• Journal of Korean Society of Industrial and Systems Engineering
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• v.19 no.39
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• pp.193-204
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• 1996

본 연구는 FMC(Flexible Manufacturing Cell)에 있어 상호 간섭이 없는 부품의 흐름을 제어하기 위한 교착제거방법(Deadlock Avoidance Method)에 대한 제안으로서, 이 방법이 주요한 장점은 첫째, FMC의 환경을 쉽게 적용시킬 수 있고 둘째, 공정상의 부품에 대한 dispatching 모듈이 협력하도록 설계되어 있다는 것이다. 교착제거방법은 두 개의 모듈로 구성되어 있는데 이는 순환발견알고리즘(A Cycle Detection Algorithm)과 원료주문 정책으로서, 특이할 만한 사항은 순환발견알고리즘을 채용하더라도 원료주문정책이 잘못될 수 있기 때문에 교착제거방법에 있어서 원료주문정책은 매우 중요하다는 것이다. 이를 위하여 교착전의 N-step 교착을 제거하고, 발견할 수 있는 교착제거방법과 N-step의 사전주무정책을 제시하였다.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.24 no.7B
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• pp.1313-1321
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• 1999

The two-phase locking protocol(2PL) is the most widely-used concurrency control mechanism for guaranteeing logical consistency of data in a database environment where a number of transactions perform concurrently. The problem inherent in the 2PL protocol is a deadlock, where a set of transactions holding some locks indefinitely wait an additional lock that is already held by other transactions in the set. The deadlock detector is a DBMS sub-component that examines periodically whether a system is in a deadlock state based on lock waiting information of transactions. The deadlock detector and transactions execute concurrently in a DBMS and read and/or write the lock waiting information simultaneously. Since the lock waiting information is a shared one, we need an efficient method guaranteeing its physical consistency by using mutual exclusion. The efficiency of the mutual exclusion method is crucial especially in a main memory DBMS with high performance since it seriously affects the performance of an entire system. In this paper, we propose a new method that effectively guarantees physical consistency of lock waiting information. Two primary goals of our method are to minimize the processing overhead and to maximize system concurrency.

• Journal of the Korea Society for Simulation
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• v.18 no.1
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• pp.9-16
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• 2009

Since a deadlock is a condition in which the excessive demand for the resources being used by others causes activities to stop, it is very important to detect and prevent a deadlock. About the deadlock detection analysis methods are may divide like as Siphon, DAPN and transitive matrix, but it's very difficult to evaluate the performance. Since DES (Discrete Event Systems) is NP-hard, and these detection and avoidance methods used various factors in each technique, it's made difficult to compare with each other's. In this paper, we are benchmarked these deadlock detection analyze methods based on the complexity, the detection time and the understanding after approached to one example.

• The Journal of Korean Association of Computer Education
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• v.13 no.6
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• pp.9-21
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• 2010

Concurrent processes come into conflict with each other when they are competing for the use of the same resources. In the case of competing processes three control problems must be faced: mutual exclusion, deadlock, and starvation. The concurrency is a subject rather difficult to understand. In addition, because concurrent programs included in most of OS texts are described by pseudocode and are not being able to execute directly, almost learners are difficult to understand behaviour of concurrent programs. The purpose of this study is to propose instruction method for mutual exclusion using SDL and MSC base on graphic. In order to verify the effectiveness of the proposed materials, we compare with materials based on pseudocode. The results indicated that the proposed materials is more effective than materials based on pseudocode in teaching-learning for mutual exclusion mechanisms.

• Journal of KIISE:Computer Systems and Theory
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• v.27 no.3
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• pp.255-263
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• 2000

A multistage interconnection network is a suitable class of interconnection architecture for constructing large-scale multicomputers. Broadcast and multicast communication are fundamental in supporting collective communication operations such as reduction and barrier synchronization. In this paper, we propose a new multicast technique in wormhole-switched bidirectional multistage banyan networks for constructing large-scale multicomputers. To efficiently support broadcast and multicast with simple additional hardware without deadlock, we propose a two-phase multicast algorithm which takes only two transmissions to perform a broadcast and a multicast to an arbitrary number of desired destinations. We encode a header as a cube and adopt the most upper input link first scheme with periodic priority rotation as arbitration mechanism on contented output links. We coalesce the desired destination addresses into multiple number of cubes. And then, we evaluate the performance of the proposed algorithm by simulation. The proposed two-phase multicast algorithm makes a significant improvement in terms of latency. It is noticeable that the two-phase algorithm keeps broadcast latency as efficient as the multicast latency of fanout 2^m where m is the minimum integer satisfying $2^m{\geq} {\sqrt{N}}$ ( N is a network size).

