def forward(self, x): x = self.conv(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) # B x 128 if self.reid: x = x.div(x.norm(p=2,dim=1,keepdim=True)) return x # classifier x = self.classifier(x) return x

这是一个 PyTorch 模型中的 forward 函数，用于前向传播计算。该模型包含了卷积层、ResNet 的若干层、平均池化层和全连接层分类器。

具体来说，该函数的输入是 x，表示输入的数据。在 forward 函数中，x 首先经过卷积层 self.conv，得到一些特征图。然后，特征图通过 ResNet 的若干层 self.layer1、self.layer2、self.layer3、self.layer4，不断提取和提高特征层次，最终得到更加抽象和高层次的特征表示。接着，特征图通过平均池化层 self.avgpool 进行降维，得到一个 B x C x 1 x 1 的张量（B 表示 batch size，C 表示特征通道数）。

如果模型是用于 ReID 任务，接下来的代码将对特征向量进行归一化处理，即将特征向量除以其 L2 范数，以实现更好的特征表达。最后，如果模型是用于分类任务，特征向量将被送入全连接层 self.classifier 进行分类。函数最终返回输出的结果。

相关问题

代码解析： class BasicBlock(nn.Layer): expansion = 1 def init(self, in_channels, channels, stride=1, downsample=None): super().init() self.conv1 = conv1x1(in_channels, channels) self.bn1 = nn.BatchNorm2D(channels) self.relu = nn.ReLU() self.conv2 = conv3x3(channels, channels, stride) self.bn2 = nn.BatchNorm2D(channels) self.downsample = downsample self.stride = stride def forward(self, x): residual = x out = self.conv1(x) out = self.bn1(out) out = self.relu(out) out = self.conv2(out) out = self.bn2(out) if self.downsample is not None: residual = self.downsample(x) out += residual out = self.relu(out) return out class ResNet45(nn.Layer): def init(self, in_channels=3, block=BasicBlock, layers=[3, 4, 6, 6, 3], strides=[2, 1, 2, 1, 1]): self.inplanes = 32 super(ResNet45, self).init() self.conv1 = nn.Conv2D( in_channels, 32, kernel_size=3, stride=1, padding=1, weight_attr=ParamAttr(initializer=KaimingNormal()), bias_attr=False) self.bn1 = nn.BatchNorm2D(32) self.relu = nn.ReLU() self.layer1 = self._make_layer(block, 32, layers[0], stride=strides[0]) self.layer2 = self._make_layer(block, 64, layers[1], stride=strides[1]) self.layer3 = self._make_layer(block, 128, layers[2], stride=strides[2]) self.layer4 = self._make_layer(block, 256, layers[3], stride=strides[3]) self.layer5 = self._make_layer(block, 512, layers[4], stride=strides[4]) self.out_channels = 512 def _make_layer(self, block, planes, blocks, stride=1): downsample = None if stride != 1 or self.inplanes != planes * block.expansion: # downsample = True downsample = nn.Sequential( nn.Conv2D( self.inplanes, planes * block.expansion, kernel_size=1, stride=stride, weight_attr=ParamAttr(initializer=KaimingNormal()), bias_attr=False), nn.BatchNorm2D(planes * block.expansion), ) layers = [] layers.append(block(self.inplanes, planes, stride, downsample)) self.inplanes = planes * block.expansion for i in range(1, blocks): layers.append(block(self.inplanes, planes)) return nn.Sequential(*layers) def forward(self, x): x = self.conv1(x) x = self.bn1(x) x = self.relu(x) x = self.layer1(x) x = self.layer2(x) x = self.layer3(x) x = self.layer4(x) x = self.layer5(x) return x

这是一个 PyTorch 实现的 ResNet 模型，包括 BasicBlock 类和 ResNet45 类。

BasicBlock 类是 ResNet 中的基本模块，由两个卷积层和一个残差连接组成。expansion=1 表示残差连接的扩张率为 1。输入特征图 x 通过 conv1、bn1、relu、conv2、bn2、残差连接和 relu 激活函数后得到输出特征图 out。

