有村 博紀(アリムラ ヒロキ) |
情報科学研究院 情報理工学部門 知識ソフトウェア科学分野 |
教授 |
1990年九州大学大学院修士課程修了.同年,九州工業大学助手.その後,九州工業大学講師および助教授,九州大学大学院助教授および准教授などを経て,2004年から北海道大学情報科学研究科教授,現在に至る.博士(理学).1999~2002年 JST PREST「情報と知」(領域総括:安西祐一郎)研究員.2007~2011年度 文科省グローバルCOEプログラム「知の創出を支える次世代IT基盤拠点」拠点リーダー.2013〜2014年度 北海道大学知識メディアラボラトリー長. 2016〜2017年度 北海道大学ビッグデータ・サイバーセキュリティ グローバルステーション (GSB) 拠点長. 2015年度および2018〜2021年度 北海道大学共同プロジェクト拠点「知識メディアラボラトリー」リーダー. 2020〜2025年度JST PREST/さきがけ「信頼されるAIの基盤技術」研究総括.
現在,人工知能と, データマイニング,機械学習, 情報検索,アルゴリズムとデータ構造等の研究に従事.電子情報通信学会,情報処理学会,日本データベース学会, 人工知能学会会員, ACM, IEEE.
Given two feasible solutions A and B, a reconfiguration problem asks whether there exists a reconfiguration sequence (A0=A, A1,...,Aℓ=B) such that (i) A0,...,Aℓ are feasible solutions and (ii) we can obtain Ai from Ai-1 under the prescribed rule (the reconfiguration rule) for each i ∈ {1,...,ℓ}. In this paper, we address the reconfiguration problem for induced trees, where an induced tree is a connected and acyclic induced subgraph of an input graph. We consider the following two rules as the prescribed rules: Token Jumping: removing u from an induced tree and adding v to the tree, and Token Sliding: removing u from an induced tree and adding v adjacent to u to the tree, where u and v are vertices of an input graph. As the main results, we show that (I) the reconfiguration problemis PSPACE-complete even if the input graph is of bounded maximum degree, (II) the reconfiguration problem is W[1]-hard when parameterized by both the size of induced trees and the length of the reconfiguration sequence, and (III) there exists an FPT algorithm when the problem is parameterized by both the size of induced trees and the maximum degree of an input graph under Token Jumping and Token Sliding.
In this study, we address a problem pertaining to the induced matching enumeration. An edge set M is an induced matching of a graph G=(V,E). The enumeration of matchings has been widely studied in literature; however, there few studies on induced matching. A straightforward algorithm takes O(Δ2) time for each solution that is coming from the time to generate a subproblem, where Δ is the maximum degree in an input graph. To generate a subproblem, an algorithm picks up an edge e and generates two graphs, the one is obtained by removing e from G, the other is obtained by removing e, adjacent edge to e, and edges adjacent to adjacent edge of e. Since this operation needs O(Δ2) time, a straightforward algorithm enumerates all induced matchings in O(Δ2) time per solution. We investigated local structures that enable us to generate subproblems within a short time and proved that the time complexity will be O(1) if the input graph is C4-free. A graph is C4-free if and only if none of its subgraphs have a cycle of length four.