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@@ -2,32 +2,104 @@ import torch
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import torch.nn as nn
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import torch.utils.model_zoo as model_zoo
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-try:
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- from .yolov2_basic import conv1x1, BasicBlock, Bottleneck
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-except:
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- from yolov2_basic import conv1x1, BasicBlock, Bottleneck
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__all__ = ['ResNet', 'resnet18', 'resnet34', 'resnet50', 'resnet101',
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'resnet152']
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-
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model_urls = {
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- 'resnet18': 'https://download.pytorch.org/models/resnet18-5c106cde.pth',
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- 'resnet34': 'https://download.pytorch.org/models/resnet34-333f7ec4.pth',
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- 'resnet50': 'https://download.pytorch.org/models/resnet50-19c8e357.pth',
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+ 'resnet18': 'https://download.pytorch.org/models/resnet18-5c106cde.pth',
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+ 'resnet34': 'https://download.pytorch.org/models/resnet34-333f7ec4.pth',
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+ 'resnet50': 'https://download.pytorch.org/models/resnet50-19c8e357.pth',
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'resnet101': 'https://download.pytorch.org/models/resnet101-5d3b4d8f.pth',
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'resnet152': 'https://download.pytorch.org/models/resnet152-b121ed2d.pth',
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}
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+# --------------------- ResNet modules ---------------------
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+def conv3x3(in_planes, out_planes, stride=1):
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+ """3x3 convolution with padding"""
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+ return nn.Conv2d(in_planes, out_planes, kernel_size=3, stride=stride,
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+ padding=1, bias=False)
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+
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+def conv1x1(in_planes, out_planes, stride=1):
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+ """1x1 convolution"""
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+ return nn.Conv2d(in_planes, out_planes, kernel_size=1, stride=stride, bias=False)
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+
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+class BasicBlock(nn.Module):
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+ expansion = 1
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+
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+ def __init__(self, inplanes, planes, stride=1, downsample=None):
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+ super(BasicBlock, self).__init__()
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+ self.conv1 = conv3x3(inplanes, planes, stride)
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+ self.bn1 = nn.BatchNorm2d(planes)
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+ self.relu = nn.ReLU(inplace=True)
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+ self.conv2 = conv3x3(planes, planes)
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+ self.bn2 = nn.BatchNorm2d(planes)
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+ self.downsample = downsample
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+ self.stride = stride
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+
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+ def forward(self, x):
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+ identity = x
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+
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+ out = self.conv1(x)
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+ out = self.bn1(out)
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+ out = self.relu(out)
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+
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+ out = self.conv2(out)
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+ out = self.bn2(out)
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+
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+ if self.downsample is not None:
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+ identity = self.downsample(x)
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+
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+ out += identity
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+ out = self.relu(out)
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+
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+ return out
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+
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+class Bottleneck(nn.Module):
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+ expansion = 4
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+
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+ def __init__(self, inplanes, planes, stride=1, downsample=None):
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+ super(Bottleneck, self).__init__()
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+ self.conv1 = conv1x1(inplanes, planes)
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+ self.bn1 = nn.BatchNorm2d(planes)
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+ self.conv2 = conv3x3(planes, planes, stride)
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+ self.bn2 = nn.BatchNorm2d(planes)
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+ self.conv3 = conv1x1(planes, planes * self.expansion)
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+ self.bn3 = nn.BatchNorm2d(planes * self.expansion)
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+ self.relu = nn.ReLU(inplace=True)
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+ self.downsample = downsample
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+ self.stride = stride
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+
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+ def forward(self, x):
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+ identity = x
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+
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+ out = self.conv1(x)
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+ out = self.bn1(out)
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+ out = self.relu(out)
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+
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+ out = self.conv2(out)
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+ out = self.bn2(out)
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+ out = self.relu(out)
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+
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+ out = self.conv3(out)
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+ out = self.bn3(out)
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+
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+ if self.downsample is not None:
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+ identity = self.downsample(x)
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+
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+ out += identity
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+ out = self.relu(out)
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+
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+ return out
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+
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+
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# --------------------- ResNet -----------------------
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class ResNet(nn.Module):
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-
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- def __init__(self, block, layers, zero_init_residual=False):
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+ def __init__(self, block, layers):
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super(ResNet, self).__init__()
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self.inplanes = 64
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- self.conv1 = nn.Conv2d(3, 64, kernel_size=7, stride=2, padding=3,
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- bias=False)
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+ self.conv1 = nn.Conv2d(3, 64, kernel_size=7, stride=2, padding=3, bias=False)
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self.bn1 = nn.BatchNorm2d(64)
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self.relu = nn.ReLU(inplace=True)
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self.maxpool = nn.MaxPool2d(kernel_size=3, stride=2, padding=1)
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@@ -43,16 +115,6 @@ class ResNet(nn.Module):
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nn.init.constant_(m.weight, 1)
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nn.init.constant_(m.bias, 0)
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- # Zero-initialize the last BN in each residual branch,
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- # so that the residual branch starts with zeros, and each residual block behaves like an identity.
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- # This improves the model by 0.2~0.3% according to https://arxiv.org/abs/1706.02677
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- if zero_init_residual:
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- for m in self.modules():
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- if isinstance(m, Bottleneck):
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- nn.init.constant_(m.bn3.weight, 0)
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- elif isinstance(m, BasicBlock):
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- nn.init.constant_(m.bn2.weight, 0)
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-
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def _make_layer(self, block, planes, blocks, stride=1):
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downsample = None
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if stride != 1 or self.inplanes != planes * block.expansion:
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