Long Live TIME: Improving Lifetime for Training-In-Memory Engines by Structured Gradient Sparsification

Deeper and larger Neural Networks (NNs) have made breakthroughs in many fields. While conventional CMOS-based computing platforms are hard to achieve higher energy efficiency. RRAM-based systems provide a promising solution to build efficient Training-In-Memory Engines (TIME). While the endurance of RRAM cells is limited, it's a severe issue as the weights of NN always need to be updated for thousands to millions of times during training. Gradient sparsification can address this problem by dropping off most of the smaller gradients but introduce unacceptable computation cost. We proposed an effective framework, SGS-ARS, including Structured Gradient Sparsification (SGS) and Aging-aware Row Swapping (ARS) scheme, to guarantee write balance across whole RRAM crossbars and prolong the lifetime of TIME. Our experiments demonstrate that 356× lifetime extension is achieved when TIME is programmed to train ResNet-50 on Imagenet dataset with our SGS-ARS framework.