import torch.nn as nn
import torch.utils.checkpoint as cp
from mmcv.cnn import build_conv_layer, build_norm_layer, constant_init
from ..builder import BACKBONES
from .resnet import Bottleneck as _Bottleneck
from .resnet import ResNet
class Bottleneck(_Bottleneck):
r"""Bottleneck for the ResNet backbone in `DetectoRS
<https://arxiv.org/pdf/2006.02334.pdf>`_.
This bottleneck allows the users to specify whether to use
SAC (Switchable Atrous Convolution) and RFP (Recursive Feature Pyramid).
Args:
inplanes (int): The number of input channels.
planes (int): The number of output channels before expansion.
rfp_inplanes (int, optional): The number of channels from RFP.
Default: None. If specified, an additional conv layer will be
added for ``rfp_feat``. Otherwise, the structure is the same as
base class.
sac (dict, optional): Dictionary to construct SAC. Default: None.
"""
expansion = 4
def __init__(self,
inplanes,
planes,
rfp_inplanes=None,
sac=None,
**kwargs):
super(Bottleneck, self).__init__(inplanes, planes, **kwargs)
assert sac is None or isinstance(sac, dict)
self.sac = sac
self.with_sac = sac is not None
if self.with_sac:
self.conv2 = build_conv_layer(
self.sac,
planes,
planes,
kernel_size=3,
stride=self.conv2_stride,
padding=self.dilation,
dilation=self.dilation,
bias=False)
self.rfp_inplanes = rfp_inplanes
if self.rfp_inplanes:
self.rfp_conv = build_conv_layer(
None,
self.rfp_inplanes,
planes * self.expansion,
1,
stride=1,
bias=True)
self.init_weights()
def init_weights(self):
"""Initialize the weights."""
if self.rfp_inplanes:
constant_init(self.rfp_conv, 0)
def rfp_forward(self, x, rfp_feat):
"""The forward function that also takes the RFP features as input."""
def _inner_forward(x):
identity = x
out = self.conv1(x)
out = self.norm1(out)
out = self.relu(out)
if self.with_plugins:
out = self.forward_plugin(out, self.after_conv1_plugin_names)
out = self.conv2(out)
out = self.norm2(out)
out = self.relu(out)
if self.with_plugins:
out = self.forward_plugin(out, self.after_conv2_plugin_names)
out = self.conv3(out)
out = self.norm3(out)
if self.with_plugins:
out = self.forward_plugin(out, self.after_conv3_plugin_names)
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)
if self.rfp_inplanes:
rfp_feat = self.rfp_conv(rfp_feat)
out = out + rfp_feat
out = self.relu(out)
return out
class ResLayer(nn.Sequential):
"""ResLayer to build ResNet style backbone for RPF in detectoRS.
The difference between this module and base class is that we pass
``rfp_inplanes`` to the first block.
Args:
block (nn.Module): block used to build ResLayer.
inplanes (int): inplanes of block.
planes (int): planes of block.
num_blocks (int): number of blocks.
stride (int): stride of the first block. Default: 1
avg_down (bool): Use AvgPool instead of stride conv when
downsampling in the bottleneck. Default: False
conv_cfg (dict): dictionary to construct and config conv layer.
Default: None
norm_cfg (dict): dictionary to construct and config norm layer.
Default: dict(type='BN')
downsample_first (bool): Downsample at the first block or last block.
False for Hourglass, True for ResNet. Default: True
rfp_inplanes (int, optional): The number of channels from RFP.
Default: None. If specified, an additional conv layer will be
added for ``rfp_feat``. Otherwise, the structure is the same as
base class.
