• The Transactions of the Korea Information Processing Society
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• v.7 no.7
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• pp.2060-2071
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• 2000

Scheduling parallel tasks, represented as a Directed Acyclic Graph (DAG) or task graph, on a multiprocessor system has been an important research area in the past decades. List scheduling algorithms assign priorities to a node or an edge in an input DAG, and then generate a schedule according to the assigned priorities. This appear proposes a list scheduling algorithms with effective method of priority assignments. The paper also analyzes the worst case performance and optimality condition for the proposed algorithm. The performance comparison study shows that the proposed algorithms outperforms existing scheduling algorithms especially for input DAGs with high communication overheads. The performance improvement over existing algorithms becomes larger as the input DAG becomes more dense and the level of parallelism in the DAG is increased.

• Proceedings of the KIEE Conference
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• 1987.07a
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• pp.226-229
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• 1987

This paper was aimed to, using a new data structure, develop a set of algorithms to execute the output function of Digital System. These functions were represented as directed, acyclic graphs. by applying many restrictions on vertices on graph, the efficient manipulation of boolean function was accomplished. The results were as follows; 1. A canonical representation of a boolean function was created by the reduction algorithm. 2. The operation of two functions was accomplished using t he apply algorithm, according to the binary operator. 3. The arguments having 1 as the value nf function were enumerated using the satisfy algorithm. 4. Composing TTL 74181 4-bit ALU and 74182 look-ahead carry generator, the ALU having 4-bit and 16-bit as word size was implemented.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.5 no.7
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• pp.1252-1273
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• 2011

In Web Service Composition (WSC) area, services selection aims at selecting an appropriate candidate from a set of functionally-equivalent services to execute the function of each task in an abstract WSC according to their different QoS values. In despite of many related works, few of previous studies consider transactional constraints in QoS-aware WSC, which guarantee reliable execution of Composite Web Service (CWS) that is composed by a number of unpredictable web services. In this paper, we propose a novel global selection-optimal approach in WSC by considering both transactional constraints and end-to-end QoS constraints. With this approach, we firstly identify building rules and the reduction method to build layer-based Directed Acyclic Graph (DAG) model which can model transactional relationships among candidate services. As such, the problem of solving global optimal QoS utility with transactional constraints in WSC can be regarded as a problem of solving single-source shortest path in DAG. After that, we present Graph-building algorithms and an optimal selection algorithm to explain the specific execution procedures. Finally, comprehensive experiments are conducted based on a real-world web service QoS dataset. The experimental results show that our approach has better performance over other competing selection approaches on success ratio and efficiency.

• Proceedings of the IEEK Conference
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• 2000.07a
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• pp.289-293
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• 2000

We propose two new algorithms for parallelism-independent scheduling. The machine code generated from the compiler using these algorithms in its scheduling phase is parallelism-independent code, executable in minimum time regardless of the number of the processors in the parallel computer. Our new algorithms have the following phases: finding the minimum number of processors on which the program can be executed in minimal time, scheduling by an heuristic algorithm for this predefined number of processors, and serialization of the parallel schedule according to the earliest start time of the tasks. At run time tasks are taken from the serialized schedule and assigned to the processor which allows the earliest start time of the task. The order of the tasks decided at compile time is not changed at run time regardless of the number of the available processors which means there is no out-of-order issue and execution. The scheduling is done predominantly at compile time and dynamic scheduling is minimized and diminished to allocation of the tasks to the processors. We evaluate the proposed algorithms by comparing them in terms of schedule length to the CP/MISF algorithm. For performance evaluation we use both randomly generated DAGs (directed acyclic graphs) and DACs representing real applications. From practical point of view, the algorithms we propose can be successfully used for scheduling programs for in-order superscalar processors and shared memory multiprocessor systems. Superscalar processors with any number of functional units can execute the parallelism-independent code in minimum time without necessity for dynamic scheduling and out-of-order issue hardware. This means that the use of our algorithms will lead to reducing the complexity of the hardware of the processors and the run-time overhead related to the dynamic scheduling.

• Journal of the Korean Institute of Telematics and Electronics T
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• v.36T no.4
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• pp.71-81
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• 1999

We propose a new CPLD(Complexity Programmable Logic Device) technology mapping algorithm improving run-time under time constraint. In our technology mapping algorithm, a given logic equation is constructed as the DAG(Directed Acyclic Graph) type, then the DAG is reconstructed by replicating the node that outdegree is more than or equal to 2. As a result, it makes delay time and the number of CLBs, run-time to be minimized. Also, after the number of multi-level is defined and cost of each nodes is calculated, the graph is partitioned in order to fit to k that is the number of OR term within CLB. The partitioned nodes are merged through collapsing and bin packing is performed in order to fit to the number of OR term within CLB(Configurable Logic Block). In the results of experiments to MCNC circuits for logic synthesis benchmark, we can shows that proposed technology mapping algorithm reduces run-time and the number of CLBs much more than the TEMPLA.

