3D-ReG: A 3D ReRAM-based Heterogeneous Architecture for Training Deep Neural Networks. - Bing Li 017; Janardhan Rao Doppa; Partha Pratim Pande; Krishnendu Chakrabarty; Joe X. Qiu; Hai (Helen) Li (ACM J. Emerg. Technol. Comput. Syst., 2020)