import warnings
import torch.nn as nn
import torch.utils.checkpoint as cp
from mmcv.cnn import build_conv_layer, build_norm_layer, build_plugin_layer
from mmcv.runner import BaseModule
from mmcv.utils.parrots_wrapper import _BatchNorm
from ..builder import BACKBONES
from ..utils import ResLayer
class BasicBlock(BaseModule):
"""Basic block for ResNet."""
expansion = 1
def __init__(self,
inplanes,
planes,
stride=1,
dilation=1,
downsample=None,
style='pytorch',
with_cp=False,
conv_cfg=None,
norm_cfg=dict(type='BN'),
dcn=None,
plugins=None,
init_cfg=None):
super(BasicBlock, self).__init__(init_cfg)
assert dcn is None, 'Not implemented yet.'
assert plugins is None, 'Not implemented yet.'
self.norm1_name, norm1 = build_norm_layer(norm_cfg, planes, postfix=1)
self.norm2_name, norm2 = build_norm_layer(norm_cfg, planes, postfix=2)
self.conv1 = build_conv_layer(
conv_cfg,
inplanes,
planes,
3,
stride=stride,
padding=dilation,
dilation=dilation,
bias=False)
self.add_module(self.norm1_name, norm1)
self.conv2 = build_conv_layer(
conv_cfg, planes, planes, 3, padding=1, bias=False)
self.add_module(self.norm2_name, norm2)
self.relu = nn.ReLU(inplace=True)
self.downsample = downsample
self.stride = stride
self.dilation = dilation
self.with_cp = with_cp
@property
def norm1(self):
"""nn.Module: normalization layer after the first convolution layer"""
return getattr(self, self.norm1_name)
@property
def norm2(self):
"""nn.Module: normalization layer after the second convolution layer"""
return getattr(self, self.norm2_name)
def forward(self, x):
"""Forward function."""
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)
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
class Bottleneck(BaseModule):
"""Bottleneck block for ResNet.
If style is "pytorch", the stride-two layer is the 3x3 conv layer, if it is
"caffe", the stride-two layer is the first 1x1 conv layer.
"""
expansion = 4
def __init__(self,
inplanes,
planes,
stride=1,
dilation=1,
downsample=None,
style='pytorch',
with_cp=False,
conv_cfg=None,
norm_cfg=dict(type='BN'),
dcn=None,
plugins=None,
init_cfg=None):
super(Bottleneck, self).__init__(init_cfg)
assert style in ['pytorch', 'caffe']
assert dcn is None or isinstance(dcn, dict)
assert plugins is None or isinstance(plugins, list)
if plugins is not None:
allowed_position = ['after_conv1', 'after_conv2', 'after_conv3']
assert all(p['position'] in allowed_position for p in plugins)
self.inplanes = inplanes
self.planes = planes
self.stride = stride
self.dilation = dilation
self.style = style
self.with_cp = with_cp
self.conv_cfg = conv_cfg
self.norm_cfg = norm_cfg
self.dcn = dcn
self.with_dcn = dcn is not None
self.plugins = plugins
self.with_plugins = plugins is not None
if self.with_plugins:
self.after_conv1_plugins = [
plugin['cfg'] for plugin in plugins
if plugin['position'] == 'after_conv1'
]
self.after_conv2_plugins = [
plugin['cfg'] for plugin in plugins
if plugin['position'] == 'after_conv2'
]
self.after_conv3_plugins = [
plugin['cfg'] for plugin in plugins
if plugin['position'] == 'after_conv3'
]
if self.style == 'pytorch':
self.conv1_stride = 1
self.conv2_stride = stride
else:
self.conv1_stride = stride
self.conv2_stride = 1
self.norm1_name, norm1 = build_norm_layer(norm_cfg, planes, postfix=1)
self.norm2_name, norm2 = build_norm_layer(norm_cfg, planes, postfix=2)
self.norm3_name, norm3 = build_norm_layer(
norm_cfg, planes * self.expansion, postfix=3)
self.conv1 = build_conv_layer(
conv_cfg,
inplanes,
planes,
kernel_size=1,
stride=self.conv1_stride,
bias=False)
self.add_module(self.norm1_name, norm1)
fallback_on_stride = False
if self.with_dcn:
fallback_on_stride = dcn.pop('fallback_on_stride', False)
if not self.with_dcn or fallback_on_stride:
self.conv2 = build_conv_layer(
conv_cfg,
planes,
planes,
kernel_size=3,
stride=self.conv2_stride,
padding=dilation,
dilation=dilation,
bias=False)
else:
assert self.conv_cfg is None, 'conv_cfg must be None for DCN'
self.conv2 = build_conv_layer(
dcn,
planes,
planes,
kernel_size=3,
stride=self.conv2_stride,
padding=dilation,
dilation=dilation,
bias=False)
self.add_module(self.norm2_name, norm2)
self.conv3 = build_conv_layer(
conv_cfg,
planes,
planes * self.expansion,
kernel_size=1,
bias=False)
self.add_module(self.norm3_name, norm3)
self.relu = nn.ReLU(inplace=True)
self.downsample = downsample
if self.with_plugins:
self.after_conv1_plugin_names = self.make_block_plugins(
planes, self.after_conv1_plugins)
self.after_conv2_plugin_names = self.make_block_plugins(
planes, self.after_conv2_plugins)
self.after_conv3_plugin_names = self.make_block_plugins(
planes * self.expansion, self.after_conv3_plugins)
def make_block_plugins(self, in_channels, plugins):
"""make plugins for block.
