Reliability-Aware Training and Performance Modeling for Processing-In-Memory Systems.

Memristor based Processing-In-Memory (PIM) systems give alternative solutions to boost the computing energy efficiency of Convolutional Neural Network (CNN) based algorithms. However, Analog-to-Digital Converters' (ADCs) high interface costs and the limited size of the memristor crossbars make it challenging to map CNN models onto PIM systems with both high accuracy and high energy efficiency. Besides, it takes a long time to simulate the performance of large-scale PIM systems, resulting in unacceptable development time for the PIM system. To address these problems, we propose a reliability-aware training framework and a behavior-level modeling tool (MNSIM 2.0) for PIM accelerators. The proposed reliability-aware training framework, containing network splitting/merging analysis and a PIM-based non-uniform activation quantization scheme, can improve the energy efficiency by reducing the ADC resolution requirements in memristor crossbars. Moreover, MNSIM 2.0 provides a general modeling method for PIM architecture design and computation data flow; it can evaluate both accuracy and hardware performance within a short time. Experiments based on MNSIM 2.0 show that the reliability-aware training framework can improve 3.4x energy efficiency of PIM accelerators with little accuracy loss. The equivalent energy efficiency is 9.02 TOPS/W, nearly 2.6~4.2x compared with the existing work. We also evaluate more case studies of MNSIM 2.0, which help us balance the trade-off between accuracy and hardware performance.