Continuous black-box optimization with an Ising machine and random subspace coding

A black-box optimization algorithm such as Bayesian optimization finds the extremum of an unknown function by alternating the inference of the underlying function and optimization of an acquisition function. In a high-dimensional space, such algorithms perform poorly due to the difficulty of acquisi...

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Main Authors: Syun Izawa, Koki Kitai, Shu Tanaka, Ryo Tamura, Koji Tsuda
Format: Article
Language:English
Published: American Physical Society 2022-04-01
Series:Physical Review Research
Online Access:http://doi.org/10.1103/PhysRevResearch.4.023062
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author Syun Izawa
Koki Kitai
Shu Tanaka
Ryo Tamura
Koji Tsuda
author_facet Syun Izawa
Koki Kitai
Shu Tanaka
Ryo Tamura
Koji Tsuda
author_sort Syun Izawa
collection DOAJ
description A black-box optimization algorithm such as Bayesian optimization finds the extremum of an unknown function by alternating the inference of the underlying function and optimization of an acquisition function. In a high-dimensional space, such algorithms perform poorly due to the difficulty of acquisition function optimization. Herein, we apply Ising machines to overcome the difficulty in the continuous black-box optimization. As an Ising machine specializes in optimization of binary problems, a continuous vector has to be encoded to binary, and the solution by Ising machines has to be translated back. Our method has the following three parts: (1) random subspace coding based on axis-parallel hyperrectangles from continuous vector to binary vector, (2) a quadratic unconstrained binary optimization (QUBO) defined by the acquisition function based on the nonnegative-weighted linear regression model, which is solved by Ising machines, and (3) a penalization scheme to ensure that the solution can be translated back. It is shown with benchmark tests that its performance using the D-Wave Advantage quantum annealer and simulated annealing is competitive with a state-of-the-art method based on the Gaussian process in high-dimensional problems. Our method may open up the possibility of Ising machines and other QUBO solvers, including a quantum approximate optimization algorithm using gated-quantum computers, and may expand its range of application to continuous-valued problems.
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spelling doaj.art-9886eb803d044127bc6de8c3f03a019e2024-04-12T17:20:08ZengAmerican Physical SocietyPhysical Review Research2643-15642022-04-014202306210.1103/PhysRevResearch.4.023062Continuous black-box optimization with an Ising machine and random subspace codingSyun IzawaKoki KitaiShu TanakaRyo TamuraKoji TsudaA black-box optimization algorithm such as Bayesian optimization finds the extremum of an unknown function by alternating the inference of the underlying function and optimization of an acquisition function. In a high-dimensional space, such algorithms perform poorly due to the difficulty of acquisition function optimization. Herein, we apply Ising machines to overcome the difficulty in the continuous black-box optimization. As an Ising machine specializes in optimization of binary problems, a continuous vector has to be encoded to binary, and the solution by Ising machines has to be translated back. Our method has the following three parts: (1) random subspace coding based on axis-parallel hyperrectangles from continuous vector to binary vector, (2) a quadratic unconstrained binary optimization (QUBO) defined by the acquisition function based on the nonnegative-weighted linear regression model, which is solved by Ising machines, and (3) a penalization scheme to ensure that the solution can be translated back. It is shown with benchmark tests that its performance using the D-Wave Advantage quantum annealer and simulated annealing is competitive with a state-of-the-art method based on the Gaussian process in high-dimensional problems. Our method may open up the possibility of Ising machines and other QUBO solvers, including a quantum approximate optimization algorithm using gated-quantum computers, and may expand its range of application to continuous-valued problems.http://doi.org/10.1103/PhysRevResearch.4.023062
spellingShingle Syun Izawa
Koki Kitai
Shu Tanaka
Ryo Tamura
Koji Tsuda
Continuous black-box optimization with an Ising machine and random subspace coding
Physical Review Research
title Continuous black-box optimization with an Ising machine and random subspace coding
title_full Continuous black-box optimization with an Ising machine and random subspace coding
title_fullStr Continuous black-box optimization with an Ising machine and random subspace coding
title_full_unstemmed Continuous black-box optimization with an Ising machine and random subspace coding
title_short Continuous black-box optimization with an Ising machine and random subspace coding
title_sort continuous black box optimization with an ising machine and random subspace coding
url http://doi.org/10.1103/PhysRevResearch.4.023062
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AT kokikitai continuousblackboxoptimizationwithanisingmachineandrandomsubspacecoding
AT shutanaka continuousblackboxoptimizationwithanisingmachineandrandomsubspacecoding
AT ryotamura continuousblackboxoptimizationwithanisingmachineandrandomsubspacecoding
AT kojitsuda continuousblackboxoptimizationwithanisingmachineandrandomsubspacecoding