DTU DeepLearning: exercise 7

torch activation functions: sigmoid, relu, tanh, softplus. https://morvanzhou.github.io/tutorials/machine-learning/torch/2-03-activation/

torch.nn.activation functions: https://pytorch.org/docs/stable/nn.html#non-linear-activations-weighted-sum-nonlinearity

https://zhuanlan.zhihu.com/p/34998569

https://blog.csdn.net/roguesir/article/details/81263442