Args:
in_channels (int): Input channels of plugin.
plugins (list[dict]): List of plugins cfg to build.
Returns:
list[str]: List of the names of plugin.
"""
assert isinstance(plugins, list)
plugin_names = []
for plugin in plugins:
plugin = plugin.copy()
name, layer = build_plugin_layer(
plugin,
in_channels=in_channels,
postfix=plugin.pop('postfix', ''))
assert not hasattr(self, name), f'duplicate plugin {name}'
self.add_module(name, layer)
plugin_names.append(name)
return plugin_names
def forward_plugin(self, x, plugin_names):
"""Forward function for plugins."""
out = x
for name in plugin_names:
out = getattr(self, name)(x)
return out
@property
def norm1(self):
"""nn.Module: normalization layer after the first convolution layer"""
return getattr(self, self.norm1_name)
@property
def norm2(self):
"""nn.Module: normalization layer after the second convolution layer"""
return getattr(self, self.norm2_name)
@property
def norm3(self):
"""nn.Module: normalization layer after the third convolution layer"""
return getattr(self, self.norm3_name)
def forward(self, x):
"""Forward function."""
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)
out = self.relu(out)
return out
@BACKBONES.register_module()
class ResNet(BaseModule):
"""ResNet backbone.
This backbone is the improved implementation of `Deep Residual Learning
for Image Recognition `_.
Args:
depth (int): Depth of resnet, from {18, 34, 50, 101, 152}.
in_channels (int): Number of input image channels. Default: 3.
stem_channels (int): Number of stem channels. Default: 64.
base_channels (int): Number of base channels of res layer. Default: 64.
num_stages (int): Resnet stages, normally 4. 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.
Default: (0, 1, 2, 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. Default: 'pytorch'.
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): Dictionary to construct and config conv layer.
When conv_cfg is None, cfg will be set to dict(type='Conv2d').
Default: None.
norm_cfg (dict): Dictionary to construct and config norm layer.
Default: dict(type='BN', requires_grad=True).
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.
dcn (dict | None): Dictionary to construct and config DCN conv layer.
When dcn is not None, conv_cfg must be None. Default: None.
stage_with_dcn (Sequence[bool]): Whether to set DCN conv for each
stage. The length of stage_with_dcn is equal to num_stages.
Default: (False, False, False, False).
plugins (list[dict]): List of plugins for stages, each dict contains:
- cfg (dict, required): Cfg dict to build plugin.
- position (str, required): Position inside block to insert plugin,
options: 'after_conv1', 'after_conv2', 'after_conv3'.
- stages (tuple[bool], optional): Stages to apply plugin, length
should be same as 'num_stages'.
Default: None.
multi_grid (Sequence[int]|None): Multi grid dilation rates of last
stage. Default: None.
contract_dilation (bool): Whether contract first dilation of each layer
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.
pretrained (str, optional): model pretrained path. Default: None.
init_cfg (dict or list[dict], optional): Initialization config dict.
Default: None.
