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Featured researches published by Atsuko Ikegami.


advanced information networking and applications | 2012

Optimal Data Allocation for Keeping Fairness of Online Game

Masaki Kohana; Shusuke Okamoto; Atsuko Ikegami

In our previous work, we proposed a load distribution technique and dynamic data reallocation method for web-based MORPG system. This approach could reduce the average server latency for game players. However, each latency widely varied, which leads unfair situation for game players. In this paper, we deal with data allocation with taking into account the fairness as a combinational optimization problem. We develop an optimization model whose objective function is to minimize the difference among latency value. We exactly solve this problem and compare the results with our previous data allocation method.


International Journal of Grid and Utility Computing | 2014

Optimal data allocation and fairness for online games

Masaki Kohana; Shusuke Okamoto; Atsuko Ikegami

In our previous work, we proposed a load distribution technique and a dynamic data reallocation method for web-based Multiplayer Online Role-Playing Game MORPG systems. Our proposed approach reduced the average server latency for game players. However, latency values varied widely resulting in some game players gaining an advantage over others. In this paper, we deal with data allocation and consider latency fairness in the form of a combinational optimisation problem. We develop an optimisation model in which the objective function minimises the differences in latency values and we solve instances from this model using an exact algorithm. Our model improved latency fairness and more stable server loads than the previous data reallocation method. Furthermore, it provides more stable gameplay using ten web servers instead of five.


Systems and Computers in Japan | 1993

A parallel branch-and-bound algorithm for integer linear programming and its implementation on a distributed multiprocessor

Atsuko Ikegami; Katsuhiro Aoyagi; Hajime Iizuka

This paper describes a parallel branch-and-bound algorithm for general integer linear programming problems and its implementation on a distributed memory multiprocessor nCUBE2. With a branch-and-bound algorithm, the amount of computation on each search tree node varies, and in general, is large. This has led to development of an effective communication strategy for the algorithm presented herein. Its implementation and performance evaluation also are described. The results show that the more difficult the problem instances become in terms of time to solve on a sequential computer, the more efficient the algorithm presented here proves to be.


Mathematical Programming | 2003

A subproblem-centric model and approach to the nurse scheduling problem

Atsuko Ikegami; Akira Niwa


Journal of The Operations Research Society of Japan | 1995

The Vehicle Routing Problem with Time Constraints

Atsuko Ikegami; Akira Niwa


Archive | 2007

BOUNDS FOR STAFF SIZE IN HOME HELP STAFF SCHEDULING

Atsuko Ikegami; Aki Uno


Journal of The Operations Research Society of Japan | 1998

AN EFFICIENT APPROACH TO NURSE SCHEDULING : IMPLEMENTATION FOR A 2-SHIFT CASE

Atsuko Ikegami; Akira Niwa


Journal of The Operations Research Society of Japan | 2007

BOUNDS FOR STAFF SIZE IN HOME HELP STAFF SCHEDULING( the 50th Anniversary of the Operations Research Society of Japan)

Atsuko Ikegami; Aki Uno


IEICE Transactions on Information and Systems | 2013

A Meta-Heuristic Approach for Dynamic Data Allocation on a Multiple Web Server System

Masaki Kohana; Shusuke Okamoto; Atsuko Ikegami


Transactions of the Operations Research Society of Japan | 2008

FINDING THE MINIMUM COST PATH FOR A RAILWAY FARE CALCULATION : A CASE STUDY INVOLVING MORE THAN ONE RAILWAY COMPANY

Atsuko Ikegami; Shunji Morita; Takuma Yamaguchi; Jo Kikuchi; Toshihiro Nakayama; Motohiro Ohkura

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