Updated on 2025/04/28

写真a

 
WAKI HAYATO
 
Organization
Institute of Mathematics for Industry Division of Applied Mathematics Associate Professor
School of Interdisciplinary Science and Innovation Department of Interdisciplinary Science and Innovation（Concurrent）
Graduate School of Mathematics Department of Mathematics（Concurrent）
Joint Graduate School of Mathematics for Innovation （Concurrent）
Title
Associate Professor
Contact information
メールアドレス
Profile
Optimization problem is the problem of finding the maximum or minimum of a given function over a given set, and is widely used in industry and daily life. My research interest are (i) to solve continuous optimization problems, e.g., convex optimization problems and semidefinite programming problems, (ii) to develop effective algorithms and software. In particular, I am strongly interested in research for solving nonlinear and nonconvex optimization problems by using convex optimization and semidefinite programming problems. Also, I research on the development of automotive engine control with industry-academia collaboration as IMI Joint Research.
Homepage
External link

Research Areas

  • Natural Science / Applied mathematics and statistics

  • Informatics / Mathematical informatics

Degree

  • Doctor of science

Education

  • Tokyo Institute of Technology   大学院情報理工学研究科   数理・計算科学専攻

    2004.4 - 2007.3

  • Tokyo Institute of Technology   大学院情報理工学研究科   数理・計算科学専攻

    2002.4 - 2004.3

  • Tokyo Institute of Technology   理学部   情報科学科

    1998.4 - 2002.3

Research Interests・Research Keywords

  • Research theme： Relationship between singularity degree of semidefinite program and the convergence rate of the alternating projection method

    Keyword： semidefinite program, singularity degree, alternating projection method, convergence rate

    Research period： 2020.4 - 2025.3

  • Research theme： We consider optimization modeling. In particular, we are interested in modeling with convex optimization. Convex optimization is broadly used in various academic fields because it has a remarkable property that local solutions are also global. We, however, often encounter ill-posedness in the resulting convex optimization problem. This means that the convex optimization problem has no optimal solutions but, the objective value is finite. Then the computed solutions will be fragile and meaningless in practice. We research how to model well-posed convex optimization from the various phenomena and/or to reveal why we encounter such an ill-posedness.

    Keyword： convex optimization, facial reduction

    Research period： 2017.4 - 2020.3

  • Research theme： Optimization problem is the problem of finding the maximum or minimum of a given function over a given set, and is widely used in industry and daily life. My research interest are (i) to solve continuous optimization problems, e.g., convex optimization problems and semidefinite programming problems, (ii) to develop effective algorithms and software. In particular, I am strongly interested in research for solving nonlinear and nonconvex optimization problems by using convex optimization and semidefinite programming problems. However, such problems have two difficulties: (1) the resulting convex optimization problems become too large-scale to handle, (2) the resulting problems become too degenerate to solve accurately. In addition, we often encounter phenomena that the theoretical results are completely different from computational results due to numerical errors, e.g., round-off errors in computation. Moreover, I am also interested in applications of optimization methods.

    Keyword： Optimization, mathematical programming, continuous optimization, semidefinite programming problem, optimization software

    Research period： 2012.4 - 2019.3

Awards

  • 制御部門マルチシンポジウム賞（基礎分野）

    2023.3   計測自動制御学会 制御部門   2022年開催の制御部門マルチシンポジウムにおいて発表した「L2+誘導ノルムの解析II：下界値解析」という論文が高く評価された.

  • 4th Kimura Best Paper Award of Asian Journal of Control

    2021.10   the Asian Control Association   2020年に国際査読付き雑誌Asian Journal of Controlに掲載された論文(約200論文)の中から選ばれた年間最優秀論文に対して授与される賞

  • 研究賞奨励賞

    2011.9   日本オペレーションズ・リサーチ学会  

    　More details

    日本オペレーションズリサーチ学会から第1回 (2011年度)研究賞奨励賞をいただいた. それまでに行っていた多項式最適化問題に対する半正定値計画緩和の研究が評価された.

