| Project/Area Number |
05452122
|
|---|
| Research Category |
Grant-in-Aid for General Scientific Research (B)
|
| Allocation Type | Single-year Grants |
|---|
| Research Field |
Engineering fundamentals
|
|---|
| Research Institution | University of Tokyo |
|---|
Principal Investigator |
IMAI Hiroshi University of Tokyo, Graduate School of Science, Associate Professor, 大学院・理学系研究科, 助教授 (80183010)
|
|---|
| Co-Investigator(Kenkyū-buntansha) |
IMAI Keiko Chuo University, Faculty of Science and Engineering, Associate Professor, 理工学部, 助教授 (70203289)
|
|---|
| Project Period (FY) |
1993 – 1995
|
| Project Status |
Completed (Fiscal Year 1995)
|
| Budget Amount *help |
¥6,400,000 (Direct Cost: ¥6,400,000)
Fiscal Year 1995: ¥1,600,000 (Direct Cost: ¥1,600,000)
Fiscal Year 1994: ¥1,600,000 (Direct Cost: ¥1,600,000)
Fiscal Year 1993: ¥3,200,000 (Direct Cost: ¥3,200,000)
|
|---|
| Keywords | On-line algorithm / Dynamic shortest paths / Dynamic computational geometry / Continuum algorithm / Real-time algorithm / 動的問題 / 実時間問題 / オンライン / 競合度 / 動的アルゴリズム / A^*アルゴリズム / ボロノイ図 / 計算幾何 / 線形計画法 / 並列ネットワーク / 分散システム |
|---|
| Research Abstract |
The aim of this research is to develop efficient algorithms for discrete optimization problems under dynamic and on-line environments. Many practical problems have dynamic and on-line natures, and algorithms should be newly designed to handle dynamic and on-line factors.
First, we consider the dynamic shortest path problem where the distances of edges vary dynamically. This problem arises in real-time route navigation system where traffic jams makes the edge costs higher. We have developed A^*-based algorithms which make clever use of past solutions. Other techniques such as bidirectional search are also investigated. Also, to cope with future dynamic situations, a new algorithm to compute multiple candidates for route navigation in the given static environment is developed.
We formulate probelems of sharing information in distributed systems as an on-line model, and developed efficient on-line algorithms. The on-line nature is inherent in the distributed system, and we mainly consider page migration and replication probelms. To evaluate the on-line algorithms the so-called competitive ratio is used. Efficient algorithms in term of this ratio have been derived. Randomized techniques are demonstrated to be powerful for on-line problems.
Dynamic computational geometry is also investigated, especially the Voronoi diagram for dynamically moving points. The combinatorial complexity of dynamic Voronoi diagram is shown, together with its efficient construction algorithm. This is further applied to geometric clustering problem which have both discrete and continuous aspects. Randomized algorithms are developed by making use of these two aspects.
We have thus clarified fundamental structures of dynamic and on-line problems, and developed new paradigms to solve this new type of problems.
|
