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mmselfsup.models.necks.swav_neck 源代码
# Copyright (c) OpenMMLab. All rights reserved.
import torch
import torch.nn as nn
from mmcv.cnn import build_norm_layer
from mmcv.runner import BaseModule
from ..builder import NECKS
[文档]@NECKS.register_module()
class SwAVNeck(BaseModule):
"""The non-linear neck of SwAV: fc-bn-relu-fc-normalization.
Args:
in_channels (int): Number of input channels.
hid_channels (int): Number of hidden channels.
out_channels (int): Number of output channels.
with_avg_pool (bool): Whether to apply the global average pooling after
backbone. Defaults to True.
with_l2norm (bool): whether to normalize the output after projection.
Defaults to True.
norm_cfg (dict): Dictionary to construct and config norm layer.
Defaults to dict(type='SyncBN').
init_cfg (dict or list[dict], optional): Initialization config dict.
"""
def __init__(self,
in_channels,
hid_channels,
out_channels,
with_avg_pool=True,
with_l2norm=True,
norm_cfg=dict(type='SyncBN'),
init_cfg=[
dict(
type='Constant',
val=1,
layer=['_BatchNorm', 'GroupNorm'])
]):
super(SwAVNeck, self).__init__(init_cfg)
self.with_avg_pool = with_avg_pool
self.with_l2norm = with_l2norm
if with_avg_pool:
self.avgpool = nn.AdaptiveAvgPool2d((1, 1))
if out_channels == 0:
self.projection_neck = None
elif hid_channels == 0:
self.projection_neck = nn.Linear(in_channels, out_channels)
else:
self.bn = build_norm_layer(norm_cfg, hid_channels)[1]
self.projection_neck = nn.Sequential(
nn.Linear(in_channels, hid_channels), self.bn,
nn.ReLU(inplace=True), nn.Linear(hid_channels, out_channels))
def forward_projection(self, x):
if self.projection_neck is not None:
x = self.projection_neck(x)
if self.with_l2norm:
x = nn.functional.normalize(x, dim=1, p=2)
return x
[文档] def forward(self, x):
# forward computing
# x: list of feature maps, len(x) according to len(num_crops)
avg_out = []
for _x in x:
_x = _x[0]
if self.with_avg_pool:
_out = self.avgpool(_x)
avg_out.append(_out)
feat_vec = torch.cat(avg_out) # [sum(num_crops) * N, C]
feat_vec = feat_vec.view(feat_vec.size(0), -1)
output = self.forward_projection(feat_vec)
return [output]