Papers

▼display all

Books

Presentations

  • Exact convergence rate of alternating projection method for the intersection of an affine subspace and the second-order cone Invited

    Hayato Waki

    錐線形計画とその周辺  2024.2 

    　More details

    Event date： 2024.2

    Language：Japanese   Presentation type：Oral presentation (general)  

    Venue：成蹊大学, 東京, 日本   Country：Japan  

  • H∞フィードバック制御問題の正定値解について

    脇　隼人

    第６回 制御部門マルチシンポジウム  2019.3 

    　More details

    Event date： 2019.3

    Language：Japanese   Presentation type：Oral presentation (general)  

    Venue：熊本大学 黒髪キャンパス南地区   Country：Japan  

  • Facial reduction for H-infinity state feedback control Invited International conference

    Hayato Waki, Noboru Sebe, Yoshio Ebihara

    International Workshop on "Control and Optimization"  2018.11 

    　More details

    Event date： 2018.11

    Language：English   Presentation type：Oral presentation (general)  

    Venue：京都大学桂キャンパスA1棟208室   Country：Japan  

    Other Link： http://www-lab22.kuee.kyoto-u.ac.jp/~ebihara/WS2018Kyoto2.pdf

  • Ill-posed semidefinite program International conference

    Hayato Waki

    Joint Mini-workshop between KU and NTNU  2018.10 

    　More details

    Event date： 2018.10

    Language：English   Presentation type：Oral presentation (general)  

    Venue：IMI Auditorium (W1-D-413), West Zone 1, Ito campus, Kyushu University   Country：Japan  

    Other Link： https://www.imi.kyushu-u.ac.jp/eng/events/view/1444

  • H-infinity制御に対する面的縮小法

    脇　隼人

    科学研究費 基盤研究(A)「新時代の最適化モデルに基づく意思決定支援プラットフォームの研究と開発」による2018年度ワークショップ  2018.9 

    　More details

    Event date： 2018.9

    Language：Japanese   Presentation type：Oral presentation (general)  

    Venue：東京工業大学 大岡山キャンパス   Country：Japan  

▼display all

MISC

▼display all

Works

Professional Memberships

  • The Operations Research Society of Japan

  • The Japan Society for Industrial and Applied Mathematics

  • Institute for Operations Research and the Management Sciences

  • Mathematical Optimization Society

  • Society for Industrial and Applied Mathematics

Committee Memberships

  • 日本オペレーションズ・リサーチ学会   九州支部副支部長   Foreign country

    2024.3 - 2026.2   

Academic Activities

  • Screening of academic papers

    Role(s)： Peer review

    2022

    　More details

    Type：Peer review 

    Number of peer-reviewed articles in foreign language journals：6

    Number of peer-reviewed articles in Japanese journals：0

    Proceedings of International Conference Number of peer-reviewed papers：0

    Proceedings of domestic conference Number of peer-reviewed papers：0

  • Journal of the Operations Research Society of Japan International contribution

    2021.5 - Present

    　More details

    Type：Academic society, research group, etc. 

  • Screening of academic papers

    Role(s)： Peer review

    2021

    　More details

    Type：Peer review 

    Number of peer-reviewed articles in foreign language journals：3

    Number of peer-reviewed articles in Japanese journals：0

    Proceedings of International Conference Number of peer-reviewed papers：2

    Proceedings of domestic conference Number of peer-reviewed papers：0

  • Screening of academic papers

    Role(s)： Peer review

    2020

    　More details

    Type：Peer review 

    Number of peer-reviewed articles in foreign language journals：4

    Number of peer-reviewed articles in Japanese journals：0

    Proceedings of International Conference Number of peer-reviewed papers：0

    Proceedings of domestic conference Number of peer-reviewed papers：0

  • Screening of academic papers

    Role(s)： Peer review

    2019

    　More details

    Type：Peer review 

    Number of peer-reviewed articles in foreign language journals：6

    Number of peer-reviewed articles in Japanese journals：0

    Proceedings of International Conference Number of peer-reviewed papers：0

    Proceedings of domestic conference Number of peer-reviewed papers：0

▼display all

Research Projects

  • 凸最適化理論における革新を目指して

    Grant number：24K14843  2024.4 - 2029.3

    Grants-in-Aid for Scientific Research  Grant-in-Aid for Scientific Research (C)

