Redundant Neurons and Shared Redundant Synapses for Robust Memristor-based DNNs with Reduced Overhead

The dominating computational workload in the inference phase of deep neural networks (DNNs) is matrix-vector multiplication. An arising solution to accelerate the inference phase is to perform analog matrix-vector multiplication using memristor crossbar arrays (MCAs). A key challenge is that stuck-at-fault defects may degrade the classification accuracy of the memristor-based DNNs. A common technique to reduce the negative impact of stuck-at-faults is to utilize redundant synapses, i.e, each row in a weight matrix is realized using two (or r) parallel rows in an MCA. In this paper, we propose to handle stuck-at-faults by inserting redundant neurons and by sharing redundant synapses. The first technique is based on inserting redundant neurons to surgically repair neurons connected to rows and columns in the MCAs with many stuck-at-faults. The second technique is focused on sharing redundant synapses between different neurons to reduce the hardware overhead, which generalizes (1:r) synapse redundancy in previous studies to (q:r) synapse redundancy. The experimental results demonstrate new trade-offs between robustness and hardware overhead without requiring the neural networks to be retrained. Compared with state-of-the-art, the power and area overhead for a neural network can be reduced with up to 16% and 25%, respectively.