Example:
>>> from mmseg.models import ResNet
>>> import torch
>>> self = ResNet(depth=18)
>>> self.eval()
>>> inputs = torch.rand(1, 3, 32, 32)
>>> level_outputs = self.forward(inputs)
>>> for level_out in level_outputs:
... print(tuple(level_out.shape))
(1, 64, 8, 8)
(1, 128, 4, 4)
(1, 256, 2, 2)
(1, 512, 1, 1)
"""
arch_settings = {
18: (BasicBlock, (2, 2, 2, 2)),
34: (BasicBlock, (3, 4, 6, 3)),
50: (Bottleneck, (3, 4, 6, 3)),
101: (Bottleneck, (3, 4, 23, 3)),
152: (Bottleneck, (3, 8, 36, 3))
}
def __init__(self,
depth,
in_channels=3,
stem_channels=64,
base_channels=64,
num_stages=4,
strides=(1, 2, 2, 2),
dilations=(1, 1, 1, 1),
out_indices=(0, 1, 2, 3),
style='pytorch',
deep_stem=False,
avg_down=False,
frozen_stages=-1,
conv_cfg=None,
norm_cfg=dict(type='BN', requires_grad=True),
norm_eval=False,
dcn=None,
stage_with_dcn=(False, False, False, False),
plugins=None,
multi_grid=None,
contract_dilation=False,
with_cp=False,
zero_init_residual=True,
pretrained=None,
init_cfg=None):
super(ResNet, self).__init__(init_cfg)
if depth not in self.arch_settings:
raise KeyError(f'invalid depth {depth} for resnet')
self.pretrained = pretrained
self.zero_init_residual = zero_init_residual
block_init_cfg = None
assert not (init_cfg and pretrained), \
'init_cfg and pretrained cannot be setting at the same time'
if isinstance(pretrained, str):
warnings.warn('DeprecationWarning: pretrained is a deprecated, '
'please use "init_cfg" instead')
self.init_cfg = dict(type='Pretrained', checkpoint=pretrained)
elif pretrained is None:
if init_cfg is None:
self.init_cfg = [
dict(type='Kaiming', layer='Conv2d'),
dict(
type='Constant',
val=1,
layer=['_BatchNorm', 'GroupNorm'])
]
block = self.arch_settings[depth][0]
if self.zero_init_residual:
if block is BasicBlock:
block_init_cfg = dict(
type='Constant',
val=0,
override=dict(name='norm2'))
elif block is Bottleneck:
block_init_cfg = dict(
type='Constant',
val=0,
override=dict(name='norm3'))
else:
raise TypeError('pretrained must be a str or None')
self.depth = depth
self.stem_channels = stem_channels
self.base_channels = base_channels
self.num_stages = num_stages
assert num_stages >= 1 and num_stages <= 4
self.strides = strides
self.dilations = dilations
assert len(strides) == len(dilations) == num_stages
self.out_indices = out_indices
assert max(out_indices) < num_stages
self.style = style
self.deep_stem = deep_stem
self.avg_down = avg_down
self.frozen_stages = frozen_stages
self.conv_cfg = conv_cfg
self.norm_cfg = norm_cfg
self.with_cp = with_cp
self.norm_eval = norm_eval
self.dcn = dcn
self.stage_with_dcn = stage_with_dcn
if dcn is not None:
assert len(stage_with_dcn) == num_stages
self.plugins = plugins
self.multi_grid = multi_grid
self.contract_dilation = contract_dilation
self.block, stage_blocks = self.arch_settings[depth]
self.stage_blocks = stage_blocks[:num_stages]
self.inplanes = stem_channels
self._make_stem_layer(in_channels, stem_channels)
self.res_layers = []
for i, num_blocks in enumerate(self.stage_blocks):
stride = strides[i]
dilation = dilations[i]
dcn = self.dcn if self.stage_with_dcn[i] else None
if plugins is not None:
stage_plugins = self.make_stage_plugins(plugins, i)
else:
stage_plugins = None
stage_multi_grid = multi_grid if i == len(
self.stage_blocks) - 1 else None
planes = 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=with_cp,
conv_cfg=conv_cfg,
norm_cfg=norm_cfg,
dcn=dcn,
plugins=stage_plugins,
multi_grid=stage_multi_grid,
contract_dilation=contract_dilation,
init_cfg=block_init_cfg)
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()
self.feat_dim = self.block.expansion * base_channels * 2**(
len(self.stage_blocks) - 1)
def make_stage_plugins(self, plugins, stage_idx):
"""make plugins for ResNet 'stage_idx'th stage .
Currently we support to insert 'context_block',
'empirical_attention_block', 'nonlocal_block' into the backbone like
ResNet/ResNeXt. They could be inserted after conv1/conv2/conv3 of
Bottleneck.
An example of plugins format could be :
>>> plugins=[
... dict(cfg=dict(type='xxx', arg1='xxx'),
... stages=(False, True, True, True),
... position='after_conv2'),
... dict(cfg=dict(type='yyy'),
... stages=(True, True, True, True),
... position='after_conv3'),
... dict(cfg=dict(type='zzz', postfix='1'),
... stages=(True, True, True, True),
... position='after_conv3'),
... dict(cfg=dict(type='zzz', postfix='2'),
... stages=(True, True, True, True),
... position='after_conv3')
... ]
>>> self = ResNet(depth=18)
>>> stage_plugins = self.make_stage_plugins(plugins, 0)
>>> assert len(stage_plugins) == 3
Suppose 'stage_idx=0', the structure of blocks in the stage would be:
conv1-> conv2->conv3->yyy->zzz1->zzz2
Suppose 'stage_idx=1', the structure of blocks in the stage would be:
conv1-> conv2->xxx->conv3->yyy->zzz1->zzz2
If stages is missing, the plugin would be applied to all stages.
