| """ | |
| ResNet in PyTorch. | |
| For Pre-activation ResNet, see 'preact_resnet.py'. | |
| Reference: | |
| [1] Kaiming He, Xiangyu Zhang, Shaoqing Ren, Jian Sun | |
| Deep Residual Learning for Image Recognition. arXiv:1512.03385 | |
| """ | |
| import torch.nn as nn | |
| import torch.nn.functional as F | |
| class BasicBlock(nn.Module): | |
| expansion = 1 | |
| def __init__(self, in_planes, planes, stride=1): | |
| super(BasicBlock, self).__init__() | |
| self.conv1 = nn.Conv2d(in_planes, planes, kernel_size=3, stride=stride, padding=1, bias=False) | |
| self.bn1 = nn.BatchNorm2d(planes) | |
| self.conv2 = nn.Conv2d(planes, planes, kernel_size=3, stride=1, padding=1, bias=False) | |
| self.bn2 = nn.BatchNorm2d(planes) | |
| self.shortcut = nn.Sequential() | |
| if stride != 1 or in_planes != self.expansion*planes: | |
| self.shortcut = nn.Sequential( | |
| nn.Conv2d(in_planes, self.expansion*planes, kernel_size=1, stride=stride, bias=False), | |
| nn.BatchNorm2d(self.expansion*planes) | |
| ) | |
| def forward(self, x): | |
| out = F.relu(self.bn1(self.conv1(x))) | |
| out = self.bn2(self.conv2(out)) | |
| out += self.shortcut(x) | |
| out = F.relu(out) | |
| return out | |
| class ResNet(nn.Module): | |
| def __init__(self, block, num_blocks, num_classes=10): | |
| super(ResNet, self).__init__() | |
| self.in_planes = 64 | |
| self.conv1 = nn.Conv2d(3, 64, kernel_size=3, stride=1, padding=1, bias=False) | |
| self.bn1 = nn.BatchNorm2d(64) | |
| self.layer1 = self._make_layer(block, 64, num_blocks[0], stride=1) | |
| self.layer2 = self._make_layer(block, 128, num_blocks[1], stride=2) | |
| self.layer3 = self._make_layer(block, 256, num_blocks[2], stride=2) | |
| self.layer4 = self._make_layer(block, 512, num_blocks[3], stride=2) | |
| self.linear = nn.Linear(512*block.expansion, num_classes) | |
| def _make_layer(self, block, planes, num_blocks, stride): | |
| strides = [stride] + [1]*(num_blocks-1) | |
| layers = [] | |
| for stride in strides: | |
| layers.append(block(self.in_planes, planes, stride)) | |
| self.in_planes = planes * block.expansion | |
| return nn.Sequential(*layers) | |
| def forward(self, x): | |
| out = F.relu(self.bn1(self.conv1(x))) | |
| out = self.layer1(out) | |
| out = self.layer2(out) | |
| out = self.layer3(out) | |
| out = self.layer4(out) | |
| out = F.avg_pool2d(out, 4) | |
| out = out.view(out.size(0), -1) | |
| out = self.linear(out) | |
| return out | |
| def ResNet18(): | |
| return ResNet(BasicBlock, [2, 2, 2, 2]) | |
| def ResNet34(): | |
| return ResNet(BasicBlock, [3, 4, 6, 3]) | |