• Proceedings of the KIEE Conference
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• 1992.07a
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• pp.365-368
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• 1992

This paper presents an approach to the design of real time task scheduling for a line controller of continuous manufacturing process automation. The line controller has multiprocessor-based architecture with shared memory and is operated by firmware. This firmware contains menu-driven software supporting real-time database management and fuction-block control language. The multitasking line control processor performs the following three functions: 1) interprets the function block control language by virtue of shared memory in the database; 2) invokes an interupt service routine as required by external hardware; 3) detects errors and notifies the user. We propose real time task scheduling method.

• Journal of KIISE:Computing Practices and Letters
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• v.11 no.1
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• pp.62-68
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• 2005

This paper presents a scheme to enhance fixed priority scheduling algorithms on multiprocessors. This scheme gives the highest priority to jobs with zero laxity and schedules them Prior to other jobs. A fixed priority algorithm employing this scheme strictly dominates the original one; it can schedule all task sets schedulable by the fixed priority algorithm and some task sets not schedulable by the fixed priority algorithm. Simulation results show that the proposed scheme improves fixed priority algorithms in terms of the number of schedulable task sets and schedulable utilization bound.

• Journal of the Korea Society of Computer and Information
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• v.4 no.4
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• pp.40-46
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• 1999

The task scheduling has an effect on system execution time in a precedence constrained task graph onto the multiprocessor system. This problem is known to be NP-hard. many people made an effort to obtain near optimal schedule. We compared modified critical path schedule with many other methods(CP, MH, DL Swapping) For testing this subject, we created randomly a directed acyclic task graph with many root nodes and terminal nodes simulation result convinced for us that the modified critical path algorithm is superior to the other scheduling algorithm.

• Journal of Digital Contents Society
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• v.8 no.3
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• pp.279-288
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• 2007

Recently, Baruah et. al. proposed an optimal Pfair scheduling algorithm in the real-time multiprocessor system environments, and several variants of it were presented. All these algorithms assume the fixed unit quantum size. However, under Pfair based scheduling algorithms that are global scheduling technique, quantum size has direct influence on the scheduling overheads such as task switching and cache reload. We proposed a method for deciding the optimal quantum size[2] and an improved method for the task set whose utilization e is less than or equal to $e\;{\leq}\;p/3+1$[3]. However, these methods use repetitive computation of the task's utilization to determine the optimal quantum size. In this paper, we propose a more efficient method that can determine the optimal quantum size in constant time.

• Journal of KIISE
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• v.43 no.3
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• pp.296-303
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• 2016

Mobile real-time systems with limited system resources and a limited power source need to fully utilize the system resources when the workload is heavy and reduce energy consumption when the workload is light. EDZL (Earliest Deadline until Zero Laxity), a multiprocessor real-time scheduling algorithm, can provide high system utilization, but little work has been done aimed at reducing its energy consumption. This paper tackles the problem of DVFS (Dynamic Voltage/Frequency Scaling) in EDZL scheduling. It proposes a technique to compute a uniform speed on full-chip DVFS platforms and individual speeds of tasks on per-core DVFS platforms. This technique, which is based on the EDZL schedulability test, is a simple but effective one for determining the speeds of tasks offline. We also show through simulation that the proposed technique is useful in reducing energy consumption.

• Journal of Information Processing Systems
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• v.9 no.2
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• pp.301-314
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• 2013

In a parallel processing system, Multi-stage Interconnection Networks (MINs) play a vital role in making the network reliable and cost effective. The MIN is an important piece of architecture for a multiprocessor system, and it has a good impact in the field of communication. Optical Multi-stage Interconnection Networks (OMINs) are the advanced version of MINs. The main problem with OMINs is crosstalk. This paper, presents the (1) Destination Based Modified Omega Network (DBMON) and the (2) Destination Based Scheduling Algorithm (DBSA). DBSA does the scheduling for a source and their corresponding destination address for messages transmission and these scheduled addresses are passed through DBMON. Furthermore, the performance of DBMON is compared with the Crosstalk-Free Modified Omega Network (CFMON). CFMON also minimizes the crosstalk in a minimum number of passes. Results show that DBMON is better than CFMON in terms of the average number of passes and execution time. DBSA can transmit all the messages in only two passes from any source to any destination, through DBMON and without crosstalk. This network is the modified form of the original omega network. Crosstalk minimization is the main objective of the proposed algorithm and proposed network.