ResNet45 类继承自 nn.Layer 类，包含了 ResNet45 模型的结构。该模型包含五个阶段，每个阶段包含若干 BasicBlock 模块。输入特征图先经过一个卷积层、bn1 和 relu 激活函数，然后进入五个阶段，最后输出特征图 x。每个阶段中的 BasicBlock 模块数量由 layers 参数指定，步长由 strides 参数指定。_make_layer 方法用于构建一个阶段，其中 planes 参数表示输出特征图的通道数，stride 参数表示步长。如果步长不为 1 或输入输出特征图通道数不同时，需要进行下采样，即 downsample，downsample 是一个包含 Conv2D 和 BatchNorm2D 的序列。

这个模型的输出特征图通道数为 512，可以用于分类、检测、分割等任务。

class EnhancedResidual(nn.Module): def init(self,in_c,out_c,fm_sz,net_type = 'ta'): super(EnhancedResidual,self).init() self.net_type = net_type self.conv1 = nn.Sequential( nn.Conv2d(in_channels = in_c,out_channels = in_c,kernel_size = 3,padding = 1), nn.BatchNorm2d(in_c), nn.ReLU(), ) self.conv2 = nn.Sequential( nn.Conv2d(in_channels = in_c,out_channels = out_c,kernel_size = 3,padding = 1), nn.BatchNorm2d(out_c), nn.ReLU(), ) self.botneck = nn.Conv2d(in_channels = in_c,out_channels = out_c,kernel_size = 1) self.pool = nn.MaxPool2d(kernel_size = 2,stride = 2) if net_type == 'ta': self.spa = SpatialAttention() self.ca = ChannelAttention(in_planes = in_c,ratio = in_c) self.sa = MultiHeadSelfAttention(in_c = in_c,out_c = in_c // 4,head_n = 4,fm_sz = fm_sz) elif net_type == 'sa': self.sa = MultiHeadSelfAttention(in_c = in_c,out_c = out_c // 4,head_n = 4,fm_sz = fm_sz) elif net_type == 'cbam': self.spa = SpatialAttention() self.ca = ChannelAttention(in_planes = in_c,ratio = in_c) def forward(self,x): x0 = self.botneck(x) x = self.conv1(x) if self.net_type == 'sa': x = self.sa(x) #x = self.conv2(x) elif self.net_type == 'cbam': x = self.ca(x) * x x = self.spa(x) * x x = self.conv2(x) elif self.net_type == 'ta': x = self.ca(x) * x x = self.spa(x) * x x = self.sa(x) x = self.conv2(x) x = x + x0 x = self.pool(x) return x 改写为tensorflow形式

import tensorflow as tf

class EnhancedResidual(tf.keras.layers.Layer):
def __init__(self, in_c, out_c, fm_sz, net_type='ta', **kwargs):
super(EnhancedResidual, self).__init__(**kwargs)
self.net_type = net_type
self.conv1 = tf.keras.Sequential([
tf.keras.layers.Conv2D(filters=in_c, kernel_size=3, padding='same'),
tf.keras.layers.BatchNormalization(),
tf.keras.layers.ReLU()
])
self.conv2 = tf.keras.Sequential([
tf.keras.layers.Conv2D(filters=out_c, kernel_size=3, padding='same'),
tf.keras.layers.BatchNormalization(),
tf.keras.layers.ReLU(),
])
self.botneck = tf.keras.layers.Conv2D(filters=out_c, kernel_size=1)
self.pool = tf.keras.layers.MaxPool2D(pool_size=2, strides=2)
if net_type == 'ta':
self.spa = SpatialAttention()
self.ca = ChannelAttention(in_planes=in_c, ratio=in_c)
self.sa = MultiHeadSelfAttention(in_c=in_c, out_c=in_c // 4, head_n=4, fm_sz=fm_sz)
elif net_type == 'sa':
self.sa = MultiHeadSelfAttention(in_c=in_c, out_c=out_c // 4, head_n=4, fm_sz=fm_sz)
elif net_type == 'cbam':
self.spa = SpatialAttention()
self.ca = ChannelAttention(in_planes=in_c, ratio=in_c)

def call(self, x):
x0 = self.botneck(x)
x = self.conv1(x)
if self.net_type == 'sa':
x = self.sa(x)
# x = self.conv2(x)
elif self.net_type == 'cbam':
x = self.ca(x) * x
x = self.spa(x) * x
x = self.conv2(x)
elif self.net_type == 'ta':
x = self.ca(x) * x
x = self.spa(x) * x
x = self.sa(x)
x = self.conv2(x)
x = x + x0
x = self.pool(x)
return x