha * self.pe[:, : x.size(1)] | |
# return self.dropout(output) | |