Physics-inspired Ising Computing with Ring Oscillator Activated p-bits

TL;DR

This paper presents an asynchronous p-computer with approximately 800 p-bits, emulating sMTJ dynamics in FPGAs, demonstrating promising performance for Ising problem solving comparable to synchronous designs.

Contribution

It introduces a truly asynchronous medium-scale p-computer architecture that closely mimics sMTJ behavior and evaluates its performance on Ising problems, showing competitive scalability.

Findings

Asynchronous architecture achieves parallelism comparable to synchronous designs.

The system effectively emulates sMTJ dynamics in FPGA hardware.

Results suggest scalability to millions of p-bits for complex problem solving.

Abstract

The nearing end of Moore's Law has been driving the development of domain-specific hardware tailored to solve a special set of problems. Along these lines, probabilistic computing with inherently stochastic building blocks (p-bits) have shown significant promise, particularly in the context of hard optimization and statistical sampling problems. p-bits have been proposed and demonstrated in different hardware substrates ranging from small-scale stochastic magnetic tunnel junctions (sMTJs) in asynchronous architectures to large-scale CMOS in synchronous architectures. Here, we design and implement a truly asynchronous and medium-scale p-computer (with $\approx$ 800 p-bits) that closely emulates the asynchronous dynamics of sMTJs in Field Programmable Gate Arrays (FPGAs). Using hard instances of the planted Ising glass problem on the Chimera lattice, we evaluate the performance of the asynchronous architecture against an ideal, synchronous design that performs parallelized (chromatic) exact Gibbs sampling. We find that despite the lack of any careful synchronization, the asynchronous design achieves parallelism with comparable algorithmic scaling in the ideal, carefully tuned and parallelized synchronous design. Our results highlight the promise of massively scaled p-computers with millions of free-running p-bits made out of nanoscale building blocks such as stochastic magnetic tunnel junctions.