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# Copyright (c) OpenMMLab. All rights reserved.
import torch.utils.checkpoint as cp
from ..builder import BACKBONES
from .resnet import Bottleneck, ResLayer, ResNet
from .utils.se_layer import SELayer
class SEBottleneck(Bottleneck):
"""SEBottleneck block for SEResNet.
Args:
in_channels (int): The input channels of the SEBottleneck block.
out_channels (int): The output channel of the SEBottleneck block.
se_ratio (int): Squeeze ratio in SELayer. Default: 16
"""
def __init__(self, in_channels, out_channels, se_ratio=16, **kwargs):
super().__init__(in_channels, out_channels, **kwargs)
self.se_layer = SELayer(out_channels, ratio=se_ratio)
def forward(self, x):
def _inner_forward(x):
identity = x
out = self.conv1(x)
out = self.norm1(out)
out = self.relu(out)
out = self.conv2(out)
out = self.norm2(out)
out = self.relu(out)
out = self.conv3(out)
out = self.norm3(out)
out = self.se_layer(out)
if self.downsample is not None:
identity = self.downsample(x)
out += identity
return out
if self.with_cp and x.requires_grad:
out = cp.checkpoint(_inner_forward, x)
else:
out = _inner_forward(x)
out = self.relu(out)
return out
@BACKBONES.register_module()
class SEResNet(ResNet):
"""SEResNet backbone.
Please refer to the `paper <https://arxiv.org/abs/1709.01507>`__ for
details.
Args:
depth (int): Network depth, from {50, 101, 152}.
se_ratio (int): Squeeze ratio in SELayer. Default: 16.
in_channels (int): Number of input image channels. Default: 3.
stem_channels (int): Output channels of the stem layer. Default: 64.
num_stages (int): Stages of the network. Default: 4.
strides (Sequence[int]): Strides of the first block of each stage.
Default: ``(1, 2, 2, 2)``.
dilations (Sequence[int]): Dilation of each stage.
Default: ``(1, 1, 1, 1)``.
out_indices (Sequence[int]): Output from which stages. If only one
stage is specified, a single tensor (feature map) is returned,
otherwise multiple stages are specified, a tuple of tensors will
be returned. Default: ``(3, )``.
style (str): `pytorch` or `caffe`. If set to "pytorch", the stride-two
layer is the 3x3 conv layer, otherwise the stride-two layer is
the first 1x1 conv layer.
deep_stem (bool): Replace 7x7 conv in input stem with 3 3x3 conv.
Default: False.
avg_down (bool): Use AvgPool instead of stride conv when
downsampling in the bottleneck. Default: False.
frozen_stages (int): Stages to be frozen (stop grad and set eval mode).
-1 means not freezing any parameters. Default: -1.
conv_cfg (dict | None): The config dict for conv layers. Default: None.
norm_cfg (dict): The config dict for norm layers.
norm_eval (bool): Whether to set norm layers to eval mode, namely,
freeze running stats (mean and var). Note: Effect on Batch Norm
and its variants only. Default: False.
with_cp (bool): Use checkpoint or not. Using checkpoint will save some
memory while slowing down the training speed. Default: False.
zero_init_residual (bool): Whether to use zero init for last norm layer
in resblocks to let them behave as identity. Default: True.
Example:
>>> from mmpose.models import SEResNet
>>> import torch
>>> self = SEResNet(depth=50, out_indices=(0, 1, 2, 3))
>>> self.eval()
>>> inputs = torch.rand(1, 3, 224, 224)
>>> level_outputs = self.forward(inputs)
>>> for level_out in level_outputs:
... print(tuple(level_out.shape))
(1, 256, 56, 56)
(1, 512, 28, 28)
(1, 1024, 14, 14)
(1, 2048, 7, 7)
"""
arch_settings = {
50: (SEBottleneck, (3, 4, 6, 3)),
101: (SEBottleneck, (3, 4, 23, 3)),
152: (SEBottleneck, (3, 8, 36, 3))
}
def __init__(self, depth, se_ratio=16, **kwargs):
if depth not in self.arch_settings:
raise KeyError(f'invalid depth {depth} for SEResNet')
self.se_ratio = se_ratio
super().__init__(depth, **kwargs)
def make_res_layer(self, **kwargs):
return ResLayer(se_ratio=self.se_ratio, **kwargs)
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