| Project/Area Number |
17500008
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Fundamental theory of informatics
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| Research Institution | Kyoto University |
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Principal Investigator |
NAGAMOCHI Hiroshi Kyoto University, Graduate School of Informatics, Professor (70202231)
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| Co-Investigator(Kenkyū-buntansha) |
HASUNUMA Toru The University of Thkushima, Faculty of integrated Arts and Sciences, Associate Professor (30313406)
KAMIDOI Yoko Hiroshima City University, Graduate School of Information Sciences, Lecturer (80264935)
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| Project Period (FY) |
2005 – 2007
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| Project Status |
Completed (Fiscal Year 2007)
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| Budget Amount *help |
¥3,700,000 (Direct Cost: ¥3,400,000、Indirect Cost: ¥300,000)
Fiscal Year 2007: ¥1,300,000 (Direct Cost: ¥1,000,000、Indirect Cost: ¥300,000)
Fiscal Year 2006: ¥1,000,000 (Direct Cost: ¥1,000,000)
Fiscal Year 2005: ¥1,400,000 (Direct Cost: ¥1,400,000)
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| Keywords | Algorithm / Applied Mathematics / Mathematical Engineering / Fundamentals of Informatics / Graph Theory / Network / Approximation Algorithm / Connectivity / ネットワーク設計 / 連結度 / 最小カット / グラフ分割 / グラフの直径 / グラフ増大問題 |
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| Research Abstract |
Many problems in communication networks can be modeled as graph problems if we fix several factors describing the problems. In this work, we first modeled problems in communication networks as graph (network) problems by selecting the essential conditions from a lot of complex conditions inquired for the communication problems and then analyzed properties on the connectivity by observing the structures of the problems. Furthermore, we designed approximation algorithms using the mathematical structures characterizing the properties that we elucidated. From our work, many results related to properties on the connectivity of graphs and networks were obtained. In what follows, we classify the results roughly into the multicast tree problem, the queue layout problem, and the minimum k-way cut problem, and then state each summary.
1. The multicast tree problem: In this work, we proposed a (3/2+(4/3) ρ)-approximation algorithm for this problem, where ρ is the best achievable approximation ratio for the Steiner tree problem. Compared with the best approximation ratio (2+ρ) in the previously known approximation algorithms, the more ρ is improved, the more the approximation ratio of our algorithm is improved. 2. The queue layout problem. In this work, we studied on the class of iterated line digraphs which contains several digraph classes that were studied individually so far, and present upper and lower bounds on the queuenumber of iterated line digraphs. 3. The minimum k-way cut problem. In this work, we defined a new problem, and designed a 2-approximation algorithm for the minimum k-way cut problem based on a method for the optimum solution for the new problem. Using this result, we improved the time complexity of a 2-approximation algorithm from O(k(mn+n^2logn)) to O(mn+n^2logn).
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