Reliability Analysis of Memristive Reservoir Computing Architecture

Neuromorphic computing systems have emerged as powerful computation tools in the field of object recognition and control systems. However, training these systems, which are usually characterized by recurrent connectivity, requires abundant computational resources: memory, computation, data, and time. Reservoir computing (RC) framework reduces this high computational training cost by focusing the training effort on only a small subset of connections thus allowing these systems to be amenable to hardware implementation. Using memristors to construct these reservoir computers reduce the area/power consumption even further. However, the inherent variability of memristors poses specific challenges. Here, we conduct an in-depth reliability analysis of challenges posed by HfO2 memristors, including cycle-to-cycle variability, read/write noise, and conductance drift in the context of RC hardware. We also explore plasticity mechanisms such as Spike-Timing Dependent Plasticity (STDP) within the scope of the spiking recurrent neural networks (SRNN) reservoir and their impact on memristor conductance drift (MCD). We present a chaotic time series prediction task applied to a Python model of the constrained hardware design achieving very low Normalized Root Mean Square Error (NRMSE) of 2 × 10-3. The analog neuron and memristive synapse circuits employed for constructing the SRNN are simulated in Cadence Spectre and the energy consumption for the Mackey-Glass (MG) time-series prediction task was found to be approximately 90 nJ.