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# Copyright (c) OpenMMLab. All rights reserved. | |
import torch.nn as nn | |
import torch.utils.checkpoint as cp | |
from mmcv.cnn import ConvModule | |
from mmcv.cnn.bricks import DropPath | |
from mmcv.runner import BaseModule | |
from .se_layer import SELayer | |
class InvertedResidual(BaseModule): | |
"""Inverted Residual Block. | |
Args: | |
in_channels (int): The input channels of this Module. | |
out_channels (int): The output channels of this Module. | |
mid_channels (int): The input channels of the depthwise convolution. | |
kernel_size (int): The kernel size of the depthwise convolution. | |
Default: 3. | |
stride (int): The stride of the depthwise convolution. Default: 1. | |
se_cfg (dict): Config dict for se layer. Default: None, which means no | |
se layer. | |
with_expand_conv (bool): Use expand conv or not. If set False, | |
mid_channels must be the same with in_channels. | |
Default: True. | |
conv_cfg (dict): Config dict for convolution layer. Default: None, | |
which means using conv2d. | |
norm_cfg (dict): Config dict for normalization layer. | |
Default: dict(type='BN'). | |
act_cfg (dict): Config dict for activation layer. | |
Default: dict(type='ReLU'). | |
drop_path_rate (float): stochastic depth rate. Defaults to 0. | |
with_cp (bool): Use checkpoint or not. Using checkpoint will save some | |
memory while slowing down the training speed. Default: False. | |
init_cfg (dict or list[dict], optional): Initialization config dict. | |
Default: None | |
Returns: | |
Tensor: The output tensor. | |
""" | |
def __init__(self, | |
in_channels, | |
out_channels, | |
mid_channels, | |
kernel_size=3, | |
stride=1, | |
se_cfg=None, | |
with_expand_conv=True, | |
conv_cfg=None, | |
norm_cfg=dict(type='BN'), | |
act_cfg=dict(type='ReLU'), | |
drop_path_rate=0., | |
with_cp=False, | |
init_cfg=None): | |
super(InvertedResidual, self).__init__(init_cfg) | |
self.with_res_shortcut = (stride == 1 and in_channels == out_channels) | |
assert stride in [1, 2], f'stride must in [1, 2]. ' \ | |
f'But received {stride}.' | |
self.with_cp = with_cp | |
self.drop_path = DropPath( | |
drop_path_rate) if drop_path_rate > 0 else nn.Identity() | |
self.with_se = se_cfg is not None | |
self.with_expand_conv = with_expand_conv | |
if self.with_se: | |
assert isinstance(se_cfg, dict) | |
if not self.with_expand_conv: | |
assert mid_channels == in_channels | |
if self.with_expand_conv: | |
self.expand_conv = ConvModule( | |
in_channels=in_channels, | |
out_channels=mid_channels, | |
kernel_size=1, | |
stride=1, | |
padding=0, | |
conv_cfg=conv_cfg, | |
norm_cfg=norm_cfg, | |
act_cfg=act_cfg) | |
self.depthwise_conv = ConvModule( | |
in_channels=mid_channels, | |
out_channels=mid_channels, | |
kernel_size=kernel_size, | |
stride=stride, | |
padding=kernel_size // 2, | |
groups=mid_channels, | |
conv_cfg=conv_cfg, | |
norm_cfg=norm_cfg, | |
act_cfg=act_cfg) | |
if self.with_se: | |
self.se = SELayer(**se_cfg) | |
self.linear_conv = ConvModule( | |
in_channels=mid_channels, | |
out_channels=out_channels, | |
kernel_size=1, | |
stride=1, | |
padding=0, | |
conv_cfg=conv_cfg, | |
norm_cfg=norm_cfg, | |
act_cfg=None) | |
def forward(self, x): | |
def _inner_forward(x): | |
out = x | |
if self.with_expand_conv: | |
out = self.expand_conv(out) | |
out = self.depthwise_conv(out) | |
if self.with_se: | |
out = self.se(out) | |
out = self.linear_conv(out) | |
if self.with_res_shortcut: | |
return x + self.drop_path(out) | |
else: | |
return out | |
if self.with_cp and x.requires_grad: | |
out = cp.checkpoint(_inner_forward, x) | |
else: | |
out = _inner_forward(x) | |
return out | |