# Copyright (c) 2017-present, Facebook, Inc.
# All rights reserved.
#
# This source code is licensed under the license found in the LICENSE file in
# the root directory of this source tree. An additional grant of patent rights
# can be found in the PATENTS file in the same directory.
import torch
import torch.nn as nn
import torch.nn.functional as F
from fairseq import utils
from fairseq.modules.unfold import unfold1d
class LightweightConv1d(nn.Module):
'''Lightweight Convolution assuming the input is BxCxT
This is just an example that explains LightConv clearer than the TBC version.
We don't use this module in the model.
Args:
input_size: # of channels of the input and output
kernel_size: convolution channels
padding: padding
num_heads: number of heads used. The weight is of shape
`(num_heads, 1, kernel_size)`
weight_softmax: normalize the weight with softmax before the convolution
Shape:
Input: BxCxT, i.e. (batch_size, input_size, timesteps)
Output: BxCxT, i.e. (batch_size, input_size, timesteps)
Attributes:
weight: the learnable weights of the module of shape
`(num_heads, 1, kernel_size)`
bias: the learnable bias of the module of shape `(input_size)`
'''
def __init__(self, input_size, kernel_size=1, padding=0, num_heads=1,
weight_softmax=False, bias=False, weight_dropout=0.):
super().__init__()
self.input_size = input_size
self.kernel_size = kernel_size
self.num_heads = num_heads
self.padding = padding
self.weight_softmax = weight_softmax
self.weight = nn.Parameter(torch.Tensor(num_heads, 1, kernel_size))
if bias:
self.bias = nn.Parameter(torch.Tensor(input_size))
else:
self.bias = None
self.weight_dropout = weight_dropout
self.reset_parameters()
def reset_parameters(self):
nn.init.xavier_uniform_(self.weight)
if self.bias is not None:
nn.init.constant_(self.bias, 0.)
def forward(self, input):
'''
input size: B x C x T
output size: B x C x T
'''
B, C, T = input.size()
H = self.num_heads
weight = self.weight
if self.weight_softmax:
weight = F.softmax(weight, dim=-1)
weight = F.dropout(weight, self.weight_dropout, training=self.training)
# Merge every C/H entries into the batch dimension (C = self.input_size)
# B x C x T -> (B * C/H) x H x T
# One can also expand the weight to C x 1 x K by a factor of C/H
# and do not reshape the input instead, which is slow though
input = input.view(-1, H, T)
output = F.conv1d(input, weight, padding=self.padding, groups=self.num_heads)
output = output.view(B, C, T)
if self.bias is not None:
output = output + self.bias.view(1, -1, 1)
return output
[docs]class LightweightConv1dTBC(nn.Module):
'''Lightweight Convolution assuming the input is TxBxC
Args:
input_size: # of channels of the input
kernel_size: convolution channels
padding_l: padding to the left when using "same" padding
num_heads: number of heads used. The weight is of shape (num_heads, 1, kernel_size)
weight_dropout: the drop rate of the DropConnect to drop the weight
weight_softmax: normalize the weight with softmax before the convolution
bias: use bias
Shape:
Input: TxBxC, i.e. (timesteps, batch_size, input_size)
Output: TxBxC, i.e. (timesteps, batch_size, input_size)
Attributes:
weight: the learnable weights of the module of shape
`(num_heads, 1, kernel_size)`
bias: the learnable bias of the module of shape `(input_size)`
'''
def __init__(self, input_size, kernel_size=1, padding_l=None, num_heads=1,
weight_dropout=0., weight_softmax=False, bias=False):
super().__init__()
self.input_size = input_size
self.kernel_size = kernel_size
self.padding_l = padding_l
self.num_heads = num_heads
self.weight_dropout = weight_dropout
self.weight_softmax = weight_softmax
self.weight = nn.Parameter(torch.Tensor(num_heads, 1, kernel_size))
if bias:
self.bias = nn.Parameter(torch.Tensor(input_size))
else:
self.bias = None
self.reset_parameters()
self.onnx_trace = False
[docs] def reset_parameters(self):
nn.init.xavier_uniform_(self.weight)
if self.bias is not None:
nn.init.constant_(self.bias, 0.)