"""
def __init__(self,
block,
inplanes,
planes,
num_blocks,
stride=1,
avg_down=False,
conv_cfg=None,
norm_cfg=dict(type='BN'),
downsample_first=True,
rfp_inplanes=None,
**kwargs):
self.block = block
assert downsample_first, f'downsampel_first={downsample_first} is ' \
'not supported in DetectoRS'
downsample = None
if stride != 1 or inplanes != planes * block.expansion:
downsample = []
conv_stride = stride
if avg_down and stride != 1:
conv_stride = 1
downsample.append(
nn.AvgPool2d(
kernel_size=stride,
stride=stride,
ceil_mode=True,
count_include_pad=False))
downsample.extend([
build_conv_layer(
conv_cfg,
inplanes,
planes * block.expansion,
kernel_size=1,
stride=conv_stride,
bias=False),
build_norm_layer(norm_cfg, planes * block.expansion)[1]
])
downsample = nn.Sequential(*downsample)
layers = []
layers.append(
block(
inplanes=inplanes,
planes=planes,
stride=stride,
downsample=downsample,
conv_cfg=conv_cfg,
norm_cfg=norm_cfg,
rfp_inplanes=rfp_inplanes,
**kwargs))
inplanes = planes * block.expansion
for _ in range(1, num_blocks):
layers.append(
block(
inplanes=inplanes,
planes=planes,
stride=1,
conv_cfg=conv_cfg,
norm_cfg=norm_cfg,
**kwargs))
super(ResLayer, self).__init__(*layers)
[docs]@BACKBONES.register_module()
class DetectoRS_ResNet(ResNet):
"""ResNet backbone for DetectoRS.
Args:
sac (dict, optional): Dictionary to construct SAC (Switchable Atrous
Convolution). Default: None.
stage_with_sac (list): Which stage to use sac. Default: (False, False,
False, False).
rfp_inplanes (int, optional): The number of channels from RFP.
Default: None. If specified, an additional conv layer will be
added for ``rfp_feat``. Otherwise, the structure is the same as
base class.
output_img (bool): If ``True``, the input image will be inserted into
the starting position of output. Default: False.
pretrained (str, optional): The pretrained model to load.
"""
arch_settings = {
50: (Bottleneck, (3, 4, 6, 3)),
101: (Bottleneck, (3, 4, 23, 3)),
152: (Bottleneck, (3, 8, 36, 3))
}
def __init__(self,
sac=None,
stage_with_sac=(False, False, False, False),
rfp_inplanes=None,
output_img=False,
pretrained=None,
**kwargs):
self.sac = sac
self.stage_with_sac = stage_with_sac
self.rfp_inplanes = rfp_inplanes
self.output_img = output_img
self.pretrained = pretrained
super(DetectoRS_ResNet, self).__init__(**kwargs)
self.inplanes = self.stem_channels
self.res_layers = []
for i, num_blocks in enumerate(self.stage_blocks):
stride = self.strides[i]
dilation = self.dilations[i]
dcn = self.dcn if self.stage_with_dcn[i] else None
sac = self.sac if self.stage_with_sac[i] else None
if self.plugins is not None:
stage_plugins = self.make_stage_plugins(self.plugins, i)
else:
stage_plugins = None
planes = self.base_channels * 2**i
res_layer = self.make_res_layer(
block=self.block,
inplanes=self.inplanes,
planes=planes,
num_blocks=num_blocks,
stride=stride,
dilation=dilation,
style=self.style,
avg_down=self.avg_down,
with_cp=self.with_cp,
conv_cfg=self.conv_cfg,
norm_cfg=self.norm_cfg,
dcn=dcn,
sac=sac,
rfp_inplanes=rfp_inplanes if i > 0 else None,
plugins=stage_plugins)
self.inplanes = planes * self.block.expansion
layer_name = f'layer{i + 1}'
self.add_module(layer_name, res_layer)
self.res_layers.append(layer_name)
self._freeze_stages()
[docs] def make_res_layer(self, **kwargs):
"""Pack all blocks in a stage into a ``ResLayer`` for DetectoRS."""
return ResLayer(**kwargs)
[docs] def forward(self, x):
"""Forward function."""
outs = list(super(DetectoRS_ResNet, self).forward(x))
if self.output_img:
outs.insert(0, x)
return tuple(outs)
[docs] def rfp_forward(self, x, rfp_feats):
"""Forward function for RFP."""
if self.deep_stem:
x = self.stem(x)
else:
x = self.conv1(x)
x = self.norm1(x)
x = self.relu(x)
x = self.maxpool(x)
outs = []
for i, layer_name in enumerate(self.res_layers):
res_layer = getattr(self, layer_name)
rfp_feat = rfp_feats[i] if i > 0 else None
for layer in res_layer:
x = layer.rfp_forward(x, rfp_feat)
if i in self.out_indices:
outs.append(x)
return tuple(outs)