描述这段代码 # load pretrained params from torchvision.models.vgg16(pretrained=True) if pretrained: pretrained_model = torchvision.models.vgg16(pretrained=pretrained) = pretrained_params = pretrained_model.state_dict() keys = list(pretrained_params.keys()) new_dict = {} for index, key in enumerate(self.state_dict().keys()): new_dict[key] = pretrained_params[keys[index]] self.load_state_dict(new_dict) = self.classifier = nn.Sequential( = nn.Linear(in_features=512 * 1 * 1, out_features=256), = # nn.Linear(in_features=512 * 7 * 7, out_features=256), = nn.ReLU(True), nn.Dropout(), nn.Linear(in_features=256, out_features=256), nn.ReLU(True), nn.Dropout(), nn.Linear(in_features=256, out_features=numClasses), ) def forward(self, x): # output: 32 * 32 * 3 x = self.relu1_1(self.conv1_1(x)) # output: 32 * 32 * 64 x = self.relu1_2(self.conv1_2(x)) # output: 32 * 32 * 64 x = self.pool1(x) # output: 16 * 16 * 64 x = self.relu2_1(self.conv2_1(x)) x = self.relu2_2(self.conv2_2(x)) x = self.pool2(x) x = self.relu3_1(self.conv3_1(x)) x = self.relu3_2(self.conv3_2(x)) x = self.relu3_3(self.conv3_3(x)) x = self.pool3(x) x = self.relu4_1(self.conv4_1(x)) x = self.relu4_2(self.conv4_2(x)) x = self.relu4_3(self.conv4_3(x)) x = self.pool4(x) x = self.relu5_1(self.conv5_1(x)) x = self.relu5_2(self.conv5_2(x)) x = self.relu5_3(self.conv5_3(x)) x = self.pool5(x) x = x.view(x.size(0), -1) output = self.classifier(x) return output

这段代码定义了一个基于 VGG16 架构的卷积神经网络模型，用于图像分类任务。在初始化过程中，如果指定了 pretrained=True 参数，则会从 torchvision.models.vgg16 加载预先训练好的参数，并将其应用于模型的权重中。接着，定义了一个包含多个线性层和激活函数的分类器，用于对卷积层的输出进行分类。在前向传递时，输入图像 x 经过多个卷积和池化层后，展平成一个向量输入到分类器中，最终产生分类结果。