• Information and Communications Magazine
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• v.28 no.9
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• pp.69-75
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• 2011

본고에서는 압축센싱(Compressed sensing) 기술의 개념과 동작원리를 소개하고 최근 제안된 Message Passing 기반의 복호암고리즘에 대하여 알아본다. Message Passing 기반의 복호알고리즘은 기존 최적화기반의 복호알고리즘보다 낮은 복잡도로 동작하면서도 뛰어난 성능을 갖는 것으로 알려져 있다. 또한, 신호처리 및 정보이론 분야에서 활발히 연구되고 있는 압축센싱 기술의 차세대 이동통신 시스템 응용의 가능성을 검토하고 최근 통신시스템을 위하여 제안된 압축센싱 기반의 알고리즘을 추가로 검토한다.

• The KIPS Transactions:PartA
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• v.15A no.2
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• pp.87-94
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• 2008

Message races should be detected for debugging effectively message-passing programs because they can cause non-deterministic executions of a program. Previous tools for detecting message races report that message races occur in every receive operation which is expected to receive any messages. However message races might not occur in the receive operation if each of messages is transmitted through a different logical communication channel so that their incorrect detection makes it a difficult task for programmers to debug programs. In this paper we suggest a tool, MPIRace-Check, which can exactly detect message races by checking the concurrency between send/receive operations, and by inspecting the logical communication channels of the messages. To detect message races, this tool uses the vector timestamp to check if send and receive operations are concurrent during an execution of a program and it also uses the message envelop to inspect if the logical communication channels of transmitted messages are the same. In our experiment, we show that our tool can exactly detect message races with efficiency using MPI_RTED and a benchmark program. By detecting message races exactly, therefore, our tool enables programmers to develop reliable parallel programs reducing the burden of debugging.

• Journal of KIISE:Computer Systems and Theory
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• v.33 no.8
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• pp.495-504
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• 2006

Detecting unaffected race conditions is important to debugging message-passing programs effectively, because such a message race can affect other races to occur or not. The previous technique to detect efficiently unaffected races detects racing messages by halting at the receive event of the first race to occur in each process. However this technique does not guarantee that all of the detected races are unaffected, because halting such processes does disconnect some chain of affects-relations among those races. In this paper, we present a novel technique that manages the state of the detected race by examining if every received message is affected until the execution terminates. Our technique therefore guarantees to detect efficiently the unaffected races, because it maintains affects-relations of the races all along the execution of program.

• Spatial Information Research
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• v.11 no.3
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• pp.213-226
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• 2003

With the increasing demand of processing massive geographic data, conventional GISs based on the single processor architecture appear to be problematic. Especially, performing complex GIS operations on the massive geographic data is very time consuming and even impossible. This is due to the processor speed development does not keep up with the data volume to be processed. In the field of GIS, this PC clustering is one of the emerging technology for handling massive geographic data effectively. In this study, a MPI(Message Passing Interface)-based parallel processing approach was conducted to implement the existing raster GIS operations that typically requires massive geographic data sets in order to improve the processing capabilities and performance. Specially for this research, four types of raster CIS operations that Tomlin(1990) has introduced for systematic analysis of raster GIS operation. A data decomposition method was designed and implemented for selected raster GIS operations.

• The KIPS Transactions:PartD
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• v.15D no.5
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• pp.659-668
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• 2008

Recently, the component model based on the Exogenous Connector has been proposed in which controls are separated from computation by managing the beginning and result of method calls in the connector. Although it could be loosely coupled between components, it has a problem that is a potential preponderance of element objects of the system by increasing the number of connectors and connection levels. In this paper we propose the Tree Component Model with the Hybrid Message Passing that combines direct and indirect message passing. In our model, components are wrapped by interfaces and controls are separated from computation by only using their interface references. There is a unique feature that the composition structure of components becomes the tree always. As a result of demonstration and comparison, it is found that the Tree Component Model is applicable practically and decreases objects to mediate message passing and build the system.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.22 no.1
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• pp.132-141
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• 1998

A parallel version of sheet forming analysis program was developed. This version is compatible with any parallel computers which support MPI that is one of the most recent and popular message passing libraries. For this purpose, SERI-SFA, a vector version which runs on Cray Y-MP C90, a sequential vector computer, was used as a source code. For the sake of the effectiveness of the work, the parallelization was focused on the selected part after checking the rank of CPU consumed from the exemplary calculation on Cray Y-MP C90. The subroutines associated with contact algorithm was selected as targe parts. For this work, MPI was used as a message passing library. For the performance verification, an oil pan and an S-rail forming simulation were carried out. The performance check was carried out by the kernel and total CPU time along with theoretical performance using Amdahl's Law. The results showed some performance improvement within the limit of the selective paralellization.

• Journal of the Korea Institute of Military Science and Technology
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• v.18 no.6
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• pp.762-770
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• 2015

Fault tolerance is a crucial design for a mission-critical computer such as engagement control computer that has to maintain its operation for long mission time. In recent years, software fault-tolerant design is becoming important in terms of cost-effectiveness and high-efficiency. In this paper, we propose MPCMCC which is a model-based software component to implement fault tolerance in mission-critical computers. MPCMCC is a fault tolerance design that synchronizes shared data between two computers by using the one-way message-passing scheme which is easy to use and more stable than the shared memory scheme. In addition, MPCMCC can be easily reused for future work by employing the model based development methodology. We verified the functions of the software component and analyzed its performance in the simulation environment by using two mission-critical computers. The results show that MPCMCC is a suitable software component for fault tolerance in mission-critical computers.

• Journal of Ocean Engineering and Technology
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• v.20 no.4 s.71
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• pp.76-82
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• 2006

The large-eddy simulation(LES) technique, based an a message passing interface method(MPI), was applied to investigate the turbulent flaw phenomena around a ship. The Smagorinski model was used in the present LES simulation to simulate the turbulent flaw around a ship. The SPMD(sidsngle program multiple data) technique was used for parallelization of the program using MPI. All computations were performed an a 24-node PC cluster parallel machine, composed of 2.6 GHz CPU, which had been installed in the Advanced Ship Engineering Research Center(ASERC). Numerical simulations were performed for the Wigley hull, and the Series 60 hull(CB=0.6) using 1/4-, 1/2-, 1- and 2-million grid systems and the computational results had been compared to the experimental ones.

• Journal of Satellite, Information and Communications
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• v.9 no.2
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• pp.63-68
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• 2014

This paper proposed a novel compressed sensing (CS) technique for an efficient video transmission of multi-copter. The proposed scheme is focused on reduction of the amount of data based on CS technology. First, we describe basic principle of Spectrum sensing. And then we compare AMP(Approximate Message Passing) with CoSaMP(Compressive Sampling Matched Pursuit) through mathematical analysis and simulation results. They are evaluated in terms of calculation time and complexity, then the promising algorithm is suggestd for multicopter operation. The result of experiment in this paper shows that AMP algorithm is more efficient than CoSaMP algorithm when it comes to calculation time and image error probability.

• Journal of KIISE:Computer Systems and Theory
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• v.34 no.7
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• pp.267-275
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• 2007

Message races should be detected for debugging message-passing parallel programs because they can cause non-deterministic executions. Specially, it is important to detect the first race in each process because the first race can cause the occurrence of the other races in the same process. The previous techniques for detecting the first races require more than two monitored runs of a program or analyze a trace file which size is proportional to the number of messages. In this paper we introduce an on-the-fly technique to detect the first race in each process without generating any trace file. In the experiment we test the accuracy of our technique with some benchmark programs and it shows that our technique detects the first race in each process in all benchmark programs.