275 lines
8.1 KiB
Python
275 lines
8.1 KiB
Python
"""
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Credit to https://github.com/XingangPan/IBN-Net.
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"""
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from __future__ import division, absolute_import
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import math
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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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__all__ = ['resnet50_ibn_b']
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model_urls = {
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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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def conv3x3(in_planes, out_planes, stride=1):
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"3x3 convolution with padding"
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return nn.Conv2d(
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in_planes,
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out_planes,
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kernel_size=3,
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stride=stride,
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padding=1,
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bias=False
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)
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class BasicBlock(nn.Module):
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expansion = 1
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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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def forward(self, x):
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residual = x
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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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out = self.conv2(out)
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out = self.bn2(out)
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if self.downsample is not None:
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residual = self.downsample(x)
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out += residual
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out = self.relu(out)
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return out
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class Bottleneck(nn.Module):
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expansion = 4
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def __init__(self, inplanes, planes, stride=1, downsample=None, IN=False):
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super(Bottleneck, self).__init__()
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self.conv1 = nn.Conv2d(inplanes, planes, kernel_size=1, bias=False)
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self.bn1 = nn.BatchNorm2d(planes)
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self.conv2 = nn.Conv2d(
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planes,
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planes,
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kernel_size=3,
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stride=stride,
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padding=1,
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bias=False
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)
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self.bn2 = nn.BatchNorm2d(planes)
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self.conv3 = nn.Conv2d(
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planes, planes * self.expansion, kernel_size=1, bias=False
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)
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self.bn3 = nn.BatchNorm2d(planes * self.expansion)
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self.IN = None
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if IN:
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self.IN = nn.InstanceNorm2d(planes * 4, affine=True)
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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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def forward(self, x):
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residual = x
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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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out = self.conv2(out)
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out = self.bn2(out)
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out = self.relu(out)
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out = self.conv3(out)
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out = self.bn3(out)
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if self.downsample is not None:
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residual = self.downsample(x)
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out += residual
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if self.IN is not None:
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out = self.IN(out)
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out = self.relu(out)
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return out
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class ResNet(nn.Module):
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"""Residual network + IBN layer.
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Reference:
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- He et al. Deep Residual Learning for Image Recognition. CVPR 2016.
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- Pan et al. Two at Once: Enhancing Learning and Generalization
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Capacities via IBN-Net. ECCV 2018.
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"""
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def __init__(
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self,
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block,
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layers,
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num_classes=1000,
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loss='softmax',
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fc_dims=None,
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dropout_p=None,
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**kwargs
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):
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scale = 64
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self.inplanes = scale
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super(ResNet, self).__init__()
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self.loss = loss
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self.feature_dim = scale * 8 * block.expansion
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self.conv1 = nn.Conv2d(
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3, scale, kernel_size=7, stride=2, padding=3, bias=False
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)
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self.bn1 = nn.InstanceNorm2d(scale, affine=True)
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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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self.layer1 = self._make_layer(
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block, scale, layers[0], stride=1, IN=True
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)
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self.layer2 = self._make_layer(
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block, scale * 2, layers[1], stride=2, IN=True
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)
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self.layer3 = self._make_layer(block, scale * 4, layers[2], stride=2)
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self.layer4 = self._make_layer(block, scale * 8, layers[3], stride=2)
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self.avgpool = nn.AdaptiveAvgPool2d((1, 1))
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self.fc = self._construct_fc_layer(
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fc_dims, scale * 8 * block.expansion, dropout_p
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)
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self.classifier = nn.Linear(self.feature_dim, num_classes)
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for m in self.modules():
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if isinstance(m, nn.Conv2d):
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n = m.kernel_size[0] * m.kernel_size[1] * m.out_channels
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m.weight.data.normal_(0, math.sqrt(2. / n))
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elif isinstance(m, nn.BatchNorm2d):
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m.weight.data.fill_(1)
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m.bias.data.zero_()
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elif isinstance(m, nn.InstanceNorm2d):
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m.weight.data.fill_(1)
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m.bias.data.zero_()
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def _make_layer(self, block, planes, blocks, stride=1, IN=False):
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downsample = None
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if stride != 1 or self.inplanes != planes * block.expansion:
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downsample = nn.Sequential(
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nn.Conv2d(
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self.inplanes,
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planes * block.expansion,
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kernel_size=1,
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stride=stride,
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bias=False
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),
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nn.BatchNorm2d(planes * block.expansion),
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)
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layers = []
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layers.append(block(self.inplanes, planes, stride, downsample))
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self.inplanes = planes * block.expansion
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for i in range(1, blocks - 1):
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layers.append(block(self.inplanes, planes))
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layers.append(block(self.inplanes, planes, IN=IN))
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return nn.Sequential(*layers)
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def _construct_fc_layer(self, fc_dims, input_dim, dropout_p=None):
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"""Constructs fully connected layer
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Args:
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fc_dims (list or tuple): dimensions of fc layers, if None, no fc layers are constructed
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input_dim (int): input dimension
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dropout_p (float): dropout probability, if None, dropout is unused
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"""
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if fc_dims is None:
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self.feature_dim = input_dim
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return None
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assert isinstance(
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fc_dims, (list, tuple)
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), 'fc_dims must be either list or tuple, but got {}'.format(
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type(fc_dims)
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)
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layers = []
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for dim in fc_dims:
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layers.append(nn.Linear(input_dim, dim))
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layers.append(nn.BatchNorm1d(dim))
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layers.append(nn.ReLU(inplace=True))
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if dropout_p is not None:
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layers.append(nn.Dropout(p=dropout_p))
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input_dim = dim
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self.feature_dim = fc_dims[-1]
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return nn.Sequential(*layers)
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def featuremaps(self, x):
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x = self.conv1(x)
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x = self.bn1(x)
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x = self.relu(x)
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x = self.maxpool(x)
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x = self.layer1(x)
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x = self.layer2(x)
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x = self.layer3(x)
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x = self.layer4(x)
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return x
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def forward(self, x):
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f = self.featuremaps(x)
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v = self.avgpool(f)
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v = v.view(v.size(0), -1)
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if self.fc is not None:
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v = self.fc(v)
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if not self.training:
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return v
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y = self.classifier(v)
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if self.loss == 'softmax':
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return y
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elif self.loss == 'triplet':
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return y, v
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else:
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raise KeyError("Unsupported loss: {}".format(self.loss))
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def init_pretrained_weights(model, model_url):
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"""Initializes model with pretrained weights.
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Layers that don't match with pretrained layers in name or size are kept unchanged.
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"""
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pretrain_dict = model_zoo.load_url(model_url)
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model_dict = model.state_dict()
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pretrain_dict = {
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k: v
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for k, v in pretrain_dict.items()
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if k in model_dict and model_dict[k].size() == v.size()
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}
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model_dict.update(pretrain_dict)
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model.load_state_dict(model_dict)
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def resnet50_ibn_b(num_classes, loss='softmax', pretrained=False, **kwargs):
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model = ResNet(
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Bottleneck, [3, 4, 6, 3], num_classes=num_classes, loss=loss, **kwargs
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)
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if pretrained:
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init_pretrained_weights(model, model_urls['resnet50'])
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return model
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