1、 introduce

Sometimes we need to change the gradient of a certain layer , Or get a gradient map of a layer , Even painting CAM When visualizing , You need to navigate to a layer in the model , But often the middle-level structure of the model is nested layer by layer , difficult .

2、 Method

We use torchvision.models in resnet34 For example , To get the name "layer1.1.conv2" The layer , Here are resnet34 Screenshot of structural part ：
First, let's look at the names of all the layers ：

for n,v in net.named_parameters():
    print(n)

Output:
	conv1.weight
	bn1.weight
	bn1.bias
	layer1.0.conv1.weight
	layer1.0.bn1.weight
	layer1.0.bn1.bias
	layer1.0.conv2.weight
	layer1.0.bn2.weight
	layer1.0.bn2.bias
	layer1.1.conv1.weight
	layer1.1.bn1.weight
	layer1.1.bn1.bias
	layer1.1.conv2.weight
	layer1.1.bn2.weight
	layer1.1.bn2.bias
	layer1.2.conv1.weight

2.1、 Method 1 ： Get the layer from the structure

There is only one principle to obtain the layer according to the result ： Not sequential Layers of objects , Directly through . name obtain ,sequential The layer of the object passes through [index] obtain sequential A layer in an object
such as "layer1.1.conv2":

• 1ayer1：1ayer1 In a non sequential In the object , So straight through model.layer1 Get this layer
• .1：layer1 It's a sequential object , To get the composition in it, you need to pass [index] obtain , So pass model.layer1[1] Get this layer
• .conv2：conv2 yes model.layer1[1] Medium , and model.layer1[1] No sequential object , So get directly by name , So pass model.layer1[1].conv2 Get
  So if you want to be right layer1.1.conv2 Do something , Directly through lay=model.layer1[1].conv2 You can get the layer , Summary is not pure numbers , Directly by name , It's purely digital , Through the upper layer [index] To get .

2.2、 Mode two ： Get... Directly by name

We already know that the name of the layer we want to operate on is "layer1.1.conv2", Then obtain the layer through the following methods ：

name ="layer1.1.conv2"
for name, module in self.model.named_modules():             
    if name == self.module_name:
        # be module  This is the floor