• Proceedings of the Korean Information Science Society Conference
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• 1998.10a
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• pp.113-115
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• 1998

다중프로세서 환경에서 타스크들을 할당해주는 중앙 프로세서를 두고 Laxity를 기반으로 긴급타스크를 선택하여 스케쥴링을 수행한다. 중앙프로세서는 프로세서들의 슬랙시간과 각 프로세서의 Local큐에 대기하고 있는 비주기적 타스크의 총 수행시간 등의 상태정보를 수집 분석하여, 타스크의 실행시간에 가장 적합한 프로세서를 선xor하여 할당한다. 또한 타스크 특성에 따라 주기적 타스크와 비주기적 타스크로 나누고 주지적 타스크는 마감시간을 지키는 범위 내에서 최대한 수행시간을 연기 시켰다. 시뮬레이션 결과 Overload(마감시간을 지키지 못하는 타스크)수의 감소와 빠른 응답시간을 제공함을 알 수 있었다.

• Proceedings of the Korea Contents Association Conference
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• 2015.05a
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• pp.57-58
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• 2015

실시간성이란 연산의 정확성과 연산 수행시간이 예측 가능한 시간 내에 완료되는 것을 말한다. 범용 운영체제인 리눅스에서는 CFS(Complete Fair Scheduling)을 사용하여 높은 우선순위 태스크에 대한 빠른 응답성을 보장할 수 없기 때문에 실시간성을 제공하지 못한다. 이를 해결하기 위해 RTiK-Linux(Real-Time implanted Kernel for Linux)가 개발되어 리눅스 환경에서 실시간성을 제공하였지만 개발 당시 싱글프로세서 환경만을 고려하여 최근 사용되는 멀티프로세서 환경에서는 실시간성 제공에 어려움이 있다. 본 논문에서는 멀티프로세서 리눅스 상에서 발생하는 RTiK-Linux의 문제점에 대해 설명하고 이에 대한 해결방안을 기술하여 멀티프로세서 리눅스 상에서 실시간성을 제공하기 위한 방안을 연구하였다.

• Journal of KIISE:Computer Systems and Theory
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• v.27 no.3
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• pp.337-344
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• 2000

In this paper, we define a Process Algebra ACSMR(Algebra of Communicating Shared Multiple Resources) for system specification and verification using multiple resources. ACSMR extends a concept of multiple resources in ACSR that is a branch of formal methods based on process algebra. We'll show that two specification and verification examples. One is the specification of system behavior in multiprocessor using EDF(Earliest-Deadline-First) which is a scheduling algorithm of a real-time system. The other is the specification of describing timing analysis and resources restriction in a super scalar processor using multiple ports registers.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.5 no.2
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• pp.137-140
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• 2004

다중 프로세서 시스템이 개발됨에 따라, 새로운 일정계획문제, 하나의 작업이 하나이상의 기계에 의해 동시에 처리되어야 하는 문제가 대두되었다. 이 연구에서는 선행관계를 가진 이러한 다중 프로세서 일정계획문제에 대해 다루어 보았다. 이 연구의 목적은 makespan을 최소화하는 일정계획을 찾는 것이다. 일반적으로 Branch and Bound 기법을 이용하여 선행관계를 가진 다중 프로세서 일정계획문제의 최적해를 찾았는데, 해의 탐색시간이 너무 오래 걸린다는 단점이 있었다. 본 연구에서는 짧은 시간 내에 최적해와 가까운 근사해를 simulated annealing(SA)방법을 이용하여 구해보았다. SA의 성능을 측정하기 위하여, SA의 CPU 처리시간과 구한 근사해를 40개의 예제문제를 통하여 Kramer의 방법의 CPU 처리시간과 최적해와 비교해 보았다.