    脇 隼人

    　 More details

    Grant type：Scientific research funding

    凸最適化理論は理論的な側面だけでなく、実用面でも非常に重要です。理論の進展は凸最適化の応用に対して有益な影響をもたらすことが期待されます。同様に、凸最適化の応用に取り組む過程で新たな理論的かつ重要な課題が浮かび上がることもあります。そのため、この研究課題では、現在進行中の凸最適化に関する研究を土台に二つのテーマに取り組みます。 特に、理論と実用の両面に焦点を当てます。
    <BR>
    (A) 複数の凸集合の共通部分を求めるアルゴリズムの最悪時の収束率を厳密に評価
    (B) 半正定値計画問題やそれに関連する線形計画問題（共性値錐や完全正値錐上のもの）の応用として、再帰型ニューラルネットワークの安定性解析

    CiNii Research

  • Stability Analysis and Optimal Synthesis of Recurrent Neural Networks by Conic Programming

    Grant number：23K20949  2021.4 - 2026.3

    Grants-in-Aid for Scientific Research  Grant-in-Aid for Scientific Research (B)

    蛯原 義雄, 脇 隼人

    　 More details

    Grant type：Scientific research funding

    時系列解析や自然言語処理の分野で，再帰型ニューラルネットワーク（Recurrent Neural Network, RNN）の有効性が広く認識されている．RNNの最大の特徴はフィードバック機構を有することであり，この機構のおかげでRNNはダイナミカルシステムの振る舞いを模擬できる．しかしながらこのフィードバック機構の存在により，重みや活性化関数の選定によってはRNNの振る舞いが不安定化する．そこで本研究では，制御理論および最適化理論に基づいた，RNNの安定性解析手法の確立を目指す．すなわち，RNNの安定性を判別する問題を凸可解問題に帰着させ，その可解性によって安定判別を行う手法を確立する．

    CiNii Research

  • Optimization modeling via convex optimization

    Grant number：20K11696  2020 - 2022

    Japan Society for the Promotion of Science  Grants-in-Aid for Scientific Research  Grant-in-Aid for Scientific Research (C)

    Waki Hayato

    　 More details

    Authorship：Principal investigator  Grant type：Scientific research funding

    One characterization using singularities defined for the intersection of semi-positive definite cones and affine subspaces is the upper bound on the convergence rate of the alternating projection method. In the present study, we obtained more rigorous evaluation of this upper bound. The convergence rate is evaluated in several settings, and it is found that (i) in some cases the exact convergence rate can be evaluated, and (ii) there are several cases where the convergence rate of the alternating projection method is faster than the upper bound of the convergence rate described by the singularity.

    CiNii Research

  • ERATO 蓮尾メタ数理システムデザインプロジェクト International coauthorship

    2017.10 - 2022.3

    日本 

    　 More details

    Authorship：Coinvestigator(s) 

  • ERATO 蓮尾メタ数理システムデザインプロジェクト

    2017.10 - 2020.3

    Research commissions

    　 More details

    Authorship：Coinvestigator(s)  Grant type：Other funds from industry-academia collaboration

▼display all

Educational Activities

  • I teach calculus for the first-year student, theory of complex function for students in Dept. Eng, numerical computation for students which belong in Dept. of Math. and theory of optimization for students in graduate school.

Award for Educational Activities

  • なし

       

Class subject

  • 共創プロジェクト

    2024.12 - 2025.1   Winter quarter

  • 分類のための数理

    2024.10 - 2024.11   Fall quarter

  • 回帰のための数理

    2024.10 - 2024.11   Fall quarter

  • データの分析・収集

    2024.6 - 2024.7   Summer quarter

  • 最適化理論基礎・演習

    2024.4 - 2024.9   First semester

▼display all

FD Participation

  • 2018.4   Role：Participation   Title：数理学研究院 教員会議

    Organizer：[Undergraduate school/graduate school/graduate faculty]

  • 2016.1   Role：Participation   Title：伊都キャンパスにおける学生生活・学科活動と人間関係

    Organizer：[Undergraduate school/graduate school/graduate faculty]

  • 2014.7   Role：Participation   Title：新GPA制度実施に関するFD

    Organizer：University-wide

  • 2012.5   Role：Participation   Title：数理学研究院 教員会議

    Organizer：[Undergraduate school/graduate school/graduate faculty]

Visiting, concurrent, or part-time lecturers at other universities, institutions, etc.

