Chapter 1 Introduction -- Chapter 2 A Theoretical Study on Artificial Intelligence Training -- Chapter 3 New Algorithm 1: Binary Direct Feedback Alignment for Fully-Connected layer -- Chapter 4 New Algorithm 2: Extension of Direct Feedback Alignment to Convolutional Recurrent Neural Network -- Chapter 5 DF-LNPU: A Pipelined Direct Feedback Alignment based Deep Neural Network Learning Processor for Fast Online Learning -- Chapter 6 HNPU-V1: An Adaptive DNN Training Processor Utilizing Stochastic Dynamic Fixed-point and Active Bit-precision Searching -- Chapter 7 HNPU-V2: An Energy-efficient DNN Training Processor for Robust Object Detection with Real-World Environmental Adaptation -- Chapter 8 An Overview of Energy-efficient DNN Training Processors -- Chapter 9 Conclusion.