DROID: Discrete-Time Simulation for Ring-Oscillator-Based Ising Design

TL;DR

DROID is an efficient event-driven simulation method for CMOS Ising machines that accurately predicts system evolution and solutions, significantly outperforming traditional simulation tools like HSPICE.

Contribution

It introduces DROID, a novel simulation approach that models CMOS Ising machines with high accuracy and efficiency, including effects of transistor nonlinearities.

Findings

DROID is nearly 10,000 times faster than HSPICE.

DROID achieves similar solution distributions as hardware.

The method is accurate under general delay-phase relations.

Abstract

Many combinatorial problems can be mapped to Ising machines, i.e., networks of coupled oscillators that settle to a minimum-energy ground state, from which the problem solution is inferred. This work proposes DROID, a novel event-driven method for simulating the evolution of a CMOS Ising machine to its ground state. The approach is accurate under general delay-phase relations that include the effects of the transistor nonlinearities and is computationally efficient. On a realistic-size all-to-all coupled ring oscillator array, DROID is nearly four orders of magnitude faster than a traditional HSPICE simulation in predicting the evolution of a coupled oscillator system and is demonstrated to attain a similar distribution of solutions as the hardware.