1. Extra Curriculum 1. Extra Curriculum PyTorch Optimization Training/Testing Loop Step torch.nn Module PyTorch Documentation Cheat Sheet PyTorch Saving and Loading Model 花费1到2小时阅读或观看gradient descent and backpropagation； Gradient Descent Wikipedia Gradient Descent Algorithm Deep Dive Gradient Descent Neural Network Learn Backpropagation Really Doing Backpropagation Wikipedia