  • 2021  国立情報学研究所  Classification:Affiliate faculty  Domestic/International Classification:Japan 

  • 2020  国立情報学研究所  Classification:Affiliate faculty  Domestic/International Classification:Japan 

  • 2019  国立情報学研究所  Classification:Affiliate faculty  Domestic/International Classification:Japan 

  • 2018  国立情報学研究所  Classification:Affiliate faculty  Domestic/International Classification:Japan 

Outline of Social Contribution and International Cooperation activities

  • An agreement on academic cooperation between the institute of mathematics for industry and Zuse Institute Berlin was concluded in 2014 spring. We carried out the following three events:
    (1) An international workshop ``Workshop on Optimization in the Real World" was held on Ito campus, Kyushu University, on 14--15 Oct. 2014. This workshop was organized by Professor Katsuki Fujisawa (Institute of mathematics for industry, Kyushu University), Yuji Shinano (Zuse Institute Berlin), and me. We invited Zuse Institute of Berlin of President and Professor Martine Groetschel and some researchers.
    (2) Combinatorial Optimization @ Work was held in Berlin, 27 Sept. -- 9 Oct, 2015. Professor Fujisawa and I give lectures on optimization to students
    (3) We published a post-proceedings on the workshop (1) as a book in the series Mathematics for Industry, Springer.

Social Activities

  • 最適化の数学/九州大学オープンキャンパス(伊都地区)

    九州大学  2018.8

    　More details

    Audience：Infants,　Schoolchildren,　Junior students,　High school students

    Type：Other

  • 糸島市コミュニティバス利用度改善のための調査・研究を通じたバススケジュールの提案とその効果

    九州大学, 糸島市役所  糸島市  2017.3

    　More details

    Audience：General,　Scientific,　Company,　Civic organization,　Governmental agency

    Type：Research consultation

    九大線における朝の通学通勤時間帯における混雑の調査・研究を行い, 前年度の共同研究により2016年度4月から該当する時間帯の九大線を増便した. この効果を調査した所, 2017年3月末までで, 九大線だけで約2万人, 糸島コミュニティバス全体では約2万4千人以上利用者が増加し, 収益も約450万円増加した. また, これに伴い, さらに九大線を増やすバススケジュール(例えば, 土日祝日の周船寺駅からの便を新設)を提案した. 他の地方自治体が運営するコミュニティーバスでは, 利用者, 収益の減少に悩んでいる中, 糸島市コミュニティバスはこの共同研究を通じて, 利用者, 収益の大幅な増加を実現した.

  • 計算するということ/九州大学オープンキャンパス(伊都地区)

    九州大学  2015.8

    　More details

    Audience：Infants,　Schoolchildren,　Junior students,　High school students

    Type：Other

  • 計算について --有限と無限, 理論と実用--/九州大学オープンキャンパス(伊都地区)

    九州大学  2014.8

    　More details

    Audience：Infants,　Schoolchildren,　Junior students,　High school students

    Type：Other

  • 最適化の紹介 ~ 身近な問題を数学で解決しよう ~/九州大学オープンキャンパス(伊都地区)

    九州大学  2013.8

    　More details

    Audience：Infants,　Schoolchildren,　Junior students,　High school students

    Type：Other

▼display all

Acceptance of Foreign Researchers, etc.

  • Department of Optimization and Control, Institute of Mathematics, Vietnam Academy of Science and Technology

    Acceptance period： 2022.9   （Period）：2weeks to less than 1 month

    Nationality：Viet Nam

    Business entity：On-campus funds

  • Zuse Institute Berlin

    Acceptance period： 2013.11   （Period）：Less than 2 weeks

    Nationality：Germany

    Business entity：On-campus funds

Travel Abroad

  • 2013.3

    Staying countory name 1：Canada   Staying institution name 1：University of Waterloo

  • 2012.3

    Staying countory name 1：Canada   Staying institution name 1：University of Waterloo

  • 2011.5 - 2011.9

    Staying countory name 1：Canada   Staying institution name 1：University of Waterloo

  • 2007.6 - 2008.3

    Staying countory name 1：Netherlands   Staying institution name 1：Centrum voor Wiskunde en Informatica (Center for Mathematics and Computer Science)