• Proceedings of the KIEE Conference
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• 2004.04a
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• pp.262-265
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• 2004

프로토콜 명세의 검정과 적합성 시험은 프로토콜 개발 과정에서 가장 중요한 부분으로, 명세에 규정되어진 시스템 기능의 정확성을 향상시키는데 사용되는 상호 보완 기술이다. 본 논문에서는 유한상태 레이블 천이시스템(LTS:Labeled Transition System)으로 명세화된 철도 신호제어용 프로토콜 Type 1 모델의 안전성 및 필연성 특성을 모형검사 기법에 의해 검정하였고, 실제적으로 교착상태의 유무나 초기 상태에서 임의의 상태로 도달 가능한지의 검사를 실험적으로 증명하였다. 구현되어진 형식 검정기는 Modal mu-calculus를 사용하며 Modal 논리로 표현된 특성이 명세에 대해 올바른지 아닌지를 검정할 수 있다. 또한 검정되어진 프로토콜 명세로부터 HO(Unique Input Output) 방법fl 의한 적합성 시험 계열 생성 방법을 제시하였다.

• Proceedings of the Korean Information Science Society Conference
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• 1998.10b
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• pp.472-474
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• 1998

병렬 객체를 이용한 소프트웨어의 개발시, 병렬성에서 기인한 경쟁 조건의 만족 여부나 교착 상태, 기아 상태 등의 오류를 모델의 검증을 통하여 개발의 초기 단계에 발겨하고 수정하는 것은 개발의 효율성을 높일 수 있다. 이러한 병력 객체모델의 검증을 위해서는 객체간의 상호 메시지 교환과 동적 행위를 기술할 수 있는 모델링 언어가 필요하며, 검증하고자 하는 속성을 기술하기 위한 방법이 요구된다. 본 연구에서는 시스템의 모델링을 위해 SPIN에서 사용되는 PROMELA를 쓰레드 기반의 객체 모델링 언어인 SPIN++로 확장하고, 속성의 기술을 위해 확장된 선형 시제 논리를 제안하였으며, 유한 상태에서는 모델 검사(model checking) 도구인 SPIN을 이용하여 검증하는 방법을 제시하고자 한다. 이러한 연구를 통하여 병렬 객체 모델의 정형적인 검증을 수행할 수 있으며, 시스템 개발의 효율성을 높이는 데 도움을 줄 수 있다.

• Journal of Industrial Technology
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• v.18
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• pp.355-362
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• 1998

The deadlock detector is a DBMS sub-component that examines periodically whether system is in a deadlock state based on lock waiting information of transactions. The deadlock detector and transactions execute concurrently in a DBMS and read and/or write the lock waiting information simultaneously. Since the lock waiting information is a shared one, we need an efficient method guaranteeing its physical consistency by using mutual exclusion. In this paper, we propose a new method that effectively guarantees physical consistency of lock waiting information. Two primary goals of our method is to minimize the processing overhead and to maximize system concurrency.

• Proceedings of the Korean Information Science Society Conference
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• 1999.10a
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• pp.376-378
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• 1999

공간 데이터 수집과정을 통해 제작된 수치지도는 타일 기반의 교환 포맷으로 구성되어 있다. 이러한 타일 기반의 수치지도를 이용해서 공간 데이터베이스를 구축하기 위해 먼저 타일로 분리되어 있는 수치지도를 Seamless 수치지도로 재작성해야 하며 이를 위해 타일 합병 작업이 필요하다. 타일 합병 작업을 다수의 작업자가 동시에 수행할 경우, 작업의 선후 관계에 따라 작업을 잃어 버리거나 (작업손실(Lost-Work)) 또는 동일한 엔티티들에 대해 교차 잠금이 요청되어 교착상태(DeadLock)가 발생하는 등의 문제점들이 발생한다. 이러한 문제점들을 해결하기 위해 이 논문에서는 작업자 상호간의 메시지 교환을 통한 동시 합병 작업 알고리즘을 제시하고 그에 따른 수치지도 합병 처리기를 설계 및 구현한다.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.25 no.4B
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• pp.646-680
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• 2000

In this paper, we discuss the design and implementation of a concurrency control manager for a main memory DBMS(MMDBMS). Since an MMDBMS, unlike a disk-based DBMS, performs all of data update or retrieval operations by accessing main memory only, the portion of the cost for concurrency control in the total cost for a data update or retrieval is fairly high. Thus, the development of an efficient concurrency control manager highly accelerates the performance of the entire system. Our concurrency control manager employs the 2-phase locking protocol, and has the following characteristics. First, it adapts the partition, an allocation unit of main memory, as a locking granule, and thus, effectively adjusts the trade-off between the system concurrency and locking cost through the analysis of applications. Second, it enjoys low locking costs by maintaining the lock information directly in the partition itself. Third, it provides the latch as a mechanism for physical consistency of system data. Our latch supports both of the shared and exclusive modes, and maximizes the CPU utilization by combining the Bakery algorithm and Unix semaphore facility. Fourth, for solving the deadlock problem, it periodically examines whether a system is in a deadlock state using lock waiting information. In addition, we discuss various issues arising in development such as mutual exclusion of a transaction table, mutual exclusion of indexes and system catalogs, and realtime application supports.