A Memristor-Based Bayesian Machine

TL;DR

This paper presents a novel memristor-based Bayesian machine that enables highly energy-efficient, robust, and explainable reasoning at the edge, demonstrated through experimental fabrication and real-world gesture recognition.

Contribution

It introduces a new architecture for Bayesian reasoning using memristors, combining distributed memory and stochastic computing principles, and demonstrates its effectiveness and energy efficiency.

Findings

Fabricated a small-scale Bayesian machine with 2,048 memristors showing viability.

Achieved 5,000 times less energy consumption for gesture recognition compared to microcontrollers.

Demonstrated robustness, instant operation, and low-voltage compatibility of the system.

Abstract

In recent years, a considerable research effort has shown the energy benefits of implementing neural networks with memristors or other emerging memory technologies. However, for extreme-edge applications with high uncertainty, access to reduced amounts of data, and where explainable decisions are required, neural networks may not provide an acceptable form of intelligence. Bayesian reasoning can solve these concerns, but it is computationally expensive and, unlike neural networks, does not translate naturally to memristor-based architectures. In this work, we introduce, demonstrate experimentally on a fully fabricated hybrid CMOS-memristor system, and analyze a Bayesian machine designed for highly-energy efficient Bayesian reasoning. The architecture of the machine is obtained by writing Bayes' law in a way making its implementation natural by the principles of distributed memory and stochastic computing, allowing the circuit to function using solely local memory and minimal data movement. Measurements on a fabricated small-scale Bayesian machine featuring 2,048 memristors and 30,080 transistors show the viability of this approach and the possibility of overcoming the challenges associated with its design: the inherent imperfections of memristors, as well as the need to distribute very locally higher-than-nominal supply voltages. The design of a scaled-up version of the machine shows its outstanding energy efficiency on a real-life gesture recognition task: a gesture can be recognized using 5,000 times less energy than using a microcontroller unit. The Bayesian machine also features several desirable features, e.g., instant on/off operation, compatibility with low supply voltages, and resilience to single-event upsets. These results open the road for Bayesian reasoning as an attractive way for energy-efficient, robust, and explainable intelligence at the edge.