Args:
plugins (list[dict]): List of plugins cfg to build. The postfix is
required if multiple same type plugins are inserted.
stage_idx (int): Index of stage to build
Returns:
list[dict]: Plugins for current stage
"""
stage_plugins = []
for plugin in plugins:
plugin = plugin.copy()
stages = plugin.pop('stages', None)
assert stages is None or len(stages) == self.num_stages
if stages is None or stages[stage_idx]:
stage_plugins.append(plugin)
return stage_plugins
def make_res_layer(self, **kwargs):
"""Pack all blocks in a stage into a ``ResLayer``."""
return ResLayer(**kwargs)
@property
def norm1(self):
"""nn.Module: the normalization layer named "norm1" """
return getattr(self, self.norm1_name)
def _make_stem_layer(self, in_channels, stem_channels):
"""Make stem layer for ResNet."""
if self.deep_stem:
self.stem = nn.Sequential(
build_conv_layer(
self.conv_cfg,
in_channels,
stem_channels // 2,
kernel_size=3,
stride=2,
padding=1,
bias=False),
build_norm_layer(self.norm_cfg, stem_channels // 2)[1],
nn.ReLU(inplace=True),
build_conv_layer(
self.conv_cfg,
stem_channels // 2,
stem_channels // 2,
kernel_size=3,
stride=1,
padding=1,
bias=False),
build_norm_layer(self.norm_cfg, stem_channels // 2)[1],
nn.ReLU(inplace=True),
build_conv_layer(
self.conv_cfg,
stem_channels // 2,
stem_channels,
kernel_size=3,
stride=1,
padding=1,
bias=False),
build_norm_layer(self.norm_cfg, stem_channels)[1],
nn.ReLU(inplace=True))
else:
self.conv1 = build_conv_layer(
self.conv_cfg,
in_channels,
stem_channels,
kernel_size=7,
stride=2,
padding=3,
bias=False)
self.norm1_name, norm1 = build_norm_layer(
self.norm_cfg, stem_channels, postfix=1)
self.add_module(self.norm1_name, norm1)
self.relu = nn.ReLU(inplace=True)
self.maxpool = nn.MaxPool2d(kernel_size=3, stride=2, padding=1)
def _freeze_stages(self):
"""Freeze stages param and norm stats."""
if self.frozen_stages >= 0:
if self.deep_stem:
self.stem.eval()
for param in self.stem.parameters():
param.requires_grad = False
else:
self.norm1.eval()
for m in [self.conv1, self.norm1]:
for param in m.parameters():
param.requires_grad = False
for i in range(1, self.frozen_stages + 1):
m = getattr(self, f'layer{i}')
m.eval()
for param in m.parameters():
param.requires_grad = False
def forward(self, x):
"""Forward function."""
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)
x = res_layer(x)
if i in self.out_indices:
outs.append(x)
return tuple(outs)
def train(self, mode=True):
"""Convert the model into training mode while keep normalization layer
freezed."""
super(ResNet, self).train(mode)
self._freeze_stages()
if mode and self.norm_eval:
for m in self.modules():
if isinstance(m, _BatchNorm):
m.eval()
@BACKBONES.register_module()
class ResNetV1c(ResNet):
"""ResNetV1c variant described in [1]_.
Compared with default ResNet(ResNetV1b), ResNetV1c replaces the 7x7 conv in
the input stem with three 3x3 convs. For more details please refer to `Bag
of Tricks for Image Classification with Convolutional Neural Networks
`_.
"""
def __init__(self, **kwargs):
super(ResNetV1c, self).__init__(
deep_stem=True, avg_down=False, **kwargs)
@BACKBONES.register_module()
class ResNetV1d(ResNet):
"""ResNetV1d variant described in [1]_.
Compared with default ResNet(ResNetV1b), ResNetV1d replaces the 7x7 conv in
the input stem with three 3x3 convs. And in the downsampling block, a 2x2
avg_pool with stride 2 is added before conv, whose stride is changed to 1.
"""
def __init__(self, **kwargs):
super(ResNetV1d, self).__init__(
deep_stem=True, avg_down=True, **kwargs)
