167 lines
5.4 KiB
Python
167 lines
5.4 KiB
Python
"""resnet in pytorch
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[1] Kaiming He, Xiangyu Zhang, Shaoqing Ren, Jian Sun.
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Deep Residual Learning for Image Recognition
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https://arxiv.org/abs/1512.03385v1
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"""
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import torch
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import torch.nn as nn
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from trainer.networks import register_model
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class BasicBlock(nn.Module):
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"""Basic Block for resnet 18 and resnet 34
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"""
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#BasicBlock and BottleNeck block
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#have different output size
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#we use class attribute expansion
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#to distinct
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expansion = 1
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def __init__(self, in_channels, out_channels, stride=1):
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super().__init__()
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#residual function
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self.residual_function = nn.Sequential(
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nn.Conv2d(in_channels, out_channels, kernel_size=3, stride=stride, padding=1, bias=False),
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nn.BatchNorm2d(out_channels),
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nn.ReLU(inplace=True),
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nn.Conv2d(out_channels, out_channels * BasicBlock.expansion, kernel_size=3, padding=1, bias=False),
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nn.BatchNorm2d(out_channels * BasicBlock.expansion)
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)
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#shortcut
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self.shortcut = nn.Sequential()
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#the shortcut output dimension is not the same with residual function
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#use 1*1 convolution to match the dimension
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if stride != 1 or in_channels != BasicBlock.expansion * out_channels:
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self.shortcut = nn.Sequential(
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nn.Conv2d(in_channels, out_channels * BasicBlock.expansion, kernel_size=1, stride=stride, bias=False),
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nn.BatchNorm2d(out_channels * BasicBlock.expansion)
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)
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def forward(self, x):
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return nn.ReLU(inplace=True)(self.residual_function(x) + self.shortcut(x))
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class BottleNeck(nn.Module):
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"""Residual block for resnet over 50 layers
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"""
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expansion = 4
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def __init__(self, in_channels, out_channels, stride=1):
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super().__init__()
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self.residual_function = nn.Sequential(
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nn.Conv2d(in_channels, out_channels, kernel_size=1, bias=False),
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nn.BatchNorm2d(out_channels),
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nn.ReLU(inplace=True),
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nn.Conv2d(out_channels, out_channels, stride=stride, kernel_size=3, padding=1, bias=False),
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nn.BatchNorm2d(out_channels),
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nn.ReLU(inplace=True),
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nn.Conv2d(out_channels, out_channels * BottleNeck.expansion, kernel_size=1, bias=False),
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nn.BatchNorm2d(out_channels * BottleNeck.expansion),
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)
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self.shortcut = nn.Sequential()
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if stride != 1 or in_channels != out_channels * BottleNeck.expansion:
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self.shortcut = nn.Sequential(
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nn.Conv2d(in_channels, out_channels * BottleNeck.expansion, stride=stride, kernel_size=1, bias=False),
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nn.BatchNorm2d(out_channels * BottleNeck.expansion)
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)
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def forward(self, x):
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return nn.ReLU(inplace=True)(self.residual_function(x) + self.shortcut(x))
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class ResNet(nn.Module):
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def __init__(self, block, num_block, num_classes=100):
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super().__init__()
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self.in_channels = 32
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self.conv1 = nn.Sequential(
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nn.Conv2d(3, 32, kernel_size=3, padding=1, bias=False),
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nn.BatchNorm2d(32),
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nn.ReLU(inplace=True))
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#we use a different inputsize than the original paper
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#so conv2_x's stride is 1
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self.conv2_x = self._make_layer(block, 32, num_block[0], 1)
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self.conv3_x = self._make_layer(block, 64, num_block[1], 2)
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self.conv4_x = self._make_layer(block, 128, num_block[2], 2)
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self.conv5_x = self._make_layer(block, 256, num_block[3], 2)
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self.avgpool = nn.AdaptiveAvgPool2d((1, 1))
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self.fc = nn.Linear(256 * block.expansion, num_classes)
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def _make_layer(self, block, out_channels, num_blocks, stride):
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"""make resnet layers(by layer i didnt mean this 'layer' was the
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same as a neuron netowork layer, ex. conv layer), one layer may
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contain more than one residual block
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Args:
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block: block type, basic block or bottle neck block
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out_channels: output depth channel number of this layer
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num_blocks: how many blocks per layer
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stride: the stride of the first block of this layer
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Return:
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return a resnet layer
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"""
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# we have num_block blocks per layer, the first block
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# could be 1 or 2, other blocks would always be 1
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strides = [stride] + [1] * (num_blocks - 1)
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layers = []
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for stride in strides:
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layers.append(block(self.in_channels, out_channels, stride))
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self.in_channels = out_channels * block.expansion
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return nn.Sequential(*layers)
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def forward(self, x):
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output = self.conv1(x)
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output = self.conv2_x(output)
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output = self.conv3_x(output)
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output = self.conv4_x(output)
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output = self.conv5_x(output)
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output = self.avgpool(output)
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output = output.view(output.size(0), -1)
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output = self.fc(output)
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return output
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@register_model
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def register_cifar_resnet18(opt_net, opt):
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""" return a ResNet 18 object
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"""
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return ResNet(BasicBlock, [2, 2, 2, 2])
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def resnet34():
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""" return a ResNet 34 object
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"""
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return ResNet(BasicBlock, [3, 4, 6, 3])
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def resnet50():
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""" return a ResNet 50 object
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"""
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return ResNet(BottleNeck, [3, 4, 6, 3])
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def resnet101():
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""" return a ResNet 101 object
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"""
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return ResNet(BottleNeck, [3, 4, 23, 3])
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def resnet152():
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""" return a ResNet 152 object
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"""
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return ResNet(BottleNeck, [3, 8, 36, 3])
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