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# -*- encoding: utf-8 -*-
import torch
import torch.nn as nn
import torch.nn.functional as F
import torch.utils.model_zoo as modelzoo
# from modules.bn import InPlaceABNSync as BatchNorm2d
resnet18_url = "https://download.pytorch.org/models/resnet18-5c106cde.pth"
def conv3x3(in_planes, out_planes, stride=1):
"""3x3 convolution with padding"""
return nn.Conv2d(in_planes, out_planes, kernel_size=3, stride=stride, padding=1, bias=False)
class BasicBlock(nn.Module):
def __init__(self, in_chan, out_chan, stride=1):
super(BasicBlock, self).__init__()
self.conv1 = conv3x3(in_chan, out_chan, stride)
self.bn1 = nn.BatchNorm2d(out_chan)
self.conv2 = conv3x3(out_chan, out_chan)
self.bn2 = nn.BatchNorm2d(out_chan)
self.relu = nn.ReLU(inplace=True)
self.downsample = None
if in_chan != out_chan or stride != 1:
self.downsample = nn.Sequential(
nn.Conv2d(in_chan, out_chan, kernel_size=1, stride=stride, bias=False),
nn.BatchNorm2d(out_chan),
)
def forward(self, x):
residual = self.conv1(x)
residual = F.relu(self.bn1(residual))
residual = self.conv2(residual)
residual = self.bn2(residual)
shortcut = x
if self.downsample is not None:
shortcut = self.downsample(x)
out = shortcut + residual
out = self.relu(out)
return out
def create_layer_basic(in_chan, out_chan, bnum, stride=1):
layers = [BasicBlock(in_chan, out_chan, stride=stride)]
for i in range(bnum - 1):
layers.append(BasicBlock(out_chan, out_chan, stride=1))
return nn.Sequential(*layers)
class Resnet18(nn.Module):
def __init__(self):
super(Resnet18, self).__init__()
self.conv1 = nn.Conv2d(3, 64, kernel_size=7, stride=2, padding=3, bias=False)
self.bn1 = nn.BatchNorm2d(64)
self.maxpool = nn.MaxPool2d(kernel_size=3, stride=2, padding=1)
self.layer1 = create_layer_basic(64, 64, bnum=2, stride=1)
self.layer2 = create_layer_basic(64, 128, bnum=2, stride=2)
self.layer3 = create_layer_basic(128, 256, bnum=2, stride=2)
self.layer4 = create_layer_basic(256, 512, bnum=2, stride=2)
self.init_weight()
def forward(self, x):
x = self.conv1(x)
x = F.relu(self.bn1(x))
x = self.maxpool(x)
x = self.layer1(x)
feat8 = self.layer2(x) # 1/8
feat16 = self.layer3(feat8) # 1/16
feat32 = self.layer4(feat16) # 1/32
return feat8, feat16, feat32
def init_weight(self):
state_dict = modelzoo.load_url(resnet18_url)
self_state_dict = self.state_dict()
for k, v in state_dict.items():
if "fc" in k:
continue
self_state_dict.update({k: v})
self.load_state_dict(self_state_dict)
def get_params(self):
wd_params, nowd_params = [], []
for name, module in self.named_modules():
if isinstance(module, (nn.Linear, nn.Conv2d)):
wd_params.append(module.weight)
if module.bias is not None:
nowd_params.append(module.bias)
elif isinstance(module, nn.BatchNorm2d):
nowd_params += list(module.parameters())
return wd_params, nowd_params
if __name__ == "__main__":
net = Resnet18()
x = torch.randn(16, 3, 224, 224)
out = net(x)
print(out[0].size())
print(out[1].size())
print(out[2].size())
net.get_params()
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