Let's define a training step by defining the loss_fn globally and implementing a step with the following substeps: all gradients must be reseted by optimizer.zero_grad() get the result of a forward pass of the network calculate the loss for this batch do a backwardpass using .backward() on the calculated loss do an optimizer step 帮我按照上面的要求补充下面的代码 def training_step(net, optimizer, loss_fn, batch): img, gt = batch # implement training step ... return loss
时间: 2024-02-14 13:17:28 浏览: 15
好的,请参考下面的完整代码:
```python
def training_step(net, optimizer, loss_fn, batch):
img, gt = batch
# reset gradients
optimizer.zero_grad()
# forward pass
out = net(img)
# calculate loss
loss = loss_fn(out, gt)
# backward pass
loss.backward()
# optimizer step
optimizer.step()
return loss
```
这段代码中,我们定义了一个名为`training_step`的函数,它接受四个参数:`net`表示网络模型,`optimizer`表示优化器,`loss_fn`表示损失函数,`batch`表示输入数据。
在函数体中,我们首先通过`optimizer.zero_grad()`来将所有的梯度清零。然后我们使用输入数据`img`调用网络模型`net`的前向传播方法,得到输出结果`out`。接下来,我们使用损失函数`loss_fn`计算模型输出结果和实际结果`gt`之间的损失。然后我们调用`loss.backward()`来计算所有参数的梯度。最后,我们使用`optimizer.step()`来更新所有参数。最后,我们将损失值`loss`作为函数的返回值。
相关问题
Define a function first_last(list1) that returns a list with the first and last element of list1 interchanged.
Here's the Python code for the function `first_last(list1)` that returns a list with the first and last element of `list1` interchanged:
```python
def first_last(list1):
if len(list1) < 2:
return list1
else:
first = list1[0]
last = list1[-1]
list1[0] = last
list1[-1] = first
return list1
```
This function takes in a list `list1` as its input and first checks if the length of the list is less than 2. If the length is less than 2, it simply returns the original list. Otherwise, it stores the first element of the list in a variable called `first` and the last element of the list in a variable called `last`. It then interchanges the values of `first` and `last` in the list and returns the modified list.
Which is used to define the member of a class externally? a. : b. :: c. # d. !!$
b. ::
The scope resolution operator `::` is used to define a member of a class externally in C++. This allows the definition of a member function or a static data member to be separate from its declaration in the class definition.
For example:
```
class MyClass {
public:
void myFunction(); // declaration
static int myStaticVariable; // declaration
};
// definition of myFunction
void MyClass::myFunction() {
// function body
}
// definition of myStaticVariable
int MyClass::myStaticVariable = 0;
```
In the example above, `myFunction` and `myStaticVariable` are declared in the class definition, but their definitions are provided externally using the scope resolution operator `::`. This allows the implementation of the member functions and static data members to be separated from the class definition, which can make the code easier to manage and understand.