import torch import torch.nn as nn import numpy as np __all__ = ['FixupResNet', 'fixup_resnet18', 'fixup_resnet34', 'fixup_resnet50', 'fixup_resnet101', 'fixup_resnet152'] 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) def conv1x1(in_planes, out_planes, stride=1): """1x1 convolution""" return nn.Conv2d(in_planes, out_planes, kernel_size=1, stride=stride, bias=False) class FixupBasicBlock(nn.Module): expansion = 1 def __init__(self, inplanes, planes, stride=1, downsample=None): super(FixupBasicBlock, self).__init__() # Both self.conv1 and self.downsample layers downsample the input when stride != 1 self.bias1a = nn.Parameter(torch.zeros(1)) self.conv1 = conv3x3(inplanes, planes, stride) self.bias1b = nn.Parameter(torch.zeros(1)) self.lrelu = nn.LeakyReLU(negative_slope=0.1, inplace=True) self.bias2a = nn.Parameter(torch.zeros(1)) self.conv2 = conv3x3(planes, planes) self.scale = nn.Parameter(torch.ones(1)) self.bias2b = nn.Parameter(torch.zeros(1)) self.downsample = downsample self.stride = stride def forward(self, x): identity = x out = self.conv1(x + self.bias1a) out = self.lrelu(out + self.bias1b) out = self.conv2(out + self.bias2a) out = out * self.scale + self.bias2b if self.downsample is not None: identity = self.downsample(x + self.bias1a) out += identity out = self.lrelu(out) return out class FixupBottleneck(nn.Module): expansion = 4 def __init__(self, inplanes, planes, stride=1, downsample=None): super(FixupBottleneck, self).__init__() # Both self.conv2 and self.downsample layers downsample the input when stride != 1 self.bias1a = nn.Parameter(torch.zeros(1)) self.conv1 = conv1x1(inplanes, planes) self.bias1b = nn.Parameter(torch.zeros(1)) self.bias2a = nn.Parameter(torch.zeros(1)) self.conv2 = conv3x3(planes, planes, stride) self.bias2b = nn.Parameter(torch.zeros(1)) self.bias3a = nn.Parameter(torch.zeros(1)) self.conv3 = conv1x1(planes, planes * self.expansion) self.scale = nn.Parameter(torch.ones(1)) self.bias3b = nn.Parameter(torch.zeros(1)) self.lrelu = nn.LeakyReLU(negative_slope=0.1, inplace=True) self.downsample = downsample self.stride = stride def forward(self, x): identity = x out = self.conv1(x + self.bias1a) out = self.lrelu(out + self.bias1b) out = self.conv2(out + self.bias2a) out = self.lrelu(out + self.bias2b) out = self.conv3(out + self.bias3a) out = out * self.scale + self.bias3b if self.downsample is not None: identity = self.downsample(x + self.bias1a) out += identity out = self.lrelu(out) return out class FixupResNet(nn.Module): def __init__(self, block, layers, num_classes=1000): super(FixupResNet, self).__init__() self.num_layers = sum(layers) self.inplanes = 64 self.conv1 = nn.Conv2d(3, 64, kernel_size=7, stride=2, padding=3, bias=False) self.bias1 = nn.Parameter(torch.zeros(1)) self.relu = nn.ReLU(inplace=True) self.maxpool = nn.MaxPool2d(kernel_size=3, stride=2, padding=1) self.layer1 = self._make_layer(block, 64, layers[0]) self.layer2 = self._make_layer(block, 128, layers[1], stride=2) self.layer3 = self._make_layer(block, 256, layers[2], stride=2) self.layer4 = self._make_layer(block, 512, layers[3], stride=2) self.avgpool = nn.AdaptiveAvgPool2d((1, 1)) self.bias2 = nn.Parameter(torch.zeros(1)) self.fc = nn.Linear(512 * block.expansion, num_classes) for m in self.modules(): if isinstance(m, FixupBasicBlock): nn.init.normal_(m.conv1.weight, mean=0, std=np.sqrt(2 / (m.conv1.weight.shape[0] * np.prod(m.conv1.weight.shape[2:]))) * self.num_layers ** (-0.5)) nn.init.constant_(m.conv2.weight, 0) if m.downsample is not None: nn.init.normal_(m.downsample.weight, mean=0, std=np.sqrt(2 / (m.downsample.weight.shape[0] * np.prod(m.downsample.weight.shape[2:])))) elif isinstance(m, FixupBottleneck): nn.init.normal_(m.conv1.weight, mean=0, std=np.sqrt(2 / (m.conv1.weight.shape[0] * np.prod(m.conv1.weight.shape[2:]))) * self.num_layers ** (-0.25)) nn.init.normal_(m.conv2.weight, mean=0, std=np.sqrt(2 / (m.conv2.weight.shape[0] * np.prod(m.conv2.weight.shape[2:]))) * self.num_layers ** (-0.25)) nn.init.constant_(m.conv3.weight, 0) if m.downsample is not None: nn.init.normal_(m.downsample.weight, mean=0, std=np.sqrt(2 / (m.downsample.weight.shape[0] * np.prod(m.downsample.weight.shape[2:])))) elif isinstance(m, nn.Linear): nn.init.constant_(m.weight, 0) nn.init.constant_(m.bias, 0) def _make_layer(self, block, planes, blocks, stride=1): downsample = None if stride != 1 or self.inplanes != planes * block.expansion: downsample = conv1x1(self.inplanes, planes * block.expansion, stride) layers = [] layers.append(block(self.inplanes, planes, stride, downsample)) self.inplanes = planes * block.expansion for _ in range(1, blocks): layers.append(block(self.inplanes, planes)) return nn.Sequential(*layers) def forward(self, x): x = self.conv1(x) x = self.relu(x + self.bias1) x = self.maxpool(x) x = self.layer1(x) x = self.layer2(x) x = self.layer3(x) x = self.layer4(x) x = self.avgpool(x) x = x.view(x.size(0), -1) x = self.fc(x + self.bias2) return x def fixup_resnet18(**kwargs): """Constructs a Fixup-ResNet-18 model.2 """ model = FixupResNet(FixupBasicBlock, [2, 2, 2, 2], **kwargs) return model def fixup_resnet34(**kwargs): """Constructs a Fixup-ResNet-34 model. """ model = FixupResNet(FixupBasicBlock, [3, 4, 6, 3], **kwargs) return model def fixup_resnet50(**kwargs): """Constructs a Fixup-ResNet-50 model. """ model = FixupResNet(FixupBottleneck, [3, 4, 6, 3], **kwargs) return model def fixup_resnet101(**kwargs): """Constructs a Fixup-ResNet-101 model. """ model = FixupResNet(FixupBottleneck, [3, 4, 23, 3], **kwargs) return model def fixup_resnet152(**kwargs): """Constructs a Fixup-ResNet-152 model. """ model = FixupResNet(FixupBottleneck, [3, 8, 36, 3], **kwargs) return model __all__ = ['FixupResNet', 'fixup_resnet18', 'fixup_resnet34', 'fixup_resnet50', 'fixup_resnet101', 'fixup_resnet152']