• Journal of KIISE:Databases
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• v.27 no.2
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• pp.185-198
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• 2000

Recently the technological advance in the hardware dealing with multimedia data as well as the explosive increase of the volume of multimedia data bring about new interest in the use of multimedia presentations in many application domains. To use multimedia presentations efficiently, the integration of multimedia presentations into DBMS is necessary. This paper presents a multimedia presentatation query language based on contents and query processing techniques. Presently, multimedia presentation authoring tools denote a multimedia presentation using a presentation graph which is a DAG. A Node in the graph is a same type of media stream and edges denote a play-out order and a synchronization way among nodes. The contents of presentations graphs are the information of each stream, the sequential order of the information inside each stream and the play-out order among the streams. GCalculus/S is a calculus-based query language and can deal with the contents of a presentation graph and physical characteristics of multimedia data. It expresses the sequential order of information inside each stream and the play-out order of streams of a presentation graph using temporal operators Next, Connected and Until. O-Algebra, which is object algebra, is extended to process GCalculus/S queries.

• International Journal of Fuzzy Logic and Intelligent Systems
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• v.11 no.3
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• pp.135-142
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• 2011

Unlike using the sequence-based representation for a chromosome in previous genetic algorithms for Bayesian structure learning, we proposed a matrix representation-based genetic algorithm. Since a good chromosome representation helps us to develop efficient genetic operators that maintain a functional link between parents and their offspring, we represent a chromosome as a matrix that is a general and intuitive data structure for a directed acyclic graph(DAG), Bayesian network structure. This matrix-based genetic algorithm enables us to develop genetic operators more efficient for structuring Bayesian network: a probability matrix and a transpose-based mutation operator to inherit a structure with the correct edge direction and enhance the diversity of the offspring. To show the outstanding performance of the proposed method, we analyzed the performance between two well-known genetic algorithms and the proposed method using two Bayesian network scoring measures.

• Proceedings of the Korea Information Processing Society Conference
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• 2003.11a
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• pp.189-192
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• 2003

이 논문에서는 그리드환경에서 Remote Procedure Call(RPC) 프로그래밍 인터페이스를 위한 메커니즘인 GridRPC 의 성능향상을 위해 DAG 기반의 Co-scheduling API 를 제안한다. 네트워크 상의 통신횟수를 줄임으로써 GridRPC call 의 최적화를 도모하기 위한 프로그래밍 인터페이스와 이를 가능하게 하는 서버구조를 제안한다. DAG 기반의 co-scheduling 은 서버-클라이언트간의 연산에 사용되는 입력값과 출력값들의 흐름을 분석하여 사용자로 하여금 DAG(Directed Acyclic Graph)로 GridRPC call 들을 구성하고 이를 기반으로 GridRPC call 들을 최적화하는 방법이다. 또한, GridRPC가 Client Interface 이기 때문에 생기는 문제점인 서버간의 지원의 문제점을 SOAP 서버의 Wrapping 을 통해 해결한다.

• Annual Conference on Human and Language Technology
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• 1994.11a
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• pp.207-210
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• 1994

한글 전자사전은 많은 양의 데이타를 저장할 수 있어야 하며, 빠른 검색 속도를 제공해야 한다. 기존의 트라이는 공통접두사만을 압축하기 때문에 사전의 크기가 방대하다는 단점이 있다. 본 논문에서는 DAWG(Directed Acyclic Word Graph)를 이용하여 공통접미사까지 압축하였고, 검색과 기억장소의 효율을 위하여, 링크드리스트 구조의 DAWG를 유형별 배열 구조로 바꾸었다. 전국의 각 학교 이름들을 대상으로 실험한 결과, 본 논문에서 제안한 DAWG를 이용한 배열 구조의 사전은 트라이와 비교하여 볼 때, 검색 연산의 성능은 동일하게 유지하면서 기억 장소의 효율과 압축율에서 효과적이었다. 또한, 트라이보다 주기억장치와 보조기억장치와의 블록 입출력횟수를 줄임으로써 전체 검색 시간을 낮출 수 있었다.

• Proceedings of the Korean Statistical Society Conference
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• 2003.05a
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• pp.157-162
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• 2003

Estimates from an EM algorithm are somewhat sensitive to the initial values for the estimates, and it is more likely when the model becomes larger and more complicated. In this article, we examined how the estimates fluctuate during an EM procedure for a recursive model of categorical variables. It is found that the fluctuation takes place mostly during the first half of the procedure and that it can be subdued by applying the Bayesian method of estimation. Both simulation data and real data are used for illustration.