arXiv subjects

Zeljko Ignjatovic

Publications and source records attributed to Zeljko Ignjatovic.

4 recordsLinked to original sources

arXiv2026

A 64-Spin All-to-All CMOS Ising Machine with Landscape Perturbation Achieving 2.28 nJ/Edge-Bit Energy-to-Solution

A 64-spin all-to-all current-mode coupling Ising machine is implemented in 65 nm CMOS. The design supports 31 coefficient levels in 0.943 mm2 and achieves Energy-to-Solution (ETS) of 2.28 nJ/edge-bit. Continuous programming refresh not only mitigates leakage but also provides a mechanism for deterministic energy landscape perturbation, which consistently improves solution quality with higher success rate compared to operation without landscape perturbation.

cs.AR↗

arXiv2024

A Pseudo-random Number Generator for Multi-Sequence Generation with Programmable Statistics

Pseudo-random number generators (PRNGs) are essential in a wide range of applications, from cryptography to statistical simulations and optimization algorithms. While uniform randomness is crucial for security-critical areas like cryptography, many domains, such as simulated annealing and CMOS-based Ising Machines, benefit from controlled or non-uniform randomness to enhance solution exploration and optimize performance. This paper presents a hardware PRNG that can simultaneously generate multiple uncorrelated sequences with programmable statistics tailored to specific application needs. Designed in 65nm process, the PRNG occupies an area of approximately 0.0013mm^2 and has an energy consumption of 0.57pJ/bit. Simulations confirm the PRNG's effectiveness in modulating the statistical distribution while demonstrating high-quality randomness properties.

cs.CR↗

arXiv2024

SKI-SAT: A CMOS-compatible Hardware for Solving SAT Problems

Nature-inspired computation is receiving increasing attention. Various Ising machine implementations have recently been proven to be effective in solving numerous combinatorial optimization problems including maximum cut, low density parity check (LDPC) decoding, and Boolean satisfiability (SAT) problems. In this paper, a novel method is presented to solve SAT or MAX-SAT problems with a CMOS circuit implementation. The technique solves a SAT problem by mapping the SAT variables onto quantized capacitor voltages generated by an array of nodes that interact through a network of coupling units. The nodal interaction is achieved through coupling currents produced by the coupling units, which charge or discharge capacitor voltages, implementing a gradient descent along the SAT problem's cost function to minimize the number of unsatisfied clauses. The system also incorporates a unique low-complexity perturbation scheme to avoid settling in local minima, greatly enhancing the performance of the system. The simulation results demonstrate that the proposed SKI-SAT is a high-performance and low-energy alternative that surpasses existing solvers by significant margins, achieving more than 10 times faster solution and 300 times less power.

cs.IT↗

arXiv2022

A CMOS-compatible Ising Machine with Bistable Nodes

Physical Ising machines rely on nature to guide a dynamical system towards an optimal state which can be read out as a heuristical solution to a combinatorial optimization problem. Such designs that use nature as a computing mechanism can lead to higher performance and/or lower operation costs and hence have attracted research and prototyping efforts from industry and academia. Quantum annealers are a prominent example of such efforts. However, some physics-centric Ising machines require stringent operating conditions that result in significant bulk and energy budget. Such disadvantages may be acceptable if these designs provide some significant intrinsic advantages at a much larger scale in the future, which remains to be seen. But for now, integrated electronic designs of Ising machines allow more immediate applications. We propose one such design that uses bistable nodes, coupled with programmable and variable strengths. The design is fully CMOS compatible for chip-scale applications and demonstrates competitive solution quality and significantly superior execution time and energy.

quant-ph↗