残差连接 （Residual connection）的示意图如下：
即残差链接就是对网络的输出 $F(X)$ 加上了一个 $X$ 成为了 $F(X)+X$，因为加上了一个 $X$ ，在反向传播的时候，求偏导的时候 会多出来一个1，所以避免了梯度消失。
解决梯度消失 – 残差连接
2019年11月6日
Bonky Zhu
If someone is able to show me that what I think or do is not right, I will happily change, for I seek the truth, by which no one was ever truly harmed. It is the person who continues in his self-deception and ignorance who is harmed.
