python深度学习求导简单题目+pytorch实战

import torch
from torch.autograd import grad

x = torch.tensor([2., ])  # x是输入的图片
w1 = torch.tensor([2., ])  # w是模型的可训练的参数
w2 = torch.tensor([2., ], requires_grad=True)
y = torch.tensor([2., ])  # y是图片的真实标签
y_pred = (3 * x ** 2) * w1 + w2  # y_pred是图片x经过模型得到的输出
loss = (y - y_pred) ** 2  # 做loss，选用平方差损失函数
grads = grad(loss, w2)  # 求loss对w2的导数
print(grads)  # 结果为48