Novel Computing Paradigms using Oscillators

Tianshi Wang

EECS Department
University of California, Berkeley
Technical Report No. UCB/EECS-2020-12
January 10, 2020

http://www2.eecs.berkeley.edu/Pubs/TechRpts/2020/EECS-2020-12.pdf

This dissertation is concerned with new ways of using oscillators to perform computational tasks. Specifically, it introduces methods for building finite state machines (for general-purpose Boolean computation) as well as Ising machines (for solving combinatorial optimization problems) using coupled oscillator networks.

But firstly, why oscillators? Why use them for computation?

An important reason is simply that oscillators are fascinating. Coupled oscillator systems often display intriguing synchronization phenomena where spontaneous patterns arise. From the synchronous flashing of fireflies to Huygens' clocks ticking in unison, from the molecular mechanism of circadian rhythms to the phase patterns in oscillatory neural circuits, the observation and study of synchronization in coupled oscillators has a long and rich history. Engineers across many disciplines have also taken inspiration from these phenomena, e.g., to design high-performance communication circuits and optical lasers. To be able to contribute to the study of coupled oscillators and leverage them in novel paradigms of computing is without question an interesting and fulfilling quest in and of itself.

Moreover, as Moore's Law nears its limits, new computing paradigms that are different from mere CMOS scaling have become an important area of exploration. While most efforts focus on novel materials/devices and architectures, our work represents a different direction with several points of novelty and attractiveness. Firstly, it makes meaningful use of nonlinear dynamical phenomena to tackle well-defined computational tasks that span analog and digital domains. It also differs from conventional computational systems at the fundamental logic encoding level, using timing/phase of oscillation as opposed to voltage levels as logic values. These differences bring about several advantages. The change of logic encoding has several device- and system-level benefits related to noise immunity and interference resistance. The use of nonlinear oscillator dynamics allows our systems to address problems difficult for conventional digital computation. Furthermore, our schemes are amenable to realizations using almost all types of oscillators, allowing a wide variety of devices from multiple physical domains to serve as the substrate for computing. This ability to leverage emerging multiphysics devices need not put off the realization of our ideas far into the future. Instead, implementations using well-established circuit technology are already both practical and attractive.

This work also differs from all past work on oscillator-based computing, which mostly focuses on specialized image preprocessing tasks. Perhaps its most unique feature is that our systems use transitions between analog and digital modes of operation --- instead of simply coupling oscillators and letting their phases settle to a continuum of values, we use a special type of injection locking to make them settle with one of the several well-defined stable phases for encoding logic. Our schemes of Boolean and Ising computation, built upon this phase digitization, expand the scope of oscillator-based computing significantly.

Our ideas are built on years of past research in the modelling, simulation and analysis of oscillators. While there is a considerable amount of literature for the subject, we have been able to further develop the underlying theory, connecting the dots to find a path of analysis that starts from the low-level differential oscillator equations and arrives at phase-based models and energy landscapes of coupled oscillator systems. This theoretical scaffolding is able not only to explain the operation of oscillator-based systems, but also to serve as the basis for simulation and design tools. Building on this, we explore the practical design of our proposed systems, demonstrate working prototypes, as well as develop the techniques, tools and methodologies essential for the process.

Advisor: Jaijeet Roychowdhury


BibTeX citation:

@phdthesis{Wang:EECS-2020-12,
    Author = {Wang, Tianshi},
    Title = {Novel Computing Paradigms using Oscillators},
    School = {EECS Department, University of California, Berkeley},
    Year = {2020},
    Month = {Jan},
    URL = {http://www2.eecs.berkeley.edu/Pubs/TechRpts/2020/EECS-2020-12.html},
    Number = {UCB/EECS-2020-12},
    Abstract = {This dissertation is concerned with new ways of using oscillators to perform computational tasks. Specifically, it introduces methods for building finite state machines (for general-purpose Boolean computation) as well as Ising machines (for solving combinatorial optimization problems) using coupled oscillator networks.

But firstly, why oscillators? Why use them for computation?

An important reason is simply that oscillators are fascinating. Coupled oscillator systems often display intriguing synchronization phenomena where spontaneous patterns arise. From the synchronous flashing of fireflies to Huygens' clocks ticking in unison, from the molecular mechanism of circadian rhythms to the phase patterns in oscillatory neural circuits, the observation and study of synchronization in coupled oscillators has a long and rich history. Engineers across many disciplines have also taken inspiration from these phenomena, e.g., to design high-performance communication circuits and optical lasers. To be able to contribute to the study of coupled oscillators and leverage them in novel paradigms of computing is without question an interesting and fulfilling quest in and of itself.

Moreover, as Moore's Law nears its limits, new computing paradigms that are different from mere CMOS scaling have become an important area of exploration. While most efforts focus on novel materials/devices and architectures, our work represents a different direction with several points of novelty and attractiveness. Firstly, it makes meaningful use of nonlinear dynamical phenomena to tackle well-defined computational tasks that span analog and digital domains. It also differs from conventional computational systems at the fundamental logic encoding level, using timing/phase of oscillation as opposed to voltage levels as logic values. These differences bring about several advantages. The change of logic encoding has several device- and system-level benefits related to noise immunity and interference resistance. The use of nonlinear oscillator dynamics allows our systems to address problems difficult for conventional digital computation. Furthermore, our schemes are amenable to realizations using almost all types of oscillators, allowing a wide variety of devices from multiple physical domains to serve as the substrate for computing. This ability to leverage emerging multiphysics devices need not put off the realization of our ideas far into the future. Instead, implementations using well-established circuit technology are already both practical and attractive.

This work also differs from all past work on oscillator-based computing, which mostly focuses on specialized image preprocessing tasks. Perhaps its most unique feature is that our systems use transitions between analog and digital modes of operation --- instead of simply coupling oscillators and letting their phases settle to a continuum of values, we use a special type of injection locking to make them settle with one of the several well-defined stable phases for encoding logic. Our schemes of Boolean and Ising computation, built upon this phase digitization, expand the scope of oscillator-based computing significantly.

Our ideas are built on years of past research in the modelling, simulation and analysis of oscillators. While there is a considerable amount of literature for the subject, we have been able to further develop the underlying theory, connecting the dots to find a path of analysis that starts from the low-level differential oscillator equations and arrives at phase-based models and energy landscapes of coupled oscillator systems. This theoretical scaffolding is able not only to explain the operation of oscillator-based systems, but also to serve as the basis for simulation and design tools. Building on this, we explore the practical design of our proposed systems, demonstrate working prototypes, as well as develop the techniques, tools and methodologies essential for the process.}
}

EndNote citation:

%0 Thesis
%A Wang, Tianshi
%T Novel Computing Paradigms using Oscillators
%I EECS Department, University of California, Berkeley
%D 2020
%8 January 10
%@ UCB/EECS-2020-12
%U http://www2.eecs.berkeley.edu/Pubs/TechRpts/2020/EECS-2020-12.html
%F Wang:EECS-2020-12