[docs] def forward(self, x, incremental_state=None, unfold=False):
'''Assuming the input, x, of the shape T x B x C and producing an output in the shape T x B x C
args:
x: Input of shape T x B x C, i.e. (timesteps, batch_size, input_size)
incremental_state: A dict to keep the state
unfold: unfold the input or not. If not, we use the matrix trick instead
'''
unfold = unfold or (incremental_state is not None)
if unfold:
output = self._forward_unfolded(x, incremental_state)
else:
output = self._forward_expanded(x, incremental_state)
if self.bias is not None:
output = output + self.bias.view(1, 1, -1)
return output
[docs] def prepare_for_onnx_export_(self):
self.onnx_trace = True
def _forward_unfolded(self, x, incremental_state):
'''The conventional implementation of convolutions.
Unfolding the input by having a window shifting to the right.'''
T, B, C = x.size()
K, H = self.kernel_size, self.num_heads
R = C // H
assert R * H == C == self.input_size
weight = self.weight.view(H, K)
if incremental_state is not None:
input_buffer = self._get_input_buffer(incremental_state)
if input_buffer is None:
input_buffer = x.new()
x_unfold = torch.cat([input_buffer, x.unsqueeze(3)], dim=3)
if self.kernel_size > 1:
self._set_input_buffer(incremental_state, x_unfold[:, :, :, -self.kernel_size+1:])
x_unfold = x_unfold.view(T*B*H, R, -1)
else:
# unfold the input: T x B x C --> T' x B x C x K
x_unfold = unfold1d(x, self.kernel_size, self.padding_l, 0)
x_unfold = x_unfold.view(T*B*H, R, K)
if self.weight_softmax:
weight = utils.softmax(weight, dim=1, onnx_trace=self.onnx_trace).type_as(weight)
if incremental_state is not None:
weight = weight[:, -x_unfold.size(2):]
K = weight.size(1)
weight = weight.view(1, H, K).expand(T*B, H, K).contiguous().view(T*B*H, K, 1)
weight = F.dropout(weight, self.weight_dropout, training=self.training)
output = torch.bmm(x_unfold, weight) # T*B*H x R x 1
output = output.view(T, B, C)
return output
def _forward_expanded(self, x, incremental_state):
'''Turn the convolution filters into band matrices and do matrix multiplication.
This is faster when the sequence is short, but less memory efficient.
This is not used in the decoder during inference.
'''
T, B, C = x.size()
K, H = self.kernel_size, self.num_heads
R = C // H
assert R * H == C == self.input_size
weight = self.weight.view(H, K)
if self.weight_softmax:
weight = utils.softmax(weight, dim=1, onnx_trace=self.onnx_trace).type_as(weight)
weight = weight.view(1, H, K).expand(T*B, H, K).contiguous()
weight = weight.view(T, B*H, K).transpose(0, 1)
x = x.view(T, B*H, R).transpose(0, 1)
P = self.padding_l
if K > T and P == K-1:
weight = weight.narrow(2, K-T, T)
K, P = T, T-1
# turn the convolution filters into band matrices
weight_expanded = weight.new_zeros(B*H, T, T+K-1, requires_grad=False)
weight_expanded.as_strided((B*H, T, K), (T*(T+K-1), T+K, 1)).copy_(weight)
weight_expanded = weight_expanded.narrow(2, P, T)
weight_expanded = F.dropout(weight_expanded, self.weight_dropout, training=self.training)
output = torch.bmm(weight_expanded, x)
output = output.transpose(0, 1).contiguous().view(T, B, C)
return output
[docs] def reorder_incremental_state(self, incremental_state, new_order):
input_buffer = self._get_input_buffer(incremental_state)
if input_buffer is not None:
input_buffer = input_buffer.index_select(1, new_order)
self._set_input_buffer(incremental_state, input_buffer)
def _get_input_buffer(self, incremental_state):
return utils.get_incremental_state(self, incremental_state, 'input_buffer')
def _set_input_buffer(self, incremental_state, new_buffer):
return utils.set_incremental_state(self, incremental_state, 'input_buffer', new_buffer)